Author Topic: Rocket Engine Q&A (Read 410481 times)

edkyle99 · « **Reply #20 on:** 03/23/2009 03:42 pm »

Quote from: gospacex on 03/23/2009 04:21 am

If you retain general dimensions of tankage, LOX/RP-1 based booster would weigh much more, need more engines, but also would have much bigger performance.

That would be a beyond-monster rocket! It would need at least 10 RS-84 engines on the core (if they could be made to fit). The core and twin boosters would produce roughly 18 million pounds of thrust at liftoff. The rocket would weigh something like 14.5 million pounds at liftoff. That's roughly equivalent to 2.4 Saturn V rockets, or about 1.8 Ares Vs, or 14.5 fully loaded A380s going straight up.

House foundations would crack in Titusville! Car alarms would go off in Orlando! All that for only a factor of 1.2 improvement in payload.

"Woof" nonetheless!

- Ed Kyle

JosephB · « **Reply #21 on:** 03/24/2009 01:02 am »

Not to beat a dead horse on Ares I (but I will anyway), after reading this and other threads wouldn't a better 1st stage be a single core with a cluster of 4 RS-68A's with a J2X upper (manned rating aside) maybe GEM capable? Then you could have a bigger service module, more capable Orion, etc.

I can see why they went with the solid for safety reasons but still. And a five seg solid still deserves devlopment just for the A5 in it's own right (imho).
Good, bad or ugly?

Jim · « **Reply #22 on:** 03/24/2009 01:08 am »

Quote from: JosephB on 03/24/2009 01:02 am

(manned rating aside) maybe GEM capable?

GEMs are a no no wrt safety/reliability

JosephB · « **Reply #23 on:** 03/24/2009 01:17 am »

I didn't know GEM's were that sketchy. Although they would be on my mind if I were riding on top! What about a 4 engine core? Sufficient?

Jim · « **Reply #24 on:** 03/24/2009 01:20 am »

Quote from: JosephB on 03/24/2009 01:17 am

I didn't know GEM's were that sketchy. Although they would be on my mind if I were riding 'on top! What about a 4 engine core? Sufficient?

It isn't the GEM's themselves, it is the additional parts/systems which reduces "reliability". That is the line that gave us the SRB first stage

JosephB · « **Reply #25 on:** 03/24/2009 01:45 am »

I see your point, but then the russian launchers come to mind with all the engines & plumbing...

Solids may be a different animal entirely in that respect but the SRB sure limits what can be done. One good thing is that it's in the here & now.

edkyle99 · « **Reply #26 on:** 03/24/2009 02:09 am »

Quote from: JosephB on 03/24/2009 01:02 am

Not to beat a dead horse on Ares I (but I will anyway), after reading this and other threads wouldn't a better 1st stage be a single core with a cluster of 4 RS-68A's with a J2X upper (manned rating aside) maybe GEM capable? Then you could have a bigger service module, more capable Orion, etc.

I can see why they went with the solid for safety reasons but still. And a five seg solid still deserves devlopment just for the A5 in it's own right (imho).
Good, bad or ugly?

MSFC proposed a similar idea back in 2004-2005, an ET-based core launcher that would serve as a building block toward a larger vehicle. The problem was that the core didn't serve either purpose (crew launch or cargo launch) very well. It needs to be smaller for crew and larger for cargo.

- Ed Kyle

Proponent · « **Reply #27 on:** 03/24/2009 02:11 am »

Quote from: Jim on 03/24/2009 01:08 am

GEMs are a no no wrt safety/reliability

A couple of questions about solid reliability, if I may:

* Do solids ever fail to ignite these days, either on the pad or at staging?
* Are there any solid or solid-boosted LVs that are held down until proper ignition is verified?
* What proportion of solid failures are catastrophic (i.e., of the "boom" variety rather than of, say, the loss-of-thrust variety)?

Jim · « **Reply #28 on:** 03/24/2009 02:14 am »

Quote from: Proponent on 03/24/2009 02:11 am

* Are there any solid or solid-boosted LVs that are held down until proper ignition is verified?

that would be none I believe

GI-Thruster · « **Reply #29 on:** 03/24/2009 03:49 pm »

Anyone heard anything about aerospike in the last 6 months?

http://www.csulb.edu/colleges/coe/mae/views/projects/rocket/news_2008/aerospike06252008.shtml

Anyone heard anything about pulsed detonation research or continuous detonation research in the last year or is continuous still a pipe dream?

Anyone know how Qinetiq's ion drive on GOCE compares to NASA's ion thrusters? With 40 years of ion research it would be embarrassing if ESA is ahead of NASA and if they're not one wonders why they didn't ask to fly one of ours. . .

http://www.esa.int/SPECIALS/GOCE/index.html

JosephB · « **Reply #30 on:** 03/25/2009 02:59 am »

Ed, very interesting. I didn't know that was ever proposed. I have no idea about performance numbers but something 1/2 to 3/4 the size of the ET would would seem perfect for what Orion is trying to accomplish (with plenty of margin).

Would anyone have a good link to find out the latest progress on the J2X?

JosephB · « **Reply #31 on:** 03/25/2009 11:50 am »

Quote from: JosephB on 03/25/2009 02:59 am

I have no idea about performance numbers but something 1/2 to 3/4 the size of the ET would would seem perfect

LOL That didn't sound to good did it?

Antares · « **Reply #32 on:** 03/26/2009 02:17 am »

Quote from: JosephB on 03/25/2009 02:59 am

Would anyone have a good link to find out the latest progress on the J2X?

Good news is usually provided here. Bad news is usually provided (at least the first anyone outside of NASA hears about it) here.

duane · « **Reply #33 on:** 03/27/2009 06:27 pm »

Your "bad news" link is broken, or is that a forum on the pay side of NSF ?

kch · « **Reply #34 on:** 03/27/2009 06:55 pm »

Quote from: duane on 03/27/2009 06:27 pm

Your "bad news" link is broken, or is that a forum on the pay side of NSF ?

That's the "Constellation" section of L2.

JosephB · « **Reply #35 on:** 03/31/2009 03:03 am »

Quote from: JosephB on 03/24/2009 01:02 am

Not to beat a dead horse on Ares I (but I will anyway), after reading this and other threads wouldn't a better 1st stage be a single core with a cluster of 4 RS-68A's with a J2X upper (manned rating aside) maybe GEM capable? Then you could have a bigger service module, more capable Orion, etc.

I can see why they went with the solid for safety reasons but still. And a five seg solid still deserves devlopment just for the A5 in it's own right (imho).
Good, bad or ugly?

Looks like other folks were thinking along the same lines well before me (imagine that). See attached...
An 8 meter CBC could lift the "Apollo on steroids" I bet. Even the larger more capable versions of Orion.

kkattula · « **Reply #36 on:** 03/31/2009 06:17 am »

Anyone know what the performance of a single core, 7 or 8 meter CBC with 2, 3 or 4 RS-68A's and an improved US would be?

Although at 8m and 4 engines, it's getting close to an ET with engines underneath and no SRB's.

JosephB · « **Reply #37 on:** 04/14/2009 07:07 pm »

Question for the more technical members...
Since A5 is set for 5 1/2 segment SRB's, wouldn't A1 gain from using it as well?
I tried searching but to no avail.

jabe · « **Reply #38 on:** 04/14/2009 09:55 pm »

A real newbie question on this..
why is a LO2/LH2 engine more expensive to design then a LO2/Kero? Is it the temperature involved the main problem? I think I'm missing the obvious on this.
jb

JosephB · « **Reply #39 on:** 04/15/2009 01:34 am »

Quote from: JosephB on 04/14/2009 07:07 pm

Question for the more technical members...
Since A5 is set for 5 1/2 segment SRB's, wouldn't A1 gain from using it as well?
I tried searching but to no avail.

OK, how about any member?
Does that extra weight push it in the realm of diminishing returns?