Poll

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

Component tests - 2017
3 (0.9%)
Component tests - 2018
18 (5.4%)
Integrated tests -  2017
16 (4.8%)
Integrated tests -  2018
218 (65.1%)
Integrated tests -  2019
51 (15.2%)
Raptor is not physically scaled up
25 (7.5%)
Never
4 (1.2%)

Total Members Voted: 335


Author Topic: ITS Propulsion The evolution of the SpaceX Raptor engine  (Read 317868 times)

Offline spacenut

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Re: ITS Propulsion The evolution of the SpaceX Raptor engine
« Reply #780 on: 02/01/2018 02:15 AM »
Ok, does anyone have any updates on Raptor?  Have they tested it to a higher pressure yet? 

Offline DJPledger

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Re: ITS Propulsion The evolution of the SpaceX Raptor engine
« Reply #781 on: 02/01/2018 08:33 AM »
Ok, does anyone have any updates on Raptor?  Have they tested it to a higher pressure yet? 
No more news on Raptor as far as I know. We will likely have to wait until IAC2018 for the next Raptor update.

Online meekGee

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Re: ITS Propulsion The evolution of the SpaceX Raptor engine
« Reply #782 on: 02/01/2018 11:58 AM »
Ok, does anyone have any updates on Raptor?  Have they tested it to a higher pressure yet? 
No more news on Raptor as far as I know. We will likely have to wait until IAC2018 for the next Raptor update.
Or a BFS update...
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Offline JoeyOak

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Re: ITS Propulsion The evolution of the SpaceX Raptor engine
« Reply #783 on: 02/07/2018 04:29 PM »
On the Methane side of Raptor...
I've always thought of it as a modified expander cycle with the preburner there to kick start it from cold and add some heat to vaporize the LNG full flow pre turbine once running...

In short... BOTH turbines will run at near room temps once going... (my opinion)  ;)

That said... the hard part of Raptor is starting it... (I think)
I'm thinking a supply of very high pressure gaseous oxygen and gaseous methane is needed to bring Raptor to life from a cold start...
700 bar room temp COPV's anyone?...  :o

All preburners (and the RCS system) share this common supply (maybe with some redundancies)

Once a Raptor is running... It can be tapped to refill such a bottle supply and keep it topped up...
(tap high pressure liquid into a small "boiler" to batch flash it into the higher pressure of the storage system)
Batch boilers may be electric heated... I'm not sure on that... 

It's all a system... thinking system and not just a rocket engine here...

Is there a commonly recognized name for this startup sequence? "Expander pressure vessel-boosted bootstrap startup"? :)

The RS-25 uses "pure" bootstrap startup, but the start sequence is slow, three to six seconds according to blogs.nasa.gov/J2X/2014/01/24/inside-the-leo-doghouse-light-my-fire/, which seems a bit slow for inflight and landings. Boosting the spin-up with pressurized gaseous propellant seems quite ingenious to me.

Offline John Alan

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #784 on: 02/07/2018 04:42 PM »
On the Methane side of Raptor...
I've always thought of it as a modified expander cycle with the preburner there to kick start it from cold and add some heat to vaporize the LNG full flow pre turbine once running...

In short... BOTH turbines will run at near room temps once going... (my opinion)  ;)

That said... the hard part of Raptor is starting it... (I think)
I'm thinking a supply of very high pressure gaseous oxygen and gaseous methane is needed to bring Raptor to life from a cold start...
700 bar room temp COPV's anyone?...  :o

All preburners (and the RCS system) share this common supply (maybe with some redundancies)

Once a Raptor is running... It can be tapped to refill such a bottle supply and keep it topped up...
(tap high pressure liquid into a small "boiler" to batch flash it into the higher pressure of the storage system)
Batch boilers may be electric heated... I'm not sure on that... 

It's all a system... thinking system and not just a rocket engine here...

Is there a commonly recognized name for this startup sequence? "Expander pressure vessel-boosted bootstrap startup"? :)

The RS-25 uses "pure" bootstrap startup, but the start sequence is slow, three to six seconds according to blogs.nasa.gov/J2X/2014/01/24/inside-the-leo-doghouse-light-my-fire/, which seems a bit slow for inflight and landings. Boosting the spin-up with pressurized gaseous propellant seems quite ingenious to me.

It's likely SpaceX (and Tom Mueller in particular) have a name for the Raptor startup sequence... never made public to my knowledge...
Please be aware that what I posted back in November was my speculation on how Raptor worked (and started) based on what we know so far about it's design...
In short... my opinion...
It's an engine with four sources of prop to run...
Super high psi gaseous Methane and Oxygen to power the pre-burners...
Super cold ~50psi liquid LNG and LOX... to feed the main chamber via pumps...
Just my opinion... nothing more...  ;)
« Last Edit: 02/07/2018 08:50 PM by John Alan »

Offline Hominans Kosmos

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Re: ITS Propulsion The evolution of the SpaceX Raptor engine
« Reply #785 on: 02/09/2018 05:00 PM »
Quote from: John Alan

That's not it directly...
HOWEVER... it reads like that was written after the prior study (I can't find) was published...
And it seems to be a follow on presentation based on that prior dry wordy study...

Nice Find...  :)

You'll find the whole study at http://elib.dlr.de/114430/
Actually you can find a lot of similar studies at the DLR servers. Their ftp servers never forget anything (Experiencing a Vulcain full run engine test from 200 meters away is something you won't forget as well ;) )

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.

Methane/NG is much cheaper though, not really as important now, but could be the difference of millions of dollars in a BFR-sized rocket.

Don't forget the EU has their launch site at Guiana in South America...
I'm not 100% sure LNG will be the cheapest hydrocarbon to get on site... ready to load on the rocket...

Purified Propane could

A large part that appears to be missing from the discussion, even from that german paper, is the comparative performance of the propellants as pressurants. The german paper cites a modelling tool not available for review: PMP 1.0 http://elib.dlr.de/113634/

Their conclusions on the benefits of propane versus methane could be flipped if that modeling is incorrect. They both have about the same launch vehicle mass, higher density might make upper stage reusability more difficult?

Besides the viscosity advantages of methane over propane (and cost), there is also performance as pressurization gas to consider. Methane has the handicap of having larger tank volumes to pressurize, but it has the two advantages of higher pressure and lower molecular weight.

https://i.imgur.com/fmDdyAe.png
Compiled from publicly available data, propane's curve would be two vertical dividers to the right, crossing 1 bar at around 230 kelvin. I hope to improve the spreadsheet soon. Edit: assume pressurization performance improves the further to the left (closer to helium) your substance is on this metric. Other metrics will apply as well.
« Last Edit: 02/09/2018 05:20 PM by Hominans Kosmos »

Offline Hominans Kosmos

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Re: ITS Propulsion The evolution of the SpaceX Raptor engine
« Reply #786 on: 02/09/2018 05:45 PM »
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.

No clue about the Indians or the Japanese, but I'm pretty sure for the rest it could be due to a shortage of young engineering talent without the experience of a previous successful  engine design under their belt form the recent past. Smaller talent, experience and legacy pool to work with. That and lack of private space flight industry, they're all variants of public sector contractors and subsidised munitions factories. Taking risks isn't public sector style usually.

Online Robotbeat

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Re: ITS Propulsion The evolution of the SpaceX Raptor engine
« Reply #787 on: 02/09/2018 05:49 PM »
BTW, "subscale" is in the eye of the beholder. Current Raptor would work fine in a prototype BFS doing Grasshopper-like hoops.
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Offline wannamoonbase

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Re: ITS Propulsion The evolution of the SpaceX Raptor engine
« Reply #788 on: 02/09/2018 08:37 PM »
BTW, "subscale" is in the eye of the beholder. Current Raptor would work fine in a prototype BFS doing Grasshopper-like hoops.

Agreed, EM has shown with rockets and cars that he prefers to get something done and iterate.  He said they'd have a BFS flying.  He didn't say it would have the final Raptor or be the final design (edit: of the BFS).

I could see them building something that flys and has the equivalent of a Merlin 1A engine.  Get it up, learn and iterate.

Compared to how NASA has spent $10 of billions in the last 30 years on vehicles that have never left the ground I prefer the SpaceX development method.
« Last Edit: 02/09/2018 08:38 PM by wannamoonbase »
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Online vaporcobra

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Re: ITS Propulsion The evolution of the SpaceX Raptor engine
« Reply #789 on: 02/09/2018 09:37 PM »
BTW, "subscale" is in the eye of the beholder. Current Raptor would work fine in a prototype BFS doing Grasshopper-like hoops.

Agreed, EM has shown with rockets and cars that he prefers to get something done and iterate.  He said they'd have a BFS flying.  He didn't say it would have the final Raptor or be the final design (edit: of the BFS).

I could see them building something that flys and has the equivalent of a Merlin 1A engine.  Get it up, learn and iterate.

Compared to how NASA has spent $10 of billions in the last 30 years on vehicles that have never left the ground I prefer the SpaceX development method.

Let's be fair, Ares IX flew a sum total of one time ;)

Offline Elmar Moelzer

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Re: ITS Propulsion The evolution of the SpaceX Raptor engine
« Reply #790 on: 02/10/2018 09:01 PM »
Let's be fair, Ares IX flew a sum total of one time ;)
And that was a subscale booster and lacked a second stage...

Online vaporcobra

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Re: ITS Propulsion The evolution of the SpaceX Raptor engine
« Reply #791 on: 02/10/2018 09:13 PM »
Let's be fair, Ares IX flew a sum total of one time ;)
And that was a subscale booster and lacked a second stage...

HEY, it still flew successfully :D consider it a ~$40 billion test flight, of maybe 2-4, assuming SLS flies even a few times.

Offline envy887

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Re: ITS Propulsion The evolution of the SpaceX Raptor engine
« Reply #792 on: 02/11/2018 01:22 AM »
A smaller raptor would mean an even smaller initial vehicle.

Not going to happen.

They could drop in 1000 kN Raptors on the 2017 BFS and still launch with up to half a fuel load.

Offline cscott

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Re: ITS Propulsion The evolution of the SpaceX Raptor engine
« Reply #793 on: 02/11/2018 12:44 PM »
Considering that the Merlin 1A (340kN thrust) is basically a subscale version of the Merlin 1D (845kN thrust), and SpaceX developed Falcon 1 and the three-engine Grasshopper and F9dev as "subscale" test vehicles, I don't see why a subscale raptor wouldn't be used on initial test vehicles.

Offline guckyfan

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Re: ITS Propulsion The evolution of the SpaceX Raptor engine
« Reply #794 on: 02/11/2018 03:14 PM »
A smaller raptor would mean an even smaller initial vehicle.

Not going to happen.

They could drop in 1000 kN Raptors on the 2017 BFS and still launch with up to half a fuel load.

They would still need to flight qualify them. I think they will flight qualify the intended version, even if they initially fly them below full pressure.

Offline hkultala

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Re: ITS Propulsion The evolution of the SpaceX Raptor engine
« Reply #795 on: 02/11/2018 08:13 PM »
Considering that the Merlin 1A (340kN thrust) is basically a subscale version of the Merlin 1D (845kN thrust), and SpaceX developed Falcon 1 and the three-engine Grasshopper and F9dev as "subscale" test vehicles, I don't see why a subscale raptor wouldn't be used on initial test vehicles.
There were interim versions of Merlin used on actual Falcon 9 missions, and I don't think I need to tell you that falcon 9 changed substantially during its service life.

They could use the subscale Raptor for BFR initially, but the vehicle (like Falcon 9) would have to be smaller.

no, it would not have to be smaller. It could launch with only partially fueled tanks.

When they were developing Merlin 1A, falcon 1 and falcon 9 1.0, they did not know much more thrust they will eventually get from the updated later merlin engine variants, and they really, really had to get SOMETHING flying.

So they made the craft for those engines they had at that point.

Offline envy887

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Re: ITS Propulsion The evolution of the SpaceX Raptor engine
« Reply #796 on: 02/13/2018 07:14 PM »
Considering that the Merlin 1A (340kN thrust) is basically a subscale version of the Merlin 1D (845kN thrust), and SpaceX developed Falcon 1 and the three-engine Grasshopper and F9dev as "subscale" test vehicles, I don't see why a subscale raptor wouldn't be used on initial test vehicles.
There were interim versions of Merlin used on actual Falcon 9 missions, and I don't think I need to tell you that falcon 9 changed substantially during its service life.

They could use the subscale Raptor for BFR initially, but the vehicle (like Falcon 9) would have to be smaller.

no, it would not have to be smaller. It could launch with only partially fueled tanks.

When they were developing Merlin 1A, falcon 1 and falcon 9 1.0, they did not know much more thrust they will eventually get from the updated later merlin engine variants, and they really, really had to get SOMETHING flying.

So they made the craft for those engines they had at that point.

Or even just fueling the landing tanks, if the point is to test the propulsion and structure and TPS. Those look like they would hold a few hundred tonnes of methalox. Even 100 tonnes would be enough to get to the Karman line and back.

Offline speedevil

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Re: ITS Propulsion The evolution of the SpaceX Raptor engine
« Reply #797 on: 02/18/2018 09:42 PM »
Falcon 9 never flies with partially-fueled tanks.

It sort-of-did-if-you-look-at-it-right.

In that early ones had lower amounts of LOX and RP1 on liftoff.
(densification and tank stretch).

It's not quite insane to imagine that at some point there might be a reasonable trade where it was easier to leave the tanks a bit long, and later upgrade the engines.

Of course, this did not happen with F9.

http://www.parabolicarc.com/2016/12/01/year-russian-launch-failure/
Quote
Dec. 5, 2010   Proton-M/ Blok-DM-3   Uragan-M #739 Uragan-M #740
Uragan-M #741   Failure   Rocket failed to reach orbital velocity after upper stage overfilled with propellant.

Seems to imply that all tanks do not always fly full.
This post from 2013 suggests it was overfilled by 1.5 tons
I could not immediately find a primary report.
« Last Edit: 02/18/2018 09:48 PM by speedevil »

Offline speedevil

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Re: ITS Propulsion The evolution of the SpaceX Raptor engine
« Reply #798 on: 02/18/2018 10:08 PM »
Moving the goalposts.
Launching with half-size tanks is not the same as launching with full-size tanks that are half-empty.

You also seem to think that SpaceX will build a BFR core with undersized engines, and then swap out those engines later on with the full-size version instead of just building a larger core for the larger engines.

Quote
It's not quite insane to imagine that at some point there might be a reasonable trade where it was easier to leave the tanks a bit long, and later upgrade the engines.
is very far from a ringing endorsement of the concept.

Vehicles have flown which have partially filled the tanks, rather than - for example - shrunk the tank for the mission.

I think they'll design the system to fly with the engines they think they are very likely to have at construction time, even if those engines are not quite ready yet.

May this in some unlikely contingencies result in an early test vehicle that flies best with underfilled tanks, sure.

It would however also not surprise me at all if the Raptor has now hit the IAC benchmarks, and is working on more.


Offline su27k

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Re: ITS Propulsion The evolution of the SpaceX Raptor engine
« Reply #799 on: 02/19/2018 02:00 AM »
Considering that the Merlin 1A (340kN thrust) is basically a subscale version of the Merlin 1D (845kN thrust), and SpaceX developed Falcon 1 and the three-engine Grasshopper and F9dev as "subscale" test vehicles, I don't see why a subscale raptor wouldn't be used on initial test vehicles.
There were interim versions of Merlin used on actual Falcon 9 missions, and I don't think I need to tell you that falcon 9 changed substantially during its service life.

They could use the subscale Raptor for BFR initially, but the vehicle (like Falcon 9) would have to be smaller.

no, it would not have to be smaller. It could launch with only partially fueled tanks.

When they were developing Merlin 1A, falcon 1 and falcon 9 1.0, they did not know much more thrust they will eventually get from the updated later merlin engine variants, and they really, really had to get SOMETHING flying.

So they made the craft for those engines they had at that point.
Falcon 9 never flies with partially-fueled tanks.

The first stage flew 15 times with partial fuel load under Grasshopper and F9R-Dev1 program, this is what the original comments are about: SpaceX can test full scale BFS by flying sub-orbital trajectory using underpowered Raptors and partial fuel load, which fits well with what Elon Musk suggested (testing BFS like Grasshopper).
« Last Edit: 02/19/2018 02:01 AM by su27k »

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