Microjet self launchers

I want to apologize to anyone I offended with my "Dog Whistle" remark about
the Silent jet glider. I have long held a disparaging view of small turbines
based largely on their huge cost, noise level, awful specific fuel economy
and short lifespan. There's also the safety issue of a compressor wheel
turning at 115,000 RPM - you really don't want to ingest any debris. This,
I now find, is a very out-of-date viewpoint.

It's easy to have missed the huge advances in microjet technology unless you
are an active part of the radio controlled aircraft hobby. I decided to
surf through the web looking for information about these and it's an eye
opener. These guys are building and flying small centrifugal compressor
turbojets of amazing sophistication. Tiny FADEC systems completely manage
start and run functions. All safety issues seem to have been satisfactorily
dealt with. Even with this success, the microjet boffins are not satisfied.
Even better engines are in development.

I think that Mike Borgelt is exactly right when says, "I have seen the
future of soaring". At small turbojet self launcher does make a awful lot
of sense. The fuel consumption and engine life issues are not a factor
since the engine in not expected to operate more than a few minutes at a
time. The concern I alluded to about poor initial acceleration is real but
there is a solution - afterburners! The RC model guys have done this too.

A 5 -10 minute engine run for a 2000 foot AGL launch seems about right.
This might consume about 10 gallons of kerosene even with an afterburner
used for the ground roll. As a strictly self-launcher, the residual weight
of the engine, empty fuel tank and support systems, is quite small.

Dealing with the hot exhaust will be an issue but not a show stopper. Two
engines canted a few degrees to the side would do it or even a single engine
with a "Y" tailpipe that deflect the exhaust to the sides of the fin.

The self launch operation will be simplicity itself. The pilot just pushes
a button and holds it in. The engine starts and goes to full power and
stays there until the fuel is exhausted or the pilot releases the button.

Contemplating air re-starts or trying for a sustainer capability will raise
the level of complexity and residual weight considerably but it's probably
doable.

Bill Daniels