原文由美国国家空间学会（NSS）于2019年出品。
MILESTONE 2
(资料图片仅供参考)
Continuous Human Occupancy in Low-Earth Orbit
人类在低地球轨道上实现连续居住
Construction of continuously occupied pressurized structuresin low-Earth orbit.
在低地球轨道上建造连续居住的「承压」结构。
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.
从美国的Skylab，到苏联的Salyut和Mir，再到国际空间站，以及中国的天宫轨道站，载人结构已经被放置在轨道上，并且就国际空间站而言，连续占用了近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.
与其说空间站是人类学习如何在轨道上建造大型结构，如何在太空中生活和工作，如何收集生物数据，如何避免与空间碎片相撞或幸存下来，并探索只有在太空中才能开发的科学原理和技术的实验室，倒不如说他们是一种基础工具。
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.
在国际空间站之后的轨道上将有其他人类居住的设施，其中可能包括酒店、实验室、工厂和储存库，其中许多是商业拥有和经营的。
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.
这些设施将支持太空旅游和娱乐、科学研究、低重力制造、太空太阳能基础设施、加油和维修作业等等。然后，学到的经验可以应用于最终的人类空间定居点。
COMPONENTS (needed to create a habitat in space)
先决条件（在太空中创建一个栖息地所需的部件）
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.
如果不首先积累技术知识、工业工具、独特的材料和创造这种新的栖息地所需的技术，以及关于人类在地球大气层之外和没有重力的情况下长期生存和发展的能力的生物数据，就无法建造永久性的太空定居点。
The required knowledge and expertise has been and willcontinue to be acquired by the launching and assemblyof large structures in low-Earth orbit.
所需的知识和专长已经并将继续通过在低地球轨道上发射和组装大型结构来获得。
This is the closestlocation in which research can occur and techniques can bepracticed, and from which rapid escape in an emergency ismost feasible.
这是可以进行研究和练习技术的最近的地点，而且在紧急情况下迅速逃离是最可行的。
Over time, newer equipment will be added and critical newexperiments conducted onboard these stations.
随着时间的推移，将增加更新的设备，并在这些站点上进行关键的新实验。
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.
需要一个足以容纳小型哺乳动物的可变重力离心机，以确定生活在部分重力环境中的影响，如在月球和火星上发现的环境。
Tests with space solar power wireless energy transmittersand receivers, closed or controlled ecological life supportsystems, and larger, more efficient electrical power systemsare also required.
还需要用空间太阳能无线能量发射器和接收器、关闭或控制的生态生命支持系统以及更大、更有效的电力系统进行试验。
BARRIERS
阻碍
• High launch cost to LEO.
- 到低地轨道的发射成本高。
• Insufficient focus on non-pressurized docking, external logistics, and robotic cargo handling for LEO operations.
- 对低地轨道运行的非加压对接、外部物流和机器人货物处理关注不够。
• Insufficiently developed economic justification for ongoing LEO activities.
- 对正在进行的低地轨道活动没有充分的经济论证。
• Man-made space debris accumulating in LEO that pose a hazard to life and property so long as effectiveinternational mitigation efforts are lacking.
- 只要缺乏有效的国际缓解努力，在低地轨道上积累的人造空间碎片就会对生命和财产造成危害。
COMPLETION
达成
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.
随着有人居住的轨道基础设施成为永久性的，并由可持续经济活动支持，且拥有至少一个商业运营的低地轨道站，这一里程碑的实现将逐渐得到认可。
