Half a croissant, on a plate, with a sign in front of it saying '50c'
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LOX gel fuel

Grind water molecules and run away
  (+6, -3)
(+6, -3)
  [vote for,

The two main types of rocket propellant are solid and two-liquid fuels. (There are also hybrids using a solid fuel and liquid oxidiser, and monopropellants.)

Solid fuels are simple to use and need only simple rockets - basically a tube with a nozzle at the end. They have the disadvantages of being non-controllable once lit, and being quite costly. Worse yet, their specific impulse is not that great.

Two-liquid fuels are typically liquid oxygen combined with either liquid hydrogen (best for impulse per unit weight) or kerosene (best for impulse per unit volume). The liquids are pumped into a combustion chamber, mixed and burned. This has the advantage of using cheap fuels and giving a very good specific impulse. It's also throttlable. The drawback is the complexity (=cost, weight) of the engine.

I suggest a sort of hybrid fuel which would have the high impulse of two-liquid systems, but the simplicity of a solid rocket. (It would not have the throttlability of a liquid system, though).

Liquid oxygen and liquid hydrogen can be mixed, and are fairly stable (at least, they aren't hypergolic - they don't ignite spontaneously). Now add a few percent of a liquid which will gel at very low temperatures (might be kerosene) and mix (gently). With luck, you will get a semi- solid gel which is >90% LOX plus liquid hydrogen. With a bit of luck, this gel will behave much like a solid propellant (ie, it will simply burn once lit), but with the high impulse afforded by the intimate mixing of LOX and H2.

There are some issues with this. First, the gel is going to have to maintain its temperature by venting, just as LOX or liquid H2 alone do. This might lead to the formation of gas bubbles in the gel. On the other hand, provided the gel is surrounded by a porous mesh, boil-off from the surface should be favoured, and might prevent the insides from bubbling.

(You might even be able to use a porous, combustible solid in place of the gelling agent, soaking the liquids up like a sponge; I'm thinking of maybe open-cell porous aluminium or magnesium, or an open-cell plastic foam.)

Second, the mix may be sensitive to premature detonation. However, agents could be added to the gelling agent to stabilize the mixture (for example, free- radical scavengers) and make it semi- stable.

Finally, handling this is going to be a nightmare - it's going to be a semi- solid that wants to turn into a gas. However, there may be some way to prepare the gel in-situ, by filling the tank with the three components and allowing them to mix and gel in situ.

MaxwellBuchanan, May 04 2008

Sprengel explosives http://en.wikipedia.org/wiki/Oxyliquit
Been there, done that, dodged the shrapnel .... [8th of 7, May 04 2008]

Messerschmitt Me 163 http://en.wikipedia...esserschmitt_Me_163
Like off a shovel ... [8th of 7, Sep 10 2010]

T-stoff http://en.wikipedia.org/wiki/T-Stoff
Refuse all substitutes. [8th of 7, Sep 10 2010]

Rocket Lab's Viscous Liquid Monopropellant https://www.google....quid+monopropellant
"a non-Newtonian fluid containing both oxidisers and fuels", according to the patent [notexactly, Feb 27 2019]


       //be able to use a porous, combustible solid in place of the gelling agent, soaking the liquids up like a sponge .............. second, the mix may be sensitive to premature detonation //   

       [MaxB}, do you want the good news or the bad news ?   

       This technology is Baked. Unfortunately for your idea, LOX-based explosives using a porous matrix of sintered carbon as the fuel have been around for a while, and have found favour in some semi-fixed applications like quarrying.   

       Essentially, a prepared "core" of carbon is placed in a polystyrene Dewar, and LOX is poured in. A small booster charge of HE such as blasting gelatin is used to initiate the bulk explosion of the LOX device. It's nearly as cheap as ANFO, but ANFO is safer, and the big downside is the LOX which is a bit of a swine to handle.   

       Put your LOX gel on the top of your rocket as the payload and you might be getting somewhere ......   

       [+] anyway for an overcomplicated and extremely dangerous idea involving powerful oxidisers and combustion.
8th of 7, May 04 2008

       Hmm. It seems as if such mixtures are low-brisance explosives, with ignition propagating by shock rather than heat. I wonder, though, if a modification of the solid component (or gelling agent for a LOX/H2 mix) might stabilize things enough to permit a slower burn.
MaxwellBuchanan, May 04 2008

       p.s. Since you asked, I always want the good news.
MaxwellBuchanan, May 04 2008

       // I wonder, though, if a modification ..... might stabilize things enough to permit a slower burn //   

       We wonder too. We would very much like to know this. We encourage you to research the subject and do a series of increasingly large practical experiments. Just give us an hour or so, while we nudge our Cube into a slightly higher orbit .......
8th of 7, May 04 2008

       Martini fuel come in two mixes:   

       Vermouth suspended in Gin, which gives a high traditional value but a low score on popularity at launch.   

       The other is a suspension of the same Vermouth in Vodka.   

       The VOX gives a lower 'retch' scale with untrained palates but I believe there is a mix which combines the rich, light GIV mix with a mild offset.   

       I propose a series of gradually reducing flavour tempers such as Cointreau or Apple, which can be reduced and replaced with the more suitable Olive-on-stick suspensions as the night wears on.   

       The 1954 Gin, Vermouth and Cointreau rinse, combined with an anchovy-laden olive duplex is my suggested optimum fuel.   

       The entire mixture needs to be kept extremely cold, of course!   

       Now, THAT is an important chemistry problem solved!
not_only_but_also, May 05 2008

       I would mix this stuff very slowly in minute quanities, from behind a rather extensive set of safety barriers....and at a substancial safe distance. Bringing any hydrocarbon into contact with liquid O2 could be rather exciting.
Blisterbob, May 05 2008

       It should be not much worse than mixing a dry oxidant with a dry fuel (as in preparing gunpowder). Spontaneous ignition ought to be inhibited by the low temperature, methinks.
MaxwellBuchanan, May 05 2008

       Yes, [Max] is correct. You need an ignition source...... static electricity will do.   

       The components of black powder are mixed wet, then dried and "mealed". There are several grades of black powder, "Meal A" is the finest grain and has the highest burn speed, useful for blasting. 4-F BPGP is used in small bore weapons like pistols, and for priming; most long arms use 3-F as their propellant. Slower burn, more sustained gas pressure, higher muzzle velocity, and less chance of the firer ending up with a breechblock passing through their ocular orbit and exiting through the back of the skull (although sometimes they just lose their sight in both eyes, and all the fingers and the thumb on their left hand).   

       <later> NB this is not a joke, it is loud and messy and expensive and people come round asking questions, so beware.
8th of 7, May 07 2008

       I was shocked that the word cold appeared nowhere in this idea. Without a liberal addition of cold this recipe is impossible.
WcW, May 09 2008

       I've just read this idea and it appears to be crap. [-]
MaxwellBuchanan, Sep 05 2010

       Perish the thought. You need to test it before you make such pronouncements.   

       Don't forget to post links to the video, and the transcript of the fatal accident inquiry.
8th of 7, Sep 05 2010

       And here was I expecting it to be made from pureed salmon...
prufrax, Sep 08 2010

       //appears to be crap// Oddly enough, I had exactly that thought when you described the problem of separating out gas bubbles from the mass of semisolid/liquid. Cryogenic, high-energy proctology.
mouseposture, Sep 08 2010

       Consider hydrogen peroxide. A liquid, but laden with O! One could dissolve hydrogen into it under pressure, then jelly it with silica or some other nonoxidizable gelling agent. Wear gloves.
bungston, Sep 08 2010

       I'm sitting here eating a bagel with cream cheese, capers, red onion, tomato, and...lox, and then here is this idea.
normzone, Sep 09 2010

       //Consider hydrogen peroxide. ... One could dissolve hydrogen into it under pressure//   

       Does anyone know the solubility of hydrogen (or, indeed, hydrocarbons) in hydrogen peroxide? And wouldn't it react spontaneously?
MaxwellBuchanan, Sep 09 2010

       It might react spontaneously. Probably.
bungston, Sep 09 2010

       Correct, [bungs]. Hi-test peroxide will react exothermically with many organic compounds ,,,   

8th of 7, Sep 10 2010


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