I’m not sure where to post this, or whether anyone will be able to help me, but here it goes…

For a research project I need a parachute to guide a 4 lb payload from high altitude. I’m hoping that a kite will work. Or at least partially work. This is an early prototype, so it doesn’t need to be perfect.

The payload will be released from a weather balloon (ie. from near zero airspeed), and as the payload falls the parachute will deploy. An on board computer will then guide the parachute back to a desired location.

Basically, the parachute needs to:
* have a reasonably good glide ratio
* be fairly stable
* deploy/open reliably, (from being folded appropriately)

I’m thinking that the deployment of the parachute would be somewhat similar to a kite in the power zone (very high angle of attack), and descent would be somewhat similar to a kite near the edge of the envelope (lower angle of attack).

I’ve read that for parasailing the ‘ideal’ wing loading is 3.1kg/m^2. This seems really high to me. Any comments? How large of a kite would generate about 4lbs of pull near the edge of the flight envelope (in say, a 15 or 20 mph wind)?

I’m concerned that if I buy a kite that is too large, the kite won’t deploy properly, and/or, it won’t develop enough forward speed. Similarly, if it is too small, the glide ratio will suffer.

Which kite?

From a control perspective, it would be easiest to use a quad line kite, that is (if I’m using the lingo correctly) quad line biased. That way most of the weight can be supported by two lines fixed to the payload, and the steering can be done with only the brakes (thus requiring smaller motors).


I'd be very happy to hear anyone's thoughts or ideas on this.

Thanks,
Warren

Quote:

Originally posted by spice I’m not sure where to post this, or whether anyone will be able to help me, but here it goes… For a research project I need a parachute to guide a 4 lb payload from high altitude. I’m hoping that a kite will work. Or at least partially work. This is an early prototype, so it doesn’t need to be perfect. The payload will be released from a weather balloon (ie. from near zero airspeed), and as the payload falls the parachute will deploy. An on board computer will then guide the parachute back to a desired location. Basically, the parachute needs to: * have a reasonably good glide ratio * be fairly stable * deploy/open reliably, (from being folded appropriately) I’m thinking that the deployment of the parachute would be somewhat similar to a kite in the power zone (very high angle of attack), and descent would be somewhat similar to a kite near the edge of the envelope (lower angle of attack). I’ve read that for parasailing the ‘ideal’ wing loading is 3.1kg/m^2. This seems really high to me. Any comments? How large of a kite would generate about 4lbs of pull near the edge of the flight envelope (in say, a 15 or 20 mph wind)? I’m concerned that if I buy a kite that is too large, the kite won’t deploy properly, and/or, it won’t develop enough forward speed. Similarly, if it is too small, the glide ratio will suffer. Which kite? From a control perspective, it would be easiest to use a quad line kite, that is (if I’m using the lingo correctly) quad line biased. That way most of the weight can be supported by two lines fixed to the payload, and the steering can be done with only the brakes (thus requiring smaller motors). I'd be very happy to hear anyone's thoughts or ideas on this. Thanks, Warren

First off let me say that the smaller the parachute/paraglider is the more difficult it is to compare to a larger one. The wing loading you have for a paraglider is correct. The wing loading is approximately .88 lbs. sq.ft. A paraglider is designed for ascending. The paraglider utilizes thermals and updrafts to stay airborne for long periods of time. The typical paraglider is not made for terminal velocity openings.

A parachute is designed mainly for desending. The parachute can withstand the forces generated on it during the opening process. Some parachutes are getting smaller now and utilize a cloth that is similar to paragliders. The opening forces on smaller parachute are about the same but it is somewhat easier to the jumper under it. Older parachutes had wing loadings in the area of .5 to 1.0 lbs sq. ft. or The newer parachutes since some are getting smaller have a wing loading that is higher 1.2 to 1.5 lbs. sq. ft. or more. The larger number will to 2 things for the jumper. 1. get the jumper to the ground quicker. 2. upon landing flare generally the jumper will be able to control his glide by applying the brakes and achieve what appears to be a very high glide ratio. Keep in mind this long glide only last until the airspeed drops.

The (quadline type) kite would be best for your application as it has the same number of attachments that a real parachute would have. You should also be aware that if the payload is too large (area) than it will reduce the flight performance. The payload will slow the kite down.

There are allot of other questions that need to be answered first but I would go with the higher wing loading and a quad line type kite.

Master Parachute Rigger

Do a search on NASA Wing, The NPW 5-LK for instance, is a kite that is based on the original design for the NASA space program by Francis Rogallo, this initial concept of a brake parachute has been refined and improved to its current performance.

Just one of many such links on the internet: http://www.countrywhatnotgardens.com/kites/hq_npw.html.

If you want, you could choose to build one; this link could help: http://www.xs4all.nl/~pdj/nasaplan.htm.

Good Luck!

I looked at the NPW a while ago, but I don’t think it is quite what I am looking for.

Over the past couple of days I’ve been talking Ted. He has been a tremendous help, even going so far as to build a deployment system.

Macpara Begos creat alot of sustained static lift. They are also made by a paraglider company, and may have many of the same traits. Something in the 4 meter size would definitely be enough, and if your payload is too light, you can always add weight. Just my thoughts, but who knows..


Scoop