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Russia: Nuclear Powered Spacecraft

 
 
farmerman
 
  1  
Reply Wed 20 Jan, 2010 07:23 pm
@BillRM,
Ion propulsion will be one of the possible means to achieve intergalactic travel. The ideas is that the acceleration is very slow and the ultimaet velocity is high after several years of acceleration using an ion prop engine that is based upon ionizing a salt or a metal by gravity capture or fule cell or EMF by opposable magnets. Ion propulsion wouldnt need the shileding and reactor . Also, ion propulsion would have an almost inexhaustible source of fuel while a nuke reactor may have a finite operating period of 50 years or less.(kinda like an aircraft carrier no?)
SOmebody call georgeob, he was a skipper of a nuke ship.
BillRM
 
  1  
Reply Wed 20 Jan, 2010 08:22 pm
@farmerman,
Farmerman Ion propulsion is great with it very high special impulse however it is great, as you had pointed out where you do not need a large change of del-V in a short time period.

For getting a mass off earth it is worthless and it main benefits is in long range unman space probes where time is not of great concern and it is similar in that regard to solar sail technology.

Ion propulsion also still need a power sources such as solar cells or further always from the sun nuclear batteries. Ejection mass because of the high high special impulse needs are tiny but you still need a source of energy and unlike chemical rockets the mass you are carrying as ejection mass does not also serve as an energy source.
0 Replies
 
georgeob1
 
  1  
Reply Wed 20 Jan, 2010 08:44 pm
The U.S. has already used plutonium power packs on several long range space probes - Cassini was one of the earlier ones. There were other classified programs as well - some going back several decades.

The nuclear-powered aircraft never got very far. It was at best a very defective idea involving many never answered questions - the salient one being, what if the aircraft crashes? In addition nuclear powerplants operate at relatively low temperatures, making any kind of jet propulsion seriously inefficient. Though the plant and its shield would necessarily be very heavy, the fact that no liquid fuel would be required more than adequately compensated for that. Indeed, in principle the aircraft would have exceedingly long range.

The reactor design project failed at a very early stage and the project was quickly abandoned. The site at the Idaho National Engineering Laboratory was still fenced off when I was last there. The prototype reactor suffered a prompt critical accident induced by operator error, killing both operators then present.
BillRM
 
  1  
Reply Wed 20 Jan, 2010 09:03 pm
@georgeob1,
Crashes? You shield the nuclear material of the reactor in a case that can take any impact from a crashing plane.

That is not all that hard to do as the nuclear batteries in the space probes are so design and we move many many tons of nuclear waste around in containers that had been tested by mounting them in the front of locomotives and then running the locomotives into a concrete wall at full speed.

As far as low temperature in aircrafts you have a point however the Orien spacecraft design did not have a low temperature problem!!!!!!!!!!!
georgeob1
 
  1  
Reply Wed 20 Jan, 2010 09:15 pm
@BillRM,
I don't think you have an adequate appreciation for the violence of a plane crash; the structural requirements associated with a dense reactor & shield; or the likelihood of a crash in the case of a combat aircraft.

Jet propulsion in the atmosphere requires high gas temperatures. Ion engines in deep space are an entirely different matter.
BillRM
 
  1  
Reply Wed 20 Jan, 2010 10:14 pm
@georgeob1,
Let see as far as spacecrafts are concern the Orion drive is a large numbers of tiny nuclear devices explosions behind a pusher plate, so there is no lack of high temperature as in the core of the sun.

Next as far as aircrafts are concern why are you be limited by the fluid temperature of the reactors? You could just as an example take in air and used the reactors power to compress the air in order to reach any temperature you could wish for. The reactors operating temperatures would not set a limit on the gases coming out of the engines.

Next, the violence of planes crashes had never been enough to break open the casing of nuclear bombs that had gone down with aircrafts so why would you think it would be enough to break open the casing around a reactor core if the core had been design to take that kind of punishment?
georgeob1
 
  1  
Reply Wed 20 Jan, 2010 10:35 pm
@BillRM,
You need to study some physics.

In deep space there is no fluid resistence. Any net force from the engine will produce acceleration. Thus an "engine" spitting out individual ions in a fixed direction is capable of producing significant acceleration in the opposite direction.

In the atmosphere the air resistence works to decelerate any moving body. it takes the thrust of a jet engine just to overcome the drag and maintain speed. A jet engine requires a source of gas at a high temperature and pressure. The metalurgy of the cladding on nuclear fuel elements generally restricts a gas cooled reactor to temperatures below what is required for an efficient jet engine. It could work, but it wouldn't be very efficient. An aircraft with a heavy low efficiency engine isn't much of an aircraft.

With respect to plane crashes, you have your facts wrong. One could certainly build a structure strong enough to enclose the gas cooled reactor. However it would likely be too heavy to fly.

In any event the Air Force very quickly dropped all research on nuclear powered aircraft.
BillRM
 
  1  
Reply Wed 20 Jan, 2010 10:54 pm
@georgeob1,
Cannot see what you are talking about please show me where I or Farmerman for that matter stated that an Ions drive of any kind would be useful in the atmosphere.

The only nuclear means of getting a spacecraft off the ground that I been talking about is setting off tiny nuclear bombs behind a pusher plate and kicking yourself into orbit and the last time I check that have nothing to do with Ions drives!!!!!!!!!!!!!

Next you can power a compressor by mechanic means from a reactor and by simple physics IE see ideal gas laws, can therefore raised both the pressure and the temperature of a gas to any degree you care to do and this is completely independent of the reactor fluid temperatures.

As far as the weight of a safety container being too great for an aircraft to lift I see no reason to assume that would be true and what are you basing that on? Just a feeling?
georgeob1
 
  1  
Reply Wed 20 Jan, 2010 11:19 pm
@BillRM,
.

I didn't read your earlier posts and don't feel restricted to responding to them. Instead I addressed only the fate of the ill-conceived and short-lived nuclear powered long range bomber.

It is pretty clear that you didn't read my posts either. The only use I posited for a nuclear rocket engine was in deep space - that is where the Russians plan to use theirs.

As for the rest, I think you have been reading too much popular mechanics or something like that. Your intuition about the design tradeoffs involved in propulsion systems and all the rest is seriously deficient.

BillRM
 
  1  
Reply Thu 21 Jan, 2010 12:16 am
@georgeob1,
Well if you care to object to positions, no one here had taken feel free but it seems somewhat pointless.

Second, where you truly need the awesome power of nuclear energy is getting into orbit not afterward. Once you have force, your ship thought the atmosphere and achieved a del V of 18,000 MPH beside you are more then half way to anywhere in the solar system.

I did have the del V break down for a surface to surface journey to Mars using a Hohmann transfer orbit however I can not at the moment place my fingers on it and I am way too tired to try to recalculate the numbers, still once in earth orbit you do not need a great deal more del V to get to Mars orbit.

As far as your opinion of your ability to do aeronautic engineering you, seem to be slightly overrating yourself in my opinion.
0 Replies
 
farmerman
 
  2  
Reply Thu 21 Jan, 2010 05:56 am
@georgeob1,
WAIT A FUCKIN MINUTE!. I asked for georgeob to drop by (since I think hes particulrly experienced in aircraft AND nuclear powered oceanic vehicles).
1There is no disagreement re: ion propulsion. It was meant, as a simple discussion point re: an engine that is made for deep space propulsion.I meant that it was to be launched from space for interstellar flight. NOT from the earths surface . (It would be built in orbit and then flown away from home)
My real question was whethera nuclear power plant (Critical mass to sustain power) could even be used in outer space for propulsion into deep space since the critical mass of fuel does have a finite life, the amount of which may actually be less than the mission requires. THATS my reason to have Georgeob's opinion since he ran a nuke carrier
We understand that nuclear "batteries" are used in several probes but, I always thought that these were waaay sub critical masses and were merely used as energy for small digital appliances.

The closest to a critical mass in a satellite that I was aware of was that Russian satellite that came crashing down into NW Canada about 20 years ago. However, I think that, even that one was a sub critical nuke device
BillRM
 
  1  
Reply Thu 21 Jan, 2010 07:15 am
@farmerman,
I been focusing on solar system probes and far more important to me man missions out to at most a few hundred AUs of the sun not interstellar probes and that in my opinion seem very far in the distance future from our current abilities. The whole solar system distances can be measure in terms of light hours and the nearest stars to us in light years and most stars that might prove interesting to us in term of light centuries. The moon is just over a light second from the earth as another example of the ranges of distances we are talking about.

Half-life of reactor mass seem to be the lest of the problems in such long term probe missions as the half live of Plutonium 239 for example is of the order of 24,000 years and it will be a long time before any human build machine will be able to function for that time span or anywhere near it.

Now as far as critical mass is concern you are correct nuclear batteries used materials with short half-lives in the range of a hundred years or less and therefore generate heat from their fast natural decay rate that is then turn onto electric and have nothing to do with critical mass.

All in all it is my opinion we are so far from being able to design probes able to function for longer then we had already been out of the cave that to worry about power sources for such probes now is pointless.

We might be able to tap the energy in the Vacuum of space or anti matter or at least fusion power that also does not have a half-life problems of any kind by the time we are able to sit down and design the first probe to the stars. One thing however I am fairly sure of is that current design of nuclear power plants will not be a part of any interstellar probe.
0 Replies
 
georgeob1
 
  1  
Reply Thu 21 Jan, 2010 10:13 am
@farmerman,
OK farmerman has posed some interesting questions. He is correct that most of the existing and earlier applications to which I referred did indeed involve sub critical electrical power applications. A couple of points;

1. The use of nuclear power to put spacecraft in or beyond earth orbit is both infeasible and unnecessary. We have ample rocket engines and the option to stage systems in earth orbit and assemble them there.
2. The use of "mini nuclear detonations" to propel a space craft in deep space is also infeasible and unnecessary. There is a minimum size involved in a supercritical nuclear detonation, and in this case "mini" is pretty large. Moreover, since there is no atmosphere in space there will be no pressure wave and no possibility of efficient capture of released energy by a "capture plate". The only thing that could be "captured" is the momentum of a small fraction of the released radiation and nuclides. That can be far more economically and efficiently done with an ion engine.

The question of a nuclear power reactor supporting long duration space flight is interesting. It isn't much of a trick to design a power reactor with fuel for (say) 50 - 75 years. We have 50 year reactors now in the Nimitz class carriers. (That is accomplished by using highly enriched uranium fuel and by doping the ractor core with consumable neutron absorbers such as boron, so that over the life of the core the product of the available fuel nucleus density and thermal neutron density is roughly constant.) I suspect the most challenging trick would be the engineering of the heat engine required to transform the thermal energy resulting from the capture of fission products into useful electrical energy; and shielding the human crew (if there is one) from the radiation --- and doing all this within the size and weight limitations applicable to space flight. The essential limitation here lies in the intersection of what is required for the design of a long-lived reactor core and what is needed for the heat engine, The metalurgy of a reactor core generally limits its internal temperature to something less than 1,800deg F. That in turn sets an upper limit on the thermodynamic efficiency of the heat engine used to produce the electrical power. This isn't seriously limiting in terrestrial applications, however on a very long space flight it could be limiting.

Fusion power generation has been under fairly constant investigation for about 50 years. We aren't any closer to a feasible containment solution now than we were 30 years ago.
BillRM
 
  1  
Reply Thu 21 Jan, 2010 11:46 am
@georgeob1,
Quote:
Moreover, since there is no atmosphere in space there will be no pressure wave and no possibility of efficient capture of released energy by a "capture plate". The only thing that could be "captured" is the momentum of a small fraction of the released radiation and nuclides. That can be far more economically and efficiently done with an ion engine.


Come on now you are sounding like someone who once claimed that rockets would not work in space as it have nothing to push against.

Layers of the pusher plate can and most likely would act as part of the ejection mass in space in the same manner as a heat shield of a returning space capsule being slowly burn off along with other ejection mass place either around the bomb case and or injected behind the plate milliseconds before the explosion.

The engineering had been work out in the late 50’s to early 60’s in some details and can be found online.

Quote:
Fusion power generation has been under fairly constant investigation for about 50 years. We aren't any closer to a feasible containment solution now than we were 30 years ago.


As other elements of interstellar probe technology is at least a few hundreds years into the future I have little question that fusion will be solve a lot sooner then the other problems.


georgeob1
 
  1  
Reply Thu 21 Jan, 2010 11:51 am
@BillRM,
BillRM wrote:

Come on now you are sounding like someone who once claimed that rockets would not work in space as it have nothing to push against.


I may "sound like" that to you. However, I made no such claim or assertion.

Your suggestions don't make sense. I suggest you study some real physics.
BillRM
 
  1  
Reply Thu 21 Jan, 2010 12:37 pm
@georgeob1,
Quote:
Your suggestions don't make sense. I suggest you study some real physics.


My opinion concerning you is that you sold my poor friend Farmerman a bill of goods as far as you being an expert in any manner on the subject at hand.

LOL your understanding of basic physic is superior to Physicist Freeman Dyson for example is that what you are claiming who did work on the Orion Project?

And as there are detail engineering studies of my nonsense that can be downloaded at whim I would question if your physics is better then some of the best minds of the late 50s and 60s including Dyson who worked on the Orion Project under government contracts and who also were the foundering fathers of our late 50s nuclear weapon programs.

Not to add all the highly train minds that had look at it in the decades after it had been cancel for safety concerns and political reasons not feasibility issues.
0 Replies
 
parados
 
  1  
Reply Thu 21 Jan, 2010 12:40 pm
@georgeob1,
Surely a spacehip could capture most of the energy of a nuclear detonation if it was built completely around the bomb.


Of course, the spaceship wouldn't be much use after the first detonation.
BillRM
 
  1  
Reply Thu 21 Jan, 2010 12:44 pm
@parados,
Quote:
Surely a spacehip could capture most of the energy of a nuclear detonation if it was built completely around the bomb.
Of course, the spaceship wouldn't be much use after the first detonation.


LOL and more LOL.............
parados
 
  1  
Reply Thu 21 Jan, 2010 12:45 pm
@BillRM,
Bill, you might want to reread what george actually said about the efficiency.
BillRM
 
  1  
Reply Thu 21 Jan, 2010 01:00 pm
@parados,
Quote:
george actually said about the efficiency.


Once out of the atmosphere the efficiency drop sharply and that is nonsense as the program at the time deal with means of keeping the efficiency high once in space and I did cover the means of doing so.

But my and Freeman Dyson understanding of physics is not up to George high levels. Poor Prof Dyson if he was alive today would need to go to George to learn some real physic it would seem.
 

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