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#20
by
Antares
on 21 Feb, 2009 16:15
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Cold gas usually refers to GN2. This would be as opposed to a biprop hypergol system or to a monoprop hydrazine system with a catalyst bed that causes exothermic decomposition.
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)
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#21
by
just-nick
on 21 Feb, 2009 23:40
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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... 
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I found this in the Ariane V user's manual - the reference to 4 GH2 thrusters for roll and four clusters of three GH2 thrusters does imply they are using vented propellant. Though the reference to O2 jets for longitudinal boost seems weird.
From what Jim says, though, the loss of propellant if you intentionally vent for RCS functions has a bigger cost (mass) than bringing along a monoprop system. There is an offhand reference in some documentation on the Vinci development that implies some sort of heat exchanger attached to the propellant vent system. Perhaps warming the vented gas to further pressurize it so you get some meaningful isp out of it?
Anyone know?
--N
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#22
by
just-nick
on 21 Feb, 2009 23:40
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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)
Sounds great to me. Wasn't sure where to start it and it has now taken on an international flavor anyway.
--Nick
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#23
by
Archibald
on 02 Dec, 2010 07:13
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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 ?
thanks in advance...
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#24
by
madscientist197
on 02 Dec, 2010 08:22
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Surely it would have been venting of propellent from the upper stage?
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#25
by
Jim
on 02 Dec, 2010 10:12
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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 ?
It was venting of the propellants through the J-2 that provided the delta V
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#26
by
Danderman
on 11 Jan, 2011 19:24
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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 wasn't uprated to the Apollo service module's 22,000 lbs, since the Delta II 2nd stage seemed puny compared with the first stage?
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#27
by
Jim
on 11 Jan, 2011 23:01
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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?
The thrust for the Aerojet AJ10-118K Transtage derived engine was 10Klb, TRW TR -201 LM derived engine was 9,850 lb.
The SM engine is a different branch of the AJ-10 family -138.
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#28
by
Danderman
on 04 Mar, 2011 15:42
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This not entirely On Topic, but I don't see a place for this type of question: when I look for Pegasus or Taurus stage masses, what is generally given is the motor mass. For example, Pegasus stage is an Orion 38 stage, so what is listed is the Orion 38 mass as given by ATK, but not the avionics ring, payload adapter, separation systems, ACS cold gas system, etc.
Is there a source of information for OSC vehicles that gives actual stage masses, and not the masses of motors as provided by ATK?
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#29
by
Boost
on 04 Mar, 2018 14:34
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Does anyone know why the Saturn-1B AS-209, displayed at the KSCVC Rocket Garden, has no ullage motors ?
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#30
by
Boost
on 04 Mar, 2018 17:24
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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 ?
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#31
by
Jim
on 04 Mar, 2018 20:26
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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 ?
It would have never had them. They are mounted just before going to the pad or at the pad, depending on the pad.
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#32
by
Boost
on 04 Mar, 2018 21:15
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Thank you. Any reason for this unusual process ?
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#33
by
Jim
on 05 Mar, 2018 02:06
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It is a standard process. They are solid motors. There are safety considerations.
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