The table below shows our measurements done over a period of 5 years to accurately determine the coefficient of drag (Cd) of the Iris Ultra Parachutes.

All tests were done having measured the weight of the rocket accurately upon landing. In addition we had precise information on the parachutes themselves and used altimeters to log the data. Factors that affect the coefficient of drag are altitude, barometric pressure, air temperature, and humidity. The factors listed here, given that altitude stays constant, can vary the Cd by up to 20%. Fruity Chutes rating of 2.2 Cd is considered to be very close to the worst case that we had measured over many flights.

 

Fruity Chutes Iris Parachute Cd Performance Log

 

     

Rocket, Drone, or Company

Who

Chute Used

Date

Diameter (in)

Recovery Weight Lbs

Descent Fps

Calculated Cd(frontal area)

Mag Max GE IFC-72 4/1/2011 72 15.53 15.05 2.103
Mag Max GE IFC-60 5/20/2011 60 16.1 17.9 2.219
Comp 4 GE IFC-72 5/21/2011 72 23.3 16.95 2.487
Mag Max GE IFC-72 6/12/2011 72 15.6 13.667 2.562
Comp 4 GE IFC-72 4/7/2012 72 22 18 2.083
Comp 4 GE IFC-72 5/19/2012 72 23.6 16.85 2.549
Comp 4 GE IFC-72 6/16/2012 72 23 16.75 2.514
Not sure DR IFC-60 7/20/2012 60 16.8 18.5 2.168
Max Maxx Thunderdome GE IFC-72-ZP 1/2/2016 72 19.025 13.97 2.990
MN Drone Ido IFC-66-SUL 1/22/2016 66 13.78 14.57 2.369
MN Drone Ido IFC-66-SUL 1/22/2016 66 13.78 12.66 3.138
MN Drone Ido IFC-66-SUL 1/22/2016 66 13.78 13.06 2.949
MN Drone Ido IFC-72-SUL 1/22/2016 72 13.78 12.7 2.620
MN Drone Ido IFC-72-SUL 1/22/2016 72 13.78 11.45 3.224
MN Drone Ido IFC-72-SUL 1/22/2016 72 13.78 12.57 2.675
MN Drone Ido IFC-72-SUL 1/22/2016 72 13.78 12.04 2.916
Mag Maxx Thunderdome GE IFC-72-ZP 2/6/2016 72 19.025 15.6 2.398
               
           

Average Cd

2.586

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