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Talk-Polywell.org • NTR fuel
Page 1 of 1

NTR fuel

Posted: Fri Sep 22, 2017 10:45 pm
by kunkmiester
Been reading Heinlein's Rolling Stones to the boy. In it they mention "stabilize monoatomic hydrogen" as the ideal fuel for the ship's rocket. Is such a thing possible?

I'd assume it wouldn't be stable long term, but if you could get a few hours out of it, it'd be practical for chemical rockets too probably. You wouldn't have to worry about energy to disassociate it, so all your energy would be go In into accelerating it, which is the point of using it in an NTR. I'd imagine most of the advantages would translate to chemical rockets however.

Re: NTR fuel

Posted: Sat Sep 23, 2017 3:44 am
by hanelyp
Mono-atomic hydrogen would be a chemical fuel, potentially the ultimate chemical fuel in terms of energy/mass if it could be stabilized without excess dilution. It has been proposed that deep frozen hydrogen could be irradiated to break apart the molecules. But that can only be taken so far before the self reaction rate becomes a problem even deep frozen.

Re: NTR fuel

Posted: Sat Sep 23, 2017 10:35 pm
by Tom Ligon
Realizing it may take some energy release hydrogen from them, wouldn't at least some of the metal hydrides essentially store monoatomic hydrogen? LiH especially.

Ability to store monoatomic hydrogen suggests, to me, some tricks other than chemistry may offer themselves. I remain convinced that coulomb shielding in metal matrices, which occurs in metal hydrides, significantly alters the energy required for some nuclear reactions (yeah, LENR).

Re: NTR fuel

Posted: Sun Sep 24, 2017 12:26 pm
by kunkmiester
Would a hydride be dense enough to provide as much hydrogen as a liquid fuel? It could certainly make an interesting hybrid rocket. I'm wondering how much monoatomic would increase isps, wpul it be enough to be worth it?

Re: NTR fuel

Posted: Sun Sep 24, 2017 1:37 pm
by Tom Ligon
Ultimately, we have to scroll this back to the start and figure out what the question is, and what constraints we're putting on the path to the answer.

We seem to be asking, what benefit is there to using monoatomic hydrogen, assuming you could achieve that.

The implication seems to be that we're stipulating a reaction rocket. Thus, cranking up specific impulse is the goal, which is exactly the same thing as saying we want to get exhaust velocity up. There are two ways to do that: increase the energy or reduce molecular weight of the exhaust product.

Could we go lighter than a proton? What about using positrons and electrons, separately but equally expelled at great velocity so that the net charge remains zero on the spacecraft? But the energy cost of creating bulk positrons is stupendous, and what we would be expelling would be in itself the ultimate fuel: matter/antimatter. So that begs the question, what about using photons ... the laser drive?

What we really want is a reactionless drive. Warp drive maybe. Some cramp-inducing twist of the right hand rule that produces thrust from the interaction of photons or raw manipulation of electric and magnetic fields.

Yeah, I'm getting out of control here. But the idea of bottling monoatomic hydrogen is rather thought-provoking. It supposes a way of bucking some pretty deep physics ... hydrogen molecules exist for some pretty basic reasons and yanking them apart, yet keeping them cold and very dense, suggest some wizardry that must make one ask, what else could we do with that sort of knowledge.

No answers here, just a hope that we do not, in fact, have all the answers yet, and need a few slightly crazy people looking for them.

Re: NTR fuel

Posted: Mon Sep 25, 2017 2:38 am
by hanelyp
A hydride would not have mono-atomic hydrogen, but be a compound with hydrogen. Mono-atomic hydrogen is hydrogen atoms not chemically bound to anything.

Re: NTR fuel

Posted: Mon Sep 25, 2017 7:00 am
by williatw

Re: NTR fuel

Posted: Mon Sep 25, 2017 9:50 am
by kunkmiester
I'm still waiting for the real Shawyer replication- - if he got his idea from how he had to adjust communication satellite orbits, a more comprehensive audit of a larger dataset will show a similar trend, and will show deviation from photon rocket thrust levels.

Monoatomic hydrogen I believe would essentially be an ion, and there are many examples of ions being held in solutions and other ways, acids being a poor example. Once you get some info on how much it would increase isp, you can see how much the few solutions we currently have are worth.

Re: NTR fuel

Posted: Tue Sep 26, 2017 7:41 am
by paperburn1

Re: NTR fuel

Posted: Tue Sep 26, 2017 2:00 pm
by Tom Ligon
We're working in the dark here. Doing a quick search on the topic, turns out this is an old topic on the site where the Polywell first gained a following, NASASpaceFlight.com. The topic includes posts by GI-Thruster (I believe this participant used a similar tag here).

https://forum.nasaspaceflight.com/index ... ic=17490.0

It would seem to me that storing monoatomic hydrogen is probably futile. The reaction between free radical (neutral) hydrogen atoms and anything handy is pretty quick, and if you want that form, or more likely the ion, the best route is to dissociate H2 on the spot by zapping it with so much energy it can't stay associated. You do this in the process of accelerating it.

You could use methods such as RWB's relativistic electron beams, maybe a microwave resonance approach (ECR or ICR), etc.

Storing metallic hydrogen is intriguing. If you can achieve this state without massive support equipment on the spacecraft, it may allow propellant storage over long voyages. There was a glimmer of evidence recently that this might be possible, but then the tiny sample vanished.

Re: NTR fuel

Posted: Tue Sep 26, 2017 4:57 pm
by paperburn1
the other option would be to burn the h2 above 5000 C. it would dissociate into H1 and give you the same thrust.
But your right ,I would not want a bottle of H1 around because it just looking for an excuse to become H2 again and that would be a bag of bang right there,

Re: NTR fuel

Posted: Mon Oct 02, 2017 9:15 pm
by KitemanSA
Meta-stable hydrogen would ake a good fuel precisely because the energy needed to break the H2 bond is stored in the fuel. That is quite a bit of additional energy.