[skew]

"kinetic energy" means nothing alone, thrust and specific impulse are better metrics to look at. Doing a lot better than ion thrusters at either without being too much worse in the other and energy efficiency would be interesting.

However, the article quotes an exhaust velocity of 30km/s (or ISP of 3000s), and using 200kW doesn't leave much room to beat http://en.wikipedia.org/wiki/HiPEP on thrust without counting on net energy gain. The linked slides also claim net energy gain.

[mchouza]

Yes, I agree. My point was that you cannot do substantially better than ion engines without having energy gain and, in fact, you are probably going to do much worse due to the weight of the "fusion hardware".

I'm quite optimistic about magnetized inertial fusion. But the idea of doing the job much better than the Z-machine, with something lightweight enough to carry into space and in less than 10 years seems to me... unlikely, to put it mildly.

[schiffern]

>in fact, you are probably going to do much worse due to the weight of the "fusion hardware".

Ion engines have weight, too. What leads you to believe that the fusion hardware will be heavier?

[mchouza]

In the short run:

- Ion thrusters are way simpler and they are trying to do something that is much easier.

- Ion thrusters are relatively mature, working "fusors" don't exist.

- Existing machines that are trying to get fusion breakeven are building-sized.

- Trying to start a fusion reaction is hard, it only makes sense if you get a commensurate result (energy gain).

In the long run, I'm very optimistic about fusion.