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Originally Posted by Cugel
Gaetanomarano,
Although I have doubts about the VSE launch architecture myself, I have to say that the above calculations are completely irrelevant. Basically, to reach an orbiting outpost in LEO the launch window is 24 hours a day. That is because there is plenty of room for manouvering once you are in orbit. For instance, you could bring the CEV in a slightly higher orbit and let the LSAM catch up with you. Of course, all this takes a bit of fuel (delta-V), but I have no doubt the CEV and its booster will be designed to cope with this sort of situations.
Another thing I would like to note is that by using a SRB as first stage for the CEV booster (CLV) the total complexity of the system is drastically reduced. Most of the delays and problems we have with current big boosters come from the enormous amounts of cryogenic fuel that have to be stored and maintained. The CLV only has (relatively) small cryogenic fuel tanks in its second stage, so theoretically, it could be a pretty reliable 'easy' booster.
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CEV fuel... it can be used for an
orbital mission not for a lunar mission because it will need for the (very important!)
lunar orbit departure...
You can add more fuel to have a larger rendez-vous tolerance, but more fuel (that don't increase so much the time available) means a bigger CLV (in recent news I've read that a 5-segSRB+oneJ2X configuration is so critic that the CEV will need part of the SM fuel or the LAS to reach the orbit!!!)
With the figures planned for the CEV/CLV the fuel use will be very critic in a moon mission.
If too much fuel will be used to reach the LSAM/EDS, the mission will fail because the SM will not have sufficient fuel to come back from lunar orbit...
SRB... I'm not sure that a NEW 5-segment SRB (with many many changes) will be reliable only "because the Shuttles' SRBs was reliable".
But the main problem is that the second launch is not only an SRB, it will be a
very complex machine (made of 1st stage, 2nd stage, interstage, LAS, SM and CEV) with
thousands parts and sensors and
ALL very
NEW and
EXPERIMENTAL.
I don't say that the missions will fail due to an SRB or CEV failure, but only for a
"sum of (many) simple (and stupid) delays".
If you see how many delays will happen with to-day's reliable, well known, simpler (than CLV/CEV) launches (with rockets launched dozens times), you can easy imagine how many delays will happen with a
completely new rocket, a
few launches of experience and a capsule
with four astronauts on the top...