On Thu, 25 Aug 2005 12:40:30 -0700, richard.kiray wrote:

The August issue of AOPA PILOT reports a "tiny jet engine" is being
developed with 150 lbs of thrust. Its 15" long, 8.6" in diameter and
weighs 19 lbs. I wonder what it costs? This sounds like a great power
to weight ratio.

I don't think power/weight is very significant for our use. Thrust/drag
ratio is a lot more use. Calculate that for your glider at typical
inter-thermal speeds, double it and that's probably all the thrust you'd
need. I did a rough calculation for an SZD Junior at 65 kts and got about
22kg of drag, Double it and you're looking at 40kg, 88 lbs thrust.

Fuel consumption is also important: a turbojet at sensible glider speeds
will be thirsty. Maybe you just carry jet fuel instead of water ballast to
bring you up to Mtow?

Finally, make sure the engine management system is as good as those on RC
models because this means that the engine will take care of its start
sequence all by itself: if you're low you don't want to be paying
attention to a manual start sequence.

Its all been done anyway: a German University project flew a Ventus on a
single 35 lb st. engine (climb rate .001 m/sec IIRC) and there is/was a
glider on the US display circuit with a pair of 35 lb st. engines: the
implication was that it was self launching from a sealed run.

--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |