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You are implying ion drives I assume. Ion Drives work by accelerating particles to _really_ fast speeds (like fractions of light-speed) and use that to generate

You are implying ion drives I assume. Ion Drives work by accelerating particles to _really_ fast speeds (like fractions of light-speed) and use that to generate thrust. Meaning it requires almost no "fuel" but requires A LOT of power for the amount of thrust generated. A fusion power generator coupled with ion drives could potentially generate a lot of thrust for little mass since the fusion fuel also has very little mass. https://en.wikipedia.org/wiki/Ion_thruster https://en.wikipedia.org/wiki/Ion_thruster

aqme28 2y ago
He might be talking about a "direct fusion drive," which is not an ion drive. It's basically a magnetic-confinement device but you leave part open in such a way that fusion products exit to produce thrust.
- short_sells_poo 2y ago
  In fact I meant it in a general sense, and both ion drive and a more classic confinement engine like design that expels the fusion products. I don't know enough about the intricacies to argue for one vs the other, but fusion fuel is the most energy dense fuel we have within reach, by a huge margin. The variable then becomes the mass of the engine (and supporting plumbing), but we have control over this. Can we shrink a fusion reactor small enough to make the rocket as a whole feasible? I don't know. My hope is that for space travel, we can make certain tradeoffs that are not feasible on Earth - e.g. expelling radioactive waste products into the environment. A rocket engine doesn't need to be all that efficient at generating electricity either, it mostly needs to be efficient for propulsion, which might make it's design much simpler.
- Symmetry 2y ago
  For example, here's a fission-fusion one that looks like it only needs engineering to be workable: https://www.nasa.gov/general/pulsed-fission-fusion-puff-propulsion-system/ https://www.nasa.gov/general/pulsed-fission-fusion-puff-prop...
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pfdietz 2y ago
> Ion Drives work by accelerating particles to _really_ fast speeds (like fractions of light-speed) Sure, if the fraction is 1/10000. Very high exhaust velocity is not optimal since it increases the power needed per unit of thrust.

aqme28 2y ago

He might be talking about a "direct fusion drive," which is not an ion drive. It's basically a magnetic-confinement device but you leave part open in such a way that fusion products exit to produce thrust.

short_sells_poo 2y ago
In fact I meant it in a general sense, and both ion drive and a more classic confinement engine like design that expels the fusion products. I don't know enough about the intricacies to argue for one vs the other, but fusion fuel is the most energy dense fuel we have within reach, by a huge margin. The variable then becomes the mass of the engine (and supporting plumbing), but we have control over this. Can we shrink a fusion reactor small enough to make the rocket as a whole feasible? I don't know. My hope is that for space travel, we can make certain tradeoffs that are not feasible on Earth - e.g. expelling radioactive waste products into the environment. A rocket engine doesn't need to be all that efficient at generating electricity either, it mostly needs to be efficient for propulsion, which might make it's design much simpler.
Symmetry 2y ago
For example, here's a fission-fusion one that looks like it only needs engineering to be workable: https://www.nasa.gov/general/pulsed-fission-fusion-puff-propulsion-system/ https://www.nasa.gov/general/pulsed-fission-fusion-puff-prop...

deleted 2y ago

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pfdietz 2y ago

> Ion Drives work by accelerating particles to _really_ fast speeds (like fractions of light-speed) Sure, if the fraction is 1/10000. Very high exhaust velocity is not optimal since it increases the power needed per unit of thrust.