Gubi wrote...
Flaser wrote...
Gubi wrote...
Chlor wrote...
That reactor is already almost 3 meters tall and 2 meters wide, and it would have to be fitted with enough armored plating to withstand a lot of force if it is to be used in combat. There's a reason we haven't fitted our tanks with nuclear cores already - they're to dangerous and take up too much space, it works on a submarine, but not on a (relatively) small tank. One of these mechs fitted with a nuclear core would suddenly weigh twice of what it already does. It's not a realistic idea.
"Force fields" in the regard of what they're talking about in that article is a long way from what I'd call a "field". A burst of electromagnetic energy that last for less than a second is not what I'd quite call "safe defence", it could never be used practically in combat.
Five years? No way, 50 years for this to leave the experimental labs, with luck. EDIT: - Alright, that might be an overstatement, but yeah, a few decades at the very least.
While I agree that it is, today, inconceivable to put together a mecha or a tank with these technologies and have it be efficient, I must bring something to attention: in the last 20 years, we have made more scientific discoveries than in the last century (maybe not as important for some, but valid and useful nontheless for the progress of science).
It took 5 years to perfect this portable nuclear core. In the next five years maybe they'll have discovered how to miniaturize even more. Maybe this "magnetic impulse" system will have improved greatly, and will have a reload time of fractions of milliseconds.
Not to say that I don't acknowledge that today it is impossible, but let us face it: science fiction is being caught up, or at least its borders have started merging with reality. And the process will speed up, until we either destroy ourselves or find an equilibrium.
1) The reporter who wrote article about "force-fields" is a dumbass, as he didn't understand what he was writing about. It's not a "force-field", it's reactive armor that uses a highly charged conductive layer sandwiched into the armor itself. When a penetrator makes contact (either the plasma jet from a shaped charge or a kinetic penetrator), the charge is discharged, vaporizing the penetrator and greatly reducing its effectiveness.
2) You can't miniaturize nuclear power-plants like you do computers. You gotta have a sufficient neutron-flux, to keep the reaction going. Using better enriched fuel, reflectors, etc. can make it smaller, however these have been developed long ago for submarine reactors... and such "mil-spec" reactors (running on highly enriched fuel, almost weapons grade) are still not small enough to fit on a tank that's reasonably small. (You can't just make it bigger... then it can't cross bridges that weren't specially reinforced, nor fit through tunnels and let's not forget that tanks are typically transported to the battlefield, as they're not designed to cross long distances on their own, so you'd need to redesign all your transport vehicles from ships, through airplanes/helicopters to trains.).
To follow up on both your points:
1) I had understood that this would consist of a discharge of an electromagnetic pulse aiming to disable/destroy/deviate incoming projectiles of balistic form.
My bad if I hadn't understood it well.
2)NOt in a tank, but in a giant mecha? Miniaturization has its limits, but to assume that we have attained the minimum size of a nuclear reactor when they have barely existed 50 years is preposterous.
Though I have little too no knowlegde of the functioning of a reactor (in details that is) and cannot verify your saying that a stable, minimum size of neutron-flux is necessary to enable fission, I can say one thing: that these mechas will need power.Lots of it.
If it is not nuclear power that will enable them to sustain themselves, then what? My hypothesis of the force field/energetic protection and generator duo needs a sufficient amount of energy to function.
Thus the energy supply needs to be enormous, for the mecha to be on the one part worth using and sustainable on long fights/distances.
Or my hypothesis is just not realistic and born from my scifi fed mind.
A nuclear reactor operates on the principle of nuclear fission sustained by a chain reaction. All known fissile materials, have a given probability to fission when hit with a neutron. This is not 100%. When fission *does* occur, you get fissison products (the split remains of the old nucleus) and 2 or 3 (on average 2.4) free neutrons, that can go on and produce further fission reactions... or just get wasted, being absorbed or leaving the reactor space without doing any work.
For a working reactor you need to keep the number of fissions going high enough by keeping absorption and neutron escape in control, so the reaction can sustain itself. Neutron flux, is a fancy way to refer to the neutron density for a given space.
Increasing the reactor / fuel size increases the chance of a reaction occurring, as neutrons have a lot more chance to split an atom as they need to go through more fuel before leaving the reactor.
The reverse is also true, the smaller the reactor, the harder to keep the reaction going, as you'll loose a lot more neutrons, escaping the reactor chamber without having caused a reaction.
Choosing the right fuel can also help, keep a high flux. Remember when I said that fuel doesn't have a 100% chance to fission? U-238, the bulk of natural uranium has a lousy tendency to just absorb neutrons (...and through a beta decay chain, eventually transform into Pu-239, the stuff used in neutron bombs). U-235 by comparison is quite a handy fuel, but you need to process your fuel with very expensive enrichment processes to increase its quantity.
(This is because U-238 & U-235 are chemically identical. They react the same way in chemical processes. The only way to separate them, is to use the minuscule difference in density - as U-238 has 3 more neutrons).
Having a highly enriched fuel will make absorption less likely, hence make it possible to build a smaller reactor.
...I could go on and on, the bottom line doesn't change:
These engineering constraints are dictated by nuclear physics itself, and are already pretty well known and we've already hit the physical limits of reactor design quite a while ago.
Some tricks may remain, like using fuel in liquid nuclear salts instead solid oxides, however I don't think you could make fission reactors small enough for use in most fighting vehicles.
(Isotope electric power sources are another issue, albeit even more - say a 1000 times - expensive then fission reactors, as you'd need to artificially create your fuel in breeder reactors. Americium was often proposed for this).