Arduino Controlled Parachute Release

[grant gibson]

Hello all,

I have been involved with amateur rocketry for around 17 years and am also part of a makers hackspace group in Derby. We have recently moved to the digital communications museum in Derby and one of our first projects is looking likely to be a HAB. I am an engineer and have vast experience in laser cutting/3d printing owning 2 3D printers and have started dabbling a bit with arduino but I'm keen to gauge some opinions and also whether this has been done before on an idea I want to instil from the rocketry world.

The way I see the current HAB launching and recovery process is very much dependent on environmental factors. In rocketry when you launch to anything beyond around 5000ft it is advisable to have something called dual deployment whereby a small drogue is released at apogee followed by a larger chute at a lower designated altitude. My thoughts for the HAB project were to use an arduino to sample the air and provide the ability to deploy a chute at a much lower altitude than leaving it to the wind. My idea from apogee is to have a cluster of streamers and allow the payload to effectively free fall down to 10k ft where a small drogue is deployed and then the main chute deployed at 2000ft

Has anyone done this already? Does anyone know of an altimeter circuit that exists for such a setup?

Also if anyone wants to get involved with Derby makers they are more than welcome to we would always welcome new members

Regards

Grant Gibson

[Ed Moore]

Hi Grant,

It has been done before but it's not had widespread use. Partly it's a requirement of the Exemption order (the thing that you get when you apply for a NOTAM) that the system descend under parachute anyway (not a huge deal if you have a small drogue chute, but would preclude a free-fall), and partly it's just that it's a bit of a higher safety risk to have something fall at high velocity and require software to work correctly in order to land at a safe (we generally say <5m/s) velocity. With a pre-deployed parachute you can have a total avionics failure and still come down at a safe velocity.

You would also have to run several flight simulations for your various cases - one for a nominal chute sequence, one for a failure to deploy the main, to make sure both of them are not landing near motorways/towns/airports/whatever.

But if you can ensure the system works to your satisfaction, and satisfy the requirements of the exemption, then you can probably go for it.

As for an altimeter-circuit, well if you're playing with arduinos anyway then just DIY it. Not too complicated. An off-the-shelf HPR parachute deployment system might Just Work (tm) too, provided it doesn't get too confused by the very low pressures it'll likely see.

Keep us posted,

Ed

Grant Gibson

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[Steve Aerospace]

Hi Grant,     I came to HAB via Amateur Rocketry some 10+ years ago - you might remember me from the EARS committee. The main difference between Amateur rocketry and HAB - is that with rocketry you are flying a rocket above a launch site that is private land with the owners permission and few people in it - if the chutes fail your rocket should land within the launch site. With HAB you are potentially landing the payload anywhere - it's essential that the cute deploys - so the in line pre-deployed chutes are preferred.

As Ed says the main thing against streamers/free fall is the wording of the permit which says: "equipment to descend by parachute".  The implication is the entire descent is under a chute.

I used a dual deployment system for the HAB part of James May's Toy Stories - Action Man at the speed of sound - pulling out a small drogue at release and a main cute after a minute of "freefall".   That required considerable testing and a separate "dropping of articles" permit from the CAA (I think its called an aerial application certificate).

    Steve

Steve Randall
Random Engineering Ltd
st...@randomaerospace.com
+44 7802 242135

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[Phil Cox]

Hi All,

I was interested to read that others had considered a packed main canopy for a HAB flight. I’m due to launch my first HAB on Saturday (4/8/18) with a conventional in-line parachute but, having been a skydiver, I’m really interested in designing a drogue-deployed main canopy.

My plan was to have a very small, in-line parachute that will inflate after the balloon bursts to give a stable but fast fall, when a given set of conditions are reached the drogue will be released much in the same way a tandem master initiates deployment at pull time.

The drogue bridle will be attached to the HAB via a cut-away system (exactly like a skydiver uses to disconnect a malfunctioned main canopy), a small linear servo will withdraw a strimmer cable from the cut-away loop at pull time. The drogue bridle is attached to the apex of the main canopy which is withdrawn from a deployment bag, a good way to control the rigging lines and avoid tangles.

The real challenge is building redundancy into the system to account for all scenarios that would prevent the servo withdrawing the cable. To set the conditions for this, I’m using altitude and temperature (increasing…i.e. descending), I could (and probably should) build in an accelerometer as another way to detect freefall.

Could all be a pipe dream but it will be fun having a go. Would be interested in people’s thoughts.

Best wishes

Phil

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[Ian Leitch]

Hello,

Could it be that a suitably sized drogue would apply a sufficiency of drag to withdraw the main chute once the atmosphere thickened sufficiently. The problem would be in calibration consistency, but might offer a very simple approach, the main chute being a 'suitable' friction fit in the tube.

A worthy subject to discuss over beers at Conference . . .
Regards,
Ian_