Parachute -forces 1

[O320]

Hi All,
I'm trying to get a feel for the opening shock g-load in various parachutes. I've found NACA TN 2051 on their server, and it seems from this the jolt would be in the order of 2g. Anybody with knowledge or a literature tip out there?

 

[Barry1961]

I know the shock load will vary greatly due to the way the chute is packed. Sky divers vary there pack to how fast they want the chute to open. Skydivers doing relative work will often have the chutes opening so fast that a few risers will break.

Barry1961

 

[Kiwikid]

There's a whole range of characteristics that will effect opening shock G-load;

payload, velocity on opening, altitude on opening, air density on opening, type of chute (square/round), exhaust opening(s), steerable/non steerable, chute square area, aerodynamics of chute, packing method, deployment method (static line/pull cord/hand deploy/braking chutes), aircraft speed, air movement (stable/descending/thermal)

I remember watching a doco on chutes for the Mars lander. Chutes would not consistently open correctly to be reliable. After much testing and hair pulling they finally bought in chute design experts. The exhaust hole in the centre was the culprit.

Have fun ;-)
Kerry

 

[O320]

Thanks for your input. Every new field you enter soon shows itself to be a science in its own right...

 

[davidjh]

AIAA used to (still does?) sponsor an "aerodynamic decelerator" conference/symposium. Check with them re availability of those papers.

 

[IRstuff]

Did you try the NASA report servers, of which, the following is one:

http://ntrs.nasa.gov/index.cgi?meth...0&mode=simple&order=DESC&keywords=parachute

NASA has done extensive analysis and testing of parachute recovery systems for all of the previous manned spaceflights as well as the Mars Rover. Ditto the Soviets for their Soyuz program.

TTFN

 

[GraviMan]

Don't forget that most chutes have a ring around the risers designed specifically to limit the area of the chute. As the chute deploys, the ring stays near the chute to limit the deccel force. As the deccel force reduces, the ring moves down the lines keeping the deccel force approx constant.

Someone, most likely NASA, will have done some maths on the effect. Fun stuff air...

Mart

 

[unclesyd]

Here is a website of the developers of the parachutes for light aircraft. One was just used in Texas to land a plane that had lost part of it’s wing. In the newscast concerning this event it shows a rocket assisted deployment of the chute and the actual reefing device mentioned in the history page. I think the plane in Texas was a Cirrus Design. I’ve seen a NASA short that has similar type deployment and reefing device.

http://brsparachutes.com/CI_history.mgi

 

[Darkmann]

Interesting question. Incidentally I had the same question as of last year. We have started rigging flight systems with accelerometer to gage the system response as the parachute deploys. The time domain data is quite interesting. The problem I have at the moment is how to analyze the data. Most people say to use shock spectrum analysis but that doesn't seem to do it since I have output data and would like to know whaich input resulted to that output. The output data is magnified because the system does have some non unity transfer function. Yesterday I was able to derive a simple formula for determining the input. I hope to test it sometime this week. Does anyone out there have an idea how to resolve this problem?

 

[vorwald]

Darkman
What's the input? I assume the output(s) are accels. I'd like to look at the data if possible. I have an upcomming report using subspace analysis on flight data; that may work on your data.

J. Vorwald