محطة الفضاء الدولية

محطة الفضاء الدولية

محطة الفضاء الدولية في 23 مايو 2010 ، كما رأينا من STS-132
إحصائيات المحطة
معرف COSPAR	1998-067A
ساتكات لا.	25544
علامة إتصال	ألفا ، محطة
طاقم العمل	طاقم كامل: 7 أفراد حاليًا على متن: 7 ( Soyuz MS-18 ، SpaceX Crew-2 ) البعثة: 65 القائد: أكيهيكو هوشيد ( JAXA )
إطلاق	20 تشرين الثاني / نوفمبر 1998 ؛ قبل 22 عاما (1998-11-20)
منصة الإطلاق	بايكونور ، الموقع 1/5 و الموقع 81/23 كينيدي ، LC-39 و CCSFS ، SLC-41 (المستقبل)
كتلة	440725 كجم (971632 رطلاً) [1]
طول	73.0 م (239.4 قدمًا) [1]
عرض	109.0 م (357.5 قدمًا) [1]
حجم مضغوط	915.6 م 3 (32333 قدمًا مكعبًا) [1]
الضغط الجوي	101.3  كيلو باسكال (14.7  رطل / بوصة مربعة ؛ 1.0  ضغط جوي ) 79٪ نيتروجين ، 21٪ أكسجين
ارتفاع نقطة الحضيض	418 كم (259.7 ميل) AMSL [2]
الأوج الارتفاع	422 كم (262.2 ميل) AMSL [2]
الميل المداري	51.64 درجة [2]
السرعة المدارية	7.66 كم / ثانية [2] [ فشل التحقق ] (27600 كم / ساعة ، 17100 ميل في الساعة)
المداري	92.68 دقيقة [2] [ فشل التحقق ]
مدارات في اليوم	15.49 [2]
عصر المدار	21 مايو 2021 05:42:57 [2]
أيام في المدار	22 سنة و 8 أشهر و 29 يومًا (18 أغسطس 2021)
أيام شغلها	20 سنة و 9 أشهر و 16 يومًا (18 أغسطس 2021)
رقم المدارات	131،440 اعتبارًا من ديسمبر 2020 [3][update]
تسوس الحجاج	2 كم / شهر
الإحصائيات حتى 9 مارس 2011 (ما لم يذكر خلاف ذلك) المراجع: [1] [2] [4] [5] [6]
ترتيب
عناصر المحطة اعتبارًا من يوليو 2021 ( عرض مفجر )[update]

على محطة الفضاء الدولية ( ISS ) هي وحدات محطة الفضاء الدولية (سكن قمر صناعي ) في مدار منخفض حول الأرض . إنه مشروع تعاوني متعدد الجنسيات يضم خمس وكالات فضاء مشاركة: ناسا (الولايات المتحدة) ، روسكوزموس (روسيا) ، جاكسا (اليابان) ، إيسا (أوروبا) ، وكالة الفضاء الكندية (كندا). ^{[7] [8]} يتم تحديد ملكية واستخدام المحطة الفضائية بموجب المعاهدات والاتفاقيات الحكومية الدولية. ^[9] محطة بمثابة الجاذبية الصغرى و البيئة الفضائيةمختبر الأبحاث التي البحوث العلمية والتي أجريت في بيولوجيا الفضاء ، علم الفلك ، علم الأرصاد الجوية ، الفيزياء ، وغيرها من المجالات. ^{[10] [11] [12]} محطة الفضاء الدولية مناسبة لاختبار أنظمة المركبات الفضائية والمعدات اللازمة للبعثات المستقبلية طويلة الأمد إلى القمر والمريخ. ^[13]

في برنامج ISS تطورت من محطة الفضاء الحرية ، اقتراحا أمريكيا التي ولدت في عام 1984 لبناء محطة التي تدور حول الأرض مأهولة بشكل دائم، ^[14] ومعاصرة / السوفيتي الروسية مير 2 اقتراح من عام 1976 مع أهداف مماثلة. محطة الفضاء الدولية هي محطة الفضاء الدولية التاسعة التي يسكنها فرق، في أعقاب السوفياتي والروسي في وقت لاحق ساليوت ، ألمظ ، و مير المحطات والأمريكية سكاي لاب . إنه أكبر جسم اصطناعي في الفضاء وأكبر قمر صناعي في مدار أرضي منخفض ، ويمكن رؤيته بالعين المجردة بانتظام من سطح الأرض. ^{[15] [16]}فإنه يحافظ على مدار على ارتفاع متوسط من 400 كيلومتر (250 ميل) عن طريق المناورات reboost باستخدام محركات من زفيزدا وحدة الخدمة أو زيارة المركبة الفضائية. ^[17] تدور محطة الفضاء الدولية حول الأرض في حوالي 93 دقيقة ، لتكمل 15.5 دورة في اليوم. ^[18]

تنقسم المحطة إلى قسمين: الجزء المداري الروسي (ROS) تديره روسيا ، بينما يتم تشغيل الجزء المداري للولايات المتحدة (USOS) من قبل الولايات المتحدة بالإضافة إلى العديد من الدول الأخرى. أيدت شركة Roscosmos استمرار تشغيل ROS حتى عام 2024 ، ^[19] بعد أن اقترحت سابقًا استخدام عناصر من هذا الجزء لبناء محطة فضائية روسية جديدة تسمى OPSEK . ^[20] تم إطلاق أول مكون لمحطة الفضاء الدولية في عام 1998 ، ووصل أول مقيمين على المدى الطويل في 2 نوفمبر 2000 بعد إطلاقهم من بايكونور كوزمودروم في 31 أكتوبر 2000. ^[21]منذ ذلك الحين ، ظلت المحطة مشغولة بشكل مستمر لمدة 20 عامًا و 289 يومًا ، ^[22] وهو أطول وجود بشري مستمر في مدار أرضي منخفض ، بعد أن تجاوز الرقم القياسي السابق البالغ 9 سنوات و 357 يومًا الذي احتفظت به محطة مير الفضائية. تم تركيب أحدث وحدة مضغوطة رئيسية ، Nauka ، في عام 2021 ، بعد ما يزيد قليلاً عن عشر سنوات بعد الإضافة الرئيسية السابقة ، ليوناردو في عام 2011. يستمر تطوير وتجميع المحطة ، مع إضافة موطن تجريبي للفضاء القابل للنفخ في عام 2016 ، والعديد من الموائل الجديدة الرئيسية من المقرر إطلاق العناصر الروسية اعتبارًا من عام 2021. اعتبارًا من ديسمبر 2018 ^[update]، تم تمديد تصريح تشغيل المحطة حتى عام 2030 ، مع تأمين التمويل حتى عام 2025. ^[23]كانت هناك دعوات لخصخصة عمليات ISS بعد هذه النقطة لتحقيق مستقبل القمر و بعثات المريخ ، مع السابقة مدير ناسا جيم بريدنستين قائلا "نظرا قيود الميزانية الحالية لدينا، إذا أردنا أن نذهب إلى القمر ونحن نريد أن نذهب إلى كوكب المريخ، ونحن بحاجة إلى تسويق مدار أرضي منخفض والانتقال إلى الخطوة التالية ". ^[24]

تتكون محطة الفضاء الدولية من وحدات سكنية مضغوطة ، دعامات هيكلية ، صفائف شمسية ضوئية ، مشعات حرارية ، منافذ لرسو السفن ، خلجان تجارب وأذرع آلية. وقد أطلقت وحدات اللواء ISS التي كتبها الروسي بروتون و صواريخ سويوز والولايات المتحدة مكوكات الفضاء . ^[25] والخدمات المحطة من قبل مجموعة متنوعة من زيارة المركبة الفضائية: الروسية سويوز و التقدم ، و (سبيس اكس) التنين 2 ، وشركة نورثروب غرومان الفضاء أنظمة الدجاجة ، ^[26] وسابقا الأوروبي مركبة النقل المؤتمتة (ATV)، واليابانيةمركبة النقل H-II ، ^[7] و SpaceX Dragon 1 . تسمح مركبة دراجون الفضائية بإعادة الحمولة المضغوطة إلى الأرض ، والتي تُستخدم ، على سبيل المثال ، لإعادة التجارب العلمية إلى الوطن لمزيد من التحليل. اعتبارًا من أغسطس 2021 ^[update]، قام 244 رائد فضاء ورائد فضاء وسائح فضاء من 19 دولة مختلفة بزيارة محطة الفضاء ، والعديد منهم عدة مرات ؛ ويشمل ذلك 153 أمريكيًا و 50 روسيًا و 9 يابانيين و 8 كنديين و 5 إيطاليين وبرازيلي واحد. ^[27]

الغرض

كان الغرض من محطة الفضاء الدولية في الأصل هو أن تكون مختبرًا ومرصدًا ومصنعًا مع توفير النقل والصيانة وقاعدة انطلاق لمدار أرضي منخفض للبعثات المستقبلية المحتملة إلى القمر والمريخ والكويكبات. ومع ذلك ، لم تتحقق جميع الاستخدامات المتوخاة في مذكرة التفاهم الأولية بين وكالة ناسا وشركة روسكوزموس . ^[28] في سياسة الفضاء الوطنية للولايات المتحدة لعام 2010 ، مُنحت محطة الفضاء الدولية أدوارًا إضافية لخدمة الأغراض التجارية والدبلوماسية ^[29] والتعليمية. ^[30]

البحث العلمي

توفر محطة الفضاء الدولية منصة لإجراء البحث العلمي ، مع توفير الطاقة والبيانات والتبريد والطاقم لدعم التجارب. يمكن للمركبات الفضائية الصغيرة غير المأهولة أن توفر أيضًا منصات للتجارب ، خاصة تلك التي تنطوي على انعدام الجاذبية والتعرض للفضاء ، لكن المحطات الفضائية توفر بيئة طويلة الأجل حيث يمكن إجراء الدراسات لعقود ، جنبًا إلى جنب مع سهولة الوصول من قبل الباحثين البشريين. ^{[31] [32]}

تبسط محطة الفضاء الدولية التجارب الفردية من خلال السماح لمجموعات من التجارب بمشاركة نفس عمليات الإطلاق ووقت الطاقم. والأبحاث التي أجريت في طائفة واسعة من المجالات، بما في ذلك بيولوجيا الفضاء ، علم الفلك ، العلوم الفيزيائية ، علوم المواد ، الطقس الفضائي ، الأرصاد الجوية ، و البحوث الإنسان بما في ذلك الطب الفضائي و علوم الحياة . ^{[10] [11] [12] [33] [34]}يمكن للعلماء على الأرض الوصول إلى البيانات في الوقت المناسب ويمكنهم اقتراح تعديلات تجريبية على الطاقم. إذا كانت تجارب المتابعة ضرورية ، فإن عمليات الإطلاق المجدولة بشكل روتيني لمركبات إعادة التوريد تسمح بإطلاق أجهزة جديدة بسهولة نسبية. ^{[32] تقوم} أطقم العمل برحلات استكشافية لمدة عدة أشهر ، وتوفر ما يقرب من 160 شخصًا / ساعة في الأسبوع من العمل بطاقم مكون من ستة أفراد. ومع ذلك ، تستغرق صيانة المحطة قدرًا كبيرًا من وقت الطاقم. ^{[10] [35]}

ولعل أبرز تجارب محطة الفضاء الدولية هو مطياف ألفا المغناطيسي (AMS) ، والذي يهدف إلى اكتشاف المادة المظلمة والإجابة على أسئلة أساسية أخرى حول كوننا وهو لا يقل أهمية عن تلسكوب هابل الفضائي وفقًا لوكالة ناسا. تم إرساؤها حاليًا على المحطة ، ولم يكن من السهل استيعابها على منصة أقمار صناعية طيران مجانية بسبب احتياجاتها من الطاقة وعرض النطاق الترددي. ^{[36] [37]} في 3 أبريل 2013 ، أفاد العلماء أنه ربما تم اكتشاف تلميحات من المادة المظلمة بواسطة AMS. ^{[38] [39] [40] [41] [42] [43]} وفقًا للعلماء ، " النتائج الأولى من مطياف ألفا المغناطيسي المحمول في الفضاء يؤكد وجود فائض غير مبرر من البوزيترونات عالية الطاقة في الأشعة الكونية المرتبطة بالأرض ".

بيئة الفضاء معادية للحياة. يتميز الوجود غير المحمي في الفضاء بمجال إشعاع مكثف (يتكون أساسًا من البروتونات والجسيمات المشحونة دون الذرية الأخرى من الرياح الشمسية ، بالإضافة إلى الأشعة الكونية ) ، والفراغ العالي ، ودرجات الحرارة القصوى ، والجاذبية الصغرى. ^[44] بعض أشكال الحياة البسيطة ودعا القاسية ، ^[45] وكذلك اللافقاريات الصغيرة تسمى بطيء الخطو ^[46] يمكن البقاء على قيد الحياة في هذه البيئة في حالة جافة للغاية من خلال تجفيف .

البحوث الطبية يحسن المعرفة حول آثار التعرض الفضاء على المدى الطويل على الجسم البشري، بما في ذلك ضمور العضلات ، فقدان العظام ، وتحول السوائل. وسوف تستخدم هذه البيانات لتحديد ما إذا كانت عالية مدة البشرية رحلات الفضاء و استعمار الفضاء وممكنا. اعتبارًا من عام 2006 ^[update]، تشير البيانات الخاصة بفقدان العظام والضمور العضلي إلى أنه سيكون هناك خطر كبير من حدوث كسور ومشاكل في الحركة إذا هبط رواد الفضاء على كوكب بعد رحلة بحرية طويلة بين الكواكب ، مثل فترة الستة أشهر المطلوبة للسفر إلى المريخ . ^{[47] [48]}

يتم إجراء الدراسات الطبية على متن محطة الفضاء الدولية نيابة عن المعهد الوطني لبحوث الطب الحيوي في الفضاء (NSBRI). ومن أبرز هذه الدراسات التشخيصية المتقدمة بالموجات فوق الصوتية في دراسة الجاذبية الصغرى التي يقوم فيها رواد الفضاء بإجراء فحوصات بالموجات فوق الصوتية تحت إشراف خبراء عن بُعد. تتناول الدراسة تشخيص وعلاج الحالات الطبية في الفضاء. عادة ، لا يوجد طبيب على متن محطة الفضاء الدولية ، ويشكل تشخيص الحالات الطبية تحديًا. من المتوقع أن يكون لفحوصات الموجات فوق الصوتية الموجهة عن بعد تطبيق على الأرض في حالات الطوارئ والرعاية الريفية حيث يصعب الوصول إلى طبيب مدرب. ^{[49] [50] [51]}

في أغسطس 2020 ، أفاد العلماء أنه تم العثور على بكتيريا من الأرض ، وخاصة بكتيريا Deinococcus radiodurans ، والتي تتميز بمقاومة عالية للأخطار البيئية ، على قيد الحياة لمدة ثلاث سنوات في الفضاء الخارجي ، بناءً على الدراسات التي أجريت في محطة الفضاء الدولية. دعمت هذه النتائج فكرة panspermia ، وهي الفرضية القائلة بأن الحياة موجودة في جميع أنحاء الكون ، موزعة بطرق مختلفة ، بما في ذلك الغبار الفضائي ، والنيازك ، والكويكبات ، والمذنبات ، والكواكب أو المركبات الفضائية الملوثة. . ^{[52] [53]}

ازدادت أبحاث الاستشعار عن بعد للأرض ، وعلم الفلك ، وأبحاث الفضاء السحيق على محطة الفضاء الدولية بشكل كبير خلال 2010 بعد الانتهاء من الجزء المداري للولايات المتحدة في عام 2011. طوال أكثر من 20 عامًا من الباحثين في برنامج محطة الفضاء الدولية على متن محطة الفضاء الدولية وعلى الأرض طلب استجواب الهباء الجوي ، الأوزون ، البرق ، و أكاسيد في الغلاف الجوي للأرض، وكذلك الشمس ، والأشعة الكونية، الغبار الكوني ، المادة المضادة ، والمادة المظلمة في الكون. من أمثلة تجارب الاستشعار عن بعد لرؤية الأرض والتي تم إجراؤها على محطة الفضاء الدولية مرصد الكربون المداري 3 ، ISS-RapidScat، ECOSTRESS ، التحقيق في ديناميكيات النظام الإيكولوجي العالمي ، ونظام نقل الهباء الجوي السحابي . تشمل تلسكوبات وتجارب علم الفلك المعتمدة على ISS SOLAR ، ومستكشف التكوين الداخلي للنجم النيوتروني ، وتلسكوب Calorimetric Electron Telescope ، وشاشة صورة الأشعة السينية التي تغطي السماء بالكامل (MAXI) ، ومقياس الطيف المغناطيسي ألفا . ^{[11] [54]}

السقوط الحر

تبلغ قوة الجاذبية على ارتفاع محطة الفضاء الدولية حوالي 90٪ من قوة سطح الأرض ، لكن الأجسام الموجودة في المدار في حالة مستمرة من السقوط الحر ، مما يؤدي إلى حالة ظاهرة من انعدام الوزن . ^[55] ينزعج انعدام الوزن الملحوظ هذا من خلال خمسة تأثيرات منفصلة: ^[56]

• اسحب من الجو المتبقي.
• الاهتزازات من حركات الأنظمة الميكانيكية والطاقم.
• تفعيل جيروسكوبات التحكم باللحظات على متن الطائرة .
• إطلاق صاعق لتغييرات الموقف أو المدار.
• تأثيرات تدرج الجاذبية ، والمعروفة أيضًا باسم تأثيرات المد والجزر . العناصر الموجودة في مواقع مختلفة داخل محطة الفضاء الدولية ، إذا لم يتم توصيلها بالمحطة ، ستتبع مدارات مختلفة قليلاً. يجري ربط هذه العناصر ميكانيكيًا ببعض القوى الصغيرة التي تحافظ على تحرك المحطة كجسم صلب .

يدرس الباحثون تأثير بيئة شبه خالية من الوزن للمحطة على التطور والتطور والنمو والعمليات الداخلية للنباتات والحيوانات. رداً على بعض هذه البيانات ، تريد ناسا التحقيق في تأثيرات الجاذبية الصغرى على نمو الأنسجة ثلاثية الأبعاد التي تشبه الإنسان ، وبلورات البروتين غير العادية التي يمكن أن تتشكل في الفضاء. ^[11]

سيوفر التحقيق في فيزياء السوائل في الجاذبية الصغرى نماذج أفضل لسلوك السوائل. نظرًا لأنه يمكن دمج السوائل بشكل شبه كامل في الجاذبية الصغرى ، يقوم الفيزيائيون بفحص السوائل التي لا تمتزج جيدًا على الأرض. بالإضافة إلى ذلك ، فإن فحص التفاعلات التي تبطئ بسبب الجاذبية المنخفضة ودرجات الحرارة المنخفضة سيحسن فهمنا للموصلية الفائقة . ^[11]

تعد دراسة علم المواد نشاطًا مهمًا للبحث في محطة الفضاء الدولية ، بهدف جني الفوائد الاقتصادية من خلال تحسين التقنيات المستخدمة على أرض الواقع. ^[57] مجالات الاهتمام الأخرى تشمل تأثير بيئة الجاذبية المنخفضة على الاحتراق ، من خلال دراسة كفاءة الاحتراق والتحكم في الانبعاثات والملوثات. قد تحسن هذه النتائج المعرفة الحالية حول إنتاج الطاقة ، وتؤدي إلى فوائد اقتصادية وبيئية. ^[11]

استكشاف

توفر محطة الفضاء الدولية موقعًا في أمان نسبي لمدار أرضي منخفض لاختبار أنظمة المركبات الفضائية التي ستكون مطلوبة لبعثات طويلة الأمد إلى القمر والمريخ. يوفر هذا خبرة في العمليات والصيانة وكذلك أنشطة الإصلاح والاستبدال في المدار ، والتي ستكون مهارات أساسية في تشغيل المركبات الفضائية بعيدًا عن الأرض ، ويمكن تقليل مخاطر المهمة وتطوير قدرات المركبات الفضائية بين الكواكب. ^[13] بالإشارة إلى تجربة MARS-500 ، تنص وكالة الفضاء الأوروبية على أنه "في حين أن محطة الفضاء الدولية ضرورية للإجابة على الأسئلة المتعلقة بالتأثير المحتمل لانعدام الوزن والإشعاع والعوامل الأخرى الخاصة بالفضاء ، فإن الجوانب مثل تأثير العزلة والحبس على المدى الطويل يمكن معالجتها بشكل أكثر ملاءمة من خلال عمليات المحاكاة الأرضية ". ^[58]اقترح سيرجي كراسنوف ، رئيس برامج رحلات الفضاء البشرية لوكالة الفضاء الروسية ، روسكوزموس ، في عام 2011 إمكانية تنفيذ "نسخة أقصر" من MARS-500 على محطة الفضاء الدولية. ^[59]

في عام 2009 ، أشار سيرجي كراسنوف إلى قيمة إطار الشراكة نفسه ، قائلاً: "عند المقارنة مع الشركاء الذين يعملون بشكل منفصل ، يمكن أن يمنحنا الشركاء الذين يطورون قدرات وموارد تكميلية مزيدًا من التأكيد على نجاح وسلامة استكشاف الفضاء. وتساعد محطة الفضاء الدولية بشكل أكبر النهوض باستكشاف الفضاء القريب من الأرض وتحقيق البرامج المستقبلية للبحث واستكشاف النظام الشمسي ، بما في ذلك القمر والمريخ ". ^[60] قد تكون مهمة مأهولة إلى المريخ جهدًا متعدد الجنسيات يشمل وكالات فضاء ودولًا خارج الشراكة الحالية لمحطة الفضاء الدولية. في عام 2010 ، صرح المدير العام لوكالة الفضاء الأوروبية ، جان جاك دوردين ، أن وكالته مستعدة لاقتراح الشركاء الأربعة الآخرين دعوة الصين والهند وكوريا الجنوبية للانضمام إلى شراكة محطة الفضاء الدولية. ^[61]صرح رئيس ناسا تشارلز بولدن في فبراير 2011 ، "من المرجح أن تكون أي مهمة إلى المريخ جهدًا عالميًا". ^[٦٢] حاليًا ، تمنع التشريعات الفيدرالية الأمريكية تعاون ناسا مع الصين في مشاريع الفضاء. ^[63]

التعليم والتواصل الثقافي

يوفر طاقم ISS فرصًا للطلاب على الأرض من خلال إجراء تجارب طورها الطلاب ، وإجراء عروض توضيحية تعليمية ، والسماح بمشاركة الطلاب في إصدارات الفصول الدراسية من تجارب محطة الفضاء الدولية ، وإشراك الطلاب مباشرةً باستخدام الراديو ، ووصلة الفيديو ، والبريد الإلكتروني. ^{[7] [64]} تقدم ESA مجموعة واسعة من المواد التعليمية المجانية التي يمكن تنزيلها لاستخدامها في الفصول الدراسية. ^[65] في درس واحد ، يمكن للطلاب التنقل في نموذج ثلاثي الأبعاد للجزء الداخلي والخارجي لمحطة الفضاء الدولية ، ومواجهة تحديات عفوية لحلها في الوقت الفعلي. ^[66]

تهدف JAXA إلى إلهام الأطفال "لمتابعة الحرفية" وزيادة "وعيهم بأهمية الحياة ومسؤولياتهم في المجتمع". ^{[67] من} خلال سلسلة من الأدلة التعليمية ، يطور الطلاب فهمًا أعمق للماضي والمستقبل القريب المدى لرحلات الفضاء المأهولة ، بالإضافة إلى الأرض والحياة. ^{[68] [69]} في تجارب "البذور في الفضاء" التي أجرتها وكالة جاكسا ، تم استكشاف التأثيرات الطفرية لرحلات الفضاء على بذور النباتات على متن محطة الفضاء الدولية من خلال زراعة بذور عباد الشمس التي طارت على محطة الفضاء الدولية لمدة تسعة أشهر تقريبًا. في المرحلة الأولى من استخدام Kib من عام 2008 إلى منتصف عام 2010 ، أجرى باحثون من أكثر من اثنتي عشرة جامعة يابانية تجارب في مجالات متنوعة. ^[70]

الأنشطة الثقافية هي هدف رئيسي آخر لبرنامج ISS. قال تيتسو تاناكا ، مدير مركز بيئة واستخدام الفضاء التابع لوكالة جاكسا: "هناك شيء ما في الفضاء يمس حتى الأشخاص غير المهتمين بالعلوم." ^[71]

راديو الهواة على محطة الفضاء الدولية (ARISS) هو برنامج تطوعي يشجع الطلاب في جميع أنحاء العالم على متابعة وظائف في مجالات العلوم والتكنولوجيا والهندسة والرياضيات ، من خلال فرص الاتصالات اللاسلكية للهواة مع طاقم محطة الفضاء الدولية. ARISS هي مجموعة عمل دولية ، تتكون من وفود من تسع دول بما في ذلك عدة دول في أوروبا ، بالإضافة إلى اليابان وروسيا وكندا والولايات المتحدة. في المناطق التي لا يمكن فيها استخدام أجهزة الراديو ، تقوم مكبرات الصوت بتوصيل الطلاب بالمحطات الأرضية التي تقوم بعد ذلك بتوصيل المكالمات بالمحطة الفضائية. ^[72]

First Orbit هو فيلم وثائقي طويل عام 2011 عن فوستوك 1 ، أول رحلة فضائية مأهولة حول الأرض. من خلال مطابقة مدار محطة الفضاء الدولية مع مدار فوستوك 1 بأكبر قدر ممكن ، من حيث المسار الأرضي والوقت من اليوم ، تمكن المخرج الوثائقي كريستوفر رايلي ورائد الفضاء في وكالة الفضاء الأوروبية باولو نيسبولي من تصوير المشهد الذيرآه يوري غاغارين في مداره الرائد الرحلات الفضائية. تم قطع هذه اللقطات الجديدة جنبًا إلى جنب مع التسجيلات الصوتية الأصلية لمهمة فوستوك 1 المأخوذة من أرشيف الدولة الروسية. يُنسب إلى نيسبولي منصب مدير التصوير الفوتوغرافي لهذا الفيلم الوثائقي ، حيث سجل غالبية اللقطات بنفسه خلال الرحلة الاستكشافية 26 /27 . ^[73] تم بث الفيلم في العرض الأول عالميًا على YouTube في عام 2011 بموجب ترخيص مجاني عبر موقع الويب firstorbit.org . ^[74]

في مايو 2013، قائد كريس هادفيلد النار على الموسيقى والفيديو من ديفيد باوي الصورة " الفضاء غرائب " على متن المحطة، والذي صدر على موقع يوتيوب. ^{[75] [76]} كان أول فيديو موسيقي يتم تصويره في الفضاء. ^[77]

في نوفمبر تشرين الثاني عام 2017، أثناء مشاركتهم في الحملة 52 / 53 في محطة الفضاء الدولية، جعلت باولو نيسبولي اثنين تسجيلات صوته المنطوقة (واحد في اللغة الإنجليزية والآخر في وطنه الإيطالية)، لاستخدامها في ويكيبيديا المواد. كانت هذه هي أول محتوى تم إنشاؤه في الفضاء خصيصًا لـ Wikipedia. ^{[78] [79]}

البناء

التصنيع

نظرًا لأن محطة الفضاء الدولية هي مشروع تعاوني متعدد الجنسيات ، فقد تم تصنيع مكونات التجميع في المدار في بلدان مختلفة حول العالم. تبدأ في 1990s منتصف، والمكونات الولايات المتحدة المصير ، الوحدة ، و الهيكل المتكامل تروس ، و ألواح الطاقة الشمسية ملفقة في مركز مارشال لرحلات الفضاء و مرفق الجمعية Michoud . تم تسليم هذه الوحدات ل عمليات البناء والخروج و مرفق محطة الفضاء تجهيز (SSPF) لالتجميع النهائي ومعالجة للانطلاق. ^[80]

تم تصنيع الوحدات الروسية ، بما في ذلك Zarya و Zvezda ، في مركز Khrunichev State Research and Production Space في موسكو . تم تصنيع Zvezda في البداية في عام 1985 كمكون لـ Mir-2 ، ولكن لم يتم إطلاقه مطلقًا وأصبح بدلاً من ذلك وحدة خدمة ISS. ^[81]

و كالة الفضاء الأوروبية (ESA) كولومبوس تم تصنيعها وحدة في EADS مرافق استريوم النقل الفضائي في بريمن ، ألمانيا، جنبا إلى جنب مع العديد من المقاولين الآخرين في جميع أنحاء أوروبا. ^[82] وغيرها من المدمج ESA modules- الوئام ، الهدوء ، و ليوناردو MPLM ، و قبة -were تصنيعها في البداية في تاليس الينيا الفضائية مصنع في تورينو، إيطاليا. ^[83] تم نقل الهياكل الفولاذية الهيكلية للوحدات بواسطة الطائرات إلى مركز كينيدي للفضاء SSPF لمعالجة الإطلاق. ^{[الاقتباس مطلوب ]}

و التجارب اليابانية وحدة كيبو ، كانت ملفقة في مختلف مرافق التصنيع التكنولوجيا في اليابان، في ناسدا (الآن جاكسا) مركز الفضاء تسوكوبا ، و معهد علوم الفضاء والملاحة الفضائية . و كيبو تم نقل وحدة بحرا وجوا بواسطة طائرة إلى SSPF. ^[84]

و نظام الخدمة المتنقلة ، التي تتألف من Canadarm2 و شخص آلي بذراعين تابع التصدي لاعبا اساسيا، تم تصنيعها في المصانع المختلفة في كندا (مثل ديفيد فلوريدا مختبر ) والولايات المتحدة، بموجب عقد من قبل وكالة الفضاء الكندية . تم بناء نظام القاعدة المتنقلة ، وهو إطار اتصال لـ Canadarm2 مثبت على قضبان ، بواسطة شركة Northrop Grumman .

تجميع

بدأ تجميع محطة الفضاء الدولية ، وهو مسعى رئيسي في هندسة الفضاء ، في نوفمبر 1998. ^{[4] تم} إطلاق الوحدات الروسية ورسو آليًا ، باستثناء Rassvet . تم تسليم جميع الوحدات الأخرى بواسطة مكوك الفضاء ، الأمر الذي تطلب تركيبه بواسطة محطة الفضاء الدولية وأعضاء طاقم المكوك باستخدام Canadarm2 (SSRMS) وأنشطة خارج المركبات (EVAs) ؛ اعتبارًا من 5 يونيو 2011 ^[update]، أضافوا 159 مكونًا خلال أكثر من 1000 ساعة من EVA. نشأت 127 من عمليات السير في الفضاء هذه من المحطة ، وتم إطلاق الـ 32 عملية المتبقية من غرف معادلة الضغط لمكوكات الفضاء الراسية. ^[85] و زاوية بيتامن المحطة كان لابد من النظر فيها في جميع الأوقات أثناء البناء. ^[86]

تم إطلاق الوحدة الأولى من محطة الفضاء الدولية ، زاريا ، في 20 نوفمبر 1998 على صاروخ بروتون روسي مستقل . لقد وفرت الدفع ، والتحكم في الموقف ، والاتصالات ، والطاقة الكهربائية ، لكنها افتقرت إلى وظائف دعم الحياة على المدى الطويل. بعد أسبوعين، وحدة نمطية سلبية NASA الوحدة انطلقت على متن مكوك الفضاء الرحلة STS-88 وتعلق زاريا من قبل رواد الفضاء خلال EVAs. تحتوي هذه الوحدة على محولي تزاوج مضغوط (PMAs) ، أحدهما يتصل بشكل دائم بـ Zarya ، والآخر يسمح للمكوك الفضائي بالالتحام بالمحطة الفضائية. في ذلك الوقت كانت المحطة الروسية (السوفيتية) ميركانت لا تزال مأهولة بالسكان ، وظلت محطة الفضاء الدولية بدون طاقم لمدة عامين. في 12 يوليو 2000 ، تم إطلاق Zvezda في المدار. نشرت الأوامر المبرمجة مسبقًا على متن الطائرة المصفوفات الشمسية وهوائي الاتصالات. أصبح بعد ذلك الهدف السلبي للالتقاء مع Zarya و Unity : فقد حافظت على مدار للمحطة بينما كانت مركبة Zarya - Unity تقوم بالالتقاء والالتحام عبر التحكم الأرضي ونظام الالتقاء الآلي الروسي ونظام الالتحام. زاريا الصورة نقل الكمبيوتر السيطرة على محطة ل زفيزدا الصورة الكمبيوتر بعد رسو السفن في وقت قريب. أضافت Zvezda أماكن للنوم ، ومرحاض ، ومطبخ ، و CO₂ أجهزة تنقية الغاز ، مزيل الرطوبة ، مولدات الأكسجين ، معدات التمرين ، بالإضافة إلى اتصالات البيانات والصوت والتلفزيون مع التحكم في المهمة. وقد أتاح هذا السكن الدائم للمحطة. ^{[87] [88]}

وصل أول طاقم مقيم ، إكسبيديشن 1 ، في نوفمبر 2000 على متن سويوز TM-31 . في نهاية اليوم الأول على المحطة ، طلب رائد الفضاء بيل شيبرد استخدام علامة الاتصال اللاسلكي " ألفا " ، التي فضلها هو ورائد الفضاء كريكاليف على " محطة الفضاء الدولية " الأكثر تعقيدًا . ^[89] تم استخدام اسم " Alpha " سابقًا للمحطة في أوائل التسعينيات ، ^[90] وكان استخدامه مسموحًا به لكامل الرحلة 1. ^[91] كان شيبرد يدعو إلى استخدام اسم جديد للمشروع مدراء لبعض الوقت. الرجوع إلى تقليد بحريفي مؤتمر صحفي قبل الإطلاق قال: "منذ آلاف السنين ، كان البشر يذهبون إلى البحر على متن السفن. لقد صمم الناس وبنوا هذه السفن ، وأطلقوها بشعور جيد بأن الاسم سيجلب الحظ السعيد للطاقم والنجاح في رحلتهم ". ^[92] يوري سيمينوف ، رئيس مؤسسة الفضاء الروسية إنيرجيا في ذلك الوقت ، رفض اسم " ألفا " لأنه شعر أن مير كان أول محطة فضاء معيارية ، لذا فإن أسماء " بيتا " أو " مير  2" لمحطة الفضاء الدولية سيكون أكثر ملاءمة. ^{[91] [93] [94]}

وصلت البعثة الأولى في منتصف الطريق بين رحلات STS-92 و STS-97 . أضافت كلٌّ من هاتين الرحلتين المكوكيتين الفضائيتين أجزاءً من هيكل تروس المتكامل للمحطة ، والذي زود المحطة باتصالات Ku-band للتلفزيون الأمريكي ، ودعمًا إضافيًا للموقف مطلوبًا للكتلة الإضافية لـ USOS ، ومصفوفات شمسية كبيرة تكمل الطاقة الشمسية الأربعة الموجودة بالمحطة. المصفوفات. ^[95]

على مدى العامين المقبلين ، استمرت المحطة في التوسع. A سويوز-U تسليم الصواريخ بيرس الالتحام المقصورة . قام كل من Space Shuttles Discovery و Atlantis و Endeavour بتسليم مختبر Destiny و Quest airlock ، بالإضافة إلى ذراع الروبوت الرئيسي للمحطة ، Canadarm2 ، والعديد من الأجزاء الأخرى من هيكل Truss المتكامل.

توقف جدول التوسع بسبب كارثة مكوك الفضاء كولومبيا في عام 2003 وما نجم عن ذلك من فجوة في الرحلات الجوية. تم تأريض مكوك الفضاء حتى عام 2005 باستخدام STS-114 بواسطة ديسكفري . ^[96]

تم استئناف التجميع في عام 2006 مع وصول STS-115 مع Atlantis ، والتي سلمت المجموعة الثانية من صفائف الطاقة الشمسية للمحطة. تم تسليم العديد من مقاطع الجمالون ومجموعة ثالثة من المصفوفات على STS-116 و STS-117 و STS-118 . نتيجة للتوسع الكبير في قدرات توليد الطاقة للمحطة ، يمكن استيعاب المزيد من الوحدات المضغوطة ، وأضيفت عقدة Harmony ومختبر كولومبوس الأوروبي. سرعان ما تبع هؤلاء المكونان الأولان من Kibō . في مارس 2009 ، STS-119أكمل هيكل الجمالون المتكامل بتركيب المجموعة الرابعة والأخيرة من المصفوفات الشمسية. تم تسليم الجزء الأخير من Kibō في يوليو 2009 على STS-127 ، تليها وحدة Poisk الروسية . تم تسليم العقدة الثالثة ، Tranquility ، في فبراير 2010 خلال STS-130 بواسطة مكوك الفضاء إنديفور ، إلى جانب Cupola ، تليها في مايو 2010 الوحدة الروسية قبل الأخيرة ، Rassvet . تم تسليم Rassvet بواسطة مكوك الفضاء Atlantis على STS-132 مقابل تسليم البروتون الروسي لـ Zarya الممولة من الولايات المتحدةوحدة في عام 1998. ^[97] آخر وحدة مضغوطة من USOS ، ليوناردو ، تم إحضارها إلى المحطة في فبراير 2011 في الرحلة الأخيرة من ديسكفري ، STS-133 . ^[98] و ألفا المغناطيسي مطياف ألقاها انديفور على STS-134 في نفس العام. ^[99]

اعتبارًا من يونيو 2011 ^[update]، تتكون المحطة من 15 وحدة مضغوطة وهيكل تروس متكامل. لا يزال يتعين إطلاق ثلاث وحدات ، بما في ذلك وحدة Prichal ، ووحدتي طاقة تدعى NEM-1 و NEM-2. ^[100] رست أحدث وحدة أبحاث أولية روسية Nauka في يوليو 2021 ، ^[101] جنبًا إلى جنب مع الذراع الروبوتية الأوروبية والتي ستكون قادرة على نقل نفسها إلى أجزاء مختلفة من الوحدات الروسية للمحطة. ^[102]

تتغير الكتلة الإجمالية للمحطة بمرور الوقت. يبلغ إجمالي كتلة الإطلاق للوحدات في المدار حوالي 417.289 كجم (919.965 رطلاً) (اعتبارًا من 3 سبتمبر 2011 ^[update]). ^[103] تضاف كتلة التجارب ، وقطع الغيار ، والأمتعة الشخصية ، والطاقم ، والمواد الغذائية ، والملابس ، والوقود ، وإمدادات المياه ، وإمدادات الغاز ، والمركبات الفضائية الراسية ، وعناصر أخرى إلى الكتلة الكلية للمحطة. يتم تهوية غاز الهيدروجين باستمرار من خلال مولدات الأكسجين.

هيكل

محطة الفضاء الدولية هي محطة فضائية معيارية من الجيل الثالث ^[104] . ^[١٠٥] يمكن أن تسمح المحطات المعيارية بإضافة وحدات أو إزالتها من الهيكل الحالي ، مما يتيح قدرًا أكبر من المرونة.

يوجد أدناه رسم تخطيطي لمكونات المحطة الرئيسية. المناطق الزرقاء عبارة عن أقسام مضغوطة يمكن للطاقم الوصول إليها دون استخدام بدلات الفضاء. تم الإشارة إلى البنية الفوقية للمحطة غير المضغوطة باللون الأحمر. تظهر المكونات المخططة باللون الأبيض والمكونات السابقة باللون الرمادي. المكونات الأخرى غير المضغوطة صفراء. و الوحدة عقدة ينضم مباشرة إلى القدر المختبر. من أجل الوضوح ، يتم عرضهم بشكل منفصل. شوهدت حالات مماثلة أيضًا في أجزاء أخرى من الهيكل.

ميناء لرسو السفن الروسي

مجموعة الشمسية

Zvezda DOS-8 (وحدة الخدمة)

مجموعة الشمسية

ميناء لرسو السفن الروسي

قفل غرفة معادلة الضغط من Poisk (MRM-2)

بيرس غرفة معادلة الضغط

ميناء لرسو السفن الروسي

المبرد الحراري

مجموعة الشمسية

موقع العمل المحمول ERA

الذراع الروبوتية الأوروبية (ERA)

ميناء لرسو السفن الروسي

Nauka MLM (معمل)

ميناء لرسو السفن الروسي

ميناء لرسو السفن الروسي

بريشال

ميناء لرسو السفن الروسي

مجموعة الشمسية

تجربة Nauka MLM غرفة معادلة الضغط

ميناء لرسو السفن الروسي

ميناء لرسو السفن الروسي

مجموعة الطاقة الشمسية (تراجعت)

Zarya FGB (الوحدة الأولى)

مجموعة الطاقة الشمسية (تراجعت)

Rassvet (MRM-1)

ميناء لرسو السفن الروسي

سلطة النقد الفلسطينية 1

ميناء رسو المركبة الفضائية للشحن

خليج البضائع ليوناردو

موطن BEAM

كويست غرفة معادلة الضغط

عقدة الوحدة 1

عقدة الهدوء 3

غرفة معادلة الضغط الأسقف

إيروسا

ESP-2

قبة

مجموعة الشمسية

مجموعة الشمسية

المبرد الحراري

المبرد الحراري

مجموعة الشمسية

مجموعة الشمسية

إيروسا

ELC 2 ، AMS

تروس Z1

مركز اللغة الإنجليزية 3

S5 / 6 تروس

S3 / S4 تروس

S1 تروس

S0 تروس

P1 تروس

P3 / P4 تروس

P5 / 6 تروس

ELC 4 ، ESP 3

مركز اللغة الإنجليزية 1

الذراع الروبوتية ديكستر

الذراع الروبوتية Canadarm2

مجموعة الشمسية

مجموعة الشمسية

مجموعة الشمسية

إيروسا

مجموعة الشمسية

إيروسا

إيروسا

ESP-1

Destiny laboratory

Kibō logistics cargo bay

iROSA

IDA 3 docking adapter

Cargo spacecraft berthing port

PMA 3 docking port

Kibō robotic arm

External payloads

Columbus laboratory

Harmony Node 2

Kibō laboratory

Kibō external platform

PMA 2 docking port

IDA 2 docking adapter

Axiom modules

Pressurised modules

Zarya

Zarya (Russian: Заря, lit. 'Dawn'^[a]), also known as the Functional Cargo Block or FGB (from the Russian: "Функционально-грузовой блок", lit. 'Funktsionalno-gruzovoy blok' or ФГБ), is the first module of the ISS to have been launched.^[106] The FGB provided electrical power, storage, propulsion, and guidance to the ISS during the initial stage of assembly. With the launch and assembly in orbit of other modules with more specialized functionality, Zarya is now^[when?] primarily used for storage, both inside the pressurized section and in the externally mounted fuel tanks. The Zarya is a descendant of the TKS spacecraft designed for the Russian Salyut program. The name Zarya ("Dawn") was given to the FGB because it signified the dawn of a new era of international cooperation in space. Although it was built by a Russian company, it is owned by the United States.^[107]

Unity

The Unity connecting module, also known as Node 1, is the first U.S.-built component of the ISS. It connects the Russian and U.S. segments of the station, and is where crew eat meals together.

The module is cylindrical in shape, with six berthing locations (forward, aft, port, starboard, zenith, and nadir) facilitating connections to other modules. Unity measures 4.57 metres (15.0 ft) in diameter, is 5.47 metres (17.9 ft) long, made of steel, and was built for NASA by Boeing in a manufacturing facility at the Marshall Space Flight Center in Huntsville, Alabama. Unity is the first of the three connecting modules; the other two are Harmony and Tranquility.

Zvezda

Zvezda (Russian: Звезда, meaning "star"), Salyut DOS-8, also known as the Zvezda Service Module, is a module of the ISS. It was the third module launched to the station, and provides all of the station's life support systems, some of which are supplemented in the USOS, as well as living quarters for two crew members. It is the structural and functional center of the Russian Orbital Segment, which is the Russian part of the ISS. Crew assemble here to deal with emergencies on the station.^{[108][109][110]}

The module was manufactured by RKK Energia, with major sub-contracting work by GKNPTs Khrunichev.^[111] Zvezda was launched on a Proton rocket on July 12, 2000, and docked with the Zarya module on July 26, 2000.

Destiny

The Destiny module, also known as the U.S. Lab, is the primary operating facility for U.S. research payloads aboard the ISS.^[112][113] It was berthed to the Unity module and activated over a period of five days in February, 2001.^[114] Destiny is NASA's first permanent operating orbital research station since Skylab was vacated in February 1974. The Boeing Company began construction of the 14.5-tonne (32,000 lb) research laboratory in 1995 at the Michoud Assembly Facility and then the Marshall Space Flight Center in Huntsville, Alabama.^[112] Destiny was shipped to the Kennedy Space Center in Florida in 1998, and was turned over to NASA for pre-launch preparations in August 2000. It launched on February 7, 2001, aboard the Space Shuttle Atlantis on STS-98.^[114] Astronauts work inside the pressurized facility to conduct research in numerous scientific fields. Scientists throughout the world would use the results to enhance their studies in medicine, engineering, biotechnology, physics, materials science, and Earth science.^[113]

Quest

The Quest Joint Airlock, previously known as the Joint Airlock Module, is the primary airlock for the ISS. Quest was designed to host spacewalks with both Extravehicular Mobility Unit (EMU) spacesuits and Orlan space suits. The airlock was launched on STS-104 on July 14, 2001. Before Quest was attached, Russian spacewalks using Orlan suits could only be done from the Zvezda service module, and American spacewalks using EMUs were only possible when a Space Shuttle was docked. The arrival of Pirs docking compartment on September 16, 2001 provided another airlock from which Orlan spacewalks can be conducted.^{[citation needed]}

Poisk

Pirs (Russian: Пирс, lit. 'Pier') and Poisk (Russian: По́иск, lit. 'Search') are Russian airlock modules, each having two identical hatches. An outward-opening hatch on the Mir space station failed after it swung open too fast after unlatching, because of a small amount of air pressure remaining in the airlock.^[115] All EVA hatches on the ISS open inwards and are pressure-sealing. Pirs was used to store, service, and refurbish Russian Orlan suits and provided contingency entry for crew using the slightly bulkier American suits. The outermost docking ports on both airlocks allow docking of Soyuz and Progress spacecraft, and the automatic transfer of propellants to and from storage on the ROS.^[116]

Harmony

Harmony, also known as Node 2, is the "utility hub" of the ISS. It connects the laboratory modules of the United States, Europe and Japan, as well as providing electrical power and electronic data. Sleeping cabins for four of the crew are housed here.^[117]

Harmony was successfully launched into space aboard Space Shuttle flight STS-120 on October 23, 2007.^[118][119] After temporarily being attached to the port side of the Unity node,^[120][121] it was moved to its permanent location on the forward end of the Destiny laboratory on November 14, 2007.^[122] Harmony added 2,666 cubic feet (75.5 m³) to the station's living volume, an increase of almost 20 percent, from 15,000 cu ft (420 m³) to 17,666 cu ft (500.2 m³). Its successful installation meant that from NASA's perspective, the station was considered to be "U.S. Core Complete".

Tranquility

Tranquility, also known as Node 3, is a module of the ISS. It contains environmental control systems, life support systems, a toilet, exercise equipment, and an observation cupola.

The European Space Agency and the Italian Space Agency had Tranquility manufactured by Thales Alenia Space. A ceremony on November 20, 2009 transferred ownership of the module to NASA.^[123] On February 8, 2010, NASA launched the module on the Space Shuttle's STS-130 mission.

Columbus

Columbus is a science laboratory that is part of the ISS and is the largest single contribution to the station made by the European Space Agency.

Like the Harmony and Tranquility modules, the Columbus laboratory was constructed in Turin, Italy by Thales Alenia Space. The functional equipment and software of the lab was designed by EADS in Bremen, Germany. It was also integrated in Bremen before being flown to the Kennedy Space Center in Florida in an Airbus Beluga. It was launched aboard Space Shuttle Atlantis on February 7, 2008, on flight STS-122. It is designed for ten years of operation. The module is controlled by the Columbus Control Centre, located at the German Space Operations Center, part of the German Aerospace Center in Oberpfaffenhofen near Munich, Germany.

The European Space Agency has spent €1.4 billion (about US$2 billion) on building Columbus, including the experiments it carries and the ground control infrastructure necessary to operate them.^[124]

Kibō

The Japanese Experiment Module (JEM), nicknamed Kibō (きぼう, Kibō, Hope), is a Japanese science module for the International Space Station (ISS) developed by JAXA. It is the largest single ISS module, and is attached to the Harmony module. The first two pieces of the module were launched on Space Shuttle missions STS-123 and STS-124. The third and final components were launched on STS-127.^[125]

Cupola

The Cupola is an ESA-built observatory module of the ISS. Its name derives from the Italian word cupola, which means "dome". Its seven windows are used to conduct experiments, dockings and observations of Earth. It was launched aboard Space Shuttle mission STS-130 on 8 February 2010 and attached to the Tranquility (Node 3) module. With the Cupola attached, ISS assembly reached 85 percent completion. The Cupola's central window has a diameter of 80 cm (31 in).^[126]

Rassvet

Rassvet (Russian: Рассвет; lit. "dawn"), also known as the Mini-Research Module 1 (MRM-1) (Russian: Малый исследовательский модуль, МИМ 1) and formerly known as the Docking Cargo Module (DCM), is a component of the International Space Station (ISS). The module's design is similar to the Mir Docking Module launched on STS-74 in 1995. Rassvet is primarily used for cargo storage and as a docking port for visiting spacecraft. It was flown to the ISS aboard Space Shuttle Atlantis on the STS-132 mission on 14 May 2010,^[127] and was connected to the ISS on 18 May 2010.^[128] The hatch connecting Rassvet with the ISS was first opened on 20 May 2010.^[129] On 28 June 2010, the Soyuz TMA-19 spacecraft performed the first docking with the module.^[130]

MLM outfittings

Equipment weighing 1.4 metric tons for Nauka was launched in May 2010, attached to the outside of Rassvet (Mini-Research Module 1) on STS-132 (as part of an agreement with NASA) and delivered by Space Shuttle Atlantis. The equipment includes a spare elbow joint for the European Robotic Arm (ERA) (launched with Nauka) and an ERA portable workpost used during EVAs, a heat exchanger, radiators, internal hardware and an experimental airlock for launching cubesats, to be positioned on the modified passive forward port near the nadir end of the module.^[131]

The deployable radiator will be used to add additional cooling capability to Nauka, which will enable the module to host more scientific experiments. The airlock will be used only to pass experiments inside and outside the module, with the aid of ERA — very similar to the Japanese airlock and Nanoracks Bishop Airlock on the U.S. segment of the station.^[131]

The ERA will be used to remove the radiator and airlock from Rassvet and transfer them over to Nauka – with an extension boom and spare elbow joint being required to allow ERA to reach the airlock. This process is expected to take several months. A portable work platform will also be transferred over, which can attach to the end of the ERA to allow cosmonauts to "ride" on the end of the arm during spacewalks.^[132]

Leonardo

The Leonardo Permanent Multipurpose Module (PMM) is a module of the International Space Station. It was flown into space aboard the Space Shuttle on STS-133 on 24 February 2011 and installed on 1 March. Leonardo is primarily used for storage of spares, supplies and waste on the ISS, which was until then stored in many different places within the space station. It is also the personal hygiene area for the astronauts who live in the US Orbital Segment. The Leonardo PMM was a Multi-Purpose Logistics Module (MPLM) before 2011, but was modified into its current configuration. It was formerly one of two MPLM used for bringing cargo to and from the ISS with the Space Shuttle. The module was named for Italian polymath Leonardo da Vinci.

Bigelow Expandable Activity Module

The Bigelow Expandable Activity Module (BEAM) is an experimental expandable space station module developed by Bigelow Aerospace, under contract to NASA, for testing as a temporary module on the International Space Station (ISS) from 2016 to at least 2020. It arrived at the ISS on April 10, 2016,^[133] was berthed to the station on April 16, and was expanded and pressurized on May 28, 2016.

International Docking Adapters

The International Docking Adapter (IDA) is a spacecraft docking system adapter developed to convert APAS-95 to the NASA Docking System (NDS). An IDA is placed on each of the ISS's two open Pressurized Mating Adapters (PMAs), both of which are connected to the Harmony module.

Two International Docking Adapters are currently installed aboard the Station. Originally, IDA-1 was planned to be installed on PMA-2, located at Harmony's forward port, and IDA-2 would be installed on PMA-3 at Harmony's zenith. After IDA 1 was destroyed in a launch incident, IDA-2 was installed on PMA-2 on 19 August 2016,^[134] while IDA-3 was later installed on PMA-3 on 21 August 2019.^[135]

Bishop Airlock Module

The NanoRacks Bishop Airlock Module is a commercially funded airlock module launched to the ISS on SpaceX CRS-21 on 6 December 2020.^[136][137] The module was built by NanoRacks, Thales Alenia Space, and Boeing.^[138] It will be used to deploy CubeSats, small satellites, and other external payloads for NASA, CASIS, and other commercial and governmental customers.^[139]

Nauka

Nauka (Russian: Наука, lit. 'Science'), also known as the Multipurpose Laboratory Module-Upgrade (MLM-U), (Russian: Многоцелевой лабораторный модуль, усоверше́нствованный, or МЛМ-У), is a component of the ISS that was launched on 21 July 2021, 14:58 UTC. The MLM-U is funded by the Roscosmos State Corporation. In the original ISS plans, Nauka was to use the location of the Docking and Stowage Module (DSM), but the DSM was later replaced by the Rassvet module and moved to Zarya's nadir port. Nauka was successfully docked on 29 July 2021, 13:29 UTC to Zvezda's nadir port, replacing the Pirs module.

Unpressurised elements

The ISS has a large number of external components that do not require pressurisation. The largest of these is the Integrated Truss Structure (ITS), to which the station's main solar arrays and thermal radiators are mounted.^[140] The ITS consists of ten separate segments forming a structure 108.5 metres (356 ft) long.^[4]

The station was intended to have several smaller external components, such as six robotic arms, three External Stowage Platforms (ESPs) and four ExPRESS Logistics Carriers (ELCs).^[141][142] While these platforms allow experiments (including MISSE, the STP-H3 and the Robotic Refueling Mission) to be deployed and conducted in the vacuum of space by providing electricity and processing experimental data locally, their primary function is to store spare Orbital Replacement Units (ORUs). ORUs are parts that can be replaced when they fail or pass their design life, including pumps, storage tanks, antennas, and battery units. Such units are replaced either by astronauts during EVA or by robotic arms.^[143] Several shuttle missions were dedicated to the delivery of ORUs, including STS-129,^[144] STS-133^[145] and STS-134.^[146] As of January 2011^[update], only one other mode of transportation of ORUs had been utilised—the Japanese cargo vessel HTV-2—which delivered an FHRC and CTC-2 via its Exposed Pallet (EP).^{[147][needs update]}

There are also smaller exposure facilities mounted directly to laboratory modules; the Kibō Exposed Facility serves as an external "porch" for the Kibō complex,^[148] and a facility on the European Columbus laboratory provides power and data connections for experiments such as the European Technology Exposure Facility^[149][150] and the Atomic Clock Ensemble in Space.^[151] A remote sensing instrument, SAGE III-ISS, was delivered to the station in February 2017 aboard CRS-10,^[152] and the NICER experiment was delivered aboard CRS-11 in June 2017.^[153] The largest scientific payload externally mounted to the ISS is the Alpha Magnetic Spectrometer (AMS), a particle physics experiment launched on STS-134 in May 2011, and mounted externally on the ITS. The AMS measures cosmic rays to look for evidence of dark matter and antimatter.^[154][155]

The commercial Bartolomeo External Payload Hosting Platform, manufactured by Airbus, was launched on 6 March 2020 aboard CRS-20 and attached to the European Columbus module. It will provide an additional 12 external payload slots, supplementing the eight on the ExPRESS Logistics Carriers, ten on Kibō, and four on Columbus. The system is designed to be robotically serviced and will require no astronaut intervention. It is named after Christopher Columbus's younger brother.^{[156][157][158]}

Robotic arms and cargo cranes

The Integrated Truss Structure serves as a base for the station's primary remote manipulator system, the Mobile Servicing System (MSS), which is composed of three main components:

• Canadarm2, the largest robotic arm on the ISS, has a mass of 1,800 kilograms (4,000 lb) and is used to: dock and manipulate spacecraft and modules on the USOS; hold crew members and equipment in place during EVAs; and move Dextre around to perform tasks.^[159]
• Dextre is a 1,560 kg (3,440 lb) robotic manipulator that has two arms and a rotating torso, with power tools, lights, and video for replacing orbital replacement units (ORUs) and performing other tasks requiring fine control.^[160]
• The Mobile Base System (MBS) is a platform that rides on rails along the length of the station's main truss, which serves as a mobile base for Canadarm2 and Dextre, allowing the robotic arms to reach all parts of the USOS.^[161]

A grapple fixture was added to Zarya on STS-134 to enable Canadarm2 to inchworm itself onto the Russian Orbital Segment.^[162] Also installed during STS-134 was the 15 m (50 ft) Orbiter Boom Sensor System (OBSS), which had been used to inspect heat shield tiles on Space Shuttle missions and which can be used on the station to increase the reach of the MSS.^[162] Staff on Earth or the ISS can operate the MSS components using remote control, performing work outside the station without the need for space walks.

Japan's Remote Manipulator System, which services the Kibō Exposed Facility,^[163] was launched on STS-124 and is attached to the Kibō Pressurised Module.^[164] The arm is similar to the Space Shuttle arm as it is permanently attached at one end and has a latching end effector for standard grapple fixtures at the other.

The European Robotic Arm, which will service the Russian Orbital Segment, was launched alongside the Nauka module.^[165] The ROS does not require spacecraft or modules to be manipulated, as all spacecraft and modules dock automatically and may be discarded the same way. Crew use the two Strela (Russian: Стрела́, lit. 'Arrow') cargo cranes during EVAs for moving crew and equipment around the ROS. Each Strela crane has a mass of 45 kg (99 lb).

Former module

Pirs

Pirs was launched on 14 September 2001, as ISS Assembly Mission 4R, on a Russian Soyuz-U rocket, using a modified Progress spacecraft, Progress M-SO1, as an upper stage. Poisk was launched on 10 November 2009^[166][167] attached to a modified Progress spacecraft, called Progress M-MIM2, on a Soyuz-U rocket from Launch Pad 1 at the Baikonur Cosmodrome in Kazakhstan. Pirs was undocked by Progress MS-16 on 26 July, 2021, 10:56 UTC and deorbited on the same day at 14:51 UTC to make room for Nauka module to be attached to the space station.

Planned components

Prichal

Prichal, also known as Uzlovoy Module or UM (Russian: Узловой Модуль Причал, lit. 'Nodal Module Berth'),^[168] is a 4-tonne (8,800 lb)^[169] ball-shaped module that will allow docking of two scientific and power modules during the final stage of the station assembly, and provide the Russian segment additional docking ports to receive Soyuz MS and Progress MS spacecraft. UM is due to be launched in the third quarter of 2021.^[170] It will be integrated with a special version of the Progress cargo spacecraft and launched by a standard Soyuz rocket, docking to the nadir port of the Nauka module. One port is equipped with an active hybrid docking port, which enables docking with the MLM module. The remaining five ports are passive hybrids, enabling docking of Soyuz and Progress vehicles, as well as heavier modules and future spacecraft with modified docking systems. The node module was intended to serve as the only permanent element of the cancelled Orbital Piloted Assembly and Experiment Complex (OPSEK).^{[170][171][172]}

Axiom segment

In January 2020, NASA awarded Axiom Space a contract to build a commercial module for the ISS with a launch date of 2024. The contract is under the NextSTEP2 program. NASA negotiated with Axiom on a firm fixed-price contract basis to build and deliver the module, which will attach to the forward port of the space station's Harmony (Node 2) module. Although NASA has only commissioned one module, Axiom plans to build an entire segment consisting of five modules, including a node module, an orbital research and manufacturing facility, a crew habitat, and a "large-windowed Earth observatory". The Axiom segment is expected to greatly increase the capabilities and value of the space station, allowing for larger crews and private spaceflight by other organisations. Axiom plans to convert the segment into a stand-alone space station once the ISS is decommissioned, with the intention that this would act as a successor to the ISS.^{[173][174][175]} Canadarm 2 will also help to berth the Axiom Space Station modules to the ISS and will continue its operations on the Axiom Space Station after the retirement of ISS in late 2020s.^[176]

Proposed components

Xbase

Made by Bigelow Aerospace. In August 2016 Bigelow negotiated an agreement with NASA to develop a full-sized ground prototype Deep Space Habitation based on the B330 under the second phase of Next Space Technologies for Exploration Partnerships. The module is called the Expandable Bigelow Advanced Station Enhancement (XBASE), as Bigelow hopes to test the module by attaching it to the International Space Station.

Independence-1

Nanoracks, after finalizing its contract with NASA, and after winning NextSTEPs Phase II award, is now developing its concept Independence-1 (previously known as Ixion), which would turn spent rocket tanks into a habitable living area to be tested in space. In Spring 2018, Nanoracks announced that Ixion is now known as the Independence-1, the first 'outpost' in Nanoracks' Space Outpost Program.

Nautilus-X Centrifuge Demonstration

If produced, this centrifuge will be the first in-space demonstration of sufficient scale centrifuge for artificial partial-g effects. It will be designed to become a sleep module for the ISS crew.

Cancelled components

Several modules planned for the station were cancelled over the course of the ISS programme. Reasons include budgetary constraints, the modules becoming unnecessary, and station redesigns after the 2003 Columbia disaster. The US Centrifuge Accommodations Module would have hosted science experiments in varying levels of artificial gravity.^[177] The US Habitation Module would have served as the station's living quarters. Instead, the living quarters are now spread throughout the station.^[178] The US Interim Control Module and ISS Propulsion Module would have replaced the functions of Zvezda in case of a launch failure.^[179] Two Russian Research Modules were planned for scientific research.^[180] They would have docked to a Russian Universal Docking Module.^[181] The Russian Science Power Platform would have supplied power to the Russian Orbital Segment independent of the ITS solar arrays.

Science Power Modules 1 and 2 (Repurposed Components)

Science Power Module 1 (SPM-1, also known as NEM-1) and Science Power Module 2 (SPM-2, also known as NEM-2) are modules that were originally planned to arrive at the ISS no earlier than 2024, and dock to the Prichal module, which is planned to be attached to the Nauka module.^[172][182] In April 2021, Roscosmos announced that NEM-1 would be repurposed to function as the core module of the proposed Russian Orbital Service Station (ROSS), launching no earlier than 2025 and docking to the free-flying Nauka module either before or after the ISS has been deorbited.^[183][184] NEM-2 may be converted into another core "base" module, which would be launched in 2028.^[185]

Onboard systems

Life support

The critical systems are the atmosphere control system, the water supply system, the food supply facilities, the sanitation and hygiene equipment, and fire detection and suppression equipment. The Russian Orbital Segment's life support systems are contained in the Zvezda service module. Some of these systems are supplemented by equipment in the USOS. The Nauka laboratory has a complete set of life support systems.

Atmospheric control systems

The atmosphere on board the ISS is similar to that of Earth.^[186] Normal air pressure on the ISS is 101.3 kPa (14.69 psi);^[187] the same as at sea level on Earth. An Earth-like atmosphere offers benefits for crew comfort, and is much safer than a pure oxygen atmosphere, because of the increased risk of a fire such as that responsible for the deaths of the Apollo 1 crew.^[188] Earth-like atmospheric conditions have been maintained on all Russian and Soviet spacecraft.^[189]

The Elektron system aboard Zvezda and a similar system in Destiny generate oxygen aboard the station.^[190] The crew has a backup option in the form of bottled oxygen and Solid Fuel Oxygen Generation (SFOG) canisters, a chemical oxygen generator system.^[191] Carbon dioxide is removed from the air by the Vozdukh system in Zvezda. Other by-products of human metabolism, such as methane from the intestines and ammonia from sweat, are removed by activated charcoal filters.^[191]

Part of the ROS atmosphere control system is the oxygen supply. Triple-redundancy is provided by the Elektron unit, solid fuel generators, and stored oxygen. The primary supply of oxygen is the Elektron unit which produces O
2 and H
2 by electrolysis of water and vents H2 overboard. The 1 kW (1.3 hp) system uses approximately one litre of water per crew member per day. This water is either brought from Earth or recycled from other systems. Mir was the first spacecraft to use recycled water for oxygen production. The secondary oxygen supply is provided by burning O
2-producing Vika cartridges (see also ISS ECLSS). Each 'candle' takes 5–20 minutes to decompose at 450–500 °C (842–932 °F), producing 600 litres (130 imp gal; 160 US gal) of O
2. This unit is manually operated.^[192]

The US Orbital Segment has redundant supplies of oxygen, from a pressurised storage tank on the Quest airlock module delivered in 2001, supplemented ten years later by ESA-built Advanced Closed-Loop System (ACLS) in the Tranquility module (Node 3), which produces O
2 by electrolysis.^[193] Hydrogen produced is combined with carbon dioxide from the cabin atmosphere and converted to water and methane.

Power and thermal control

Double-sided solar arrays provide electrical power to the ISS. These bifacial cells collect direct sunlight on one side and light reflected off from the Earth on the other, and are more efficient and operate at a lower temperature than single-sided cells commonly used on Earth.^[194]

The Russian segment of the station, like most spacecraft, uses 28 V low voltage DC from two rotating solar arrays mounted on Zvezda. The USOS uses 130–180 V DC from the USOS PV array, power is stabilised and distributed at 160 V DC and converted to the user-required 124 V DC. The higher distribution voltage allows smaller, lighter conductors, at the expense of crew safety. The two station segments share power with converters.

The USOS solar arrays are arranged as four wing pairs, for a total production of 75 to 90 kilowatts.^[195] These arrays normally track the Sun to maximise power generation. Each array is about 375 m² (4,036 sq ft) in area and 58 m (190 ft) long. In the complete configuration, the solar arrays track the Sun by rotating the alpha gimbal once per orbit; the beta gimbal follows slower changes in the angle of the Sun to the orbital plane. The Night Glider mode aligns the solar arrays parallel to the ground at night to reduce the significant aerodynamic drag at the station's relatively low orbital altitude.^[196]

The station originally used rechargeable nickel–hydrogen batteries (NiH
2) for continuous power during the 45 minutes of every 90-minute orbit that it is eclipsed by the Earth. The batteries are recharged on the day side of the orbit. They had a 6.5-year lifetime (over 37,000 charge/discharge cycles) and were regularly replaced over the anticipated 20-year life of the station.^[197] Starting in 2016, the nickel–hydrogen batteries were replaced by lithium-ion batteries, which are expected to last until the end of the ISS program.^[198]

The station's large solar panels generate a high potential voltage difference between the station and the ionosphere. This could cause arcing through insulating surfaces and sputtering of conductive surfaces as ions are accelerated by the spacecraft plasma sheath. To mitigate this, plasma contactor units (PCU)s create current paths between the station and the ambient plasma field.^[199]

The station's systems and experiments consume a large amount of electrical power, almost all of which is converted to heat. To keep the internal temperature within workable limits, a passive thermal control system (PTCS) is made of external surface materials, insulation such as MLI, and heat pipes. If the PTCS cannot keep up with the heat load, an External Active Thermal Control System (EATCS) maintains the temperature. The EATCS consists of an internal, non-toxic, water coolant loop used to cool and dehumidify the atmosphere, which transfers collected heat into an external liquid ammonia loop. From the heat exchangers, ammonia is pumped into external radiators that emit heat as infrared radiation, then back to the station.^[200] The EATCS provides cooling for all the US pressurised modules, including Kibō and Columbus, as well as the main power distribution electronics of the S0, S1 and P1 trusses. It can reject up to 70 kW. This is much more than the 14 kW of the Early External Active Thermal Control System (EEATCS) via the Early Ammonia Servicer (EAS), which was launched on STS-105 and installed onto the P6 Truss.^[201]

Communications and computers

Radio communications provide telemetry and scientific data links between the station and mission control centres. Radio links are also used during rendezvous and docking procedures and for audio and video communication between crew members, flight controllers and family members. As a result, the ISS is equipped with internal and external communication systems used for different purposes.^[202]

The Russian Orbital Segment communicates directly with the ground via the Lira antenna mounted to Zvezda.^[7][203] The Lira antenna also has the capability to use the Luch data relay satellite system.^[7] This system fell into disrepair during the 1990s, and so was not used during the early years of the ISS,^{[7][204][205]} although two new Luch satellites—Luch-5A and Luch-5B—were launched in 2011 and 2012 respectively to restore the operational capability of the system.^[206] Another Russian communications system is the Voskhod-M, which enables internal telephone communications between Zvezda, Zarya, Pirs, Poisk, and the USOS and provides a VHF radio link to ground control centres via antennas on Zvezda's exterior.^[207]

The US Orbital Segment (USOS) makes use of two separate radio links mounted in the Z1 truss structure: the S band (audio) and K_u band (audio, video and data) systems. These transmissions are routed via the United States Tracking and Data Relay Satellite System (TDRSS) in geostationary orbit, allowing for almost continuous real-time communications with Christopher C. Kraft Jr. Mission Control Center (MCC-H) in Houston.^[7][25][202] Data channels for the Canadarm2, European Columbus laboratory and Japanese Kibō modules were originally also routed via the S band and K_u band systems, with the European Data Relay System and a similar Japanese system intended to eventually complement the TDRSS in this role.^[25][208] Communications between modules are carried on an internal wireless network.^[209]

UHF radio is used by astronauts and cosmonauts conducting EVAs and other spacecraft that dock to or undock from the station.^[7] Automated spacecraft are fitted with their own communications equipment; the ATV uses a laser attached to the spacecraft and the Proximity Communications Equipment attached to Zvezda to accurately dock with the station.^[210][211]

The ISS is equipped with about 100 IBM/Lenovo ThinkPad and HP ZBook 15 laptop computers. The laptops have run Windows 95, Windows 2000, Windows XP, Windows 7, Windows 10 and Linux operating systems.^[212] Each computer is a commercial off-the-shelf purchase which is then modified for safety and operation including updates to connectors, cooling and power to accommodate the station's 28V DC power system and weightless environment. Heat generated by the laptops does not rise but stagnates around the laptop, so additional forced ventilation is required. Laptops aboard the ISS are connected to the station's wireless LAN via Wi-Fi and ethernet, which connects to the ground via K_u band. While originally this provided speeds of 10 Mbit/s download and 3 Mbit/s upload from the station,^[213][214] NASA upgraded the system in late August 2019 and increased the speeds to 600 Mbit/s.^[215][216] Laptop hard drives occasionally fail and must be replaced.^[217] Other computer hardware failures include instances in 2001, 2007 and 2017; some of these failures have required EVAs to replace computer modules in externally mounted devices.^{[218][219][220][221]}

The operating system used for key station functions is the Debian Linux distribution.^[222] The migration from Microsoft Windows to Linux was made in May 2013 for reasons of reliability, stability and flexibility.^[223]

In 2017, an SG100 Cloud Computer was launched to the ISS as part of OA-7 mission.^[224] It was manufactured by NCSIST of Taiwan and designed in collaboration with Academia Sinica, and National Central University under contract for NASA.^[225]

Operations

Expeditions

Each permanent crew is given an expedition number. Expeditions run up to six months, from launch until undocking, an 'increment' covers the same time period, but includes cargo spacecraft and all activities. Expeditions 1 to 6 consisted of three-person crews. Expeditions 7 to 12 were reduced to the safe minimum of two following the destruction of the NASA Shuttle Columbia. From Expedition 13 the crew gradually increased to six around 2010.^[226][227] With the arrival of crew on US commercial vehicles beginning in 2020,^[228] NASA has indicated that expedition size may be increased to seven crew members, the number ISS was originally designed for.^[229][230]

Gennady Padalka, member of Expeditions 9, 19/20, 31/32, and 43/44, and Commander of Expedition 11, has spent more time in space than anyone else, a total of 878 days, 11 hours, and 29 minutes.^[231] Peggy Whitson has spent the most time in space of any American, totalling 665 days, 22 hours, and 22 minutes during her time on Expeditions 5, 16, and 50/51/52.^[232]

Private flights

Travellers who pay for their own passage into space are termed spaceflight participants by Roscosmos and NASA, and are sometimes referred to as "space tourists", a term they generally dislike.^[b] All seven were transported to the ISS on Russian Soyuz spacecraft. When professional crews change over in numbers not divisible by the three seats in a Soyuz, and a short-stay crewmember is not sent, the spare seat is sold by MirCorp through Space Adventures. When the Space Shuttle was retired in 2011, and the station's crew size was reduced to six, space tourism was halted, as the partners relied on Russian transport seats for access to the station. Soyuz flight schedules increase after 2013, allowing five Soyuz flights (15 seats) with only two expeditions (12 seats) required.^[240] The remaining seats are sold for around US$40 million to members of the public who can pass a medical exam. ESA and NASA criticised private spaceflight at the beginning of the ISS, and NASA initially resisted training Dennis Tito, the first person to pay for his own passage to the ISS.^[c]

Anousheh Ansari became the first Iranian in space and the first self-funded woman to fly to the station. Officials reported that her education and experience make her much more than a tourist, and her performance in training had been "excellent."^[241] Ansari herself dismisses the idea that she is a tourist. She did Russian and European studies involving medicine and microbiology during her 10-day stay. The 2009 documentary Space Tourists follows her journey to the station, where she fulfilled "an age-old dream of man: to leave our planet as a "normal person" and travel into outer space."^[242]

In 2008, spaceflight participant Richard Garriott placed a geocache aboard the ISS during his flight.^[243] This is currently the only non-terrestrial geocache in existence.^[244] At the same time, the Immortality Drive, an electronic record of eight digitised human DNA sequences, was placed aboard the ISS.^[245]

Fleet operations

A wide variety of crewed and uncrewed spacecraft have supported the station's activities. Flights to the ISS include 37 Space Shuttle missions, 75 Progress resupply spacecraft (including the modified M-MIM2 and M-SO1 module transports), 59 crewed Soyuz spacecraft, 5 European ATVs, 9 Japanese HTVs, 22 SpaceX Dragon and 16 Cygnus missions.^[246]

There are currently 9 available docking ports for visiting spacecrafts:^[247][248]

1. Harmony forward (with PMA 2 / IDA 2)
2. Harmony zenith (with PMA 3 / IDA 3)
3. Harmony nadir
4. Unity nadir
5. Nauka nadir^[249]
6. Nauka forward^[250]
7. Poisk zenith
8. Rassvet nadir
9. Zvezda aft

Crewed

As of 2 August 2021^[ref], 244 people from 19 countries had visited the space station, many of them multiple times. The United States sent 153 people, Russia sent 50, nine were Japanese, eight were Canadian, five were Italian, four were French, three were German, and there were one each from Belgium, Brazil, Denmark, Great Britain, Kazakhstan, Malaysia, the Netherlands, South Africa, South Korea, Spain, Sweden and the United Arab Emirates.^[251]

Uncrewed

Uncrewed spaceflights to the International Space Station (ISS) are made primarily to deliver cargo, however several Russian modules have also docked to the outpost following uncrewed launches. Resupply missions typically used the Russian Progress spacecraft, European ATVs, Japanese Kounotori vehicles, and the American Dragon and Cygnus spacecraft. The primary docking system for Progress spacecraft is the automated Kurs system, with the manual TORU system as a backup. ATVs also use Kurs, however they are not equipped with TORU. Progress and ATV can remain docked for up to six months.^[252][253] The other spacecraft — the Japanese HTV, the SpaceX Dragon (under CRS phase 1) and the Northrop Grumman^[254] Cygnus — rendezvous with the station before being grappled using Canadarm2 and berthed at the nadir port of the Harmony or Unity module for one to two months. Under CRS phase 2, Cargo Dragon docks autonomously at IDA-2 or 3 as the case may be. As of December 2020, Progress spacecraft have flown most of the uncrewed missions to the ISS.

Currently docked/berthed

Key

Spacecraft and mission			Location	Arrival (UTC)	Departure (planned)
	Soyuz MS Yu.A.Gagarin	Soyuz MS-18	Rassvet nadir	9 April 2021[255][256]	13 October 2021
	Crew Dragon Endeavour	Crew-2	Harmony zenith	24 April 2021[257]	October 2021
	Progress MS No. 446	Progress MS-17	Poisk zenith	2 July 2021[255][256]	24 November 2021
	Nauka passive docking adapter[d]	Nauka	Nauka nadir	29 July 2021	24 November 2021
	S.S. Ellison Onizuka	NG-16	Unity nadir	12 August 2021	November 2021

Scheduled missions

• All dates are UTC. Dates are the earliest possible dates and may change.
• Forward ports are at the front of the station according to its normal direction of travel and orientation (attitude). Aft is at the rear of the station, used by spacecraft boosting the station's orbit. Nadir is closest the Earth, Zenith is on top. Port is to the left if pointing one's feet towards the Earth and looking in the direction of travel; starboard to the right.^[258]

Key

Docking

All Russian spacecraft and self-propelled modules are able to rendezvous and dock to the space station without human intervention using the Kurs radar docking system from over 200 kilometres away. The European ATV uses star sensors and GPS to determine its intercept course. When it catches up it uses laser equipment to optically recognise Zvezda, along with the Kurs system for redundancy. Crew supervise these craft, but do not intervene except to send abort commands in emergencies. Progress and ATV supply craft can remain at the ISS for six months,^[264][265] allowing great flexibility in crew time for loading and unloading of supplies and trash.

From the initial station programs, the Russians pursued an automated docking methodology that used the crew in override or monitoring roles. Although the initial development costs were high, the system has become very reliable with standardisations that provide significant cost benefits in repetitive operations.^[266]

Soyuz spacecraft used for crew rotation also serve as lifeboats for emergency evacuation; they are replaced every six months and were used after the Columbia disaster to return stranded crew from the ISS.^[267] Expeditions require, on average, 2,722 kg of supplies, and as of 9 March 2011^[update], crews had consumed a total of around 22,000 meals.^[85] Soyuz crew rotation flights and Progress resupply flights visit the station on average two and three times respectively each year.^[268]

Other vehicles berth instead of docking. The Japanese H-II Transfer Vehicle parked itself in progressively closer orbits to the station, and then awaited 'approach' commands from the crew, until it was close enough for a robotic arm to grapple and berth the vehicle to the USOS. Berthed craft can transfer International Standard Payload Racks. Japanese spacecraft berth for one to two months.^[269] The berthing Cygnus and SpaceX Dragon were contracted to fly cargo to the station under the phase 1 of the Commercial Resupply Services program.^[270][271]

From 26 February 2011 to 7 March 2011 four of the governmental partners (United States, ESA, Japan and Russia) had their spacecraft (NASA Shuttle, ATV, HTV, Progress and Soyuz) docked at the ISS, the only time this has happened to date.^[272] On 25 May 2012, SpaceX delivered the first commercial cargo with a Dragon spacecraft.^[273]

Launch and docking windows

Prior to a spacecraft's docking to the ISS, navigation and attitude control (GNC) is handed over to the ground control of the spacecraft's country of origin. GNC is set to allow the station to drift in space, rather than fire its thrusters or turn using gyroscopes. The solar panels of the station are turned edge-on to the incoming spacecraft, so residue from its thrusters does not damage the cells. Before its retirement, Shuttle launches were often given priority over Soyuz, with occasional priority given to Soyuz arrivals carrying crew and time-critical cargoes, such as biological experiment materials.^[274]

Repairs

Orbital Replacement Units (ORUs) are spare parts that can be readily replaced when a unit either passes its design life or fails. Examples of ORUs are pumps, storage tanks, controller boxes, antennas, and battery units. Some units can be replaced using robotic arms. Most are stored outside the station, either on small pallets called ExPRESS Logistics Carriers (ELCs) or share larger platforms called External Stowage Platforms which also hold science experiments. Both kinds of pallets provide electricity for many parts that could be damaged by the cold of space and require heating. The larger logistics carriers also have local area network (LAN) connections for telemetry to connect experiments. A heavy emphasis on stocking the USOS with ORU's occurred around 2011, before the end of the NASA shuttle programme, as its commercial replacements, Cygnus and Dragon, carry one tenth to one quarter the payload.

Unexpected problems and failures have impacted the station's assembly time-line and work schedules leading to periods of reduced capabilities and, in some cases, could have forced abandonment of the station for safety reasons. Serious problems include an air leak from the USOS in 2004,^[275] the venting of fumes from an Elektron oxygen generator in 2006,^[276] and the failure of the computers in the ROS in 2007 during STS-117 that left the station without thruster, Elektron, Vozdukh and other environmental control system operations. In the latter case, the root cause was found to be condensation inside electrical connectors leading to a short circuit.^[277]

During STS-120 in 2007 and following the relocation of the P6 truss and solar arrays, it was noted during unfurling that the solar array had torn and was not deploying properly.^[278] An EVA was carried out by Scott Parazynski, assisted by Douglas Wheelock. Extra precautions were taken to reduce the risk of electric shock, as the repairs were carried out with the solar array exposed to sunlight.^[279] The issues with the array were followed in the same year by problems with the starboard Solar Alpha Rotary Joint (SARJ), which rotates the arrays on the starboard side of the station. Excessive vibration and high-current spikes in the array drive motor were noted, resulting in a decision to substantially curtail motion of the starboard SARJ until the cause was understood. Inspections during EVAs on STS-120 and STS-123 showed extensive contamination from metallic shavings and debris in the large drive gear and confirmed damage to the large metallic bearing surfaces, so the joint was locked to prevent further damage.^[280][281] Repairs to the joints were carried out during STS-126 with lubrication and the replacement of 11 out of 12 trundle bearings on the joint.^[282][283]

In September 2008, damage to the S1 radiator was first noticed in Soyuz imagery. The problem was initially not thought to be serious.^[284] The imagery showed that the surface of one sub-panel has peeled back from the underlying central structure, possibly because of micro-meteoroid or debris impact. On 15 May 2009 the damaged radiator panel's ammonia tubing was mechanically shut off from the rest of the cooling system by the computer-controlled closure of a valve. The same valve was then used to vent the ammonia from the damaged panel, eliminating the possibility of an ammonia leak.^[284] It is also known that a Service Module thruster cover struck the S1 radiator after being jettisoned during an EVA in 2008, but its effect, if any, has not been determined.

In the early hours of 1 August 2010, a failure in cooling Loop A (starboard side), one of two external cooling loops, left the station with only half of its normal cooling capacity and zero redundancy in some systems.^{[285][286][287]} The problem appeared to be in the ammonia pump module that circulates the ammonia cooling fluid. Several subsystems, including two of the four CMGs, were shut down.

Planned operations on the ISS were interrupted through a series of EVAs to address the cooling system issue. A first EVA on 7 August 2010, to replace the failed pump module, was not fully completed because of an ammonia leak in one of four quick-disconnects. A second EVA on 11 August successfully removed the failed pump module.^[288][289] A third EVA was required to restore Loop A to normal functionality.^[290][291]

The USOS's cooling system is largely built by the US company Boeing,^[292] which is also the manufacturer of the failed pump.^[285]

The four Main Bus Switching Units (MBSUs, located in the S0 truss), control the routing of power from the four solar array wings to the rest of the ISS. Each MBSU has two power channels that feed 160V DC from the arrays to two DC-to-DC power converters (DDCUs) that supply the 124V power used in the station. In late 2011 MBSU-1 ceased responding to commands or sending data confirming its health. While still routing power correctly, it was scheduled to be swapped out at the next available EVA. A spare MBSU was already on board, but a 30 August 2012 EVA failed to be completed when a bolt being tightened to finish installation of the spare unit jammed before the electrical connection was secured.^[293] The loss of MBSU-1 limited the station to 75% of its normal power capacity, requiring minor limitations in normal operations until the problem could be addressed.

On 5 September 2012, in a second six-hour EVA, astronauts Sunita Williams and Akihiko Hoshide successfully replaced MBSU-1 and restored the ISS to 100% power.^[294]

On 24 December 2013, astronauts installed a new ammonia pump for the station's cooling system. The faulty cooling system had failed earlier in the month, halting many of the station's science experiments. Astronauts had to brave a "mini blizzard" of ammonia while installing the new pump. It was only the second Christmas Eve spacewalk in NASA history.^[295]

Mission control centres

The components of the ISS are operated and monitored by their respective space agencies at mission control centres across the globe, including RKA Mission Control Center, ATV Control Centre, JEM Control Center and HTV Control Center at Tsukuba Space Center, Christopher C. Kraft Jr. Mission Control Center, Payload Operations and Integration Center, Columbus Control Center and Mobile Servicing System Control.

Life aboard

Crew activities

A typical day for the crew begins with a wake-up at 06:00, followed by post-sleep activities and a morning inspection of the station. The crew then eats breakfast and takes part in a daily planning conference with Mission Control before starting work at around 08:10. The first scheduled exercise of the day follows, after which the crew continues work until 13:05. Following a one-hour lunch break, the afternoon consists of more exercise and work before the crew carries out its pre-sleep activities beginning at 19:30, including dinner and a crew conference. The scheduled sleep period begins at 21:30. In general, the crew works ten hours per day on a weekday, and five hours on Saturdays, with the rest of the time their own for relaxation or work catch-up.^[296]

The time zone used aboard the ISS is Coordinated Universal Time (UTC).^[297] The windows are covered during night hours to give the impression of darkness because the station experiences 16 sunrises and sunsets per day. During visiting Space Shuttle missions, the ISS crew mostly follows the shuttle's Mission Elapsed Time (MET), which is a flexible time zone based on the launch time of the Space Shuttle mission.^{[298][299][300]}

The station provides crew quarters for each member of the expedition's crew, with two "sleep stations" in the Zvezda, one in Nauka and four more installed in Harmony.^{[301][302][303][304]} The USOS quarters are private, approximately person-sized soundproof booths. The ROS crew quarters in Zvezda include a small window, but provide less ventilation and sound proofing. A crew member can sleep in a crew quarter in a tethered sleeping bag, listen to music, use a laptop, and store personal items in a large drawer or in nets attached to the module's walls. The module also provides a reading lamp, a shelf and a desktop.^{[305][306][307]} Visiting crews have no allocated sleep module, and attach a sleeping bag to an available space on a wall. It is possible to sleep floating freely through the station, but this is generally avoided because of the possibility of bumping into sensitive equipment.^[308] It is important that crew accommodations be well ventilated; otherwise, astronauts can wake up oxygen-deprived and gasping for air, because a bubble of their own exhaled carbon dioxide has formed around their heads.^[305] During various station activities and crew rest times, the lights in the ISS can be dimmed, switched off, and colour temperatures adjusted.^[309][310]

Food and personal hygiene

On the USOS, most of the food aboard is vacuum sealed in plastic bags; cans are rare because they are heavy and expensive to transport. Preserved food is not highly regarded by the crew and taste is reduced in microgravity,^[305] so efforts are taken to make the food more palatable, including using more spices than in regular cooking. The crew looks forward to the arrival of any spacecraft from Earth as they bring fresh fruit and vegetables. Care is taken that foods do not create crumbs, and liquid condiments are preferred over solid to avoid contaminating station equipment. Each crew member has individual food packages and cooks them using the on-board galley. The galley features two food warmers, a refrigerator (added in November 2008), and a water dispenser that provides both heated and unheated water.^[306] Drinks are provided as dehydrated powder that is mixed with water before consumption.^[306][307] Drinks and soups are sipped from plastic bags with straws, while solid food is eaten with a knife and fork attached to a tray with magnets to prevent them from floating away. Any food that floats away, including crumbs, must be collected to prevent it from clogging the station's air filters and other equipment.^[307]

Showers on space stations were introduced in the early 1970s on Skylab and Salyut 3.^[311]:139 By Salyut 6, in the early 1980s, the crew complained of the complexity of showering in space, which was a monthly activity.^[312] The ISS does not feature a shower; instead, crewmembers wash using a water jet and wet wipes, with soap dispensed from a toothpaste tube-like container. Crews are also provided with rinseless shampoo and edible toothpaste to save water.^[308][313]

There are two space toilets on the ISS, both of Russian design, located in Zvezda and Tranquility.^[306] These Waste and Hygiene Compartments use a fan-driven suction system similar to the Space Shuttle Waste Collection System. Astronauts first fasten themselves to the toilet seat, which is equipped with spring-loaded restraining bars to ensure a good seal.^[305] A lever operates a powerful fan and a suction hole slides open: the air stream carries the waste away. Solid waste is collected in individual bags which are stored in an aluminium container. Full containers are transferred to Progress spacecraft for disposal.^[306][314] Liquid waste is evacuated by a hose connected to the front of the toilet, with anatomically correct "urine funnel adapters" attached to the tube so that men and women can use the same toilet. The diverted urine is collected and transferred to the Water Recovery System, where it is recycled into drinking water.^[307]

Crew health and safety

Overall

On 12 April 2019, NASA reported medical results from the Astronaut Twin Study. Astronaut Scott Kelly spent a year in space on the ISS, while his twin spent the year on Earth. Several long-lasting changes were observed, including those related to alterations in DNA and cognition, when one twin was compared with the other.^[315][316]

In November 2019, researchers reported that astronauts experienced serious blood flow and clot problems while on board the ISS, based on a six-month study of 11 healthy astronauts. The results may influence long-term spaceflight, including a mission to the planet Mars, according to the researchers.^[317][318]

Radiation

The ISS is partially protected from the space environment by Earth's magnetic field. From an average distance of about 70,000 km (43,000 mi) from the Earth's surface, depending on Solar activity, the magnetosphere begins to deflect solar wind around Earth and the space station. Solar flares are still a hazard to the crew, who may receive only a few minutes warning. In 2005, during the initial "proton storm" of an X-3 class solar flare, the crew of Expedition 10 took shelter in a more heavily shielded part of the ROS designed for this purpose.^[319][320]

Subatomic charged particles, primarily protons from cosmic rays and solar wind, are normally absorbed by Earth's atmosphere. When they interact in sufficient quantity, their effect is visible to the naked eye in a phenomenon called an aurora. Outside Earth's atmosphere, ISS crews are exposed to approximately one millisievert each day (about a year's worth of natural exposure on Earth), resulting in a higher risk of cancer. Radiation can penetrate living tissue and damage the DNA and chromosomes of lymphocytes; being central to the immune system, any damage to these cells could contribute to the lower immunity experienced by astronauts. Radiation has also been linked to a higher incidence of cataracts in astronauts. Protective shielding and medications may lower the risks to an acceptable level.^[47]

Radiation levels on the ISS are about five times greater than those experienced by airline passengers and crew, as Earth's electromagnetic field provides almost the same level of protection against solar and other types of radiation in low Earth orbit as in the stratosphere. For example, on a 12-hour flight, an airline passenger would experience 0.1 millisieverts of radiation, or a rate of 0.2 millisieverts per day; this is only one fifth the rate experienced by an astronaut in LEO. Additionally, airline passengers experience this level of radiation for a few hours of flight, while the ISS crew are exposed for their whole stay on board the station.^[321]

Stress

There is considerable evidence that psychosocial stressors are among the most important impediments to optimal crew morale and performance.^[322] Cosmonaut Valery Ryumin wrote in his journal during a particularly difficult period on board the Salyut 6 space station: "All the conditions necessary for murder are met if you shut two men in a cabin measuring 18 feet by 20 and leave them together for two months."

NASA's interest in psychological stress caused by space travel, initially studied when their crewed missions began, was rekindled when astronauts joined cosmonauts on the Russian space station Mir. Common sources of stress in early US missions included maintaining high performance under public scrutiny and isolation from peers and family. The latter is still often a cause of stress on the ISS, such as when the mother of NASA astronaut Daniel Tani died in a car accident, and when Michael Fincke was forced to miss the birth of his second child.

A study of the longest spaceflight concluded that the first three weeks are a critical period where attention is adversely affected because of the demand to adjust to the extreme change of environment.^[323] ISS crew flights typically last about five to six months.

The ISS working environment includes further stress caused by living and working in cramped conditions with people from very different cultures who speak a different language. First-generation space stations had crews who spoke a single language; second- and third-generation stations have crew from many cultures who speak many languages. Astronauts must speak English and Russian, and knowing additional languages is even better.^[324]

Due to the lack of gravity, confusion often occurs. Even though there is no up and down in space, some crew members feel like they are oriented upside down. They may also have difficulty measuring distances. This can cause problems like getting lost inside the space station, pulling switches in the wrong direction or misjudging the speed of an approaching vehicle during docking.^[325]

Medical

The physiological effects of long-term weightlessness include muscle atrophy, deterioration of the skeleton (osteopenia), fluid redistribution, a slowing of the cardiovascular system, decreased production of red blood cells, balance disorders, and a weakening of the immune system. Lesser symptoms include loss of body mass, and puffiness of the face.^[47]

Sleep is regularly disturbed on the ISS because of mission demands, such as incoming or departing spacecraft. Sound levels in the station are unavoidably high. The atmosphere is unable to thermosiphon naturally, so fans are required at all times to process the air which would stagnate in the freefall (zero-G) environment.

To prevent some of the adverse effects on the body, the station is equipped with: two TVIS treadmills (including the COLBERT); the ARED (Advanced Resistive Exercise Device), which enables various weightlifting exercises that add muscle without raising (or compensating for) the astronauts' reduced bone density;^[326] and a stationary bicycle. Each astronaut spends at least two hours per day exercising on the equipment.^[305][306] Astronauts use bungee cords to strap themselves to the treadmill.^[327][328]

Microbiological environmental hazards

Hazardous moulds that can foul air and water filters may develop aboard space stations. They can produce acids that degrade metal, glass, and rubber. They can also be harmful to the crew's health. Microbiological hazards have led to a development of the LOCAD-PTS which identifies common bacteria and moulds faster than standard methods of culturing, which may require a sample to be sent back to Earth.^[329] Researchers in 2018 reported, after detecting the presence of five Enterobacter bugandensis bacterial strains on the ISS (none of which are pathogenic to humans), that microorganisms on the ISS should be carefully monitored to continue assuring a medically healthy environment for astronauts.^[330][331]

Contamination on space stations can be prevented by reduced humidity, and by using paint that contains mould-killing chemicals, as well as the use of antiseptic solutions. All materials used in the ISS are tested for resistance against fungi.^[332]

In April 2019, NASA reported that a comprehensive study had been conducted into the microorganisms and fungi present on the ISS. The results may be useful in improving the health and safety conditions for astronauts.^[333][334]

Noise

Space flight is not inherently quiet, with noise levels exceeding acoustic standards as far back as the Apollo missions.^[335][336] For this reason, NASA and the International Space Station international partners have developed noise control and hearing loss prevention goals as part of the health program for crew members. Specifically, these goals have been the primary focus of the ISS Multilateral Medical Operations Panel (MMOP) Acoustics Subgroup since the first days of ISS assembly and operations.^[337][338] The effort includes contributions from acoustical engineers, audiologists, industrial hygienists, and physicians who comprise the subgroup's membership from NASA, the Russian Space Agency (RSA), the European Space Agency (ESA), the Japanese Aerospace Exploration Agency (JAXA), and the Canadian Space Agency (CSA).

When compared to terrestrial environments, the noise levels incurred by astronauts and cosmonauts on the ISS may seem insignificant and typically occur at levels that would not be of major concern to the Occupational Safety and Health Administration – rarely reaching 85 dBA. But crew members are exposed to these levels 24 hours a day, seven days a week, with current missions averaging six months in duration. These levels of noise also impose risks to crew health and performance in the form of sleep interference and communication, as well as reduced alarm audibility.

Over the 19 plus year history of the ISS, significant efforts have been put forth to limit and reduce noise levels on the ISS. During design and pre-flight activities, members of the Acoustic Subgroup have written acoustic limits and verification requirements, consulted to design and choose quietest available payloads, and then conducted acoustic verification tests prior to launch.^[337]:5.7.3 During spaceflights, the Acoustics Subgroup has assessed each ISS module's in flight sound levels, produced by a large number of vehicle and science experiment noise sources, to assure compliance with strict acoustic standards. The acoustic environment on ISS changed when additional modules were added during its construction, and as additional spacecraft arrive at the ISS. The Acoustics Subgroup has responded to this dynamic operations schedule by successfully designing and employing acoustic covers, absorptive materials, noise barriers, and vibration isolators to reduce noise levels. Moreover, when pumps, fans, and ventilation systems age and show increased noise levels, this Acoustics Subgroup has guided ISS managers to replace the older, noisier instruments with quiet fan and pump technologies, significantly reducing ambient noise levels.

NASA has adopted most-conservative damage risk criteria (based on recommendations from the National Institute for Occupational Safety and Health and the World Health Organization), in order to protect all crew members. The MMOP Acoustics Subgroup has adjusted its approach to managing noise risks in this unique environment by applying, or modifying, terrestrial approaches for hearing loss prevention to set these conservative limits. One innovative approach has been NASA's Noise Exposure Estimation Tool (NEET), in which noise exposures are calculated in a task-based approach to determine the need for hearing protection devices (HPDs). Guidance for use of HPDs, either mandatory use or recommended, is then documented in the Noise Hazard Inventory, and posted for crew reference during their missions. The Acoustics Subgroup also tracks spacecraft noise exceedances, applies engineering controls, and recommends hearing protective devices to reduce crew noise exposures. Finally, hearing thresholds are monitored on-orbit, during missions.

There have been no persistent mission-related hearing threshold shifts among US Orbital Segment crewmembers (JAXA, CSA, ESA, NASA) during what is approaching 20 years of ISS mission operations, or nearly 175,000 work hours. In 2020, the MMOP Acoustics Subgroup received the Safe-In-Sound Award for Innovation for their combined efforts to mitigate any health effects of noise.^[339]

Fire and toxic gases

An onboard fire or a toxic gas leak are other potential hazards. Ammonia is used in the external radiators of the station and could potentially leak into the pressurised modules.^[340]

Orbit

Altitude and orbital inclination

The ISS is currently maintained in a nearly circular orbit with a minimum mean altitude of 370 km (230 mi) and a maximum of 460 km (290 mi),^[341] in the centre of the thermosphere, at an inclination of 51.6 degrees to Earth's equator. This orbit was selected because it is the lowest inclination that can be directly reached by Russian Soyuz and Progress spacecraft launched from Baikonur Cosmodrome at 46° N latitude without overflying China or dropping spent rocket stages in inhabited areas.^[342][343] It travels at an average speed of 28,000 kilometres per hour (17,000 mph), and completes 15.5 orbits per day (93 minutes per orbit).^[2][18] The station's altitude was allowed to fall around the time of each NASA shuttle flight to permit heavier loads to be transferred to the station. After the retirement of the shuttle, the nominal orbit of the space station was raised in altitude (from about 350 km to about 400 km).^[344][345] Other, more frequent supply spacecraft do not require this adjustment as they are substantially higher performance vehicles.^[32][346]

Atmospheric drag reduces the altitude by about 2 km a month on average. Orbital boosting can be performed by the station's two main engines on the Zvezda service module, or Russian or European spacecraft docked to Zvezda's aft port. The Automated Transfer Vehicle is constructed with the possibility of adding a second docking port to its aft end, allowing other craft to dock and boost the station. It takes approximately two orbits (three hours) for the boost to a higher altitude to be completed.^[346] Maintaining ISS altitude uses about 7.5 tonnes of chemical fuel per annum^[347] at an annual cost of about $210 million.^[348]

The Russian Orbital Segment contains the Data Management System, which handles Guidance, Navigation and Control (ROS GNC) for the entire station.^[349] Initially, Zarya, the first module of the station, controlled the station until a short time after the Russian service module Zvezda docked and was transferred control. Zvezda contains the ESA built DMS-R Data Management System.^[350] Using two fault-tolerant computers (FTC), Zvezda computes the station's position and orbital trajectory using redundant Earth horizon sensors, Solar horizon sensors as well as Sun and star trackers. The FTCs each contain three identical processing units working in parallel and provide advanced fault-masking by majority voting.

Orientation

Zvezda uses gyroscopes (reaction wheels) and thrusters to turn itself around. Gyroscopes do not require propellant; instead they use electricity to 'store' momentum in flywheels by turning in the opposite direction to the station's movement. The USOS has its own computer-controlled gyroscopes to handle its extra mass. When gyroscopes 'saturate', thrusters are used to cancel out the stored momentum. In February 2005, during Expedition 10, an incorrect command was sent to the station's computer, using about 14 kilograms of propellant before the fault was noticed and fixed. When attitude control computers in the ROS and USOS fail to communicate properly, this can result in a rare 'force fight' where the ROS GNC computer must ignore the USOS counterpart, which itself has no thrusters.^{[351][352][353]}

Docked spacecraft can also be used to maintain station attitude, such as for troubleshooting or during the installation of the S3/S4 truss, which provides electrical power and data interfaces for the station's electronics.^[354]

Orbital debris threats

The low altitudes at which the ISS orbits are also home to a variety of space debris,^[355] including spent rocket stages, defunct satellites, explosion fragments (including materials from anti-satellite weapon tests), paint flakes, slag from solid rocket motors, and coolant released by US-A nuclear-powered satellites. These objects, in addition to natural micrometeoroids,^[356] are a significant threat. Objects large enough to destroy the station can be tracked, and are not as dangerous as smaller debris.^[357][358] Objects too small to be detected by optical and radar instruments, from approximately 1 cm down to microscopic size, number in the trillions. Despite their small size, some of these objects are a threat because of their kinetic energy and direction in relation to the station. Spacewalking crew in spacesuits are also at risk of suit damage and consequent exposure to vacuum.^[359]

Ballistic panels, also called micrometeorite shielding, are incorporated into the station to protect pressurised sections and critical systems. The type and thickness of these panels depend on their predicted exposure to damage. The station's shields and structure have different designs on the ROS and the USOS. On the USOS, Whipple Shields are used. The US segment modules consist of an inner layer made from 1.5–5.0 cm-thick (0.59–1.97 in) aluminium, a 10 cm-thick (3.9 in) intermediate layers of Kevlar and Nextel,^[360] and an outer layer of stainless steel, which causes objects to shatter into a cloud before hitting the hull, thereby spreading the energy of impact. On the ROS, a carbon fibre reinforced polymer honeycomb screen is spaced from the hull, an aluminium honeycomb screen is spaced from that, with a screen-vacuum thermal insulation covering, and glass cloth over the top.^[361]

Space debris is tracked remotely from the ground, and the station crew can be notified.^[362] If necessary, thrusters on the Russian Orbital Segment can alter the station's orbital altitude, avoiding the debris. These Debris Avoidance Manoeuvres (DAMs) are not uncommon, taking place if computational models show the debris will approach within a certain threat distance. Ten DAMs had been performed by the end of 2009.^{[363][364][365]} Usually, an increase in orbital velocity of the order of 1 m/s is used to raise the orbit by one or two kilometres. If necessary, the altitude can also be lowered, although such a manoeuvre wastes propellant.^[364][366] If a threat from orbital debris is identified too late for a DAM to be safely conducted, the station crew close all the hatches aboard the station and retreat into their Soyuz spacecraft in order to be able to evacuate in the event the station was seriously damaged by the debris. This partial station evacuation has occurred on 13 March 2009, 28 June 2011, 24 March 2012 and 16 June 2015.^[367][368]

• 

  A 7-gram object (shown in centre) shot at 7 km/s (23,000 ft/s), the orbital velocity of the ISS, made this 15 cm (5.9 in) crater in a solid block of aluminium.

• 

  Radar-trackable objects, including debris, with distinct ring of geostationary satellites

• 

  Example of risk management: A NASA model showing areas at high risk from impact for the International Space Station.

Sightings from Earth

Naked-eye visibility

The ISS is visible to the naked eye as a slow-moving, bright white dot because of reflected sunlight, and can be seen in the hours after sunset and before sunrise, when the station remains sunlit but the ground and sky are dark.^[369] The ISS takes about 10 minutes to pass from one horizon to another, and will only be visible part of that time because of moving into or out of the Earth's shadow. Because of the size of its reflective surface area, the ISS is the brightest artificial object in the sky (excluding other satellite flares), with an approximate maximum magnitude of −4 when overhead (similar to Venus). The ISS, like many satellites including the Iridium constellation, can also produce flares of up to 16 times the brightness of Venus as sunlight glints off reflective surfaces.^[370][371] The ISS is also visible in broad daylight, albeit with a great deal more difficulty.

Tools are provided by a number of websites such as Heavens-Above (see Live viewing below) as well as smartphone applications that use orbital data and the observer's longitude and latitude to indicate when the ISS will be visible (weather permitting), where the station will appear to rise, the altitude above the horizon it will reach and the duration of the pass before the station disappears either by setting below the horizon or entering into Earth's shadow.^{[372][373][374][375]}

In November 2012 NASA launched its "Spot the Station" service, which sends people text and email alerts when the station is due to fly above their town.^[376] The station is visible from 95% of the inhabited land on Earth, but is not visible from extreme northern or southern latitudes.^[342]

Under specific conditions, the ISS can be observed at night on five consecutive orbits. Those conditions are 1) a mid-latitude observer location, 2) near the time of the solstice with 3) the ISS passing in the direction of the pole from the observer near midnight local time. The three photos show the first, middle and last of the five passes on June 5/6, 2014.

• 

  Skytrack long duration exposure of the ISS

• 

  The ISS on its first pass of the night passing nearly overhead shortly after sunset in June 2014

• 

  The ISS passing north on its third pass of the night near local midnight in June 2014

• 

  The ISS passing west on its fifth pass of the night before sunrise in June 2014

Astrophotography

Using a telescope-mounted camera to photograph the station is a popular hobby for astronomers,^[377] while using a mounted camera to photograph the Earth and stars is a popular hobby for crew.^[378] The use of a telescope or binoculars allows viewing of the ISS during daylight hours.^[379]

Some amateur astronomers also use telescopic lenses to photograph the ISS while it transits the Sun, sometimes doing so during an eclipse (and so the Sun, Moon, and ISS are all positioned approximately in a single line). One example is during the 21 August solar eclipse, where at one location in Wyoming, images of the ISS were captured during the eclipse.^[380] Similar images were captured by NASA from a location in Washington.

Parisian engineer and astrophotographer Thierry Legault, known for his photos of spaceships transiting the Sun, travelled to Oman in 2011 to photograph the Sun, Moon and space station all lined up.^[381] Legault, who received the Marius Jacquemetton award from the Société astronomique de France in 1999, and other hobbyists, use websites that predict when the ISS will transit the Sun or Moon and from what location those passes will be visible.

International co-operation

Involving five space programs and fifteen countries,^[382] the International Space Station is the most politically and legally complex space exploration programme in history.^[383] The 1998 Space Station Intergovernmental Agreement sets forth the primary framework for international cooperation among the parties. A series of subsequent agreements govern other aspects of the station, ranging from jurisdictional issues to a code of conduct among visiting astronauts.^[384]

Participating countries

•  Brazil (1997–2007)
•  Canada
• European Space Agency
  •  Belgium
  •  Denmark
  •  France
  •  Germany
  •  Italy
  •  Netherlands
  •  Norway
  •  Spain
  •  Sweden
  •   Switzerland
  •  United Kingdom
•  Japan
•  Russia
•  United States

End of mission

According to the Outer Space Treaty, the United States and Russia are legally responsible for all modules they have launched.^[385] Several possible disposal options were considered: Natural orbital decay with random reentry (as with Skylab), boosting the station to a higher altitude (which would delay reentry), and a controlled targeted de-orbit to a remote ocean area.^[386] As of late 2010, the preferred plan is to use a slightly modified Progress spacecraft to de-orbit the ISS.^[387] This plan was seen as the simplest, cheapest and with the highest margin.^[387]

OPSEK was previously intended to be constructed of modules from the Russian Orbital Segment after the ISS is decommissioned. The modules under consideration for removal from the current ISS included the Multipurpose Laboratory Module (Nauka), launched in July 2021, and the other new Russian modules that are proposed to be attached to Nauka. These newly launched modules would still be well within their useful lives in 2024.^[388]

At the end of 2011, the Exploration Gateway Platform concept also proposed using leftover USOS hardware and Zvezda 2 as a refuelling depot and service station located at one of the Earth-Moon Lagrange points. However, the entire USOS was not designed for disassembly and will be discarded.^[389]

In February 2015, Roscosmos announced that it would remain a part of the ISS programme until 2024.^[19] Nine months earlier—in response to US sanctions against Russia over the annexation of Crimea—Russian Deputy Prime Minister Dmitry Rogozin had stated that Russia would reject a US request to prolong the orbiting station's use beyond 2020, and would only supply rocket engines to the US for non-military satellite launches.^[390]

On 28 March 2015, Russian sources announced that Roscosmos and NASA had agreed to collaborate on the development of a replacement for the current ISS.^[391] Igor Komarov, the head of Russia's Roscosmos, made the announcement with NASA administrator Charles Bolden at his side.^[392] In a statement provided to SpaceNews on 28 March, NASA spokesman David Weaver said the agency appreciated the Russian commitment to extending the ISS, but did not confirm any plans for a future space station.^[393]

On 30 September 2015, Boeing's contract with NASA as prime contractor for the ISS was extended to 30 September 2020. Part of Boeing's services under the contract will relate to extending the station's primary structural hardware past 2020 to the end of 2028.^[394]

There have also been suggestions that the station could be converted to commercial operations after it is retired by government entities.^[395]

In July 2018, the Space Frontier Act of 2018 was intended to extend operations of the ISS to 2030. This bill was unanimously approved in the Senate, but failed to pass in the U.S. House.^[396][397] In September 2018, the Leading Human Spaceflight Act was introduced with the intent to extend operations of the ISS to 2030, and was confirmed in December 2018.^{[23][24][398]}

Cost

The ISS has been described as the most expensive single item ever constructed.^[399] As of 2010 the total cost was US$150 billion. This includes NASA's budget of $58.7 billion (inflation-unadjusted) for the station from 1985 to 2015 ($72.4 billion in 2010 dollars), Russia's $12 billion, Europe's $5 billion, Japan's $5 billion, Canada's $2 billion, and the cost of 36 shuttle flights to build the station, estimated at $1.4 billion each, or $50.4 billion in total. Assuming 20,000 person-days of use from 2000 to 2015 by two- to six-person crews, each person-day would cost $7.5 million, less than half the inflation-adjusted $19.6 million ($5.5 million before inflation) per person-day of Skylab.^[400]

See also

• A Beautiful Planet – 2016 IMAX documentary film showing scenes of Earth, as well as astronaut life aboard the ISS
• Center for the Advancement of Science in Space – operates the US National Laboratory on the ISS
• List of commanders of the International Space Station
• List of space stations
• List of spacecraft deployed from the International Space Station
• Science diplomacy
• Space Station 3D – 2002 Canadian documentary

Notes

References

 This article incorporates public domain material from websites or documents of the National Aeronautics and Space Administration.