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Comment by msandford | Hacker News Reader

"which incorporates technology that makes it invisible to enemy thermal imaging"

I call bullshit on this one. The US M1 Abrams has a 1500HP gas turbine engine. To develop 1500HP means producing at least another 1500HP in waste heat, if not more like 3000-5000HP. Let's conservatively say it's 1500HP * 732W/HP ~= 1MW

How in the world do they think they're going to hide a 1-5MW power plant? From the second video: Peltier plates on the exterior.

That's great, but it doesn't do jack to the huge plume of exhaust jetting out the back. And since they've got some kind of fancy exhaust cooling system they've got to be sucking up and discharging MASSIVE amounts of air to dissipate several megawatts without increasing the air temperature too much.

Even then, it's not too hard to turn up the sensitivity on the thermal systems a bit so you can spot these things.

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I call bullshit on this one. The US M1 Abrams has a 1500HP gas turbine engine. To develop 1500HP means producing at least another 1500HP in waste heat, if not more like 3000-5000HP.

An electric drive system would alleviate a lot of that. For range, make it a series hybrid. It can recharge batteries en route, then operate in a "cool/stealth" mode, so that it can cool down and lie in wait under camouflage and in an enfilade position peeking over a ridge. For maximum stealth, we might want an electromagnetic accelerator instead of a cannon. Such a system would probably want to sacrifice physical protection from anything deadlier than high explosive artillery shells and machine guns for greater stealth.

While we are at it, why do we have to have massive armor and cannons? What if such vehicles could operate as "drone carriers" and launch swarms of drones which are designed as combined surveillance platforms and guided munitions? If you take something like an Abrams M1 tank and land a shaped charge on its main cannon and its tracks, then it just becomes a badly camouflaged machine gun nest. Once immobilized and de-fanged, its machine guns would then be easy to take out. Such drone-missiles can easily out-range the most sophisticated main battle tank gun.

EDIT: The lethality of weapons vs. armor has caused dramatic swings in the tactics of hand to hand weapons on the battlefield. It only makes sense that the increasing lethality of computerized weaponry would cause this to happen for armored vehicles. Knights in armor plate used to rule the field. Firearms made personal steel plate armor obsolete. It used to be that high velocity cannon and massive armor ruled the battlefield. Now it's detection and situational awareness.

So something like lightly armored rocket artillery with a screen of antipersonnel/reconnaissance drones that could paint targets for guided rockets. This might work well until you need to take enemy air force into account.

So something like lightly armored rocket artillery with a screen of antipersonnel/reconnaissance drones that could paint targets for guided rockets.

Not only that. The drones themselves could act as munitions. They could clamp themselves onto something like a main battle tank cannon and set off a shaped charge.

This might work well until you need to take enemy air force into account.

Make the drones small enough, and make them fly low enough, and it won't be as much of an issue. Also, this is why you have your own air force and surface to air missiles.

I was thinking about air force blowing up lightly armored rocket artillery. Also drones make natural target for automatic radar or lidar aimed weapons. I suspect there will be a race to make drones nearly invisible to that form of targeting in a few years as armies around the world equip them.

As with all stealth tech, the point is not to make it impossible to know that there is a tank somewhere there -- it's to make it impossible to automatically track by guided weaponry, and hard to acquire as a target when using an IR sight. For that purpose, dissipating all heat into air and thus cloaking the tank and everything around it in a cloud of hot air is an advantage, not a disadvantage.

It might be "invisible" only while standing still. This would still be strategically useful, at least from a defensive standpoint.

It might but the second video showed it in motion (30 sec mark) while "stealthed." Although it was moving relatively slowly.

Another posted noted that the prototype is based on a CV-90. That's not really a tank at all (Wikipedia calls is an "infantry fighting vehicle"). For those in the US it is roughly comparable to the Bradley Fighting Vehicle.

It has a 550hp Diesel engine, which is much easier to cool than a 1500hp turbine.

Jet engine on planes have a pretty serious thermal signature as well. That doesn't mean stealth technologies are useless.

I suspect invisible in the general case involved some poetic license. But improving the thermal characteristics even in limited circumstances is pretty valuable.

> US M1 Abrams

You're comparing an old, outdated lump of shit of a tank with a brand new 2014 design.

Source: My buddy works for the Defence Materiel Organisation in Australia, and had to buy a bunch of them.

Yeah, sure. It makes a lot more waste heat than a new one. That means that it might make 5MW of waste heat while the new 500HP diesel might only make 1.5MW of waste heat. Or a 300HP diesel might only make 1MW of waste heat.

It's 80% less! A megawatt is still a lot, though.

Maybe it's not so much about being completely invisible as being hard to localize by thermal imaging?

For instance, if they can dump most of the heat into the air, so that what the thermal imager sees is a big blob, then if you had several tanks advancing as a loose group, so their thermal blobs overlapped, someone trying to use thermal imaging to aim an anti-tank weapon might not be able to tell where to aim to hit the tanks instead of the spaces between the tanks.

A long insulated hose could exhaust the heat some distance away from the tank. Then it would look like a giant stealth rat.

What if it uses an electric motor? Imagine the usefulness of a hybrid tank, electric power for when you want to crawl in stealth mode and a huge diesel motor for when you want to floor it.

What if it had some sort of, uhm, "thermal ballast" that would be refrigerated during normal operation?

Then when danger is expected, run the peltier modules in reverse, transferring heat from the outer layer back into the center for a short period of time.

Peltiers are notoriously inefficient. Hideously. Reasonable numbers are in the 10% range. So in order to remove say 5kW of heat from the skin (1.5 tons of refrigeration) which is pretty conservative would require say 50kW of power. Most of which would end up as heat in the metal of the structure of the tank.

If you figure the chassis and armor are say, 50 tons, and steel, you can do a little math to figure out how quickly it would heat up. 50 tons is 50,000 kg and the specific heat of steel is about 0.5kJ/kgK. We're putting heat into the chassis at the rate of 50kJ/sec and things cancel out pretty nicely. You'd heat it up at about half a degree C per second, or about one degree F per second.

In the best possible scenario you're talking about no more than two minutes worth of stealth (perhaps only 30 seconds in reality) and that's with the tank not moving and only idling its engine, just enough to produce the necessary 50kW. It's a neat trick, but I'm not sure it's worth writing home about.

Storing the heat chemically, in an easily reversible endothermic reaction including but not limited to phase-change, could be much more efficient than using Peltiers to cook the crewmwmbers

Could you also carry liquid air, or compress it on the spot, and use it as a coolant?

It's Polish. For much of the year there is a reasonable supply of snow for cooling too.

"Ready for export in 2022", it says. That's a lot of countries you can't sell to if you have to rely on snow all year round.

3 months of snow most years, sometimes less.

Hybrid engines? if you can make the thing move cool for the last couple of miles that's a massive range of stealth.

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