There's no question that SpaceX have found an excellent solution that promises to revolutionise launch prices. But I still see room for definite improvement beyond BFR. I'm quite sure there are ways to get LEO prices down to a third of BFR's promised levels, probably even lower - though not from a BDB solution
Some of the problems, -Material costs for the tanks, Sea dragon was meant to use 4" thick aluminium, which they didn't have a method for welding.
That, I'm going to hold close for a while Ross.
Evidently, Elon Musk has hinted that the cost per launch of the BFR could become as little as $7 million. That's $21.21 per pound to LEO. That number seems insanely optimistic to me, but if SpaceX can achieve anything close to that, we won't need a Sea Dragon or a Leviathan.https://www.nextbigfuture.com/2017/10/spacex-bfr-to-be-lower-cost-than-falcon-1-at-7-million-per-launch.html
The main problem I'd expect to see would be combustion instability -- conventional wisdom says that's a bigger problem in large chambers than small ones, and this is certainly a large chamber. This Q/A discusses that problem.However, the original Aerojet-General proposal suggests that the resonant frequencies of such a large chamber would be so low that feedback instability wouldn't be sustained: With regard to combustion stability, an analysis on the basis of sensitive time lag theory (perhaps the best theory so far developed) indicates that the Sea Dragon thrust chamber will operate well outside the region of combustion instability. One of the primary advantages of sea based development testing is that it permits early experimental evaluation of combustion stability on a full scale basis without an exorbitant outlay for facilities.In other words "we don't think it's a problem, but, hey, at least if one of those engines blows up in the ocean it won't hurt anything."
Truax wasn't concerned with combustion stability because the engine was going to be a pintle injector type. He believed the natural combustion stability of the pintle injector would allow enormous engines to be highly stable at a variety of pressures. (Variable pressure was a key part of his design, because it allowed a much simpler and sloppier system in which pressure started high and slowly dwindled down as the tanks emptied.)TRW (who built the rockets for the Apollo lander) later validated his belief. In that paper they point out that pintle injectors have demonstrated stable combustion with motors varying in scale by 50,000:1. So, Truax was probably right.
I wonder how much it would cost to build and test a one-third scale Sea Dragon engine prototype. If nothing else, you'd get a nice big explosion out of it.
how would the sea dragon launching impact the marine life around it? and if it does impact the marine life in a negative way, how can we fix or mitigate that?
Launch it from some dead water body, such as a salt lake or a heavily poluted lake. Does anyone know of suitable candidates?