中国“长征五号B”火骸坠落问题再次引发担忧 - 纽约时报中文网

周一，中国发射了另一枚“长征五号B”火箭，这是运载天宫空间站部件 所需的强大火箭。这枚火箭将空间站第三个也是最后一个部件送入轨道。

And once again, the rocket’s 23-ton center core stage will tumble back to Earth, uncontrolled, scattering large, heavy pieces of debris that will hit the surface somewhere.

此外，重达23吨的火箭核心级将再次不受控制地坠落地球，将又大又重的残骸散落于地表的某个地方。

“Here we go again,” Ted Muelhaupt, a consultant for the Aerospace Corporation, a nonprofit group largely financed by the U.S. government that performs research and analysis, said in a news conference on Wednesday.

“又来了，”航空航天公司顾问泰德·穆尔豪普特在周三的新闻发布会上表示，该公司是一家主要由美国政府资助并进行研究和分析的非营利组织。

The Long March 5B booster is not the only human-made object, or even the largest, to fall from space. And pieces of spacecraft from other countries, including the United States, have also fallen back to Earth recently — including a small piece of a SpaceX vehicle that turned up on an Australian sheep farm in August .

“长征五号B”火箭的助推器并不是唯一从太空坠落的人造物件，甚至也不是最大的。最近还有包括美国在内的其他国家的航天器残骸已落回地球——包括今年8月出现在澳大利亚一处牧羊场 的SpaceX航天器的一小部分。

But Dr. Muelhaupt and other experts emphasize that such incidents differ from China’s use of the Long March 5B rocket.

但穆尔豪普特和其他专家强调称，此类事件与中国对长征五号B火箭的使用不同。

“The thing I want to point out about this is that we, the world, don’t deliberately launch things this big intending them to fall wherever,” he said. “We haven’t done that for 50 years.”

“我想指出的一点是，我们全世界都不会在发射这么大的东西时故意令其随意坠落，”他说。“50年来我们都没有这样做过。”

Where and when will the rocket body come down?

Where exactly, no one knows — yet. But we’ll know within a few hours, because it is now dropping quickly back into the atmosphere.

目前，确切地点尚无人知晓。但几小时内就能知道答案，因为它现在正在迅速落回大气层。

On Friday evening, the Aerospace Corporation predicted that re-entry would occur at 7:20 a.m. Eastern time. If that is accurate, debris will fall into the southern Pacific Ocean. However, as the booster is speeding around the globe at 17,500 miles per hour, a difference of even a few minutes would shift the re-entry by hundreds of miles.

周五晚间，航空航天公司预测，该火箭将于东部时间早7点20分重入大气层。如果预测准确，残骸将落入南太平洋。但由于助推器正以每小时约28000公里的速度绕地球飞行，即使是时间上的毫厘之差，也会导致重入大气层的路程偏移千里。

What are the odds of being struck by falling debris?

It depends on where you live.

Because of the orientation of the orbit, if you live somewhere like Chicago or somewhere farther north — that includes almost all of Europe and all of Russia — the odds of being hit by this falling rocket are zero. The last few orbits also completely miss Asia and South America. Everyone on those two continents is definitely safe.

由于轨道的朝向，如果你住在芝加哥或者更北的地方——包括几乎整个欧洲和整个俄罗斯——被这枚坠落火箭击中的几率为零。轨道的最后几段也完全错过亚洲和南美洲。这两个大洲上的人都绝对安全。

For people elsewhere, the chances of being hit are minuscule, although not quite zero.

对于其他地方的人而言，被击中的概率也微乎其微，但不完全为零。

“You’ve got far better odds of winning the lottery” than of being hit by part of the Chinese rocket, Dr. Muelhaupt said. “The risk to an individual is six per 10 trillion. That’s a really small number.” (That is, if 10 trillion Chinese Long March 5B rocket boosters fell out of the sky, six of them would hit you personally.)

比起被这枚中国火箭的一部分击中，“你中彩票的几率要高得多，”穆尔豪普特说。“个人面临的风险是10万亿分之六。这是个非常小的数字。”（也就是说，如果10万亿枚中国“长征五号B”火箭助推器从天而降，其中六个会砸到你身上。）

He puts the odds that all of the nearly eight billion people on Earth will survive unscathed at 99.5 percent.

他认为，地球上近80亿人都安然无恙的几率为99.5%。

But the 0.5 percent chance that someone will be hurt is “high enough that the world has to watch and prepare and take precautionary steps, and that has a cost, which is unnecessary,” Dr. Muelhaupt said.

但是，0.5%的有人受伤的可能性“已经足够高，以至于全世界都必须观察、准备并采取预防措施，而这种代价是不必要的，”穆尔豪普特说。

菲律宾海岸警卫队于菲律宾民都洛省寻回的据信属于中国“长征五号B”火箭的残骸，该火箭发射于7月24日。 Aaron Favila/Philippine Coast Guard, via Associated Press

Why focus on the Chinese rocket?

The Long March 5B consists of a large center booster and four smaller side boosters. The side boosters drop off shortly after launch, crashing harmlessly in the Pacific Ocean. But, by design, the core booster stage goes all the way to orbit before deploying its payload.

“长征五号B”火箭由一个大型芯级助推器和四个较小的侧翼助推器组成。侧翼助推器在发射后不久脱落坠入太平洋，没有造成任何伤害。但根据设计，其芯级助推器需要飞向轨道部署有效载荷。

Mengtian docked to China’s orbital outpost on Tuesday. Tiangong, designed to last at least 10 years, is not as big as the International Space Station — it is more comparable in size to the Russian Mir space station that orbited from 1986 to 2001. But it will establish a more permanent base in space than China’s earlier space stations, and more than 1,000 scientific experiments are planned for it in the years to come.

“梦天”实验舱已于周二与中国的轨道前哨对接。“天宫”空间站的设计寿命为至少10年，它没有国际空间站那么大，其大小更接近于1986年至2001年间运行的俄罗斯“和平号”空间站。但它将在太空中建立一个比中国早期空间站更固定的基地，并计划在未来几年进行上千次科学实验。

The Chinese rocket engineers who designed the Long March 5B did not include any way to guide the spent core booster to an empty part of an ocean.

设计“长征五号B”的中国火箭工程师没有顾及到任何将废弃芯级助推器引导至空旷海洋区域的方法。

Instead, the booster gradually falls as it rubs against the wisps of the upper atmosphere. How fast it falls depends on the air density. That varies, because the Earth’s atmosphere puffs outward when the sun is active, spewing out more charged particles, and contracts when the sun is quieter.

相反，助推器会在与上层大气的缕缕摩擦中逐渐下落。其下落速度取决于空气密度。数据会有变动，因为地球大气层会在太阳活跃时向外膨胀，喷出更多带电粒子，太阳不活跃时则会收缩。

Has the rocket’s debris caused damage in the past?

Two of the three previous launches of the Long March 5B — one of the most powerful rockets in operation today — ended with large chunks of metal landing near populated areas. Although no one has been injured, the proximity illustrated the dangers.

作为目前威力最大的运行中火箭之一，“长征五号B”此前三次发射，有两次存在大块金属落在有人居住区域附近的情况。虽然无人受伤，但距离的接近表明了其危险性。

For the first launch of the rocket, in 2020, the booster made an uncontrolled re-entry over West Africa, with some debris landing on a village in Ivory Coast. After the third launch, in July, the uncontrolled re-entry occurred over Southeast Asia , with pieces landing in Malaysia.

该火箭在2020年首次发射时，助推器在西非上空失控再入，一些残骸落到了科特迪瓦的一处村庄。在今年7月的第三次发射后，失控再入发生在东南亚 ，有残骸落在马来西亚。

“Again, big chunks of metal have come down near where people are,” Dr. Muelhaupt said.

“再一次，大块大块的金属掉落在人类居住地的附近，”穆尔豪普特说。

He said there was no indication that China had made any of the significant modifications to the rocket design that would be needed for a controlled re-entry.

他说，没有迹象表明中国对火箭设计进行了任何控制重入大气层所需的重大修改。

China has at least one more Long March 5B launch planned, for next year, to put in orbit a space telescope, Xuntian, that would rival NASA’s Hubble space telescope .

And it is probable that debris from American rockets and spacecraft will turn up on land again, too, like the SpaceX vehicle part found in Australia.

美国火箭及航天器的残骸也很可能会再次坠落地表，正如在澳大利亚发现的SpaceX航天器部件一样。

But there is little need to worry about the upcoming flight of NASA’s massive moon rocket, the Space Launch System, the agency says. The S.L.S., the biggest rocket to fly since the Saturn V used for the Apollo missions, is scheduled to make its first flight later this month. Its center core stage travels almost all the way to orbit, but NASA officials said on Thursday that its trajectory was designed to re-enter not long after launch in a specific unpopulated area.

但美国宇航局表示，对接下来重型月球火箭“太空发射系统”（简称SLS）的飞行无须有多少担忧。SLS是继用于“阿波罗”任务的“土星5号”之后最大的火箭，计划在本月晚些时候进行首次发射。该火箭的中央核心级会几乎抵达轨道，但美国宇航局官员周四表示，其轨迹按照设计会在发射后不久再入，落入一个具体的无人区域。

“It’s in an area of the ocean where it won’t affect anyone,” said James Free, the associate administrator for exploration systems at NASA.

“它会落到不影响到任何人的海域，”管理美国宇航局勘探系统的副署长詹姆斯·弗里说道。