Slightly of topic: ArduPilot for RTL recovery by steerable parachute???

I’m completely new to this and a complete no-know about electronics but I have a few questions not related to a typical UAV.

For reference and typical for 2 stage recovery.

I launch rockets in The Netherlands and as a side project I want the rocket to be recovered by a steerable parachute and returned to a fixed waypoint. Preferable this waypoint would be right next to the launch pad. Basically the return-to-launch (RTL) feature of the ArduPilot.

The rockets are launched twice a year on a military shooting range with restricted airspace and typically achieve heights between 1500 – 2000m. Because of wind, the rockets have either a small parachute for a rapid decent or drift for several km from the launch pad. Ideal situation would be a parachute that could steer / circle the rocket back to the place where it was launched. Two main reasons: 1) safety, 2) higher flights possible with less drift.
RC is not an option because at 1km the rocket under chute is hardly visible.

I have a 3 stage plan of approach:

Stage 1) Proof of principle - by means of building a prototype and launch it from a RC plane. There is an organisation which does just that:

Stage 2) Single stage recovery of a test rocket from an altitude of +/- 1km. All pyro events are triggered by means of a RDAS tiny.

Stage 3) Dual stage recovery from an altitude of 2 km. First a small drogue is released for a rapid but controlled decent to 1km after which the steerable parachute will be deployed and the ArduPilot should take over. Again all pyro events will be triggered by the RDAS.

A few questions arise:

Stage 1-2
1) I think I figured this one out already but is it possible to have an independent direct power supply which does not go through the ESC?
2) Can the unit be switched on/off by means of a physical toggle switch next to the unit and not through and RC receiver?
3) I will not be using IN 1 & 2 on the ArduPilot. Does the unit still function? Basically all I will be using is the rudder servo to control the steering of the chute. The rest is not used.
4) I have the possibility to get a GPS lock when the rocket is at the launch pad and the GPS receiver is out (for reference see photo below. Before launch, I have to put the receiver into the aluminium or carbon fibre rocket. There it will lose GPS lock and only after apogee when the parachute is out the GPS receiver is hanging free again and able to get a lock again. Is this possible? How long would it take for the GPS to get a new lock and does the ArduPilot remember the first GPS lock thus returning to the launch pad (the unit is not switched off)?

Stage 3
5) Experience proves that when the rockets rapidly descents under the drogue chute only it rotate on its longitudinal axis even if swivels are installed in the lines. Is the GPS receiver still able to get a lock when, for example, it rotates at 1Hz on its own axis?

Looking forward to your comments and I thinks this will be quite a fun project.


PS - I’m not trying to make the next DIY cruise missile (there is a distinct difference between a rocket and a missile as my rockets lack guidance).
For more info or my personal site

Views: 2135

Comment by lionel on February 5, 2009 at 11:55am
Hi, why don' t you drop by ESTEC ? there is a section specialising in sounding rockets
Comment by Kyle Sanders on February 5, 2009 at 3:14pm
Wow! that's a much more serious hobby than the Estes rockets of my younger days! I think it would require there to be some sort of measurable direction of travel, perhaps in the form of the rocket being able to "glide" somehow back the the general proximity of home before deploying the parachute. Ofcourse if the 'chute fails to deploy, you've essentially made a GPS guided spike that is homing in on your launch side ... not ideal. Another option would be to use a parasail / foil kite instead of a parachute (like a kiteboarder), then you would be able to have "forward" movement. You could change direction like a kiteboarder would, shortening the amount of line out on each side with say a winch servo (sailboats) but that would require some pretty trick coding! If the GPS only refreshes once per second or so, and a 1meter parasail / foil kite might do a 360 degree twist in much less time - could be worth a try tho. Atleast that way you still have a parachute-like flapping wad of cloth in case of a total system failure!

3D Robotics
Comment by Julian on February 5, 2009 at 3:55pm
The problem would be that the parachuting rocket would have no means of propulsion so you might be able to steer it into the wind to get it back to the launch site, but the wind would still take it in its direction regardless.
Comment by Kyle Sanders on February 5, 2009 at 4:00pm
You would trade some of your drag the parachute provides to spill out one side to give it thrust ... of sorts. Rather... it would be like falling slightly down-hill, gravity pulls you down and in the opposite direction of the spill in a steerable 'chute. It then becomes a very inefficient "glider."

Comment by Brian on February 5, 2009 at 6:18pm
Expanding on the kite concept:

Picture the rocket as one of Batman's cool gadgets. His would have wings (yes, Bat wings) that pop out of the side instead of a parachute. They could be spring-loaded carbon framework and ripstop nylon. One wing could have a subtle weight on it which would cause a gentle circle pattern glide to earth. An autopilot could be used in lieu of the weighted wing and have a servo control a left and right side flap (like a two channel v-tail glider) and have a little control during it's decent...
Comment by Kyle Sanders on February 5, 2009 at 10:54pm
Yeah, the MOAB has a pretty slick "grid wing" system. If you want something completely internal to your rocket payload / recovery system section, maybe there's something to be said for a Rogallo wing? Stick a motor on it and it would really remind me of those "powered parachute" class ultralight / microlight aircraft!
Comment by j on February 6, 2009 at 6:56am
I've prototyped something similar to this. Quick tips (sorry don't have much time right now):
* the worries you mention are no problem
* your biggest worry is the oscillation of the payload causing instability. As the payload oscillates, it changes the shape of the parafoil, and may pull the brake lines (used to steer). Solving this will likely take a lot of testing. The problem is mainly after deployment, if you make it through the first few seconds you should be fine.
* I used a kite that people use for kite boarding (but the dry variety, not the kind for the ocean). It worked well. Making your own is just adding more chance of things going wrong. The kits come in many sizes from 1m2 and up.
* I'm not familiar with ardupilot (other than hearing of it before), but the controls problem is different than a plane.
Comment by Kyle Sanders on February 6, 2009 at 8:50am
I know in kiteboarding you use 30 meter lines... the longer lines help smooth out some of those problems. Maybe with say ... 10 meter lines you would reduce some of the oscillation problems, as a shift of half a meter on the end of a 10 meter line is a much less drastic change!
Comment by Jim on February 6, 2009 at 10:35am
I'm attempting the same thing but for high-altitude balloon payload recovery rather than rockets. I'm also planning on using a large single line delta kite as my test platform to drop the payload from rather than an R/C plane. Right now i'm working on some of the servo and radio software using processing and the arduino. Arduipilot will be a natural progression for me when i go autonomous. i'm trying to document my progress over at I'm looking forward to seeing your progress!
Comment by JvdB on February 6, 2009 at 10:48am
I will use a ramp air parachute or parafoil. The idea of a kite crossed my mind and it will be a fast and cheap solution during prototyping.

Maybe one of you guys can explain to me why a parafoil is that much different to control than a RC plane with a rudder only autopilot? The parachute will have forward motion (not as fast as a RC plane but that is good with the 1Hz GPS refresh rate. It will only loose altitude but that is the whole idea and I do not want to maintain altitude as with and RC plane. I only want to use left and right motion which a rudder only autopilot just does on a RC plane.

Jim - your goal is the same as mine, looking forward sharing info together


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