|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
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 |
#2
|
|||
|
|||
Jet Powered Parafoil for Airlaunch
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. |
#3
|
|||
|
|||
Jet Powered Parafoil for Airlaunch
"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. |
#4
|
|||
|
|||
Jet Powered Parafoil for Airlaunch
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 |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
What we need is a nuclear powered moon rover | bob haller | Space Shuttle | 0 | April 4th 04 09:20 PM |
Space Station Over Powered | VTrade | Space Station | 0 | January 21st 04 10:21 PM |