Yet Another UAV Thread...

I need your help!

I'm trying to find out the required surface area for a parachute to be used in the killswitch mechanism.
Basically, if the UAV leaves radio range it will automatically stop engine and deploy parachute...making sure I don't have a fly-away.

I think this is the formula for it...but I'm not 100%

Someone help me out?

D=1/2 rho v² S Cd

D = drag force
rho = air density (1.225)
v = desired descent velocity (2 feet per second)
S = parachute surface area
Cd = drag (.75)

Where would I input the object's weight/mass?
I need to solve for S.

I know, its simple algebra...but Im sick and my brain is mush.

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the answer is Pi ! but really i can't think right now either sorry..

ooohh I can help! 3 years in rocketry finaly pays of!!

But first how do you plan on deploying the 'chute?

...Also I think instead of using a chute you should consider streamer recovery (weighs much less and takes up less space)

Zane wrote:

ooohh I can help! 3 years in rocketry finaly pays of!!

But first how do you plan on deploying the 'chute?

...Also I think instead of using a chute you should consider streamer recovery (weighs much less and takes up less space)

Ya I was thinking about stealing the deployment charge from a model rocket motor...then have it connected to the plane's Li-Po.
There's space in the rear of the airframe that I could drill out...and depending on the material/size of the parachute stick in the hole with wadding.
Then cover the hole with either a plastic cap or tape...that way there isn't any change to airflow.

And I found a system recommended to me by some guys at DIY drones for the actual triggering of the system...it basically sets up an adjustable perimeter around your controller...and when the drone flies outside of that perimeter, it will initiate a script of your choice. If I can get a board that will divert electrical flow from the motor to an igniter (to deploy the parachute), I think it might work.

Again, this is only a concept. I've seen it done before and it was beautiful...

While I can't help you with the electronic stuff, your best bet is to find a brick or somthing simular that weighs the same as your set up and do some trail and error with the streamer set up. We competed on a National lvl with rocketry and I can tell you parachutes get "Watch your language" expensive (the good kind, since they will most lily be hand made)

Once you tell me the weight I can make some recomendations.

Your olso going to have to deal with drift, bigger shoot=softer landing=more drift

Zane wrote:

While I can't help you with the electronic stuff, your best bet is to find a brick or somthing simular that weighs the same as your set up and do some trail and error with the streamer set up. We competed on a National lvl with rocketry and I can tell you parachutes get "Watch your language" expensive (the good kind, since they will most lily be hand made)

Once you tell me the weight I can make some recomendations.

Your olso going to have to deal with drift, bigger shoot=softer landing=more drift

Ya I thought about streamers...but idunno...
I have experience with the little D and E rockets...which weight about 1/4 of what my rig will weigh...so I think if I just get 2 or 3 parachutes from the model rockets and set up a rig to make sure they don't tangle...

The parachutes are just plastic...basically trash bags...hahaha

They fold up real small too, so I think that might work.

But I'm willing to try streamer recovery. Never done anything with them in the past, though

G50 Rockets in a cluster r ftw.

Plastic chutes are "Watch your language", they get ripped, they melt, they don't deploy right...the list goes on and on and to be honost a little estes chute wont get you far.
(BTW if you get the reloadable rockets you can easily get the charge that deploys the chute...aerotech's prices aren't to bad..)

But yeah streamers are very nice..and yay for cheapness

Heres a link to thier online catolouge

http://www.aerotech-rocketry.com/products.aspx

Im starting to get kinda shakey about using high temperature explosives and reactants around foam...hahah...

Seems like I'd have soup real fast.

Are there any low-temp deployment charges?

Maybe I should look into a C02 method?

Mhm...correct me if im wrong but isn't compressed CO2 VERY cold?...I seem to recall some interesting burns...

Simple compressed air wouldnt be to hard.

A box like chamber with a flap controlled by a micro serve (flap has a one way valve for compressing chamber)

When you open the flap *POOF* your streamer/chute goes flying out.

EDIT:...or you could simply line the inside with insulation sprayed in some sort of fire retardent. (We called it dog barf...used it instead of the tissue as spacer between rocket and chute)

But honestly? The way it's build I wouldnt worry about a chute...it's pretty sturdy. More importantly id worry about switching the prop of so it doesnt hit somone.

Zane wrote:

A box like chamber with a flap controlled by a micro serve (flap has a one way valve for compressing chamber)

When you open the flap *POOF* your streamer/chute goes flying out.

Makes sense.

That is a viable option.
I'd have to pack the streamer/chutes real light...or they'll stick around inside the chamber longer than we want...

Come to think of it, I do have an extra micro servo sitting around...

...

...

WAIT A SECOND!!!

X-Module.
http://secure.hobbyzone.com/catalog/HZ/search/HBZ6023.html

I could figure out how to do that...maybe just cut the system down so it can fit inside a cavity in the under-carriage...

Plugs right into the plane's electronics. All I'd have to do is hijack some of the electronics from an X-module compatible plane...

hmm...

Heh i actualy have a aerobird challanger...never bought the drop thing tho. ANother cool thing they have is laser tag..you hit the guy his engine shuts down lol.

But yeah...what could also happen is a little basket with a hinged lid...servo opens it and drag pulls chute out..(would only work with streamer I think..chute to heavy) (basket would have holes in it to let it pass

Zane wrote:

Heh i actualy have a aerobird challanger...never bought the drop thing tho. ANother cool thing they have is laser tag..you hit the guy his engine shuts down lol.

But yeah...what could also happen is a little basket with a hinged lid...servo opens it and drag pulls chute out..(would only work with streamer I think..chute to heavy) (basket would have holes in it to let it pass

HMM...depending on the range of those laser tag things...if I were to use this for wargaming, I could give the OPFOR one of the laser thingies...
You know that'd be cool.

But ya, I'll see if I can't jurry rig something this weekend.