Rosatom has at least some money
So actually as far as "not having money" in this particular case all bets are off.
Russia, the US and other nations are to discuss cooperation on building a nuclear-powered spacecraft, according to the head of Roscosmos – the Russian space agency. Anatoly Perminov, Roscosmos chief, tells state-owned newswire RIA Novosti that nuclear spacecraft plans are to be discussed with NASA on April 15. Perminov added …
the SALT treaties* banned nuclear power in space?
I'd love to see it - let's move heavy industry off Earth and beautify it, isn't this what greens want as well? Nuclear power + space travel + nanotechnology could = a glorious future.
I'd move to an asteroid in a second. Presuming there was a good school for the kids and broadband of course.
* or some anti-proliferation treaty anyway.
As long as you waited to fire up the reactor when it's safely in space, there is very little problem launching a reactor, as it will pretty much only contain relatively benign weakly radioactive Uranium (They're sending up worse stuff in RTGs) there are no fission products or minor actinides.
Re-entry of radioactive material might be more of an issue - depends how it scatters, the other issue being possible production of nukes in space - But in the main it's a PR thing
I was talking to an astronomer and a solar-system-specialist physicist a while back about a proposed spacecraft that would be sent out to edge of the solar system. Most of the conversation was about the limitations imposed by spacecraft's power budget.
I asked why they could not just bolt a, say, 50MW nuclear reactor onto the side of the space craft and have lots of power. They told me that at this time the regulatory frameworks in effect in the USA and internationally have made it such that it is very difficult for new spacecraft to be equipped with even nuclear-thermo power. Mainly because production of the radio-isotopes used in thermo generators is very tightly controlled, and there is not a lot in stock.
IMHO this is silly. If there was ever a good place to stick a nuclear reactor it is far away from here, in outer space.
Else in Lewis Page's basement bwahahaha!
What's all this surplus heat about? Is this going to be steam engines in space?
Has there been no progress in converting nuclear radiation directly into electricity? (Something I remember reading about as a child in the '50s - "Atomic Batteries")
Or what about direct use of (ionising) radiation to power the ion drive?
(Yeah, yeah, I'm well aware that there will still be surplus heat, but just using nuclear energy to boil water seems pretty low tech and dangerous to me.)
I don't know where the bizarre idea "boils stuff, thus must be primitive" comes from.
The dumbfuck who came up with "nuclear power is an exceedingly expensive way to heat water" probably wouldn't have been able to help James Watt use a wrench. So there.
There are not a whole lot of methods to get motive power out of a temperature differential.
"Or what about direct use of (ionising) radiation to power the ion drive?"
because you'd need phenomentally intense radiation - almost all of which would be wasted if you were irradiating a gas/plasma fuel.
Oh, and neutrons aren't much good for that - you'd need a beta or gamma source.
"but just using nuclear energy to boil water seems pretty low tech and dangerous to me"
well, you could use something like a Brayton cycle - with nitrogen or helium as a working fluid, but that takes very high termperatures, and for decent efficiency you still need a steam cycle on the back end. And you're still rejecting a very large proportion of the heat.
Or you could try thermocouples, but they produce 2/10ths of f-all power.
If tis is what I think it's likely to be - a NERVA type design, it's a simpler beast. It's just a heat source which boils and then heats fuel/coolant through the reactor core and spits it out of the back end. They've got much higher specific impulse figures than normal chemical rockets, not least because there's no need for heavy oxidiser.
As an aside, making power from anything in space is a bugger of a problem - finding a way to reject heat is a problem. You need a BIG radiating surface.....
That's what radioisotope thermoelectric generator (RTG) do, the nuclear decay is the hot side of a thermopile, the cold side is a radiator into space and it's how all the deep-space satellites are powered.
There's also Stirling radioisotope generator (SRG), but getting the piston seals to work in the cold and vacuum of space is an engineering challenge.
"Has there been no progress in converting nuclear radiation directly into electricity? (Something I remember reading about as a child in the '50s - "Atomic Batteries")"
This is *probably* another name for what are called Radioisotope Thermoelectric Generators which various US probes to the outer planets have carried. they are the RTG's protesters protest about and are chunks of usually Pu268 (The former Soviet union liked Po as well) heating the hot side of thermoelectric junctions.
Power levels are 500W and no actual control. Also there efficiency is IIRC about the 10% mark.
The more SF kind of device (which the Russian TOPAZ reactors use) is the "Thermionic" converter.
Normal electronic valves use a heater coil to trigger electron emission. Thermionic converters use reactor heat *directly* to trigger electron emission IE a current flow.
Again with limited efficiency but IIRC better than the straight thermoelectric junctions and AFAIK without the limits of a Carnot cycle (In *principle* the Cathode and Anode can be the same temperature. IN the thermoelectric system theis would produce no electricity at all).
"Or what about direct use of (ionising) radiation to power the ion drive?"
Does sound a good idea but I doubt anyone has actually *tried* it.
AFAIK the nearest that has been done is the use of reactor neutrons to drive a laser (not quite the same thing
"(Yeah, yeah, I'm well aware that there will still be surplus heat, but just using nuclear energy to boil water seems pretty low tech and dangerous to me.)"
It's pretty well understood and it delivers a *lot* of power.
People have seen so much nuclear disaster hype that they just ignore it and get on with their lives. Today is an excellent day to step up plans for reactors, reprocessing and proper waste storage facilities as almost everyone will not care. Time to build thunderbird 3.
Orion - the nuclear pulse rocket tech - was pretty much killed off by SALT, but the main issue they had was the calculations of the engineers that an earth based take-off would release enough additional radioactivity into the environment to account for something like 10 deaths (IIRC) any deaths were unacceptable to the designers.
If you could buildin space with conventional chemical rockets and launch fom there, that would be a good solution.
(sigh) it takes an electrical engineer to point out the main problem with a nuclear-thermal-electric generator in space.
These things only work when there is a temperature differential between the reactor output and the ambient environment. As well as heating up the circulating fluid you have to cool it down again. Otherwise you can't extract power from it. Earth-based reactors use cooling towers or river or seawater to get that extra few degrees needed to raise their thermodynamic efficiency.
A solution, currently use already as cold end of thermal nuclear interstellar devises, is to have a nice big heat-sink on the shadow side of the craft.
A shielded from the sun area of inter-planetary space is really cold indeed ( nights on the moon get about -180 Celsius degrees ).
Of course, the wasted heat energy damped will only scape by radiative meanings, due the lack of air, but still it will work.
"These things only work when there is a temperature differential between the reactor output and the ambient environment. As well as heating up the circulating fluid you have to cool it down again. Otherwise you can't extract power from it."
Err you might like to notice that *actual* pictures show a *very* large structure attached to the relatively small reactor core.
It's called a radiator. IRL its design is a *substantial* part of *any* space nuclear system.
Booster rockets fail every year even for well funded and experienced spacefaring nations like the US and Russia. The chance of a launch accident is like 0.3% for the supposedly ultra-reliable manned missions using the shuttle, and 0.1% for the proposed Ares boosters. These numbers are far worse than failure rates for ground-based reactors that would expose the fuel to the environment. It is entirely reasonable that we account for these risks when deciding to launch radioactive material into space.
As I remember, RTG's have to be designed to withstand reentry without breaking up, though there is of course no way to guarantee that they can withstand the most spectacular failure modes of chemical rocket boosters. Any boost of serious amounts of reactor fuel will absolutely need to account for the possibility of booster failure.
Still, once out of the atmosphere, I can't think of a safer place for nuclear power than the cold vacuum of space. Nothing to pollute, very limited numbers of people to irradiate.
The way it was explained to me, at the start of their lives - before they are used to generate power - the contents of a fission reactor are fairly benign. It's only during their active life, as the nucleii split into nasty fission products and irradiate the moderator and everything around them with neutrons that they become a hazard.
We know this as the half-life of uranium is in the hundreds of millions of years. So it takes an awfully long time for it to decay. It's only when we poke it with neutrons that start the fission process that more active isotopes are produced.
The thing about RTGs is they they are different. The "fuel" in them decays rapidly and the heat it produces during this decay is used to create electricity, directly. That means the fuel must be much more radioactive - and significantly, that it can't be turned on and off - if it goes *splash* then there is a lot of nasty stuff released. Typically RTGs are powered by Plutonium (not nice) or Strontium (even less nice, as it can displace Calcium in peoples' bones and therefore stays in the body until the person dies).
So, while there is a strong case to be made for not putting RTGs in rattly old rockets, since they are "live" during the launch, the same argument does not hold for reactors, as these can be activated once they get far away from earth - and more importantly once they are on a trajectory that won't bring them back again.
The use of reaction mass for space propulsion, whether nuclear or chemical, is about as primitive as can be. Not to mention slow, dangerous and frustratingly expensive. Sure, the blue glow of spaceship exhaust in space movies may look cool. But rest assured that humanity is not going to colonize the solar system with mass-ejecting rockets based on Newtonian physics, let alone the star systems beyond. Unless there is some sort of breakthrough in our understanding of motion at the fundamental level, there will be no mass migration off the earth any time soon.
The truth is that we will not come out of the current dark age of space travel until and unless physicists pull their collective head out of the sand and realize that they do not really understand motion, even if they think they do. A new analysis of the causality of motion reveals that Aristotle was right to insist that motion is caused and that, as a result, we are immersed in an immense lattice of energetic particles without which there can be no motion. Soon, we'll learn how to exploit the lattice for clean energy production and extremely fast propulsion. New York to Beijing in minutes, earth to Mars in hours; that's the future of transportation. Imagine vehicles that can move at prodigious speeds and negotiate right angle turns without slowing down and without suffering any damage due to to inertial effects. It will happen in your lifetimes.
Google "Physics: The Problem with Motion" if you're interested in the amazing future of travel.
Opening up Sutton 4th Ed to page 518 you'll find its target design was a T/w of 5.3:1 (75000lb thrust, 14000lb weight). with a fairly modest 450psi chamber pressure but a fairly hefty 100:1 expansion ratio nozzle.
The lowish chamber pressure + high expansion ratio nozzle and *very* poor (by normal rocket standards) T/W confirm this is something for use in Earth orbit at least.
Peak power during the NERVA test runs was 4200MW (4.2GW) in a ground test.
Compare this with the 5Kw(e) of a TOPAZ system.
While people *have* built GW nuclear power systems they are *only* to heat and eject Hydrogen out of a nozzle.
Do you think there was a reason the designers went this way?
The engineering of a nuclear thermal system (especially in the materials) is tough but *conceptually* it's know (from Earth power plants) that it works.
The alternatives are an ion derive about 1000x bigger than *anything* seen anywhere (yes that *is* quite a big scale up in 1 jump) or clustering *lots* of current sized devices.Plume interaction between devices *is* an issue (I think DS1 did some work on this). Putting *lots* of them in close proximity is likely to make things "challenging".
LIkewise the nearest anyone has come to a space nuclear power system IIRC was in the 100Kw class using either a Na/K metal vapor or an inert gas mix to drive a turbo-generator (check NASA for space Brayton and mini-brayton (MBU systems). The ones that got to (ground) test status were IIRC in the 10-15Kw range.
No one has got near a live trial of a magnetohydrodynamic (MHD) direct conversion hot metal vapor -> power system. Possibly the holy grail of this sort of app. No bearings, no turbines and (in principle) no failure mechanism.
Big (MW) space nuclear electric is well *beyond* state of the art.
Big nuclear thermal (Isp c 850) is *within* the state of the art.
Just something to think about.
I happened to be thinking about this earlier today - the Liquid Fluoride Thorium Reactor technology might be a great candidate for this application. Among other things it has the great advantage of the ability to alter the heat output almost instantly - we have seen in recent days the great disadvantage of solid fuel reactors, the fact that they can not be just 'turned off'. An LFTR can be literally turned off - the original one at Oak Ridge was normally turned off every night when the researchers went home! As a liquid-based system, the flow rate can be adjusted constantly to provide the desired amount of heat and power, which would greatly simplify the management of thrust.
Also the LFTR does not require a pressure vessel, so it would greatly reduce the required mass, for better efficiency.
LFTRs also have minimal radioactive waste (so much less risk of radioactive pollution in the event of an accident or hostile action), and do not generate large amounts of weapons material that might be stolen and used for evil purposes.
You might like to try getting your hands on a little book called "Thrust into space." It discusses the energy requirements for various missions and (can't remember if it says so specifically) the molten salt reactors for the nuclear aircraft programme were the proposed solution to this.
Note the nuclear aircraft (and project Pluto, the nuclear ramjet at Los Alamos) use ambient air as the working fluid. NERVA would have heated the 20k LH2 through its outlet nozzle to heat up but I'm not it would have gotten as far as 0c before hitting the 2000+c core.
One of NASA's side projects was an electrically heated Hydrogen thruster.
They appear to have built the world's largest incandescent light bulb filament at 30Kw.
The design gave 1lb of thrust but at an ISP of c500sec (The smallest thrusters on the Shuttle are 25Lb with an ISP of 215secs).
Obviously a scale up would be needed but if you have MW sized power generation this should be fairly straight forward.
Tapping some hot H2 off the core of a nuclear thermal system would be a bit more problematical. The smart money would carry LO2 and keep the propellant system unified with the option to refuel at Mars from in situ resources (AFAIK no one has looked at in situ mfg of storable propellants or oxidisers and NTO and the MMH/UDMH groups are all *nasty* to handle).
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