Idea for guided descent

HunterWhyte

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Hi everyone, I've built a few model rockets from kits but by no means do I know what I'm talking about. The truth is I am more into RC stuff than rockets and I recently had an idea for a guided recovery system and wanted to know what some of you guys thought.

The basic idea is to use brushed dc motors and propellers attached to a nose cone to control where the rocket lands. The nose cone itself would have a separate parachute from the body of the rocket with both of them packed into the body to start. Then the nose cone separates from the body and glides down directly attached its oversized parachute to safety without having to worry about drift since it is able to be controlled by the four brushed motors attached perpendicular to the nose cone while the body quickly descends on a smaller chute or streamer. Here's a picture to better describe what I am talking about https://gyazo.com/88f7192b2e636c993965b2259eb123e8.

I have made a small scale proof of concept with just a physical switch controlling the motors and the idea seems to work good if anyone wants to see the video. Does anyone have thoughts on this concept? I'm currently hung up by trying to figure out the most stable parachute and where to get it. I'm also unsure about a good speed of descent and by extension the size of the parachute if anyone has ideas about that either. Anyways, doubts? concerns? dream crushing realities?

Thanks in advance!

- Hunter
 

djs

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I'm a little confused by this- if the nose cone is separated, then you have two pieces to find, right? Also, bringing the body down with a small chute or streamer may not be all that safe.


FYI- the guy you want to talk to on here is the user Ravenex- he has a rocket where he has a steerable parachute to bring it back to him by guiding it via RC.
 

Scott_650

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Other than the increased drag from the props and the added weight from the motors/batteries/servos looks like an interesting idea. Not sure if there’s any practical reason to do this but what the heck - we do this for fun so why not?! I’d probably go ahead and add a keychain camera while you’re at it, the video of the descent phase would be fascinating.

As for the separate recovery of the body tube how about attaching a leader - maybe a steel fishing leader? - from the tip of the nose cone to the shock cord. With the props sticking out the side there is a chance it’ll tangle but if it works everything comes down under R/C control. And it’s not like drag is a big concern - you have propellers sticking out of your rocket anyway!

You will need a fairly substantial rocket motor to lift this contraption high enough to make it worth the effort - probably should use a 29mm Aerotech single use motor - at least. Econojet motors, I think, can be shipped ground with no hazmat fee if that’s a concern. Good luck and post an update if you try it.
 

rcktnut

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dsj beat me to it, and is right on the 2 parts to find. Unless you have a lawn dart the nose cone is about the only thing that survives intact with a rapid descent. Why let the most vulnerable parts- body tube /fins descend fast and have the nose cone under an oversized chute and try to steer it back? Stability could be an issue also with props hanging out of the nose cone.
 

HunterWhyte

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I'm a little confused by this- if the nose cone is separated, then you have two pieces to find, right? Also, bringing the body down with a small chute or streamer may not be all that safe.

FYI- the guy you want to talk to on here is the user Ravenex- he has a rocket where he has a steerable parachute to bring it back to him by guiding it via RC.

Thanks for the reply. Yep sorry I think I've confused a lot of people in this thread! My idea wasn't that the body is disposable and comes plummeting down to earth I sort of meant that the parachute for the body would be reasonable or I guess standard for it's size while the parachute for the nose cone would be over sized relative to it's mass ( my current plan has it under 75 grams). And the hopefully if the RC control works you would only have 1 piece to find :wink:.

I've looked at Ravenex's steerable parachute it's such a cool project! (and way more practical than my idea)


Not sure if there’s any practical reason to do this but what the heck - we do this for fun so why not?! I’d probably go ahead and add a keychain camera while you’re at it, the video of the descent phase would be fascinating.

Exactly what I was thinking! I would definitely include a camera if I ever give this thing a go.


As for the separate recovery of the body tube how about attaching a leader - maybe a steel fishing leader? - from the tip of the nose cone to the shock cord. With the props sticking out the side there is a chance it’ll tangle but if it works everything comes down under R/C control. And it’s not like drag is a big concern - you have propellers sticking out of your rocket anyway!

dsj beat me to it, and is right on the 2 parts to find. Unless you have a lawn dart the nose cone is about the only thing that survives intact with a rapid descent. Why let the most vulnerable parts- body tube /fins descend fast and have the nose cone under an oversized chute and try to steer it back? Stability could be an issue also with props hanging out of the nose cone.

The idea of having the rocket body come down on a separate parachute is based entirely on my doubts about the thrust that these little brushed DC motors can output. I'm worried that controlling the body tube's descent with this method would require too large of motors and propellers to make it move enough to be practical while I know that just the nose cone could definitely be controlled by this method. My though process was also that in my case all the expensive stuff (flight computer, radio control, batteries etc) would have to live in the nose cone so I thought I would be saving the more valuable part. It would definitely be ideal to be able to control them both under one parachute but I am just concerned that I would not be able to get very much control over the rocket's descent but who knows! I guess I should do some testing to see if I can move the body along with it.

As for the concerns about stability I really am a beginner with all so I don't have much of an idea on how much they would affect stability. Maybe there is some clever way to get around the propellers being exposed before the stages separate.

You will need a fairly substantial rocket motor to lift this contraption high enough to make it worth the effort - probably should use a 29mm Aerotech single use motor - at least. Econojet motors, I think, can be shipped ground with no hazmat fee if that’s a concern. Good luck and post an update if you try it.

I'm not sure if this changes the motor you would suggest but sorry I think I've been really vague on the scale of this thing! With the way I have it set up right now I can fit the flight controller, RC tx and batteries all inside a diameter of 42mm and the brushed motors themselves are 7 or 8mm in diameter and 16 - 20mm in length with 30 - 50mm diameter props. So far the AUW of this stuff is around 75 grams just in case anyone was curious.

Thanks for all the help and suggestions guys I really appreciate it! I'll definitely post updates if I decide to carry through with this.
 

Steve Shannon

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Thanks for the reply. Yep sorry I think I've confused a lot of people in this thread! My idea wasn't that the body is disposable and comes plummeting down to earth I sort of meant that the parachute for the body would be reasonable or I guess standard for it's size while the parachute for the nose cone would be over sized relative to it's mass ( my current plan has it under 75 grams). And the hopefully if the RC control works you would only have 1 piece to find :wink:.

I've looked at Ravenex's steerable parachute it's such a cool project! (and way more practical than my idea)




Exactly what I was thinking! I would definitely include a camera if I ever give this thing a go.






The idea of having the rocket body come down on a separate parachute is based entirely on my doubts about the thrust that these little brushed DC motors can output. I'm worried that controlling the body tube's descent with this method would require too large of motors and propellers to make it move enough to be practical while I know that just the nose cone could definitely be controlled by this method. My though process was also that in my case all the expensive stuff (flight computer, radio control, batteries etc) would have to live in the nose cone so I thought I would be saving the more valuable part. It would definitely be ideal to be able to control them both under one parachute but I am just concerned that I would not be able to get very much control over the rocket's descent but who knows! I guess I should do some testing to see if I can move the body along with it.

As for the concerns about stability I really am a beginner with all so I don't have much of an idea on how much they would affect stability. Maybe there is some clever way to get around the propellers being exposed before the stages separate.



I'm not sure if this changes the motor you would suggest but sorry I think I've been really vague on the scale of this thing! With the way I have it set up right now I can fit the flight controller, RC tx and batteries all inside a diameter of 42mm and the brushed motors themselves are 7 or 8mm in diameter and 16 - 20mm in length with 30 - 50mm diameter props. So far the AUW of this stuff is around 75 grams just in case anyone was curious.

Thanks for all the help and suggestions guys I really appreciate it! I'll definitely post updates if I decide to carry through with this.

One thing that you may want to look into is whether the rules for drones become effective with guided or radio controlled descent.
 

HunterWhyte

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That's a great point I hadn't considered! Here in Canada I believe the weight restriction is 250 grams before it starts getting more restricted so I suppose that could be another reason why I might have to make just the nose cone controlled and not the entire rocket. Thanks for mentioning that, from what I've read as long as I stay beneath 250 grams I should be allowed to operate it at a high enough altitude.
 

Andrew_ASC

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Hey bud. I think you are real inventive. I like your guided recovery idea. I think you have made a system too hard to implement and far too expensive or heavy. Have you seen those sport rectangle parachutes that are agile? You could have one servo pull the entire harness to left or right and steer the chute on landing rather than try to launch s rocket with four props/motors/power supply etc. It would be guided glide recovery instead of powered recovery. Unless your like really into drones I think you have made it too hard to do. I don't think you'd meet that weight restriction. By using a base jumper style chute on a model rocket it still qualifies as parachute recovery. The only thing you are doing is allowing the user to control the descent pattern direction by r/c.
 

Andrew_ASC

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I don't know how practical it would be to miniaturize a parafoil type chute. I don't know much outside of traditional chute design and those chutes are rather complicated. Somehow I think something pack able and motor eject deployable is better then creating a bunch of unwanted drag on a rocket. And I don't know how a Parafoil chute would do if it deployed at zero forward velocity because those are glide chutes.
 

HunterWhyte

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Hey bud. I think you are real inventive. I like your guided recovery idea. I think you have made a system too hard to implement and far too expensive or heavy. Have you seen those sport rectangle parachutes that are agile? You could have one servo pull the entire harness to left or right and steer the chute on landing rather than try to launch s rocket with four props/motors/power supply etc. It would be guided glide recovery instead of powered recovery. Unless your like really into drones I think you have made it too hard to do. I don't think you'd meet that weight restriction. By using a base jumper style chute on a model rocket it still qualifies as parachute recovery. The only thing you are doing is allowing the user to control the descent pattern direction by r/c.

Thanks for trying to let me down gently and not outright crush my dreams! The one thing I am somewhat confident in is with the weight and cost. I'll send in a design and some pictures of a put together prototype as soon as the rest of my parts come in. I've actually managed to put it together with some pretty inexpensive stuff (who knows if it will work though). If I just control the descent of the nose cone I am pretty confident that I would meet the weight requirement but I definitely understand your doubts about that!

As for the glide recovery idea I really would like to try a project like that! But as far as I can tell the hardware for that ends up being not that much simpler than what I've come up with as well as the extra issues of parachute deployment and everything which I am a lot less knowledgeable about than this RC quadcopter stuff. Also I am not sure if that then classifies as a UAV as well or if I'd have a weight restriction on that. Maybe I'm just stubborn but I've yet to run into an issue quite big enough to have me give up on this idea quite yet. I will definitely try a project like that if I hit a big enough problem with this one though.

I really don't mean for this thread to turn into me defending my idea against everyone's reasonable doubt and advice. I'm just trying to explain my idea better is all. Thanks for your advice I really appreciate it!
 

Andrew_ASC

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I am concerned of the windmilling propellers if exposed in flight. If you find a mechanism to spring unfold it when cone pops off so it's stored into a tube you can avoid a lot of rocket aero headaches. If the motors and propellers are near nosecone you will have a forward CG rocket that may be over stable.

I am not familiar with the saucer style rockets. Maybe it's easier to put a rocket motor on the quad copter you build as a prototype just to proof of concept this.
 

HunterWhyte

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I don't know how practical it would be to miniaturize a parafoil type chute. I don't know much outside of traditional chute design and those chutes are rather complicated. Somehow I think something pack able and motor eject deployable is better then creating a bunch of unwanted drag on a rocket. And I don't know how a Parafoil chute would do if it deployed at zero forward velocity because those are glide chutes.

That's another thing. I really don't know much about parachutes and I don't know how easy it would be to find a suitable miniature parafoil. As for drage I think that there would be a way to have the motors hidden until the two stages separate but I don't know if it would work https://gyazo.com/816efbf8ae880123375f033492cea700 heres a link to a diagram if that helps, I'll try to explain the best that I can. The motors would be mounted to a tube attached to the shoulder of the nose cone inside of a larger tube that couples the two stages together. When the stages separate and the nose cone gets blown off the motors are then out in the open air. Hopefully that makes sense. The motors aren't in a quadcopter configuration at all really not sure if that picture demonstrates that but the motors are perpendicular to the body of the rocket so the propellers would be parallel I guess you would say and would pull the rocket beneath the parachute so I suppose it's a form of gliding descent. Sorry I've had problems explaining this to people in person so I can imagine it must be pretty bad over the internet!
 

Andrew_ASC

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Much better. I hope you plan to add realistic masses. I see your CP is infront of CG which is not stable rocket. You may want some counter weight or maybe this is still just prelim anyways have nice evening.
 

HunterWhyte

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Yep I just whipped that up to show the general idea of the inset tubes kind of thing not a real design. You too, thanks for the help.
Here is a crude test of a really basic proof of concept prototype I did. if you look closely there is a propeller and motor being powered by a small 1s battery pushing the parachute in a certain direction https://drive.google.com/file/d/1P5b2EeUlWDgMcQb3hAvHlWd_R6ckmiw-/view?usp=sharing sorry for the lack of editing, I drop it at around 38 seconds into the video. Maybe that will help show what I am trying to do.​


 

HunterWhyte

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Does anyone have any tips about the type and size of parachute I should be looking for. I think for my project it would be better if the parachute was as stable as possible so I've been looking at ringslot or ringsail parachutes but I don't think anyone sells them in this smaller size. As for size, I've done some descent velocity calculations and I think that I'll need a parachute around 75cm or 30 inches in diameter using this formula

S= ( 2 x g x m ) / (p x C x V2 )
where S is the area of the parachute. g is acceleration. m is the mass in grams. p is density of air. C is the coefficient of drag, estimated at 0.8. V is the descent velocity in m/sec.

My rough idea for a good descent velocity is around 2 meters/second but I may be underestimating how slow that is. Anyways if anyone has any tips or ideas about this and how stable of a parachute I'd need I'd love to hear them, thanks
 

cerving

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Maybe you can have four passive helicopter blades pop out with the nose cone, and control the angle of the blades with servos to guide it.... just a thought.
 

HunterWhyte

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Maybe you can have four passive helicopter blades pop out with the nose cone, and control the angle of the blades with servos to guide it.... just a thought.
that is a really interesting idea. Sort of like control fins kind of thing? I'll definitely have to try that out
 

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A few years ago at MDRA, we got to watch a flight, and more importantly the landing, of a rocket with a completely automated recovery control system. It used a combination of GPS and servos attached to a parafoil to self-steer to a spot on the ground close to the pad. Pretty amazing. Unfortunately, just prior to the launch, the gentleman who designed it died, and this launch was done in memoriam. I truly don't know what happened to the idea or the implementation after that.

I would have to think that someone out there with a good knowledge of this kind of engineering would be able to duplicate this effort. There would be cost up front, but I'd surely buy one. Landing near the pad every single time no matter how high you go? Priceless.
 

rcktnut

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I see projects like this more of something to fool around with, rather than practical, and nothing wrong with that. It doesn't take much wind working on a chute to over power the methods trying to work against it. I guess with no wind at all they would work out better, but then don't have to worry about the rocket drifting too far in the first place. A few years back at the Rockets for Schools event here some students had ducted fans in the payload section to try to steer the whole rocket back. They did not launch it at the event, but they told us the trial launches they did with it were not that great. They believed it helped somewhat but again, the wind prevailed.
 

HunterWhyte

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I can agree with that, it's definitely just a fun little project. It probably would barely work in the wind but still something to try
 
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