Disposable Power Armor

[Pulp Hero]

A concept I had, discuss feasiblity of it. I am not an expert in science or economics.

The US government has a history of leaving military equipment behind. Hueys in Vietnam, small arms in various conflicts.

A major power will have major industrial output.

Getting objects onto a planet's surface is far easier than getting them off.
***

So a major power in a sci-fi war develops power armor meant to be used in quick drop pod or fast shuttle style insertion for hit and run raids on planets that are behind enemy lines.

The power armor is disposable, designed to be quickly taken off at the end of a mission and possibly with a self distruct feature to destroy the armor.

This is because either the fuel used in the extractration craft is expense, more so than saving the armor, or due to weight limits on a small extraction craft used to retrieve the special operations soldiers.


Thoughts, comments, childish insults?

[DPDarkPrimus]

Can't be too hard to make if they're disposable.

[Pulp Hero]

I'm thinking the are like the Sherman tanks of power armor and they use a lot of solid metal for armor rather than more advanced techniques.

[Fingolfin_Noldor]

The question is cost. If the power armour is expensive enough, I don;t think the military is too inclined to just destroy it just because it is a little damaged.

[Pulp Hero]

The question is cost. If the power armour is expensive enough, I don;t think the military is too inclined to just destroy it just because it is a little damaged.

Er, the premise is that it is cost saving because the fuel costs of transporting it are higher than making new ones.

[Fingolfin_Noldor]

The question is cost. If the power armour is expensive enough, I don;t think the military is too inclined to just destroy it just because it is a little damaged.

Er, the premise is that it is cost saving because the fuel costs of transporting it are higher than making new ones.

Well, yes, but you mustn't forget it cost money to transport it to the battlefield as well.

[defanatic]

The question is cost. If the power armour is expensive enough, I don;t think the military is too inclined to just destroy it just because it is a little damaged.

Er, the premise is that it is cost saving because the fuel costs of transporting it are higher than making new ones.

Well, yes, but you mustn't forget it cost money to transport it to the battlefield as well.

But one way, gravity is your friend. The other way, it is your foe. Maybe if the extraction shuttle isn't powerful enough to take a squad of power armoured soldiers off the ground, and making it too big would make it very vulnerable (and also hard to maneuver).

[Howedar]

The energy cost in fighting a gravity well is insignificant compared to the energy needed to accelerate/decelerate a ship enough to move between star systems in a reasonable time.

[defanatic]

The energy cost in fighting a gravity well is insignificant compared to the energy needed to accelerate/decelerate a ship enough to move between star systems in a reasonable time.

And the other point I made?

[darthbob88]

The energy cost in fighting a gravity well is insignificant compared to the energy needed to accelerate/decelerate a ship enough to move between star systems in a reasonable time.

And the other point I made?

If you have enough power to engage in interstellar warfare, you have enough power to pull up a few measly troopers in power armor.

[defanatic]

The energy cost in fighting a gravity well is insignificant compared to the energy needed to accelerate/decelerate a ship enough to move between star systems in a reasonable time.

And the other point I made?

If you have enough power to engage in interstellar warfare, you have enough power to pull up a few measly troopers in power armor.

Because power is perfectly transferable and efficiently usable in all cases. Perhaps the warship cannot land (for whatever reason, let's say that it might get badly damaged if it attempts landing in a hot zone, and may also have to wait a while undetected for the power armoured troops to arrive), so you send down a smaller, stealthy shuttle, which doesn't have big powerful engines (BTW, the shuttle rides on the warship, so it doesn't have interstellar capabilities). The marines get back, dispose of their power armour, and ride on back to the orbitting warship.

[kinnison]

The energy cost in fighting a gravity well is insignificant compared to the energy needed to accelerate/decelerate a ship enough to move between star systems in a reasonable time.

The assumption there is that you are travelling in real space. Given that assumption, which leads to another one (that FTL travel is impossible), it's difficult for me at least to imagine a scenario where it's worth the effort - minimum 4 years for the trip? And 4 years back, even at large fractions of c?

[Plekhanov]

Because power is perfectly transferable and efficiently usable in all cases. Perhaps the warship cannot land (for whatever reason, let's say that it might get badly damaged if it attempts landing in a hot zone, and may also have to wait a while undetected for the power armoured troops to arrive), so you send down a smaller, stealthy shuttle, which doesn't have big powerful engines (BTW, the shuttle rides on the warship, so it doesn't have interstellar capabilities). The marines get back, dispose of their power armour, and ride on back to the orbitting warship.

Nobody suggested that intersteller warships would inevitably be used to go down into the gravity well just that in all but the most contrived universes (ie one with cheap ftl travel, cheap resources & manufacture but expensive energy) disposable power armour would make little sense.

[Alan Bolte]

I think we're getting confused between 'disposable by design' and 'disposable because we don't need them anymore.' For the latter to happen, you're generally going to need a fairly big conflict in which a significant percentage of the designing nation's economy is mobilized, such that when the conflict ends and the economy is demobilized, the much smaller military will have no use for all that equipment. You're also going to need a universe with a significant rate of technological progress, otherwise it would be worthwhile to mothball all that equipment for the next big war.

If a smaller scale is required, I can see the power armor being sacrificed in favor of more boots on the ground for a few very important spec ops missions, but disposable by design still seems unlikely at best.

[Sikon]

This is because either the fuel used in the extractration craft is expense, more so than saving the armor

Fuel costs aren't likely to be that extreme compared to the hardware expense of power armor.

Even today, fuel expense isn't that high.

It is only having expensive hardware not able to be amortized over many launches that currently leads to high costs for space launch. As one random example, a launch of the Atlas D used about $0.04 million of kerosene and liquid oxygen, converted to today's dollars, while the rocket itself cost $27 million.

Like that illustration, typically propellant expense is vastly less than hardware costs today ... two or three orders of magnitude less.

The above is shown in more detail within my old post here.

Of course, a civilization with far more advanced technology than today may have space launch much different from the Atlas D developed back in 1959, and the fuel may be different. But it should be roughly either the same order of magnitude or lesser expense for the fuel, though space launch hardware should be less expensive per use if people are living beyond earth at all.

Keep in mind that the energy used in getting out of a planet's gravitational well, although significant by terrestrial standards, is rather small by most sci-fi standards.

For earth, the theoretical minimum energy required to reach low earth orbit (LEO) is about 30 MJ per kilogram before inefficiencies, mostly from the ~ 7800 m/s orbital velocity for LEO with KE = 0.5 MV^2. (Reaching escape velocity is about 60 MJ per kilogram ... nominally 63 MJ/kg).

Indeed, for perspective, though low velocity in comparison, for a 747 airline aircraft to keep flying against air drag for a whole long trip can take a comparable order of magnitude of energy, although delivered at lower power consumption rate in a different manner and without needing onboard oxidizer. A 747 can consume up to 240,000 liters of fuel during a long international flight, while carrying around 400 passengers.

That's around 600 liters per passenger of the aircraft. The fuel's energy content is about 33 MJ per liter.

The resulting energy consumption of a flight of the 747 aircraft is up to about 20000 MJ per passenger, which makes the 30 MJ per kilogram of orbital velocity not seem so enormous in comparison.

Remember, reaching LEO is just like 3000 MJ per 100 kilograms before inefficiencies.

Of course, reaching orbit isn't just the same as the theoretical minimum energy. Rockets have energy go into accelerating unused propellant and all dry weight as well as payload, suffer from drag during the starting portion of their trajectory within the atmosphere, and experience more loss from gravity than the theoretical minimum (depending on thrust to weight ratio, varying throughout the flight). They must carry oxidizer onboard and have rocket engines rapidly consume all their propellant in a few minutes with the resulting performance demands on turbopumps and more. However, the preceding shows the general order of magnitude involved.

It is thus no surprise that the actual fuel cost of reaching orbit isn't very high, not like the astronomical hardware and operations cost today.

or due to weight limits on a small extraction craft used to retrieve the special operations soldiers.

On the other hand, that could be a reason in some scenarios. For example, what if the interplanetary transport has limited cargo capability when in a hurry to get there at maximum velocity and what if it must drop down equipment taking time to get enough hydrogen propellant from the planet's water for nuclear thermal rockets?

Then the mission constraints could make it troublesome to get any extra mass off the planet.

In that case, such could be the future equivalent of a cruise missile strike using multi-million dollar missiles today ... expending a lot of expensive hardware because the mission was militarily or politically considered worth it.

I'd use the term expendable rather than disposable, though. As an analogy, a million-dollar cruise missile isn't just disposable, but it certainly can be expendable if the mission is worth it.

[General Zod]

Because power is perfectly transferable and efficiently usable in all cases. Perhaps the warship cannot land (for whatever reason, let's say that it might get badly damaged if it attempts landing in a hot zone, and may also have to wait a while undetected for the power armoured troops to arrive), so you send down a smaller, stealthy shuttle, which doesn't have big powerful engines (BTW, the shuttle rides on the warship, so it doesn't have interstellar capabilities). The marines get back, dispose of their power armour, and ride on back to the orbitting warship.

Why make it needlessly complicated? If it requires a lot of acrobatics to make the plot device work that doesn't necessarily add anything to the given setting or story, then perhaps it isn't a very good one?

[Starglider]

With sufficiently good nanoassemblers, the cost of anything but the most exotic materials is the cost of the elements needed to make it and a fairly trivial amount of energy (compared to interstellar travel or even orbital insertion). Thus your civ probably has 'sufficiently advanced nanoassemblers'. Even if they somehow didn't, being able to make powered armour that cheaply implies the ability to make all kinds of other sophisticated technological artefacts very cheaply.

[Azazal]

Back in Dragonstar Rising/Living Steel, bit of an obscure sci-fi RPG, there were Templar power armor suits provided by Neemis Enterprises. They were lightweight, easy yo make suits that were worn by "volunteers", usually criminals and other unlucky people pick up form the street, who were pumped full of a battle drug cocktail and let loose on the battlefield. They would be hired out as mercenaries that a power could use to take the brunt of a fight, allowing for one's own troops to avoid the worst of the action. Minimal electronics, no redundant systems, no back armor. Just omething to take a few hits before being killed in.

[frogcurry]

In a forced withdrawal scenario, it might be preferential to leave behind equipment simply due to the fact that inadequate transport ability exists to get it off planet or out of the star system in the remaining time. What lift and transport capacity exists would be used for the less replaceable human components rather than re-manufacturable machinery.

Of course if you could disable or destroy it before withdrawal, that would be best, so it can't be used against you. For something as advanced (and inherently complex) as a power armour used by an interstellar civilisation, disabling their equipment beyond use quickly should be easy. On the other hand, you don't want to allow an enemy to disable your suits by remote in battle, so they'd probably need to be hardwired such that they can only be disabled in person. So if you want to theorise a situation where they might fail to disable the equipment left behind before withdrawal, a lack of time and suitable access to activate the disabling protocols would suffice.

[Beowulf]

Disabling a suit should be as relatively simple as shooting up the computer. It should be under armor, but you can shoot it from the inside, thereby circumventing that. Also, thermite grenades or similar would probably be better. Just toss one in each suit.

[Connor MacLeod]

What is the fascination with power armour, anyhow? In specific situations or as a supporrt platform it makes some sense, but it has some rather nasty drawbacks (being a hugely visible target due to cooling needs is one.)

If the whole "cost of deploying troops on planet" is a problem, just minimize the equipment issue. Cut out tanks, and artillery and all that. Rely on orbital and/or aerial support and if needed orbitally deployed combat drones/robots. Make the drones/robots expendable. Make the kamikaze/self destruct function part of their ability to inflict damage on the enemy.

[Ford Prefect]

What is the fascination with power armour, anyhow?

It's awesome. I think that's a pretty valid reason to do pretty much anything.

[Cykeisme]

If we're dealing purely with energy savings by saving weight when putting back gravitational potential energy into our troops as they leave, perhaps we can just leave the heavy parts of the armor behind?

For example, the massive solid armour plating can be left behind, while keeping the much lighter electronics.. perhaps also keeping the servomotors, power plant etc.

I'd imagine this approach (leaving armour plates behind) is also viable for larger vehicles in a similar hypothetical sci-fi scenario.

[Phantasee]

frogcurry, I take it you meant a Dunkirk type of scenario?

To be honest, that's the only way I think the OP would work out. Not on a day-to-day basis, but that once-in-a-while-when-we-get-surrounded-by-Germans type of event.

[Beowulf]

The fascination with power armor is the steady trend of adding more weight to an infantryman. With power armor, you can stick heavier and more effective armor him, and also be able to stick more supplies, etc on him. Depending on exactly how much power output you need from the suit, the cooling needs may not actually be that great.