...Sea Dragon has nothing to do with the SpaceX Dragon capsule. The Sea Dragon was a proposed ocean-launched superrocket developed by the NASA Future Projects branch before it was shutdown in the mid 60's. It was designed to be built using many of the same shipyard tricks used to build submarines. Its fuel would be seawater cracked into its components hydrogen/oxygen by the tender craft. It could lift 550mT into orbit. The second stage of the Saturn V could fit inside of its massive rocket nozzle.
Quote from: Downix on 11/22/2009 10:36 am...Sea Dragon has nothing to do with the SpaceX Dragon capsule. The Sea Dragon was a proposed ocean-launched superrocket developed by the NASA Future Projects branch before it was shutdown in the mid 60's. It was designed to be built using many of the same shipyard tricks used to build submarines. Its fuel would be seawater cracked into its components hydrogen/oxygen by the tender craft. It could lift 550mT into orbit. The second stage of the Saturn V could fit inside of its massive rocket nozzle.Nitpick: Sea Dragon first stage was LOX / RP-1
Liquid Hydrogen is a LOT lighter than water. There's no way Sea Dragon wouldn't float, even if the first stage fuel was denser than water. In fact, with the RP-1 it needed ballast tanks to sink the base and bring it vertical. They were to be discarded at launch.I'm a little uncomforatable with using N2 to pressurize the tanks:1) It's a lot heavier than Helium. I suppose that much He might be too expensive, although it could be recovered from the spent first stage and re-used.2) Nitrogen tends to disolve in LOX causing combustion instabilities.If I was designing a Sea Dragon today, I might consider using He or N2 to drive a pistonless pump. (See Flowmetrics). The driving gas could even be produced by a gas generator.This would have the advantage of reducing the weight of the main tanks, while increasing the combustion chamber pressures, without requiring expensive, complicated turbo-pumps.
Even 30 to 50 psi would give the tanks an awful lot of strength.For a cylinder that ratio will mostly be equal to the depth of propellant in the tank. Sea Dragon's tanks are fairly squat, and at the end of the burn, won't have much depth. OTOH, I'm not an expert on exactly how N2 disolves in LOX. Could be some weird chemistry. I've heard anecdotal evidence of problems with N2 pressure fed rockets. Pump fed ones don't seem to have as many problems with N2 pressurization, because the pressure is about 1/10th as much. YMMV.
Yes, quite easily.The problem isn't that it could do that, the question is how do you pay for all that hardware to go fly on a single rocket -- that laundry list you suggest is worth billions and billions! More importantly: Do you really want to risk putting all those eggs in a single basket?If anything happened to that launch, you would lose everything in your entire *program* not just a single element.A Sea Dragon could just-about launch the equivalent mass of two International Space Station's in a single shot.While we would have loved to have had that capability ten years ago when we started lifting all those modules, there isn't much in the way of payloads around today -- or even planned in the next 20 years -- which would fill a single Sea Dragon each year -- and Sea Dragon's cost benefits required it to have a decent flight rate around 12 flights per year (just like every other launcher).If you didn't have that many launches, then the same old rules come into effect and the infrastructure costs start dominating the cost of each flight -- making the system non-viable again.The entire world's launch requirements -- government, military and civilian combined -- amounts to just a very small fraction of the 6,600mT of LEO lift capability which this system needed to make it worthwhile.And it's one hell of a gamble to go pay all the money needed to develop this in the hope that "if you build it they will come". That approach failed to work out very well for either EELV, did it?This needs a totally different business model to have any chance at all -- and I personally don't think NASA would ever choose to fly anything on it.Ross.
I never thought of stringing a few of them together like that for the rotational gravity at greater radius. An elegant solution! Another way to slow down the middle one further for docking/unloading would be have 7 of them, the central one, and attach 2 more end-to end so they go in 400 foot long spokes from the central point. With fairly short rotation. Gravity could almost feel natural at the bottom of those. Here's an interesting document I found...http://neverworld.net/truax/Truax_Engineering.pdf
I wonder how rigid Bigelow's inflatables will be... Perhaps a long inflatable habitat tube could touch the tips of all these tanks and keep them in proper alignment. Air pressure can provide a lot of rigidity. It would look like a bike tire with really really fat spokes and a big fat hub. This would enable useful volume at higher G's and connect access to the tips. You could go jogging along the entire outside wall of the inflatable tube. Mission duration is less relevant if you have lots of volume for astronaughts to roam at higher g-force. If they were attached stage to stage for the extra length, perhaps you could weld or bolt the nozzles together. That would provide even more space. Agreed that some well placed cables would be highly desirable. Central hub tank would have docking ports, nuclear reactor, and engines (perhaps vasimr). Or polywell drive...
Good idea. Water also is a good insulator for radiation. It can be cracked for fuel with solar power attached.