Fusion vs Plasma vs Lasers

[Supertank]

Not entirely on board with "They're not supposed to be useful for ACS", either.

For armor "Heat x100" simply means AV×100 vs Heat (e.g. Lasers).

So, the noted AV for the structure and TL is the Base AV. Effective AV against specific attacks may be larger.

Note that p202 says which anti-layers works against which weapons; all of them works against Lasers.

It's a multiplier for the TL, not the AV itself (which has its own modifier).

TL-12 Polymer armor for example would have an AV of 6 (12/2), whereas Reflec would give it a Heat protection of 1,200 (12 * 100).

I think it's also not helped by the various Armor Tables not being entirely consistent (compare p. 74, 202 and 280 plus the Quick Armor Tables).

 

[acgetchell]

Physics wise, it is a lot easier to pick a wavelength that penetrates an atmosphere than it is to maintain cohesion of a plasmoid. Once it virializes (ie turns into an ideal gas) it essentially stops propagating.

The energy density of a matter beam can be greater than just photons, but the natural progression of this is the particle accelerator.

What a plasma gun adds that a laser or particle beam can’t is the ability to self-generate additional energy on route to the target. This would require containment and would be ideally done by something like a packet of magnetic monopoles (which in catalyzing baryons to anti-baryons would also add energy via annihilation).

Gamewise I’d double the damage of the plasma weapon by adding heat in addition to kinetic, and triple the damage of the fusion weapon by adding radiation or EMP (depends how the fusion reaction is tuned) in addition to heat. A nuclear damper should only remove the rads/EMP, not the kinetic and heat. (And the advanced monopole version should require a proton screen to get the same effect, being immune to a nuclear damper).

 

[acgetchell]

IMTU Meson guns don’t exist (because the Heisenberg Uncertainty Principle makes it impossible to manipulate decay of particles that precisely) but Monopole accelerators do, which ignore armor by converting it into antimatter. The inherent magnetic fields also make them easier to focus, hence they have less divergence (better range) and more effect than X-ray lasers and normal particle beams. As in Classic Traveller Meson Guns they’re the dominant spinal weapon, if you can afford/produce them.

 

[Supertank]

I would definitely give Fusion Guns their number of hits in radiation (and/or EMP) again so Nuclear Dampers make a bit more sense.
Making Plasma and Fusion slightly penetrating to reflect their kinetic portion might also do the trick, putting them halfway between Lasers and Mesons.

The rivalry between Lasers and Plasma/Fusion could also be mitigated by ruling that lasers can only be put on turret mounts (arguing that the energy-efficiency of lasers drops too fast if you scale them up).

 

[acgetchell]

Except lasers actually get better as they scale up, as their divergence is directly related to the diameter of the lens. My friend Luke Campbell, a laser physicist, worked out an absolutely terrifying X-ray laser with a few hundred AU range that required a kilometer sized FEL. It would boil away tens of meters of anything with chemical bonds per second, as well as instantly inflicting lethal radiation doses on anything biological or electronic. It was posted on AtomicRockets at one point, but he seems to have taken it down.

 

[mike wightman]

Why would a fusion gun inflict radiation hits in the first place? There is a lot of misunderstanding and semi-retcon going on here thanks to a certain rule system...
go back to the original source material:

The first light energy weapon (other than lasers), the weapon consists of a power pack carried on the firer's back, the weapon itself, and a flexible power link. The power pack powers a laser ignition system in the weapon itself which heats hydrogen fuel to a plasma state. The plasma is contained in the ignition chamber briefly and then released through a magnetically focused field along the weapon's barrel. The high initial velocity plasma jet is 2 cm in diameter but begins to dissipate immediately. Each power pack has sufficient energy to discharge 40 plasma bolts before recharging is necessary. Each pull of the trigger discharges one plasma bolt.

So basically a gauss rifle firing plasma bolts rather than a bullet - hence much higher velocities.
Now as for the fusion gun:

the FGMP-14 differs only in that it contains the plasma slightly longer until a fusion reaction begins to take place

So basically the hot hydrogen plasma begins to fuse inside the weapon and then this more energetic bolt is fired. It is likely to he hotter and faster so you are dumping more energy into the target. But no ionising radiation...

 

[acgetchell]

Because energetically favorable fusion reactions release a significant fraction of their energy as neutrons, which is to say, radiation. In a fusion reactor a lot of this is reabsorbed by the plasma, especially if large. This wouldn’t apply to a fusion bolt, ergo, lots of radiation in the form of neutrons and secondary decays.

Realistically this would also be a problem for the firer, which is why PGMPs/FGMPs should only be carried by sophonts wearing rad-hardened battle dress.

 

[mike wightman]

Exactly - the fusion reaction is inside the weapon and dealt with by the weapon. At the risk of invoking the magical damper technology to explain the containment, not to mention initiate the fusion reaction in the first place

And canonically there are plasma weapons and fusion weapons that can be carried and fired by individuals not in battle dress.

 

[acgetchell]

No, that’s not how the physics works.

A Deuterium-Tritium reaction emits 80% of its energy as fast 14MeV neutrons and operates at a temperature of 70keV, which is in the hard X-ray regime. Even with a magic weapon barrel the instant the bolt leaves the barrel the firer (and target, a few milliseconds later) is going to be inundated by neutrons and X-rays.

Canonically Traveller has meson guns, but those can’t work as described either.

 

[mike wightman]

I know how real world physics works.

Show me again where it describes the fusion reaction inside the fusion gun, it certainly doesn't mention a deuterium/tritium reaction, the fuel for the plasma/fusion guns is just regular hydrogen. This suggests the proton-proton chain reaction which means you will have a lot of gamma radiation to deal with inside the weapon.

It says is hydrogen, heated by lasers, contained a bit longer until a fusion reaction initiates inside the weapon. The plasma bolt emitted from the weapon is no longer fusing, the reactions are over. Any fusion products are dealt with within the weapon.

Yup, nuclear damper magic required here...

 

[acgetchell]

Deuterium and Tritium are isotopes of hydrogen, so the description of using hydrogen fuel is correct but imprecise.

There are no practical fusion reactions that use plain hydrogen. The proton-proton chain used by the Sun takes an average of 9 billion years to complete, so it's not a viable candidate for a weapon. Indeed, the other fusion reactions besides D-T have at least 3 orders of magnitude less energy density, so they're similarly impractical.

The nuclear damper magic has a few problems:

1. Plasma guns are TL11, Nuclear dampers are TL12.
2. Nuclear dampers are large field-emitting units. There are no descriptions of portable nuclear dampers fitting in the breach of a plasma weapon in mainstream Traveller technology descriptions.
3. Even if there were, a nuclear damper is antithetical to the goal of achieving a fusion reaction.
4. Nuclear dampers do nothing about the hard X-rays emitted by the plasma.

Finally, there's no particular reason to suppose the fusion reactions will magically stop happening in the bolt just because it's left the weapon. Indeed, it's energetically advantageous to continue the reactions as long as possible, as that gives the fusion weapon an advantage over a particle beam weapon.

In T5 terms, plasma weapons do Pen and Heat. IMTU due to physics, they also inflict Rad from hard x-rays. A fusion weapon would do more of the same, adding more Rads from neutrons.

 

[mike wightman]

Good points but here is some stuff to consider. Refining deuterium from hydrogen takes a good while, and tritium has to be manufactured, hardly just recharge at a ship or vehicle power plant is it? Fusion in Traveller has always been a bit lacking in real world physics- it would make a lot more sense if helium 3 fusion were used and then you would have a reason to build resource extraction facilities on moons and around gas giants, not just skim and dip. But that changes the setting somewhat.

There are no practical fusion reactions full stop, and there probably won't be for another 20 years . Somehow TL8 on the Traveller timeline solves the issue of making Mr Fusion. The incremental improvements you then see as TLs rise could be due to the introduction of grav compression fusion and damper catalysed fusion.

Plasma guns are TL12 for battlefield use - they are TL10 as ship weapons.
Fusion guns are TL13 for battlefield use - they are TL12 as ship weapons, while the nuclear damper screen is also a TL12 invention.

There was no mention of extreme grav focusing to make laser weapons viable at ship combat ranges until TNE, it stands to reason that the technologies that exist in the Traveller timeline have multiple applications that we can discuss, argue, or deny because someone hasn't spelled it out in a book. I prefer to think of the implications and applications rather than it just be the Star Trech tech of the week.

Nuclear dampers somehow manipulate the "strong force" - they can enhance or inhibit fission and they can enhance or inhibit fusion reactions.

There is no magic as to why the fusion reaction stops once the plasma leaves the weapon, it is the simplest of simple physics,
Once the plasma leaves the weapon it is cooling and expanding, the exact opposite of the conditions necessary for fusion.

 

[acgetchell]

I think you and I have different definitions of the word "practical".

We've already hit scientific breakeven, with more power coming out of the reaction than going in. We just haven't hit engineering or commercial breakeven, where sustained operation of the fusion plant produces power economically. D-T fusion is achievable now.

Proton-proton fusion is not achievable with our technology or extrapolations thereof.

The nice thing about D-T fusion is you can use the excess neutrons to produce more Tritium with a Lithium blanket, an easy process that happens while running the reactor. It's not particularly hard to extract Deuterium from any form of water. The energy density out of D-T is worth it: D-He3 fusion has three orders of magnitude less energy density, and you still need the Deuterium.

Cold Fusion (aka muon-catalyzed fusion) is not achievable or practical in any sense.

Again, nuclear dampers don't affect X-ray production in a plasma, which is an EM process. So the rads remain for any notional plasma/fusion weapon.

As mentioned, a fusion bolt has to be non-virialized to be viable. In other words, it's non-equilibrium, and the plasmoid is adiabatic and non-expanding for its short duration of effectiveness. Fusion processes producing neutrons would continue until the timescale where heat exchange with the environment occurs, then the whole thing falls rapidly apart, dumps its energy, and becomes ineffective. If that happens before the bolt leaves the weapon you have major issues.

If it happens after the bolt leaves the gun, the firer is subjected to neutrons as stated before. If it doesn't happen before the bolt impacts the target the target gets neutrons as well.

Fusion beams aren't a thing because a non-virial beam is known as a particle accelerator.

 

[kilemall]

If not to your taste change it.

What game effect do you want?