Re: interesting papers on microwave thermal launcher

In article <[EMAIL PROTECTED]>,
Tom Merkle <[EMAIL PROTECTED]> wrote:
>It's not an urgency to reach equatorial orbit. It's an urgency to be
>able to chose the orbit you launch into, much harder for this launch
>system than chemical rockets.

It's not actually that bad.  Selecting the direction of launch is not much
harder, given suitable terrain -- you move the launch point, not the
microwave transmitter -- and in any case, there are often only a few
directions of interest.  (Many of the Russian launchers do just fine with
the location of spent-stage impact areas limiting them to two or three
launch directions.)

If you're thinking of "dogleg" maneuvers -- making a turn partway up --
that is ruinously expensive in fuel for a chemical rocket, so it's rarely
done and the practical doglegs are quite small.  (E.g., the only time the
shuttle did one was to reach 62deg inclination rather than the 57deg it's
normally limited to, and that took heroic efforts of weight reduction.)
No way do you reach an equatorial orbit from 19deg latitude with a chemical
rocket by doing that. 

It might actually be *more* practical for this launch system, because the
effective engine performance is so much higher.  You launch due east, and
put a second microwave transmitter under the point where the orbit crosses
the equator, to do a plane-change burn there.  The only problem is finding
suitable geography.  That's tricky, as it turns out:  the equator crossing
is 90deg of latitude east of the launch site, and while that is on land
for either launch site, it looks to be in low-altitude jungle for either
(the Amazon for Mauna Kea, the Congo for Atacama).  Hmm, if you accept
some deliberate performance loss by launching south of due east, from
Mauna Kea you could probably put the equator crossing over the Ecuadorian
Andes.  From the Atacama it's harder, but there are some mountains in East
Africa.  Whether either set of mountains has sufficiently dry air is
another question, although the requirements aren't so bad because the
plane-change burn will be shorter and can be done more nearly overhead,
where the path through the atmosphere is shortest.

>I think the nature of this super-fast-acceleration launch system tends
>to favor a single trajectory which puts lots of satellites over time
>into the same orbit. As such, the only single orbital inclination I
>can think of that is useful to EVERYBODY is equitorial for GEO xfer. 

As noted above, it's not that big a handicap to be restricted to only a
few inclinations, and you can do that with a single microwave transmitter
by having multiple launch points around it.

Being able to launch into an equatorial orbit *would* be good, not just
for the GSO market but because it's the right orbit for an orbital
assembly base.  (In particular, you get one launch window to your base per
orbit, rather than one or two per day, because Earth's rotation does not
carry your launch site away from the plane of the orbit.)  But for that,
barring the possibility I note above, you really need a launch site on
the equator.
-- 
MOST launched 30 June; first light, 29 July; 5arcsec    | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well.  | [EMAIL PROTECTED]