原文由美國國家空間學會（NSS）于2019年出品。?
MILESTONE 2
(資料圖片僅供參考)
Continuous Human Occupancy in Low-Earth Orbit
人類在低地球軌道上實現連續居住
Construction of continuously occupied pressurized structuresin low-Earth orbit.
在低地球軌道上建造連續居住的「承壓」結構。
DESCRIPTION
From the U.S. Skylab, to the Soviet Salyut and Mir, to theInternational Space Station (ISS), and China’s Tiangongorbital stations, crewed structures have been placed inorbit and, in the case of the ISS, continuously occupied foralmost twenty years.?
從美國的Skylab，到蘇聯的Salyut和Mir，再到國際空間站，以及中國的天宮軌道站，載人結構已經被放置在軌道上，并且就國際空間站而言，連續占用了近20年。
These space stations are essentiallytools, rather than ends in themselves—laboratories wherewe learn how to construct large structures in orbit, liveand work in space, gather biological data, avoid or survivecollisions with space debris, and explore scientific principlesand technologies that can be developed only in space.
與其說空間站是人類學習如何在軌道上建造大型結構，如何在太空中生活和工作，如何收集生物數據，如何避免與空間碎片相撞或幸存下來，并探索只有在太空中才能開發的科學原理和技術的實驗室，倒不如說他們是一種基礎工具。
The International Space Station will be followed in orbit byother human-occupied facilities, which will likely includehotels, laboratories, factories, and storage depots, withmany of them commercially owned and operated.?
在國際空間站之后的軌道上將有其他人類居住的設施，其中可能包括酒店、實驗室、工廠和儲存庫，其中許多是商業擁有和經營的。
Thesewould support space tourism and recreation, scientificresearch, low-gravity manufacturing, space solar powerinfrastructure, refueling and repair operations, and the like.The lessons learned can then be applied to eventual humanspace settlements.
這些設施將支持太空旅游和娛樂、科學研究、低重力制造、太空太陽能基礎設施、加油和維修作業等等。然后，學到的經驗可以應用于最終的人類空間定居點。
COMPONENTS (needed to create a habitat in space)
先決條件（在太空中創建一個棲息地所需的部件）
No permanent space settlement can be constructed withoutfirst accumulating the technical knowledge, industrial tools,unique materials, and techniques necessary to create sucha novel habitat, as well as biological data about the abilityof humans to survive and thrive for long periods of timeoutside Earth’s atmosphere and without gravity.
如果不首先積累技術知識、工業工具、獨特的材料和創造這種新的棲息地所需的技術，以及關于人類在地球大氣層之外和沒有重力的情況下長期生存和發展的能力的生物數據，就無法建造永久性的太空定居點。
The required knowledge and expertise has been and willcontinue to be acquired by the launching and assemblyof large structures in low-Earth orbit.?
所需的知識和專長已經并將繼續通過在低地球軌道上發射和組裝大型結構來獲得。
This is the closestlocation in which research can occur and techniques can bepracticed, and from which rapid escape in an emergency ismost feasible.
這是可以進行研究和練習技術的最近的地點，而且在緊急情況下迅速逃離是最可行的。
Over time, newer equipment will be added and critical newexperiments conducted onboard these stations.?
隨著時間的推移，將增加更新的設備，并在這些站點上進行關鍵的新實驗。
A variablegravity centrifuge, large enough for small mammals, isneeded to determine the effects of living in partial gravityenvironments such as those found on the Moon and Mars.?
需要一個足以容納小型哺乳動物的可變重力離心機，以確定生活在部分重力環境中的影響，如在月球和火星上發現的環境。
Tests with space solar power wireless energy transmittersand receivers, closed or controlled ecological life supportsystems, and larger, more efficient electrical power systemsare also required.
還需要用空間太陽能無線能量發射器和接收器、關閉或控制的生態生命支持系統以及更大、更有效的電力系統進行試驗。
BARRIERS
阻礙
? High launch cost to LEO.
- 到低地軌道的發射成本高。
? Insufficient focus on non-pressurized docking, external?logistics, and robotic cargo handling for LEO operations.
- 對低地軌道運行的非加壓對接、外部物流和機器人貨物處理關注不夠。
? Insufficiently developed economic justification for ongoing LEO activities.
- 對正在進行的低地軌道活動沒有充分的經濟論證。
? Man-made space debris accumulating in LEO that?pose a hazard to life and property so long as effectiveinternational mitigation efforts are lacking.
- 只要缺乏有效的國際緩解努力，在低地軌道上積累的人造空間碎片就會對生命和財產造成危害。
COMPLETION
達成
The attainment of this milestone will be recognized graduallyas inhabited orbital infrastructures become permanent, aresupported by sustainable economic activity, and include atleast one commercially owned and operated LEO station.
隨著有人居住的軌道基礎設施成為永久性的，并由可持續經濟活動支持，且擁有至少一個商業運營的低地軌道站，這一里程碑的實現將逐漸得到認可。
