Re: NASAspaceflight.com - Censors the John Young - Ares I Thread.

pstanley55@xxxxxxxxxxx wrote:

there were some important LM changes, notably larger descent-stage tanks and a stretched descent-engine nozzle.

Mr Spencer, what was the reason for larger descent stage tanks? Does
this mean the CM orbitted further away from the moon? what does a "stretched" descent engine nozzle mean, and what are the advantages?

The goal was to get as much additional mass to the lunar surface as
possible.

The extended-stay LM was about 2200 kg heavier than Eagle and Intrepid.
The single largest component of this was the additional propellant in
the enlarged descent stage propellant tanks. The second largest was the
Lunar Rover. A solar power extension package was also considered but
later dropped after the surface stay time was capped at 54 hours. Other
changes included additional batteries, water, LiOH, and oxygen to extend
the surface stay time.

The additional propellant, plus use of the CSM's SPS engine to put the
LM into its descent orbit, allowed a heavier LM to be landed. It also
provided 17 seconds of additional hover time just before landing.

The nozzle extension on the descent stage engine is where the exhaust
gases trade off heat for speed. Stretching the extension increases the
efficiency of the engine by allowing the velocity of the exhaust to
increase just a bit further before it exits the nozzle.

HTH.

--
Dave Michelson
davem@xxxxxxxxxx






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