NASA Moon Rocket May Shake Too Much (Pogo Problem)
I'm more worried about Owl...
Posted on 01/19/2008 11:03:55 PM PST by anymouse
NASA is wrestling with a potentially dangerous problem in a spacecraft, this time in a moon rocket that hasn't even been built yet.
Engineers are concerned that the new rocket meant to replace the space shuttle and send astronauts on their way to the moon could shake violently during the first few minutes of flight, possibly destroying the entire vehicle.
"They know it's a real problem," said Carnegie Mellon University engineering professor Paul Fischbeck, who has consulted on risk issues with NASA in the past. "This thing is going to shake apart the whole structure, and they've got to solve it."
If not corrected, the shaking would arise from the powerful first stage of the Ares I rocket, which will lift the Orion crew capsule into orbit.
NASA officials hope to have a plan for fixing the design as early as March, and they do not expect it to delay the goal of returning astronauts to the moon by 2020.
"I hope no one was so ill-informed as to believe that we would be able to develop a system to replace the shuttle without facing any challenges in doing so," NASA administrator Michael Griffin said in a statement to The Associated Press. "NASA has an excellent track record of resolving technical challenges. We're confident we'll solve this one as well."
Professor Jorge Arenas of the Institute of Acoustics in Valdivia, Chile, acknowledged that the problem was serious but said: "NASA has developed one of the safest and risk-controlled space programs in engineering history."
The space agency has been working on a plan to return to the moon, at a cost of more than $100 billion, since 2005. It involves two different rockets: Ares I, which would carry the astronauts into space, and an unmanned heavy-lift cargo ship, Ares V.
The concern isn't the shaking on the first stage, but how it affects everything that sits on top: the Orion crew capsule, instrument unit, and a booster.
That first stage is composed of five segments derived from the solid rocket boosters that NASA uses to launch the shuttle and would be built by ATK Launch Systems of Brigham City, Utah.
The shaking problem, which is common to solid rocket boosters, involves pulses of added acceleration caused by gas vortices in the rocket similar to the wake that develops behind a fast-moving boat, said Arenas, who has researched vibration and space-launch issues.
Those vortices happen to match the natural vibrating frequencies of the motor's combustion chamber, and the combination causes the shaking.
Senior managers were told of the findings last fall, but NASA did not talk about them publicly until the AP filed a Freedom of Information Act request earlier this month and the watchdog Web site Nasawatch.com submitted detailed engineering-oriented questions.
The response to those questions, given to both Nasawatch and AP, were shared with outside experts, who judged it a serious problem.
NASA engineers characterized the shaking as being in what the agency considers the "red zone" of risk, ranking a five on a 1-to-5 scale of severity.
"It's highly likely to happen and if it does, it's a disaster," said Fischbeck, an expert in engineering risks.
The first launch of astronauts aboard Ares I and Orion is set for March 2015.
On the Net:
NASA's Ares and Orion program:
http://www.nasa.gov/mission_pages/constellation/ares/index.html
I really enjoyed the chapters in Richard Feynman’s books that talk about his investigation into the shuttle disaster.
It seems that the shuttle is about as safe as they can make it now - about a 1% chance of total loss per flight. That said, 1% can become %100 if the machines are put in situations they weren’t designed for.
Absolutely!
Thanks. Putting it into my seminar for new hire engineers.
It had a buncha crudely drawn missiles flying towards the top of the page and one spiraling down out of control. In the forground is a man in a general's uniform scowling at the dud.
The caption was something like:
Don't give me 99% reliability! Would YOU fly it?
If it were the Shuttle, I would, in a heartbeat!
You’re hiring engineers?
What kind, and where are you????
Hydrogen does have three times the energy of gasoline by weight, for example. The trouble is that liquid hydrogen has only one tenth the density of gasoline, so as a result it has only a third the energy by volume. I don’t know what type of solid fuels the SRB’s use, but for their small size they get much more lbs of thrust than the shuttle itself, which uses hydrogen.
Need any wafer fab people?
n&v, the horse’s patoot has been several places, National Review did it a few years back, but still a great one, too true.
The line in the article that got me cackling was Prof. Arenas’ declaration that “NASA has developed one of the safest and risk-controlled space programs in engineering history.”. Like there’s a lot to compare with in “engineering history” of space flight.
‘Scuse me Prof, but with the limited launches and two total losses, we are running about 1 in 50 lethal/passenger ratio. Bomber pilots from WWII might have admired that, but today we wouldn’t accept it as a loss level amongst pilots flying combat missions.
That said, give me a ticket on a shuttle, it would take physical restraint to keep me off the bird, I don’t care if the odds were 50/50 of return.
Was wondering when this would pop up. Solids are a rough ride, and a single solid with no other mass to dampen the pogo would be roughest of all.
No. That is holding back private space development, not this gov't stuff.
Me too. We're funny that way...
To be fair, the Mercury, Gemini and Apollo spacecraft (and the Shuttle for that matter) were developed by Max Faget (born in British Honduras). And without the spacecraft, the rockets had nothing to send the astronauts up in. The Lunar Module was designed and built by Grumman Aircraft.
Low frequency axial mode problems. Not the first time this has happened in rocket design.
There’s life after silicon?
Geezus Cripes, this is a fundamental design problem that has to be dealt with on EVERY rocket. It ain’t new, it isn’t a show stoper it is business as usual.
It’s rocket science, not brain surgery!
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