[Jweb_Guru]

The problem isn't just sending something (or someone) to another star (though it would take far longer than 1400 years with any currently plausible technology and energy expenditure). It's sending something accurately to another star (can't use too much energy adjusting course, since fractional additions to weight require tremendously more power) with a payload that's still operational by the time it gets there. Think about the myriad problems NASA probes have after just a relative handful of years or so in space.

Also worth noting is that all deep space missions thus far have had to rely on nuclear power, usually using 238-Pu with a half life of less than 90 years. With such technology, a well-shielded, self-correcting computer system traveling at reasonable speeds and energies could not survive too long because it would simply run out of power. AFAIK, workarounds for this rely on exotic power sources and unproven physics--it's entirely possible that these don't pan out, and this provides our "Great Filter."

[stcredzero]

There's been some nifty work done on the practicality of electrodynamic tethers and using them to turn a starship against the galactic magnetic field. You won't get sci-fi ship maneuverability out of this, but it's useful for course corrections without having to carry or expend reaction mass.

As far as onboard power sources go, fission seems perfectly cromulent. You just have to protect those radiators.

[Jweb_Guru]

I can only find one source on using tethers in interstellar travel: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/2005021.... To quote the article, for energy production:

> Since the tether current is 1,333 amps, ne = 3 X 10‘‘ m-3 and the ship’s velocity is 900 km/sec, the effective electron-collector radius is approximately 3 13 km.

This appears to have a toroidal-field ramscoop as a prerequisite.

For thrustless turning, a 0.06 degree turn requires a tether 10^3 km long:

> To obtain a six-degree trajectory modification during a 1,400-year journey with the tether current assumed, the tether length must be increased by a factor of lOOX to equal l0^5 km. This would increase tether mass to 2.7 X lo5 kg.

And this is using a reference ship many scientists are skeptical about:

> ...it is assumed here that the primary propulsion for these ships is the ultra-thin, space manufactured solar sail unfurled as close to the Sun as possible at the perihelion of a parabolic or hyperbolic solar orbit. After acceleration to interstellar cruise velocity, it is also assumed that sail and cables are wound around the habitat section to provide extra cosmic ray shielding. The sail is unfurled again for deceleration at the destination star.... since the baseline sailcraft for this analysis is somewhat faster, either more advanced sail/cable materials are required or the pre-perihelion orbit is hyperbolic.

I'd definitely categorize that under "experimental power sources and unproven physics." Perhaps you are thinking of a different article?

[stcredzero]

I got that from a Robert Forward nonfiction book. The craft he described didn't have ramscoops, but were lightsail craft.