Can someone tell me why LOX cooled kerolox ORSC engine has never been proposed by Aerojet Rocket dyne even after end of the cold war and availability of the RD180 which clearly shows the potential of an high ISP and thrust US indigenous engine? Switching to LOX cooling would completely eliminate the coking problem of RP-1.
Quote from: fl1034 on 12/25/2019 12:43 pmCan someone tell me why LOX cooled kerolox ORSC engine has never been proposed by Aerojet Rocket dyne even after end of the cold war and availability of the RD180 which clearly shows the potential of an high ISP and thrust US indigenous engine? Switching to LOX cooling would completely eliminate the coking problem of RP-1.It has. The AR1 is an ORSC engine proposed for use in Vulcan. They choose BE4 instead and AR1 may potentially be used in Firefly Beta in the future.https://en.m.wikipedia.org/wiki/AR1
Well, why not LOX cooling? Splitting the usual coaxial shaft pump of the kerolox engine into 2, use LOX and LOX only for regen cooling, adjust the fuel side preburner temperature, then you get completely independent mixture ratio control, no coking to worry about, much easier pumps to design, and the ability to use from methane all the way to kerosene or even diesel for fuel. Just saying.
The obvious concern - which may not be relevant, but still - is well, it’s LOX. It’s comparatively *very* nasty, even cold,
and is going to introduce new material requirements in the cooling channels. I would be interested to hear livingjw on this topic.
All good facts, but then: wasn't the SSME the first choice for Aries I Upper Stage?
Didn't the people who pushed the SSME for the Upper Stage know this?
How were they going to deal with this?
Quote from: darkenfast on 09/06/2017 06:14 amAll good facts, but then: wasn't the SSME the first choice for Aries I Upper Stage? IIRC both design teams had it as their US engine.Quote from: darkenfastDidn't the people who pushed the SSME for the Upper Stage know this? Well you'd think so but actually Rocketdyne was asked a similar question in the early 90's (IIRC) and said it wouldn't be a problem. IIRC it's mostly the augmented spark ignitors that didn't have enough flow. Quote from: darkenfastHow were they going to deal with this?Well they'd been told it wasn't a problem.You might think with both designs relying on the SSME doing a start in space that NASA would have either a) Request the teams demonstrate this or b)Scheduled some stand time on a altitude test stand to verify it.But they did neither. It's been noted before that NASA is much more willing that the DoD to go ahead with ideas with much lower levels of proof that they will even work. I'm not sure how many $Bn were spent before this issue was finally "discovered."
Quote from: john smith 19 on 12/28/2019 01:26 pmQuote from: darkenfast on 09/06/2017 06:14 amAll good facts, but then: wasn't the SSME the first choice for Aries I Upper Stage? IIRC both design teams had it as their US engine.Quote from: darkenfastDidn't the people who pushed the SSME for the Upper Stage know this? Well you'd think so but actually Rocketdyne was asked a similar question in the early 90's (IIRC) and said it wouldn't be a problem. IIRC it's mostly the augmented spark ignitors that didn't have enough flow. Quote from: darkenfastHow were they going to deal with this?Well they'd been told it wasn't a problem.You might think with both designs relying on the SSME doing a start in space that NASA would have either a) Request the teams demonstrate this or b)Scheduled some stand time on a altitude test stand to verify it.But they did neither. It's been noted before that NASA is much more willing that the DoD to go ahead with ideas with much lower levels of proof that they will even work. I'm not sure how many $Bn were spent before this issue was finally "discovered." Wasn't the main issue lack of pressure head in freefall after staging? I'm curious why they didn't opt for large solid ullage motors, or hot staging, as those would provide the acceleration needed for a pressure head.
Airstarting the SSME after staging wasn't the problem, it was re-starting it for the TLI burn. NASA wanted a common engine for both the Ares I and Ares V upper stages so when they ran into the problem of getting a good re-start of the SSME on the Ares V upper stage, they decided it wasn't worth expending the resources into making it re-startable in flight and went with the J-2X as the upper stage engine on both LVs. This had the cascade effect of making the Ares I upper stage unable to insert the CEV into orbit which forced them to not only upsizing the upper stage but the booster stage as well (was derivative of the STS SRB but became a brand new five segment version with no flight history).
But surely, say, Merlin 1D - which has got to have a quick and deep throttle to land - how is that done?
What are the challenges around designing an electric pump engine similar to the Rutherford or Stealth Space/Astra’s engine? How much complexity & cost does it add over a pressure fed system? Asking as a member of a student team that has successfully built and tested a N2O/Kerosene pressure fed engine.
Quote from: nicp on 01/03/2020 09:26 pmBut surely, say, Merlin 1D - which has got to have a quick and deep throttle to land - how is that done?It isn't.F9 takes off on 9 engines then lands on 1.That alone deals with most of the "deep" throttling problem. A Merlin at 50% thrust (a fairly shallow throttle providing your nozzle expansion ratio is not extreme) has 1/18 of an F9's take off thrust.
... Could multiple engine sets feed into one bell to save space? What I conceived was a compound shaped bell with three lobes that had an exit area close to the exit area of three standard engines. ...
If one of your three combustion chambers suffers a failure, then you have severely unbalanced pressure inside the bell. It would likely deform or suffer from flow separation on the faulty side. You'd have to shut all three chambers down to avoid further damage. This reduces engine-out capability