Ice rocket

[rogers_buck]

I don't want to get bogged down in specific engineering details, but I'll give a hypothetical case to illustrate the basic idea I'm presenting here. Afterwards, I'll single out the base concept so the minutia of materials, etc., doesn't swamp the basic idea.<br /><br />Water is a valuable comodity in orbit. It can be used to sustain life, it can be split and used as rocket fuel. Imagine two concentric conic tanks made from thin walled plastic that are set up on a launch pad. Under the tanks is a module that contains aero-spike engines, pumps, guidance, etc.. The thin walled plastic tanks are filled with a cryofluid like liquid N2 and sprayed with water. Eventually, the two tanks are encrusted in a rock-hard snow cone of frozen water. When the desired mass of ice is accumulated, the tanks are filled with liquid O2 and liquid H2 in place of the nitrogen and a plastic skin is pulled over the ice cone. The engines are ignited and the whole snow cone blasts its way to orbit. Once in orbit, the ice rocket spins about its axis and warms in the sun. As the ice melts, the water is pumped into one of the empty tanks where it is safe for harvesting as needed. Presumably, the aerospike engine module would detatch and reenter for reuse.<br /><br /><br />Ok, a lot of engineering details in there to pick nit, and that's not the point of the post. The point of the post is simply this. When materials get really cold they get really strong. What if the structure of the rocket could be a frozen substance that would itself be of use. Water is just one possibility of many. The substance doesn't have to be pure. Chicken soup, jello, water with solids in suspension. The idea is to make a cheap pad assembled vehicle held together by the coldness of its fuel.<br /><br /><br /><br /><br />

 

[shadowsound]

The main thing is to keep the lox away from potentially combustible material. Think major boom!<br /><br />Other than that I am a major fan of this type idea.<br /><br />I also think that volatiles can be shaped and sent into or under maximum thrust. Add electricity or heat and separate the base elements into useful items.

 

[vogelbek]

I'll do as asked and not naysay the engineering details. Instead, let me rain on the parade via rocket staging theory. What it sounds like you're proposing is replacing our aerospace structures with ice (or other useful material)<br /><br />Unfortunately, for a single stage rocket, we need to have the "structure" (in our case, structural payload) be no more that a few percent (<5%) of the total vehicle mass. So the question is, can we make a vehicle made of ice that is strong enough to survive the harsh loading and vibrations of launch (while still being light enough)?<br /><br />I've heard that one can mix straw into freezing water and make bricks that are resiliant enough to bounce off bullets. Perhaps we could get clever with carbon or glass fibers to make a carbon-ice composites.

 

[rogers_buck]

How to distill the problem to a simple form for analysis... Perhaps there is a shortcut by analogy.<br />1) Could an N segment solid stick make it to LEO with X payload?<br />2) If so, what is the upper limit for X?<br /><br />If we assume that X is a hard frozen nose-cone of water in a trash bag, that will give us a general cost/kg of water delivered to orbit. Approx cost of SRB/kg of water.<br /><br />Not quite the model since structural payload is important to the concept, but it would seem to give a upper limit cost.<br />

 

[webtaz99]

They couldn't even make a sea ship out of ice (as was tried in WW2), much less a rocket ship. <div class="Discussion_UserSignature"> </div>

 

[barf9]

Oh, could have built it, and it might have worked just fine, but it was too limited in use to be worth the massive resource expenditure, a 2 million ton ice ship limited to the north atlantic? By the time construction would have begun there was no critical mission. <br /><br />Pykrete 14% wood pulp

 

[why06]

Is there anyway you could make... I don't know.. A diagram of it with a Paint program or something. It doesn't have to be good I just need to visualize it. Trust me it helps. <div class="Discussion_UserSignature"> <div>________________________________________ <br /></div><div><ul><li><font color="#008000"><em>your move...</em></font></li></ul></div> </div>

 

[gunsandrockets]

"The point of the post is simply this... What if the structure of the rocket could be a frozen substance that would itself be of use. Water is just one possibility of many."<br /><br />Usefull principle. But as ususal the devil is in the details. What are the tradeoffs? What mass advantage vs disadvantage does it entail?<br /><br />Your basic idea is to reuse structure as consumable payload. The biggest problem with this is that rocket structure is already a tiny fraction of total rocket mass, and that structure is very specialized in order to reduce that mass. The basic function of structure is to enclose volume and resist various external forces-- acceleration, pressure, temperature etc. Making consumable material function in such a fashion is probably extremely ineffecient.<br /><br />Because of that the most common proposed reuse of what would normally be expended rocket structure, is as storage tanks or as 'wet' habitats.<br /><br />But there still may be a practical use for your basic idea, just turned around some. Instead of having structure reused as consumable payload, how about making the consumable propellant serve a secondary purpose as the rocket structure?<br /><br />For example take a big block of ice in space, perhaps carved out from some comet or boiled off from some asteroid, and make caverns in it to contain pressurized habitat areas and attach a rocket to the tail for propulsion. The (probably nuclear) rockets could be fed by melting the ice block, piece by piece, and feeding it into the engine.<br /><br />Perhaps the easiest way to design such a ship would be a rocket engine cluster attached to a very long truss 'spine'. The spine would serve as a backbone upon which the frozen material would be stacked. Or the spine could be melted into a large frozen block of material like a popsicle stick!<br /><br />A thin mylar air-proof bag might tightly surround the ice block, doing double duty. It would contain evaporation from escaping into space and the c

 

[annodomini2]

Interesting idea, as water is probably the most valuable resource for humans living in space how much ice would it take to offer significant radiation protection? i.e. wrap the ship in ice to protect the crew? also there is then significant resources which also serve as a dual perpose. <div class="Discussion_UserSignature"> </div>

 

[gunsandrockets]

"...how much ice would it take to offer significant radiation protection?"<br /><br />A depth of three feet of water is the gold standard as far as radiation shielding. A similar mass of ice would do the same. Hence the benefit of carving habitat 'caverns' inside your block of ice.