Vision For Space Exploration Facing Critical Juncture
Honolulu HI (SPX) Apr 12, 2006
Another space news website - NASA Space Flight has published a leaked NASA study called "LRA-0
" which is spreading despair and gloom through the space community. Many people are surprised that the architecture for returning men to the Moon laid out in the famous ESAS report is declared to be totally unworkable in this new document.
[Editor's Note: an update to this report has been publisher here] But no one should be surprised. I pointed this out four months ago, and anyone who has followed the announced and rumored changes to the ESAS plan since its appearance could see that it was in serious trouble.
The 723-page ESAS report went to elaborate lengths to justify its particular choices of spacecraft, boosters, engines, and fuels. Many of these justifications were obviously phony. (My favorite was a long table of expensive modifications that would supposedly be needed to "man-rate" the Delta-4H or Atlas-5H.)
It was clear to many astute observers that the ESAS program was a political one. It was designed to mollify Congress by keeping almost every worker in the dying Space Shuttle program in his present job, performing the same task in the same factory in the same politician's district.
Little attention was given to financial or technical feasibility. Cost and schedule estimates by Shuttle contractors were accepted without any attempt to check them (even though those contractor estimates have proven wildly optimistic in the past).
So it was inevitable that once Congress was on board many of those politically optimum choices would be changed. NASA has adopted or studied numerous options that were "considered" and rejected by ESAS.
The LRA-0 presentation provides a compressed summary of these changes and the reasons why they are under consideration. The problems that have appeared with the ESAS plan are basically the same ones I identified four months ago:
Unfortunatly, every change intended to solve one of these problems has made at least one of the others worse.
The use of LCH4 in the CEV and LSAM ascent stage had to be dropped because of the 6-month space storage requirement for these modules. Methane is significantly harder to keep liquid than LOX, and over 180 days on or near the Moon much of it would boil off due to heating of the tanks by sunlight.
So NASA was forced to adopt traditional storable NTO/MMH propellants. These have lower ISP than LO2/LCH4 and exacerbate the weight problem. The reduction of the CEV's diameter from 5.5m to 5.0m was intended to compensate for this weight increase - but apparently has not.
The air-start SSME planned for Stage 2 of the CLV presented serious technical challenges, so it was replaced by the old J-2. To make up the lost performance and/or increased CEV weight, Stage 1 was changed from the existing 4-segment SRB to a new 5-segment SRB. This increased the projected development cost from ~$1B to ~$3B.
Mike Griffin is reportedly dissatisfied with the high refurbishment costs of the SRBs and is considering making the new version expendable to reduce operating costs - the same reason given 35 years ago for making them refurbishable!
The vast expense involved in dropping 5 SSMEs to the sea bottom on each mission has led to consideration of using the cheaper RS-68 in the CaLV core stage. This change would reduce operating costs, but increase the weight and reduce the ISP.
The CaLV core cannot be lengthened to restore performance because the total stack height is already near the VAB door clearance. If it is made thicker it can no longer be produced with the old Shuttle ET tooling in New Orleans.
The EOR mission architecture leaves the LSAM and EDS in Earth orbit waiting for the CEV to launch. In January, the loiter time requirement for both these modules was increased from 25 days to 95 days. Both EDS and the LSAM descent stage use LH2 fuel, which is even harder to store in space than methane.
Extra fuel might be included to allow for boiloff. But if by some miracle the CEV's countdown goes perfectly and it actually does launch on schedule, these stages will have too much LH2 and the surplus must either be carried to the moon or dumped by a "Thermodynamic Vent System" before the TLI burn (with complications to the navigation).
The LRA-0 report assumes the use of as many as 140 layers of aluminized Mylar on the LH2 tanks. Each of these layers would have to be installed and inspected separately, by highly paid technicians. And these tanks are not small.
The cost of using this superinsulation would be huge. (The presentation doesn't consider a third option of including a small reliquification plant, probably because the power and weight demands are excessive).
It is no exaggeration to say that the original ESAS plan now lies in ruins. There is virtually nothing left of the original claims of low development cost and high inheritance from Shuttle.
The authors of LRA-0 propose two main options for salvaging the program which both have the smell of desperation about them. One of them completely undercuts the supposed justifications for the program.
The L2-rendevous scenario is unattractive from a safety standpoint. The crew transfers to the LSAM soon after TLI and rides out to the Moon in the lander, while the unmanned CEV goes further out to L2.
The astronauts are a long way away from their only ride home if anything goes wrong. Furthermore, the return flight Moon-lunar orbit-L2-Earth lasts an extra 6 days which considerably increases the risk of the crew being fried by a solar flare.
The "Wal-Mart Lander" option is even more unacceptable. This vehicle is massively scaled down from the original LSAM. It has no airlock, carries only two astronauts instead of four and 500kg of science gear instead of 2300kg. Even worse, it is limited to landing near the lunar equator. It cannot explore the possible polar ice deposits.
This change would be a poison pill for the program, because then it really would be little different from Apollo. Critics who have derided the LSAS plan as "Apollo Redo" or "Back to the Future" would be vindicated. Political support would vanish overnight. What would be the point of repeating a project we already did 50 years before?
It seems that only major changes in the ESAS architecture can save this program. Here is what we should look for in a possible "VSE Get-Well Program":
In this plan development costs are reduced, commonality with Shuttle is increased, but operations costs are likely to be as high or even higher than in the ESAS plan. But there really isn't any way around this.
The LRA-0 report just makes official what I've been telling you all along: There's no free lunch in space. There isn't any magic technology or management trick that will make it possible to fly double-Apollo missions on a half-Apollo budget. As long as we use throw-away vehicles powered by rocket engines, space travel will be extremely expensive. If we aren't willing to pay for a real space program, we should get out of the game and stop wasting our money.
Jeffrey F. Bell is a former space scientist and recovering pro-space activist.
Power Point Package of Lunar Architecture LRA-0 Trade Summary
ZIP Package of JPG Slides of Lunar Architecture LRA-0 Trade Summary
The Vision at NASA
NASA Says False Documents Behind Recent Lunar Study Article
Honolulu HI (SPX) Apr 14, 2006
The internet news site NASASpaceflight.com has withdrawn it's article and supporting NASA documents upon which I based my recent article on the crisis facing the Vision for Space Exploration - apparently at the request of an unnamed NASA official.
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2006 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA PortalReports are copyright European Space Agency. All NASA sourced material is public domain. Additionalcopyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement