However; If this could be made as a reliable TSTO craft that either could have both stages reusable, OR the first stage reusable and use the upper stage as a .5 stage, (Doing Dry-for-wet) as part of either a space station or as a part of a Mars Exploration Vessel, then I think that it would more than justify the cost.
Quote from: JasonAW3 on 12/20/2012 03:35 pm However; If this could be made as a reliable TSTO craft that either could have both stages reusable, OR the first stage reusable and use the upper stage as a .5 stage, (Doing Dry-for-wet) as part of either a space station or as a part of a Mars Exploration Vessel, then I think that it would more than justify the cost.No, it wouldn't. Reuseability negates the whole idea of Sea dragon. It is designed to be built cheap and robust, not for reuse. Also, return of huge stages is unthinkable
QuoteNote exactly See the "problem" is the amount of payload one of these things could lift. Short of a sudden "emergency" colonization program, need for a super asteroid/comet defense system or solar power satillite program the SD is simply too BIG to be viable. It has such a huge payload capabilty that you can't really justify a "viable" use for a single flight, let alone the multiples that the "program" would have required.It's an "issue" I wish we didn't have, but it is still the main issue with a SDLV type vehicle Not exactly sure I agree with you on this.
Note exactly See the "problem" is the amount of payload one of these things could lift. Short of a sudden "emergency" colonization program, need for a super asteroid/comet defense system or solar power satillite program the SD is simply too BIG to be viable. It has such a huge payload capabilty that you can't really justify a "viable" use for a single flight, let alone the multiples that the "program" would have required.It's an "issue" I wish we didn't have, but it is still the main issue with a SDLV type vehicle
Yes, the payload, currently, is excessive. However; If this could be made as a reliable TSTO craft that either could have both stages reusable, OR the first stage reusable and use the upper stage as a .5 stage, (Doing Dry-for-wet) as part of either a space station or as a part of a Mars Exploration Vessel, then I think that it would more than justify the cost.
Quote from: go4mars on 10/22/2012 08:47 pmSeveral people have mentioned their concern over developing a large rocket engine due to combustion instabilities. With modern software/analytical tools, is combustion instability still considered a practically insurmountable challenge for developing really big engines?It's not insurmountable, it's just extremely expensive. We know more than we knew during the days of the F1, but you're still looking at a very test-intensive program to get it right. Models of combustion stability have to take into account the coupled interactions of combustion kinetics, acoustics, and multi-phase fluid mechanics. Models of any one of these are happy to get within 10-20% of the real world values. Computational acoustics in particular is in its infancy.
Several people have mentioned their concern over developing a large rocket engine due to combustion instabilities. With modern software/analytical tools, is combustion instability still considered a practically insurmountable challenge for developing really big engines?
Geez, I just had a sick thought. What if you sacrificed about 30% of your total throw mass for both stages and added landing gear to the stages like on the Reusable Falcon 9? It COULD be recoverable then, still have a HUGE throw mass, and be reusable. But where the heck would you land such a monster? It'd be like trying to land a 25 story building for each stage!YEIKES!
Of course landing one on MARS could prove... Interesting. A ready, semi insulated structure that could be used dry for wet as a Mars COLONY, not just a Base. Save any reisidual O2 from the oxidizer tanks, scrub or otherwise neturalize the kerosene from the fule tanks, having already designed in hatchways into the tanks, go inset up gridwork floors and inflate habitat segments per floor, (For further insulation amd privacy) and you have a pretty good Mars colony to start.Jason
What if you sacrificed about 30% of your total throw mass for both stages and added landing gear to the stages like on the Reusable Falcon 9? It COULD be recoverable then, still have a HUGE throw mass, and be reusable. But where the heck would you land such a monster?
I vaguely remember some arguments that combustion instability becomes easier to solve at Sea Dragon engine sizes.Would love some references to back up that claim
<p>Sorry.</p><p> You must surround the entire living quarters with shielding that has the same effectiveness as five feet of water in a tank. This requirement should be used for all mass calculations for extremely long duration missions. Lighter elements are more effective per unit mass, so using liquid hydrogen gives the lightest shield. A thin layer of boron-10 would be needed as a neutron absorber. It is not possible to get away with less shielding, owing to the fact that the incoming cosmic rays have enough energy to create electron-positron pairs. These pairs are called secondary radiation, and they, too, must be stopped. However, these, in turn, create more electron-positron pairs until their energy drops below 1.1 MeV (the minimum energy needed to create an electron-positron pair) (At some point, each positron will annihilate an electron, producing two gamma rays). Because, for a given total energy of ionizing radiation, alpha radiation is more damaging than beta radiation which is more damaging than gamma rays, and lower frequency (longer wavelength) gammas are more damaging than shorter wavelength gammas, a thinner shield would actually be counterproductive, so far as cosmic rays are concerned. </p><p> </p>
My question is from a slightly different angle.It seems we have a history of building "right-sized" rockets, that then suffer weight increases and/or performance shortfalls, then we have to optimize the crap out of them to get the job done.Is a really big, dumb booster more expensive than all the effort expended on optimization & advanced materials?Is there harm in overkill? Granted, if we tried to build something with 30 F-1 engines, now we're hit with high engine expense, and duplicated complexity.
My question is from a slightly different angle.It seems we have a history of building "right-sized" rockets, that then suffer weight increases and/or performance shortfalls, then we have to optimize the crap out of them to get the job done.Is a really big, dumb booster more expensive than all the effort expended on optimization & advanced materials?
Is there harm in overkill? Granted, if we tried to build something with 30 F-1 engines, now we're hit with high engine expense, and duplicated complexity.
Matt, with 30 engines you run into SIGNIFICANT timing and fuel routing issues. (An example of this is the Soviet N-1 moon rocket).
There are also a couple of significant issues with the Sea Dragon design. (While I am infavor of this design, I am having to play Devil's advocate here for a minute). First, it is designed to be launched from the ocean with all shipping and air traffic to be cleared out for at least a five mile radius. (Not impossible, but difficult) Should the craft suffer a catostrophic failure during any part of the ascent, it would detonate with the force of a small nuclear weapon and scatter debris over a VERY large area. (The higher it got the larger the area)
Also, due to the Sea launch set up, it would rove a significant danger to sea life in the immediate vicinity. (Boiled shark soup with a side of broiled whale anyone?)
Fueling the first stage with Kerosene would be possible at shore, but should leaks develope, signifcant envionmental damage could occure.
The noise of such a launch would FAR exceed any OSHA standards and the shockwave over water is likely going to be able to travel a significant distance with little diminimishment.
Fueling the hydrogen for the second stage and the LOX for both First and Second stage would be very tricky using specialized cryogenics ships, similar to the current LNG tankers. Even with a dedicated Nuclear Reactor for fuel seperation from sea water and cryogenic cooling of both LOX and Hydrogen, we are talking a significant time to fully fuel such a craft, during which storms could develope endangering both the craft and the ocean vessels.
Assuming development of large plug nozzle systems for such craft, it MAY be possible to stretch the first stage and eliminate the second stage as plug nozzles tend to reconfigure their exhaust according to atmospheric pressure and do not require a specialized exhaust bell for low or zero pressure environments. This would also facilitate the recovery of such a craft for reuse, but it would again, endanger sea life where it landed.
However, even with these issues, I think that this is still a very viable launch system.
This guy briefly outlines some features of Sea Dragon (high level).