Sea Dragon

The Sea Dragon rocket was a concept put forth by Robert Truax in 1962. It was a proposal for a two stage launch vehicle capable of putting over 500 tons into LEO, potentially at a cost of around $100/kilo.

In order to save costs, the vehicle was planned to be constructed out of low cost materials, such as 8mm steel sheet, and launched from the open ocean. Evidently, this was considered to be feasible with 1960s tech (The Astronautix article claims that Aerojet had previously tested the launch concept), but funding dried up post-Apollo.


First off, do y'all think this concept would have been feasible, and able to deliver the stated performance goals?

Second, how might our space program look different if this program had in fact been successful. I think we would have a much larger presence in LEO, with such a (relatively) cheap launch capability.
 
IIRC weren't there some technical difficulties when dealing with engines that size? I'm sure I can remember reading that either on here or some other forums when this was discussed. But assuming that you can get the kinks worked out before the hippies and environmental protesters start happening you've certainly given the space industry a shot in the arm, plus probably butterflied away the space shuttle.
 
I can't comment on the technical feasibility issues, but wasn't one of the big problems with Sea Dragon that nobody had that much payload to launch? I mean, correct me if I'm wrong, but that's about enough payload to put up the whole ISS in one shot, isn't it?
 
Regardless of economics (what in the 1960s can justify flying a Sea Dragon more than once per year? Can recon sats and geostationary coms sats and interplanetary probes even be loaded onto the same booster? If not, you're going to be flying empty most of the time), combustion instability will likely be a problem. F-1 had issues that took years to resolve from the project's start in the 1950s--Sea Dragon's first stage engine is big enough to deep-throat a Saturn V. Combustion instability will be magnified with it. Not to mention that enormous LH2 engine on the second stage.

Can it be done? Sure, with concerted national effort and a lot of money. Can it be done quickly and with a reasonable budget? Probably not. Will it fly often enough to achieve low costs after it's built?

I say "hell no."

Now, the later, scaled-down variant (Excalibur) has potential. But Sea Dragon is the sort of thing that is economical and feasible only if the US dedicates itself to bringing about 2001: A Space Odyssey by 1980.
 
Problem with low budget equipment is it fails much more often. NASA suceeded it getting the US space exploration off and running by realizing the need to focus on quality performance.
 
I can't comment on the technical feasibility issues, but wasn't one of the big problems with Sea Dragon that nobody had that much payload to launch? I mean, correct me if I'm wrong, but that's about enough payload to put up the whole ISS in one shot, isn't it?

A valid point, and probably one of the main reasons why it got canceled.




However, I think that a reboot of the technology would be viable today, or possibly in the 1970s/80s in place of the Shuttle. Although the issues with combustion instability would have been severe, and I'm not sure exactly how you would deal with them.
 
A valid point, and probably one of the main reasons why it got canceled.




However, I think that a reboot of the technology would be viable today, or possibly in the 1970s/80s in place of the Shuttle. Although the issues with combustion instability would have been severe, and I'm not sure exactly how you would deal with them.

Fluid modeling has advanced by leaps and bounds since the 1960s, as it requires computing power. You can reduce costs of development by figuring out how to mitigate that using computers. It'll still be expensive, mind you (engine development costs go up non-linearly as pressures increase).

Even today, Sea Dragon is a solution in search of a problem. Barring full-scale commitment to a Mars Program or an O'Neill colony with solar power satellites, there's nothing that justifies that kind of mass. Even Musk isn't saying that SpaceX will launch that much mass without a millions-to-Mars goal.

In short, Sea Dragon just doesn't have a good reason to exist without electing the membership of the National Space Society to fill every major government position.
 
Aww...everyone's basically already said everything I was going to while I was looking up my Standard Sea Dragon Rant (tm). :( Anyway, yeah. Two giant engines, each many, many times larger than the F1 which took almost two years to beat its struggles with combustion instability makes combustion instabilities certain. Then, once you have it, there's no payload to justify it.

Anyway, the other issue I'll raise is the cost. The cost of about $60-$600 kg was cited in 1962 dollars. Inflation since then turns that into more like $460-$4600/kg in 2012 dollars. SpaceX's price for Falcon Heavy sits at $2412/kg, and reuse of the first stages (something outside the "minimum cost design" framework that lead to Sea Dragon) should cut that by half or more considering how much of the costs lie in building the hardware. Sea Dragon's interesting, but there's better ways to get to cheap spaceflight.
 
IIRC weren't there some technical difficulties when dealing with engines that size? I'm sure I can remember reading that either on here or some other forums when this was discussed. But assuming that you can get the kinks worked out before the hippies and environmental protesters start happening you've certainly given the space industry a shot in the arm, plus probably butterflied away the space shuttle.

Larger engines seem to have combustion instabilities (the vaster size means there's more room for chaotic fluid interactions in the gas) and the engines the Sea Dragon would require would be huge. So you'd either have to do some complex engineering and create a new type of engine, which is expensive and contrary to the Big Dumb Booster concept, or you are going to have to do lots of engine testing and prototype iterations, which is very expensive and also contrary to the Big Dumb Booster concept.

With modern modeling, you might be able to reduce the cost some by doing a lot of the prototyping in software simulations, but there is ultimately no substitue for firing up a prototype and seeing what happens, since there are limits to how accurately you can model flows.
The other thing computers might do is to allow you to use a whole bunch of smaller engines. Having something like 500 Merlin engines where you are almost certainly guaranteed to have ten or a dozen engine-outs sounds crazy, but with modern control software and the rugged compartmentalization that Sea Dragon construction allows, it might just work.
 
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Archibald

Banned
For the anecdote, the only pressure-fed rocket ever in service was the french launcher Diamant. It's L-17 "amethyste" first stage was the biggest and more powerful pressure-fed stage ever build.

After extensive research it seems that no-one in America, not even Truax, ever realized that fact. :confused:

So I had to correct that issue in my little space TL.
The shuttle get's canned and the space station is build using the Lockheed Agena as a space tug.
What is interesting is that Diamant and Agena by pure coincidence have the same narrow diameter of 5 feet. An Agena would fit a Diamant first stage like a glove.
The result is Diamant-Agena, or Diagonal. Through Diagonal, Lockheed become familiar with pressure-fed rocketry; and unlike Truax, Lockheed is a household aerospace name.
Next step is Lockheed recruting Germans from Marshall; they bring the Saturn cluster concept with them, and apply it to Diagonal.
The end result is a family of bigger and bigger pressure-fed rockets (see below)
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I'll admit that I love the Sea Dragon concept, partly because I think the focus on safety and quality and miniaturization has killed spaceflight, but mostly because its awesome. The thing is effectively a battleship that is its own shell.

That said, I see a hard time of any need for it. You need a scenario that requires lots of stuff in space FAST. Which are hard to come up with. An imminent alien invasion or a dino-killer would work, if you knew about them 5 to 10 years in advance. Even then something like Orion is more probable because if you're looking at near-extinction level events 1-2 million cancer deaths start sounding like acceptable levels of casualties.

Of course the Apollo imperative could itself be your need for lots of stuff in space fast. So many of the engineering challenges get so much easier if the weight constraints are dramatically relaxed. Going this route probably requires handwaving the combustion instablity problem and it probably also requires tinkering with the path dependency of rockets way back in the Goddard and early Von Braun days, and somehow getting navies more involved in the whole process. Just to throw one crazy notion out there, if the state of the art on rocket engines was a little more advanced when WWII rolled around, but the control and guidance problems were still there and were perhaps more apparent, I could see Hitler approving some lunatic project to make a big human-controlled behemoth that would drop tons and tons of explosives over London, perhaps with the vessel's commander nominally parachuting out to safety or perhaps as a suicide mission.
 
Now, the later, scaled-down variant (Excalibur) has potential.
From a quick search looks as though it could still lift 60 tons worth of payload as opposed to Sea Dragon's 600 tons which as others have mentioned is possibly a bit of an overkill. How about if we got the military involved? If they got behind the idea of kinetic bombardment weapons and dusted down the plans for Project Thor that might give you a need for being able to lift large amounts - wikipedia says each cylinder weighed 8 tons. Allows you to tap both the Pentagon's ridiculous funding levels and possibly rope in DARPA to help with both initial development and possibly modifying it to reach higher orbits later.
 
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As has been said where would you get 500 tonnes to launch in one flight? For that matter would you want to risk all that hardware on one rocket? I do think there's a notion that the economies of scale you get with ocean going ships can be applied to rockets but unless hydrodynamic drag is a big issue in launches it just isn't so.
 
the Sea Dragon was design as NOVA class booster for Manned Mars Mission.
It had to launch 450 tons payload like Mission module, Fuel-tanks, engine module
there assembled in orbit to a Marsship, manned and launch.

As at NASA all project for 1970s manned Mars flight were cancel, the Sea Dragon was the first victim
i think with smaller "Sea Dragon" Saturn V or even Saturn IB class, they had be build
but there was the Siren called Space Shuttle...
 
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