Since the end of the 30-year US space shuttle programme in 2011, manned space flight has dwindled to a series of mundane but bone-shaking bus-rides on Russian rockets up to the International Space Station in low Earth orbit.

2011年美国结束为期30年的航天飞机计划以后，载人太空飞行就只剩下了一系列寻常而颠簸的搭载俄罗斯火箭前往在低地轨道运行的国际空间站的太空巴士航行。

True, Nasa, still by far the world’s largest space agency, is developing a new generation of manned spacecraft.

没错，作为一直以来全世界最大的航天机构，美国国家航空航天局(Nasa)正在研发新一代载人飞行器。

But a working prototype — let alone a new Apollo-style programme — is many years away.

但是造出一架可投入使用的原型机还需要许多年的时间，更不用说提出一项可与阿波罗计划相提并论的新航天计划了。

Logically, this hiatus should provide an opportunity to rethink the whole purpose of sending people into space, an environment so profoundly hostile that huge sums have to be spent making travel beyond the Earth’s atmosphere even remotely safe.

按理说这个间隙是个很好的时机，我们正好反思把人类送入太空究竟有何意义，毕竟太空环境极其恶劣，仅仅是为了保证飞越地球大气层的航行具有丝毫的安全性就需要投入庞大资金。

But too many Americans still feel a compulsion to spend billions of tax dollars on manned space flight for a re-evaluation to be politically feasible.

但是美国仍然有太多人怀着冲动，希望投入巨额纳税人资金对载人太空飞行进行重新评估，使其具有政治可行性。

When, in 2010, President Barack Obama scrapped the Constellation programme that would have taken the US back to the moon by the next decade, the storm of protest was intense.

2010年美国总统巴拉克•奥巴马(Barack Obama)取消在下个10年重返月球的星座计划时，就引发了强烈的抗议浪潮。

The latest to capitalise on the inchoate desire to slip Earth’s surly bonds is the Silicon Valley entrepreneur, Elon Musk.

最新一位想要利用人类尚处于早期阶段的渴望摆脱地球粗暴羁绊心理的是硅谷企业家埃隆•马斯克(Elon Musk)，他提出了一项让星际旅行梦想复活的计划：

He has come forward with a plan to revive the dream of interplanetary travel, proposing a reusable spaceship that he estimates that could travel between Earth and Mars in three months, starting sometime in the 2020s.

建造一艘可以重复使用的宇宙飞船，它可以在3个月时间内来往于地球和火星之间，在2020年至2030年之间的某个时间点开始投入使用。

This would be the first step to building a larger fleet and ultimately establishing colonies on other planets.

这将是打造一支更庞大飞船舰队的第一步，最终目标是在其他星球建立殖民地。

In Mr Musk’s view, that could allow mankind to become a multi-planet species — thus cheating its inevitable extinction on Earth.

在马斯克看来，这将使人类成为多星球物种，以此逃离在地球上不可避免的灭绝命运。

These are, of course, intoxicating visions. But they also raise questions about the merit of prioritising what remains, surely, a very long-term objective.

这样的愿景当然令人神往，但也不免让人心生疑问：把一个仍然十分长远的目标当作优先事项来处理是否可取？

Mr Musk’s project depends on technologies not yet in existence, whether propulsion systems or the means to protect any interplanetary craft’s human cargo against the impact of radiation in deeper space.

马斯克的计划取决于目前尚未发明出来的技术，无论是推进系统，还是保护星际飞船所载人员免受深层太空辐射影响的技术。

It would require partnerships with the public sector — not least Nasa — that could cost very many billions of taxpayers’ money.

这将需要与公共部门（尤其是Nasa）合作，也就是说可能会耗费数量巨大的纳税人资金。

Then there is the risk of failure damaging confidence in manned space flight for the longer-term future.

况且如果计划失败，可能会在未来很长一段时间内影响人们对载人航天飞行的信心。

It is worth remembering that SpaceX’s own record is not flawless.

应当记住的是，SpaceX本身的记录并不完美。

Two of its unmanned rockets recently blew up, one during a routine refuelling exercise earlier this month.

该公司近期有两枚无人火箭炸毁，其中一枚是本月早些时候在进行燃料补给的常规操作时爆炸的。

There is nothing wrong about bringing in private sector capital and know-how to back space exploration.

引入私营部门资本及技术支持太空探索没有错。

Mr Musk’s SpaceX has, through some clever innovations, helped to bring down the cost of putting unmanned payloads into space.

通过一些巧妙的创新，马斯克的SpaceX帮助降低了把无人航天器送入太空的成本。

But manned space flight remains a grossly extravagant endeavour on any rational evaluation of the scientific benefits, which are often mentioned as its justification.

但是，根据对相关的科学益处（这也往往被视作该领域研究的正当理由）进行的合理评估，载人航天飞行仍然是一项非常奢侈的尝试。

If past funds had instead been invested in unmanned exploration and space science, we would know far more about our solar system, and indeed the universe, than we do today.

如果过去用于该领域的资金投入无人探索和空间科学，我们对太阳系、乃至宇宙的了解会比现在多得多。

Apart from national pride, the real reasons for manned space flight are those outlined by Mr Musk in his presentation.

除了国家自豪感，载人航天飞行的真正原因正是马斯克在其演讲中所阐述的那些。

Advocates talk about the benefits of international collaboration and inspiring the young.

支持者们谈论国际合作的好处以及对年轻人的激励作用。

But above all, there is the human spirit of adventure, the idea that our manifest destiny is to move out from the Earth to explore — and ultimately to colonise — the solar system and the galaxy.

但最重要的是人类的冒险精神，我们相信我们的天赋使命是走出地球，探索太阳系和银河系，并最终在其他星球进行殖民。

This long-term vision lay behind Apollo in the 1960s and also underpins Mr Musk’s interplanetary vision.

这个长远的愿景既是上世纪60年代阿波罗计划启动的背后原因，也支撑着马斯克的星际旅行梦想。

While many people will now regard it as more fantastic than inspiring, it remains the best justification for sending people into space.

尽管现在很多人会认为这个愿景与其说激动人心不如说不切实际，但是它仍然是将人类送入太空的最佳理由。