Chair Force Engineer

Thursday, March 01, 2007

Team Vision (Part 3 of 5)

Era 3 of the TeamVision proposal finally lands humans on the moon. This is where the underlying assumptions of TeamVision start to get shaky.

Previously, TeamVision called for the development of the shuttle-derived Jupiter I booster to enable robotic lunar rovers and human missions to lunar orbit. The firm calls for the development of a "Jupiter II" booster for the human lunar landing missions in Era 3. The problem I see is that Jupiter II has very little in common with Jupiter I. The 5m Integrated Common Evolved Stage now becomes a 10m rocket stage for the Jupiter II. The new rocket requires the development of 5-segment solid rocket boosters and three new, liquid-fueled stages: one powered by five RS-68's, one powered by two J-2X's, and one powered by an RL-60.

So TeamVision is proposing a new launch pad and umbilical tower, new tankage, new SRB's, and development of two engines (J-2X and RL-60) that only exist on paper, as far as I can discern. The fact that three stages (plus the SRB's) are needed to reach low earth orbit is a bit too complex for my tastes; I feel that three stages in total is an optimum balance between performance and complexity. Also worth noting is that the separation plane between the first and second stages is also the same place where the carry-through beam connects the forward attach points of the two SRB's.

To their credit, TeamVision has come up with a launch vehicle that can put 178 mT into low earth orbit. Why build a rocket even more powerful than the Ares V design? Because TeamVision believes that the Block III Orion CSM should make a direct landing and ascent on the moon. The direct approach is heavier than lunar orbit rendezvous. I also believe that it sacrifices the potential for reusability in the future. The reason is because the Orion CSM will need a "lunar crasher stage" in order to de-orbit and provide propulsion for most of the descent phase. In the TeamVision plan, the lunar crasher is based on Jupiter I's 5m upper stage, but with an RL-60 main engine. The stage is then discarded just prior to landing, in order to keep the lander at a reasonable height (otherwise, imagine a pilot trying to land an Atlas missile, partially loaded with propellant, directly on its tail.) This is one of the reasons why I support a rendezvous at the earth-moon L1 point instead of direct landing and ascent.

There are some good features of TeamVision's Era 3 proposal. The most compelling argument for direct landing and ascent is that a separate lunar lander doesn't need to be developed. The problem of having a pilot steer the capsule to a landing is solved by having the pilot stand vertically in the command module, staring out through a viewing dome installed in place of the docking module. Finally, TeamVision believes that NASA's proposed crew size is too big; all of the science objectives can be accomplished by a crew of two (plus robot rovers) working for seven days on the lunar surface. This begs the question of "If we only need a crew of two, why do we have to make the Orion command module bigger than the Apollo command module?" I think that NASA has a responsibility to give taxpayers a good and coherent answer to this stumper.

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