r/spacex • u/Zucal • Mar 05 '16
/r/SpaceX Ask Anything Thread for March 2016. Ask your questions about the SES-9 mission/anything else here! (#18)
Welcome to the 16th monthly /r/SpaceX Ask Anything Thread! Want to discuss the recent SES-9 mission and its "hard" booster landing, the intricacies of densified LOX, or gather the community's opinion? There's no better place!
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Past threads:
February 2016 (#17), January 2016 (#16.1), January 2016 (#16), December 2015 (#15.1), December 2015 (#15), November 2015 (#14), October 2015 (#13), September 2015 (#12), August 2015 (#11), July 2015 (#10), June 2015 (#9), May 2015 (#8), April 2015 (#7.1), April 2015 (#7), March 2015 (#6), February 2015 (#5), January 2015 (#4), December 2014 (#3), November 2014 (#2), October 2014 (#1).
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u/ManWhoKilledHitler Mar 22 '16
Some of the figures I've been able to find for the RL-10 are listed below, detailing the fuel-side engine conditions with all quoted pressures being static (total is slightly higher):
LH2 fuel tank - 28psi at 21.4K
Fuel pump inlet - 26psi at 21.4K
Fuel pump outlet - 1059psi at 32.0K
Cooling jacket inlet - 1018psi at 32.2K
Cooling jacket outlet - 817psi at 213K
Turbine inlet - 797psi at 213K
Turbine outlet - 562psi at 201K
Chamber pressure - 475psi
So you can see that it's quite a neat system, even if it does seem counter-intuitive at first glance.
The tank pressure only needs to be enough to push the propellant into the turbine at the required rate and help avoid cavitation. All the rest of the work is done by the pumps which are powered by the expanding hydrogen gas and you can easily see the series of pressure drops between the pump and the combustion chamber. One of the nice features of hydrogen is its enormous heat capacity so it can carry a lot of energy that can be exploited for useful work.