Recovery question

I'm still digging into a cold-release mechanism (or minimally pyrotechnic)
for main chute deployment, and while I've found a couple items (Blacksky's &
Defy Gravity's) neither is quite what I want... overkill for my application.
The DefyGravity tether looks like it would blow my 4" rocket apart, and
Blacksky's rig seems overly complex (and pricey). Lacking any other method
I'll use a parachute burrito, but I have a "vision" of what I want to
accomplish, and that isn't it.
I've a couple ideas, but one key thing I don't really know.... what is the
actual load on a parachute during descent? Is it simply the weight of the
rocket? I understand that transient stresses and shock loading will be more
than that (perhaps substantially more), but the working, constant load is my
interest. If the load is simply the weight of the rocket, then a cold
release mechanism for a rocket weighing 5 pounds is not a big deal.
Has anyone ever done a system in which the main chute is deployed but
reefed, acting as a drogue until deployment altitude, when a sliding reef is
released and the chute allowed to fill? Not sure it could be easily
accomplished, but heck, I figure it doesn't hurt to ask,...
Can anyone point me to a "parachute geeks" book or page so I can get
seriously silly about this issue? I've looked at many of the rocketry
related sites but have not found the depth of info I desire.
TIA for any suggestions.
Kevin OClassen
NAR 13578
Reply to
Kevin OClassen
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application.
I've done that. The drogue was tied to the top of the main parachute canopy. At this place a hook was retained by a lock mechanism that was unlocked by a servo. The system worked well but last flight crashed. Don't know if I have pictures of the release mechanism... By the way, the rocket weight was more than 40 pounds.
Reply to
michel
I've used the Tether in a BSD Horizon 4" in the "burrito" mode.
Take a look at The Parachute Recovery Systems Design Manual by T.W. Knacke about half way down the page at
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and see what you think. I'm reading it now and it seems good.
Kev...
Reply to
Will Marchant
If I remember, Knacke's book was originally developed as a US Navy manual. It is by far the best book on recovery systems and general knowledge, available. Although the designs and information presented are quite detailed and in most cases exceed the requirements of most HPR rockets, except more complex designs, the principles and information can be used to understand and design a good HPR recovery system. My copy has lots of dog ears. For me, the up part of a rocket launch is cool, but a well designed and functioning staged recovery system is really cool.
Fred
Will Marchant wrote: > > I've used the Tether in a BSD Horizon 4" in the "burrito" mode. > > Take a look at The Parachute Recovery Systems Design Manual by T.W. > Knacke about half way down the page at >
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and see what you > think. I'm reading it now and it seems good. > > Kev> ... > > The DefyGravity tether looks like it would blow my 4" rocket apart, and > ... > > Can anyone point me to a "parachute geeks" book or page so I can get > ... > > -- > Will Marchant, NAR 13356, Tripoli 10125 L2 > snipped-for-privacy@amsat.org
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Reply to
WallaceF
I have done that method entirely electronics free (many moons ago) with a burn string. The system works just fine that way. I suppose you could also use electronics and a "minimally pyrotechnic "piston style line cutter" as well.
Reply to
Jerry Irvine
How about doing something technically interesting for a change, and list the "top ten dog ears".
Just a suggestion from the people at Jerry.
Reply to
Jerry Irvine
kevin: have you seen this:
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you can use either an altimeter ot timer to fire an ematch or similar igniter that releases the piston.... almost totally non-pyrotechnic
shockie B)
Reply to
shockwaveriderz
pyrotechnic)
(Blacksky's &
application.
Hello Kevin:
IMHO Defy Gravity's Tether is the best thing since sliced bread. I've used Tether on two different 4" rockets. On the second rocket, "apogee" deployment of the main occurred at some time before apogee.... apparently a problem with the altimeter. Even so, Tether held the main until the rocket dropped to 800 ft, then released it as pretty as you please.
One thing I REEEEALLY like about Tether is that it takes less than a quarter-gram of BP for deployment of the mains. None of them five-gram or ten-gram charges to deal with.
I expect to use Tether on most of my future high-power flights.
Best regards -- Terry
Reply to
prfesser
I want to thank all who responded and have provided food for thought. The Knacke book is on order, and I'm playing with a number of ideas to achieve what I'd like to see (i.e. "drogue pulls the main"). LOL-- I read the Tether manual, and it looks great for certain applications, especially when it is used outside the airframe on the recovery harness, but I do want a system where the release mechanism for the main is inside the airframe. I took their warnings about mounting to avoid damage to heart, and am looking for somehting a little less "active". The movie of the Tether dropping the tire was the clincher :)
The servo-driven ejection mechanism has potential, even if only for the use of a servomotor for the release mechanism and the related circutry. I'm thinking if it can release under the described spring load, it may well release under the static parachute load.
I guess the real answer is to build a few prototypes and see what works.
Thanks again to all.
Kevin OClassen NAR 13578
Reply to
Kevin OClassen
Hi.
I really think you will find the tether to work better then the servo.
if you really are worried about damage due to the tether, line the inside of your 4" payload tube with an extra tubing coupler just as extra protection, just in case.
Reply to
AlMax
Guys who aerotow large model sailplanes use a servo actuated mechanism to release the tow line from the nose of large 6 meter span gliders with relatively small mechanisms.
I don't know exactly how this one works but it says it works off of small servos..
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The ones at this page look more like the duty for a drogue/main
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The problem I see is that you have to run a servo off of a timer/altimeter.
Reply to
Thomas Koszuta
I developed a small schematic to control a servo (two positions) either with a timer on the same board or an external one.
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timer/altimeter.
pyrotechnic)
Reply to
michel
Care to help out those of us who are electronically deficient? I've seen one rig using two 555 timers, but am interested in anything that might work.
Kevin
Reply to
Kevin OClassen
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The '08M' can control a servo, and the system is very easy to use. You just need the cable (about £3.50) and free software to get started.
Reply to
Niall Oswald
My shematic uses one 4093. I also had a version with a microcontroller, but I didn't like it because it was difficult to change the positions of the servo on the field, without bringing a laptop. I'm interested in the version with two 555, btw. Michel
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Reply to
michel
Servo, meaning it would be possible to activate it by radio control(from the ground)? Sorry if that sounds like a dumb idea, but that's the first thing I thought of when I read "servo"...
Eldred
Reply to
Eldred Pickett

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