Skip to comments.NASA Moon Rocket May Shake Too Much (Pogo Problem)
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:
It would be bad.
"Egon, define 'bad.'"
“Simple! Reverse the polarity.”
Don’t cross the streams.
That would be bad.
I presume they carry the same instructions as a Chinese firecracker pack:
I agree, it certainly sounds like NASA is taking all the right steps. You make a preliminary design, analyze it and improve it. If this is something that should have been anticipated before the original drawings were begun, that's a bad thing but not a disaster.
All in all, it's merely an uncomfortable stumble, but not really anything like a major embarassment.
We have met the enemy, and he is us?...
I'm so old I've actually used a slide-rule. (AKA a 'friction calculator')...
They need seals at every pipe juncture, pump, valve, and gimbal.
Because in 1960 NASA was a space program, and in 2008 NASA is a federal affirmative action jobs program that needs to satisfy environmentalists and lawyers.
Yeah, and a gerrymandering issue in that Utah wanted a piece of the space pie before its congress crittiers would vote for funding.
The Space Shuttle and the Horse's Rear End
Say friend, did you know that the US Standard railroad gauge (distance between the rails) is 4 feet, 8 1/2 inches.
That's an exceedingly odd number. Why was that gauge used?
Because that's the way they built them in England, and the US railroads were built by English expatriates.
I see, but why did the English build them like that?
Because the first railway lines were built by the same people who built the pre-railroad tramways, and that's the gauge they used.
Well, why did they use that gauge in England?
Because the people who built the tramways used the same jigs and tools that they used for building wagons, which used that wheel spacing.
Okay! Why did their wagons use that odd wheel spacing?
Because, if they tried to use any other spacing the wagon wheels would break on some of the old, long distance roads. Because that's the spacing of the old wheel ruts.
So who built these old rutted roads?
The first long distance roads in Europe were built by Imperial Rome for the benefit of their legions. The Roman roads have been used ever since.
And the ruts?
The original ruts, which everyone else had to match for fear of destroying their wagons, were first made by the wheels of Roman war chariots. Since the chariots were made for or by Imperial Rome they were all alike in the matter of wheel spacing.
Thus, we have the answer to the original question. The United States standard railroad gauge of 4 feet, 8 1/2 inches derives from the original specification for an Imperial Roman army war chariot.
And the motto of the story is Specifications and bureaucracies live forever.
So, the next time you are handed a specification and wonder what horse's ass came up with it, you may be exactly right. Because the Imperial Roman chariots were made to be just wide enough to accommodate the back-ends of two war-horses.
So, just what does this have to do with the exploration of space?
Well, there's an interesting extension of the story about railroad gauge and horses' behinds. When we see a Space Shuttle sitting on the launch pad, there are two big booster rockets attached to the sides of the main fuel tank. These are the solid rocket boosters, or SRBs. The SRBs are made by Thiokol at a factory in Utah. The engineers who designed the SRBs might have preferred to make them a bit fatter, but the SRBs had to be shipped by train from the factory to the launch site.
The railroad from the factory runs through a tunnel in the mountains. The SRBs had to fit through that tunnel. The tunnel is slightly wider than a railroad track, and the railroad track is about as wide as two horses' behinds.
So a major design feature of what is arguably the world's most advanced transportation system was originally determined by the width of a horse's ass.
Well it occurs to me the added danger from solid rocket boosters isn’t the seals themselves but that they have superheated gas flowing past them instead of cool liquid. If I understand it, liquid fuel isn’t ignited until after it is pumped to the reaction chamber.
Too many of NASA's resources have been diverted to "Global Warming" and other issues that are not remotely related to their original mission.
Important safety tip.
The Challenger died because the seals were too cold.
It was so cold on the launch pad that the rubber was too hard to make a good seal.
That is why EVERY ENGINEER involved wanted to suspend the launch until it was warmer.
MANAGMENT wanted the shuttle to be triumphantly in orbit when Reagan gave his State of the Union address.
MANAGMENT bullied the staff into being reasonable, and doing it THEIR WAY (or else!).
The rest is, as they say, History...
“Liquid fuel doent pack the punch of solid fuel, and its harder to store. “
Interesting - I had always assumed that LOX + Hydrogen was about the most powerful fuel you could use. Is that offset by the added tanks, pipes, pumps, engines, etc?
Of course, it is a lot easier to turn off or adjust the thrust on a liquid fueled engine - I guess that is important.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.