Chris Hadfield / CSA / NASA via Twitter
SpaceX's Dragon cargo capsule is held by the International Space Station's Canadian-built robotic arm in advance of its berthing on Sunday. "A Dragon, snared and tamed," Canadian astronaut Chris Hadfield wrote on Twitter.
By Alan Boyle, Science Editor, NBC News
The commercial SpaceX rocket venture has launched Dragon cargo capsules to the International Space Station three times in the past year, and every time there's been a problem. Should NASA be upset?
Not really.
The fact that glitches have cropped up ? and have been solved, with no impact on the multimillion-dollar cargo resupply missions ? isn't a black mark against the California-based company. Rather, it's a sign that the designs for SpaceX's Dragon capsule and Falcon 9 are resilient in the face of the inevitable glitches associated with spaceflight. It's also a sign of things to come.
"We may see more mission aborts, where the cost of a mission may be a fraction of the cost of a 'perfect' spacecraft," says James Oberg, NBC News' space analyst. "For the same cost, you could launch three or four, or even eight or 10 'not-perfect' vehicles, with a success rate of 90 to 95 percent. and as a result, for the same starting cost launch many times more missions."
Rand Simberg, a former rocket engineer who now writes about spaceflight for a variety of publications, made a similar point in a PJMedia piece touting SpaceX's latest "successful failure": a problem with the Dragon's thruster system that was resolved when SpaceX's engineers issued commands to cycle the system's valves and clear out the lines with a blast of pressurized gas.
"It was a valuable failure in that it identified a potential problem with either the design or operations but didn't cost them the mission," Simberg wrote. After the system reset, the Dragon's thrusters performed without a hitch. The capsule was brought in for its berthing at the space station on Sunday, just a day later than originally scheduled.
"They did everything exactly right about the vehicle," Bill Gerstenmaier, NASA's associate administrator for human exploration and operations, told reporters after the thruster system was fixed.?
The snags that cropped up during the previous two Dragon launches were similarly resolved without major consequences for SpaceX or NASA:
- Last May, SpaceX's Falcon 9 rocket lit up its engines for launch, but immediately shut them down when the flight computer detected an excessive pressure reading in one of the engines. Engineers found and fixed a problem with the engine's turbopump valve, and a few days later, the Falcon 9 launched the Dragon on a historic demonstration mission to the space station. In August, a NASA panel said it was satisfied with SpaceX's handling of the glitch and its aftermath.
- Last October, one of the nine engines on the Falcon 9's first stage shut down during the ascent, due to a flaw in the sheathing that surrounded the engine. The other engines automatically adjusted their thrust to make up for the shutdown, and the Dragon successfully reached orbit. However, the Falcon wasn't able to put an Orbcomm telecommunications satellite that was carried as a secondary payload in its proper orbit. As a result, the satellite was lost. SpaceX President Gwynne Shotwell said the company tracked down the problem and beefed up its procedure for non-destructive evaluation of the Merlin rocket engines. Since the satellite loss, Orbcomm and SpaceX have renegotiated their launch contract.
SpaceX's communication director, Christina Ra, told NBC News that there the investigation of last week's thruster problem has already begun. "But I am hesitant to give you any commitment on whether or not we can give more detail, and what the timing would be," she wrote in an email, "because it does take time, the information is shared with and approved by multiple parties, and at the end of the day, regulated by ITAR."
That last acronym refers to the International Trade in Arms Regulations, which strictly limit the transfer of aerospace technology to foreign countries. SpaceX fears that the unauthorized disclosure of information about a rocket anomaly would get the company in ITAR trouble with the federal government, and maybe even get someone put in jail. "I don't look good in horizontal stripes," Shotwell joked.
Dealing with anomalies may well be a more frequent option for future spaceflight, even when humans are involved. Oberg noted that the subject came up when millionaire Dennis Tito was discussing his plan to send private-sector astronauts on a 501-day trip past Mars in 2018. "He described how his two-human crew to Mars would be occupied servicing, repairing and coaxing their life support systems, which would be designed to be fixable, not to be 'perfect,'" Oberg said in an email.
This is why SpaceX and NASA's other commercial partners are devoting so much attention to the development of launch abort systems for crew-capable spaceships. Those systems might actually have to be used someday.
"With a commercialized crew taxi that doesn't 'overspend' on unattainable perfect reliability, but accepts the occasional mission failure, you'll fly many more successful missions. You don't have to pay for it in crew safety, just in mission completion rates. And the high flight rates can shake out hardware to enhance reliability far more than flying a vehicle once or twice?a year, as with space shuttles." Oberg said.
"If there isn't a commercial crew mission abort at some point in the first 10 missions, I'd suspect they spent too much on reliability. I'm not talking about somebody getting hurt ? we need to build robust and reliable escape systems ? but just having to come home without accomplishing the purpose of the launch."
Does that sound scary? It shouldn't. The key to success in space may well be to make sure failure is an option that can be dealt with?? as SpaceX demonstrated last week.
March 1: The SpaceX Dragon cargo capsule's arrival at the International Space Station was delayed due to a problem with its thrusters. NBC's Tom Costello reports.
More about commercial space ventures:
Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's?Facebook page, following?@b0yle on Twitter?and adding the?Cosmic Log page?to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out?"The Case for Pluto,"?my book about the controversial dwarf planet and the search for new worlds.
Source: http://cosmiclog.nbcnews.com/_news/2013/03/06/17201079-why-its-good-for-spacexs-private-spaceships-to-rise-above-the-glitches?lite
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