CNES ESA Prometheus / Callisto proposal

[FutureSpaceTourist]

twitter.com/nasaspaceflight/status/1268900315128094728

ESA interest in Methalox and Reusability:

"ESA’s Future Launchers Preparatory Programme, Arianeworks is preparing an in-flight reusable demonstrater called Themis... will incorporate the Prometheus precursor engine.

Prometheus is the baseline for future evolutions of Ariane 6."

https://twitter.com/elonmusk/status/1268941050912968704

Methalox is the right propellant. Should be staged combustion & highly reusable.

[Asteroza]

Wait a sec, weren't they waiting on JAXA work package data for Themis/Callisto? Are they just pushing ahead with the engine development regardless then?

[gosnold]

Wait a sec, weren't they waiting on JAXA work package data for Themis/Callisto? Are they just pushing ahead with the engine development regardless then?

For Callisto yes, the engine is Japanese. AFAIK Prometheus is fully european, and that is what Themis will use.

[JEF_300]

What do we know about the engine for Callisto? Just that it's hydrolox, reusable, and made for propulsive landing?

[Rik ISS-fan]

twitter.com/nasaspaceflight/status/1268900315128094728

ESA interest in Methalox and Reusability:

"ESA’s Future Launchers Preparatory Programme, Arianeworks is preparing an in-flight reusable demonstrater called Themis... will incorporate the Prometheus precursor engine.

Prometheus is the baseline for future evolutions of Ariane 6."

https://twitter.com/elonmusk/status/1268941050912968704

Methalox is the right propellant. Should be staged combustion & highly reusable.

I think the best reply to this is Blue Origins motto; Gradantim Ferociter. (Step by step, ferociously.)

DLR and CNES are working on the test facility upgrades for Prometheus. It will take at least another year.
But possibly the CNES Perseus ARES rocket launch from CSG was in preparation for Calisto.

[Jakdowski]

PDF: Model-based Robust Transient
Control of Reusable
Liquid-Propellant Rocket
Engines
https://www.theses.fr/2020UPASS017.pdf

[Halken]

First post here. 

I was wondering why it seems as the prometheus engine is not a closed cycle engine. As I understand it, the reason for making the raptor engine closed cycle, that you avoid problems with the seals in the turbine when reusing the engine. So by making it a open cycle with shared shaft, they are inviting a host of problems when they have to reuse it. Have they optimized it more to get under 1m€ over the reuse design criteria?
To me this is kind of strange, as I would have specified designing an engine with the lowest running costs, including refurbishment instead of the up-front cost.

[Alpha_Centauri]

First post here. 

I was wondering why it seems as the prometheus engine is not a closed cycle engine. As I understand it, the reason for making the raptor engine closed cycle, that you avoid problems with the seals in the turbine when reusing the engine. So by making it a open cycle with shared shaft, they are inviting a host of problems when they have to reuse it. Have they optimized it more to get under 1m€ over the reuse design criteria?
To me this is kind of strange, as I would have specified designing an engine with the lowest running costs, including refurbishment instead of the up-front cost.

That only makes sense if you are reusing a lot of times. If you can make engines so cheap that you can afford to replace them after a couple of reuses, then there's no need for added complexity.

Europe's main experience on 1st stage engines is with the open cycle Vulcain. Europe hasn't developed a staged combustion engine, let alone a methalox one.

The mission brief for Prometheus is a very cheap and versatile engine that can be developed relatively quickly. For Europe it makes sense move incrementally, based on their industrial experience.

[Halken]

I agree with the staged approach. Can the engine be developed at a later stage to have staged combustion? Is staged combustion a necessity for keeping refurbishment costs low? 

[john smith 19]

First post here. 

I was wondering why it seems as the prometheus engine is not a closed cycle engine. As I understand it, the reason for making the raptor engine closed cycle, that you avoid problems with the seals in the turbine when reusing the engine.

Welcome to the site.

Raptor is a particular variant of the stage combustion cycle. Running both turbo pumps from either ox rich or fuel rich pre burners still leaves a very tricky sealing issue for the one where oxidizer and fuel are on opposite sides of the bearing.

So by making it a open cycle with shared shaft, they are inviting a host of problems when they have to reuse it.

GG cycle is mostly what Europe knows. Also the chamber pressure is about 1/2 that of an SC engine.  The obvious tactic is to put the fuel pump closest to the GG and the LOX pump after it. This should minimize the risk of a leak from either pump hitting something before it's contents evaporate.

Have they optimized it more to get under 1m€ over the reuse design criteria?
To me this is kind of strange, as I would have specified designing an engine with the lowest running costs, including refurbishment instead of the up-front cost.

It's a fair point.

Interestingly the CNES Reaction Engines collaboration looked at a simple, single use variant for their TSTO concept.

[john smith 19]

Europe hasn't developed a staged combustion engine, let alone a methalox one.

Incorrect. MBB and DLR worked on SC thrust chambers in the 200bar range in the 1960's.

[john smith 19]

I agree with the staged approach. Can the engine be developed at a later stage to have staged combustion?

No. Look at the structure of the SSME and compare it to that of any GG engine like Vulcaine, F1, J2 etc.

Is staged combustion a necessity for keeping refurbishment costs low?

Since no one outside of SX has any experience refurbishing rocket stages no one really knows.

It's said GG cycles deposit a lot of soot inside the GG chamber what is difficult to clean out and high thrust chamber temperatures polymerize the fuel in the coolant channels, which degrades heat reduction and encourages tube overheating leading to burn through.

But these are design choices. They are not laws of physics. 

Don't want GG coking? Don't use a long chain hydrocarbon fuel IE RP1 to begin with.
Don't want a sticky layer in your thrust chamber cooling channels? Use the oxidizer (which is what is done by all engines that use oxidizers that are not LO2 and was tested by NASA up to 40 000lb in the early 90's).

A full flow SC engine is more tolerant of seal failure between the pump drive turbines and the pump impellers.

A lot of this stuff could be found on the site if the search function was working properly. 

[Alpha_Centauri]

Europe hasn't developed a staged combustion engine, let alone a methalox one.

Incorrect. MBB and DLR worked on SC thrust chambers in the 200bar range in the 1960's.

So they haven't actually developed a complete staged combustion engine that can actually be used on a launcher.

Yes, they have done some work on staged combustion. There were test firings a few years ago as part of an FLPP research programme.

The point is thats not enough experience to make a production staged combustion methalox from scratch without risks of long delay or poor performance.

[Halken]

It will be interesting to see. I don't think there is much debate about methane and LOx being the propellant and oxidizer of choice going forward, if we want to reuse.
If I understand it correctly, then seals in the turbine pumps are less of a problem in a full flow engine, because leakage primarily means that the efficiency of the turbine goes down.

I can see that the raptor, which is 2 mN instead of 1,2 has a target price of 2m$, so slightly more expensive pr N, but it also have a target of 50 flights. BOs BE4 is slightly worse at 2,4mN and 8m$ and 25 flights. The real question is if prometheus can keep up with the raptor cost wise over 50 flights, if the raptor also is slightly more efficient. The raptor does seem to be the engine to beat, and I worry that while prometheus is good, it might not be good enough. Too little too late,  if you want to stay in the game. We europeans can move when we want to, but some things take time, and while we're developing these things, the competitions are also moving, and they appear to move faster than us. we don't need to beat them at this game or lead the pack, but if we want to stay relevant in the launch services, we need to 1) catch up and 2) keep up. ULA, SX and BO has changed the game, and one can only hope that the powers that be at Arianespace recognize it for what it is, and is accelerating R&D accordingly. Development and competitions will happens much faster than it has in the past. To catch up and keep up, or not to, is a strategic decision that Arianegroup has to make. As competition grows more fierce, all decisions has to be made on a strict commercial basis.

One thing I wonder about, is that both SW and BO has chosen around 2 mN, while the prometheus is 1,2 mN?

EDIT: I have just read this, and it seems as some gets it. Are there any other interesting reads out there about this?
https://satelliteobservation.net/2018/06/02/cnes-director-of-launchers-talks-reusable-rockets/

[john smith 19]

ULA, SX and BO has changed the game, and one can only hope that the powers that be at Arianespace recognize it for what it is,

Firstly that's mostly SX. BO look like they may "change the game"
As for ULA Vulcan is basically yet another TSTO ELV 

and is accelerating R&D accordingly. Development and competitions will happens much faster than it has in the past. To catch up and keep up, or not to, is a strategic decision that Arianegroup has to make. As competition grows more fierce, all decisions has to be made on a strict commercial basis.

Aranespace is no more a commercial company than ULA. Unfortunately it innovates when it's told to innovate. 

The actual process is
ESA decides it needs a new LV
CNES designs it. Usually of what was in vogue in the US in the previous 1 or 2 decades. Hermes modeled DynaSoar, Ariane 5 modeled Shuttle, Ariane 6 will model Atlas V. 
The design gets handed to industry to build
Arianespace markets it.

As it stands this process results in incremental refinement, not step changes in performance.

We'll see if the next cycle produces anything better.

BTW it would help if you broke up your prose a bit. Walls of text are tough to read.

[libra]

Oh great, ye old Diamant launch complex ! Last launch from there was in September 1975. More or less the exact day my parents got married. 

[edzieba]

While FFSC may be the 'best' for a highly re-usable engine, maybe best is the enemy of good enough here: if Ariane Group can get Prometheus into a good-enough and cheap-enough workable state for use in launcher, that beats a theoretically better FFSC engine that may take an extra decade to make its way to production-ready status (and assumes funding for such a high-risk long-term R&D endeavour is forthcoming).

[Rik ISS-fan]

Halken welkom on NSF. Sorry I had a laugh because you wrote mN (10^-3) instead of MN (10^6).
(I don't have problems with how you wrote your post.)
I think there is at least an order of magnitude (10x) difference in development budget for Prometheus compared to Raptor or BE-4. Thus Prometheus is far less efficient and advanced.
I think Prometheus and Raptor have roughly the same Nozzle/combustion-chamber size. Prometheus is 1,2MN at ~15MPa, while Raptor is 2MN at 30MPa chamber pressure. If a follow on engine design with the Prometheus nozzle and staged combustion this would also be ~2MN.
I view Prometheus as comparable with a LOxLNG merlin engine, it's for low reuse. (I view a testbed engine as reusable as well, thus Europe has experience with reusable engines.)

Prometheus development is pushed by industry. I think it builds on the work industry did on the Romeo engine.
European govenmnents remember how Arianespace got it's dominant market share. The reusable space shuttle would launch much more affordable than expandable launchers. Thus the US phased out Atlas, Delta and Titan. The Space shuttle reuse didn't work out as planned, and Europe with it's Ariane IV got a dominant launch market share that it still has.
Sorry, but I'm not at all convinced a reusable launcher is the path to go for Europe. Without a much higher (>4x) launch rate the businesscase doesn't work. Let's explain (again).

For a single company with minimal production ascets and centralized production reuse works at low rate. Politically work share is divided in Europe. Italy builds the solids (P120C), France the core (LLPM) and engines, and Germany the upper stage (ULPM). A reusable Ariane Next would diminish the Italian and France work share. At the planned Ariane 6 rate of 11/12 launches annually, and 4x reuse; Germany is happely manufacturing 11/12x ULPM. France only builds 3x LLPM with 21x Prometheus engines and 11/12 upper stage engines. Italy is left supplying parts for the engines and it's Vega work. Both France and Italy won't be happy.
And now I only dealt with the main launcher components. Many smaller member-states will also lose a lot of work = jobs.

I'm in favor of the Prometheus R&D project. But I doubt it will be implemented.
I think the ETID would be a beter engine design base to develop a staged combustion and/or reusable stage.  But that's just my opinion.

[Steven Pietrobon]

Arianespace dominated because they were competing against a government bureaucracy (NASA) and traditional US military industrial complex (Boeing and Lockheed Martin) companies. Making that same bet against a visionary led company whose sole purpose is to lower the cost of space flight (SpaceX) is and is going to be highly unlikely to win.

Besides, the future is not companies being both the launch vehicle and launch service provider, but separate companies, one providing reusable launch vehicles and the other launching satellites on those reusable vehicles. This way, a launch vehicle manufacturer has lots of business since they can sell their vehicles to launch service providers all over the world.

[Hobbes-22]

What's the benefit of splitting those functions? Arianespace sells its launch services all over the world right now.