Larry J said:

>I don't know if a single CEV design would be a good idea for
>orbital, lunar, and Mars missions. There is room for a great deal
>of commonality in some systems and software, and I completely
>support that, but a CEV required for a very short term mission
>to the moon just seems too small for a multi-month Mars mission.
>
>I've heard that one corollary to Occam's Razor is to simplify as
>much as possible, but no further. If there was to be only one
>CEV design for orbital, lunar, and Mars missions, then it makes
>sense that the design be built to the most rigorous
>requirements - Mars.

I suspect this discussion will boil down to a "violent agreement" where we're saying the same thing from different pespectives.

As Larry and others know, the biggest single expense with a spacecraft, aircraft or automobiles is the development cost. The Space Shuttle's operational cost was deliberately made higher because the original development cost was too high. What limit's a Mars return vehicle is its lift-over-drag (L/D) ratio. The lift-over-drag ratio is shape dependent, i.e. a spherical section entry vehicle like the Apollo CM does not have a high enough L/D for Mars return. To reduce development costs, it will be very tempting to just dust off the Apollo CM design, scale it up for a crew of six people and go with that. We would then be locked into a Moon only program with Mars out of the picture. However by spending the extra money and developing a vehicle that could enter at 13 km/sec, we would have a return vehicle that could service the entire inner Solar System. The issue about trip time from Earth to Mars is a red herring. The CEV would be shutdown (in hibernation) during the trip much like the Apollo CM was shutdown during the Skylab missions. The CEV would be reactivated shortly before actual return to Earth.

I would prefer us to skip the Moon and proceed directly to Mars. However an incremental program is possible with a properly designed CEV. We could do Earth orbital missions much like we did with the Apollo CM. We could then do missions out to the Moon and Libration points. Next we could do asteroid missions which could be quite interesting (unlike the Moon). We could do Venus flyby and orbiter missions as proof-of-concept missions in preparation to Mars missions. We could then do Mars missions of various types, e.g. Mars orbiters, Phobos missions, Mars landers, etc. We might even do missions to outer asteroids like Ceres which is darn near the size of a planet. Now compare all of that with an improperly designed CEV. If it is merely a scaled up Apollo CM then we're ripe to do some flags and footprints on the Moon (again). We do a couple missions to the Moon until Hillary or whoever else is President gets bored with it. Then the hardware gets hauled off to the Smithsonian and scrapyards while thousands of aerospace engineers have their careers terminated (again).

Gary