繁体中文  
 
版主:黑木崖
 · 九阳全新免清洗型豆浆机 全美最低
 
Zuma发射失败表明space X的可靠性仍然成疑
送交者:  2018年01月23日11:14:34 于 [世界军事论坛] 发送悄悄话

JAN 15, 2018 @ 12:22 PM64,763 Doubts About SpaceX Reliability Persist As Astronaut Missions Approach Loren Thompson ,   CONTRIBUTOR I write about national security, especially its business dimensions.   Wikimedia 

A Falcon 9 launch vehicle lifts off with a Dragon spacecraft aboard. The Dragon capsule, currently used for cargo missions, will be equipped to host astronauts under NASA's commercial crew program. We may never know the precise reason a billion-dollar spy satellite that was launched Jan. 7 on SpaceX's Falcon 9 rocket failed to reach orbit. Everything about the mission except the launch itself was secret, so even after a root cause for the loss is identified, few details will be available to the public. However, one thing can already be said for certain: the failed mission isn't going to help SpaceX overcome doubts about the reliability of its launch vehicles. Founder Elon Musk got into the launch business to reduce the cost and increase the reliability of access to space. With regard to cost, he has been spectacularly successful: SpaceX provides launch services at a price well below that of competitors, even state-subsidized offerors such as Europe's Arianespace. With regard to reliability though, the jury is still out, and the evidence is ambiguous. Although SpaceX was quick to assert last week that its Falcon 9 performed as advertised, the secret "Zuma" satellite is the third payload sitting on a Falcon 9 that has been lost in four years. By way of comparison, United Launch Alliance, SpaceX's sole competitor in the military launch business, hasn't lost a single payload in 12 years and 124 missions. ULA once again demonstrated its reliability on Jan. 12, lifting a different spy satellite into orbit for the National Reconnaissance Office. ULA is jointly owned by Boeing and Lockheed Martin, two companies with whom I have long relationships, so you might say I'm biased. But the statistics speak for themselves. The launch alliance hasn't seen a single major failure since it was created a dozen years ago; SpaceX has lately been averaging a major setback every year. In 2015, a Falcon 9 cargo mission to the International Space Station exploded minutes after launch, costing NASA $110 million. In 2016, an Israeli commercial satellite was destroyed on the ground when supposedly routine fueling procedures went dramatically awry (the launchpad was damaged by that explosion). In 2017 the latest version of the company's Merlin rocket engine blew up at a testing facility in Texas. Recommended by Forbes MOST POPULAR Photos: The 10 Most Dangerous U.S. Cities +601,466 VIEWS Apple Leak Reveals Sudden iPhone X Cancellation And now SpaceX has begun 2018 with yet another catastrophe. Maybe SpaceX really isn't responsible for the latest failure; the problem might have been caused by a payload adapter that Northrop Grumman, the company that also built the lost satellite, supplied. But launch providers usually have final responsibility for tip-to-tail readiness before a rocket lifts off, and competitor ULA has successfully employed a variety of payload adapters to attach satellites to its rockets. The most worrisome aspect of this apparent pattern is that the same SpaceX launch vehicle will begin flight tests later this year to carry astronauts to the International Space Station. Boeing and SpaceX both won contracts to deliver astronauts to the space station, and they are in the final stages of developing habitable spacecraft for that purpose. Boeing's Starliner capsule will be lifted by ULA's Atlas V rocket, which has never failed in over 70 launches. SpaceX's Dragon 2 capsule will be carried on the company's Falcon 9 rocket -- the only launch vehicle SpaceX currently operates. It's called Falcon 9 because the first stage relies on nine Merlin engines that the company builds at its Hawthorne, California headquarters. After dozens of successful launches, Merlin is generally considered to be mature technology. However, in the parlance of the space business, it doesn't scale well. So when SpaceX tests a heavier version of Falcon in the near future, its first stage will have 27 Merlin engines. Musk himself has raised the possibility that this improbable design might not work. But it is the Falcon 9 on which SpaceX proposes to carry astronauts, beginning with the first crewed test flight later this year. So NASA managers have to be curious about why the January 7 mission failed. If anything goes wrong with the test flights, or with the subsequent astronaut missions to the space station, it could be a big setback for America's human spaceflight program. Against that backdrop, two recent government reports raise questions bearing upon the reliability of SpaceX products and processes. The first is an evaluation of quality controls among launch-vehicle suppliers to the military space program. That report, prepared by the defense department's Inspector General and dated December 20, found 181 deviations from quality standards at contractor sites. Over a third were "major nonconformities," meaning deviations that might contribute to a failure in quality controls. All of the suppliers surveyed were observed to have issues, but investigators who visited SpaceX sites noted over 50% more major nonconformities there than at United Launch Alliance facilities -- 33 versus 21 major nonconformities. Among other things, the report stated that SpaceX had failed to comply with requirements for reviewing designs, selecting suppliers, documenting program changes, calibrating tools, and monitoring product acceptance criteria. A second report from NASA's Aerospace Safety Advisory Panel dated January 11 singled out two concerns about SpaceX preparations to participate in the civil space agency's commercial crew program -- the program to deliver astronauts to the space station. The first concerned a NASA-mandated redesign of helium tanks that maintain the pressure of liquid oxygen supplies during flight. Deficiencies in a "cryogenic oxygen pressure vessel" are believed to have contributed to the 2016 launchpad explosion that destroyed an Israeli satellite. The second and related issue has to do with seating astronauts aboard crewed missions before supercooled fuel is added, a deviation from accepted practice that the safety panel warned involves significant risk. SpaceX plans to use "densified" fuel to increase the energy of Falcon 9 rockets, but that must be loaded shortly before takeoff, meaning astronauts will already be onboard when the loading occurs. Normal NASA procedure is to put astronauts in their capsule only after the volatile fuel has been loaded. SpaceX continues to favor this "load and go" approach to missions despite the potential dangers involved. The prospect that up to seven astronauts might be sitting atop a rocket while it is being fueled inevitably raises concerns about safety. These concerns would exist even if Falcon 9 had the flawless track record of ULA's Atlas V or Delta IV vehicles. But it doesn't, and that exacerbates the worries. This isn't the first time a NASA safety panel has raised concerns about the "load and go" approach to launch-vehicle fueling -- it was voiced in 2015 too -- but the 2016 launchpad explosion highlighted the danger. The larger question in the aftermath of the failed January 7 mission is what criteria NASA will apply to certifying that Boeing and SpaceX vehicles are ready to lift astronauts to the space station. Washington has been eager to stop using Russian rockets for such missions, but nobody on Capitol Hill wants U.S. astronauts riding on unreliable launch vehicles. The House Science, Space and Technology Committee will hold hearings on NASA's commercial crew program this coming Wednesday. It will be interesting to see how the loss of a billion-dollar spy satellite plays into the discussion of what measures NASA is taking to assure the safety of America's astronauts.

0%(0)
0%(0)
标 题 (必选项):
内 容 (选填项):
实用资讯
北美最大最全的折扣机票网站
美国名厂保健品一级代理,花旗参,维他命,鱼油,卵磷脂,30天退货保证.买百免邮.
一周点击热帖 更多>>
一周回复热帖
历史上的今天:回复热帖
2017: 吕秀莲:要是台湾这两年没稳定 可能就要
2017: 解放军第三代重卡曝光,强悍越野外加全
2016: 我军新研制装甲装备寒区试验:极寒之地
2016: 战前要准备的事情太多了。我有三件事要
2015: 我国超精密光学零件加工技术跨入世界领
2015: 中国首创透明计算:可让计算机彻底减掉
2014: 有气势!
2014: 印度国产神盾舰海试秘照曝光 zt
2013: 不知道真假,感觉又是往中国人身上泼脏
2013: Logic. 请看Encyclopedia Britannica有