Thread: Interstellar Medium

http://en.wikipedia.org/wiki/Interstellar_medium

Is it possible to use the hydrogen to fuel a fusion reactor on board a space ship? The faster you go, the more energy per second you take in to fuel your acceleration. This could allow us to reach extremely high speeds, fractions the speed of light. At least this would make Sirius reachable if we cannot figure out how to make a warp drive in the next 40 years.

http://en.wikipedia.org/wiki/Bussard_ramjet

Originally Posted by Cold Fusion

http://en.wikipedia.org/wiki/Interstellar_medium

Is it possible to use the hydrogen to fuel a fusion reactor on board a space ship? The faster you go, the more energy per second you take in to fuel your acceleration. This could allow us to reach extremely high speeds, fractions the speed of light. At least this would make Sirius reachable if we cannot figure out how to make a warp drive in the next 40 years.

This is ouit of the question. You are talking about 'cold' fusion that is not possible.

I think only the stars can create fusion IMO.

Cosmo

I suppose this is a French star...
http://www.flickr.com/photos/7969902@N07/511234695/

We can easily fuse hydrogen on earth. In fact, I believe it was a 15 year old a little while ago that made his own vacuum fusion device. It took him two years and a couple thousand dollars.

Its not cold fusion; the temperatures would be very high, as is needed to fuse hydrogen.

Originally Posted by Cold Fusion

We can easily fuse hydrogen on earth. In fact, I believe it was a 15 year old a little while ago that made his own vacuum fusion device. It took him two years and a couple thousand dollars.

Its not cold fusion; the temperatures would be very high, as is needed to fuse hydrogen.

Such devices consume more energy than is produced by the fusion. They are useful as a source of neutrons, but that is about it.

A fusion propulsion system would need to be able to net more energy from the fusion than is needed to operate the system. It is reaching or exceeding this break-even point which has proven elusive.

Originally Posted by Arch2008

I suppose this is a French star...
http://www.flickr.com/photos/7969902@N07/511234695/

I saw the picture of that bomb but the question is, was it a fusion or a fission bomb?

Fission bombs are man made. The US fusion bomb required a fission stage after it was triggered by an ordinary chemical bomb IMO.

Cosmo

Thermonuclear means fusion.

I believe that the ramjet uses fusion for propulsion, not power. So it doesn't need to 'break even'.

Originally Posted by Arch2008

Thermonuclear means fusion.

I believe that the ramjet uses fusion for propulsion, not power. So it doesn't need to 'break even'.

That statement makes no sense. In order to propel the ship, the ship must expel reaction mass at high speeds. To get that reaction mass to high speed you must supply energy. Thus there must be excess energy left over after the fusion process in order for there to be any to propel the ship.

One of the requirements of fusion propulsion is that it be self sustaining. That the fusion process produces enough energy to maintain itself, and have an excess for propulsion.

http://en.wikipedia.org/wiki/Fusion_rocket

“An attractive possibility is to simply direct the exhaust of fusion product out the back of the rocket to provide thrust without the intermediate production of electricity.”

Does this make sense to you now?

Originally Posted by Arch2008

http://en.wikipedia.org/wiki/Fusion_rocket

“An attractive possibility is to simply direct the exhaust of fusion product out the back of the rocket to provide thrust without the intermediate production of electricity.”

Does this make sense to you now?

I know how a fusion rocket should work. The point is that the exhaust gases get their energy from the fusion process, and at present, we have not yet found a way to maintain such a controlled fusion reaction that does not take more energy than what is released. (We are not talking about the uncontrolled fusion reaction of a nuclear explosion which would not work for a Bussard Ramjet).

And if you had a compact and efficient enough energy source other than fusion on board that allowed you to maintain the controlled fusion reaction, you would just use that for your propulsion system.

The point being that we do not yet know how to make a fusion rocket work. If we did, we wouldn't be fooling around with ion propulsion or VASIMRs.

“To produce positive thrust, the fusion reactor must be capable of producing fusion without significantly slowing the incident ions down (relative to the ship).”

It’s a ramjet, not a power source. A fusion power source has to contain the explosion and then use less energy to contain it than is produced so that it breaks even. A ramjet does not have to contain the explosion any more than a current jet engine would have to contain the explosion of JP4.
That is the point.

Fusion needs too much fuel and the further you get from the sun, the less there is of it. Under ideal conditions, a ram jet is only good for a tenth light speed.

I would think you'd have to use nuclear binding force energy holding together elements like iron and lead, at least in tandem, to provide much of the power. A hybrid space craft.