For hard scifi buffs, check out Stephen Baxter's space-program-alt-hist novel Voyage, where (among other things) NERVA is revived for a manned Mars shot.
I'm kinda surprised to see this; I thought that public acceptance of nuclear-related programs would be at a low, after Fukushima. Heck, I remember when people were kicking up a fuss over Cassini's RTG back in 1997.
All I ever heard before was Project Orion, but after reading about Project Rover, I don't understand why you would want Orion's design. Isn't Rover superior in every way? It appears to me that Orion uses a much smaller fraction of the released nuclear energy, leading to a bigger waste of resources and smaller payload to total weight ratio. Furthermore it's harder to use Rover as a weapon, but maybe this would be a minus for some of the potential investors.
Well, Project Orion was certainly more dramatic -- detonating hundreds of nukes to punch a rocket up into space. It was also top-secret at the time; that explains its mystique.
As far as being a superior choice, I don't think it's quite apples to apples. Project Orion (nuclear pulse propulsion) was designed to get very large payloads directly into orbit. Nuclear thermal rockets like NERVA were apparently designed to be used as drop-in replacements for upper stages on conventional chemical rockets, or as space "tugs" in orbit. That might imply that it was difficult to design a nuclear thermal rocket which would deliver the high initial thrust(?) necessary to lift a payload directly out of our gravity well (but IANA rocket scientist, so I may be mistaken on this). That said, a small blurb on Wikipedia does mention that "Robert Bussard proposed the Single-Stage-To-Orbit "Aspen" vehicle using a nuclear thermal rocket for propulsion and liquid hydrogen propellant[...]" -- so maybe it would indeed have been a superior design choice in the end.
Orion-type designs are less efficient than nuclear thermal, but have orders of magnitude more energy to work with. Nuclear bombs are pretty unbeatable for raw power.
Thanks for the infos, it makes a bit more sense to me now. I'm still trying to understand as a layman with engineering background, so I'm pulling a few numbers out of my ass now..
Let's say we have a unit power output of P_therm and P_bomb (in case of the bomb its time plot should look close to dirac pulses while P_thermal should look like a flat line), we have efficiencies eps_therm, eps_bomb and we have the mass of the propellant systems m_ohterm, m_ohbomb.
I'm assuming
P_thermal to be 1e+7W (1/100 of a powerplant),
P_bomb = 0.15 kiloton per second ~= 6e+11W => lets make that 1e+12.
Efficiency: eps_therm = 1'000 * eps_bomb
Mass: m_therm = 10 * m_bomb
so if these numbers work out the bombs give you about 10^5 times the power output of the furnace, deliver 10x the power to the ship (efficiency differences) and yield about 100x the effect per unit of mass.
hmmmm... I think I'm starting to get it ;). However here's the thing: I'm imagining that the furnaces can be scaled up much easier than the orion design. You can just make them bigger up to a certain point and when that doesn't help anymore you can strap them together. You can't really strap together the orion propellers because it would become incredibly susceptible to timing (one bomb goes off 1ms earlier and you end up spiraling everyone to death with 20G acceleration or so :D ).
As I recall, Orion-style craft scales up well. Ahh, the Wikipedia article says "physicist Ted Taylor showed that with the right designs for explosives, the amount of fissionables used on launch was close to constant for every size of Orion from 2,000 tons to 8,000,000 tons." The original design team worked on 4,000 and 10,000 ton vehicles and the "Super" was an 8 million ton interstellar vehicle.
The timing isn't so critical. It could handle a 10ms timing variation, and a misfire.
George Dyson's book, Project Orion, is well written. That being the son of Freeman Dyson, who worked on the project.
Key words: bumpy ride. The G-forces exerted by such a launch would turn human passengers into pulp. Freight only! http://en.wikipedia.org/wiki/Space_gun
They aren't really comparable, you'd use each for different purposes. An NTR is an incremental design, you can use it in a more or less conventional rocket design, with massive improvements in payload and/or delta V capability.
Nuclear pulse propulsion is something different entirely. It has vastly higher exhaust velocity and vastly more thrust but has very different design requirements than NTRs. With it you could put enormous payloads into orbit (think battleships and aircraft carriers) if you were ok with the fallout, or you could intercept dangerous asteroids or comets with very short warning times, or you could launch payloads to neighboring stars at truly enormous speeds.
The part of this that surprised me is that the amount of radioactive fission products in the reactor is fairly insignificant for the first part of a mission -- a nuclear thermal rocket can be well out of Earth's orbit before it's as radioactive as the RTG that powers the Curiosity rover.
Honestly the best way to handle that would probably be to simply not mention it.
If directly asked about it, just start spewing jargon at them until they get bored and walk away. Just don't give them something that would make a good soundbite.
That sounds like it would backfire horribly. Honestly, it's a lose-lose situation. If you didn't mention it, they'd spin it as some sort of cover-up; if you spewed jargon at them, they'd just take whatever snippet sounded good to them and spin it into something unrecognizable that fits their agenda. Journalists never let truth get in the way of a good story.
You would need to pick your jargon carefully. The words that tend to set people off are pretty particular. Just avoid words like "radioactive", "isotope", any element name, "nuclear", etc. Don't call it a "reactor", call it a "thermal generator". Be honest and open about everything, but don't brag about it on twitter or in press releases.
The idea is to act like it is nothing special to give off the impression that it is nothing special. Make it all seem very routine and boring. Hyping actually boring aspects of the mission could also help. Do lots of things like making twitter accounts for rocks: https://twitter.com/N165Mars
Well, just look at the kerfuffle over the Cassini RTG back in 1997:
Reporter: "Could this probe fail on launch, re-enter the atmosphere, and explode, showering the U.S. with radioactive particles?"
Scientist: "Yes, but there's a one-in-a-million chance of that happening, and we have safeguards against that..."
Headline: "SPACE PROBE COULD EXPLODE AND SHOWER RADIATION EVERYWHERE!"
The key here is the "Yes, but..." -- if a reporter wants a sensational story, they'll find a way to get it, even if they have to play fast and loose with the truth to do it.
(Thanks for that Twitter account link -- I love NASA's sense of humor.)
Yeah, they really botched Cassini. However with the experiance they gained from that, and a healthy awareness that PR issues like that can happen in the first place, I think they could overcome any issues they might run into. The answer they gave was correct, and they were correct to not be concerned. They know RTGs are safe, but they forgot that the public doesn't know that.
I'm not sure I'd call plutonium metal "not that dangerous" - it is pretty toxic, can catch fire spontaneously and once if does catch fire you have to be really careful trying to put the fire out. There is an excellent book on the history of the Rocky Flats nuclear weapons plant near Denver that describes some of the problems with handling plutonium on an industrial scale:
Edit: Of course these things are relative. I guess compared to chemicals like chlorine trifluoride or FOOF it is pretty tame from a chemical perspective:
Well yes. What I meant to say was that in trace amounts in the atmosphere Plutonium isn't terribly dangerous. When you're working with bulk metal there are heavy metal toxicity and radioactivity concerns, of course, and if you're working with powder or fines then that can be particularly dangerous in terms of radioactivity exposure (because Plutonium in your lungs is pretty much where it can do the most damage).
But compared to fission byproducts like I-131 or Sr-90 which are both crazy radioactive and eagerly taken up by your body and placed into your bones and your thyroid, Plutonium barely registers.
Very smart to link nuclear thermal technology to manned Mars missions. It would be wonderful if public enthusiasm after Curiosity makes further development in this area possible.
Nuclear propulsion will open vast horizons to the future of mankind. I think the best option will be fusion-powered plasma turbines. http://youtu.be/ro5-QYqqxzM
I was going to say it looks like a Bussard IEC (Inertial Electrostatic Containment) with a VASIMR (Variable Specific Impulse Magnetoplasma Rocket) tacked on the back, but there's a dozen things about the IEC that they're talking that seem different, and they spent little enough time detailing the thruster that comparisons v.s. VASIMR are a little tricky.
There are a lot of key differences. Bussard IEC can be characterized by recirculation of electrons, virtual cathode, "wiffleball" magnetic compression. VASIMR can be characterized by helicon antenna, single phase instead of multiphase.
Project Rover: http://en.wikipedia.org/wiki/Project_Rover
For hard scifi buffs, check out Stephen Baxter's space-program-alt-hist novel Voyage, where (among other things) NERVA is revived for a manned Mars shot.
I'm kinda surprised to see this; I thought that public acceptance of nuclear-related programs would be at a low, after Fukushima. Heck, I remember when people were kicking up a fuss over Cassini's RTG back in 1997.
Are we going to revive Project Orion next? http://en.wikipedia.org/wiki/Project_Orion_%28nuclear_propul...