Category Archives: Space

Political Commentary, Space

The Cause Of The Ares 1 Problem

23 Comments

Well, actually there are multiple causes, but this is one of them. The launch escape system is very heavy. And it’s heavier than it needs to be because of the inherent inefficiency of the engines resulting from the cant outward (necessary to avoid blasting the capsule with the exhaust). Note that each opposed pair are fighting each other with the horizontal components of their thrust, contributing nothing whatsoever to the mission. This is called a cosine loss because the effective amount of vertical thrust is the total thrust times the cosine of the angle they’re canted at. Since the lost thrust is the sine of the angle, you need more thrust overall (and hence a heavier engine) to compensate, making a bad problem worse.

People have considered putting the escape motor underneath the capsule for this reason (I think that Mike Griffin even drew a napkin sketch of it–we looked at it in OSP as well), but that complicates jettisoning, since it goes between the capsule and the service module. That would mean that you’d have to carry it all the way to orbit on each mission, and then separate, jettison, and redock with the SM, which carries performance and safety risks in itself. Or if it goes under the service module, then the motor has to be a lot bigger, and then you have to do a CM/SM separation after motor burnout but before rotation for entry. So they stuck with the Apollo tractor configuration, in which the capsule is pulled away in an abort.

The other solution, which would give them a ton (actually, literally tons) of margin would be to get rid of the damned thing. It’s only there as a backup in case something goes wrong with the launch vehicle, and then only if specific things go wrong (for instance, a loss of thrust wouldn’t require it). The weight and design is driven by the extreme case in which the upper stage is exploding beneath you and you have to try to outrun the flying debris. This is an extremely unlikely failure mode, but politically, they have to have the system there, because no one wants to take the chance that they’ll have to testify before Congress that they killed astronauts because they didn’t have it. With it, the estimate is a one in five hundred chance of losing a crew. Without it, it’s much higher (though there are no doubt many astronauts who would accept the risk regardless, since they’re already doing so now on the Shuttle).

Also, as Jon Goff has pointed out in the past, they’re putting a lot of effort into safety during ascent, when this is actually one of the lesser hazards of a total lunar mission.

But that’s the way that politics drives a government space program, and why it is so horrifically expensive.

[Update a while later]

It just occurs to me that the other case where you need it is an on-pad, or shortly-after-liftoff abort, when there is insufficient altitude for safe chute deployment.

But the thing to keep in mind is that it made a lot more sense in Apollo, because in the early sixties, “our rockets always blew up.” The technology is much more mature now, and the failure modes for which it would be needed are much less likely, even in an expendable.

Media Criticism, Science And Society, Space

Rolling My Eyes

6 Comments

…at Keith’s brief “review” of my exploration piece:

The author of this article makes some odd, borderline misogynist, and mostly unsupportable claims (mixed with some valid points) as he rambles along trying to explain why people do or not explore. “Empirically obvious“? – Where’s the data to support this?

Where the support for the claim that it is “misogynist,” “borderline” or otherwise? Is he claiming that Cristina Hoff Sommers is misogynist?

What is “odd” about my claims?

And as for the data to support my claim, I provided it in the piece. Things for which there is an “innate human urge” are done by most, if not all humans. Most people don’t explore.

[Update a few minutes later]

One of the commenters over there gets it:

I didn’t see anything misogynist in Simberg’s piece – he’s just pointing out a potential cost of browbeating and drugging boys into behaving more like girls in school.

Exactly. If my piece was (mis)interpreted to imply that women cannot or should not be explorers, that’s absurd, and I would hope obviously so.

Space

The Problem With Ares

7 Comments

Henry Spencer (whose wisdom is finally becoming available on the web, apparently) explains:

An experienced designer with more freedom to act might have realised that there was just too much optimism in the Ares I concept, that a shuttle SRB was simply too small as a first stage for a rocket carrying the relatively heavy Orion spacecraft. There were several ways to handle the situation, but in my opinion the best was to just forget about Ares I entirely: build Ares V, or something like it, right away and use it for all the launches.

With a big launcher, there would be plenty of margin for weight overruns in development. Using the big launcher for Earth-orbit missions would obviously permit much heavier payloads there. Moreover, the lunar missions would get greater margins too, because they’d be done with two big launches rather than a big one and a little one, so they could weigh almost twice as much.

There is also an important pragmatic issue: the biggest threat to NASA’s return to the Moon is the possibility that Congress will delay or cancel development funding for Ares V. Doing Ares V right away, and using it for the Earth-orbit missions as well as the ones to the Moon, would have ensured that this crucial element of NASA’s plans actually gets built.

Of course, better yet would have been a focus on in-space infrastructure, drawing on ISS assembly experience, to allow us to use existing launchers. That would have also freed up money for earlier development of injection stages and landers, and made lunar missions much more of a fait accompli by now.

Space

“Research, Not Mitigation”

3 Comments

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.

Space, Technology and Society

“Snarkyboy” Persists

18 Comments

In a follow-up to the original Orion worship post:

The Saturn V, the biggest thing we’ve ever launched (just go with me here) weighed in at 6,699,000 lbs, or 3,350 tons, and managed to put a measly 100,000 lbs (50 tons) into lunar orbit.

So lets pretend we want to build a classic L5 space colony. How big does it have to be?

Sorry, but we’re not going to “go with you there.”

This is an inappropriate methodology, and the assumptions here are completely nonsensical. The problem has nothing to do with scaling Saturn Vs, and no one in their right mind ever thought that a “classic L5 space colony” would be built completely out of materials launched from the planet.

There is no good reason that we can’t have launch costs of less than a hundred dollars a pound with chemical rockets, and give rides to millions of pounds of passengers and cargo. All that is needed is to make the investment into space transports, and set multiple teams of engineers loose on the problem, something that we have not done to date.

The cargo would be used to bootstrap production facilities for extraterrestrial resources, with high-value/pound payloads (i.e., electronics) coming up from earth. We do not need Orion to build space colonies. We need a lot of other things, but not that.