sizing drogues

rocket sok
SilicdyneTRF
shop deals on amazon
Onebadhawk
The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
watermelonman

watermelonman

Well-Known Member
Joined
Sep 22, 2014
Messages
2,597
Reaction score
10
What rhyme or reason do people use when sizing drogue parachutes? I have been using guess and check.

What can happen when using a drogue that is too small? Is it more likely to tear or not hold open properly?
 
A drogue too small will still open and shouldn't be damaged by the flight. They deploy at apogee and at low speeds. The issue with too small of drogue is it doesn't keep the payload section above the fin can. When the fin can is above the payload the chances of the fin can fouling the main go up. I usually increase/decrease the size of my drogues until it keeps the payload just above the fin can, but not with so much drag that the fin can and payload are both hanging straight below the drogue. I look for the fin can to fall pretty much on its own, but always below the payload section.
 
Handeman said:
A drogue too small will still open and shouldn't be damaged by the flight. They deploy at apogee and at low speeds. The issue with too small of drogue is it doesn't keep the payload section above the fin can. When the fin can is above the payload the chances of the fin can fouling the main go up. I usually increase/decrease the size of my drogues until it keeps the payload just above the fin can, but not with so much drag that the fin can and payload are both hanging straight below the drogue. I look for the fin can to fall pretty much on its own, but always below the payload section.
Click to expand...

+1.....

The booster and the payload section / av bay / nose cone should make an inverted "V" while falling from apogee........

If they're falling in a vertical straight line the drogue is too large,,, too much drag....

If they're either falling flat in a horizontal straight line
or worse in a vertical straight line nose cone down fins up booster being dragged down by the mass of the streamlined payload section / av bay / nose cone
Then the drogue is too small,,, not enough drag.....

Teddy
 
That's a question I've struggled with. How do you set the initial size of the drogue chute before a test flight? Do you sim the booster and forward section (AV bay, payload section, nosecone) individually and compare descent rates? I've tried to watch my dual-deploy flights to garner this information, but I just can't see them well enough to know if a 12" drogue is better than a 9" or 15"...
 
With my drogues, I have been using Rocketman's drogue descent rate chart. Using the weight of my rocket, I can see approximately how fast my rocket descends under drogue and pick a size that will keep the rocket at a descent rate (FPS) that I am comfortable deploying the main at. Of course, this chart is based on using a Rocketman chute for a drogue. Check out their kevlar chutes as drogues.
 
You can simulate a drogue in OR. Resize the parachute and run a sim. It will tell what the descent rate is. It's probably going to be higher than reality since the rocket will probably fall horizontally but at least you know it will be coming down at a reasonable rate.
 
There's lotsa folks that fly drogueless and do it well.

IMHO just keep the stuff that deploys the main on top during descent and you're golden.
 
ChrisAttebery said:
You can simulate a drogue in OR. Resize the parachute and run a sim. It will tell what the descent rate is. It's probably going to be higher than reality since the rocket will probably fall horizontally but at least you know it will be coming down at a reasonable rate.
Click to expand...

That's a great idea,,, duuhh,, I never thought of that....


[QUOTE
There's lotsa folks that fly drogueless and do it well.

IMHO just keep the stuff that deploys the main on top during descent and you're golden.][/QUOTE]

That's a different way of wording it,,,
I like this way a lot...
What you're trying to accomplish is to have the payload section over the booster when deployment occurs...

Teddy
 
Drogueless I s fine up to a certain size. The key is keeping the top of the rocket above the aft. I do both drogueless and drogueless depending on the rocket.
 

Similar threads

SuperNova-Rocketry
Questions about streamers
Replies
24
Views
952
bad_idea
bad_idea
SuperNova-Rocketry
2 parachutes exiting from the nose cone
Replies
15
Views
642
SolarYellow
SolarYellow
H
Questions regarding equations for calculating the force of a parachute opening.
Replies
24
Views
1K
Spacedog49Krell
Spacedog49Krell
DaHabes
  • Poll
Recovery Harness Attachment
Replies
1
Views
517
Handeman
Handeman
SolarYellow
Very small nylon parachutes?
Replies
11
Views
594
3stoogesrocketry
3stoogesrocketry

Latest posts

Back
Top