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.

Clark Lindsey is leaving the conference before the end, but he has a lot more summaries of the sessions, many of which looked quite interesting. As before, just keep scrolling. I assume that some time next week, he’ll pull together the individual posts on a single page with permalinks.

One of the more annoying things that I find in commentary on space policy is the assumption that there is One True Way to get off the planet, and that working on anything else (particularly chemical rockets) is a waste of time and money. Often it’s space elevators, but here’s another case in point: an Orion fan (the original Orion, not the current Apollo crew module on steroids):

Nuclear power is still the only thing that’s going to allow us to get large amounts of mass into Earth orbit and beyond. Nothing else has enough specific impulse to do the job.

While nuclear-pulse propulsion may be an interesting technology for in-space transportation, where the radiation level is pretty high to start with, it was never going to be used for earth-to-orbit transportation. One does not have to be a luddite to believe this. I’m all in favor of getting access to orbit as low cost as possible, as soon as possible, but I think that the notion of using Orion for this is nuts (and not just for the radiation and atmospheric contamination issues–consider the EMP…). I highly respect Professor Dyson and Jerry Pournelle as well, but that doesn’t mean that there aren’t some major technical issues in getting such a system practical and operational. If such a system is ever built and tested, it will be built and tested in space, after we’ve come up with other ways of getting large amounts of mass into orbit, affordably. And I’m quite confident that if and when we do this, it will (at least initially) be with chemical rockets.

Part of the misunderstanding is revealed in the second sentence. The assumption is made that the reason costs of getting into space are high is due to performance, and particularly a specific performance parameter–specific impulse. For those unaware, this is basically a measure of a rocket’s fuel economy. The higher the I_sp, the less propellant is required to provide a given amount of thrust over a given time period.

But there is no equation in vehicle design or operations that correlates cost with I_sp. If I_sp were the problem, one would expect propellant costs to be a high percentage of launch costs. But they’re not. Typically, propellant costs are on the order of a percent of the total launch costs. Yes, requiring fewer pounds of propellant means that the vehicle can be smaller, which reduces manufacturing and operations costs, but it still doesn’t account for the high costs.

Chemical rockets are perfectly adequate for affordable launch–their specific impulse is not a problem. As an example of why there’s a lot more to rocket science than I_sp, consider that some of the more promising concepts (LOX/hydrocarbon) actually have lower specific impulse than so-called “high performance” propellants (LOX/LH₂). Why? Because liquid hydrogen is so fluffy (the opposite of “dense”) that the tank sizes get large, increasing vehicle dry mass and atmospheric drag. For instance, the Shuttle external tank carries six pounds of LOX for each pound of hydrogen, but the LOX is all carried in a little tank at the top, and most of the ET that you see contains liquid hydrogen.

As I’ve noted many times before, there are two key elements to affordable launch using chemical rockets. Fly a lot, and don’t throw the vehicle away. Despite the mythology about the Shuttle, we’ve never actually done this in a program. It seems unlikely that NASA ever will, but fortunately, private enterprise is finally stepping up to the plate.