Dilithium crystal fusion impulse engine in development | Hacker News Reader

Dilithium crystal fusion impulse engine in development

news.cnet.com

38 pointsaneth49 comments

The other article has a nonzero information content, for a change:

http://txchnologist.com/post/32463368168/channeling-star-tre...

Summary: it's nuclear pulse propulsion (riding the shock wave of a nuclear explosion). Small nuclear explosions in this concept: they hope to create small (~1 ton TNT eq.) pure-fusion explosions using nanosecond bursts of extremely powerful electric currents (plasma Z-pinch). Basically, it's the same problem as fusion power plants based on "inertial confinement" (euphemism for "explosion").

Lithium is a progenitor of tritium. This is common D+T fusion.

This concept is not remotely close to practicality. Which is why the reported goal ("a mind-bending 62,600 mph") is bizarre; it's only a small factor better than chemical rockets. It's just as bad as e.g. nuclear thermal propulsion, which was designed and built 40 years ago. So I really don't see the point.

The fuel has a much greater energy density than chemical rockets, making longer distances practical, and the process is safer than nuclear fission.

link to oldskool version > http://en.wikipedia.org/wiki/Nuclear_pulse_propulsion

That's my complaint, it doesn't have much greater energy density, or more precisely it's not usefully translated to momentum. The speed target in the article is extremely low ("62,600 mph") -- only a small factor higher then what chemical rockets achieve, and comparable (as I mentioned) to nuclear thermal rockets. (It looks like they edited their article to mention NTRs.) They have extremely energetic fuel, but they don't get any meaningful specific impulse out of it. Maybe they don't easily extract momentum from high-energy radiation. Or maybe they lose too much mass to radiation damage or vaporization ("ablative shield") -- their mass consumption could be dominated by shielding, not fuel.

Their ultimate goal is to develop a nuclear fusion propulsion system by 2030 that can spirit spacecraft from Earth to Mars in around three months—about twice as fast as researchers think they could go with a nuclear fission engine, another scheme that is being investigated but has not yet been built.

The speed doesn't tell us the whole story. If a chemical rocket can only practically carry enough fuel to burn a couple times on a one-way trip to Mars, while this has fuel to burn for maneuvers and a return journey, then it is a big advancement. We weren't given enough info, so it's a bit early to discount it as worthless.

Dilithium crystals weren't used in the impulse drive though, they're used to catalyse the matter/antimatter reaction through their crystal structure.

Also it seems to be fusion pulse propulsion. Pretty good for going fast.

Original article:

http://txchnologist.com/post/32463368168/channeling-star-tre...

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