Fusion Rocket Could Take Us To Mars 171
New submitter imikem writes "University of Washington researchers and scientists at a Redmond-based space-propulsion company are building components of a fusion-powered rocket aimed to clear many of the hurdles that block deep space travel, including long times in transit, exorbitant costs and health risks. 'Using existing rocket fuels, it's nearly impossible for humans to explore much beyond Earth,' said lead researcher John Slough, a UW research associate professor of aeronautics and astronautics. 'We are hoping to give us a much more powerful source of energy in space that could eventually lead to making interplanetary travel commonplace.' 'The research team has developed a type of plasma that is encased in its own magnetic field. Nuclear fusion occurs when this plasma is compressed to high pressure with a magnetic field. The team has successfully tested this technique in the lab. Only a small amount of fusion is needed to power a rocket – a small grain of sand of this material has the same energy content as 1 gallon of rocket fuel.'"
Re:Yuh huh (Score:5, Informative)
I don't think practical fusion technologies are as far away as you're acting like they are. If you've been following fusion news, there are several projects that are getting pretty close to scientific net+(my favorite is the Focus Fusion experiment).
Re:nuclear fusion? (Score:5, Informative)
High-speed ions would actually be easier and more efficient to use for generating electricity than conventional thermal energy. You set up an opposing electric field with a voltage that corresponds to the ions' energy in MeV, and capture them once they've slowed down. This creates a direct electric current at that high voltage, without the need for Carnot cycles, steam equipment, heat exchangers, etc.
One of the attractions of aneutronic fusion is that most of the energy is released in the form of charged ions that can be harnessed in this way.
Re:Yuh huh (Score:3, Informative)
The devices we call 'hydrogen bombs' are not pure fusion explosives. They are more correctly known as 'hydrogen-boosted fission' devices. The hydrogen fusion is used to provide more neutrons to sustain the fission reaction, but in most cases the majority of the energy still comes from fission.
(At least, that's my understanding.)
Correct. Fission --> Fusion --> Lots More Fission --> Very Big Kaboom
Although the energy density of hydrogen fusion is greater than that of Uranium/Plutonium fission, the energy of individual fusion reactions are generally much less energetic than individual fission ones. H-bombs are crazy because fusion produces high-energy neutrons (and lots of 'em), which are sufficient to cause fission in normally non-fissile U238. So, they jacket the fusion part with cheap U238, which is useful as a tamper for slow neutrons until the fusion fuel ignites (by way of energy from a separate, fission primary), after which the cheap U238 is fuel for boosting the yield off the charts.
Re:Yuh huh (Score:4, Informative)
All of the fusion projects that I'm aware of are not only heavy, they're also delicate, and require lots of skilled technical attention.
I'd say we're *at least* two decades from a fusion engine that's practical in a spaceship. Three or four wouldn't surprise me. And I also wouldn't be totally surprised if it is one of those things that can just never be made practical (though I'd be very disappoiinted).
For that matter, while several of the fusion projects appear to be near the technical "break even" point, I can't think of one of them that's even approaching the economic break even point. Even fission is a bit dubious about that, when you count in all if the expenses. (E.g., government providing "insurance" against massive problems [in the form of saying "you won't be held liable"], and what to do with spent reactors and fuel.) That said, one mussn't forget that coal also gets massive subsidies, if only in the form of permission to engage in environmental degradation and pollution.
Note that all mining is environmentally destructive, and it is rare for the costs of that destructuion to be included in the cost of the products of the mining. So it's quite difficult to come to a rational balance of which technology is more expensive. Fusion has the problem that it's less dependant on mining, so it doesn't get the benefit of free pollution of the environment. This makes it more difficult for it to compete with established technologies. But it's not even nearly ready yet anyway. None of the existing projects have passed the technological break even point, which is a lot easier than the economic break even point.
Re:Yuh huh (Score:4, Informative)
Think of it as a super high density fuel that just takes a lot of energy on the ground to process.
It doesn't even have to be exothermic (net energy gain) on the spacecraft, without considering any ground processing. In other words, it's perfectly fine if, for each kWh of electric energy you supply into the engine, you only get e.g. 0.4 kWh of kinetic energy of exhaust gases (plasma) coming out of the engine's nozzle. What's much more important is that the engine puts that 0.4 kWh into a very tiny amount of plasma, so that the plasma's velocity is very high (for a given amount of kinetic energy, the velocity is proportional to the reciprocal of the square root of the mass). That velocity is the "specific impulse" of the engine, and it determines how much fuel mass you need to achieve a given delta-v of the vehicle.