[ExI] specific thrust

[Adrian Tymes]

On Fri, Dec 10, 2010 at 8:06 PM, spike <spike66 at att.net> wrote:
> Feynman suggested the concept in 1941.  NASA has managed to get drives that
> could be hauled into orbit that are capable of sending an ion stream all in
> the same direction with a velocity at around 30 km/sec.  This would provide
> enormous *specific* thrust, but the total thrust is in the milli-newton
> range.

I think I recall reading about that.  This was why I was specifying that the
thrust-to-weight of the engine needed to include the power source, so you
can't get away with claiming "enormous" thrust without including everything
that would need to scale up in order to scale the engine up.

> So you could eventually use something like that to navigate in
> space, but it requires patience.  It could be scaled up, but everything
> scales together.

IIRC, the main problem was a heavy power source - and there's been much
research since then into lighter weight power sources.  So I wonder if it would
be possible, using today's technology, to build an ion engine that could
deliver 1G+ of thrust - again, including something to power said ion engine for
about 10 minutes.