日本研发出世界首颗木制卫星 使用后不会造成太空污染

随着太空中的卫星越来越多，太空污染已经成为不可忽视的问题。为此，日本科学家研发出了世界首颗木制卫星，这种卫星在完成任务重新进入大气层燃烧时，只会产生一点可生物降解的灰。

Japanese scientists have created one of the world’s most unusual spacecraft – a tiny satellite that is made of timber.

日本科学家制造出了全世界最独特的航天器——用木材做成的微型卫星。

The LignoSat probe has been built of magnolia wood, which, in experiments carried out on the International Space Station (ISS), was found to be particularly stable and resistant to cracking. Now plans are being finalised for it to be launched on a US rocket this summer.

这枚名为LignoSat的航天探测器是用木兰木制成的，在国际空间站上开展的实验中发现，木制卫星特别稳定，也不容易开裂。现在计划今年夏天将这颗木制卫星放在美国火箭上发射出去，目前该计划还未最终敲定。

The timber satellite has been built by researchers at Kyoto University and the logging company Sumitomo Forestry in order to test the idea of using biodegradable materials such as wood to see if they can act as environmentally friendly alternatives to the metals from which all satellites are currently constructed.

这颗木制卫星是由京都大学的研究人员和伐木企业住友林业公司联手制造的，目的是测试木头这种可生物降解材料是否能够作为替代当下用来制造所有卫星的金属材料的环保选择。

"All the satellites which re-enter the Earth’s atmosphere burn and create tiny alumina particles, which will float in the upper atmosphere for many years,” Takao Doi, a Japanese astronaut and aerospace engineer with Kyoto University, warned recently. “Eventually, it will affect the environment of the Earth.”

日本宇航员、京都大学航天工程师土井隆雄表示：“所有重新进入地球大气层的卫星都会燃烧并产生氧化铝微粒，这些微粒会在高层大气中飘浮许多年，最终会对地球环境造成影响。”

To tackle the problem, Kyoto researchers set up a project to evaluate types of wood to determine how well they could withstand the rigours of space launch and lengthy flights in orbit round the Earth. The first tests were carried out in laboratories that recreated conditions in space, and wood samples were found to have suffered no measurable changes in mass or signs of decomposition or damage.

为了解决这一问题，京都大学的研究人员设立了一个项目来评估各种类型的木材是否能很好地承受太空发射以及绕地飞行漫长旅途的强度。第一批测试是在还原太空条件的实验室中进行的，研究人员发现木材样本的质量没有明显改变，也没有呈现出分解或毁坏的迹象。

"Wood’s ability to withstand these conditions astounded us,” said Koji Murata, head of the project.

该项目的负责人村田浩二表示：“木材在这些条件下的抗压能力让我们感到震惊。”

After these tests, samples were sent to the ISS, where they were subjected to exposure trials for almost a year before being brought back to Earth. Again they showed little signs of damage, a phenomenon that Murata attributed to the fact that there is no oxygen in space which could cause wood to burn, and no living creatures to cause it to rot.

在测试结束后，木材样本被送到了国际空间站，在那里木材样本暴露在太空环境下进行了将近一年的测试才被送回地球。这一次木材样本依然没有呈现出多少损坏的迹象，村田浩二将这一现象归结于太空中没有导致木材燃烧的氧气，也没有导致木材腐烂的生物。

Several types of wood were tested, including Japanese cherry, with wood from magnolia trees proving to be the most robust. This has now been used to build Kyoto’s wooden satellite, said Murata.

研究人员测试了包括日本山樱木在内的几种木材，事实证明木兰木是最坚固的。村田浩二指出，当前京都大学的木制卫星就是用木兰木制作的。

Murata added that a final decision had still to be made on the launch vehicle, with choices now narrowed down to a flight this summer on an Orbital Sciences Cygnus supply ship to the ISS or a similar SpaceX Dragon mission slightly later in the year. It is expected that the probe – which is the size of a coffee mug –will operate in space for at least six months before it is allowed to enter the upper atmosphere.

村田浩二补充道，是否将木制卫星投入生产还需要最后的测试才能做决定，眼下有几个测试选择，其中就包括今年夏天让木制卫星搭载“天鹅座”货运飞船前往国际空间站，或在今年晚些时候搭载龙飞船去太空。这枚只有咖啡杯大小的探测器预计将在太空运行至少6个月再返回高层大气。

If the LignoSat performs well ­during its operation in orbit, then the door could be opened for the use of wood as a construction material for more satellites. It is estimated that more than 2,000 spacecraft are likely to be launched annually in coming years, and the aluminium that they are likely to deposit in the upper atmosphere as they burn up on re-entry could soon pose major environmental problems.

如果LignoSat探测器在轨运行良好，木材将会正式获批成为卫星的建造材料。据估计未来每年将会建造超2000枚探测器，这些铝制探测器重新进入地球大气时燃烧后留在高层大气中的氧化铝颗粒物将会造成严重的环境问题。

Recent research carried out by scientists at the University of British Columbia, Canada, revealed that aluminium from re-entering satellites could cause serious depletion of the ozone layer which protects the Earth from the sun’s ultraviolet radiation and could also affect the amount of sunlight that travels through the atmosphere and reaches the ground.

加拿大不列颠哥伦比亚大学的科学家最近开展的一项研究发现，卫星重新进入大气时留下的铝离子将会导致隔离太阳紫外线的臭氧层严重耗损，没有了臭氧层，穿过大气层并到达地面的日照量也会增多。

However, this should not be a problem with satellites built of wood, like LignoSat, which, when it burns up as it re-enters the atmosphere after completing its mission, will produce only a fine spray of ­biodegradable ash.

但是，像LignoSat这样的木制卫星就不会产生这种问题，在完成任务重新进入大气层燃烧时，它只会产生一小把可生物降解的灰。