Fusion Thrusters For Space Travel 192
kgeiger writes "John J. Chapman, a physicist and electronics engineer at NASA's Langley Research Center, envisions a laser-pumped fusion drive. Chapman estimates the drive can produce thrust 40 times more efficiently than existing ion engines such as those on the Dawn mission now exploring the asteroid belt."
It seems more fission than fusion (Score:5, Informative)
The reaction is
1H + 11B -> 12C -> 4He + 8Be -> 4He + 4He + 4He
so there are more output nuclei than input.
However, I suppose it is true that all of the energy is coming from fusion, as 12C -> 4He + 4He + 4He is exothermic. (The reverse reaction is an energy source for stars under some circumstances.)
12C is normally stable, so for this reaction to go as stated the nucleus must be created in some suitable excited state.
Yes, probably. (Score:2, Informative)
On Earth, we want to use fusion to power homes, ground vehicles, etc. However, the amount of work and energy we put into fusion gives us much less gain when compared to the amount of energy we can extract with fission, wind, solar, waves, geothermal, oil and coal. We attempt this with deuterium and tritium to produce neutrons. As the article puts it; [To make use of neutrons, "you need an absorbing wall that converts the kinetic energy of the particles to thermal energy," he says. "In effect, all you’ve got is a fancy heat engine, with all its resultant losses and limitations."]
According to the article, he's suggesting using Aneutronic fusion using Boron-11 as a fuel source to produce alpha particles (Helium-4 and Beryllium) via a laser which will yield 60% - 70% efficiency and 100,000 particles with each pulse. Boron will yield 300 MW of power per 11 mg, whereas Helium-3 isotopes as a fuel source would yield 493 MW in equal quantities. However, Helium-3 is scarce whereas Boron is not so it makes more sense to go with Boron instead. He claims it would be 40% more efficient than current deep space ion engines.
Keep in mind, that these engines have to run for long periods of time over great distances. They have all the time in the world to increase their acceleration to their mass potential. It's Hare vs the Tortoise, on Earth we need our power *right now* in large quantities and quickly. Whereas, in space you have patience because the distances are already so vast, you don't have much room to store fuel, and there is little or no friction so you can take your time building up speed.
Hope that helped you make heads or tails of this.
Re:research! (Score:3, Informative)
1. Spacex's rockets were based on a concept engine called Fastrac, killed in 2001. Spacex have scaled up the thrust by a factor of four and the ISP from 260 seconds to 300.
2. Spacex's aluminium-lithium friction stir welded tanks were developed by LockMart for the SLWT first flown by the space shuttle in 1998. X-33 used experimental composite tanks and ignored the lighter FSW technology because it wasn't "Space Age" enough. This is why X-33 failed.
3. Transhab was not killed by the 1996 congress. Transhab didn't exist in 1996. Transhab was killed by House Resolution 1654 in 2000 to prevent NASA from even thinking about Mars. If NASA had called it an Orbhab instead of a Transhab then it wouldn't have been killed.
4. Nope.
5. VASIMR barely existed on paper in 1996. It didn't exist as a national program and there was nothing for congress to kill.