Jet Powered Parafoil for Airlaunch

A couple years back Pete Lynn (http://www.peterlynnkites.com/)
posted about the idea of using a powered parafoil to airlaunch
a rocket. It seems you can scale to much large cargo weights
much easier than with an airplane. Since you just want a short
flight up to altitude, and you are not worried about distance,
gas mileage is not a big design issue.

This could be far lower cost than either a commercial or military
jet. There would not be the kind of problem with ground clearance
that you get with most existing aircraft.

If you have a parafoil with an L/D of 6 and a jet engine that has
thrust 5 times its weight you could theoretically maintain level
flight with a total flying weight of about 30 times the engine
weight. Since we want to go up fast we might really want only 15
times engine weight. Probably want 2 engines (one above the other
for centerline thrust) where each one could keep you up on its own.

Parafoils are very light, so designing with healthy design margins
would not be a problem.

You need some sort of frame for parafoil attachements, cockpit,
engines, rocket, and landing gear.

With a parafoil, a relatively small budget could get a custom tailored
design. Storage and maintenance would be much easier than a regular
airplane.

Landing with the same large parafoil, but with much less weight than
takeoff, could be tricky if there is any wind. It may be possible
to collapse center sections of the parafoil to reduce its size. Is
this a killer problem?

There is the usual problem that to get licensed and certified could
be a huge amount of money. Like maybe you get your jet powered
parafoil for $5 mil and it costs you $50 to $200 mil to get licensed.

What are the other pros/cons?

To see Pete's posts search sci space groups for
"pete lynn paraglider launch" as in:

http://groups.google.com/groups?num=...aglider+launch

Nasa says the X-38 parafoil was worlds largest:
http://www.dfrc.nasa.gov/Gallery/Pho...0-0317-52.html

I have a page on why Airlaunch is interesting:
http://spacetethers.com/airlaunch.html

If you are interested in particular jet engines see:
http://www.shanaberger.com/engines/e...esignation.htm

-- Vince

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~
Vincent Cate Space Tether Enthusiast
http://spacetethers.com/
Anguilla, East Caribbean http://offshore.ai/vince
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~

You have to take life as it happens, but you should try to make it
happen the way you want to take it. - German Proverb

Vincent Cate wrote:
A couple years back Pete Lynn (http://www.peterlynnkites.com/)
posted about the idea of using a powered parafoil to airlaunch
a rocket. It seems you can scale to much large cargo weights
much easier than with an airplane. Since you just want a short
flight up to altitude, and you are not worried about distance,
gas mileage is not a big design issue.

This could be far lower cost than either a commercial or military
jet. There would not be the kind of problem with ground clearance
that you get with most existing aircraft.

If you have a parafoil with an L/D of 6 and a jet engine that has
thrust 5 times its weight you could theoretically maintain level
flight with a total flying weight of about 30 times the engine
weight. Since we want to go up fast we might really want only 15
times engine weight. Probably want 2 engines (one above the other
for centerline thrust) where each one could keep you up on its own.

AIUI, a L/D of 6 is very optimistic.
Also, the flight speed is a problem.
You want to match the speed of the exhaust from the propellor or engine
to about the same magnitude as the speed.

I don't know how fast the fastest parafoils fly.
I'd be really, really surprised if anybody has gotten one to go at over
80m/s or so.

Also, jet engine thrust falls of with height.
The engine has nowhere near its sea-level thrust at 30000 feet.

--
http://inquisitor.i.am/ | | Ian Stirling.
---------------------------+-------------------------+--------------------------
Paranoia: A game for the whole family, and anyone else who might be watching.

"Ian Stirling" wrote in message
...
AIUI, a L/D of 6 is very optimistic.
Also, the flight speed is a problem.
You want to match the speed of the exhaust from the propellor or
engine to about the same magnitude as the speed.

An L/D of 8 is typical for paragliders, I have heard of high performance
paragliders reaching 13, at the expense of stability, (they start
killing people).

I don't know how fast the fastest parafoils fly.

Paragliders have maximum flight speeds of around 35 km/hr, (10m/s), this
is because they are primarily concerned with sink rate and L/D.

I'd be really, really surprised if anybody has gotten one to go at
over
80m/s or so.

I think skydiving chutes designed specifically for forward speed might
reach 40-50m/s or so. There is no fundamental reason why they can not
fly faster, I do not even see why supersonic flight would not be
theoretically possible, not that I can see any good reason for doing so.

A paraglider might cost $3000, fly at 10m/s, and lift 100kg. Ideally a
take off speed of 50m/s might be desirable, say 250m/s at a very high
launch altitude, such a paraglider might lift 2.5 ton and cost $10000.
Paraglider cost is primarily determined by minimum gauge constraints,
(minimum fabric weight), and so is largely independent of load. Thus
such a high speed/load paraglider might cost $10000, or less, (excluding
development cost), they might even use rigid materials, (higher L/D).
Such paragliders could probably be scaled into the thousands of tons.

Also, jet engine thrust falls of with height.
The engine has nowhere near its sea-level thrust at 30000 feet.

This is the real problem, propulsion is I think more critical than
airplane type, personally I do not think that jet engines are an
appropriate solution to this problem, (assuming subsonic flight). I
favour carrying your own oxidizer, as it is a short high power trip,
also, propulsive efficiencies favour a propeller or rotor, over a ducted
fan. And so some possibilities that come to mind are a rotor with tip
rockets, a turboprop with mass injection, a pure rocket powered
turbine/rotor, etc.

Pete.

Ian Stirling wrote in message ...

[snip]

You want to match the speed of the exhaust from the propellor or engine
to about the same magnitude as the speed.

That would make the rocket engines more efficient, but some people are
trying to launch rockets from balloons, too.

"It was Saturday, March 25, and the day of reckoning had finally
arrived. Much work had been performed preparing for this day. The
test facility was to be christened with an asphalt and nitrous-oxide
(N2O) hybrid rocket motor (in the middle of the stand test) capable of
achieving a total impulse of 2000 lb-sec (200 pounds of thrust for 10
seconds), which we estimate could loft a balloon-launched rocket into
space."

http://home.hiwaay.net/~hal5/HALO/reports/rmtd_01.shtml

"A hybrid-fuel rocket launched from a balloon on May 11 [1997] became
the first amateur-built rocket to fly into "the edge of space",
reaching a peak altitude of 64 kilometers (40 miles).

"Space Launch 1 of Project HALO (High Altitude Lift-Off), a project of
the Huntsville Alabama L5 (HAL5), took place on the morning of Sunday,
May 11, with a balloon launch from Hampstead, North Carolina. Ninety
minutes after the balloon lifted off, at an altitude of 18 km (60,000
ft.), the rocket it carried ignited and flew a suborbital trajectory
above the Atlantic Ocean.

"The HALO team had planned to launch the rocket when the balloon
reached of 30 km (100,000 ft.), but were forced to launch early when a
seam burst in the balloon at the lower altitude. As a result, the
rocket reached a peak altitude of 64 km (40 mi), less than their
planned peak of 108 km (67 mi.)"

Amateur Rocket Reaches "Edge of Space"
http://www.seds.org/spaceviews/970515/top.html

"In the competition to build the first privately funded, reusable
spacecraft, IL Aerospace Technologies (ILAT), an Israeli entrant in
the $10 million X Prize competition, have high-rise hopes of snagging
the cash.

"The group is working on the Negev 5, a concept using a large
super-pressure helium balloon as a first stage for flight. That
balloon totes both hybrid motor-propelled rocket and the crew capsule
to the upper reaches of the atmosphere. High above Earth, rocket
engines are ignited that will propel the vehicle and crew into space."

"Israeli X Prize Entry Has High Altitude Hopes"
http://www.space.com/businesstechnol...ze_030710.html

"DaVinci is tethered to a balloon and launched from a high altitude
with liquid oxygen/kerosene rockets. Landing is achieved by a
combination of high-drag reentry ballute and parachute."

"X Prize Contestant Chooses Launch Site"
http://www.space.com/missionlaunches...te_030630.html

- 1952 Jul 29 - First Rockoon launch attempt.
First Rockoon (balloon-launched rocket) launched from icebreaker
Eastwind off Greenland by ONR group under James A. Van Allen. Rockoon
low-cost technique was later used by ONR and University of Iowa
research groups in 1953-55 and 1957, from ships in sea between Boston
and Thule, Greenland.

http://www.astronautix.com/astros/vanallen.htm