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Playing with Metallic Hydrogen

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Tue, 2017-06-27 04:36

DataPacRat DataPacRat's picture

Playing with Metallic Hydrogen

Premise: Spare synthmorph (from Gatecrashing) modified with Internal Rocket (from Transhuman). (... Am I the only one who's all too amused by the mental images of a fork-happy fellow sending hordes of customized, large-squirrel-sized robots tootling across the solar system, without bothering putting them in something as large as a spaceship?) Starting Numbers: A standard Spare weighs 2 kg; Internal Rocket creates 0.25 gravities of thrust for 90 minutes; according to this thread, metallic hydrogen drives have an ISP of 1,600. Calculations: That acceleration for that time provides a total delta-v of 13,230 m/s, which is reasonably nifty. Assuming that the 2 kg figure counts as the payload mass, then the rocket equation concludes that the morph, plus fuel, weighs a total of 4.65 kilograms. Assuming there's a bit of slack in that 2 kg number, enough that it includes the structural support and the equipment to keep the metallic hydrogen from immediately evaporating, that's over five and a half pounds of MH attached to a morph that's usually the size of a frisbee... ... So just how many ways would there be for a PC to void any warranties, and have fun with the stuff? :) As the most obvious example - the rocket normally has a mass-flow rate of around half a gram a second; how explosive would the results be if it was all released at once, such as by being in the middle of a firefight? The density I get for MH via Google is 0.6 g/cm^3, so the tanks for the modified Spare adds about 4.4 litres to the morph's volume. If all that hydrogen were converted into ordinary gas, that would be 29,483 litres, something like 6,675 times its previous volume. Put another way, that's enough to inflate a 10x10x10 foot balloon at standard pressure... or to double the air pressure in a 10x10x10 foot sealed room, which seems likely to rupture a few important gadgets (or biomorph organs), or even cause a blowout. And that's without even considering hydrogen gas's famous flammability. How expensive do you think a gadget to create fresh metallic hydrogen, to refuel emptied tanks, would be to nanofacture, and/or to run? How fast would it work? Is there any reason water electrolyzed into its component elements couldn't be used as feedstock? How expensive would MH be to buy in random places? (One possibility - if local water is already being split to create breathable oxygen for biomorphs, then the hydrogen might be little more than a waste product.) What are conditions inside the MH tanks like? For example, would it be possible to hide an object within that would be nigh-impossible to notice until the tanks were emptied, without significant damage? I found a note that MH can't be stored long at Venus's surface; what other sorts of environmental conditions might PCs venture into that would affect MH tanks? Is there any way to deliberately make MH tanks unsteady, or MH more volatile, ala the ultra-high-pressure versions of Things I Won't Work With? What other evil ideas come to your mind?

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Thank you for your time,

Tue, 2017-06-27 07:31

ubik2

Based on the numbers at

Based on the numbers at project rho, 2kg of MH has as much energy as 100kg of TNT. However, if people have figured out a way to pack it that small, they may have a stable system. We haven't created any, and while some scientists think it will be stable, others think tunneling effects will make it unstable. Perhaps a larger issue is that the combustion chamber for that 1700s Isp is 7000 K. MH is a good choice for delta-v, but it's not great for density, as you point out. Even in metallic form, it's still less dense than water. You may also be interested in nuclear salt water engines, with Isp values around 7000s, though your neighbors won't appreciate it. Really, if you're trying to seed the solar system (or beyond) with your morphs, the best choice is probably an ion drive, like VASIMR, with close to 30000s of ISP (with pitiful thrust). I don't know how you would shrink any of these designs small enough to work in a spare, but it's the future, so maybe there's something there. Edit: after reading other threads, I realize that the low thrust of the ion drives won't work for landing under any real gravity, or escaping your gravity well in the first place.

Tue, 2017-06-27 10:45

sysop

(You are definitely not the

(You are definitely not the only one amused by that image.)

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I fix broken things. If you need something fixed, mention it [url=/forums/suggestions/website-and-forum-suggestions]on the suggestions board[/url]. [color=red]I also sometimes speak as website administrator and/ moderator.[/color]

Tue, 2017-06-27 18:05

DataPacRat DataPacRat's picture

ubik2 wrote:Based on the

ubik2 wrote:
Based on the numbers at project rho, 2kg of MH has as much energy as 100kg of TNT.

This brings up some interesting questions about the legality of carrying the stuff around, especially in the less anarchistic juristictions.

Quote:
However, if people have figured out a way to pack it that small, they may have a stable system. We haven't created any, and while some scientists think it will be stable, others think tunneling effects will make it unstable. Perhaps a larger issue is that the combustion chamber for that 1700s Isp is 7000 K.

EP p347 mentions "it can be stabilized with carefully controlled electrical and magnetic fields, and these field generators are an integral part of every metallic hydrogen fuel tank", which is a good enough acknowledgement of the problem that I'm easily willing to suspend my disbelief, and accept that clever people had enough incentives to be able to come up with clever solutions. (Heck, people are already working out ideas for nuclear rockets whose cores are so hot they've turned to gas.)

sysop wrote:
(You are definitely not the only one amused by that image.)

Good, good. :) Next up - I ponder the rules on increasing Rep, to see if I can figure out how quickly this widespread-fork-family concept could increase its income, to pay for the morphs, rockets, and so on that much faster.

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Thank you for your time,

Tue, 2017-06-27 21:12

o11o1

Are we sure that Metallic

Are we sure that Metallic Hdrogen drive can even be made that tiny? The numbers we have tend to assume you're building your engine for big ships. I would imagine for a fuel tank that will more or less explode on you if it loses power (not unlike the big issue with antimatter) there will be parts that you cannot usefully miniaturize. I would expect a fleet of these would tend to be a net loss of currency from fuel costs, there aren't a lot of tasks that a 2 kilogram football with legs on a rocket can do that radio waves or a normal courier can't do better. Except for maybe one. What you really have here, is a smart missile that can evade most dumb ECM.

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A slight smell of ions....

Tue, 2017-06-27 22:43

DataPacRat DataPacRat's picture

o11o1 wrote:Are we sure that

o11o1 wrote:
Are we sure that Metallic Hdrogen drive can even be made that tiny?

Well, since EP is a point-buy system, and there's no rule against buying that morph with that add-on... :)

Quote:
The numbers we have tend to assume you're building your engine for big ships. I would imagine for a fuel tank that will more or less explode on you if it loses power (not unlike the big issue with antimatter)

Depending on how violently that power is lost, there may be enough safety features involved to slow the decay of the MH to avoid simple explosions.

Quote:
there will be parts that you cannot usefully miniaturize.

Plausible, but not confirmed.

Quote:
I would expect a fleet of these would tend to be a net loss of currency from fuel costs, there aren't a lot of tasks that a 2 kilogram football with legs on a rocket can do that radio waves or a normal courier can't do better. Except for maybe one. What you really have here, is a smart missile that can evade most dumb ECM.

There's a second aspect in which a Spare with Internal Rocket beats a Courier morph; a Courier costs at least 40,000, while the Spare is a mere two Moderate costs, or 2,000. I can see a lot of potential advantages of having 20 Spares tootling around instead of a single Courier. (For example, ferrying a set of one-time pads around, to allow undecryptable comms when an expensive quantum comm system isn't available.) I've had another thought about MH today - if the stuff can be contained safely enough that the authours didn't feel a need to include rules about MH tanks exploding, and it can be released controllably enough to be used for rockets... how hard would it be to hook up some kind of microturbine, or a more advanced conversion system, so that the rocket exhaust provides power instead of thrust? MH is a /lot/ more energy-dense than standard chemical-storage systems like traditional batteries or petrochemical fuels, and could possibly even out-perform superconductive storage systems. (Of course, the electrical fields used to contain MH stably might also be used to let superconductive power-storage systems similarly exceed the storage-density you might expect; and whether or not that's true, there could be issues with how much power is needed to keep the system in check.) Could still be some niche applications even if all those problems remain problematic.

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Thank you for your time,

Wed, 2017-06-28 05:43

ubik2

The optimistic MH engine is

The optimistic MH engine is probably the easiest to miniaturize, since it's so simple. Presuming containment is a non-issue (it might be, and in any case EP says it's possible), all you have to do is heat it up to 1000 K, and out comes pressurized gas. Much like what you'd use on an EVA, except a *lot* more thrust and heat (hotter than the surface of the sun).