About Parachute Configuration of a HPR Rocket

[John Feller]

Hello all,

I am planning to launch the high power rocket. I have chosen Iris Ultra 60" parachute as main and 48" fruity chutes as drogue chute. I was wondering that if this parachute configuration is suitable or not for the rocket that has weight of 20kg.

Thanks in advance!
John

 

[Nytrunner]

The answer is: It depends.

Needed info:
-Expected altitude
-Fin material and configuration (Swept back? delta? other?)
-Field surface (hard dirt? soft grass? desert packed? asphalt? other?)

With a target rocket mass of 20kg, Fruity Chutes' online descent calculator gives me:
29.75 ft/s for the main
37.2 ft/s for the drogue

Main:
Depending on how hard your surface is and what your fins are made of (and how they're shaped), this may be a bit fast. If they're delta or other shapes that aren't swept back, you may be ok since the motor will hit the ground first. If the fins are swept back or simple plywood, You should consider a slower landing speed. Also if the ground is hard, you'll want slower landing speed.

Drogue:
This is Very slow for a drogue descent. Not even 10 ft/s faster than your main. If you're flying to any altitude over a couple thousand feet, your rocket will drift forever on that drogue. A good target is ~75-90 ft/s for drogue descent, although you of course want to make sure your recovery harness can handle the deployment shocks.

Summary (Nyt's opinion): If I were planning this flight, I'd increase the main chute size and decrease the drogue size.

 

[HHaase]

I'd concur on Nyt's suggestion. I'd want to reduce the velocity on the main to around 20fps, and about double the speed on the drogue.

With a chute and rocket in that weight category, also consider a reefing ring or other similar piece to slow the deployment of the main and reduce the shock on the lines.

-Hans

 

[Bat-mite]

I agree. The whole point of DD is that you can get a nice, gentle landing with a bigger main, and a rapid, close to home descent with a drogue. The only thing the drogue has to do is keep the NC and booster separate and pointed away from each other.