Part of the problem is also that you're not talking about driving a "simple" machine like an excavator's diesel. The kind of articulation required for just the basics of walking involves dozens of different muscles, all of which are hooked up to pull in not quite identical directions. You don't have a fairly linear drivetrain like in a car... you've got to move that power from one part of the suit (the power pack, if you will) to lots of others (the actuators) in some efficient fashion. Hydraulics are pretty efficient... pressure goes down the pipe. But they're bulkier and heavier than, say, electric motors... but converting from physical force to electricity then back again is an efficiency loss... the issue goes on.

If we're talking about a strength-augmenting suit slinging heavy armor on it, in addition to warfighting gear, the difference between "it runs on 2 liters of gasoline a day" and "it runs on 20 liters of gasoline a day" isn't more than 40 pounds or so. Not a huge number if we're talking about a few hundred pounds of suit/armor/kit being moved by a power source. So, given that, I've got a feeling the issue has more to do with articulation and mobility. Stuff like the eLEGS and HULC seems to be addressing the articulation and mobility problems to start with... now let's give it another 10 years.

I work as an EMT in an urban setting. I'm amused thinking of the kinds of mischief a rescue firefighter-paramedic could get into with a strength-augmenting exoskeleton.

Should we then include the "efficiency" related to converting bio matter to oil in the first place?

I don't think so if we want to compare fuel efficiency in converting whatever something "eat" into mechanical energy. You don't put biological matter to be turned into oil and then refined in the tank of your car, but gas or diesel (or alcohol, vegetable oil or other alternative fuel), while a human being usually don't thrive on pure glucose.

while true, said gas or diesel has to be refined from something before it can be used by the engine. Humans can live off the land if need be. And iirc, modern offensive military forces are trained to do just that to one degree or another.

But the refining is not done in the vehicule using the fuel, thus it's efficiency does not need to be factored into computing how much useful mechanical work you can extract from a given load of fuel, while a metahuman need to eat and digest the food he is carrying.

While foraging can effectively extend the time of operation of a metahuman unit (less food means more ammo for exemple), it use up time from the main mission.

"Every minute in the field spent looking for your next meal is a minute not spent looking for your next target." -me

I'm not entirely sure how much use this side arguement (glucose versus gasoline) is, since nothing happens in a vacuum.. A trooper with a bullet through him (which might have been stopped by the armor on a suit of PA) burns a lot of energy doing nothing much useful to the mission, once you figure in medivac, his buddies stopping to help him, etc. The armor isn't just a mobility system, it's a force multiplier.

And hey, scrounging for gasoline in an urban environment isn't impossible. Although I have a sudden image of insurgent fighters contaminating the gas tanks at gas stations, etc., before pulling out of an area and the resulting overextended PA units running into technical issues as the bad gas they acquire cripples their suits.

It's a stretch, I admit. I'm concerned about the suit's efficiency simply because if it ran off ICE then you have to factor in the size and weight of an armored fuel tank. I don't doubt these guys have support units right there, but were it me I'd try to make sure they could at least operate for at least eight hours before requiring a refuel.

Sure. At that point it's just a numbers game of "what's 8 hours of fuel weigh?" and "can the suit carry that much and still move effectively?" Or maybe we'll have a breakthrough in battery tech, or something. Either way, it should be feasible, it's just a matter of time and research.

Sorry to bring a thread back from the recent dead, but I just got to thinking; Couldn't metamaterials (in theory) be used as a type of ultra thin/lightweight rad shielding that would make portable reactor tech feasible?

perhaps, in the sense of routing the radiation away from the shield area rather then stop it outright. But i don't really know enough about the physics to say either way.

By 'portable reactor tech' I presume you mean a nuclear reaction of some kind? The first problem that has to be solved is making it small enough to be portable, then we can start worrying about radiation shielding. Remember that a nuclear reaction requires a minimum amount of material to occur. I don't remember the exact amount, but it is at least several kilos, around 10 I think, but it could be less.

Yeah nuclear was what I was referring to. I had questioned the plausibility of adapting the proposed tech from the Ford Nucleon nuclear powered car. Something like this might not lead to "Iron Man", but maybe something like the suits from "Exo-Squad" or bigger.

Yeah, not sure. The problem with nuclear power sources is that there are a whole bunch of problems. As I said, there is a physical minimum size just for the material itself. Then you have to remember that a nuclear reaction doesn't simply generate usable energy, it generates tons and tons and tons of heat, which is used to boil water which turns turbines which generates usable energy.

So, a few of the problems are:
Radiation shielding to stop the reactor killing a person. (Actually, wouldn't a lead lining solve this?)
Minimum size of the reacting material.
Have to convert heat to usable energy.
Have to prevent massive heat from escaping and melting whatever it is near.
Means of preventing catastrophic failure.
I'm sure some others that I'm not thinking of.

Now, there is alot of research going into sustainable cold fusion reactions, which would solve a few of the problems, perhaps most of them. It would still likely have to be 50+ kilos even at its best because it would need lead in its construction to prevent radiation. Portable, depending on your definition of portable. Unlikely to ever have pocket sized or anything like that, but could potentially stick it on an exosuit.

Oh, could also be powered by wireless energy transmission via magnetic resonance, an interesting new technology that does just what it says on the box, transmits energy wirelessly. Great part is that they actually already have it working. Not sure how well it handles transfer over longer distances, but it could be a possibility to have a large generator near the front lines transferring power to suits in this way (with batteries in case the power is interrupted of course)

Yeah, I was about to say we don't have true nuclear power: we have "advanced" steam engines that create steam by throwing water on radioactive elements.

Also, Slashdot has an article up right now claiming that these suits can be fielded by 2015.

I wouldn't doubt it. From what I've seen, the framework and 'muscles' are already done, and operation looked fairly natural. The main difficulty would be power, but if the suit can carry a few hundred kilos, it shouldn't be a problem to just stick a 40 kilo battery on it to keep it going all day long.

And of course there is a difference between 'can be fielded' and 'will be a battalion of them on the front lines.'

They might see use in forward bases for help with construction and various other heavy lifting tasks. That could likely happen in a year or two. They could likely get armored sentry type models for near base operations together in 5 years without too much trouble. Won't be a ton of them out there, but they will be 'fielded'.

I'm worried about the armor they'll be putting on these things. And how they'll look. As a US citizen who fully supports the military, we need to make sure these things look frakking awsome to make sure the other countries crap themselves instead of laugh at it.

Another possible power source would be RTGs, basically nuclear batteries, like what space probes use. I'm not super familiar with them but I know that waste heat is their main hazard rather than radiation... the Rat Thing in Snow Crash was a good example of RTG power in an exoskeleton (though that was a pretty heavy cyber-augment)

Ehm no. They're a good option for really long life, low power requirement jobs. A 50kg unit can power your fridge for decades, but they have nowhere near the output and weigth efficience needed.

https://secure.wikimedia.org/wikipedia/en/w..._rays#Shielding

depends on the amount of radiation given off.

lead btw have a weight of 11.34 grams pr cm3.

Gamma rays are btw the only real problem, alpah and beta are stopped by paper and aluminum...

You could use a tiny nuclear-thermal lightbulb. It's basically a lightbulb made out of quartz or silica filled with Uranium Hexafluoride that's induced into fission by spinning it into a vortex (usually) with superconductive magnets. A little casual reading indicates that they can be air-cooled, and there are a few different ways of scramming the reactor if something bad happens.

They have a few big advantages: they're relatively light, small, and are high power-output. It seems you can run a tiny NTL on a few kilograms of UF6. The lightbulb produces radiation in the hard ultraviolet range (UV-B), so is easy to shield against and not extremely dangerous. You could operate at 5 or 10% efficiency and still have more power than you need for the deployment time of an average power armor suit (4-6 hours, I suspect). Nuclear-thermal lightbulbs were originally investigated as an alternative fuel energy source for rockets in the 1970s, and a fair amount of data exists on how they work and what they're capable of.

Note that if the nuclear lightbulb is punctured, it will release what basically amounts to several kg of nuclear fallout superheated to thousands of degrees. So if you're going to build one, make sure you have a containment chamber armored to take a TOW hit. Even if the suit is disabled and the pilot killed, you don't want to dump radioactivity all over your battlefield.

Also, the technology is far from perfected: aside from some experiments in the 70s, nobody knows how difficult they are to actually use in a practical setting. I've read some articles which seem to indicate that they may be impractical because any dark spot on the bulb would cause it to explode and release the gas into your coolant.


Edit: Used the term 'fuel' incorrectly.

Then again, if they look silly and enemies underestimate the suits until they've conquered a country with a handful of suits....

While that power source is friggin' awesome, armoring it enough to take the kind of hit you're talking about would be implausible/impossible on something the size of powered armor, as an RPG-7 (one of the most common antitank weapons out there) can punch a HEAT round through 1-2 feet of tank armor. If nothing else, mounting a 4+ foot diameter sphere on the back of this thing is going to shift it's center of mass somewhat. Until we can make an IFV capable of taking an RPG hit (or a light tank for that matter) I don't think we'll see powered armor that can. Now, reactive armor might be one way to deal with those.

I have this sudden image of people protesting the use of weapons systems (read, guys in powered armor) that expose the battlefield to nuclear fallout, and the counterprotest that if people would just stop shooting at our troops and holing their suits, there wouldn't BE any fallout.

"Hey, we don't want war. If they would just surrender, it would all be over. They're the ones protracting this war, not us."

Who needs armor when one have a laser pod that can shoot down the rocket mid-flight?

http://cnc.wikia.com/wiki/Paladin_tank_%28Generals%29

funny, it didn't dawn on me until now how pretentious the tanks in that game was named.

I'm thinking of Raven from Snowcrash now

Please, those things are so dated.

Heh, should have guessed

A HEAT round can punch through 1-2 feet of undifferentiated steel with a direct hit. Tank armor is rarely undifferentiated steel anymore. Most MBT armor--and some heavy IFV armor--is a composite of some sort or another. More and more vehicle armor, additionally, is angled such that direct hits are difficult to pull off from ground level.

Some mixture of composite armor and angled plating would certainly do the trick, and wouldn't need to be nearly as thick. Assuming decent engineering and mechanical design, you could embed your containment chamber somewhere relatively low and less likely to be hit (the small of the back seems like an obvious place). In that case you might only need 5 to 10 cm of rear armor to deflect from the vast majority of combat situations. Front armor would protect the containment chamber from incoming fire from that direction. Weak spots would probably be directly beneath and directly above the machine.

That said, it's probably too dangerous a technology to do anything practical with, but it would be cool to see.

It occurs to me that a small gas turbine might be an ideal power source. It would have to be a hybrid system so you can swap over to the battery when the machine isn't moving, but gas turbines are high power output for their mass and reasonably fuel-efficient with requisite heat reclamation systems. There would be two engineering challenges: First, you would need to have the right turbine for your combat role -- to large a turbine and you're producing more energy than you need and wasting lots of fuel. Too small and your machine will be underpowered in combat; Second, you need to address the problem that turbines take a while to start up, so you could potentially deplete your battery before the turbine has a chance to kick in and act as the main generator.


All of the above assumes your powered armor is closer to the size of a large jeep--more like a Heavy Gear--rather than traditional "guy in a suit" power armor suits.

How long of a startup time are we worried about here? "Start" time for a conventional Internal Combustion Engine in a car is a second or two (depending on maintainance, mostly ) but the ICE in something like a Prius uses a high-speed starter engine that gets it up to speed quickly. While it can take a while for a turbine to wind up, having a heavy duty battery and starter might get you around some of that by "spinning up" the turbine very aggressively, electrically.

Helicopters and tanks use gas turbines. I'd say between 10-30 secs, but honestly that is just a pure guess.

Gas turbines can be made really, really small, I've heard of 1 inch gas turbines (experiments for powering laptops!).

Another problem with gas turbines is that they can't really idle.

Perhaps a two-step system, with a gas-turbine recharging batteries as needed?

That looks like it could be an option.

You might even want two different model designs: One that has a large turbine and a small battery pack--the batteries keep it powered up when it's stationary or under low stress; And one that has a small turbine and a large battery pack--the turbine keeps it moving on long-distance treks, but switches over to batteries for stealth ops.