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ARCA Space's webpage for the Stabilo program has a description and an image. Hydrogen peroxide monopropellant? Reaction closer to the crew than the nozzle?

With thrust at the top, it seems that simplification due to inherent stability is a big advantage no, per @RussellBorogove's comment that's not right. While the word "Stabilo" appears frequently, the "aerodynamic stability system at the top" does not refer to any passive stabilization due to thrust-at-the-top at all. It's something different entirely.

Why was the thrust put at the top, and how was the attitude controlled during the phase of descent that used this engine?

Also, wasn't it tempting to use all that free oxygen to get a boost from combustion? Or was that going in the wrong direction - adding complexity where simplicity was sought?

The problem with steam is that it condenses, shrinking by a factor of roughly 1000 in volume. Was it difficult to ensure that the steam was always above its local boiling point (noncondensing) at each location and pressure, at least until well outside of the nozzle?

enter image description here

uhoh
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    Thrust at the top doesn't give any stability advantage. https://en.wikipedia.org/wiki/Pendulum_rocket_fallacy http://space.stackexchange.com/questions/9682/why-are-rocket-engines-at-the-base-of-the-rocket – Russell Borogove Apr 02 '17 at 08:48
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    I don't think it did work. They appear to have dropped this approach in favor of other speculative designs. – Organic Marble Apr 02 '17 at 15:31
  • @OrganicMarble do you mean the system failed in some way, or that the project ended without going anywhere further? – uhoh Apr 02 '17 at 15:44
  • From what I can tell none of the tests even lit the engine. – Organic Marble Apr 02 '17 at 15:44
  • @OrganicMarble Yikes - isn't the engine just steam from Peroxide decomposition? So much for simplicity! – uhoh Apr 02 '17 at 15:52
  • The propellant tanks store peroxide, not steam. The decomposition occurs in the combustion chamber, and the exhaust won’t condense until it’s well out of the nozzle. – Russell Borogove Aug 09 '19 at 15:06
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    Maybe it'd be better to phrase the question "how was X supposed to work?" rather then "how did X work?" given that it seems to have never actually launched. – user2705196 Aug 09 '19 at 20:36
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    Stabilo did refer to passive stability due to use of tractor engines (with the claim that towing a mass on a cable magically made it work). They even named it the "Popescu-Diaconu stabilization method", and hyped it up quite a bit early on. They're better at getting investors to give them money than they are at building rockets. – Christopher James Huff Aug 09 '19 at 22:35
  • I think you mean ".... than they are at launching rockets" @ChristopherJamesHuff they've built quite a few.... But I'm sure their latest water boiling aerospike rocket will launch real soon now –  Dec 18 '20 at 18:31
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    Building a lot of them hasn't made them good at building them. They can't even run their steam rocket above 1.85 bar (no, I didn't put the decimal in the wrong place) on the test stand because its tank leaks, and what comes out is a weak spray of steam and liquid water that barely makes the vehicle bounce in its suspending cables. They launch infrequently because their designs and fabrication are both incompetent. – Christopher James Huff Dec 19 '20 at 00:57
  • @ChristopherJamesHuff is there video? :-) – uhoh Dec 19 '20 at 00:59
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    @uhoh here: https://youtu.be/IUE2v9mNgIQ?t=161 – Christopher James Huff Dec 19 '20 at 01:06
  • @ChristopherJamesHuff I was totally disoriented for a moment! Where I live the internet ads are often game-related, so I thought that this was the leaky test stand https://i.stack.imgur.com/eBK87.jpg then the real video started and I still felt like I was looking at an animation. After a while the greater reality of what is (and isn't) being shown sunk in. Thanks! – uhoh Dec 19 '20 at 01:17
  • @ChristopherJamesHuff speaking of big launch batteries Are LiPo batteries more suitable for 1st stage electric power than Li-ion batteries? is currently unanswered. – uhoh Dec 19 '20 at 01:23
  • I still say they're good at building rockets, but I recognise the ambiguity in that people might think I was saying the build good rockets... and the sarcasm about their boiler rocket didn't come through at all. –  Dec 29 '20 at 00:54

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