500 lb rocket recovery

[jessemarder]

Hello,
I am working on a rocket that will utilize a pressure-fed liquid propellant (LOX/Ethanol) motor to propel it. Total weight will be in the 400-600lb range, height >20ft. We're thinking it will go around 5 miles up.
My question is how would you suggest we perform the recovery? I assume dual deployment is the way to go, though I'm unsure about the sizes of the parachutes needed. Based on a 15fps descent rate, it looks like we'd need a main greater than 50 feet in diameter! Also, is it fine to just scale up the DD system you might use in a smaller rocket?
I haven't been able to find any examples of "hobby/model" rockets of this size but if anyone knows of any, with details on its recovery system, I would be very interested.
Any input would be appreciated.

Thanks,
Jesse

[ClayD]

Hello,
I am working on a rocket that will utilize a pressure-fed liquid propellant (LOX/Ethanol) motor to propel it. Total weight will be in the 400-600lb range, height >20ft. We're thinking it will go around 5 miles up.
My question is how would you suggest we perform the recovery? I assume dual deployment is the way to go, though I'm unsure about the sizes of the parachutes needed. Based on a 15fps descent rate, it looks like we'd need a main greater than 50 feet in diameter! Also, is it fine to just scale up the DD system you might use in a smaller rocket?
I haven't been able to find any examples of "hobby/model" rockets of this size but if anyone knows of any, with details on its recovery system, I would be very interested.
Any input would be appreciated.

Thanks,
Jesse

Jesse, I would look to some of the amature clubs for personal mentoring on this.

the vehicle you describe, would be - of verry high impulse, and likewise a very complex vehicle.

I think it is way too complex for a "recovery" thread.

But, One idea you may look into, is rocket propelled parachutes, like BRS systems. they make teathers that can deploy anything from 20 to 80' parachutes to recover anything from a hanglider up to a 6 place aircraft. and they do it reliably and consistantly.

I wouldnt think of using something like "hope and pray" dual deploy on a 200lb rocket at 30,000ft, let alone a 500#'er.

[rstaff3]

That size rocket is rare in our hobby but not unheard of. However, I don't know how many people who are knowledgeable about such a project read this forum.

Although Steve Eves' Saturn V only (almost) scratched a mile of altitude, it's loaded weight was over 1500 lbs. Steve might be a good source. Ky Michaelson would be worth contacting. Hmmm, I know there are others but the names don't come to mind at the moment.

[cjl]

Dirk Gates would probably be a good contact as well.

[AlphaHybrids]

Kevin Trojanowski would also be a good contact. He's troj on here. He has a lot of experience with big projects.

Edward

[rstaff3]

Yeah, Ky would be a good place to start. He worked on the CSXT Go Fast. 724 lbs. 72 miles altitude.

http://www.ddeville.com/derek/CSXT.htm

[cjl]

Did he do the recovery though? I'll be honest, I've been less than impressed with the recovery record of some of Ky's projects. I think Kevin or Dirk (or Steve Eves for that matter) would be a better choice.

[troj]

Do you plan to recover in one piece, or in multiple pieces?

A C-9 (28 foot man-rated ejection seat parachute used in the B-1, A-10, and several other aircraft) is good for 120 - 140lbs, at a standard recovery rate for what we do.

We recover our projects with a combination of 24 footers and 28 footers, all man-rated military surplus. They can be found, but finding a good one, with lines, is difficult. Re-lining them properly is a very expensive proposition -- just sewing little loops on the end, and attaching lines is not proper re-lining, and I wouldn't trust them with a full load, if done with loops.

If you look around, you can periodically find 64 and 100 foot cargo parachutes; they're really hard to find with lines, but it can be done. If you need to recover in one piece, that's really what you're looking at.

For a parachute in the size you're looking at, you need someone who has a clue what they're doing to design and build a complete recovery system, from the harnesses, to the deployment bags, up through the pilot chutes.

We're fortunate that one of our team members is an FAA licensed Senior Rigger with a tremendous amount of experience. He has the knowledge and the tools, and has pulled in people he knows with even more experience, to help design some of what we use.

BTW, I would not use Steve Eves Saturn V as an example -- that recovered as much on luck as anything else. And it gained one bodacious zipper along the way.

-Kevin

[bobkrech]

Hello,
I am working on a rocket that will utilize a pressure-fed liquid propellant (LOX/Ethanol) motor to propel it. Total weight will be in the 400-600lb range, height >20ft. We're thinking it will go around 5 miles up.
My question is how would you suggest we perform the recovery? I assume dual deployment is the way to go, though I'm unsure about the sizes of the parachutes needed. Based on a 15fps descent rate, it looks like we'd need a main greater than 50 feet in diameter! Also, is it fine to just scale up the DD system you might use in a smaller rocket?
I haven't been able to find any examples of "hobby/model" rockets of this size but if anyone knows of any, with details on its recovery system, I would be very interested.
Any input would be appreciated.

Thanks,
Jesse

You need to use professional recovery techniques for rockets of this size, not hobby rocket stuff.

http://www.mrc.uidaho.edu/~atkinson/...ent%20Wolf.pdf

This is the bible of parachutes and recovery. http://openlibrary.org/books/OL15624...covery_systems This book is downloadable from other sites. Do a google seach.

http://www.nakka-rocketry.net/sp8000.html These are good references for larger vehicles.

Bob

[jessemarder]

Is it weight that determines how sophisticated the recovery system needs to be? We may be able to get the weight down to 400 lb. We'd like to put this together using reasonably standard materials, like Aerocon 28' parachutes, an RRC2-mini and a Featherweight Raven. Also, if we split the recovery up (nose cone separate from payload/body tube) wouldn't that simplify things?

I very much appreciate all of your replies and suggestions and will definitely take them to heart.
Thanks,
Jesse

[troj]

Is it weight that determines how sophisticated the recovery system needs to be?

Yep. For two reasons...

First, it's a safety thing -- the risk of a 500lb rocket coming in with no recovery are much higher than a 5lb rocket.

Second, the stresses involved are significantly different. Lots of people can recover a 10lb rocket. The same techniques do not scale to a 100 or 200lb rocket, and what works on a 100lb rocket may not work on a 500lb rocket.

We may be able to get the weight down to 400 lb.

Not a real significant drop in weight.

We'd like to put this together using reasonably standard materials, like Aerocon 28' parachutes, an RRC2-mini and a Featherweight Raven. Also, if we split the recovery up (nose cone separate from payload/body tube) wouldn't that simplify things?

Unless you're going to get it into individual pieces that weigh no more than 125 pounds each, forget the 28 foot parachutes.

And even so, a Raven, on its own, isn't going to do what you need.

You need a recovery expert for this project. Bob has pointed you to some good sources, but trust me, unless you're a very, very rare type, just reading it isn't going to give you the knowledge and experience you need to recover this beast.

You need a rigger.

-Kevin

[troj]

Oh, and to give you a basis of experience, we've flown four rockets in the 300+ pound range. Two had motor issues that prevented recovery from having a prayer, the other two recovered just fine -- one was 450 pounds on the pad, the other was 350 pounds on the pad.

The two failures were caused by 1) bad ignition sequence of outboards versus central, resulting in instability off the pad, and a disastrous flight profile, and 2) a motor issue coupled with placement of static ports that confused the altimeters, causing ejection while the motor was still burning.

-Kevin

[UPscaler]

snip

The two failures were caused by 1) bad ignition sequence of outboards versus central, resulting in instability off the pad, and a disastrous flight profile
-Kevin

Would that be the pershing?



Braden

[troj]

Would that be the pershing?

First Delta III flight and the Pershing.

On the first Delta flight, we made the mistake of trying to light everything at once. The boosters came up way faster than the P, in spite of thermite. The boosters were enough to lift the rocket, but not enough to get it stable.

The P finally kicked in as it was reaching the end of the rails, which was far too late. The rocket leaned over and went into cruise-missile mode. The altimeters behaved exactly as they're designed to; unfortunately, the rocket was moving far too fast, and we shredded the main on the lower section. The boosters, the upper section and the nose all recovered just fine, as they didn't have near the amount of inertia that the main did.

The Pershing was a different issue -- the motor "burped" about a second into the burn. It's visible on the video, and my wife got a photo of a nice black cloud beneath the rocket. The case almost let go.

When this happened, CFD sims show that the low pressure point over the static port moved, causing the altimeters to see an increase in pressure, and they did what they're designed to, which is fire the charges. Not good when you're about 1 second into an 8 second burn.

The drogue pulled the bagged 28' main for the upper section through the side of the airframe. The main then inflated, snapped two 3/8" steel cables, then disintigrated.

-Kevin

[cjl]

Of course, the Pershing mishap (based on that description) could have been prevented with a set of accelerometer-based altimeters, or even simply a proper mach delay...

[troj]

Of course, the Pershing mishap (based on that description) could have been prevented with a set of accelerometer-based altimeters, or even simply a proper mach delay...

Motor behaving properly, a different location for the static port, different altimeters, setting a Mach delay... It's quite possible any one of them would have prevent it.

-Kevin

[ClayD]

Motor behaving properly, a different location for the static port, different altimeters, setting a Mach delay... It's quite possible any one of them would have prevent it.

-Kevin

Foresight, is a privelage of few!

I guess, I dont understand. How could a milisecond burp do that?

[troj]

I guess, I dont understand. How could a milisecond burp do that?

Change in velocity moves the low pressure zones.

We found it in the altimeter data, and the CFD sims confirmed the cause.

Video, data and sims all line up.

-Kevin

[ClayD]

Change in velocity moves the low pressure zones.

We found it in the altimeter data, and the CFD sims confirmed the cause.

Video, data and sims all line up.

-Kevin

I am curous what the velocity was prior, and the actual amount of change from the burp. and how long it took to get back to the original velocity. If it had been MECO at that moment, wouldnt it have been a false deploy as well?...

Sounds like to me the port locations were the main failure, and probably would have fired early anyway at 1 or 8 seconds? Being in a location a low pressure is being generated by velocity.

Motor behaving properly, a different location for the static port, different altimeters, setting a Mach delay... It's quite possible any one of them would have prevent it.

I guess I am starting to see the answers to my questions, I guess I didnt realize the - sensitivity- of the barometric altimeters. I always thought it took at least 1/2 second of "falling" change before it would fire, not of of 1 or 2 200hz or 400hz readings.

I am deffinately not doubting your summation, it is agreeable to me, and thanks for the discussion.

[niels popping]

I think you can better use Chute mortars.

just a side panel in your rocket, where the parachute fits in.

that way you don't have to separate the nose from your rocket.

A saver recovery.

maybe with more side panels, its possible to use more chutes for your recovery.

[niels popping]

Foresight, is a privelage of few!

I guess, I dont understand. How could a milisecond burp do that?

More static ports each with his own altimeter, but the static ports isolated from each other.

place that static ports at the smooth surface of your rocket, where the airflow is laminar,
you can find the perfect place with a aerodynamic software, or wind-tunnel

what I always do, is connect the altimeter to a free-fall sensor, (really easy to made) that sensor switch when your rocket slowly falls back to earth.
and never fail to switch, because the earth gravity holds the magnet in place, but when your rocket is descending and your altimeters give the pulse to the sensor, the magnet push the button, that way your recovery is not to early,

[ClayD]

More static ports each with his own altimeter, but the static ports isolated from each other.

place that static ports at the smooth surface of your rocket, where the airflow is laminar,
you can find the perfect place with a aerodynamic software, or wind-tunnel

what I always do, is connect the altimeter to a free-fall sensor, (really easy to made) that sensor switch when your rocket slowly falls back to earth.
and never fail to switch, because the earth gravity holds the magnet in place, but when your rocket is descending and your altimeters give the pulse to the sensor, the magnet push the button, that way your recovery is not to early,

the only electronics i use, are accelerometer based, and deploy based on math calculations from measured acceloration and - time over deceloration.
they are also carrying baro metric sensors and can sense altitude change. using both sensors is called "dual based detection".
they are "or"ed, being that one or the other sensor will detect apogee, and fire the charges. I've had a 100% success rate with this set up, even when my baro output was stuck high voltage, and not reading any change - 0' altitude. Problem was it immediately puts out the main. but i have never had an early apogee charge.

the only "foreseeable" failure, is mach busting horizontally. the velocity will lock-out the barometer apogee... - this system wont break apart a rocket on a bullet path.

Kevin's, Purshing was definately a system flaw, I have a real problem accepting the answer of a BURP, to cause a false apogee detection. Irregular thrust is very common in larger motors(probably not so much to the level this rocket had), but a hardware manufacturer (altimeter maker) should have programming to forgive a slight gulp of pressure. Most barometric boards i see buffer to a 25ft resolution when detecting apogee(which equates to i think 1 atmosphere of change??). that would mean this burp caused one massive change in pressure over a fairly long period of time. 15psi? for 1/4 second? this is a big change and an eternity of time in 400mhz world.

I agree with the principal that the burp caused a change in port pressure - totally, but i think the electronics should have been set up to not be so dang unforgiving. remember,... a piece of tape or loose wire could do this same thing, even in a well placed port location.

[ClayD]

Irregular thrust is very common in larger motors(probably not so much to the level this rocket had), but a hardware manufacturer (altimeter maker) should have programming to forgive a slight gulp of pressure.

Engine anomolies are common, this is from a (not Q10,000-like Kevins was) Large M motor. As you can see, there were a few BURPS.. this was rather neat and fun to watch, (in fact when you watch the video, you can hear a series of thumps that correspond with the dropp in thrust). these were grains of fuel being chucked out of the nozzle. two grains were thrown, and are the steps you see at the end of the thrust. they made awesome fireballs exploding in the flame plume.

None of these burps caused a significant change in velocity other than an early meco, and an earlier deceloration, probably cost me a 1000 feet in altitude, and mach 1.4 instead of 1.6.

[cjl]

Most barometric boards i see buffer to a 25ft resolution when detecting apogee(which equates to i think 1 atmosphere of change??). that would mean this burp caused one massive change in pressure over a fairly long period of time. 15psi? for 1/4 second? this is a big change and an eternity of time in 400mhz world.

To see a 15 PSI change, you'd have to go from sea level to the upper atmosphere, so that's definitely not right. A 25 foot resolution means around a 100 Pa change, or roughly 1/1000 of an atmosphere (0.015 psi). It's a fairly small difference, honestly.

[troj]

Kevin's, Purshing was definately a system flaw, I have a real problem accepting the answer of a BURP, to cause a false apogee detection.

You can refuse to accept it all you want, but there's speculation based on what you know, and there's the hard facts that we know, based on seeing the evidence.

The "burp" as I call it was a clogged nozzle -- the motor was close to letting go, before it did its proverbial throat clearing. Every piece of data lines up with this being the trigger that set everything off.

Sorry, but refuse to accept want you want. We've analyzed data, rather than speculating without facts to work from.

Every single large flight we do, whether successful or not, we look at it afterwards, to find what worked and what needs improvement.

-Kevin

[ClayD]

You can refuse to accept it all you want, but there's speculation based on what you know, and there's the hard facts that we know, based on seeing the evidence.

The "burp" as I call it was a clogged nozzle -- the motor was close to letting go, before it did its proverbial throat clearing. Every piece of data lines up with this being the trigger that set everything off.

Sorry, but refuse to accept want you want. We've analyzed data, rather than speculating without facts to work from.

Every single large flight we do, whether successful or not, we look at it afterwards, to find what worked and what needs improvement.

-Kevin

I am not refuting your empirical data at all. And, I am quite sure if I saw the data, may come to the same conclusion.
My point is that the "flaw" that caused the event was the port location and the electronics used. simply put, this event would have happend at burnout or any time when the low area began to regain presure again.(going from what youve told me is occuring on the rocket) and is regardless of the "clogged nozzle".....

[troj]

...except that moving the ports would've required a significant change in how the rocket is built. Sometimes you run into constraints that force you to make certain decisions.

And if you go back and read my original description, I said that a different port location may well have prevented this from happening. However, if the motor hadn't suffered an anomaly, it wouldn't have been an issue.

System failures are often a chain of events. This is a perfect example of that -- change any one thing in that chain, and the failure doesn't happen.

-Kevin

[ClayD]

To see a 15 PSI change, you'd have to go from sea level to the upper atmosphere, so that's definitely not right. A 25 foot resolution means around a 100 Pa change, or roughly 1/1000 of an atmosphere (0.015 psi). It's a fairly small difference, honestly.

yes, thanks for reminding me.

However, the rate of change is large in scale to the resloution of the sensor. Most baro sensors measure at rates of 1 to 2 feet of altitude. So to buffer them to 25 feet, means a significant change occured.(as relates to the sensor)
In this instance, not a change from velocity gaining in altitude, but a change in increased pressure for a length of time for the electronics to detect apogee.

To me, the programming in the altimeter, should have had a slower resolution detecting apogee than it did.

[AlphaHybrids]

It is easy to armchair quarterback on Monday morning isn't it?

So, you'd like to see a delay in detecting apogee. So that way your rocket is on the way down and you have a higher chance of zipper. Awesome.

Isn't hindsight 20/20.

I trust Kevin (troj).

Edward

[ClayD]

...except that moving the ports would've required a significant change in how the rocket is built. Sometimes you run into constraints that force you to make certain decisions.

And if you go back and read my original description, I said that a different port location may well have prevented this from happening. However, if the motor hadn't suffered an anomaly, it wouldn't have been an issue.

System failures are often a chain of events. This is a perfect example of that -- change any one thing in that chain, and the failure doesn't happen.

-Kevin

So, why at 1 second does returning air pressure set of the charges, when at motor burnout returning air pressure not?

To me, a burp like this is going to stop accelloration, but be too brief to actually allow deceloration.

Since I dont have any data, nor did I witness it, your dead on I dont have standings to say what is or isnt. So, please understand I am trying to learn - from your mistake- and be discussive, not correct.