"Morgans" wrote in message
...

"Bill Daniels" bildan@comcast-dot-net wrote

For Dan's earlier question about performance at altitude, what I hear
from Bob is that it looks pretty good. His real concern was restarts at
altitude. He made a big improvement in that by switching from glo-plugs
to spark igniters. As I understand it, the micomputer engine controller
senses altitude and adjusts the engine to adapt.

I also hear that the life of the engine, and especially the bearings (the
most prone to need replaced first) have been much improved in many brands
of engines, and that the little engines run happily for many hours.

Some of the engines out there are getting pretty big, and with big thrust
values to go along with it.

I'm thinking that a pair of them would make self launching possible; if
not completely unassisted, with an auto towing down the runway to, say, 30
or 40 feet of altitude?

Then, if a cruise at the same altitude was needed to get home, or
whatever, one could be shut down.
--
Jim in NC

I think the whole thing is coming together. The neat thing is most of these
engines only cost a few thousand dollars. Yes, they are thirsty but the
sailplane application is unique in that they need not run very long. One
thing seldom mentioned is that these little turbines whine at 150,000 RPM is
way above human hearing. All you hear is the exhaust roar and that isn't
too loud.

Takeoff will be a problem until we get workable afterburners. (It's been
done.) You'd only need the re-heat for a few seconds until liftoff.
Another takeoff aid that has been proposed is a bungee launch.

Although everybody in the know says the jet exhaust from a single piggyback
engine aimed at the fin doesn't do any harm, I'd like a little more
information on that.

Bill Daniels