Category Archives: Space

Silk Purses From Sow’s Ears

When NASA first proposed a single-SRB-based launcher, one of the issues that jumped out immediately to many familiar with vehicle design and Shuttle design was roll control. As designed for the Shuttle, there are two SRBs, both of which can gimbal the engines. This allows roll control of the Shuttle stack by gimbaling them in opposite directions. But when there’s only one, the engine gimbal provides pitch and yaw control, but there’s no way for it to control roll.

There are two potential solutions to this–to modify the SRB itself to add roll-control thrusters, or to incorporate them into the new upper stage. The latter has the disadvantage of oversizing the roll-control system for the period after stage separation, which adds weight and affects performance, but it simplifies design by requiring only one system.

In any event, the concept seems to be in trouble. Now this certainly isn’t a show stopper, and issues like this are inevitable in the development of a new launch vehicle, but it’s just one more demonstration of the fact that deriving a new launcher from existing pieces isn’t as easy as has been advertised by many, both within and out of the agency.

[Late morning update]

Gary Hudson emails one other option:

There is a third possibility: let it roll. Depending on the rate and duration, it may not be a problem. Some current vehicles do this (Taurus, for one) and we are planning a subset of it for the AirLaunch QuickReach. In our case, we have a Stage Two roll thruster but its purpose is to limit the rate, not hold a specific roll attitude. Makes for a much small thruster. It is later used as part of the normally smaller sized Stage Two attitude control subsystem.

Silk Purses From Sow’s Ears

When NASA first proposed a single-SRB-based launcher, one of the issues that jumped out immediately to many familiar with vehicle design and Shuttle design was roll control. As designed for the Shuttle, there are two SRBs, both of which can gimbal the engines. This allows roll control of the Shuttle stack by gimbaling them in opposite directions. But when there’s only one, the engine gimbal provides pitch and yaw control, but there’s no way for it to control roll.

There are two potential solutions to this–to modify the SRB itself to add roll-control thrusters, or to incorporate them into the new upper stage. The latter has the disadvantage of oversizing the roll-control system for the period after stage separation, which adds weight and affects performance, but it simplifies design by requiring only one system.

In any event, the concept seems to be in trouble. Now this certainly isn’t a show stopper, and issues like this are inevitable in the development of a new launch vehicle, but it’s just one more demonstration of the fact that deriving a new launcher from existing pieces isn’t as easy as has been advertised by many, both within and out of the agency.

[Late morning update]

Gary Hudson emails one other option:

There is a third possibility: let it roll. Depending on the rate and duration, it may not be a problem. Some current vehicles do this (Taurus, for one) and we are planning a subset of it for the AirLaunch QuickReach. In our case, we have a Stage Two roll thruster but its purpose is to limit the rate, not hold a specific roll attitude. Makes for a much small thruster. It is later used as part of the normally smaller sized Stage Two attitude control subsystem.

The Once And Future King?

George Abbey, who ran NASA’s manned spaceflight program in the Goldin years, seems to be attempting to position himself to replace Mike Griffin with the advent of a Democrat administration. There are some grammar problems with this report of a recent speech by him (it reads sort of like a live blog of the speech). I know that you will all be shocked to hear this, but he doesn’t want to replace the Shuttle–he wants to keep operating it:

The space program needs realism, Abbey said. Putting an end point on the shuttle forces NASA to focus all of its remaining missions on the space station, giving little leeway for other missions.

What other missions? Other than Hubble, what does he have in mind? Surely he doesn’t think that we can afford to do deep space exploration with it as a launch vehicle?

If we don’t retire it, how long does he expect to be able to keep operating it? What happens when (not if) we lose another orbiter?

The major difference between the two craft, Abbey said, is versatility a handy attribute when working in space [sic–I assume that there is supposed to be some kind of punctuation after the word “versatility”]. (Orion) is not as capable as the shuttle it cant [sic] do any of the things the shuttle can do.

Well, it certainly can’t do all the things that the Shuttle can do, but it can certainly (at least in theory) deliver crew to space and back, which is one of the things that the Shuttle can do. Whether or not it even should be able to do all of the things that the Shuttle can do is barely even debatable any more, given the consensus of most observers of the program that a primary problem with Shuttle is that it had too many conflicting requirements. This is thinking right out of the early seventies, and it’s also thinking born of a career at NASA, in which it is automatically assumed that we can only afford one vehicle type, so it must do everything (ISS was severely crippled by this attitude as well). And of course any system that has to have so much capability, if it’s possible at all, will be very expensive to develop and operate, so the notion that we can only afford one becomes a self-fulfilling prophecy.

I find his concern about other space nations misplaced. Certainly China isn’t going to make any great strides at their current place. And his spinoff argument is typical NASA fluff. The only thing he says that I agree with, in fact, is about ITAR (at least I assume that’s what he’s talking about when he says):

First, Abbey said too much government red tape is making it very difficult for wanting nations to purchase satellites from the U.S. The red tape is forcing nations to other competitors those competitors are surpassing us.

Of course, it’s hard to know exactly what he said, or meant, given the quality of the reportage.

(Not So) Hidden Agendas?

I’ll probably have some commentary on this when I get more time (i.e., when relatives aren’t visiting for the weekend), but Jon Goff has an interesting post on some candid comments by Doug Stanley on ESAS. I’m sure that Doug is sincere in his beliefs that a) Mars is more important than the moon and b) ESAS is the best way under the political circumstances to make it happen. But I think he’s wrong on both counts, and more importantly it is not his place (or even Mike Griffin’s) to make policy. If he has problems with VSE as stated, and wants to do a touch and go on the moon (ignoring the president’s directive), he should work to get the policy changed, rather than pervert the architecture in his preferred direction without such a debate.

[Update on Monday morning]

More interactions with Dr. Stanley, from Keith Cowing.

Encouragement

Jon Goff is unaccountably questioning the value of his blogging. I haven’t been linking to him as much as I should, but he has been putting up a lot of well-thought-out and thought -provoking posts on potential space architectures that would be far superior to NASA’s current plans. Head over there and tell him to keep it up.

I do second the recommendation to get off Blogspot, though. If nothing else, it would allow him to post his URL in comments here.

Step Backwards

Clark Lindsey notes that the FAA-AST web site has been revamped, by folding it into the general FAA web site. While the improvements he notes are worthwhile (though the changing of permalinks definitely is not), I’m unthrilled with the concept of entwining AST even more deeply with the FAA. AST was originally the Office of Commercial Space Transportation, reporting directly to the Secretary of Transportation. The Clinton administration demoted it, and folded it into FAA in the early nineties.

This had two deleterious effects. First, it gave it less clout within the department, since the AA for it now had to report to the SecTran up through the FAA administrator. Second, it placed it in an agency that, after the Valujet crash, had its responsibility declared solely for public safety, with none to promote the aviation industry (one of its charters in the early days).

But the infant space transportation industry needs a different balance between safety and promotion than a mature aviation industry, and there is a potential clash of regulatory cultures as long as AST remains within FAA. Its current bureaucratic abode makes it much easier to justify nannyism that could strangle it in the cradle. I think that there should be a push on by the space activist community to restore it to its original position as a separate administration within DOT, and I’m not happy whenever I see its status as a subset of FAA further entrenched.

Maybe We Need To Be Louder

Clark Lindsey isn’t impressed by Scott Horowitz’ ability to ignore “outside noise:”

I guess this is an improvement over the deaf/mute NASA that produced the Space Shuttle, the ISS, X-33, X-34, SLI, OSP, etc. NASA leaders were then completely oblivious to the existence of any outside voices on space hardware development and never felt it necessary to address complaints from know-nothings (i.e. anyone not working at NASA). At least now they go to the window and before closing it they yell at the peons outside to shut up and stop making a racket.

Save Centennial Challenges

Rick Tumlinson challenges the space activist community:

The most disappointing thing about the state of the Centennial Challenges is that the pro-frontier/pro-NewSpace community hasn’t made Congress change its position.

Given the importance we have all attached to prizes and new ways of NASA/USG doing things in space, the tepid response of this community and its inability to raise enough pressure to get the prizes funded shows we are either too weak to effect significant change, too disorganized to do so, or we simply don’t care or aren’t willing to put our muscle where our mouth is.

We have a few weeks to put that pressure on and bring one home for the cause. The leaders of this community, including many of the great bloggers out there, need to wake up and make this happen. We need to both focus attention on the committee(s) involved and on NASA to fight for one of the brightest spots in its otherwise dark future. This isn’t about who does the prizes or competes for them, or even how soon anyone wins, it is about the concept of trying something new with hundreds of years of proven track record, changing how we do space, supporting the fledgling NewSpace industries and movement, and showing that those of us who care about humanity’s future in space is worth fighting for.

I noticed someone posted links to the Appropriations committee and its staffers. Those in the know as to how the machine operates should enlighten their readers, and we all should step up to this one.

I saw Pixel (Armadillo