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QuirkyKepler Space module DIY

Posted: Tue Jan 15, 2013 3:52 am
by tmos540
Hi all,
I am both a first time poster, and a Quirky devil's advocate. I recently tried to gain support for a more high-tech version of the Quirky Kepler.
As you can see, I failed. What I was lobbying for was a simple Pi-like command module with a simple if-then computing (If altimeter reads greater than 500 feet, then GPS and wireless is off, if not moving and altimeter less than 500 feet, then super strobe lights and alarm on, etc.) Basic functions for finding and making sure the thing was safe and all. I would have also liked a way to "cut the cord" to the weather balloon so to speak, so the module could drop at a preset altitude. Another one was to keep the parachute from deploying before it was needed, which as it stands, is as soon as the module starts to drop. This would mean less travel to find the module, because the parachute would not have deployed until it was closer to the ground, allowing less drift from wind. I understand that computer-controlling a parachute is probably gonna have more room for error than simply flying it like a flag on the weather balloon tether, but I don't wanna have to cross state lines or anything to get back my module. Anyone thing a Pi would be a good idea for a computing method? How plug-n-play would the altimeter and motors and other sensors be? (I am not anything remotely resembling a electronics engineer, nor a programmer) I have yet to brainstorm good ways of deploying a parachute, but one method I had in mind was to have a simple latch that would be undone by stepper motor, then a shell pops off, revealing a parachute. I would kinda like a way to drop the module if it is stuck in a tree, either via remote, or automated detaching of the parachute once altitude and freefall are detected to be within the allowed parameters.

So, any ideas? I am pretty good with the mechanical and hardware aspects of this sorta thing, but the software would have to be knock-down, drag-out simple (The original Lego Mindstorms programming software was probably the closest/most advanced programming to this sorta thing I have ever done.)
I was going to basically house the computing stuff in something like a Pelican case, watertight, shockproof, preferably canister-like or cylindrical. Maybe a really big Alladin Thermos with shockproof foam bumpers??? And then just attach a GoPro to the exterior. Detaching the weather balloon could be as simple as "@ alt>xfeet, run ycurrent through wire" (thus heating the wire, which would be spliced, or wrapped around the line to the weather balloon, melting or burning it, and detaching the module from the balloon.) I feel like I can think in the mathematical sense, but I may need plenty of pointers on programming language and all.

Cheers, lets see where this goes.
Thomas/tmos540/Snarge/HEY YOU!

Re: QuirkyKepler Space module DIY

Posted: Tue Jan 15, 2013 5:42 am
by aTao
For balloon release I would be looking at a solenoid that retracts a pin. The cord from the balloon would have a loop tied which is hooked on the pin. To be sure that the cord does not slip off too early the pin should poke into a hole.
My first thoughts for parachute deployment are pyrotechnics, they are easy to set off electrically and need not be big enough to cause fire or damage. A small detonator at the bottom of a cylinder holding the 'chute with a membrane over the open end of the tube. Some aluminium foil could offer protection for the 'chute.

For altitude ... price=true looks good. Its an absolute sensor (not differential) with temperature compensation. I would look at hardware (op-amps/comparators) to trigger a single GPIO input for over/under 500 ft, saves a bunch of A->D conversion. And maybe another comparator/ GPIO in for 'chute deployment height if thats not 500 ft.
All very doable, there are threads on this forum regarding GPS interface.

Re: QuirkyKepler Space module DIY

Posted: Tue Jan 15, 2013 6:33 am
by aTao
I just had a thought that with all that processing power up in the air, then there are few reasons why the module isnt fitted with a para-foil type 'chute which can be used to fly the module "home". Then you have even less chasing and finding.

Re: QuirkyKepler Space module DIY

Posted: Tue Jan 15, 2013 9:38 am
by Ravenous
What's the total projected weight? What I mean is, how much can one of these balloons lift to your projected altitude?

There have been a few raspi projects in high altitude ballooning (without the fancy parachute system) posted on the News page as well as the forums, might be worth having a look at these first.

(Fascinating fact: NASA originally proposed either the Gemini or Apollo capsules would come down not on parachutes, but on paraglider type wings which the astronauts would fly onto a landing site. In theory with modern GPS on board, you could have yours steer itself to a predetermined landing site after release.)

Re: QuirkyKepler Space module DIY

Posted: Tue Jan 15, 2013 9:54 pm
by daveake
The Stratosphere has a habit of breaking things that you thought were well designed. Things like stepper motors and solenoids may well freeze up. A Raspberry Pi controller may fail because the SD card comes loose. I would not want to rely on anything not 100% reliable to deploy a parachute, nor would I want to be anywhere near the flight path of such a balloon flight. People use inline pre-deployed parachutes for a very good reason - they're guaranteed to work.

By all means do something 'clever' that's not mission-critical. e.g. a cutdown to separate the flight from the balloon. But the basic flight has to work otherwise you'll be dropping something at speed onto some random location.

Which brings me on to .... if you have little programming and electronics experience, you are frankly going to find it hard going writing a basic tracker. Please do have a go, but my advice is to limit your aims to just that - a reliable tracker that reads the GPS location and transmits it - and not to add any bells or whistles until after you've successfully flown it. Without that basic functionality your flight will most likely not be recovered.