Which Saturn V manual are you referring to?F=ma
Atlas V uses retro rockets and Delta Iv uses push off springs to achieve separation. Both use settling thrusters/jets that basically fire constantly during coast for prop management. This keeps the liquids stable and keep them away from the pressure relief valves.Ullage rockets are seldom used
Quote from: Fequalsma on 02/15/2009 02:52 amWhich Saturn V manual are you referring to?F=maTruly a thing of wonder:http://history.nasa.gov/ap08fj/pdf/sa503-flightmanual.pdf --Nick
Nothing but a name thing... Comparing SIV-B to Delta and Centuar they all use the same pitch/yaw/roll control thrusters to provide axial thrust prior to engine start to force the propellant liquid to settle at the bottom of the tank prior to engine start. SII had single shot solids to due the same, but that's because it didn't have either spaceflight control thrusters or the need to restart.
Atlas V uses retro rockets and Delta Iv uses push off springs to achieve separation. Both use settling thrusters/jets that basically fire constantly during coast for prop management. This keeps the liquids stable and keep them away from the pressure relief valves.
The latest generation of upper stages seem to use comparatively tiny thrusters to settle propellants -- which I can understand after a long coast when things have had a chance to reach a steady state condition -- but right after the acceleration of stage one the sudden deceleration from residual atmospheric drag, jolting of springs and pyros, and with just a few little monopropellant puffers, it surprises me that all the fluids are where they need to be.Are there other tricks?
Got to disagree with you on that... While I'm not very familar with Centaur I know that DCSS vents both LO2 and LH2 during coast from propellenat conditioning. The LO2 vents thru a non-propulsive vent, but the LH2 vents thru a propulsive vent.From DIV Planner's Guide: "Propellants are managed during coast by directing hydrogen boil-off through aft-facing thrusters to provide settling thrust, and by the use of the ACS, as required."
Thanks. Here's an interesting paper that I found that relates to the D-IV and slosh management.http://sloshcentral.bbbeard.org/Refs/DeltaIVLaunchVehicle_PulseSettlingFinalPaper.pdfA big realization for me has been the idea that "continuous venting" isn't REALLY continuous. It is just a matter of capturing a little settling power out of the venting that you've got to do anyway.
Thanks. Here's an interesting paper that I found that relates to the D-IV and slosh management.http://sloshcentral.bbbeard.org/Refs/DeltaIVLaunchVehicle_PulseSettlingFinalPaper.pdfA big realization for me has been the idea that "continuous venting" isn't REALLY continuous. It is just a matter of capturing a little settling power out of the venting that you've got to do anyway.On another note -- how is the Ariane's ACS and settling system put together? Didn't the Ariane IV's 4th stage use a GH2 system? I assume that's not at tank pressure (super low isp) so how's that work, then? And what about the ECA and ECB?Thanks, --N
WRT Ariane, I have heard reference to "cold gas thrusters" during their webcasts so I assume it is vented propellant on the ECA versions. I don't know about the others (and I don't want to go too far off topic... )
BTW, this is a pretty good thread for the Q&A section. Anyone mind if I flag it for relocation over there? (or a mod can do it without me flagging it)
A question for all experts here... After the CSM-LM got away from the S-IVB, the spent stage ullage motors fired for a last time to move the large rocket body out of the way (either in heliocentric orbit or on a collision course to the Moon) Does anybody know how much delta-V did the solid-fuel ullage motor provided to the S-IVB ?
During the 1980s, the Delta II upper (second) stage was uprated to some 10,000 lbs (heritage from the Apollo LM). The question is why the stage was uprated to the Apollo service module's 22,000 lbs, since the Delta II 2nd stage seemed puny compared with the first stage?
To be more precise, is it by design on the booster or did this model have those ullage engines some time in the past and had it removed for some reason ?