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Steerable drogue chute?

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Dan Griffing

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Has anyone thought about a steerable drogue chute?

Coming down from 20k feet a 4-axis controller — with a similar technology as 4-axis rocket canard rotation and vertical controller — could control the four shroud lines of a drogue chute as it descends at say, 70fps from 10k to the 1k main chute deployment.

Instead of coming down 3 miles away, 100 yards would make recovery much easier and observable by the spectators.

Some years ago Apogee Components had shown a video of a steerable main chute for small rocket but I never saw this come to market as an actual product.

But what I’m envisioning is a drogue for a 4” rocket that would deploy at much higher altitudes and come down faster.

If someone has already found the show-stopping impediments that keep something like this from working, it would be a useful discussion to have.
 

Dan Griffing

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It might make for a good, original, Level-3 project for some young, technically-skilled, engineer-type that would make a nice contribution to HPR, d’ya think?
 

Bat-mite

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Apogee Components is working on a steerable parasail, but it is designed as a main.
 

Ravenex

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I am working on this with a power kite as the main. The particular kite I'm using has a separate line that can partially or even fully collapse the kite to adjust decent rate to be used as both drogue and main. I have what I believe are robust reliable mechanics but the controls for autonomous steering are outside my abilities. I am currently working on this as an R/C solution for now within visual range and eventually I hope to fly it with a long range radio link and camera/telemetry.
 

AllDigital

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I thought about this a while back and also concluded that the main would be a lot easier to engineer. The challenge with the drogue is twofold, 1) the rate of fall often keeps you in GPS lock-out -- at a minimum you'd need to size your drogue to prevent lock-out or use some other method direction finding and 2) with a drogue there is still a LOT of spinning and thrashing of the airframe, making it harder to get a good compass bearing and get control of the glide path. By using the main both of these challenges get easier.
 

Tech 68

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Talked a bit about this with a good friend that also does a lot of R/C airplane flying. His concern would be the servos surviving the opening shock of the main.
Perhaps using a streamer of sorts in conjunction with the drogue might minimize the spinning... like the "tail" on a kite.
The military uses this capability for high risk cargo drops... Course, they have much deeper pockets than us.
 

Ravenex

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Talked a bit about this with a good friend that also does a lot of R/C airplane flying. His concern would be the servos surviving the opening shock of the main.
Perhaps using a streamer of sorts in conjunction with the drogue might minimize the spinning... like the "tail" on a kite.
The military uses this capability for high risk cargo drops... Course, they have much deeper pockets than us.
That is precisely the problem I have successfully fixed, my servos see none of those loads. In fact my servos have survived every flight even one where the opening shock tore the main kevlar.

 

Dan Griffing

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I thought about this a while back and also concluded that the main would be a lot easier to engineer. The challenge with the drogue is twofold, 1) the rate of fall often keeps you in GPS lock-out -- at a minimum you'd need to size your drogue to prevent lock-out or use some other method direction finding and 2) with a drogue there is still a LOT of spinning and thrashing of the airframe, making it harder to get a good compass bearing and get control of the glide path. By using the main both of these challenges get easier.
I’ve seen a number of high altitude flights where the Multitronix “Kate” GPS is used with dual deployment, and continually reports the altitude and down range location.

Is there something special going on here to prevent “GPS lockout”.

My surmise is that a precise GPS location isn’t necessary to know what compass heading is needed to come back to near the launch point.
 

AllDigital

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Altitude is easy, as it is just using a barometer. Kate is subject to the same lock-outs, although depending on the GPS and the descent velocity you might get GPS readings on the way down from 20K feet. With a drogue going 75 fps you likely will get some GPS data, but it isn't just about the drop rate it is about the spin rate confusing the GPS into thinking it is going much faster. Older GPS units had less rules and newer GPS units are often black boxes and don't always publish their velocity algorithms. Just about all GPS units lock-out on ascent, regain at apogee, and then descent under drogue is a mixed bag, descent under main is smooth sailing for a GPS.
 

VernK

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Kate is subject to the same lock-outs, although depending on the GPS and the descent velocity you might get GPS readings on the way down from 20K feet. With a drogue going 75 fps you likely will get some GPS data, but it isn't just about the drop rate it is about the spin rate confusing the GPS into thinking it is going much faster.
The Kate system has no trouble at all maintaining GPS lock during descent on drogue. Velocity lock out is not until almost 1700 feet per second. I have never seen a spin rate produce that kind of apparent speed. It also helps a lot to have a very good GPS antenna so that spinning does not disrupt the view of the satellite constellation too much.
 

VernK

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I have always wanted to build a steerable recovery system that would land a rocket somewhere near a designated spot. It always seemed to me that the electronics, including the GPS, was the easy part. I think the hard part is the mechanical aspect of the design. That being a steerable canopy and the control motors, pulleys or what ever is needed to steer it. Making all that small enough and light weight enough yet strong enough to do the job is a tough problem. Keeping the control lines from getting crossed or tangled when the chute deploys is also a tough problem. From what I have read and heard, just getting a steerable canopy to open reliably can be tricky. Especially if done at apogee where the conditions and orientations are not well controlled. Nevertheless, it would be a fun project to work on......
 

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This has been worked on for 30 years. Someday someone will get one to work.
 

Richard Dierking

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The problem with higher velocity descents (say 75 fps range) is that the system including the rocket airframe with fins, nose, and drogue parachute become only slightly organized. Small drogue chutes have chaotic movements and spill holes don't seem to help. I did testing around the 75 fps velocity. (btw, if you ever want to get the attention of local law enforcement, attach a rocket to the side of your truck and drive really fast.)

I created a rocket with a side deployment bay so the shock cord was attached to the CG of the rocket and it was a no-go. If you descend fast sideways the airframe and fins cause big problems for control.

Roll is the enemy of rocket control.

There's just so much info I have, but I should try and keep this short. I've included a couple photos. I'm not a fan of bringing rockets back to home. Probably enough rockets under chute hit vehicles already. I prefer 'recovery area.' Over time, I hope recovery areas become more defined and smaller. I also prefer to control directions and not go to destinations. Just my preference. My 'dream flight' would start leaning on the pad away from the spectator area, launch, and after some time pitch to up. The rocket turns at apogee and comes down controlled by the surfaces used to control up. Then, side drogues chutes deploy to slow for the main. Yup, the rocket after apogee would be coming down really fast before the drogues.

A couple photos are included below. The 2 control surfaces are designed to control roll orientation first, then pitch. The side bays deploy 2 small parachutes (9"). I would like to control the rocket a bit on the way down, but roll continues to be a serious problem after the drogues deploy.

I'm not presently a big fan of control canards on rockets. They bring the CP forward. And the ones I usually see are so large. Why so big? But, installing control surfaces at the aft end are difficult because the rocket has to be custom built.
Future commercial control surface systems will probably be canard systems. It would be so much easier to produce a canard system for other people to use. So, instead of controlling drogues, I believe controlling canards during descent would work better. And, if you had 4 you could actually slow the rocket before deploying the pre-main.

IMG_2828.jpg
IMG_2831.jpg
 

VernK

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Wouldn’t it be simpler to just deploy the main chute a bit higher and then steer it rather than trying to steer things during high speed descent or while on drogue?
 

Richard Dierking

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The "main" problem with deploying larger parachutes at higher altitude is that wind can be quite acceptable on the deck but really cook'n higher up. I launched a two stage to 20K' and surface wind was under 10 mph, but I found out later from a pilot the wind was about 50 mph at 3,000 feet. The rocket landed 3 miles away.

I believe the solution is coming down fast and straight, then slowing to landing. Not to say that controlling drogues and maybe the main isn't cool and not worth trying.
 

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This was done about 3 or 4 years ago (for a single main, no drouge). The guy who was developing it invented the same basic system for air drop loads for the military. He was working on it in conjunction w/ a gentleman out in California. Took some tweaking to downscale it. It was a para-foil, GPS steered. It could be set up to "Fly" a predetermined flight path, say around ponds or stands of trees, to a pinpoint landing; Plus could receive real time input/updates in flight to change the flight path if needed for whatever reason. The prototype rocket was flown at MDRA, Higgs Farm; 7.5" airframe on a K as I recall, basic 4FNC. I want to say the altitude was around 4500' (system had a bit of weight but not ridiculous). Wind was quite stiff that day, around 25-30mph. Forward penetration in the wind was quite good, looked to promising and he was looking to downscale it even more, once fully developed. Sadly Don passed away very shortly after that maiden flight. Man was a brilliant engineering and had launched a couple of successful aerospace companies, and more than a couple of hobby rockets. There was talk of his partner out west continuing the project but I haven't heard any more about it. I know there were a couple who expressed concern about the "Guided Return" to a potential target aspect presenting an issue with authorities.
 

Dan Griffing

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I’ve like the way that Dino Chutes X-Form parachutes behave as drogues and haven’t had problems with their four pairs of shrouds — two on each X bar getting tangled.

The spinning of the two halves of the rocket during the drogue part of the descent shouldn’t be a problem. —Disconnect them from the drogue and its steerable controller with a ball bearing swivel and let them spin.

I was thinking about using the MPU-6050 gyroscope/accelerometer chip that JimJarvis50 and his group has used for rocket fin control, along with an ARM Cortex CPU and four small servo control motors to control the four pairs of shrouds.

This overall control package would need to be relatively small compared to the two rocket halves, and would hang directly beneath the 18” or 24” X-chute drogue.

The first control task would be to bring the X-chute‘s rotation under control, and then, as JimJarvis50 et al did with their rocket 4-fin control, use the opposite sides of the X-chute to steer the drogue and rocket in the opposite direction that the wind was taking it.

Would such a thing even make sense? Any ideas or criticism?

Thanks so far to all who have responded.
 

Richard Dierking

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Guided return is no problem if you can do it.
Troy, do you know who Don's associate was? I'm in Southern California and would like to reach out to anyone interested in doing this.

When I did the sonic experiment with a platform descending under parachute, the only way I was able to control spin is by attaching 3 separate parachutes at different points on the capsule. And, the points were close to the circumference. Otherwise the capsule would spin too much for a stable platform.

I would suggest that you spit the rocket into two halves at apogee, airframe and fins with its own parachute for recovery and try and control the direction of descent of the upper part with the nose. I just think this is something you would want to go simple to more complex.

And, a lot depends on what descent rate you decide on.

I think this would be a great project however you wish to pursue.
 

Tech 68

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Any ideas or criticism?
Unfortunately I lack the "skill set" to see something like this through, start-to-finish, but I would like to share an idea...
Similar to the "piston" used for main deploy, use a piston for drogue deploy also. However, instead of being open at one end, seal it up and house the GPS, servos, and electronics inside. Standard apogee deploy would push it out with the drogue attached.
 

Richard Dierking

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Kind of what I did for the sonic experiment. The video follows. The capsule was pushed out of a 4" airframe using a CO2 ejection system. I used 3 parachutes attached at different points because I was interested in stability. However, if you attached 4 shroud lines on one chute (X-type) at different points, I think it would not spin and be controllable. Anyway, skip the part where I'm speaking and go 2 mins 30 seconds into the video to see the deployment. The capsule was this stable all the way to landing.


Richard
 

stantonjtroy

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Guided return is no problem if you can do it.
Troy, do you know who Don's associate was? I'm in Southern California and would like to reach out to anyone interested in doing this.

When I did the sonic experiment with a platform descending under parachute, the only way I was able to control spin is by attaching 3 separate parachutes at different points on the capsule. And, the points were close to the circumference. Otherwise the capsule would spin too much for a stable platform.

I would suggest that you spit the rocket into two halves at apogee, airframe and fins with its own parachute for recovery and try and control the direction of descent of the upper part with the nose. I just think this is something you would want to go simple to more complex.

And, a lot depends on what descent rate you decide on.

I think this would be a great project however you wish to pursue.
I'm sorry I don't but let me see is I can track it down. He had started and sold a couple of businesses and, When I knew him, was retired. Let me see what I can dig up.
 

Handeman

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If you are going to 10K ft and the average wind speed between apogee and a 1K ft main deployment is 25 mph, you need to have a 25mph forward speed on your drogue, or main if you deploy that at apogee, to end up near the launch pad. Add a little more to compensate for the sideways drift of the rocket in the wind as it ascends.

The steerable part is fine, but if you don't have significant forward speed during decent, you are not going to get near the landing site. At our east coast site, 8-12 mph ground winds usually equates to 20 mph @ 3000 ft, 25 mph @ 6000 ft, and +30 mph @ 9000 ft. Some days, add 10 mph to each of those.

The whole purpose of DD is to drop fast out of those high upper level winds. If you are going to open a steerable chute up there, you have to have enough forward speed to counter those wind speeds. If you don't, and have a slower decent rate then a standard drogue, you might end up further away then if you just popped a drogue with DD no matter how well you steer into the wind.
 
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Richard Dierking

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I think it's best to descend quickly over the recovery area to main deployment. But, how quickly is a matter of opinion. And, perhaps with redundancy and history of success. When I use the two small parachutes from side deployment bays my descent from apogee is in the 115 to 125 fps range. At 1100' to 1500' the main (and sometimes the pre-main) deploys and the rocket lands at about 20 fps. Whole fights to 12 K' take less than 3 minutes. I had a flight to 25 K' that took less than 5 minutes. All with no damage.

Also, I found out that if a rocket is coming down "hot" it can wind cock just like on the way up. So, you might think a rocket would travel horizontally with the wind on the way down, but it can actually go farther out into the wind. Again, if you could control a descending rocket to straight down from apogee it would be a great improvement in my opinion.
 

Dan Griffing

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I think it's best to descend quickly over the recovery area to main deployment. But, how quickly is a matter of opinion. And, perhaps with redundancy and history of success. When I use the two small parachutes from side deployment bays my descent from apogee is in the 115 to 125 fps range. At 1100' to 1500' the main (and sometimes the pre-main) deploys and the rocket lands at about 20 fps. Whole fights to 12 K' take less than 3 minutes. I had a flight to 25 K' that took less than 5 minutes. All with no damage.

Also, I found out that if a rocket is coming down "hot" it can wind cock just like on the way up. So, you might think a rocket would travel horizontally with the wind on the way down, but it can actually go farther out into the wind. Again, if you could control a descending rocket to straight down from apogee it would be a great improvement in my opinion.
This summer, a 10k or 20k BSRA launch rocket had a parabolic flight where the horizontal velocity at apogee was well over 200mph. The rocket barely held together at drogue deployment but it opened up a 3/8” SS quick link. I’ve seen the picture of it. Because of gps the rocket was recovered undamaged miles away.

The point is that with a vertically steerable rocket, there would have been no dangerously fast horizontal velocity component at apogee.
 

Richard Dierking

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The point is that with a vertically steerable rocket, there would have been no dangerously fast horizontal velocity component at apogee.
Yes, and also tilt protection for multi-stage rockets.
I wish there was more sharing of information and collaboration to develop improved stabilization and recovery systems. There's not even that much information collected on failures. In fact, for BALLS and XPRS last year, I haven't seen any description and analysis of launch and recovery failures.
If you don't have some type of failure analysis, how can you appreciate the scope of the problem and develop corrective measures?
 

BABAR

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The "main" problem with deploying larger parachutes at higher altitude is that wind can be quite acceptable on the deck but really cook'n higher up. I launched a two stage to 20K' and surface wind was under 10 mph, but I found out later from a pilot the wind was about 50 mph at 3,000 feet. The rocket landed 3 miles away.

I believe the solution is coming down fast and straight, then slowing to landing. Not to say that controlling drogues and maybe the main isn't cool and not worth trying.
Having personal experience coming down under a “steerable” chute during military training, this is right on.

I remember pulling the cord, getting oriented to the nice soft ploughed dirt of the drop zone, steering the chute so I was aimed at it, and whatever my relative forward canopy speed was, it was less than the wind speed and my target site got smaller and smaller even as the spiny yucca bushed aimed at my hiney got bigger and bigger (fortunately I landed BETWEEN bushes, but it wasn’t exactly soft!). Standard military chutes aren’t like the square canopy chutes you see on demo drops done by USAFA’s Wings of Blue where they have good forward speed and stall the canopy for a near zero vertical velocity landing.

Since even High Power Model Rocket Safety Code restricts launching with surface winds over 20 mph


Seems like the winds aloft during the much longer drop from apogee to deployment of main would be a bigger concern for drift compared to drift from a main deploying at much lower altitude.

Interestingly, the rapid fall under drought may be an advantage to a control surface, seems like a faster moving airstream would give your steering device more “bite”, translating into a faster relative forward speed. Obviously you need a target zone well away from spectators, but you could otherwise try to steer the rocket under drogue a bit “upwind” of your desired landing zone.

Of course, this could be a double edged sword. If you lose control, and unfortunately the “forward” direction happens to coincide WITH as opposed to AGAINST the prevailing high altitude winds, or even perpendicular to them, you MAY be worse off than you would be with a standard “dumb” drogue.

My Dad was an Air Force Navigator/Bombardier (he is 95 now.). He worked with some of the early guided bombs, which were controlled by radio frequency communications. Unfortunately, on some of the earlier tests, the communication frequency selected just happened to be that of a local radio station. I don’t know what the exact wattage was, but let’s just say that my Dad’s transmitter was a couple of orders of magnitude LESS powerful than the radio station. They dropped the bomb, and didn’t matter how hard my Dad moved the stick to the right, the bomb went straight left. In any case, the munition impact was well outside the predicted Circular Area Probable.
 

Dan Griffing

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Having personal experience coming down under a “steerable” chute during military training, this is right on.

I remember pulling the cord, getting oriented to the nice soft ploughed dirt of the drop zone, steering the chute so I was aimed at it, and whatever my relative forward canopy speed was, it was less than the wind speed and my target site got smaller and smaller even as the spiny yucca bushed aimed at my hiney got bigger and bigger (fortunately I landed BETWEEN bushes, but it wasn’t exactly soft!). Standard military chutes aren’t like the square canopy chutes you see on demo drops done by USAFA’s Wings of Blue where they have good forward speed and stall the canopy for a near zero vertical velocity landing.

Since even High Power Model Rocket Safety Code restricts launching with surface winds over 20 mph


Seems like the winds aloft during the much longer drop from apogee to deployment of main would be a bigger concern for drift compared to drift from a main deploying at much lower altitude.

Interestingly, the rapid fall under drought may be an advantage to a control surface, seems like a faster moving airstream would give your steering device more “bite”, translating into a faster relative forward speed. Obviously you need a target zone well away from spectators, but you could otherwise try to steer the rocket under drogue a bit “upwind” of your desired landing zone.

Of course, this could be a double edged sword. If you lose control, and unfortunately the “forward” direction happens to coincide WITH as opposed to AGAINST the prevailing high altitude winds, or even perpendicular to them, you MAY be worse off than you would be with a standard “dumb” drogue.

My Dad was an Air Force Navigator/Bombardier (he is 95 now.). He worked with some of the early guided bombs, which were controlled by radio frequency communications. Unfortunately, on some of the earlier tests, the communication frequency selected just happened to be that of a local radio station. I don’t know what the exact wattage was, but let’s just say that my Dad’s transmitter was a couple of orders of magnitude LESS powerful than the radio station. They dropped the bomb, and didn’t matter how hard my Dad moved the stick to the right, the bomb went straight left. In any case, the munition impact was well outside the predicted Circular Area Probable.
The problem isn’t just wind speed. With long burn rocket motors, there’s a larger component of the gravity deceleration vector turning the rocket’s flight to horizontal.

Even without high velocity altitude winds to carry the rocket downrange, a 200mph+ horizontal velocity at apogee with have already carried the rocket quite far by the time the drogue deploys.
 
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