

Dilithium crystal fusion impulse engine in development - aneth4
http://news.cnet.com/8301-17938_105-57523867-1/star-trek-fusion-impulse-engine-in-the-works/

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

[http://txchnologist.com/post/32463368168/channeling-star-
tre...](http://txchnologist.com/post/32463368168/channeling-star-trek-
researchers-to-begin-fusion)

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.

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

~~~
uvdiv
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._

~~~
WiseWeasel
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.

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sitharus
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.

------
Hoff
Original article:

[http://txchnologist.com/post/32463368168/channeling-star-
tre...](http://txchnologist.com/post/32463368168/channeling-star-trek-
researchers-to-begin-fusion)

