If I cook it on the reactor, is it fusion cuisine?

[Umbran]

understood. So, back to the solar sail, then. How would it be able to work with the above limitation?

Well, a solar sail takes photons from a very large area, and bounces them off it's reflective surface. In bouncing off, the photons exert a force on the sail.

The sail is *huge*. The NASA Sunjammer, which was cancelled just earlier this month, would have had a sail area of about 13,000 square feet. It would have produced thrust about equivalent to the weight of a packet of sugar.

The more you concentrate the incoming light/particles, the smaller the sail could be. But, then, the sail has to be tough. We aren't talking about light, now - the fusion produces helium ions and neutrons with high energy. We can't do much with the neutrons - the're not charged, so we don't have a handle on them, and cannot easily collimate them. That leaves us with the helium nucleii. - we are talking about charged particles moving close to the speed of light. Individually, not a big deal. But, in numbers and energy enough to turn a 100 MW generator? We don't have the materials to take that hit in a small space.

But.. to take the concept.... On a smaller scale - fire the beam down a long tunnel. The tunnel is in hard vacuum, so you aren't worried about air getting in the way. The tunnel is long enough that the beam has spread out and isn't too harsh. Put your particle-turbine blades down at the end of the tunnel. You still have to deal with the fact that the things are charged - that'll cause damage long term, so maybe you have to charge the blades with electrons, which is annoying.

That's why I'm thinking something more like a reverse tokamak.

 

[Scott DeWar]

I see your points. It is actually quite clear!

 

[Scott DeWar]

So, back to square one. Are you suggesting this beam of negatively charged Helium ions, super hot and traveling at, say, .9 C (provided it is in a hard vacuum) moving through a magnetic field will generate an electrical charge?

 

[Umbran]

So, back to square one. Are you suggesting this beam of negatively charged Helium ions, super hot and traveling at, say, .9 C (provided it is in a hard vacuum) moving through a magnetic field will generate an electrical charge?

It will not generate an electrical charge. It can induce current.

The beam is of positively charged particles. That is *itself* a current - charge is going from point A to point B. You know what we call a thing that takes a high-voltage current in one place, and turns it into a low-voltage current in another place? A transformer. Charges moving in one wire create a magnetic field. We use that field to move charges in another wire, a process we call "inducing current". The energy from one wire moves into the other wire, by way of magnetic fields.

The only difference is that one of the currents is actually a stream of free charged particles. Not a *small* difference, but... well, I'll be interested in seeing if I am right.

 

[Scott DeWar]

So the stream of charged particles can act as the primary of a transformer? I thought that it had to be a changing electrical field, 'alternating current'. it seems that the stream is a Direct current.

addm: I remember that inductive coils resist changing current, giving DC a more steady current, or resisting a changing current causing a field of magnetic flux that is then induced as a current in a secondary coil, Right?

 

[Umbran]

So the stream of charged particles can act as the primary of a transformer? I thought that it had to be a changing electrical field, 'alternating current'. it seems that the stream is a Direct current.

Well, we are now digging into engineering details. The basic fact is that we have energetic particles with a handle (their charge). There's several ways we can be clever and get at their energy.

For example - it is only a steady, direct current if the fusion source is constant. If, instead, we pulse that source* (say, as some useful multiple of 60 cycles per second), then we have the basis for an alternating current.





*Some forms of fusion are done with a fuel pellet you shoot with big frikkin' lasers until the pellet is hot enough to undergo fusion. If you pulse those lasers, you may be all set!

 

[Scott DeWar]

For example - it is only a steady, direct current if the fusion source is constant. If, instead, we pulse that source* (say, as some useful multiple of 60 cycles per second), then we have the basis for an alternating current.

I was like DUH! of course. pulse dc works just fine with a transformer! That is interesting about the laser heating of a fuel pellet. Never even heard of that. Of course you ca pulse a laser, so that is a piece of cake to do. clever.