Why didn't they used the RL-10 in the Apollo CSM ?

[Archibald]

Title says all. I'm just curious. ???
http://www.astronautix.com/craft/apolocsm.htm

 

[Archibald]

Ideas behind this question are the following

- they used Hydrogen for S-II and S-IVB
- hydrogen is a high-energy fuel

 

[Michel Van]

Reason one: Safety
LH2/LOX is a high-energy fuel
so its explode also like that...

Reason two: Boil off
LH2/Lox are super cooled to be liquid.
ones in a Tank the LH2 (hydrogen) start boiled.
and the hydrogen gas has to be vent out
or the Tank explode because of overpressure

so after some days in Space the LH2 tank is empty

of course we can install better Isolation and a Refrigeration unit for Hydrogene
but that increase the mass of spacecraft and so Rocket to launch it.

NASA look for LH2/LOX Apollo proposal
but there were only the edge of possibly technology in that time (1961)
and went save with N2O4/UDMH

IMHO that Save Apollo 13 Crew.
had they LH2/LOX Propellants wen the LOX tank explode
they would be death now...

 

[Archibald]

Thank you! Now do you think it would have been a more viable option in the late 70's, let's say for Apollo follow-ons ?

 

[Michel Van]

it would have been a more viable option in the late 70's, let's say for Apollo follow-ons ?

Yes !
even in 1970 the technology was ready for to get to Moon and land with LH2/LOX (3-4 day)

there were proposal to replace LEM step by step with LH2/LOX tech.
see picture
source "Improved Lunar Cargo and Personnel Delivery Systems," by L. L. Morgan and Rodney W. Johnson
found at Romance to Reality: Moon & mars mission plans
reborn as Altair VI Blog

or as modify S-II for Manned Mars Fly-by
http://altairvi.blogspot.com/2008/01/saturn-v-s-ii-injection-stage-1968.html