[Vehicles] How big should a self-destruct be?

[Fred Brackin]

Originally Posted by DataPacRat

Yet another technical question: Assuming that metastable nuclear isomers can, in fact, be stored and can also be detonated on command, is there any reasonable way to take your pile of the things and use them to generate electricity? And what'd be the most reasonable model - non-rechargeable battery, RTG, explosive-fuelled internal combustion engine...?

You want your metastable whatsits to fission because at least with the sort of uranium fission we're familiar with 94% of the energy is in the form of heacy charged fragments of the nuclei. When your options are gamma rays, neutrons and charged particles you want the last because it turns into heat readily.

so you could use these things to fuel more than one sort of heat engine as long as the radiation of not 94% isn't too bad.

[RyanW]

Originally Posted by DataPacRat

And what'd be the most reasonable model - non-rechargeable battery, RTG, explosive-fuelled internal combustion engine...?

Are you suggesting an Orion drive piston engine?

[DataPacRat]

Originally Posted by RyanW

Are you suggesting an Orion drive piston engine?

... I'm going to pretend I always intended 'yes'. :)

IIRC, gasoline has about ten times the energy content of TNT per mass; and these isomers have ten times that again. Assuming that whatever superscience is in play* to hold the isomers stable and trigger them can be scaled down arbitrarily small, and the carrier-substance can be thinned down to a liquid instead of just 'toothpaste', maybe I could treat an "isomer-gas" engine as needing 1/10th the gallons-per-hour of regular gas-engines. ... I should probably dig up that idea from GURPSnet's V2ad for "stabilized fuel tanks".


*: Hm, what sort of technobabble sounds right; "unquantized nucleon-field manipulation", maybe?

[DataPacRat]

Originally Posted by DataPacRat

... I'm going to pretend I always intended 'yes'. :)

IIRC, gasoline has about ten times the energy content of TNT per mass; and these isomers have ten times that again. Assuming that whatever superscience is in play* to hold the isomers stable and trigger them can be scaled down arbitrarily small, and the carrier-substance can be thinned down to a liquid instead of just 'toothpaste', maybe I could treat an "isomer-gas" engine as needing 1/10th the gallons-per-hour of regular gas-engines. ... I should probably dig up that idea from GURPSnet's V2ad for "stabilized fuel tanks".


*: Hm, what sort of technobabble sounds right; "unquantized nucleon-field manipulation", maybe?

Treating isomers as 10x TNT's energy density, and comparing that with GURPS fuels via Vehicles stats, I'm ending up with energy-storage about an order of magnitude higher than even GURPS' standard TL10 power-cells. Even by having to throw in intermediate steps like using an isomer-Stirling engine to transfer power to a battery (which can then dump out power a lot faster than the engine can), I'm getting much entertainment from considering the consequences. (Eg, "Gas-powered trucks on the moon! Who needs oxygen?")

There are two parts of the economy that I haven't quite sussed out. One is how large a large-scale isomer-maker has to be to be efficient enough that isomers could be sold at the listed $500/lb. The other is to figure out how efficient a small-scale isomer-recycler/exciter would be - eg, at 50%, I'd have to shove 2 kilojoules into the gizmo to charge up 1 kilojoule's worth of isomer - and what the limits of a gizmo of a particular size would be.

Anyone care to suggest numbers that make at least a reasonable amount of sense?

[Daigoro]

Have you checked the Wikipedia article? It has nuclear batteries that capture beta particles in a silicon P-N junction to directly create a current, rather than going the route of making a heat engine.

[Fred Brackin]

Originally Posted by Daigoro

Have you checked the Wikipedia article? It has nuclear batteries that capture beta particles in a silicon P-N junction to directly create a current, rather than going the route of making a heat engine.

Beta particles are electrons (negatve charge). Some of these would get created by the moving fragments of nuclei but those are going to be positively charged. You'd never get most of the energy messing about with electrons. Those would be secondary radiation.

[Anthony]

Nuclear batteries that use beta particles rely on isomers that undergo beta decay (usually Tritium), it's not really related to theoretical induced decay isomer transitions, which are gamma ray based (the material they talked about last it came up was Hf178m2).

[DataPacRat]

As far as I can tell, these are all the metastable isomers with a half-life of at least one year, which seem likely to be the ones easiest to stabilize with the Sufficiently Advanced isomer-stabilizing tech:

102m Rh, 3.7y
113m Cd, 14.1y
93m Nb, 16.13y
178m2 Hf, 31y
121m1 Sn, 43.9y
242m Am, 141y
192m2 Ir, 241y
108m Ag, 418y
166m1 Ho, 1200y
186m Re, 200,000y
210m Bi 3,040,000y
180m1 Ta, >10^16y

I'm leaning towards silver, bismuth, and/or tin as the base element of choice - they're reasonably abundant compared to the others and the handling properties are well-known. Presumably, slightly different end-uses would nudge companies to pick different elements to excite into metastable states. Eg, tin's probably the cheapest of those three, while bismuth would be favoured for minimizing the energy needed to be applied for stabilization for long-term storage.

[DataPacRat]

Originally Posted by DataPacRat

As far as I can tell, these are all the metastable isomers with a half-life of at least one year, which seem likely to be the ones easiest to stabilize with the Sufficiently Advanced isomer-stabilizing tech:

102m Rh, 3.7y
113m Cd, 14.1y
93m Nb, 16.13y
178m2 Hf, 31y
121m1 Sn, 43.9y
242m Am, 141y
192m2 Ir, 241y
108m Ag, 418y
166m1 Ho, 1200y
186m Re, 200,000y
210m Bi 3,040,000y
180m1 Ta, >10^16y

I'm leaning towards silver, bismuth, and/or tin as the base element of choice - they're reasonably abundant compared to the others and the handling properties are well-known. Presumably, slightly different end-uses would nudge companies to pick different elements to excite into metastable states. Eg, tin's probably the cheapest of those three, while bismuth would be favoured for minimizing the energy needed to be applied for stabilization for long-term storage.

After some further digging, if I limit myself to metastable isomers which only decay to stable isomers of the same element (so the Sufficiently Advanced tech can re-excite any nuclei that settle back into the stable isomer), my choices drop down to two: 92m Niobium, and 178m2 Hafnium. Given that about 60,000 tons of the former are already mined per year, and around 100 tons/year of the latter, it looks like niobium's the one for me.

[DataPacRat]

By the by, does anyone know offhand how much conventional explosive is used in a typical A-bomb, to compress the fissionables to criticality?


Also, while I'm thinking about it, how about how much gamma-emitting metastable isomer do you need to have before throwing in some tritium or other fusables would start adding to the explosive force?


I've found a lot of articles online about 'hafnium bombs', but none seem to have quite enough detail to convert into GURPS terms. And I'd like to have a better what sort of proliferation risks I'm introducing into the setting's background by adding isomer-based explosives. (There are already other new and fascinating forms of WMDs, but it's still a detail worth having an explanation handy for, in case it comes up, plot-wise.)