Author Topic: Rocket Engine Q&A  (Read 242894 times)

Offline kneecaps

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Re: Rocket Engine Q&A
« Reply #80 on: 09/08/2009 04:06 PM »
Thanks for the excellent input guys. I'll put Sutton's on my X-mas list and hope I won't need a Doctorate in Physics to glean a few nuggets.

Plenty of good information in Sutton even if you don't understand all the math, you'll certainly gain insight into things.
Allow subject to scream. In space no one will hear.

Offline Propforce

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Re: Rocket Engine Q&A
« Reply #81 on: 09/08/2009 05:45 PM »
I came across the RL-10 based CECE and wondered if it could eventually be tested on the X-37B or is that way to big of an engine for possible testing?


CECE - check out the video!
http://www.nasa.gov/mission_pages/constellation/news/cece.html

X-37B's AR2-3
http://www.astronautix.com/engines/ar23.htm

Too big.  X-37 is just a spacecraft

Also, X-37 no longer uses the AR2-3.


Offline Propforce

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Re: Rocket Engine Q&A
« Reply #82 on: 09/08/2009 06:08 PM »
If Ares I had an airstart SSME it wouldn't be taking the heat is is. Fair assessment?

If so, how much of a showstopper was this really? Is it technically extremely difficult? Too expensive? Or both? If Nasa wanted Ares I bad enough I would think they would push forward to a solution.

Ares I would taken less heat if it had an airstart SSME.

For one, it would not needed to spend $1B for a brand new J-2X, plus it wouldn't had to spend an additional $1B to put an extra seg.ment (20%) on the existing Shuttle SRB.  That's a wopping $2B impact that Mike Griffin had not counted on. 

Also, a 4-segment SRB would have less of Thrust Oscillation issue (different structural natural frequency plus a lower magnitude of oscillation). 

One had to ask NASA if it was worth to spend the extra money, plus the engineering effort (time & money) on TO, just to avoid an SSME 'upgrade' to an expendable air-startable RS-25

But the contractors are not asking any questions as they are happy.  Rocketdyne got a new $1B engine development contract.  ATK got a $1B SRB development contract, plus $X hundreds of Millions on TO problem solving and isolator development.  Both Boeing & LM are happy because they get 'extension' on their deliverable schedule on Ares I Upper Stage and the Orion.

How much does it take to upgrade SSME to an air-startable RS-25?  Can NASA use that extra $2.X Billion budget if it didn't need to develop a J-2X and a FSB?  It is certainly interesting to ask if, had someone done some upfront trade study & cost analysis, would MSFC still gets an black eye on the Ares I design? 

Quote
What specifically is the sticking point in the engine that stopped progress?
I know it's a fine tuned hotrod but I would think they could come up with something between J2X and airstart SSME?

Also, could anyone suggest an excellent modern book on engines for the layperson?

That would be the "Modern Design of Liquid Rocket Engines" by Huang & Huzel from AIAA.  Both authors worked at Rocketdyne for sometime and it provides great insights on the design of pump-fed liquid rocket engines.




Offline Propforce

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Re: Rocket Engine Q&A
« Reply #83 on: 09/08/2009 06:12 PM »

I think it would be VERY hard to change the SSME to airstart.  I am certain the design relies heavily on head pressure at the pumps due to gravity during the start sequence......

Is it $1 BILLION dollar hard?   ::)


Offline Danny Dot

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Re: Rocket Engine Q&A
« Reply #84 on: 09/08/2009 06:13 PM »
On Airstarting an SSME, ESAS mentions a NAS8- paper that I have found.  It also mentions a 2004 Marshal paper on looking at airstarting an SSME.  Can someone find and post?

Danny Deger
Danny Deger

Offline Jorge

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Re: Rocket Engine Q&A
« Reply #85 on: 09/08/2009 06:25 PM »

I think it would be VERY hard to change the SSME to airstart.  I am certain the design relies heavily on head pressure at the pumps due to gravity during the start sequence......

Is it $1 BILLION dollar hard?   ::)

No. That's probably a lowball. Airstart SSME is harder than J-2X.

JRF

Offline Jim

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Re: Rocket Engine Q&A
« Reply #86 on: 09/08/2009 06:26 PM »

I think it would be VERY hard to change the SSME to airstart.  I am certain the design relies heavily on head pressure at the pumps due to gravity during the start sequence......

Is it $1 BILLION dollar hard?   ::)

No. That's probably a lowball. Airstart SSME is harder than J-2X.


and the SSME can't be restarted and therefore is not a EDS candidate

Offline Jorge

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Re: Rocket Engine Q&A
« Reply #87 on: 09/08/2009 06:27 PM »
If Ares I had an airstart SSME it wouldn't be taking the heat is is. Fair assessment?

If so, how much of a showstopper was this really? Is it technically extremely difficult? Too expensive? Or both? If Nasa wanted Ares I bad enough I would think they would push forward to a solution.

Ares I would taken less heat if it had an airstart SSME.

For one, it would not needed to spend $1B for a brand new J-2X, plus it wouldn't had to spend an additional $1B to put an extra seg.ment (20%) on the existing Shuttle SRB.  That's a wopping $2B impact that Mike Griffin had not counted on. 

But both those items were needed for Ares V anyway. So it would just delay the impact, not eliminate it. Whereas switching to J-2X *eliminated* the impact of airstart SSME.
JRF

Offline Jorge

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Re: Rocket Engine Q&A
« Reply #88 on: 09/08/2009 06:28 PM »

I think it would be VERY hard to change the SSME to airstart.  I am certain the design relies heavily on head pressure at the pumps due to gravity during the start sequence......

Is it $1 BILLION dollar hard?   ::)

No. That's probably a lowball. Airstart SSME is harder than J-2X.


and the SSME can't be restarted and therefore is not a EDS candidate

Right, so you need the J-2X (or some other restartable engine) anyway.
JRF

Offline Propforce

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Re: Rocket Engine Q&A
« Reply #89 on: 09/08/2009 09:20 PM »

I think it would be VERY hard to change the SSME to airstart.  I am certain the design relies heavily on head pressure at the pumps due to gravity during the start sequence......

Is it $1 BILLION dollar hard?   ::)

No. That's probably a lowball. Airstart SSME is harder than J-2X.


and the SSME can't be restarted and therefore is not a EDS candidate

Right, so you need the J-2X (or some other restartable engine) anyway.

Surely for $2 Billon dollars, we can design an air-startable, re-startable, staged combustion cycle engine?

Call it a derived SSME, RS-83, IPD, Russian RD-0120... whatever heritage you'd like
« Last Edit: 09/08/2009 09:21 PM by Propforce »

Offline cleo

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Re: Rocket Engine Q&A
« Reply #90 on: 09/08/2009 09:34 PM »
For some a (slight) notion of the complexity take a look at the ground support for a launch start of SSMEs  Now pack it all up and do same things up in the air /vacuum (spin up of the turbine rotor at such rpms where a tiny spec will rip a blade apart)

Offline Jorge

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Re: Rocket Engine Q&A
« Reply #91 on: 09/08/2009 09:57 PM »

I think it would be VERY hard to change the SSME to airstart.  I am certain the design relies heavily on head pressure at the pumps due to gravity during the start sequence......

Is it $1 BILLION dollar hard?   ::)

No. That's probably a lowball. Airstart SSME is harder than J-2X.


and the SSME can't be restarted and therefore is not a EDS candidate

Right, so you need the J-2X (or some other restartable engine) anyway.

Surely for $2 Billon dollars, we can design an air-startable, re-startable, staged combustion cycle engine?

It will cost more than modifying an existing engine like the J-2. J-2X budget was $1.2 billion back in 2006. Don't know if it's gone up since then. And don't call me Shirley.
JRF

Offline Antares

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Re: Rocket Engine Q&A
« Reply #92 on: 09/08/2009 10:25 PM »
Gents, isn't this getting more into a discussion that should be in the CxP threads?

Another resource for JosephB: http://www.pwrengineering.com/data.htm
There are some papers in there that aren't so technical.
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline JosephB

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Re: Rocket Engine Q&A
« Reply #93 on: 09/09/2009 04:35 AM »
Great points from all. Thank you. Adding all the above mentioned books to the wish list. I have to say that having the air-startable, re-startable, staged combustion cycle engine (Call it a derived SSME, RS-83, IPD) that Propforce mentioned would be wise to have. In hindsight I'll bet Nasa now wishes they would have gone down that path?

On a side note, what does the X-37 use now if not the AR2-3?
« Last Edit: 09/09/2009 04:37 AM by JosephB »

Offline Propforce

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Re: Rocket Engine Q&A
« Reply #94 on: 09/09/2009 04:03 PM »

I think it would be VERY hard to change the SSME to airstart.  I am certain the design relies heavily on head pressure at the pumps due to gravity during the start sequence......

Is it $1 BILLION dollar hard?   ::)

No. That's probably a lowball. Airstart SSME is harder than J-2X.


and the SSME can't be restarted and therefore is not a EDS candidate

Right, so you need the J-2X (or some other restartable engine) anyway.

Surely for $2 Billon dollars, we can design an air-startable, re-startable, staged combustion cycle engine?

It will cost more than modifying an existing engine like the J-2. J-2X budget was $1.2 billion back in 2006. Don't know if it's gone up since then. And don't call me Shirley.

If you say so, Georgi  ;D

BTW, the J-2X looks NOTHING like the J-2.  Just about the only thing 'derived' is the name.

I recalled some discussions on airstart RS-25 back in 2005 and associated NRE & RE costs. 

Offline Antares

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Re: Rocket Engine Q&A
« Reply #95 on: 09/10/2009 05:29 PM »
Hyper vs cryo question:

Is it more common to express run conditions on a hypergol engine in Pc vs MR, whereas on a cryogen engine it's P vs T for the inlet conditions of the propellants?
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline Propforce

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Re: Rocket Engine Q&A
« Reply #96 on: 09/11/2009 03:26 AM »
Hyper vs cryo question:

Is it more common to express run conditions on a hypergol engine in Pc vs MR, whereas on a cryogen engine it's P vs T for the inlet conditions of the propellants?

I think it's the other way around.  In the US, the yhpergols tend to be smaller pressure-fed engines so inlet pressure (& temp) is important, thought the Russians & Chinese are very good at pump-fed hypergol engines.  Cryos tend to be pump-fed engines therefore we usually specify it in Pc & MR.  Inlet pressure is often expressed in terms of NPSP (net positive suction pressure = P-inlet minus P-vapor) requirement.  Engine guys will then design their pump performance characteristic based on the requirements (NPSP, Pc, MR, cycle, & engine balance) given.  At the end, it's iterations & compromises between the engine guys & the vehicle guys.

Offline Antares

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Re: Rocket Engine Q&A
« Reply #97 on: 09/18/2009 04:48 PM »
Reposting an old request I made in the video forum, here in the "engine shop":

In the late 90s there was a video on the web, in the expert.??.purdue.edu domain IIRC, of a couple of enterprising aerospace students putting liquid hydrocarbon fuel in a 2-liter bottle attached to a skateboard and lighting it off in their kitchen.

I'd be in debt to anyone who could find and post it here.  Watching the flame front move through the bottle in slo-mo was pretty neat.
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline JosephB

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Re: Rocket Engine Q&A
« Reply #98 on: 09/18/2009 07:20 PM »
OK, now that sounded too neat not to investigate. I didn't find the Purdue rocketboard but did find something equally entertaining....

http://www.davesdaily.com/videoclips/94-rocketpoweredskateboard.htm

And just for kicks...  (add a "W" to www)

ww.youtube.com/watch?v=LpqwDcM8zcs&feature=channel

Edit: And as Alex noted: Watch out for TO!
« Last Edit: 09/19/2009 02:22 AM by JosephB »

Offline AlexInOklahoma

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Re: Rocket Engine Q&A
« Reply #99 on: 09/19/2009 01:15 AM »
The skateboard motor should not exceed a *four* seg SRB as 5 or more segments just might shake/throw the rider to the ground (vibrations, ya know!)  ;-) 

(Mods: I just HAD to say that, please, please forgive me.....)

Alex