[extropy-chat] next generation of ion engines

Adrian Tymes wingcat at pacbell.net
Sat Jan 14 21:18:17 UTC 2006

That will work for getting things to orbital altitude.  There's
a big difference between orbital altitude and orbital velocity.
Better ion engines would be of possible use for stationkeeping,
and for the sats they launch - but doesn't really strike me as
something they would get uber-excited about.  That said, they're
also well short of the edge of space: their latest mission only
got to about 78 thousand feet, well short of 100 km (about 328
thousand feet).

--- Dennis Roberts <live2scan at charter.net> wrote:

> You really don't need SpaceShipOne or anything like it. Check out
> http://www.jpaerospace.com/, these folks are probably still dancing
> around
> after ESA's announcement. Low cost access to LEO is comin' to us all.
> Dennis Roberts 
> -----Original Message-----
> From: extropy-chat-bounces at lists.extropy.org
> [mailto:extropy-chat-bounces at lists.extropy.org] On Behalf Of Adrian
> Tymes
> Sent: Saturday, January 14, 2006 2:57 AM
> To: ExI chat list
> Subject: Re: [extropy-chat] next generation of ion engines
> --- deimtee <deimtee at optusnet.com.au> wrote:
> > It takes about 10 newtons to lift a kilo against 1 gee.
> ...right, forgot to factor in G.
> > However,  how about if you dropped it off SpaceShipOne at apogee?
> > How much time have you got to give it orbital velocity before drag 
> > exceeds thrust?
> >From http://en.wikipedia.org/wiki/SpaceShipOne_flight_17P we
> know that SSO only took 24 minutes between detaching from White
> Knight through apogee to landing, of which just over 80 seconds
> was spent under thrust.  So the apogee-to-landing phase probably
> took about 12 minutes.  Most orbital rocket launches I've
> studied seem to take about 10 minutes to get to orbital
> velocity.  So, you'd probably need wings or something to gain
> lift while going at hypersonic speeds - and the wings would need
> to be thermally protected (probably made out of solid heat
> shields), because as you get towards Mach 25 you're flying not
> through air but through plasma.  Which is not to say it can't be
> done, just that a proper analysis is probably way in excess of
> simple back-of-the-envelope equations.
> I wonder, though: what would be the physics of flying through
> plasma?  Could you use an M2P2-type magnetic bubble to shield
> the craft from direct contact with the atmosphere, while still
> maintaining enough of an airfoil shape (in the bubble, which
> seems to be the shape that would then matter for lift and drag
> calculations) to gain lift?
> > also,
> > I think you are a bit optimistic on the battery too.
> > 
> > 100kW * 10 min = 16.666 kWHrs
> > Thats about the same as a 12 volt battery delivering 1400 amps for
> an
> > hour.
> > 
> > I want some of those for my electric car.   : )
> Actually, some of the sources were advanced batteries being
> developed for cars.  But I did caution that that was the
> optimistic end of the figures I was seeing: quite a few of the
> "most advanced" figures were quite a bit more conservative than
> that.  ;)
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