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Old 08-31-2017, 09:36 AM   #31
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Default Re: [Spaceships] Anti-Lithium for Drives – Does this work?

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Originally Posted by Fred Brackin View Post
I've never seen a proposal for an antimatter rocket with gamma exhaust.
I've seen proposals for utilizing the gamma rays produced by pion decays. About 1/3 of the energy of the exhaust will be from the decay of pi0 particles into a pair of absurdly high energy gamma rays. If you have a thick tungsten plate in front of your reaction chamber, you not only get radiation shielding from these gammas, but you capture their momentum and turn it into thrust for your spacecraft. The majority of the thrust still comes from re-directing the charged pions, but the gamma component is still a fairly significant minority.

You would also be getting the same benefit from the electron-positron annihilation gammas, but those will be negligible.

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Old 08-31-2017, 09:51 AM   #32
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Default Re: [Spaceships] Anti-Lithium for Drives – Does this work?

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If you have a thick tungsten plate in front of your reaction chamber, you not only get radiation shielding from these gammas, but you capture their momentum and turn it into thrust for your spacecraft. The majority of the thrust still comes from re-directing the charged pions, but the gamma component is still a fairly significant minority.
A thick tungsten plate sounds like just the thing to sour the thrust-to-weight ratio.
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Old 08-31-2017, 01:27 PM   #33
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Default Re: [Spaceships] Anti-Lithium for Drives – Does this work?

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The terminology is non-orientable wormhole. But yeah, I've been thinking that since I started reading this thread.

Luke
That sounds like the only way to feasibly use/create large quantities of antimatter "practically" without steamrolling through known and proven physics, as far as we know.
Probably not possible, but not proven to be so just yet.
Right?
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Old 08-31-2017, 02:56 PM   #34
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Default Re: [Spaceships] Anti-Lithium for Drives – Does this work?

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The terminology is non-orientable wormhole. But yeah, I've been thinking that since I started reading this thread.
The terminology is something my phone likes to autocorrrect so I look like an idiot.
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Old 08-31-2017, 07:55 PM   #35
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Default Re: [Spaceships] Anti-Lithium for Drives – Does this work?

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Originally Posted by Fred Brackin View Post
A thick tungsten plate sounds like just the thing to sour the thrust-to-weight ratio.
If you need radiation shielding anyway, its better than anything else you can use (lead is better on a per-mass basis at the same flux, but tungsten has a much higher melting temperature so you can get it much closer to the place where the reaction is occurring and intercept the same number of gamma rays with less area and thus less mass overall).

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Old 08-31-2017, 08:15 PM   #36
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Default Re: [Spaceships] Anti-Lithium for Drives – Does this work?

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That sounds like the only way to feasibly use/create large quantities of antimatter "practically" without steamrolling through known and proven physics, as far as we know.
Probably not possible, but not proven to be so just yet.
Right?
I've heard vaguely about q-balls reflecting matter into antimatter, but haven't looked into it enough to know if it is actually expected to happen or just people making stuff up. What we do know is that there definitely is a physical process that violates baryon and lepton conservation, and can thus result in either turning matter directly into energetic radiation or turning matter into antimatter. Unfortunately, we don't know what that process is yet (but if it was not present, the equal amounts of matter and antimatter in the early universe would have annihilated each other and we would not be here).

If you need FTL anyway, why not use the same FTL mechanism to also get you other fun stuff? Orientable wormholes give you rapid transit to other star systems, non-orientable wormholes give you bulk antimatter.

Wormholes have not been shown to be possible in real life, but they are a valid solution to Einstein's equation in general relativity so their existence cannot be ruled out a priori. I am not going to say they are probable or improbable - science doesn't work that way - but they are fun for fictional purposes. For my own setting I use wormholes extensively, both for transportation and energy
http://panoptesv.com/RPGs/Settings/V...s/TheVerge.php

Another non-physics-denies method of getting energy is to use magnetic monopoles (which are predicted by many theories but not yet observed) to catalyze baryon decay into light leptons and energetic radiation. "Matter to energy", as it were, using more popular but incorrect terminology.

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Old 08-31-2017, 08:15 PM   #37
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Default Re: [Spaceships] Anti-Lithium for Drives – Does this work?

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The terminology is something my phone likes to autocorrrect so I look like an idiot.
Gotcha. Fair 'nuff. Carry on.

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Old 09-01-2017, 09:25 AM   #38
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Default Re: [Spaceships] Anti-Lithium for Drives – Does this work?

Just a vague speculation, but anti-lithium is a solid at room temperature, while anti-hydrogen and anti-helium are gases at all but very low temperatures. That might make it easier to handle and store.

Though if you don't have a really really good way to store antimatter you probably shouldn't be messing with it at all...
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Old 09-01-2017, 03:14 PM   #39
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Default Re: [Spaceships] Anti-Lithium for Drives – Does this work?

But storing matter hydrogen is exceptionally difficult for more than short term, especially if you care about individual atoms escaping rather than tens of percents.
Antimatter hydrogen must be similarly difficult, so on a purely storage issue, nearly any other type of antimatter would be easier and safer.
But making it in such a way as to make any economical sense seems nigh impossible.
Maybe very niche small super speedy military vehicles of a very wealthy government.
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Old 09-01-2017, 03:46 PM   #40
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Default Re: [Spaceships] Anti-Lithium for Drives – Does this work?

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But storing matter hydrogen is exceptionally difficult for more than short term, especially if you care about individual atoms escaping rather than tens of percents.
Antimatter hydrogen must be similarly difficult, so on a purely storage issue, nearly any other type of antimatter would be easier and safer.
But making it in such a way as to make any economical sense seems nigh impossible.
Maybe very niche small super speedy military vehicles of a very wealthy government.
Any antimatter containment has to be using fields anyway, so I don't know if solid storage actually makes much difference.

Assuming that you can make non-orientable wormholes with throat diameters of around 100 pm you could make antilithium as long as the wormhole is open, which I think just means big initial costs in generating the required negative energy densities (much lower than the densities needed for large traversable wormholes at this scale). Once you have the wormhole all you need to do is keep it open and shoot lithium ions through.
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