Re: But on further regurgitation...
Posted by Southern Man on Jun 05, 2002 at 08:49
Re: But on further genuflection... (bobba)
ďAssembled as a self-contained unit before flight. No maintenance required.Ē
Follow me for a moment. Have you ever seen the construction details of a stick built house and a mobile home? The mobile home walls are tightly packed with insulation leading to rigidity of the entire structure. The walls are securely fastened to a steel frame under the structure. The wood house walls are mostly hollow. The ties to the ground are very few because weight will hold them in place.
A similar situation exists for creating a self-contained reactor. If you build it in place it can be a lot less rigid and therefore weigh less than if you expect to drop it from the sky. IMHO I see no way to build a steam turbine nuclear electric generator that can withstand launch and landing forces. The thermocouple solution is possible in small scale because there are no moving parts and so it can be more rigid. But that solution weighs about half a pound per watt even without bioshielding. Scaling up to the 300KW level would mean it would weigh 150,000 pounds even if we ignore the fact taht weight increases as the square of strength/size. Very possible to construct in an apartment building basement but not very mobile.
ďWithout shielding the steam you generate is going to contain radioactive particles.
not so really. ď
Yes, really. A thin container could contain the plutonium but any fission reaction (or fusion for that matter) is going to produce neutrons which will produce secondary radioactive isotopes. You canít keep the neutrons inside a container unless the container becomes very heavy. You are trying to make steam in the mud and you are going to produce radioactive dirt that will go up the steam line to your turbine.
ďGreat find!!! Much better. How much does it weigh compared to just shipping in the required fuel?
I'd think, and this is a guess, several orders of magnitude less, especially without the heavy shielding. It was designed pretty much for this very purpose after all. ď
See above estimated weight.
Ya know at first i thought this would be a fairly straightforward calculation but the more i got into the more i realized it was a bit over my head and there seems to be more than a bit of esoteric knowledge required.
And thatís one reason why I havenít just done the calculation and presented it for ridicule. The primary reason is that I have found that people are always convinced easier if they convince themselves by figuring out the answer themselves. It also weeds out those who have no interest in reducing their ignorance level. If you canít be bothered to think about what the solution might be then you arenít going to be bothered by the fact that you havenít a clue what reality might be.
But this is a very complex calculation subject to many errors. If I just presented my calculation we would end up discussing all the errors I made and losing sight of the real problem.
Iíll accept you Ĺ million hp/year. To move on from there I believe we should plan on at least 10,000Kg of people/food/air/water/shielding to lift. I have found a nice link http://www.marsacademy.com/traj/traj6.htm that calculates the velocity needed to get from the Earth to Mars. Since we are just spitballing an answer here, 3km/sec seems the right ballpark to get back also. So we need about 5e10 KgM^2/sec^2 in the payload. All we need to do now is add the fuel needed to boost this amount of fuel and the payload to Mars orbit. How are you at doing integral calculations? :)