Poll

When will full-scale hot-fire testing of Raptor begin?

Component tests - 2017
3 (0.6%)
Component tests - 2018
21 (4.2%)
Integrated tests -  2017
19 (3.8%)
Integrated tests -  2018
237 (47%)
Integrated tests -  2019
181 (35.9%)
Raptor is not physically scaled up
33 (6.5%)
Never
10 (2%)

Total Members Voted: 504


Author Topic: SpaceX Raptor engine (Super Heavy/Starship Propulsion) - General Thread 1  (Read 869738 times)

Offline livingjw

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #740 on: 11/26/2017 12:50 pm »
I'm just saying that I have seen no evidence that the Raptor or Merlin use any type of spin up system. Does anyone know different?

Merlin uses a spin up system driven by high-pressure helium.  The actual valves used to control the flow of fuel and LOX are spring-actuated (built into the pintle in the case of the combustion chamber, not sure about the preburner but presumably it has something similar?), so in order for fuel to even be injected the pressure must be high enough, which requires first spinning up the turbopump somehow.
Thank you.

John

Offline spacenut

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #741 on: 12/08/2017 03:15 am »
Any new information from SpaceX on Raptor development? 

Offline DJPledger

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #742 on: 12/14/2017 09:54 am »
Any new information from SpaceX on Raptor development? 
Not heard anything. Perhaps you should not expect any more new info. on Raptor dev. until IAC2018 knowing SpaceX.

Offline mgeagon

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #743 on: 01/30/2018 07:35 am »
It appears the Raptor is still the only FFSC engine currently under development. It has been shown to work at full thrust for many minutes in sub-scale form. Why are other space agencies not pursuing this very efficient technology? Why aren't Russia, China, India and the ESA pursuing Methane as the fuel of the future? It seems Blue is going for a slightly more proven ORSC methalox design, and is slowly making some progress, but even that seems years ahead of any new motor on the horizon.


Online woods170

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #744 on: 01/30/2018 08:35 am »
It appears the Raptor is still the only FFSC engine currently under development. It has been shown to work at full thrust for many minutes in sub-scale form. Why are other space agencies not pursuing this very efficient technology? Why aren't Russia, China, India and the ESA pursuing Methane as the fuel of the future? It seems Blue is going for a slightly more proven ORSC methalox design, and is slowly making some progress, but even that seems years ahead of any new motor on the horizon.



ESA is in fact pursuing a Methane-fueled engine as part of the Future Launcher Preparatory Program (FLPP):

http://www.esa.int/Our_Activities/Space_Transportation/Prometheus_to_power_future_launchers

http://spacenews.com/frances-prometheus-reusable-engine-becomes-esa-project-gets-funding-boost/
« Last Edit: 01/30/2018 08:38 am by woods170 »

Offline hkultala

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #745 on: 01/30/2018 09:51 am »
It appears the Raptor is still the only FFSC engine currently under development. It has been shown to work at full thrust for many minutes in sub-scale form. Why are other space agencies not pursuing this very efficient technology?

Engines are not developed just to use new technology. Engines are developed because they are needed and because someone is willing to pay the development costs.

And methalox is not an optimal booster propellant. Kerolox allows lighter tanks, and for similar engine, allows better T/W. (however, FFSC may be easier with methalox than kerolox)

Methalox is a very good compromize between booster propellant and upper stage propellant, when only single propellant type is desired for both.

Quote
Why aren't Russia, China, India and the ESA pursuing Methane as the fuel of the future?

Russia IS planning a methane-fueled rocket to replace most of their rockets

https://en.wikipedia.org/wiki/Soyuz-7_(rocket)

China has series of branch new efficient ORSC engines. They don't need a better engine right now. Developing a new engine would delay their new rockets by many years, and would not make them much better.

SpaceX needed a heavier engine than Merlin, and Blue Origin needed a heavier and more booster-optimized (better T/W, better T/$) engine than BE-3.
When they were anyway developing new booster engines, they decided to go to metlalox.
« Last Edit: 01/30/2018 09:53 am by hkultala »

Offline Cheapchips

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #746 on: 01/30/2018 12:41 pm »

And methalox is not an optimal booster propellant. Kerolox allows lighter tanks, and for similar engine, allows better T/W.

Methalox is better than kerolox for heavy/rapid reuse as it avoids the coking issues that kerolox creates.  That must have been part of the decision by both SX & Blue to chose methane. 

As you point out, why pay the development cost if Methalox is of no benefit.  Only SX and Blue are really targeting reuse at this point.  Doesn't make a whole lot of sense for anyone else yet.

Offline Robotbeat

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #747 on: 01/30/2018 01:02 pm »
It does make sense for everyone else, they're just too hide bound to realize that reuse is the new reality. No point spending billions on a new expendable launcher that effectively assumes SpaceX and Blue will fail at reuse. That's a stupid gamble at this point (and I think some are realizing it now).

Better to fly out existing expendable launchers.
« Last Edit: 01/30/2018 01:25 pm by Robotbeat »
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Offline Cheapchips

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #748 on: 01/30/2018 01:14 pm »

I should have phrased that "doesn't make a whole lot of sense to anyone else".   

Offline TrevorMonty

Methalox also allows for elimination of He for tank pressurisation. Makes for cheaper tank, plumbing and associated ground systems. Especially in SpaceX case another point of failure.
« Last Edit: 01/30/2018 02:31 pm by TrevorMonty »

Offline AncientU

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #750 on: 01/30/2018 03:18 pm »
Methlox is also prime propellant for depots, on-orbit refueling, and long duration spaceflight.
I believe it was a propellant option for the Lunar Lander (Altair) envisioned during Constellation for many of these reasons, but the Methlox engine technology was too immature and NASA went back to RL-10s and Hydrolox.

Edit: Updated choice of Methlox option details for Lunar lander.
« Last Edit: 01/30/2018 03:25 pm by AncientU »
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Offline rakaydos

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #751 on: 01/30/2018 05:39 pm »
The "problem" in the metaphorical mind of the bureaucracy, is that FFSC, Methane, Reuse, and orbital refueling are all a package- they all solve each others problems.

But changing that many things at once is anathema to Oldspace. Test ONE thing until you know it wont fail, then move to the next. Right now they're working on the ACES orbital refueling with their tried and true hydrogen expansion cycle booster, and wont touch the others till the solve, for instance, hydrogen leaking through solid metal over long duration missions.

Offline Rabidpanda

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #752 on: 01/30/2018 06:12 pm »
Methalox is not the end-all be-all of propellants. For SpaceX's BFR architecture it makes sense for a variety of reasons, including ISRU on Mars. For other in-space applications hydrolox may be a better option overall.

FFSC makes higher chamber pressures easier to achieve than ORSC, but at the expense of increased complexity (with all the cost and reliability impacts that entails).

Offline John Alan

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #753 on: 01/30/2018 06:27 pm »
Somewhere (can't find it now) I saw a paper by someone in the EU rocket group, that sub cooled Propane and sub cooled LOX actually works out as the best mass fraction (tank sizes, weights etc) propellant to use in a booster stage...  :o

BUT... can't make propane on mars...  ;)
« Last Edit: 01/30/2018 06:31 pm by John Alan »

Offline docmordrid

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #754 on: 01/30/2018 06:41 pm »
>
BUT... can't make propane on mars...  ;)

Sez here you can, using Fischer-Tropsch Synthesis.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140002709.pdf
« Last Edit: 01/30/2018 06:42 pm by docmordrid »
DM

Offline jpo234

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #755 on: 01/30/2018 07:02 pm »
Methane is basically natural gas. I think Blue actually wants to use commodity natural gas as fuel for the BE-4. With reuse the price of the fuel becomes a significant part of the overall launch price.

I think both, SpaceX and Blue Origin chose methane among other reasons because it is the cheapest practical rocket fuel.
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Offline envy887

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #756 on: 01/30/2018 07:29 pm »
Somewhere (can't find it now) I saw a paper by someone in the EU rocket group, that sub cooled Propane and sub cooled LOX actually works out as the best mass fraction (tank sizes, weights etc) propellant to use in a booster stage...  :o

BUT... can't make propane on mars...  ;)

Propylene is even better, see this post (and several other linked to it)
https://forum.nasaspaceflight.com/index.php?topic=42302.msg1642577#msg1642577

But methane is perfectly acceptable, especially for higher delta-v stages.
« Last Edit: 01/30/2018 07:30 pm by envy887 »

Offline John Alan

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #757 on: 01/30/2018 09:55 pm »
>
BUT... can't make propane on mars...  ;)

Sez here you can, using Fischer-Tropsch Synthesis.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140002709.pdf

I stand corrected... you can make it on Mars with a bit of fine tuning of the processes...  ;)

This same paper also pointed out what the EU folks had said...
(which my Google-Fu has failed to locate and link to sadly today)
Propane and Lox (both deep sub cooled) seems to make the best overall rocket system...  :)
(pages 6 and 7 in that pdf)

But yes... Methane is close enough and cheaper here on earth... likely easiest to make on Mars... 
-------------------------------------------------------------
On edit (aside note)
This other pdf I stumbled across and read some time ago... and now can't find... In a nutshell...
Was a report by some study group in the EU rocket program recommending what the future Ariane 7 or 8 system should be based on...
In short, it suggested copy the Falcon 9 systems ideas, but develop parts based on Propane and Lox...
Engines... tank sizes... all optimized to sub cooled PropLox...
They also said 9 engines on stage 1 and copy the stage one recovery like SpaceX...
Single same type engine stage 2 (like F9) but also added a 3rd stage using hypergols
Overall it was a weird dry read, and now it seems to be gone from the web...

« Last Edit: 01/30/2018 10:28 pm by John Alan »

Offline Robotbeat

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #758 on: 01/30/2018 11:16 pm »
Subcooled propane with Falcon 9 recovery IS a good architecture. They should cancel Ariane 6 and go straight to it, over-sized first stage that would allow upper stage reuse down the road.
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Offline TorenAltair

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #759 on: 01/30/2018 11:41 pm »
@John Alan
Do you mean those studies of the German Aerospace Center?   http://elib.dlr.de/114430/2/PresentationIAC-17%20-%20D2.4.3_f.pdf

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