antimatter?

[jaf]

what do you think about antimatter engines in ksp 2 do you think they are likely

[Pthigrivi]

I do. There are a few fuel types they're keeping in their back pocket and I think it's widely suspected this is one of them. Plus like, you need that last, late carrot at the end of the tech tree that you can only unlock after you've visited another system or two. 

Edited April 10, 2022 by Pthigrivi

[Davi SDF]

I think Antimatter is very likely the end-game fuel. 

An Antimatter ship would likely be powerful and efficient enough to get you to any system in the game while carrying lots of cargo. 

However, it will probably be very hard to produce (probably the hardest), and will take a lot of energy. 

 

I'm more of a Nuclear Salt Water rocket fan though 

Edited April 10, 2022 by Davi SDF

[jaf]

11 minutes ago, Davi SDF said:

I think Antimatter is very likely the end-game fuel. 

An Antimatter ship nwould likely be powerful and efficient enough to get you to any system in the while carrying lots of cargo. 

However, it will probably be very hard to produce (probably the hardest), and will take a lot of energy. 

 

I'm more of a Nuclear Salt Water rocket fan though 

ah yeah i woas thinking the same 

Edited April 10, 2022 by jaf

[The Aziz]

There's a chance that torch drive engines would use antimatter or other very exotic material.

[Maria Sirona]

Well, if antimatter engines do exist in KSP2, that will make accurate ISV Venture Star (from Avatar) possible

[magnemoe]

15 hours ago, Pthigrivi said:

I do. There are a few fuel types they're keeping in their back pocket and I think it's widely suspected this is one of them. Plus like, you need that last, late carrot at the end of the tech tree that you can only unlock after you've visited another system or two. 

Agree, some of the reactors they have shown is gigantic, way more than needed to produce energy for an small colony even with ISRU and industry. 
And they are advanced fusion reactors, you are doing something eating loads of gigawatt, yes you have metallic hydrogen. 
But feel that is more for smaller ships and large landers, especially landers you bring to other stars but if you go up in size orion and later fusion become better options, and orion should be lower tech level than metallic hydrogen. Antimatter on the other hand is something you want a lot of to push things fast. 
 

15 hours ago, Pthigrivi said:

I do. There are a few fuel types they're keeping in their back pocket and I think it's widely suspected this is one of them. Plus like, you need that last, late carrot at the end of the tech tree that you can only unlock after you've visited another system or two. 

One game play mechanic would be that you have to recover alien technology for it. Obvious location would be on Venus if it was an super earth in another star system. 
And the ship you need to recover is huge. 
You need to colonize the system to build the city who build the launcher to take it into orbit and dock it with the return starship. 
 

[SciMan]

I don't think that recovering alien technology is going to be any part of any bit of the game in any way at all whatsoever, except perhaps as an easter egg that has minimal if any impact on overall gameplay.

And if I'm wrong, it's Metallic Hydrogen that needs alien tech to become available, not Antimatter.

Antimatter is an entirely easier problem to solve than the stable storage of metallic hydrogen at low pressures and probably high temperatures (which is exactly the kind of situation that makes metallic hydrogen as we know it decompose into regular hydrogen, with a tremendous amount of energy released in the process).

Antimatter on the other hand, we already know how to create and store and use small quantities of antimatter IRL. It's just a matter of scaling up to mass production.
And for mass production of antimatter, there's no location in a given solar system that's better than a low orbit around the brightest star of that solar system, because the energy needs are SO tremendous that no feasible reactor (or array of reactors that wouldn't melt your computer) is capable of supplying enough power to result in the ability to create antimatter at a fast enough rate.
Antimatter is NOT an energy SOURCE, nor is is a FUEL. It is an energy STORAGE method, just like the proposed-but-entirely-impractical "Hydrogen Economy" that bases it's hydrogen production on electrolysis of seawater (so, where you gonna get all that energy from, huh? That question makes the "hydrogen economy" proposal fall apart, to my knowledge).

So, low orbit around a very bright star. You bet you're gonna have heat problems.
But what is the machine you dump all that power into anyway? Maybe it's not an "easy" answer in the "now I have to build this thing" way, but it's an extremely simple concept.
The thing that makes antimatter is a particle accelerator. And it does so at quite low efficiency, which is why you have to dump so much energy into it to get even a tiny (but usable) amount of antimatter out of it.

The energy problem of antimatter is so much of a problem that there's an entire video game dedicated to it. That game is called Dyson Sphere Program, which is a game similar to Factorio, but set on an interstellar scale. However, because it's a game, they have sacrificed much realism in the pursuit of good gameplay. In that game, the amount of energy you get out of the fuel for an antimatter power reactor is exactly the same as the amount of energy your dyson sphere produced in order to manufacture antimatter in the first place.
In real life, it is hard to over-state how unfavorable the proportions are.
With particle accelerators that are as efficient as the best we can make IRL, when creating antimatter something like 99.9% of the energy you put into the particle beams is re-emitted as waste heat dumped into the superconducting magnet cooling systems (which then takes even more energy to power the cryo-coolers removing that energy from those superconducting magnet's cooling baths of cryogenic liquid lightweight gases like liquid helium).

But how big are these particle accelerators going to be, since we're in orbit and gravity doesn't have much of an effect? GIGANTIC! You know how CERN's particle accelerator main ring is around 30km in diameter? The ones that would be in low orbit around the star would probably be on order of 1000 km in diameter. And despite being in the "vacuum" of space, you'll still need to have an evacuated beam tube for those particles to pass thru, with another set of either acceleration or steering magnet coils each say 10km of that tube's length. And now remember that despite being so close to the star, you're going to need to keep those superconducting magnets cold enough that they remain superconducting. The best "high temperature" superconductors we have today still need a bath of at least Liquid Nitrogen to become superconductors, and while in Earth Orbit Liquid Nitrogen isn't that hard to keep liquid (it's a lot easier than keeping LH2 liquid!), it's still gonna be plenty hard that close to the star.
But the thing that dwarfs the particle accelerator ring itself is gonna be the solar arrays. These are going to be SO MASSIVE that the whole structure will likely be able to support itself against the gravity of the star using just solar wind and solar radiation pressures, or at least it will have to have a guidance system on it that actively compensates for the effects of those forces, because those forces will be massive.

But hey if you want a ready large supply of Antimatter, that's what you have to do to get it.

Now as far as how to use it, you'd probably have 2 or 3 kinds of drives that use Antimatter:

1. Solid core Antimatter engine, useful for landers and surface-to-orbit uses:
Runs on Antimatter for fuel (energy source) and Hydrogen (or practically any other liquid resource, with varying specific impulse and thrust depending on which one) as reaction mass, with the antimatter beam being aimed at say a solid block of Tungsten in the "reaction chamber" of the engine. This is basically an antimatter-thermal engine. Antimatter reacts with matter, that makes more matter get hot, that hot matter heats the reaction mass, the reaction mass is exhausted out a rocket nozzle. Pretty simple to make, pretty simple to control.
This is a propulsion system that is most similar to chemical rockets or the best solid-core fission nuclear thermal rockets. Specific impulse is good enough to get you anywhere in the solar system, but it's gonna take a nice long series of gravity assists and/or a potentialy-even-longer direct Hohmann transfer to get you there. No brachistrchone trajectories here, you're stuck on the "slow boat", and normal orbital dynamics still very much dictates just exactly where you can go. However, extremely high thrusts are possible with this system, so it's ideal for getting things into orbit from the surface, or landing back on the surface from orbit.

2. Plasma-core Antimatter engine, useful for travel within a solar system. Just like the Solid core one, it takes Antimatter for fuel (energy source), and Hydrogen (or any other liquid resource) as reaction mass. However, in this design there is no intervening block of Tungsten or other high-melting-point material. Instead, the antimatter beam is allowed to directly react with the reaction mass, and the flow of antimatter (and therefore power output) is increased to the point that the reaction mass in the reaction chamber is heated to Plasma temperatures. Magnetic fields are used to create both the reaction chamber and the exhaust nozzle (similar to how the KSP devs have made their Metallic Hydrogen engines work, but with real physics behind it instead of whatever that Metallic Hydrogen stuff is supposed to be). This too is basically a thermal rocket, however because the temperatures are now "plasma hot" rather than "glowing block of Tungsten" hot, the specific impulse and thrust are much higher for the same reaction mass flow rate.
As far as "torch drives" go, this is very much one of those.
While you "could" use this for a surface-to-orbit or a landing engine, the problem is that you'd glass the launch/landing site with your exhaust, and potentially destroy your own ship with the energy and debris reflected from and kicked up from the surface, therefore there would likely be quite a lot of people getting very upset at you if you did this, potentially including yourself (and I mean "Glass" as in Halo or WH40K type "glassing" of planets, "Exterminatus" style).
What it's meant for is use between the planets, and you can for sure do brachistrchone trajectories, in fact with a drive with this much performance you can pretty much ignore the rules of orbital dynamics, since you have so much thrust and specific impulse available.
Expect high thrust, high specific impulse, and long burn times without burning thru your entire propellant tank, but not high enough specific impulse to go truly interstellar.

3. Beam-core Antimatter engine, useful for travel between the stars. Also known as a "pion rocket" or potentially "mass-energy conversion drive".
If we only get ONE antimatter drive in KSP 2, expect it to be this one.
This is the engine you want to use to go to other stars. This engine is also the first antimatter engine that can be classified as "low thrust", but only in relation to the other two engines. Of interstellar drives, this is probably the one with the highest power output (and therefore highest thrust and specific impulse). After all, if you don't consider the efficiencies of actually MAKING the dang antimatter, then antimatter drives are pretty dang efficient. The only reason they output so much waste heat is that 0.5% of 1 Terawatt is still a LOT of heat to get rid of in the vacuum of space
This drive reacts equal parts Hydrogen and Anti-Hydrogen, directed at each other as a pair of colliding low-energy particle beams that intersect directly inside a stupendously large magnetic nozzle (it needs to be large, because the direct product of the reaction of hydrogen and anti-hydrogen is a bunch of Pions and Gamma rays, both of which are extremely hard to direct with a magnetic field. However, pions are short-lived, only traveling a few 10's or 100's of meters before they decay into charged particles which can "easily" be directed with a magnetic field).
Now, as for specific impulse, this drive can't be beat. It's literally the highest possible specific impulse for any engine that isn't just a photon rocket (which would have an exhaust velocity of the speed of light, and since matter can't travel at the speed of light the antimatter drive's specific impulse will be lower, but not by much).
Thrust, not so much. Because of the waste heat problems of most antimatter drives, but especially a Beam-Core antimatter drive, what power you CAN use is directed mostly at accelerating small quantities of matter to nearly the speed of light, which is what you need when going interstellar, but not useful for travel inside a solar system, and you can just forget about trying to launch or land with it.
However, if you DO accidentally direct the exhaust at the surface of a planet or moon, BAD THINGS HAPPEN. This thing is basically a laser-beam of highly deadly radiation, since guess what hydrogen nuclei traveling at near the speed of light are? They're cosmic rays. And since they're going so fast, it's really hard to shield against this kind of radiation.
Lead won't save you this time. Neither will tungsten. Best bet is to be on the other side of the planet, that's pretty much what it takes. As for what happens on the near-side, it depends on just how close the beam-core antimatter drive is when the exhaust hits the planet, but the least that would happen is the creation of a glowing crater along with the stripping-away of the atmosphere within the area of the exhaust beam (and "beam" is the right word here, "plume" assumes that it has sufficient time to spread out a lot, which is not what happens with the exhaust of a beam-core antimatter drive).
So when "playing" with any interstellar-capable drive system, be responsible, and remember the Kzinti Lesson:
"Any spacecraft drive system sufficiently powerful to be interesting is also sufficiently powerful to be easily converted to use as a weapon".

EDIT (again):

Also, I suppose for the sake of completeness, you would likely have a very powerful antimatter power reactor, which allows you to have supply missions supply power to places that don't have a ready supply of sunlight, fusion fuels, or fissile isotopes (like space stations for example). Antimatter being what it is, this would have to be the most energy-dense "power matter" type resource in the game (as in joules out per kilogram in), with the antimatter reactors always being smaller and lighter and creating less radiation (aside from Gamma, which can be shielded with a player-supplied Tungsten shadow shield) than any other kind of power reactor for the same power output.

Edited April 10, 2022 by SciMan
Accidentally posted part-way thru composing my post.

[SciMan]

For "non-end-game" uses of Antimatter, you could also have the various antimatter-initiated pulse drives, which are like miniature Orion drives that don't actually need to carry anything that by itself can be used as a nuclear weapon.

The principle is that antimatter triggers a Fission detonation, Fusion detonation, or to reduce the amount of antimatter (or increase drive power) even further, a three-stage approach, with a small amount of antimatter triggering a more conventional thermonuclear device (fission-triggered-fusion, with potentially another fission stage on top, like the Tsar Bomb device but minus the high explosives).

All three options are well explored over on the Atomic Rockets website, and despite doing those engines from memory, I'm pretty sure that's where I got my info from.
However, for the PRODUCTION of antimatter, I pulled my info from the Encyclopedia Galactica, specifically THIS page