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I recently began playing Fallout 4 and asked myself a question: Would it be possible to build a power armor with todays technology?

I did some investigation on servomotors and stuff and came to conclusion that it would be theoretically possible to build such a suit. The main problem, in my humble opinion as a non-engineer, would be the power supply, as strong servomotors need much more of it than for example solor cells could supply.

So here comes my question: What would be the smallest possible size of a functional nuclear reactor in theory (1) and in practice regarding todays technology (2).

Well, put on hold, okay... somehow restrictive. Can a moderator maybe move this Question to an appropriate StackExchange site please?

Martin Tausch
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  • A conventional nuclear reactor is, essentially, a steam engine of sorts, just with better fuel. I was hoping to write an answer, but couldn't find reliable figures on the heat produced by a single (small) pellet of fuel. Apparently it's enough for spent fuel to glow red hot, so my estimate would be the size of a small combustion engine as the lower bound. As a reactor is more complex, a normal petroleum engine would probably be more practical for power armor. – LLlAMnYP Nov 20 '15 at 08:41
  • I doubt that a normal petroleum enigne can provide enough power. I would roughly estimate the peek power consumption of such an armor at 500kW... at least... – Martin Tausch Nov 20 '15 at 08:58
  • @MartinTausch You're going to need some serious heat dissipation capability if the wearer is not going to be fried! – Selene Routley Nov 20 '15 at 09:07
  • @WetSavannaAnimalakaRodVance Thats true. This would be in need of a sophisticated water cooling system running through the whole armor. But I think this can be done, maybe with same practical disadvantages like a forced shutdown when overheated. Or do you disargree? If so, please explain :) – Martin Tausch Nov 20 '15 at 09:14
  • @MartinTausch is there any basis to this estimate? A 100kW petroleum engine has no problem moving my 1.6 tonne car around. The peak useful power needed to jump up 4 feet high, for example is about 30kW assuming a 500kg suit. I'd say, this suit needs a hybrid power station, but not like hybrid automobiles. Use supercapacitors when you need to do high power stuff like jumping and such and run on petroleum to charge them and do low power stuff like walking. – LLlAMnYP Nov 20 '15 at 11:23
  • Also, regarding petroleum engines' power-to-mass ratio, from the wiki article on the Smart Roadster "This V6 bi-turbo powerplant had a maximum power of 160 kW (218 PS; 215 hp) for a weight of only 840 kg". This is a complete vehicle that has about 500kg/100kW, not too far from my figures in the previous comment. – LLlAMnYP Nov 20 '15 at 11:30
  • Yes, there is a basis on this estimate. I will update my question with some figures. But it is obviously a huge difference to push an object on wheels on just one axis compared to a complex movement along at least 6/8 axis just for walking. How much weight can you carry by your hands? How much weight can pull on wagon? – Martin Tausch Nov 20 '15 at 12:06
  • Using supercapacitors sounds reasonable, but there won't be too much space left. The power supply would already need be worn as a kind of backpack. – Martin Tausch Nov 20 '15 at 12:08
  • Well, the 30kW I quoted for jumping is simply the mechanical power necessary. Regardless, wheels on one axis or not, it's simply a matter of applying force in the right places in the right ratios. If the efficiency of the suit degrades so badly, that for slightly more complex motion you already waste 95% of the available energy, then that's a whole 'nother bag of chips. – LLlAMnYP Nov 20 '15 at 13:15
  • Well, okay. Let's assume one arm of the suit is 1,1m0,25m0,25m = 68.750cm^3. Let us furthur assume it is mainly made of titanium (4,5 g/cm^3). That arm would weight >100kg. Let's assume the weightpoint is at 35% from shoulder joint to fingertip. A servo at the shoulder joint would then need 1000nm * 0.35 = 350nm to just lift the arm. According to Siemens SIMOTICS 1FT6-Servos, such a servo would consume >118kW. Did I miss something? Maybe there are more efficient servos, I don't know. As I said, I'm not an engineer... – Martin Tausch Nov 20 '15 at 13:33
  • The discussion is getting quite long, but there's not much time to chat right for me. I'd comment: surely you don't assume, that the arm is a solid block of titanium? But really, you can use a gearbox to magnify torque from a lower power servo, you can use counterweights/springs, etc. As rightfully noted by the mods, this is an engineering problem. Demanding ultra-high power to overcome engineering difficulties feels like a faulty approach. – LLlAMnYP Nov 20 '15 at 13:56
  • A solid block of these sizes would weigth >300kg. I asked for moving the question to another SA site... – Martin Tausch Nov 20 '15 at 14:05
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    https://en.wikipedia.org/wiki/TOPAZ_nuclear_reactor –  Nov 20 '15 at 14:17
  • @LLlAMnYP: Final comment: What would your estimated power consumption look like? – Martin Tausch Nov 20 '15 at 14:19
  • Powered exoskeletons for lift-n-carry support are an area of active interest for the US armed forces. But they're not armored because so far they don't work adequately even without all the extra weight. Nor is a human figure an efficient shape for armoring. There is a reason tank look like squared-off, squashed balls. – dmckee --- ex-moderator kitten Nov 20 '15 at 15:12
  • If engineering problems are overcome, I'd put petrol to actual mechanical energy at 1/6 efficiency at best. But mechanics themselves are easy to calculate. But you don't need to output peak energy constantly. If supercaps work, even a 50kW engine could potentially suffice. You just wouldn't be able to to be in combat for more than a few minutes. – LLlAMnYP Nov 20 '15 at 18:36
  • Also, to give an order of magnitude Raytheon's exoskeletons are apparently under development to cut down power required for walking to 3hp (about 2kW). You can check this link out: http://www.popsci.com/scitech/article/2008-04/building-real-iron-man – LLlAMnYP Nov 21 '15 at 14:06

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Considering that the fuel element is called "fusion core", I guess they use fusion reactors, not fission. But in reality fusion reactors are not cost-effective and require extreme temperatures to initiate a fusion reaction (see "tokamak" to get an idea and see the size).

There were some news about a team of scientists who made some progress on that kind of reactors, but we'll see if it's true.

Kosm
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