But it isn’t going where you want to go. It’s meandering as the gravity field present wherever it is at that moment perturbs its existing velocity vector. Lather rinse repeat every second going forward in time.
The whole point of ship thrusters and such is to navigate; to move purposefully in a direction other than the local gravity gradient’s perturbations of your current velocity vector.
We’ve gone through several permutations. And the simplified case is just to see if it’s possible. And perhaps to study it.
But some ideas were to have it In a solar orbit out beyond Neptune. Or perhaps an interstellar mission. In both places, you would construct it on the coasting and orbital phase and stay with it.
There really aren’t any shortcuts to radiative cooling. No matter what exotic materials you use, no matter what state of matter, you’re still limited by total cross-sectional area (so fractal shapes with a lot of surface area scrunched up very small don’t help you) and temperature. A cloud of vaporized metal a hundred meters across doesn’t work any better than a sheet of solid material a hundred meters across.
I was hoping the run away temperature would be a feature, not a bug. To achieve the temperature needed to have the appropriate heat transfer. At T^4 it would seem to be pretty good heat transfer for high values of T no matter what the shape.
Not exactly. The level of isotope ratio (235 vs 238, for example) determines how fast it decays. Consider that neutrons come from 2 different sources - natural random decay, and emitted when an atom is hit by another neutron. (too fast with the latter and you get an explosion of sorts) The splitting also produces heat. the key to a stable blob is that the heat emitted balances the heat radiated away. We’re just suggesting a much higher stable temperature than one would really expect.
You don’t. That’s why the suggestion is the station - or the pieces that collect the energy - maneuver to follow it. The obvious suggestion is to put it at an L3 point so its location is generally fixed, and you must simply adjust to some meandering.
Whether it will evaporate when it is liquid, or a taffy consistency, is a good question. Otherwise one presumes like any liquid in a vaccum, surface tension will keep it in a nice neat globular form.
The problem isn’t cooling the reactor at all. The problem is cooling the thing that converts the reactor’s output into usable energy (usually electricity). The thing that converts the reactor’s output into usable energy has to be cooler than the reactor to work, because energy does not spontaneously flow from areas of low density to areas of high density. So the reactor has to ultimately heat the energy converter, and if the converter has no way to cool it will eventually reach an equilibrium temperature equal to that of the reactor and cease to be able to perform work. Now if you have an extreme difference like in photovoltaic cells, which convert sunlight with a blackbody temperature of 5700K° while operating at a temperature of 300K°, then the theoretical thermal efficiency is so high it looks like magic; the waste heat is easily rejected even in space. But that’s because the 5700K° light source only spans one-quarter of a square degree of arc with most of the rest of the sky available for heat rejection.
The simple solution would be to duplicate this by moving the panel far enough away from the heat source.
You’re not going to get a solid core nuclear reactor to operate at 5700K°, and in this case you can’t make up for quality with quantity: the amount of waste heat at the generator is strongly dependent on the temperature difference. And in any event you’re simply reducing how much energy reaches the panels to an amount low enough that the waste heat is tolerable. So now your reactor is simply throwing away most of its output. In the context of generating power for an ion or plasma rocket you’re faced with the irreducible problem that you want your rocket exhaust to be faster (effectively equals hotter) than your primary energy source. The only way to do that is an energy conversion cycle that inevitably generates large amounts of waste heat. If your reactor was somehow hot enough like a fission gas-core or fusion plasma design, you could simply heat the propellent directly.
Obviously not, but could one be created?
A standard star (a “fusion star” if you will) has a bunch of fusible material in a big pile; the fusion reaction generates energy forcing the material out, but there is so much of it that its gravity pulls it back in. A star is at an equilibrium state.
So… if we pile up a bunch of fissile material… it will eventually generate enough energy to push itself apart.
Could we have so much fissile material that the energy generated by fission is matched by the gravity of all that fissile material?
I suspect the answer is no, because adding more fissile material just adds more energy even faster.
Sounds like you are describing a big nuclear bomb. As many people have found out, you cannot pile together too much material before it goes critical, much less a star’s worth.
I think the answer is obviously yes since with enough material it forms a black hole.
Continuing after edit window closed on my fingers (ouch!):
However will the fission reactions be strong enough to prevent degenerate matter/ neutron star? One thing it has going for it is it’s going to be very dense so will have a small size relative to it’s gravity well, helping to keep it together.
As such a fission star may be something that can exist if formed but practically can not form. One of those ‘how did we get there situations.’
But if you form a black hole, it doesn’t matter if the uranium is radioactive or not - any energy generated past the event horizon will never ever interact with the rest of the universe, right?
Yes. The black hole mention was simply to establish the upper limit to show gravity would be the dominant force.
Thing is, if you just piled up enough uranium to make a black hole, I think you’d get an explosion, not an implosion. You’d need to shove all the uranium in with tremendous force above and beyond gravity, and once you’re past a critical point you’d get a black hole and then it wouldn’t matter what the mass is made of.
The obvious solution to the “generation” is to use a heat panel facing the blob to collect the heat; and have a long trailing pipe to a giant fan of raiant panels to coll the coolant, which gets pumped through, condensed, and returned for more heat - all the while driving a genearot.
The logical comeback is that now all you’re doing is putting 19th century technology in space, it’s not the simplest (or safest) option - too many things to go wrong.
But we’re talking hypotheticals, so it can be done. But the basic problem is that there is no simpler way to turn “waste” heat into useable power, and certainly no simple way.
The whole point of critical mass, as I understand it, was the distance a neutron has to travel before striking another atom (Uranium) and releasing multiple neutrons. This is affected by the size of the mass, the density and the mix of isotopes. So there is a critical mass, at which point the reaction will run away, as I beieve it was Szilard(?) who demonstrated. If a reaction generatess heat (and more reaction) far faster than the heat can disapate, severe expansion and RUD (rapid Unplanned Disassembly) is the logical outcome. I only minored in physics, but my unprofessional guess is that happens well before mass reaches black hole levels.
OK this has diverged to 2 different concepts:
1: Is a stable theoretically fission star possible. Is there a point or a range of points where gravity can confine a self sustaining fission reaction with the reaction producing enough heat to prevent the fissionable elements from degrading into degenerate matter? Somewhere between black hole and atomic bomb? I would think the density of the fissionable elements is so high which would allow a much greater gravitational force than say hydrogen so that would be a plus.
2: Can we use some melted down radioactive core slag as a long term point source of energy in space. Not atomic bomb strength, but something that can glow white hot for decades if not hundreds of years.
I was thinking that perhaps this is what happened with the planet Krypton. The uranium was running as a slow reactor mixed in the core, and it slowly migrated to the center over the ages due to gravitational forces on the heavier elements, until suddenly it reached critical mass and the planet blew up…
Or perhaps it was scientifically illiterate comic book authors pulling stuff out of their nether orfice?
Over the various retcons there have been alternate accounts of different baddies causing Krypton’s explosion.
I read Superman well into the mid-1960’s and don’t recall seeing any of these theories.