Main chute plus drogue?

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rocketcharlie

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There is something I have been wondering. On a dual deploy set up will the drogue chute and main chute act in concert to slow the descent to a greater degree than what is stated in a descent rate calculator when just the size of the main chute is entered? It seems like it would have to. Can the size of the main chute be lessened if this is true?
 

DaveW6DPS

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Anything producing drag slows descent. Although the drogue should not have a major effect. When the main slows the descent the drogue becomes much less effective.

As for reducing the size of the main, if it inflates, why reduce it? Slower on touchdown is better, and the whole point of dual deployment is to open the main at a lower altitude.

Size the drogue so that the main can open without too much stress and size the main for a good touchdown speed relative to the surface you will be landing on.
 

JoePfeiffer

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Yes, but you should regard the small difference as just providing a little bit of extra safety margin. Plan on the descent rate from the main.
 

Handeman

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Generally, the drogue is not there to slow decent. It is there to stabilize and control the two parts of the rocket as they drop from apogee. Depending on a lot of factors, you could have a large drogue or a very small one. In either case don't add the drogue to the decent rate calculation for the main. Don't reduce the main size based on drogue size. You don't have to have an exact speed for touch down. Slow is good!
 

rocketcharlie

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Thanks guys. I am having trouble fitting a 48" main chute in this MD rocket. I guess I was looking for a rationale to downsize it a bit. Not a good idea I know.
 

afadeev

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Thanks guys. I am having trouble fitting a 48" main chute in this MD rocket. I guess I was looking for a rationale to downsize it a bit. Not a good idea I know.
A better solution to chute packaging challenges is to get a thin-mil chute of similar size, or another design chute (X-chute, Prabolic, Disk-band, etc) that achieves the desired descent speed.

Here are a few links to get you started:
 

AfterBurners

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You can probably downsize main by replacing it with a large rock or bowling ball but keep the drogue.:p:p:p I'm teasin. Keep the main but going with a thin mill chute may solve your packing issues.
 
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