[extropy-chat] next generation of ion engines

Adrian Tymes wingcat at pacbell.net
Tue Jan 24 22:05:10 UTC 2006


I did read their site.  In fact, I know some of their people.
High-performance ion engines might be useful for station-keeping
for their eventual goal, but it's not critical for achieving
orbital altitude their way.

If one wanted to get to altitude their way and then accelerate
to orbital velocity - one still runs into the problem of going
Mach 25 through an atmosphere thick enough to provide lift, from
wings or balloons or what have you, no matter how slowly one
approaches that speed.  (In fact, this is part of the reason why
rockets tend to get out of the lower atmosphere and then roll to
start horizontal acceleration.  Dealing with the atmosphere at
those speeds is bad enough once per mission, when you're
landing.)

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

> I guess you haven't read their site. Sure the most altitude they've
> reached
> is ONLY in the neighborhood of 100k feet. They are hoping to develop
> an
> ascender to regularly climb to much higher altitudes. Then they want
> to
> setup a permanent facility where a craft that can reach both orbital
> altitude and velocity can be constructed. A ship that will never be
> able to
> land but doesn't require an initial high velocity to achieve orbit is
> what
> they aspire to build. It's an AIRSHIP, just floatin' along to start,
> but at
> a high enough altitude that an ion engine can operate to accelerate
> it,
> slowly. It will (hopefully) be able to return to its starting point
> the same
> way- no flaming re-entry needed.
> 
> -----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 4:18 PM
> To: ExI chat list
> Subject: RE: [extropy-chat] next generation of ion engines
> 
> 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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