# 300fps Apogee Velocity

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#### s3th

##### Member
I've got several of their standard chutes, no flights with data recorded hit at high speed, but I've had delays go long on smaller rockets, in the 3 pound range with a 3 foot rocket man chute. The design in general lends itself to a gradual opening.
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In my experience, they tend to open "softly" not just a big slam. Of course, the rest of the recovery system needs to be up to the task, but I'd think these chutes can absolutely handle the speeds you're looking at, if sized and mounted properly.
Thank you David for sharing your experience. That they tend to open softly sounds great, this will reduce the shock load. Well I think, I am on the right way. Anyway great pictures. Awesome. What was the take-off weight and motor of the two flights?

One way to calculate Isp is to take the total impulse divided by unit weight of propellant
I converted everything to imperial units.
10,000 Ns = 2248 lbf
5.0kg oxidizer + 1.5kg HDPE fuel = 6.5kg propellant = 14.33 lb
2248/14.33 = 156s
Edward
Hey Edward, ok I could follow you: I use:
Thrust (F)= Mass-Flow-Rate (m'_p) * Effective Exhaust Velocity (c*)
-> c*
ISP=c*/g_0

Well I get the same results. So anyway both ways work.
So the above image shows the first 0.5s of test #005_02 -> it was a 8s run with 4.5kg total fuel mass burned. The image shows the peak thrust with approx. 1600N - the average across the 8s was around 1260N:
m´_p=0.563kg/s
c*=2238m/s
ISP=228s
So its doing quit well ... in the beginning I´ve just thrown in some approx. numbers because it was about the chute. If you want do discuss the engine in detail we could switch the topic and go somewhere else (not in recovery....)

s3th

#### DavidMcCann

##### Well-Known Member
Thank you David for sharing your experience. That they tend to open softly sounds great, this will reduce the shock load. Well I think, I am on the right way. Anyway great pictures. Awesome. What was the take-off weight and motor of the two flights?
Nothing exciting at all on either. Both G motors and about 3 pound rockets. Probably going about half the speed you're looking at. The photos where more for demonstration of how the chutes act as they open. I've had them open at faster speeds, but no photos of those deployments.