This will be available in ten years
Nuclear is attractive, but it is not automatically the most efficient option. In addition to the many reasons you don't want to use it as a launch engine (political and public concerns as well as abysmal T/W ratio), there are significant instances where biprop chemical rockets would outperform. Let's consider a fast transit to Mars packing 4 km/s out of LEO. Since we will assume that you don't want to land on the nuke, we'll make an apples to apples comparison and talk about getting into a nominal low Martian orbit. A vehicle like Starship can aggressively aerocapture at Mars and then aerobrake in multiple passes to the desired orbit. A nuclear rocket, on the other hand, cannot. Keeping the nuke well away from your crew during burns will require some sort of long truss or heavy shielding or other superstructure that will weigh as much or more as the heat shield and control surfaces on Starship but not permit any aggressive aerocapture. So while Starship enters Martian orbit for free, a nuke must carry 1.1 km/s in additional dV to brake propulsively. Any subsequent aerobraking will be much less aggressive and take much longer than for Starship, so it actually takes more time. If you want to circularize propulsively as well, rather than spend a week aerobraking, that jumps to 2.7 km/s. Additionally, the dry mass penalty is substantial -- I will say 20% m1 mass growth to account for both the greater tankage volume and the heavier engine. So even if lifting liquid hydrogen into LEO is no more costly than lifting methalox (it's much more expensive, both in the context of actual price and with respect to the bulk density issues), the nuke will have to be to be pushing a specific impulse of 780 seconds just to break even. And that's without additional considerations like the cost of getting the nuke into orbit, the cost of the nuke itself, the operating lifespan, the need to service the engine and reprocess the fuel, the extra descent/ascent infrastructure you need at Mars.It is more efficient for the moon, of course, where propulsive braking is non-negotiable. Even here, however, the descent-ascent infrastructure needs to be considered.Where nukes become game-changing is if you end up with LH2 production capacity on the moon AND regular shuttle/tug flights between the moon and other destinations.
Nuclear Thermal does not require liquid Hydrogen
Quote from: ZChris13 on 09/26/2019 06:14 pmNuclear Thermal does not require liquid HydrogenNTR without hydrogen as the propellant has so bad isp that it makes practically no sense at all.And NTR with gaseous hydrogen - then the tank mass will be insane.
SpaceX is working on nuclear propulsion since at least 2016. Tom Mueller involvement currently is related to nuclear propulsion.
Using a high-performance low-density propellant is not the answer. So we’ve gotten everything we’re going to get out of chemical propellants.So we’re looking, actually, at like electric propulsion for the satellites, and we’re talking to people about nuclear-thermal, you know, the NASA centers are working on nuclear; it’s just prohibitively expensive to test because you can’t; it’s not like the 60s, like when you can just let fission products fly out of your rocket into the desert. You’ve now got to scrub it and clean it and capture it, which is super-expensive. I don’t think SpaceX could really afford to develop that rocket ourselves. If NASA ever gets turned on to develop those test stands, we’d probably want to jump in on that. You can just about double the performance of a rocket to Mars compared to a really-good, like a Raptor system, a chemical system, with fission; nuclear fission. Theoretically, fusion may be ten times better, and antimatter maybe a thousand times better, but I think those are certainly not going to happen in my lifetime. Maybe in your lifetimes.The warp drive is still a long way away. <laughter> So we’re stuck with chemical propellant for quite a while.
1/Starship to reach any part of solar system need nuclear power plant2/Nuclear rocket engine give more delta V for available fuel.3/New nuclear engine could be very low trust engine, using just for everything with exception of landing and launching from planets.(Hydrogen could be produce from methane by steam reforming)4/Power plant could be used also for producing electricity, replacing solars in distances beyond Mars5/Cooling of power plant could be done using skin of rocket, that is design to accept and radiate heat during landing6/Power plant will be turn off during launch and landing, to cool down for landing heat wave
Nuclear engines will never get off the ground at least for leaving the Earth's surface due to radiation issues until SpaceX or someone else devs. an engine powered by nuclear fusion which will be likely at least several decades away. Will need to go beyond chemical propulsion for interstellar travel.
Or they could go with nuclear pulse propulsion Orion style. That would just involve Elon controlling more nuclear weapons in orbit than the Russians and the US have total combined. It would certainly move him up a bit in the Forbes Most Powerful People ranking. He’s already ahead of Kim Jong Un and Netanyahu. https://www.forbes.com/powerful-people/list/#tab:overall
but then mine Uranium on Mars (if possible) and thus be free to build empty reactors on Earth, and power ships (some immense) across the solar system and beyond, whilst not polluting Earth(Disclosure: I'm generally against nuclear fission power on Earth due to safety, and cost and clean alternatives.)
Quote from: Ludus on 09/26/2019 07:58 pmOr they could go with nuclear pulse propulsion Orion style. That would just involve Elon controlling more nuclear weapons in orbit than the Russians and the US have total combined. It would certainly move him up a bit in the Forbes Most Powerful People ranking. He’s already ahead of Kim Jong Un and Netanyahu. https://www.forbes.com/powerful-people/list/#tab:overallSee my essay above it is much, much TL:DR (MMTL:DDR) Definately dont read!https://forum.nasaspaceflight.com/index.php?topic=49104.msg1996932#msg1996932 IMO: So Elon is taking on several "world changing" technologies. Especially ones that are heavily bogged down in paperwork.If Elon looks ahead to a need for Nuclear, he may "take on" development of that industry. Doing this on earth would be expensive. I suggest he might start on earth working with NASA etc, but then mine Uranium on Mars (if possible) and thus be free to build empty reactors on Earth, and power ships (some immense) across the solar system and beyond, whilst not polluting Earth or needing Earth based regulatory compliance. (apart from crew safety)These ships would never land on Earth, and many would never land. (shuttles would dock etc)We will shortly see SpaceX start some small cooperation with NASA - toe-in-the-water stuff.And as for power... SpaceX (&Elon) would be THE absolute experts and suppliers of Atomic space propulsion technologies. This would include fusion, and antimatter, in time. The best experts would go to SpaceX to see their discoveries bear fruit!(Disclosure: I'm generally against nuclear fission power on Earth due to safety, and cost and clean alternatives.)
Quote from: DistantTemple on 09/26/2019 09:08 pmbut then mine Uranium on Mars (if possible) and thus be free to build empty reactors on Earth, and power ships (some immense) across the solar system and beyond, whilst not polluting Earth(Disclosure: I'm generally against nuclear fission power on Earth due to safety, and cost and clean alternatives.)Why the concern about Earth-sourced nuclear fuel?Leaving aside the Earth-regulatory issues, uranium-fuel pellets are relatively safe AIUI. Mining and enriching uranium off-Earth seems a strange trade. That part of the cycle isn't really dirty is it?
snip...Looking at the list of industries Elon tackled: Banking&Payments, Automobile manufacturing, Orbital Rockets, Global Telecommunications, Tunneling & urban infrastructure, Brain surgery & Medical Devices, it doesn’t show much fear of complex bureaucracy and regulation. It seems plausible to me that if he judges Nuclear to be a critical technology that’s not advancing fast enough he might put it on the list and try unusual approaches as you suggest. I don’t think nuclear has any real technical problems on earth but it might have intractable political perception problems that make exotic approaches necessary.
Environmentally fairly clean. Regulatory and politically extremely dirty.
