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More Non-Defense Defense

Like Steve Cooke, Dave King defends ESAS/Ares:

Direct 2.0, the concept in question in the June 23 Times article, falls significantly short of the lunar lander performance requirement for exploration missions as specifically outlined in Constellation Program ground rules. The concept also overshoots the requirements for early missions to the International Space Station in the coming decade. These shortcomings would necessitate rushed development of a more expensive launch system with too little capability in the long run, and would actually increase the gap between space shuttle retirement and development of a new vehicle. Even more importantly, the Ares approach offers a much greater margin of crew safety - paramount to every mission NASA puts into space.


To accomplish the nation's goals in space, we need more than a new rocket. We need a robust, multipurpose space fleet.

Again, this is all simply argument by assertion. Show us the numbers and the assumptions. The notion that Direct 2.0 falls short of the lunar lander performance requirement is pretty funny, considering that Ares 5 does as well. This makes one think that there may be a problem with the requirement. The second paragraph is semantically meaningless. Is he saying that Direct is "a rocket" but that Ares 1 and 5 are a "fleet"? Why is Direct not multi-purpose? In what way is Ares "robust" that Direct is not?

Not that I'm a big Direct fan, of course. A lot of these issues would be solved by simply coming up with an architecture and operating philosophy that allows the use of existing vehicles, something that was clearly never under consideration.

 
 

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9 Comments

brian d wrote:

Stop with the ďDirectĒ already, itís been debunked by me and others. The ET cannot handle the stress of having the payload on top. The compression load is way too much.

If someone wants to argue that building a completely new core (that looks something like the Shuttle ET) and using the current solids is a good design for a rocket, then fine, but ďDirectĒ does not reuse the ET.

And donít assume I like the Ares rocket just because I know that ďDirectĒ wonít work as sketched in the cartoons.

K wrote:

Man, reading the space development news has never been more depressing.

Rand Simberg wrote:

The ET cannot handle the stress of having the payload on top. The compression load is way too much.

Oh, please.

The ET can carry a million and a half pounds of LOX on top, but it can't handle a few more tens of thousands of pounds of payload?

Do you have any analysis to support this nonsense?

brian d wrote:

Supporting something inside the structure i.e. LOX is completely different than stacking it on top. All the load paths for this concept are different than Shuttle; itís a brand new core.

"Do you have any analysis to support this nonsense?"

I donít personally, but NASA showed the analysis to some supporters of Direct. I have also discussed the matter with the ET structural analysts, and they agree. Finally I pointed this out to one of the proponents of Direct who admitted that he hadnít even given that problem a thought and that I was probably right. He ended with; well at least youíd be able to reuse much of the GSE, which is true. Besides, what a ridiculous question I donít have the obligation to prove a negative; you must have the analysis to prove it will work?

brian d wrote:

And besides, itís not a few tens of thousands of pounds, according to the web site itís 250,000lb. Since youíre accelerating at 2gs or so, itís really a half a million pounds. Hardly something to just ignore.

Rand Simberg wrote:

Supporting something inside the structure i.e. LOX is completely different than stacking it on top.

No, from the standpoint of the ET structure itself, it is exactly the same. It just means replacing the ogive at the top with a payload interface to carry the loads through.

...itís not a few tens of thousands of pounds, according to the web site itís 250,000lb. Since youíre accelerating at 2gs or so, itís really a half a million pounds.

OK, at liftoff, it adds a little over ten percent of the weight of the LOX tank. As it accelerates, it approaches about half the weight of the LOX tanks, but by the time it gets to a three-g level, the LOX tank is largely depleted (otherwise it wouldn't be capable of accelerating that fast).

We looked at many Shuttle-derived concepts in the eighties, some of which were in-line with the payload on top of the ET, in this payload class. This was never identified as an issue. The loads between a payload and the LOX tanks are not different. In both cases they are carried from the top down through the barrel sections of the ET. It's actually easier with an in-line configuration, because you don't have the asymmetric loads from the Orbiter and SRB attach points. The ET is structurally overdesigned for this vehicle concept.

Again, show me the analysis.

Louis Archuleta wrote:

NASA needs to look at another concept for asustained return to the moon. I propose taking one orbiter vehicle and modifying it to be a Earth orbit-to-moon shuttle.
To accomplish this the wings, landing gear, and thermal protection system can be removed from the vehicle, new RS-88 engines added, along with a compartment located in the cargo bay for additional crew. A landing/storage pad could be built onto and inside the cargo bay for a lunar lander. It would be neccesary to launch several ET's for fuel storage into Earth orbit along with a fuel transfer facility to transfer LOX and LH2 to an ET permanently attached to the shuttle body. For crew protection from cosmic rays and solar flares the entire crew ares can be coated with ten feet of borated water ice and covered with a thin aluminum structure to keep the ice from sublimating and melting on the sunlit side. The electronics would need upgrading to modern standards.
This configuration will serve to transfer crews to and from the moon with a larger crew than the "Aries" concept. The new heavy lifter could ferry supplies to the lunar vicinity and the four man crew capsule could be used only for getting the crews into earth orbit and home.
Why waste our shuttles in some museum on earth when the lifetime of the vehicles is nowhere even close to being at an end. The stresses of lunar travel are not even close to liftoff from earth. The solutions to earth/moon travel are merely engineering problems that we have solved or will solve in the near future.
My background was as a designer/engineer for the ground support equipment for the shuttle launch facility at Vandenberg Air Force Base Space Launch Complex Six back in the eighties until the Challenger accident shut us down.
NASA needs to pull it's collective head from between it's cheeks and take an unbiased look at the re-use of our shuttle fleet.

David, if ESAS was so great why donít you release ESAS Appendix 6a-f?

Oh thatís right because it contains detailed cost and performance numbers of all the RS-68 powered designs you guys eliminated from showing us mere mortals in the publicly released ESAS report. I mean after all the SSME were clearly the way to go then but not now.

Good thing you guys got rid of the DIRECT concept by taking out those pesky RS-68 engines only to add them back into the new baseline plan before the ink was even dry on the public ESAS report.

As soon as you want to actually debate this issue using real numbers instead of platitudes let me know. Iíll even let you use your own numbers just to make it fair.

BTW, the tank is fine for the Jupiter-120 and just needs a few gage changes for the Jupiter-232. Already checked already confirmed fine. Remember F=ma and both m and a is changing throughout the ascent and three RS-68 engines burn propellant 50% faster than three SSME. The bigger deal is the bending moment needed for steering but that is fine as well.

If you have any real tank concerns maybe you should look at the Ares-I interstage. Ask NASA why they had a structural failure on the exceedingly heavy design they thought was more than safe for the Ares-IX admiral test.

Habitat Hermit wrote:

I feel pretty sure this kind of duplicity that NASA has been engaging in won't survive McCain's freeze'n'review. I'm putting it mildly since the ESAS mess could so easily be far worse than anything Boeing has ever done.

Is it the FBI which handles investigating suspected criminal activity in US agencies?

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This page contains a single entry by Rand Simberg published on June 30, 2008 11:17 AM.

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