Author Topic: CNES ESA Prometheus / Callisto proposal  (Read 28415 times)

Online FutureSpaceTourist

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Re: CNES ESA Prometheus / Callisto proposal
« Reply #120 on: 01/09/2018 07:04 PM »
Quote
Interesting #Prometheus / #Callisto Ariane Next video via @CNES and blackbear studio @DLR_en

https://twitter.com/dutchspace/status/950798523355815936

Video attached.

Offline john smith 19

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Re: CNES ESA Prometheus / Callisto proposal
« Reply #121 on: 01/10/2018 05:50 PM »
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Interesting #Prometheus / #Callisto Ariane Next video via @CNES and blackbear studio @DLR_en

https://twitter.com/dutchspace/status/950798523355815936

Video attached.
Watched it.

Not worth the download. Nothing new added.  :(

TBH I'm underwhelmed by Prometheus.  It looks like an engine that could have been built any time within the last 30-40 years.

It's a GG cycle Methalox engine with a shared turbine drive. Quite a  lot of it will be 3d printed. It's got quite a good throttling range compared to other engines produced in Europe (Europe, not parts of the FSU).

But.

No variable Isp to maximize payload to orbit (which is what this is all about).
No gas chamber tapoff to eliminate a GG yet still have "full flow"
No cutting edge chamber pressure or nozzle design to increase Isp.

And what are these features that will promote easy and fast reuse? So far it looks the ECU is going to do most of the work. Will they still use ball and roller bearings for it?

As others have noted CALLISTO is not a micro launcher. It's a test vehicle. The correct analogy would be to Grasshopper.

I'll note that with SX booster recovery (and reuse) as a fact all other recovery and reuse strategies hare much riskier, simply because none of them have ever been actually tried, let alone succeeded.

This clean sheet approach also means there is no opportunity to do any early testing on Ariane5, and probably none on A6, although it may not be too late to design in the hooks for recovery testing (like space and connections for an OBC and it's power, given 1st stages typically lose 1Kg of payload for 13Kg of 1st stage mass, meaning you could put the hooks in place without loosing any major final payload).
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Online Alpha_Centauri

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Re: CNES ESA Prometheus / Callisto proposal
« Reply #122 on: 01/10/2018 06:07 PM »
It's designed to be ridiculously cheap, not state of the art.

Online AncientU

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Re: CNES ESA Prometheus / Callisto proposal
« Reply #123 on: 01/10/2018 06:23 PM »
...

TBH I'm underwhelmed by Prometheus.  It looks like an engine that could have been built any time within the last 30-40 years.

It's a GG cycle Methalox engine with a shared turbine drive. Quite a  lot of it will be 3d printed. It's got quite a good throttling range compared to other engines produced in Europe (Europe, not parts of the FSU).

...

Sounds perfect for a low cost reusable engine along the lines of Merlin (but no coke build-up).  Additive manufacturing was not available for the last 30-40 years -- and this is a huge contributor to cost efficiency and thrust-to-weight.  Rocket engine technology-wise, yes, it could have been made 40 years ago... but wasn't, and neither was Merlin. 

If you're still judging engines on 'performance' alone -- see Merlin.
« Last Edit: 01/10/2018 06:25 PM by AncientU »
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Offline john smith 19

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Re: CNES ESA Prometheus / Callisto proposal
« Reply #124 on: 01/11/2018 09:16 AM »
Sounds perfect for a low cost reusable engine along the lines of Merlin (but no coke build-up).
The simple answer to avoiding coke build up (and not having to re-size your turbo pump if you have to change fuels) is to use LOX cooling, demonstrated by NASA  around 1991 in a 40 k lb pressure fed test engine they use. Rotary Rocket also did work in this area and found no showstoppers. IOW 3 decades ago.
Quote from: AncientU

 Additive manufacturing was not available for the last 30-40 years -- and this is a huge contributor to cost efficiency and thrust-to-weight.
It's probably been available only for the last 20 years.

Before that you'd be looking at phote-etching/diffusion bonding, vacuum melting/casting with lost wax/foam and ceramic bag dross filtering if necessary, or electroforming or EDM/ECM as "rapid prototyping" approaches.

Quote from: AncientU

  Rocket engine technology-wise, yes, it could have been made 40 years ago... but wasn't, and neither was Merlin. 
True.
Quote from: AncientU
If you're still judging engines on 'performance' alone -- see Merlin.
I'd have ignored RP1 and selected the best available hydrocarbon that was not LH2. IIRC they are all pretty similar except for Propyne (Old name Methyl Acetylene) , which has a strained bond that gives it several seconds better Isp. AFAIk on this scale all reasonable propellants (IE not NTO and Hydrazines) have cost levels "in the noise"  and handling restrictions no worse than LOX, which is the obvious "performance" oxidizer in any case (CTF fails for the same reason as NTO and the Hydrazines).
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.
So you're going to Mars to seek a better life. What does that mean to you? Always spot a fanbois by how they react to their idols failures.

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