Clark Lindsey points to a study (with which new NASA administrator Mike Griffin was heavily involved) that's been kicking around for about a year now, apparently popular with some in the astronaut office, proposing an SRB-based crew launch system. Clark notes that "The reasoning is that this system could be developed more quickly than a CEV on a Delta IV or Atlas V since the SRBs are already 'human-rated.'"

Well, not exactly. At least, they (correctly) don't say that. As I've noted many times in the past, the phrase "human rated" is a very misleading one. What they actually say is that "...the SRM has proven to be the most reliable launch vehicle in the history of manned space flight, with no failures in 176 flights following the modifications implemented in the aftermath of the Challenger accident."

The reality is that the SRB is not "human rated." In fact (surprising to many) the Shuttle itself is not. "Human rated" or "man rated" is a phrase that so many misuse that I'd just like to purge it from our vocabulary, because as I've explained, it's really a relic of the sixties. All we can say about the SRB is that it has flown reliably (at least after the O-ring problem was resolved) on our only vehicle that carries crew. As such, it may be the basis of a relatively (as expendable launchers go) safe ride for astronauts.

One thing that I never see mentioned in this concept, though, is how they propose to do roll control. The current SRB has none, because it is part of a larger vehicle, which rolls by gimbaling its nozzles. As a stand-alone system, it would have no roll authority at all, without adding fins or a reaction control system. Is that what those little appendages down at the bottom of the figure in Clark's post are meant to represent?

In any event, such a vehicle will in fact be a new launch system (and one with a pretty rough ride and probably pretty high accelerations toward the end of the burn)--no one will be able to simply stick a capsule on top of an SRB.

[Update about noon eastern]

I just noticed another depressing little statement in the report: "During the time frame addressed by this report—the next several decades—the cost of access to Earth orbit can hardly be less than several thousand dollars per kilogram, and, as we have discussed, even a Spartan expedition to Mars will require many hundreds of metric tons of material to be delivered to LEO."

With an attitude like that, we're going to waste a lot of money trying to get to other planets. Or even into orbit, for that matter. That's why I think that much of the funds being spent for the VSE program will be for naught. But they probably won't be spent any worse than they have been for the past three decades, and at least now we have an interesting goal.

I figured that term would get your attention. ;-) I put it in quotes because I know it is controversial and I don't necessarily agree with it. In this case, I was following the description of the Planetary report given in the AvWeek article:

"The shuttle-derived CEV launcher has also been touted by SRM-manufacturer ATK Thiokol and others as a faster and cheaper approach that would avoid the need to human-rate expendable launch vehicles (ELVs) like the Atlas V and Delta IV (AW&ST June 28, 2004, p. 26). The SRM is already rated safe for human flight, and the Planetary Society report suggested a version of the space shuttle main engine or the Apollo-era J-2S Saturn engine--also human-rated--for the upper stage."

While attitude control isn't a solved problem, adding such a system really shouldn't be that hard (IMHO). Rand, I do see the problem you mention with the diagram. With the somewhat bulbous top portion and tiny fins, this vehicle would appear to have a rather high "center-of-pressure". As an aside, the center-of-pressure is the geometric "center of mass" of the cross-section of the rocket from the side, the center-of-pressure should be below the actual center of mass unless you use some sort of active control system (imagine balancing a broom in a wind, it's much easy to do if you add weights to the top of the broom, or if you have someone steadying the top of the broom. If you add weight to near the bottom, you actually make the broom more unstable).

Acceleration apparently is a somewhat solved problem. They apparently can and do "taper" the burn rate near "burnout" the point where the vehicle is lightest and acceleration greatest due to exhaustion of most of the fuel. Still would probably be a rough time near that point.

I tried to point out the news item at Hobbyspace in an earlier comment here, in the context of why I think subsidies are a bad idea. We'd be too likely to wind up with what we've always gotten.

I am amazed and aghast that anyone still takes this "SRM-derived vehicle" seriously. Let's look at what else is available in this payload class:

Delta IV Heavy
Atlas V Heavy
Ariane V
Proton
Titan IV (if anyone was silly enough to order more)

Plus, in short order if anyone wanted to pay for it:

Growth H-IIA
Growth Zenit/Sea Launch
Growth Long March
Angara
Growth Falcon V

So NASA decides that, with limited time and funds, it makes sense to develop an ELEVENTH launcher in this weight class. Does this make sense to anyone?
Based on the SRM, no less, which has "only" killed seven people so far, and is no cheaper or more reliable than a pure-expendable segmented SRM (compare to Titan IV SRMU, for example). And which, not so very long ago, was declared unsafe enough that we really really needed to fund a $3 billion functionally identical motor (the ASRM) just to reduce the number of "leak paths".

Message to NASA: you can go to the moon and Mars, or you can spend the money instead subsidizing Thiokol and polishing pads 39A and B. There is not enough money to do both.

If it's such a great idea, why hasn't Thiokol developed it on their own? I mean, they had a cash stream coming in from the sales of the things.

This seems more like an idea some sales guy at Thiokol came up with than a well-thought-out design.

For one thing, the SRB has no ability to cut off if it develops a problem. It's a booster, not a primary launch vehicle.

For one thing, the SRB has no ability to cut off if it develops a problem. It's a booster, not a primary launch vehicle.

Not that this makes it any safer or easier for carrying humans, but they do have a "cut off" of sorts with the self-destruct.

Oh, yeah, I want to ride something that the only way to shut it down in case of trouble is to explode.

sheesh

What would make a lot more sense is if Thiokol was working on a hybrid replacement. That wouild allow the thing to throttle and shut off.

Correct me if I'm wrong, but wouldn't a hybrid have less chance of exploding too? It would only burn where the oxidizer is, instead of exploding when there was a bubble?

> And which, not so very long ago, was declared unsafe enough that we really
> really needed to fund a $3 billion functionally identical motor
> (the ASRM) just to reduce the number of "leak paths".

McDD's estimate for DC-Y was around $1.5 billion. NASA's estimate for 2nd Generation RLV, overengineered as it was, was only $5-6 billion.

Now we're talking $3 billion for a solid rocket motor, $15 billion for a CEV capsule -- who was it that said expendables were cheaper?

Nice and to-the-point post there Rand, hard to disagree with that.

What would the "man-rating" or whatever they're going to do, include with the EELV's? This is an important question when comparing to the shuttle solid rocket which already has a lot of flights behind and has in that way (partially) proven itself.

Are there some inherent design decisions in EELV's that would cause problems with human flight and would have to be revamped? Surely they looked at human flight possibilities when designing those rockets - but did they exclude those things from all the requirements?

Off the top of my mind it would feel a lot cheaper just to check the designs, test components and fly a dozen test flights with EELV('s). Hey, you can even launch satellites on some of those test flights. Much cheaper than to start pieceing up a totally new launcher (...again).

Another comment comes to mind: the capsule is visibly larger than the SRB, but otherwise looks like an Apollo capsule.

I just checked the net, an Apollo capsule was 12.8 feet in diameter, while a shuttle SRB is 12 feet in diameter.

The pictured CEV is larger than that.

Why are they so dead-set towards building a CEV that will only fit on the heavier medium lift boosters?

With Liftport opening its first carbon nanotube manufacturing facility, the potential cost of access to LEO could conceivably drop by three orders of magnitude over the next 20 years.

When I first saw this configuration, I thought it was a journalism error, and every time I look at a diagram of it, I wish that my initial assessment was correct.

I believe that the roll control would be accomplished through roll jets on the second stage. Odd, to be sure, but I don't think it violates any laws of physics.

As to why ATK wouldn't develop this on their own...they haven't been paid to do so. There are some cool computer graphics of the system around, but doing any of the serious work would require serious money and very few traditional aerospace contractors would stick their neck out like that.

On man-rating, my feelings echo Rand's. To me, a system should be judged on how it can handle big problems and still allow a crew to walk (or swim) away from the event. Briefing charts with lots of 9's on them (such as 99.999999999% reliable) mean very little if the option is that no one gets out alive.

In the proposed vehicle roll control would be performed by the second stage. The trajectory has some unfavorable characteristics. Max-q is over 1100psf which is outside the range of any NASA experience; late ballistic aborts impose a high g and thermal load; and acent g loads are somewhat unfavorable.

To alleviate case burst concerns ATK has proposed adding a "blow-out" panel but the problem of escaping a thrusting vehicle seems challenging, e.g. a 12g escape at max-q might not be sufficient.

The addition of a blow out panel and new loads on top mean the vehicle would have to be recertified which weakens their claim somewhat.