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"Research, Not Mitigation"

This (to me) amazing report on the status of the thrust-oscillation problem just has me shaking my head. If accurate, they don't even understand enough about it yet to know which weight-increasing kludge may mitigate it, and by how much. And the vaunted Ares 1-X "test" next year won't provide them with the information they need:

I see no discussion of the new failure modes that could be introduced by the addition of these systems, or their effects on first-stage reliability (which was supposedly the big feature of this approach). For example, if the active system has a failure (and I suspect that a failure of just one of the engines would be a failure, due to asymmetries), the vehicle will get shaken apart. It seems to be single point (unless they can still reach the oscillation-reduction goal with single engine out).

And now they're going to put shock absorbers into the couches to further isolate the crew, which implies that the Orion itself is going to sustain a lot more rockin' and rollin' than the current requirement stipulates. Which in turn implies a heavier vehicle to handle the accelerations and stress.

No one will consider the possibility, apparently, that this is an unclosable design, though such things happen in real life, once one gets outside of Powerpoint world.

With the July status of the engineering efforts showing the issue to be an across the board high "RED" risk to Ares I's development, the mitigation process is likely to continue until at least the end of the decade.

So months more, and billions more, without knowing whether or not the road they're on is a dead end.

[Update a few minutes later]

More depressing news (again, assuming accuracy) here.

[Another update]

The Chinese seem to be having problems, too:

China's English language state owned television channel CCTV9 has revealed the fact that on its past two manned missons the astronauts have experienced physical discomfort from the vibration of the rocket on its ascent

The tv news segment goes on to report that the rocket's chief designer says that changes to the "frequencies" of the engines and the "electrical circuits" have been made to try to eliminate this vibration problem.

Whatever that means. I wonder if it's POGO? And just how much "physical discomfort" was there? Not enough to end the missions, or the crews, apparently.


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K wrote:

Someone needs to get Boeing and Musk or someone together and build a capsule that would fit on the EELV. Otherwise, the US is going to be using the Russians taxi to orbit for 5 to 10 years after Shuttle retirement.

Or maybe this is all just a plan to keep the shuttle around for another 5 years.

ken anthony wrote:

Rand, how can you attend an engineering meeting with such an annoying understanding of the facts? I can imagine the other engineers chasing you with torches and pitchforks from the meeting. When you see things before others you get opposite reaction one would hope for. At least that's been my experience. After two engineering meetings at a company I used to work for, I stopped attending because they were just a waste of time.

...and they don't learn from their committed mistakes either.

Isn't the solution to most vibration issues a change of geometry?

Habitat Hermit wrote:

"Isn't the solution to most vibration issues a change of geometry?"

You mean the geometry of the grain core/hollow? I'm pretty sure they've done that from the start and also changed the mix/composition of the grain, as far as I know it's impossible not to when you significantly change the SRB like they've done several times (length/segments, burn rate for several different reasons etc.). The SRB diameter is pretty much fixed and with that you get about the same lengths for a specific amount of fuel no matter what and the more oomph you need in a single stage the longer it gets which makes everything harder and round and round we go as long as it's meant to be able to fool politicians into thinking it's Shuttle SRB derived in any significant way. Phew!

So it's not merely a Rude Goldberg contraption but a Goldbergian Perpetuum Mobile with rockets attached and should be ready to go shortly before the heat death of the universe ^_^

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This page contains a single entry by Rand Simberg published on July 21, 2008 6:32 AM.

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