Paul,
Reading the discussion about NASA prompts me to send some stuff with
current info. The aeronautics part is about 4% of the total NASA
budget, so it's small. Some friends of mine there are working on
electric airplanes, that can do things normal airplanes can't. Not
intending to talk about that, just bear with me for a moment.
Things are going to get very interesting in the next couple of
years. I know of at least two electric VTOL aircraft that have flown
with an adult human aboard, and several other teams that have flown
models and subsystems. They can't fly for very long, because
batteries are still too heavy. What's needed right now is a light,
quiet, reliable (note, I didn't say cheap, or efficient) range
extender that can address this problem.
NASA likes to develop high risk, high return concepts, because they
can. But they and their contractors
*buy* conventional solutions
when needs are met.
I talked with Woelfle about this a couple of years ago, and they have
the right approach but need funding in advance. They have already
developed a 20 kW unit which is great as far as it goes, but it needs
to be bigger.
To see where the market is going, go to uber.com/elevate
<
http://uber.com/elevate and download the white paper. Disclaimer: I
wrote the acoustic section, and parts of the others, as a consultant
for them -- they have a long way to go but it's a good start. Their
idea is simple -- if you build some of these and make it possible to
fly them in cities, Uber will buy some. Whether this is absolutely
realistic depends on too many variables to consider, but there will
be people competing in this space starting now, and they have
problems to solve.
The electrical part is fairly easy. You'd be using a multiphase
permanent magnet generator made the same way brushless motors are
made -- in fact they might be essentially the same part. Whatever
voltage and frequency is most efficient for a given design would be
fine, and the multiphase output would drive their power circuitry.
You'd have to do the analysis looking at the cruise power budgets,
but there will be needs for everything from 50 to 500 kW (70-700 hp
roughly) initially. A Rotax weighs about 130 pounds with cooling and
without gearbox, 92 hp all day at 5500 rpm. It makes sense to use
two of them to produce 200 hp (150 kW.) Can you beat this with a
rotary? If so, developers in this space will buy them.
David Josephson
I would rather not cater to that market. Too risky. I would rather
stick to an established market like LSA. We would still go head to
head against the Rotax. We could beat them on first cost and life.
Basically the Rotax is scrapped at the end of 1500 hours or what
every the TBO is now.
The turbo option would give us up to 250 to 300 HP with little
increase in weight.
Yes I know the LSA sport rules specify a max speed but the HP can be
used for STOL or even LSA VTOL :-) There is no rule on how fast you
can take off :-) My eye is on OZ as the entire out back is a
potential air field. I have flown all over the eastern third.
We have to sell enough of them to pay for the start up cost.
BTW David do you know Simon Saba? He and David Mikesell are in your
neck of the woods. I am thinking of driving up in the next few of
weeks.
Paul Lamar
Should be simple enough to use a pilot tube for speed sensing and
use a diaphragm to close another butterfly in the intake. Easy enough
to calibrate a spring to control speed. Is LSA speed limit indicated
or actual speed? Dale Davies
LSA limit is "maximum airspeed in level flight with maximum
continuous power (VH) of not more than 120 knots CAS under standard
atmospheric conditions at sea level." Many ways around that - just
not a problem unless the airplane is really slick. Carbon Cub is a
certificated S-LSA with a 180 hp ECi Titan (Lyc), it says right there
in the manual that you can't use full throttle continuously.
David Josephson
I guess that is sufficient to get around the top speed rules.
Did they define continuous ? :-)
---------------------------------------------------
The TTC gets off the ground in 2 seconds at half throttle no flaps.
(The flaps are bolted in the up position.) Give it another few
seconds to get over a 50 foot obstacle. A good high power STOL bush
plane could land and take off almost anywhere. Who needs a
helicopter? The engine power to weight ratio changes everything.
The TTC firewall forward weighs less than 300 pounds. That is roughly
2 HP per pound. The air cooled turbo one rotor at 150 pounds firewall
forward would be in the same category. Saves the weight of the
cooling system.
Paul Lamar
The weight of batteries should NOT be a consideration for electric
airplanes.
They can use Wi-Fli.
John Dinkel
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