Author Topic: Raptor Upper Stage consolidated thread  (Read 124093 times)

Offline Okie_Steve

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Re: Raptor Upper Stage consolidated thread
« Reply #180 on: 05/16/2017 02:24 am »
 Remember who asked for the raptor derived US engine to begin with. What if any sort of launch profile might they be interested in that even the super duper M1D of the future might not be able to hack?

Offline envy887

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Re: Raptor Upper Stage consolidated thread
« Reply #181 on: 05/16/2017 02:00 pm »
Remember who asked for the raptor derived US engine to begin with. What if any sort of launch profile might they be interested in that even the super duper M1D of the future might not be able to hack?

Only direct insertion of 15,000+ kg payloads to GEO.

Offline Nathan2go

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Re: Raptor Upper Stage consolidated thread
« Reply #182 on: 05/21/2017 12:01 am »
Remember who asked for the raptor derived US engine to begin with.
Take a look at the SpaceX Mars presentation, then look at what NASA says about Mars, then checkout the Boeing or Lockmart websites.  Outside of the SpaceX fanbase, the rest of the world (including the investment community) does not believe ITS is going to happen any time soon. 

To change that perception, SpaceX needs to use the Falcon family to demonstrate more ITS technology.  Landing F9 S1 repeatedly is great, but they must go further:  flying Raptor on paying missions would help, as would demonstrations of S2 re-use, and a few successful Red Dragon missions.   Demo of on-orbit propellant transfer would be good, but there's little market for that now.

People seem to assume a Raptor upper stage needs to be 5m diameter.  Sure, that's lighter, stronger, and more aesthetic.  But it is also more expensive and less compatible with their existing infrastructure.  F9 is near the limit of too skinny now, but the skinniness pain threshold is higher for the FH (because the benefit is higher due to the US/LS mass imbalance on FH).  Even with 3.7m diameter, some tank stretching is likely.

I'm not expecting a 300% tank stretch on the FH upper stage, but I think a >=20% is very likely (assuming a Merlin engine), and 50-100% with Raptor is very plausible.  That would provide a useful improvement in the payload limit with 3-core S1 re-use, and thus improve competitiveness with New Glenn.
« Last Edit: 05/21/2017 12:07 am by Nathan2go »

Offline AncientU

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Re: Raptor Upper Stage consolidated thread
« Reply #183 on: 05/21/2017 12:12 am »
Remember who asked for the raptor derived US engine to begin with.
Take a look at the SpaceX Mars presentation, then look at what NASA says about Mars, then checkout the Boeing or Lockmart websites.  Outside of the SpaceX fanbase, the rest of the world (including the investment community) does not believe ITS is going to happen any time soon. 
...

The Kremlin and China's leadership would agree... so might lots of Arianespace folks.
Senator Shelby would agree, as would every member of the Alabama (sorry, need to stop here for a second and just say that I have to use stupid words to get my point across. I know that means I must have a weak argument, but that's why I use bad words)..
Same group would have voted in unison about reusable launch vehicles a couple years ago.

Notice a pattern?

What they collectively believe is immaterial to the pace of SpaceX's technological achievement.
"If we shared everything [we are working on] people would think we are insane!"
-- SpaceX friend of mlindner

Offline BobHk

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Re: Raptor Upper Stage consolidated thread
« Reply #184 on: 05/21/2017 12:46 am »

Landing F9 S1 repeatedly is great, but they must go further:

The day landing rockets became old hat.... eagles cried.

Offline su27k

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Re: Raptor Upper Stage consolidated thread
« Reply #185 on: 05/21/2017 03:58 am »
I think the odds of seeing a RUS is significantly reduced after the Tom Mueller interview, he gave no hints this is happening, instead he talked about the Mars rocket, hundreds of tons to orbit, etc. Also when he talked about 2nd stage reuse, it sounds like the stage is still performance challenged, which would not be the case for a big RUS.

Offline meekGee

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Re: Raptor Upper Stage consolidated thread
« Reply #186 on: 05/21/2017 04:40 am »
I think the odds of seeing a RUS is significantly reduced after the Tom Mueller interview, he gave no hints this is happening, instead he talked about the Mars rocket, hundreds of tons to orbit, etc. Also when he talked about 2nd stage reuse, it sounds like the stage is still performance challenged, which would not be the case for a big RUS.

Yup - any time there's indication of trying to reuse the current S2, that's a counte-indication for RUS. 
ABCD - Always Be Counting Down

Offline spacenut

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Re: Raptor Upper Stage consolidated thread
« Reply #187 on: 06/12/2017 08:54 pm »
Could a full size Raptor fit in 3.7m?  That is why I thought if they made a 5m Raptor upper stage, the nozzle would fit.  It sure would make it more competitive with NG and even SLS. 

Online Paul_G

Re: Raptor Upper Stage consolidated thread
« Reply #188 on: 06/21/2017 03:58 pm »
Is this new news:


Quote
from @Painkiller606

@elonmusk How will Raptor-vac engine bell be cooled? Will radiative cooling work with other engine bells surrounding it?

Quote
from @elonmusk

@Painkiller606
Will be full regen cooled all the way out to the 3 meter (10 ft) nozzle diameter. Heat flux is nuts & radiative view factor is low.

https://twitter.com/elonmusk/status/877341165808361472

Offline spacenut

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Re: Raptor Upper Stage consolidated thread
« Reply #189 on: 06/21/2017 05:04 pm »
So, if this test Raptor is made into an engine, would it be about the same size as the Merlin V?  And if so, could the existing size upper stage to increase ISP enough to get larger payloads into orbit off F9 and FH?  The existing upper stage is small enough to be filled by tanker LNG tractor trailer trucks it seems.  My company had one and it was used if there were low pressure areas of our natural gas distribution system during extremely cold weather.  It could supply a town of 25,000 for about a month with one truck load of LNG (residential/small commercial only, not industrial). 

So 2 or 3 of these tractor trailers could fill one upper stage. 

Offline LastStarFighter

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Re: Raptor Upper Stage consolidated thread
« Reply #190 on: 06/21/2017 08:13 pm »
So, if this test Raptor is made into an engine, would it be about the same size as the Merlin V?  And if so, could the existing size upper stage to increase ISP enough to get larger payloads into orbit off F9 and FH?  The existing upper stage is small enough to be filled by tanker LNG tractor trailer trucks it seems.  My company had one and it was used if there were low pressure areas of our natural gas distribution system during extremely cold weather.  It could supply a town of 25,000 for about a month with one truck load of LNG (residential/small commercial only, not industrial). 

So 2 or 3 of these tractor trailers could fill one upper stage.

Hypothetically (since I doubt they would just convert it) it would get less performance with the same volume upper stage. Lower density methane takes up more space and therefore you can't load nearly as much propellant. Same reason ULA's Vulcan has to be a 5+m first stage instead of keeping the Atlas tankage. There are some gains due to a lighter overall weight but that makes the first stage separation velocity even higher which cant be great for recovery. 

Offline envy887

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Re: Raptor Upper Stage consolidated thread
« Reply #191 on: 06/21/2017 11:16 pm »
So, if this test Raptor is made into an engine, would it be about the same size as the Merlin V?  And if so, could the existing size upper stage to increase ISP enough to get larger payloads into orbit off F9 and FH?  The existing upper stage is small enough to be filled by tanker LNG tractor trailer trucks it seems.  My company had one and it was used if there were low pressure areas of our natural gas distribution system during extremely cold weather.  It could supply a town of 25,000 for about a month with one truck load of LNG (residential/small commercial only, not industrial). 

So 2 or 3 of these tractor trailers could fill one upper stage.

Hypothetically (since I doubt they would just convert it) it would get less performance with the same volume upper stage. Lower density methane takes up more space and therefore you can't load nearly as much propellant. Same reason ULA's Vulcan has to be a 5+m first stage instead of keeping the Atlas tankage. There are some gains due to a lighter overall weight but that makes the first stage separation velocity even higher which cant be great for recovery.

Not necessarily true. Depending on the exact values they achieve for engine mass, thrust, and efficiency, the Raptor stage would be anywhere from considerably better to slightly worse for the same volume (the volume ratio of subcooled kerolox to subcooled methalox is 1.209:1.000).

The difference depends on delta-v and payload mass. A typical GTO injection requires the upper stage to provide ~7800 m/s after staging. For a max payload to that delta-v, the Raptor is likely better (see attached graph). You can adjust the sensitivity to engine parameters in the attached spreadsheet...

Edit: I did not include the reduced gravity loss the RUS would incur due to lighter lift-off and staging mass and shorter burn time for both S1 and S2. This would favor the Raptor stage by a couple more percent.
« Last Edit: 06/21/2017 11:20 pm by envy887 »

Offline spacenut

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Re: Raptor Upper Stage consolidated thread
« Reply #192 on: 06/21/2017 11:31 pm »
So, would it help at all, OR, would you have to make the stage wider, or longer to achieve upgraded capabilities?

Offline envy887

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Re: Raptor Upper Stage consolidated thread
« Reply #193 on: 06/22/2017 12:25 am »
So, would it help at all, OR, would you have to make the stage wider, or longer to achieve upgraded capabilities?

Maybe a little. Probably not much.

But with a 2m stretch to the F9 US (basically what they did from v1.1>v1.2), a methalox RUS would have the same wet mass as the current kerolox US. Which would bump the performance considerably if they hit Raptor performance specs. Full expendable would be about:

27.5 tonne to LEO
11 tonne to GEO-1800
7.3 tonne to TLI
« Last Edit: 06/22/2017 12:25 am by envy887 »

Offline Rik ISS-fan

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Re: Raptor Upper Stage consolidated thread
« Reply #194 on: 06/22/2017 08:06 am »
Could a 1.5 stage to orbit using two Falcon Heavy boosters and a core (orbital stage) powered by a single vacuum optimized Merlin Raptor 3MN engine. The core could be derived from an expendable falcon heavy core.
I'm very sceptical about upperstage reusability, so the core will be expendable.
If required an small in orbit maneuvering stage (Hypergolic Draco, or LOx-Methane) could be added.
Could this work? What will be it's performance? And is it a good idea?

I think for a Falcon 9 upper-stage a Raptor 1MN would be required. I do like the idea.
A methane merlin (Merlin 1D.M / 1DV.m) could be an intermediate development before the FFSC Raptor 3MN.
« Last Edit: 06/22/2017 07:19 pm by Rik ISS-fan »

Online rakaydos

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Re: Raptor Upper Stage consolidated thread
« Reply #195 on: 06/22/2017 05:07 pm »
Could a 1.5 stage to orbit using two Falcon Heavy boosters and a core (orbital stage) powered by a single vacuum optimized Merlin 3MN engine. The core could be derived from an expendable falcon heavy core.
I'm very sceptical about upperstage reusability, so the core will be expendable.
If required an small in orbit maneuvering stage (Hypergolic Draco, or LOx-Methane) could be added.
Could this work? What will be it's performance? And is it a good idea?

I think for a Falcon 9 upper-stage a Raptor 1MN would be required. I do like the idea.
A methane merlin (Merlin 1D.M / 1DV.m) could be an intermediate development before the FFSC Raptor 3MN.

What are you trying to gain by going 1.5 stage over 2.5 stage?

Offline envy887

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Re: Raptor Upper Stage consolidated thread
« Reply #196 on: 06/22/2017 05:23 pm »
Could a 1.5 stage to orbit using two Falcon Heavy boosters and a core (orbital stage) powered by a single vacuum optimized Merlin 3MN engine. The core could be derived from an expendable falcon heavy core.
I'm very sceptical about upperstage reusability, so the core will be expendable.
If required an small in orbit maneuvering stage (Hypergolic Draco, or LOx-Methane) could be added.
Could this work? What will be it's performance? And is it a good idea?

I think for a Falcon 9 upper-stage a Raptor 1MN would be required. I do like the idea.
A methane merlin (Merlin 1D.M / 1DV.m) could be an intermediate development before the FFSC Raptor 3MN.

There is no "Merlin 3MN engine" or plans for one. Merlin is kerolox and SpaceX is going methalox.

1.5 parallel stage rockets are not very efficient: replacing a 5 tonne upper stage with a 25 tonne core means 20 fewer tonnes of payload to orbit. And now you expend a $30M booster instead of a $10M upper stage. You do gain the reliability of fewer staging events and all-groundlit engines, but SpaceX hasn't found this worthwhile compared to the efficiency of a serial TSTO. Especially since the engine has to be able to be lit on the ground, which costs some efficiency.

If SpaceX goes with a Raptor on Falcon, it will be an air-lit upper stage.

Offline Lars-J

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Re: Raptor Upper Stage consolidated thread
« Reply #197 on: 06/22/2017 05:36 pm »
Could a 1.5 stage to orbit using two Falcon Heavy boosters and a core (orbital stage) powered by a single vacuum optimized Merlin 3MN engine. The core could be derived from an expendable falcon heavy core.
I'm very sceptical about upperstage reusability, so the core will be expendable.
If required an small in orbit maneuvering stage (Hypergolic Draco, or LOx-Methane) could be added.
Could this work? What will be it's performance? And is it a good idea?

I think for a Falcon 9 upper-stage a Raptor 1MN would be required. I do like the idea.
A methane merlin (Merlin 1D.M / 1DV.m) could be an intermediate development before the FFSC Raptor 3MN.

What is Merlin 3MN? Raptor 1MN? Raptor 3MN?

Offline spacenut

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Re: Raptor Upper Stage consolidated thread
« Reply #198 on: 06/22/2017 05:53 pm »
So it seems the test Raptor, IF made into an upper stage vacuum engine, with a 2m stretch of the upper stage, gets the results you say, they should do that at least for FH.  Even with F9, it would cut into some of the FH launches.

Offline envy887

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Re: Raptor Upper Stage consolidated thread
« Reply #199 on: 06/22/2017 06:48 pm »
Could a 1.5 stage to orbit using two Falcon Heavy boosters and a core (orbital stage) powered by a single vacuum optimized Merlin 3MN engine. The core could be derived from an expendable falcon heavy core.
I'm very sceptical about upperstage reusability, so the core will be expendable.
If required an small in orbit maneuvering stage (Hypergolic Draco, or LOx-Methane) could be added.
Could this work? What will be it's performance? And is it a good idea?

I think for a Falcon 9 upper-stage a Raptor 1MN would be required. I do like the idea.
A methane merlin (Merlin 1D.M / 1DV.m) could be an intermediate development before the FFSC Raptor 3MN.

What is Merlin 3MN? Raptor 1MN? Raptor 3MN?

1MN = 1,000 kN which is the nominal thrust of the subscale Raptor demo engine fired last year.

3MN = ~3,000 kN which is the nominal thrust of the ITS Raptor proposed at IAC 2016.

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