Dual deployment minimum altitude

[RocketTree]

What is recommended minimum altitude for dual deployment?

I am ready to start using dual deployment. Instead of risking some of my larger (4 inch) DD rockets, I will be practicing on a BT60 Star Orbiter clone until I'm comfortable with it. The rocket has av-bay with Bear Altimeter and 9V battery. What is the lowest altitude you would recommend experimenting/practicing dual deployment?

 

[Steve Shannon]

I wouldn’t go less than 500 feet. Depending on how you prepare your chute it can easily take 250 feet to completely unfurl.

 

[dhbarr]

I guess that really depends on the size and type of your field, as well as how dense the rocket is vs. how large the canopy.

When I try a new piece of electronics, I tend to start about 2/3 of the way up between min and max; but I mostly fly on soft stuff with wide open spaces.

 

[manixFan]

If you mean min/max altitude I would shoot for at least 1000 ft., with the main set for 300’-500’. That will give you time to observe how a rocket behaves under drogue and low enough for the main for you to see what happens. For normal HPR rockets I generally don’t go below 500’ for the main but for a smaller, lighter rocket you should be ok.

Good luck,

Tony

 

[Zeus-cat]

I look at my Stratologger data after every flight. Main is usually set to deploy at 500 feet, but it can drop another 200 feet for the rocket to slow down to final descent speed. I wouldn't set a deployment altitude below 500 feet unless your conditions demand it.

Years ago I tested dual deploy using a MAWD with a rocket that only hit 300 feet. The deployment altitude was 500 feet, but it still worked. Both charges went off at the same time at the low apogee. I don't recommend doing that, but I guess it really depends on what pucker factor you can deal with.

 

[waltr]

Also check the Altimeter Specs as to the Minimum altitude (LDA, Launch Detect Arm, or what ever the altimeter maker calls it) it needs to fully Arm.
The Eggtimer Quark & Quantum I use will not arm if the rocket does NOT go above 200'. With the possibility of weather-cocking or not going straight up I try for a predicted altitude if 3-4 times the LDA.

Next as manixFan said: keep low enough to see the drogue and Main deployment. Important to observe how the booster & payload stay apart from each other under the Drogue.

Last is what altitude to deploy Main. A BT60 size rocekt with a nylon chute in a nomex blancket should have the chute open in a short distance. I set main at 300' on my BT50 through BT60 raockets using the Quark.
With a eggtimer Quantum in a LOC 2.2" IRIS, Main deploys at 250'. Rocket weighs 1kg, Drogue is 12" and main is 24". Main opens with plenty of time (height) to slow to a soft landing.

I try to do 500-800 feet on first flights.

 

[Voyager1]

What is recommended minimum altitude for dual deployment?

I am ready to start using dual deployment. Instead of risking some of my larger (4 inch) DD rockets, I will be practicing on a BT60 Star Orbiter clone until I'm comfortable with it. The rocket has av-bay with Bear Altimeter and 9V battery. What is the lowest altitude you would recommend experimenting/practicing dual deployment?

I use redundant dual deployment these days. For the main chute I typically use 600'-700' for the primary deployment event and no less than 500' for the secondary event. As mentioned by Zeus-cat, the chute might require up to 200' to deploy fully, so I wouldn't use lower than 500' unless there was a very good reason at the time.

 

[manixFan]

Also check the Altimeter Specs as to the Minimum altitude (LDA, Launch Detect Arm, or what ever the altimeter maker calls it) it needs to fully Arm.
The Eggtimer Quark & Quantum I use will not arm if the rocket does NOT go above 200'. With the possibility of weather-cocking or not going straight up I try for a predicted altitude if 3-4 times the LDA.

Next as manixFan said: keep low enough to see the drogue and Main deployment. Important to observe how the booster & payload stay apart from each other under the Drogue.

Last is what altitude to deploy Main. A BT60 size rocekt with a nylon chute in a nomex blancket should have the chute open in a short distance. I set main at 300' on my BT50 through BT60 raockets using the Quark.
With a eggtimer Quantum in a LOC 2.2" IRIS, Main deploys at 250'. Rocket weighs 1kg, Drogue is 12" and main is 24". Main opens with plenty of time (height) to slow to a soft landing.

I try to do 500-800 feet on first flights.

Not to create a circular quote, but your point about it being a small lightweight rocket is important in being able to set the main to open at a lower altitude than would be more typical of a heavier, larger HPR rocket. The Star Orbiter can fly on E and F motors, so opening below 500 feet should not be an issue in terms of needing several hundred feet to deploy the chute.

On my big flights - like a 6" rocket, I typically set the main at 1,200'. As size and weight increase, so should the main chute altitude.


Tony

 

[JoePfeiffer]

Depends on the parachute, which in turn depends on the weight of the rocket. I've got a lightweight 2.6" cardboard rocket where I set the main at 200'. I've been part of a team launching a 165lb rocket; on that one we set it for 1500' because the chute may take a while to open.

 

[ghuber]

In learning/practicing dual deploy, I used a BT60-sized scratch built rocket flying on Estes Ds that flew to 250 feet max and had the main deploy at 100 feet. The altimeter was an eggtimer quantum in a midbody coupler (A length of body tube with each end a 3-d printed coupler-sized ring that went into the main body tube). Per the above, I turned the launch detect altitude down to 100 feet. These were short flights, but it helped me learn a lot. I believe the drogue was a streamer and the main was a little 6" or 9" nylon chute.

 

[waltr]

Yes, it does depend on rocket weight, Drogue chute size, etc.
Which is why I stated that info. Too many posts on this topic do not state rocket stats therefore suggestions can be mis-leading.

Good to know the LDA can be turned lower on the Quantum, That makes in great for lower apogee flights on smaller fields and to do first DD flights.

 

[Handeman]

My first HiAlt45 had a jumper to set the main for 400 ft. That has become my standard on all my DD flights, except my L3 flights. Never had an issue.

 

[cerving]

Yes, it does depend on rocket weight, Drogue chute size, etc.
Which is why I stated that info. Too many posts on this topic do not state rocket stats therefore suggestions can be mis-leading.

Good to know the LDA can be turned lower on the Quantum, That makes in great for lower apogee flights on smaller fields and to do first DD flights.

You can turn the LDA down on the Quantum to 50', although I recommend 100' as a minimum. If your rocket doesn't make it to 100', it's probably because it either CATO'd, shredded, or looped, and parachutes aren't going to save your flight.

 

[waltr]

You can turn the LDA down on the Quantum to 50', although I recommend 100' as a minimum. If your rocket doesn't make it to 100', it's probably because it either CATO'd, shredded, or looped, and parachutes aren't going to save your flight.

thanks Cris. 100' sounds reasonable.
I have had two flights with a Quark that didn't go high enough to LDA.
On one the rocket bound on a launch rod partially so didn't get to 200' but motor ejected drogue.
Second was a Qjet nozzle failure that sent the rocket nearly horizontial at about 100 feet. Never fired Main and failed Qjet didn't fire drogue. Came in ballistic somewhere way out in the corn or woods and was never found. If the Main or drogue ejected there would be a better chance to find it.

 

[gtg738w]

Depends a bit on what you are trying to test. If you just want to test the electronics, you have a lot of flexibility with a kit that size. If you up the drogue size it won't matter too much if the main doesn't fully open. I've flown down to 200' on smaller sizes and they do just fine. Small chutes open very quickly compared to what most DD flights use. If you have the bay space you can even switch the main & drogue for the first flight. You basically get a single deploy flight with the main at apogee and the second event just verifies everything is setup correctly. With a motor backup, you still get a safe recovery even if the altimeter does nothing at all. If you want to measure the descent rate in a specific config you will need more time (before landing or between events) for everything to stabilize.

 

[Not Quite Nominal]

Real simple answer: as low as you'd be willing to go for apogee deploy for that rocket, plus a little bit.

Bigger parachutes/thicker material takes longer to inflate. Higher drogue speeds mean more distance covered during inflation time. On the other hand, modroc parachutes will inflate fully when tossed out a second story window, and modrocs have so much body drag they don't come down fast even drogueless.

A heavy fiberglass rocket might require over 1000ft to safely open/decelerate.

I made a DD Der Red Max with an EasyMini, and set it to pop the main lower and lower every flight. I downloaded the data from the EasyMini and the rocket never took more than 30-40 ft to inflate the main and decelerate.

Lowest I was willing to go was 100ft, and it was great. Dual deploy on a Quest C12 in a park!