Recovery Questions?

[AfterBurners]

Why and how does the elevation at the launch site affect the performance of the chute?

Is it because the air is denser at higher altitudes?

https://www.spherachutes.com/decent-rate-chart
Also the descent rate is only around .750. I always thought that having an elliptical shaped chutes would produce a higher CD? It seems the rate is the same as the typical flat para-sheet style chute, but I know that the elliptical type chutes do perform better because they are more stable keeping the rocket from swaying from side to side when under the chute. So Fruity chutes offer an excellent chute, but of course there's the price to consider. Their chutes produce a higher CD, but because they measure the chute sized based on the actual opening of the chute and not the diameter.

I also have a couple PML chutes, but I would assume their performance is similar to Spherachutes as far as CD?

So what chutes do most of you like to use? I no longer use the flat chutes only in smaller type rockets etc. I had a friend who launch his G-FORCE and recovery was on a 45" flat style chute. Nice flight and nice recovery. Problem when it landed the chute inflated and dragged the rocket about a 100 yards or more along the desert floor. Completely ruined the paint job down to where it put a hole on the body tube and had to be replaced. So I've come to learn to steer clear of those types of chutes. Not only that most of the companies that make the chutes sew the shroud lines from corner to corner, which causes a couple lines to tangle. Never could figure that out? Why not just sew them across from one another so when you pull the chute at the apex the lines all come together even without any tangling.

So what chutes do most of you like to use?

 

[SpaceX76]

Chutes perform better at lower altitude because the air is denser this means that the chute has more drag. But as you increase altitude the air becomes less dense this means that the chute(s) have less air molecules to resist against. My chutes that I like are plastic for low power and the nylon for mid to high power.When it comes to type i fined that flat chutes work the best for low power and mid power this is because i cluster my chutes.

I hope this helps

 

[Bat-mite]

I generally use TFR PARs for anything up to K motors, and Rocketman for bigger projects.

 

[AfterBurners]

thanks guys! TFR makes exceptional chutes. I have a few on them as well

 

[Handeman]

When you talk about Cd of a chute, you have to know what you are talking about and how that is calculated.
Some manufactures use diameter as the open flat diameter of the chute when laid flat. For a flat chute, this can be tip to tip or flat to flat. Some use the diameter of the inflated chute under load. Others used the designed diameter of the chute. Some use the distance from one edge to the other edge across the dome of the chute. All of that comes into play when calculating Cd. Also the type and porosity of the material plays a part.

I make all my own chutes. Mostly from umbrellas from small kids umbrellas to large golf umbrellas. That covers most rockets from 4 to 10 lbs. Anything larger and I make elliptical chute based on decent calculators for elliptical chutes.

If I was going to buy a chute, I would base it on the decent calculations the manufacturer provide rather than any Cd specification they may have. If you want 15 ft/sec for a 20 lb rocket, some manufactures will tell you their 8 ft. diameter chute is good, other will tell you their 12 ft. diameter is right. All of them are probably right because it doesn't matter how they calculate things, lbs and speed are going to take into account everything else.

If they don't list the decent rates in speed vs. mass for their chutes, I would be hesitant to buy.

 

[AfterBurners]

When you talk about Cd of a chute, you have to know what you are talking about and how that is calculated.
Some manufactures use diameter as the open flat diameter of the chute when laid flat. For a flat chute, this can be tip to tip or flat to flat. Some use the diameter of the inflated chute under load. Others used the designed diameter of the chute. Some use the distance from one edge to the other edge across the dome of the chute. All of that comes into play when calculating Cd. Also the type and porosity of the material plays a part.

I make all my own chutes. Mostly from umbrellas from small kids umbrellas to large golf umbrellas. That covers most rockets from 4 to 10 lbs. Anything larger and I make elliptical chute based on decent calculators for elliptical chutes.

If I was going to buy a chute, I would base it on the decent calculations the manufacturer provide rather than any Cd specification they may have. If you want 15 ft/sec for a 20 lb rocket, some manufactures will tell you their 8 ft. diameter chute is good, other will tell you their 12 ft. diameter is right. All of them are probably right because it doesn't matter how they calculate things, lbs and speed are going to take into account everything else.

If they don't list the decent rates in speed vs. mass for their chutes, I would be hesitant to buy.

And if I wanted a chute from the manufacturer that had a slower descent rate I could always go up in size and vice versa if I wanted it to come down a little faster depending on the recovery if it was soft or hard like a desert floor. Okay that makes it a lot easier than putting all these calculations into a design program. Thank You sir!