On Sept. 19 NASA AdministratorMike Griffin revealed the agency's new plan for implementing the president'sVision for Space Exploration.
The plan has significant positiveand negative features.
On the positive side, it recognizesthe need for the development of a true heavy-lift launch vehicle (HLV),and takes concrete steps to preserve the shuttle industrial infrastructurenecessary to produce such a vehicle. It does this by initiating development ofa medium-lift launch vehicle using shuttle technology.
The importance of this cannot beoveremphasized. An HLV is absolutely necessary to enable human exploration ofthe Moon or Mars, and it was a measure of former NASA Administrator SeanO'Keefe's unfitness for his position that he was willing to promote a clearlyunworkable quadruple launch/quadruple rendezvous lunar architecture for thepurpose of justifying the abandonment of that capability. Dr. Griffin hasreversed that position and backed his policy with action, and that isexcellent.
Another strong feature of the planis its decision to develop and employ a methane/oxygen rocket engine for Lunarascent. Methane/oxygen is a far more storable propellant combination thanhydrogen/oxygen and offers much better performance than conventional hypergols,making it a much better choice than either for lunar ascent and returnpropulsion.
More importantly, however,methane/oxygen is the easiest propellant combination to synthesize out of theMartian atmosphere, and some could be made out of lunar base waste products aswell. The choice of this propellant therefore shows good system engineeringsense with thoughtful consideration of the best way to select Lunar missiontechnologies that will be most useful in enabling human exploration of Mars as well.
On the more problematic side is thedecision to develop such a large Crew Exploration Vehicle (CEV). While a largeCEV certainly enables larger crews and greater comfort, it will cost more todevelop, produce and launch than a smaller capsule. Furthermore, becauseof its excessive mass, the large CEV makes direct return lunar missionsimpossible, thus mandating a lunar orbit rendezvous mission architecture. This,in turn, will require the costly development and production of lunar excursionmodules, and impose return rendezvous phasing complications that couldhamstring the operations of a lunar base, especially if surface stays greaterthan two weeks are desired.
Another cause for concern is thedecision to launch the CEV after the HLV delivers the rest of the missioncomponents to orbit. The HLV's cargo will include stages employing cryogenicliquid hydrogen/oxygen propellant, and this propellant will start to boil awayimmediately after launch. Thus for the mission to succeed, the CEV must belaunched on time, within a few weeks at most of the prior flight, without fail.
Otherwise, the billion-dollar classHLV launch and cargo will have to be written off. This situation will put greatpressure on managers to launch despite warnings, thereby putting crews at risk.Moreover, NASA's record of achieving on-time crewed launch to date is verypoor. Unless it is radically improved, this aspect of the plan will have to beabandoned.
That said, the plan is an enormousimprovement over its predecessors. One only has to compare it to thepsychedelic NASA mission architecture of 2002, which called for supportingLunar exploration from a LaGrange point space station supplied by giant cyclingnuclear electric spaceships, or the nonsensical O'Keefe quadruple-launch/quadruplerendezvous lunar mission plan of 2004, in order to breathe a huge sigh ofrelief.
The previous NASA plans were purenonsense. This one is real engineering. Finally, we have a plan that couldactually work.
There is, however, a deeper problemwith the plan than the engineering concerns noted above. That is, that whilepreserving the HLV infrastructure, the plan relegates the development of an HLVto a subsequent administration. In consequence, for the next 13 years, NASAwill continue to send crew after crew up and down to low Earth orbit, at a costof some $70 billion, for no justifiable purpose whatsoever.
Both Adm. Harold Gehman, thechairman of the Columbia Accident Investigation Board, and Dr. Griffin havemade the point that if we are to accept the costs and risks of humanspaceflight, we should be undertaking missions that are worthy of those costsand risks. But for the next 13 years, we will continue not do so.
To paraphrase St. Augustine, NASA isnow saying "Lord, make me a destination-driven space agency, but not yet."
In saying this NASA is, infact, acting in accord with the Bush Vision for Space Exploration, asenunciated in January 2004. That policy however, was formulated by a WhiteHouse which lacked a competent NASA administrator to advise it. Now, however,that we have a qualified NASA administrator, this policy needs to be revisitedand reformulated.
Let us review the consequences ofblindly following the mediocre vision scriptural document of January 2004.
That document was a compromisebetween those who wanted a destination-driven space program, and those who didnot. Therefore, in accord with the bargain reached, NASA would be allowed tocontinue to fly shuttle missions for the rest of the decade, after which thedestination driven program could begin.
But does this make any sense? Theonly really time-critical shuttle mission is Hubble Space Telescope repair.This is indeed a truly important mission, and it should be flown with dispatch,as it is without question worthy of the 2-percent risk to crew that any shuttlemission must entail. But the rest of the shuttle manifest is devoted to spacestation construction, and these cargos could be delivered much moreexpeditiously by the HLV that NASA needs to develop to reach the Moon anyway.
Griffin's HLV design will be able to deliver 125 metric tonsto low Earth orbit. The shuttle can only deliver 20 tons. With a single launchthen, the HLV will be able to deliver as much payload as the shuttle programcan during a year -- and that's during a good year.
Compared to current shuttle launchrates, which will have managed only one flight between February 2003 andFebruary 2006, (at a cost of $15 billion), the HLV will be able to launch in anafternoon everything the shuttle program would be able to launch for the next18 years.
Operating the shuttle program forthe next five or six years to deliver a few space station payloads early willcost us $30 billion. All that money could be saved simply by shutting theshuttle down after Hubble repair, and shifting the shuttle program funds overto immediate development of the HLV and the other Lunar exploration hardwareelements. We could then use the HLV to complete the space station and reach theMoon by 2012 instead of 2018.
In the wake of Hurricane Katrina andthe financial burdens it will impose on the nation, gratuitously wasting $30billion of the taxpayers' money in order to dogmatically fulfill an oldscriptural document is unacceptable. The new NASA architecture is a good planfor implementing a flawed policy. We need a good policy. We have real talent atNASA now, and we should make use of it to revise the policy itself.
Robert Zubrin, an astronautical engineer, is president ofthe Mars Society (http://www.marssociety.org), and author of The Case for Mars (Simon and Schuster, 1996), Entering Space (Tarcher Putnam, 1999), and Mars on Earth (Tarcher Penguin, 2005).
NOTE: The views of this article are the author's and do not reflect the policies of the National Space Society.
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