Propulsion

So, a few words on my propulsion research.

I don’t really think this is everything possible said on the subject, likely I’m only glancing at the tip of the iceberg. However, I really doubt I should ever go into too much detail on mechanics and mathematics behind the actual function of whatever propulsion method I choose to use (the really nitpicky technical details are something I quite often just glace through when reading Sci-Fi) ’cause not that many people would understand them or appreciate them.

You know, all that stuff is just a bit heavy on the brain. And I’m sure not just my brain. Boring people to death with technical details is not really what I’m after with this story, although I think I should drop the occasional line about the matter that would actually be true and/or plausible.

So, on to the possible means of moving through space!

Nuclear fission

Ion engine

With this engine, electric power is used to create charged particles of the fuel. The fuel used would usually be Xenon. The charged particles are then accelerated to extremely high velocities.

It’s a rather low force solution, but possible speed is only limited by the power available. What would be used to supply that power is bit of a mystery to me at this point.

The down-side of this solution is that it’s only suitable for interplanetary travel. Perhaps it is suitable for use in some of the smaller spacecraft used after human race has conquered far away systems. Not to be used in my interstellar (intergalactic?) ship.

Fission-electric

This is a very long-lasting engine type at low thrust.

However, it is limited to deep-space operations as it would not be able to leave atmosphere. It would stay in-orbit and landing to planetary surface should be done with smaller, higher-thrust vessels.

Also, it’s not suitable for interstellar travel.

Fission-fragment

Creates high-speed jets of nuclear fragment ejected at about 12000 km/s. In order to reach maximum velocity the reaction mass should consist of fission products.

This type uses a lot of fuel and therefore isn’t all that cost-effective for any long journey (the fuel I assume would take quite some room).

Nuclear pulse

Driven forward by series of nuclear explosions.With fusion-antimatter catalyst this one could reach 10% of the speed of light. If instead a pure matter-antimatter annihilation rockets were used, this could theoretically achieve 50-80% of the speed of light.

The problem with this system would be slowing down: either about 50% of the fuel would need to be saved for slowing down or alternate solutions need to be used. For this purpose, a magnetic sail has been proposed.

Project Daedalus from 1970s took the idea a bit further. The plan was to use externally triggered inertial confinement fusion. What this means is that fusion explosions are produces via compressing fusion fuel pellets with electron beams. Also laser, ion beams, neutral particle beams and hyperkinetic projectiles have been suggested in place of electron beams.

Nuclear fusion rockets

Can reach up to 10% of the speed of light. With enough fusion stages could reach close to the speed of light.

Antimatter rockets

If energy resources and efficient production methods to make antimatter in quantities needed are found and the antimatter could be stored safely, this propulsion method could theoretically reach speeds of several tens of percents of that of light.

So, the problem really is that 1) we don’t have the energy resources to make enough antimatter, 2) we can’t do it efficiently currently even if we had the energy and 3) we don’t know how to store it.

Then there’s the fact that at the annihilation of antimatter quite a bit of energy is lost to gamma radiation and neutrinos. Just because of the radiation some sort of shielding methods would be needed to protect passengers and cargo.

As far as I gather this would still be a better choice (if we forget the radiation) as about 40% of mc² would be available. With nuclear fusion it’s only 1%. If the loss of fuel to radiation and neutrinos could be prevented the number could be higher.

Speculated methods

Just a list. Might revise to expand on these later.

  • quark matter
  • Hawking radiation rockets
  • faster-than-light travel
  • Alcubierre drive

So, there are quite a few choices. I can’t lie and say I’d understand much of what I’ve read on the matter and therefore decided to focus on the parts I’m actually sure I got (or think I understood, whichever is closer).

Should have paid more attention in my physiscs classes…

 

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