When to deploy main?

[Dave A]

I tend to deploy mains probably sooner than most but I have a few questions.
I'm setting several altimeter bays and wanted some feedback.

What altitude do your deploy mains? (standard chutes, no bag):

4" rockets around 15-20 lbs?

6"-9" rockets around 45-70 lbs?

If you do these differently.

 

[3stoogesrocketry]

I tend to deploy mains probably sooner than most but I have a few questions.
I'm setting several altimeter bays and wanted some feedback.

What altitude do your deploy mains? (standard chutes, no bag):

4" rockets around 15-20 lbs?

6"-9" rockets around 45-70 lbs?

If you do these differently.

Before they hit the ground. I deploy most at 400 feet . My 4 inch 18 pounder pops a top flight 120 inch chute at 400 and is fully inflated within about 50/75 feet. Even my 100 plus pound boat anchors will blow the 20 foot main around 600 feet. It completely depends on your ability to pack a chute , how the rocket is falling ( under drouge or free fall ) and your charge sizes .

Eric

 

[rharshberger]

Non D-bag deploy I add 100' feet or so to my deployment altitude. The method of folding chutes I use ( I learned from a video on folding competition chutes) opens pretty quickly usually in less than the 100', based on my altimeter data (charge altitude fired vs main descent rate start altitude). Bigger rockets than 4" get D-bag setups, generally though everything gets a 500' main now that I am confident in my gear and packing methods.

 

[Eric]

I do all of mine at 500' or with heavier/faster falling rockets at the 600' and set the backup altimeter 100' lower.

I always set the Chute Release lower since all of the gear is already out of the tube.

 

[jsdemar]

Remember to take into account the terrain of the area you launch at. If the main deploys over a higher elevation, it may be too late.

 

[cbrarick]

No coward here. big rockets 600, 4 inch 400 and anything smaller 200. Wish I could get a stratologger to do lower.
No D-bags or pistons. Just correctly packed chutes and nomex.

 

[rharshberger]

I always forget about the release altitude for my Jolly Logic Chute Release, thats almost invariably set at 300'.

 

[Steve Shannon]

I do everything at 500’. There’s a 70’ hill a quarter mile away on my home field. Nothing higher for miles.

 

[rharshberger]

I do everything at 500’. There’s a 70’ hill a quarter mile away on my home field. Nothing higher for miles.

Same here for us, we might have 20' from pad height to top of hill level, then nothing tall for literally 5 miles or more.

 

[mpitfield]

Depends on where and what I fly. If I fly at Potter, whcih is mostly but not always where I fly, it is surrounded by higher hills and I tend to try to kiss the 18k waiver most flights. In this case I typically set main for 700 with the backup at 500. If I think the rocket might drift out of range, which it often does, and it drifts to towards the higher hills then that 700 is closer to 5-400 and the 500 is closer to 3-200. If it's a slow and low, 8K or less, then I will pop it as low as 300 but mostly 500. Having said that I also take into account wind. If it is on the higher side then I might take a 100-200 off.

 

[cerving]

500' for most rockets going under 7K, 700' for 7K-12K, 1000' for anything higher than that (with a 17K waiver). This is based on how far away from the pad it's likely to be... if you deploy it higher there's a better chance that you'll spot it on the way down, and a few hundred feet doesn't amount to a hill of beans in terms of drift. Of course, with an Eggfinder that should be a moot point, but it's still nice to see it on the way down

 

[JDcluster]

Most of my rockets ( 2" to 4" dia) usually 700 to 500 ft.
on bigger rockets, 4.5" and up; I go 1000 to 600 ft

 

[JoeG]

500' main with back up at 400' on most everything. On new rockets with any changes in harness from normal I might go to 700' but once I see it work properly go back down to 500'. At Black Rock and Air Fest I will use the 700' to maybe better catch a glimpse on the way down. No drogue. Ever.

 

[DaveW6DPS]

I always set the main for at least 500 feet, to allow deployment, deceleration, and a few second to spot it if it is out any distance.

Heavier rockets maybe 700 to allow more time to decelerate.

 

[roytyson]

Heavier rockets maybe 700 to allow more time to decelerate.[/QUOTE]

Time to decelerate? Doesn't terminal velocity happen in less than 1 second after the chute fully inflates? I agree you need ample time for the chute to inflate, but I was under the assumption that once inflated, that it will not slow down much if any after that point.

 

[GrouchoDuke]

For us folks who fly near mountains, it sure would be nice if flight computers had an integrated GPS and terrain database that would deploy the main at a given AGL over the current lat/long. Five hundred feet above the launch tower on a dry lakebed is great, but if it drifts over the mountains that'd ruin my day. Since no one offers that yet, I usually set mine pretty high when doing high altitude flights (over the highest peak within 10 miles?).

(*Ahem* Altus Metrum, Eggtimer, Featherweight, Missile Works, Jolly Logic, etc.)

 

[OverTheTop]

Most of my 3" or 4" rockets get main at around 1800'. Plenty of time to get a chute out, including the delayed main backup charge, if it is coming in at 300mph (ballistic) from apogee. Only happened once but I count the final outcome as nominal as final landing under main was nominal. The extra time also guarantees GPS packets for location data.

Remember to design for off-nominal situations. No flying fenceposts please .

 

[cerving]

For us folks who fly near mountains, it sure would be nice if flight computers had an integrated GPS and terrain database that would deploy the main at a given AGL over the current lat/long. Five hundred feet above the launch tower on a dry lakebed is great, but if it drifts over the mountains that'd ruin my day. Since no one offers that yet, I usually set mine pretty high when doing high altitude flights (over the highest peak within 10 miles?).

(*Ahem* Altus Metrum, Eggtimer, Featherweight, Missile Works, Jolly Logic, etc.)

Interesting idea, but if your deployment doesn't take you over the top of the mountain to the other side (where the terrain is supposedly friendlier for recovery) then it probably wouldn't matter. Your drogue velocity should be high enough to shorten your descent time but not so high that damage to the rocket is inevitable if the main doesn't pop. I've had one deployment where the main came out just after the drogue (loose shear pins), and it drifted 5 1/2 miles away over the backside of some hills, landing on a nice flat spot of desert between the sagebrush. I was REALLY glad that it drifted as far as it did... the hills were basically covered in boulders, recovering the rocket from that would have been very difficult if not impossible.

 

[ksaves2]

Most of my 3" or 4" rockets get main at around 1800'. Plenty of time to get a chute out, including the delayed main backup charge, if it is coming in at 300mph (ballistic) from apogee. Only happened once but I count the final outcome as nominal as final landing under main was nominal. The extra time also guarantees GPS packets for location data.

Remember to design for off-nominal situations. No flying fenceposts please .

Listen to OTP. Blow the main as high as the venue can tolerate. Doing lower can lend to a smackdown that's visible. Rf propagates better at altitude mostly so's better to get a fix/bearing or lat/long via GPS.

The 900mhz GPS trackers work better when slowly drifting under the main chute whereas a tumbling rocket at range has antenna polarity issues with the receiver that are exacerbated by low power and distance.

Kurt

 

[seth_cooper]

Main at 500'

300' with Chute release

 

[JohnCoker]

I'd say it depends on how flat and hard the landing surface is. Flying in the desert, I generally set the main to 1000'. That ensures it will be fully inflated. (There are no trees to get hung up on.)

 

[Dave A]

Mostly I fly at MDRA-Sod Fam and Culpeper, lower is better to avoid trees and cows!
MDRA-Higgs Farm, much bigger field, but deploying higher means longer walk with 80# rocket on a slightly windy day.
Thanks everyone for the input, this helps!
Happy New Year!!!

 

[GrouchoDuke]

Interesting idea, but if your deployment doesn't take you over the top of the mountain to the other side (where the terrain is supposedly friendlier for recovery) then it probably wouldn't matter. Your drogue velocity should be high enough to shorten your descent time but not so high that damage to the rocket is inevitable if the main doesn't pop. I've had one deployment where the main came out just after the drogue (loose shear pins), and it drifted 5 1/2 miles away over the backside of some hills, landing on a nice flat spot of desert between the sagebrush. I was REALLY glad that it drifted as far as it did... the hills were basically covered in boulders, recovering the rocket from that would have been very difficult if not impossible.

Yeah, I think I saw that launch of yours (here in Vegas...?). As many feature requests go, we're talking an edge case that wouldn't matter to most fliers (so, I'm jumping down a rabbit hole derailing the thread...).

I think it'd be nice to have that feature for places like Vegas & Delamar. Jean Dry Lake near Vegas has terrain that rises about 1000' within 3 miles (with a sweet soft flat spot on the other side). Delamar Dry Lake has terrain about 1500' high within 5 miles. At Delamar with a 50k waiver, a perfect 50k flight with average winds aloft of 30mph would make you drift roughly 3 miles under drogue. A 100-200k launch at Black Rock could run into similar problems with the rising terrain near there. So, we just need a GPS, enough onboard storage for a terrain database and enough processing power to crunch everything.

 

[MClark]

Higher the better. Gives more time to see the rocket in the air.

 

[cbrarick]

Higher the better. Gives more time to see the rocket in the air.

Or watch it drift away....

 

[rharshberger]

Or watch it drift away....

Especially with the wind we have generally pushing at least 10mph at ground level, coupled with the rolling terrain (+ or - 30 or so feet), and the scattered corn fields, potato and alfalfa fields (they do a great job of hiding down rockets), get the rocket on the ground as quickly as possible. Each venue has its recommended recovery situations, and it also depends on how much you like to walk.

 

[tim cubbedge]

Most of my 3" or 4" rockets get main at around 1800'. Plenty of time to get a chute out, including the delayed main backup charge, if it is coming in at 300mph (ballistic) from apogee. Only happened once but I count the final outcome as nominal as final landing under main was nominal. The extra time also guarantees GPS packets for location data.

Remember to design for off-nominal situations. No flying fenceposts please .

I can see that if you’re flying extreme altitude & terrain but if you’re only flying 5-10k on flat land, most people I fly with pop the main at 500-600’. Heavier rockets maybe 700-800’.

 

[jsdemar]

I am seeing a dichotomy of opinions between Western rocket people and "the others". ;-)

 

[cbrarick]

It appears that the western people don't have to worry about where they land, where on the east, it's the most important part of the deal....

 

[Banzai88]

It appears that the western people don't have to worry about where they land, where on the east, it's the most important part of the deal....

Yup. With variable wind speeds at different altitudes and SWAMPS and TREES everywhere.........it's prudent to know how to "fly the field". That means knowing how/when to pop the 'chute as much as what motor to pick.