Europe joins the re-usability bandwagon?

[TrevorMonty]

I'm a bit shy on my math here but:

What would be the implications of a (reusable) first stage with a slightly ad-hoc tripropellant combination?  Say, an engine cluster containing both Prometheus and Vulcain engines?  The Prometheus engines can do much of the thrust at the start of flight, light the A5 / A6 do with solids, and then swap to Vulcain only later in the primary flight, improving the specific impulse of the stage over all?  Then use the Prometheus engines for landing, and the boost back and / or re-entry burns, if those exist?  Would this help to reduce the extreme wet mass requirements of re-usability from an all Prometheus stage?  Would using hydrogen in a first stage make it unacceptably high volume?

The extra tanks required for LH would add so extra dry mass that any gains from LH higher ISP would be loss. LH is better as US propellant.

[Rik ISS-fan]

I also think the tripropallent combination is to complicated. I expect a 2.5 stage design beside a two stage design. Ariane 5 and 6 are 2.5 stage designs. The solid boosters could be replaced by (reusable) liquid boosters. I expect only two liquid boosters will be used. This will be a heavy version of the launcher. A lighter version will lift an upperstage and possibly an in-orbit/kick stage.
Let them mess around with Callisto and/or other small demonstrators to develop efficient stage recovery methodes.
SpaceX used landing legs on Falcon 9, but plans to use a catch tower for super heavy and starship. Rocketlab plans parachute recovery with mid-air capture. There are also ideas for wire catch mechanisms in Europe. I think tests on small rockets will have to show what is the best option. They need to plan for the fact they will destroy a couple of vehicles, that's required to figure out the best stage recovery method. If they launch the demonstrator to more than 100km altitude with scientific payloads each launch also has another use. I expect this will cost roughly half a billion euro and take several years.
I think the (first stage of) Sirius1 from Sirius Space Services, could be a succesor to Callisto. Or the first stage of one of the ther European micro launchers. Themis is to large for a technology demonstrator, and it requires the engines to be operational, that delays the stage recovery tests a lot.
The Sirius 1 uses 38kN pressure feed LOx LCH4 engines, simple, thus cheap and reliable.

[libra]

TAN was an interesting innovation for tripropellant rocketry, unfortunately it seems to be locked at Aerojet...

[Solarsail]

I'm a bit shy on my math here but:

What would be the implications of a (reusable) first stage with a slightly ad-hoc tripropellant combination?  Say, an engine cluster containing both Prometheus and Vulcain engines?  The Prometheus engines can do much of the thrust at the start of flight, light the A5 / A6 do with solids, and then swap to Vulcain only later in the primary flight, improving the specific impulse of the stage over all?  Then use the Prometheus engines for landing, and the boost back and / or re-entry burns, if those exist?  Would this help to reduce the extreme wet mass requirements of re-usability from an all Prometheus stage?  Would using hydrogen in a first stage make it unacceptably high volume?

The extra tanks required for LH would add so extra dry mass that any gains from LH higher ISP would be loss. LH is better as US propellant.

I wish I knew how to run the numbers on that.  What struck me was the extreme Δv requirements of accelerating to stage velocity and then braking for reentry within this thread: https://forum.nasaspaceflight.com/index.php?topic=41330.180  (Maybe I should have posted there instead?  More context..)

The optimum separation velocity leaves a amount of work for the upper stage to do, and needs a huge first stage for it.  Thus my thinking of a stage splitting the differences between Prometheus and Vulcain engines.  You would need a less extreme stage volume than a Delta IV by doing much of the impulse in denser methalox, you would raise the average effective specific impulse for the flight (for a high Δv flight) and have restart / landing capabilities in the less efficient engines.  At least, landing burns look to require fairly little Δv, so the reduced isp is less painful there.  Thus the heterogeneus engine cluster, sitting between low-isp, higher density and higher stage T/W (including tank mass) on some engines and higher isp, lower density, lower stage T/W on the others.  And accomplishing this variable ISP behaviour without needing exotic engine designs.  Admittedly, by adding an exotic cluster of engines.

[FutureSpaceTourist]

https://twitter.com/andrewparsonson/status/1635377628743098371

Interesting development: @esaspaceflight announced on 10 March its intention to conduct a study on a future European family of reusable launch systems with a human space transportation capability. The study is part of the agency's Future Launchers Preparatory Programme.

https://esastar-publication-ext.sso.esa.int/ESATenderActions/details/58379

STUDY ON A FUTURE EUROPEAN FAMILY OF REUSABLE LAUNCH SYSTEMS ENCOMPASSING HUMAN SPACE TRANSPORTATION CAPABILITY, BASED ON COMMON BUILDING BLOCK AND REUSABILITY
1-11695

Intended
Clarification Request Deadline
N/A
Closing Date Extension Request Deadline
N/A
Announcement Date
10/03/2023
Last Update On
10/03/2023 11:48 CET

Update Reason
New Tender Action
Directorate
Estabilishment
ESAHQ
Open Date
N/A
Closing Date
N/A
ECOS Required
No
Classified
No
Price Range
200-500 KEURO
Responsible
Giorgio Tumino
Initiating Service
STS-F
IP Measure
N/A
Prog. Reference
E/A222-01 - FLPP Human Sp Transp
Tender Type
Open Competition
Open To Tenderers From
BE+CH+ES+FR+IT
Technology Keywords
Products Keywords

If you wish to access the documents related to the tender action and/or express interest (in case, you are assigned to a Bid Manager role), you have to log in

[TrevorMonty]

https://twitter.com/andrewparsonson/status/1635377628743098371

Interesting development: @esaspaceflight announced on 10 March its intention to conduct a study on a future European family of reusable launch systems with a human space transportation capability. The study is part of the agency's Future Launchers Preparatory Programme.

https://esastar-publication-ext.sso.esa.int/ESATenderActions/details/58379

STUDY ON A FUTURE EUROPEAN FAMILY OF REUSABLE LAUNCH SYSTEMS ENCOMPASSING HUMAN SPACE TRANSPORTATION CAPABILITY, BASED ON COMMON BUILDING BLOCK AND REUSABILITY
1-11695

Intended
Clarification Request Deadline
N/A
Closing Date Extension Request Deadline
N/A
Announcement Date
10/03/2023
Last Update On
10/03/2023 11:48 CET

Update Reason
New Tender Action
Directorate
Estabilishment
ESAHQ
Open Date
N/A
Closing Date
N/A
ECOS Required
No
Classified
No
Price Range
200-500 KEURO
Responsible
Giorgio Tumino
Initiating Service
STS-F
IP Measure
N/A
Prog. Reference
E/A222-01 - FLPP Human Sp Transp
Tender Type
Open Competition
Open To Tenderers From
BE+CH+ES+FR+IT
Technology Keywords
Products Keywords

If you wish to access the documents related to the tender action and/or express interest (in case, you are assigned to a Bid Manager role), you have to log in

ESA doing what it does best, studies.

[Asteroza]

Less than a million euros is enough to keep some grad student seats warm...

[deltaV]

IMO there are two lessons to learn from SpaceX and the last decade of US government space purchases: reusable launch vehicles reduce costs if done well and competition reduces costs if done well. Europe seems to be learning the first lesson but shows no signs of learning the second lesson. I don't think Europe will succeed at producing a cost effective launcher unless they learn both lessons.

[Rik ISS-fan]

IMO there are two lessons to learn from SpaceX and the last decade of US government space purchases: reusable launch vehicles reduce costs if done well and competition reduces costs if done well. Europe seems to be learning the first lesson but shows no signs of learning the second lesson. I don't think Europe will succeed at producing a cost effective launcher unless they learn both lessons.

You are overlooking two prerequisites.
Long term launch demand should be high enough to sustain serial production on the reusable launcher.
And only when duplication of work is avoided, competition reduces cost.

The quantity of the long term launch demand that is uncertain in Europe. In Europe's launch history (from 1979 to now) only 13 years 10 or more launches took place (from CSG). Only two years 2000 & 2021 (17 &)15 or more orbital launches took place by all European launch programs. I'm doubtful 12 launches annually is enough to get cost benefits from reuse.
The way European launcher development works; results in work-packages being distributed over several ESA member-states. Thus work is distributed and duplication of work happens, unavoidably.

And I've an example where another competitor practically kills the market. Under ESA BOOST! program three companies in Germany (ISAR Aerospace, RFA and HyImpulse) and two companies in the UK (Skyrora and Orbex) were developing small launchers. Now Avio is also (re)entering this marketplace with the VEGA STS demo. This fully (Norther Europe) state funded project ruins the European commercial small launcher market. While STS strives to be a reusable launcher.
The this is 'if done right' is very difficult with all the politics involved.

[Rik ISS-fan]

STUDY ON A FUTURE EUROPEAN FAMILY OF REUSABLE LAUNCH SYSTEMS ENCOMPASSING HUMAN SPACE TRANSPORTATION CAPABILITY, BASED ON COMMON BUILDING BLOCK AND REUSABILITY
1-11695
....
Open To Tenderers From
BE+CH+ES+FR+IT
...

ESA doing what it does best, studies.

And it's only open to companies from a limited subset of ESA memberstates.