Author Topic: ITS Propulsion – The evolution of the SpaceX Raptor engine  (Read 51375 times)

Offline docmordrid

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #180 on: 04/22/2017 12:29 AM »
Any significance to specifying flight assemblies & hardware?

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Offline philw1776

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #181 on: 04/22/2017 01:35 PM »
I wouldn't get too excited about something likely massaged by HR
“When it looks more like an alien dreadnought, that’s when you know you’ve won.”

Offline robert_d

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #182 on: 05/04/2017 02:04 AM »
My question is what conditions/factors must be accounted for if this new engine is to be restartable?
Will there be a separate restartable version? Does performance suffer overall? Is there extra weight involved for other equipment/fluids? What about power required before the engine can produce any of its own?


Offline livingjw

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #183 on: 05/04/2017 11:18 PM »
My question is what conditions/factors must be accounted for if this new engine is to be restartable?
Will there be a separate restartable version? Does performance suffer overall? Is there extra weight involved for other equipment/fluids? What about power required before the engine can produce any of its own?

They said it was spark ignited. The sparks probably ignite ignition torches which in turn ignites the pre-burners and the main chamber.  You can see the ignition leads on their CAD model.

This ignition approach would make all Raptors restartable assuming their propellants had enough head pressure.
Head pressure and an electrical power source is all that is required to start.

The start sequence is something like the following:
- crack valves and dribble in propellants to pre-chill the engine.
- open valves and propellants flow into their respective pre-burners.
- spark ignites stoichiometric mixture in torches.
- torches ignite pre-burners
- pre-burner exhaust spins turbines attached to propellant pumps. (one for methane, one for LOX)
- main chamber torch ignites gaseous propellants entering chamber.
- pumps start increasing pressure above head pressure and quickly climb to design pressure.

This requires detailed understanding of the combustion processes and the dynamics of the pumps, turbines and valves. It is a tightly choreographed dance.

John



Offline Apollo100

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #184 on: 05/08/2017 05:52 PM »
Were the initial "Raptor" tests solely re-manufactured IPD hardware from AR drawings, or did they change the designs?

The Integrated Powerhead Demonstrator used liquid hydrogen propellant, so yes of course SpaceX must have changed the design for Raptor. Thanks for the pointer -- it was fascinating to read about IPD. I wonder how many Aerojet-Rocketdyne engineers are working at SpaceX now?

Hydrogen seems to behave pretty similarly to methane with regards to engine operation. Most of the methalox engines fired to date have been lightly modified hydrolox engines, not purpose-built designs.

Though I doubt there is much IPD heritage in Raptor

Thanks for the replies and apologies for the delayed response.... Given that SX acquired the IPD Final report, all of the drawings, and all of the hardware, I would imagine that there is quite a bit of IPD heritage in the Raptor engine.

Online Robotbeat

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #185 on: 05/09/2017 12:42 PM »
Were the initial "Raptor" tests solely re-manufactured IPD hardware from AR drawings, or did they change the designs?

The Integrated Powerhead Demonstrator used liquid hydrogen propellant, so yes of course SpaceX must have changed the design for Raptor. Thanks for the pointer -- it was fascinating to read about IPD. I wonder how many Aerojet-Rocketdyne engineers are working at SpaceX now?

Hydrogen seems to behave pretty similarly to methane with regards to engine operation. Most of the methalox engines fired to date have been lightly modified hydrolox engines, not purpose-built designs.

Though I doubt there is much IPD heritage in Raptor

Thanks for the replies and apologies for the delayed response.... Given that SX acquired the IPD Final report, all of the drawings, and all of the hardware, I would imagine that there is quite a bit of IPD heritage in the Raptor engine.
I wouldn't. SpaceX learned the lessons and will implement the solutions in their own way.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline spacenut

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #186 on: 05/09/2017 12:54 PM »
So, what is the proposed thrust SL and Vacuum?  I've seen it all over the map.  In pounds thrust, please.  I'm retired and grew up and used the English system all my life.  I compare it to old engines from the 1960's like the F-1 and H-1, etc. 

Offline philw1776

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #187 on: 05/09/2017 02:13 PM »
So, what is the proposed thrust SL and Vacuum?  I've seen it all over the map.  In pounds thrust, please.  I'm retired and grew up and used the English system all my life.  I compare it to old engines from the 1960's like the F-1 and H-1, etc.

R SL  685,000 LBS   3050 KN

Rvac  787,000 LBS   3500 KN

Source ITS presentation Sept 2016
« Last Edit: 05/09/2017 02:42 PM by philw1776 »
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Offline spacenut

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #188 on: 05/10/2017 07:05 PM »
That is more than I thought.  I though it was about 550,000 lbs. 

Offline philw1776

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #189 on: 05/13/2017 05:33 PM »
That is more than I thought.  I though it was about 550,000 lbs.

That was the # announced years before the September reveal.  Even before that it was up to F-1 levels.
In the BFR threads here I predicted the thrust upgrade in Elon's reveal and made the obvious (sun to rise in East tomorrow) prediction that all BFR #s would continue to evolve long after those on the September Tablets From The Mount.
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Online hamerad

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #190 on: 06/21/2017 02:50 AM »
Quote
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

Elon Musk on twitter. Probably already rumoured but now confirmed

Online Lars-J

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #191 on: 06/21/2017 04:30 AM »
Quote
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

Elon Musk on twitter. Probably already rumoured but now confirmed

Interesting! That also means that they have shrunk the Raptor-Vac nozzle, in the original ITS presentation the nozzle diameter was closer to 3.7m / 12 ft. (as measured from the schematic images)
« Last Edit: 06/21/2017 04:31 AM by Lars-J »

Online guckyfan

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #192 on: 06/21/2017 06:17 AM »
It also means it is a quite robust nozzle, as needed to survive reentry. Somewhat more heavy too. But that is the price for a reusable vac nozzle.

Offline nacnud

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #193 on: 06/21/2017 06:45 AM »
Interesting! That also means that they have shrunk the Raptor-Vac nozzle, in the original ITS presentation the nozzle diameter was closer to 3.7m / 12 ft. (as measured from the schematic images)

Does it mean it has been shrunk? You could read the statement to mean that the last 2 feet of diameter increase is radiatively cooled.

Online jpo234

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #194 on: 06/21/2017 07:08 AM »
Interesting! That also means that they have shrunk the Raptor-Vac nozzle, in the original ITS presentation the nozzle diameter was closer to 3.7m / 12 ft. (as measured from the schematic images)

While this might be true, it's not something Elon wrote in this Tweet. The nozzle might well extend beyond the 3m diameter mark, but then with radiative cooling.

Edit: Just what nacnud wrote.
« Last Edit: 06/21/2017 07:10 AM by jpo234 »

Online AncientU

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #195 on: 06/21/2017 09:42 AM »
What expansion ratio does this 3m correspond to then?  40?
« Last Edit: 06/21/2017 09:43 AM by AncientU »
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Offline DJPledger

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #196 on: 06/21/2017 10:03 AM »
What expansion ratio does this 3m correspond to then?  40?
3m Raptor nozzle at ER 40 would produce F-1 class thrust so  3m nozzle dia. for the announced thrust of Raptor would indicate an ER of around 100-150.

Online AncientU

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #197 on: 06/21/2017 10:46 AM »
What expansion ratio does this 3m correspond to then?  40?
3m Raptor nozzle at ER 40 would produce F-1 class thrust so  3m nozzle dia. for the announced thrust of Raptor would indicate an ER of around 100-150.

So, this would be the vac version?  Multiple engines on a second stage would preclude the radiative cooling used on single-engine Falcon S2s.

Note: Just realized this is all about Raptor Vac...
« Last Edit: 06/21/2017 10:51 AM by AncientU »
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Offline envy887

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #198 on: 06/21/2017 04:06 PM »
What expansion ratio does this 3m correspond to then?  40?
3m Raptor nozzle at ER 40 would produce F-1 class thrust so  3m nozzle dia. for the announced thrust of Raptor would indicate an ER of around 100-150.

To narrow this down just a little, it should be an ER of 130 - 140 at 3m diameter to hit the expected thrust (3500 kN) and ISP (382 sec) with a full ER of 200.

They could lower the thrust target and get a ER of 200 with a 3 m nozzle.

Offline Kaputnik

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #199 on: 06/22/2017 03:04 PM »
Interesting! That also means that they have shrunk the Raptor-Vac nozzle, in the original ITS presentation the nozzle diameter was closer to 3.7m / 12 ft. (as measured from the schematic images)

Does it mean it has been shrunk? You could read the statement to mean that the last 2 feet of diameter increase is radiatively cooled.

That would a somewhat contrived reading, IMHO. 'Full regen' implies the whole thing, as opposed to simply 'regen' or 'partial regen'; 'nozzle diameter' implies the whole thing, not a measurement of a point on the nozzle.

It seems slightly more plausible that he simply forgot the .7
Waiting for joy and raptor

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