Re: The "Real Aerospace" Thread
Posted: Mon Apr 01, 2019 7:06 pm
So, I've just had a reeeeally crazy idea I've been mulling over for about two weeks, and I'd like to pass it by here.
Firstly, I started from the concept of the Nuclear Thermal Turbo rocket, an idea for a Air Augmented Nuclear Thermal Rocket, that uses air-breathing propulsion to lofts itself out of the lower atmosphere, transitioning from a ramjet type of system (powered by a turbofan spun by gasses leached from the reactor chamber), then to a scramjet (using the air directly by heating, and leaving the fanblades at idle angles of attack), then finally using standard NTR-type propulsion for the final ascent and orbital circularisation.
More on the ideea (and it's creator, John Bucknell) here:
https://forum.nasaspaceflight.com/index ... c=43344.20
http://www.projectrho.com/public_html/r ... rmal_Turbo
The kicker is the quite phenomenal promised (and I do stress "promised") mass fractions, that can be seen in the tables presented. This is due to the high average Isp of the thing (as air-breathing systems have Isp's in the thousands generally).
I thought, "great, but that pure rocket Isp is killing me. Looks so weak compared to the rest". So I started digging for more experimental types of NTR's. I stumbled onto MITEE, which uses a hybrid power system to dissociate some of the hydrogen into it's monoatomic state, thus achieving Isp of about 1350. There was also the NTER, the european concept that used hot gasses to drive what is essentially an electrothermal thruster.
But... then I realised that, since I already have a nuclear reactor onboard, how about going even more speculative...and mate it to this:
http://www.projectrho.com/public_html/r ... d-core_NTR
If it works (think I said that about half a dozen times) then I could literally get to Titan with an SSTO. And back (with the payload fractions in LEO plus a specific impulse of about 17,000 sec from the pulsed regime).
Finally, since I've got copious amounts of power onboard, why not use a more... exotic system to aerobrake for the return trip? Like the magshell:
https://forum.nasaspaceflight.com/index ... c=29912.80
https://selenianboondocks.com/2010/02/m ... rocapture/
There are MONSTROUS issues with the above concept:
1) making the turbo-fan airbreathing mode work (supersonic ducted fans are not really a thing).
2) transitioning between modes
3) getting rid of the excess heat from the pulsed NTR mode (radiators aplenty).
My initial vehicle would be almost entirely fuel, but that can be aleviated if one uses ISRU (pump the atmosphere of wherever it is you be landing into your tanks; NTR's don't care much what they propell out the nozzle as long as it doesn't gum up the works; water vapour, methane, ammonia, H2 produced by electrolisys and cracking, etc) and magnetoshell aerobraking.
Or you can split the mission, and use a Starship-esque upper stage that has the pulsed unit, along with a simpler airbreathing mode and a pumping station.
Monstrously complex, but, as you might know, I like thinking ludicrous...
Another, simpler mission, is to use a molten salt thorium reactor to melt my way into Europa. The thorium would produce U233, which fissions and gives off neutrons... but also U232, which fissions into Th (Thallium) 228, which is a HARD gamma emitter (at 2.67 Mev, it's the third most potent one known). The reactor and the submersible that follows it down would be bathed in hard gamma, thus resolving the issue of how to sterilise the craft (the most complicated problem in this type of Europa mission). the reactor would be fueled so that it's no longer critical by the time it finishes melting, and just plunks into the abyss. The submersible could have it's own, separate, reactor or RTG to do long duration surveys (and would transmit data to the lander on the surface by optical cable). Before landing, the craft could use high-power ground penetrating radar (remember, plenty of power available) to map the ice, and determine ideal landing spots (not too thin, or the reactor will continue to be critical as it finishes melting, and kill whatever is in the general vicinity of it's landing spot when it hits the bottom).
Firstly, I started from the concept of the Nuclear Thermal Turbo rocket, an idea for a Air Augmented Nuclear Thermal Rocket, that uses air-breathing propulsion to lofts itself out of the lower atmosphere, transitioning from a ramjet type of system (powered by a turbofan spun by gasses leached from the reactor chamber), then to a scramjet (using the air directly by heating, and leaving the fanblades at idle angles of attack), then finally using standard NTR-type propulsion for the final ascent and orbital circularisation.
More on the ideea (and it's creator, John Bucknell) here:
https://forum.nasaspaceflight.com/index ... c=43344.20
http://www.projectrho.com/public_html/r ... rmal_Turbo
The kicker is the quite phenomenal promised (and I do stress "promised") mass fractions, that can be seen in the tables presented. This is due to the high average Isp of the thing (as air-breathing systems have Isp's in the thousands generally).
I thought, "great, but that pure rocket Isp is killing me. Looks so weak compared to the rest". So I started digging for more experimental types of NTR's. I stumbled onto MITEE, which uses a hybrid power system to dissociate some of the hydrogen into it's monoatomic state, thus achieving Isp of about 1350. There was also the NTER, the european concept that used hot gasses to drive what is essentially an electrothermal thruster.
But... then I realised that, since I already have a nuclear reactor onboard, how about going even more speculative...and mate it to this:
http://www.projectrho.com/public_html/r ... d-core_NTR
If it works (think I said that about half a dozen times) then I could literally get to Titan with an SSTO. And back (with the payload fractions in LEO plus a specific impulse of about 17,000 sec from the pulsed regime).
Finally, since I've got copious amounts of power onboard, why not use a more... exotic system to aerobrake for the return trip? Like the magshell:
https://forum.nasaspaceflight.com/index ... c=29912.80
https://selenianboondocks.com/2010/02/m ... rocapture/
There are MONSTROUS issues with the above concept:
1) making the turbo-fan airbreathing mode work (supersonic ducted fans are not really a thing).
2) transitioning between modes
3) getting rid of the excess heat from the pulsed NTR mode (radiators aplenty).
My initial vehicle would be almost entirely fuel, but that can be aleviated if one uses ISRU (pump the atmosphere of wherever it is you be landing into your tanks; NTR's don't care much what they propell out the nozzle as long as it doesn't gum up the works; water vapour, methane, ammonia, H2 produced by electrolisys and cracking, etc) and magnetoshell aerobraking.
Or you can split the mission, and use a Starship-esque upper stage that has the pulsed unit, along with a simpler airbreathing mode and a pumping station.
Monstrously complex, but, as you might know, I like thinking ludicrous...
Another, simpler mission, is to use a molten salt thorium reactor to melt my way into Europa. The thorium would produce U233, which fissions and gives off neutrons... but also U232, which fissions into Th (Thallium) 228, which is a HARD gamma emitter (at 2.67 Mev, it's the third most potent one known). The reactor and the submersible that follows it down would be bathed in hard gamma, thus resolving the issue of how to sterilise the craft (the most complicated problem in this type of Europa mission). the reactor would be fueled so that it's no longer critical by the time it finishes melting, and just plunks into the abyss. The submersible could have it's own, separate, reactor or RTG to do long duration surveys (and would transmit data to the lander on the surface by optical cable). Before landing, the craft could use high-power ground penetrating radar (remember, plenty of power available) to map the ice, and determine ideal landing spots (not too thin, or the reactor will continue to be critical as it finishes melting, and kill whatever is in the general vicinity of it's landing spot when it hits the bottom).