sheesh! use clockwork
Why not just calculate how long it ought to take the balloon to ascend to release altitude, and have some clockwork cut the string?
Well, it's all go here at the PARIS programme headquarters, and we've spent the last 24 hours pondering the sticky issue of how to release Vulture 1 from the weather balloon which will carry it aloft in summer 2010. Our PARIS Vulture 1 logo More on that in a bit, but first thanks very much to all of you who chipped in with …
Do you have a ban on electronics in the *balloon*? The syringe method seems a good backup approach, but it's going to be tricky to calibrate - you're looking at around 10mb at that altitude, so you'd need a long thin tube to be able to place the plunger, and also need to be pretty sure that the piston is both easy enough to drive and sealed well enough to avoid leakage on the way up.
There are dozens (well, some) of pressure sensors available which will give an accurate reading at that level - something like the Intersema 5534 works down to 10mb and may be suitable - I have designs and code for an AVR chip altimeter which could be adapted.
Alternatively, since that unit requires a microprocessor to talk to it, Motorola do some sensors in the right range; they'd just need an op-amp to trigger the release.
Just a thought...
(hey, I don't get to do the technical logo often, right?)
Haven't really been following so if this has been said before, everyone please berate me.
You mention some kind of syringe-based mechanism. How about this: attach the plane to the plunger of a 100ml syringe and attach the barrel to the ballon. Suck 1ml air into the syring on the ground (at 100kPa). At 100,000ft (about 1kPa according to http://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html), the plunger will fall out.
I like the idea of a pressure release using a collapsing tube but I think the calibration might be a bit tricky. There are lots of variables and testing is desctructive. Syringe plunger looks more promising.
Other than pressure both temperature and radiation will change with altitude. I don't think radiation is a goer but could temperature be used with a version of a bi-metal strip. Would have the advantage that it could be tested in a fridge and be easy to calibrate for ambient conditions.
Just some thoughts to add to the mix. People Who Know Better may well shoot me down in flames. But if any project deserves the benefit of Blue Sky Thinking I guess it is this one.
"what's the best electronics package to make this thing work."
PIC get's my vote (www.microchip.com). They come in a huge range of models depending on the processing power required, number of I/O pins and on-board perhiperals (including timers, A/D convertors, communications trancievers, hardware interrupts, etc). There's plenty of pre-assembeled break-out boards available so there's no need to do too much soldoring either...
From your earlier article:
> Our tentative plan is to construct three aircraft: Low altitude prototype for initial testing; fully-equipped medium altitude example for systems-test release from aircraft; and the final operational model.
See the Air Navigation Order 2005, section 66 (2). http://www.opsi.gov.uk/si/si2005/20051970.htm#66
But you might be able to get a permit - my instructor got a permit to drop me out of an aeroplane.
internet connectivity and tunes while its on the way down. Strap a smartphone to it :) And for comnparison, drop an unprotected Iphone....
My LG U820 dies a similar way, I have a video somewhere of it leaving the barrel of a large cannon, punching the cloudline, then the phone hitting the ground.
Sure someone there can donate a phone.
"Bear in mind we're talking about an aircraft here, so it has to be a light as possible and stowable in the fuselage. If the weight starts to rise, then the wingspan starts to increase, and before you know it we've become Lockheed Martin." .... Ouch, those Direct hits hurt, Lester, but they do like them ... :-) Virtually IntelAIgent Vultures to Strip the MetaDataBase Carcass of ITs Pwnd Carrion, Compromised Failed Systems with Infinitely Odd PornographICQ Drivers, thus for ITs Sinful Viceless Drive to Engage and Harness.
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How about making one to start with? a couple of vacuum cleaners, a pressure gauge and a pressure cooker (?) should do the trick for the small scale stuff.
For larger scale testing a real one would have to do I guess, but if there is a spare gas container anywhere you could try using that???
Only a thought.
Another thought on a chase-plane would be the SR.177 (http://en.wikipedia.org/wiki/Saunders-Roe_SR.177) or 187.
But then that was cancelled as well...
Get a piece of concrete pipe big enough for your needs, put a thick ( > 30mm) metacrilate circle on both ends, one end attached with some flexible cement (poliuretane may be a good choice, the other end justa a rubber ring.
On the fixed plate, insert a fitting, and ask your local air conditioning guy to lend the vacuum pump to evacuate the air.
Envelope the concrete with plastic film to seal it.
When ready to go, insert model into chamber, engage the pump, hold the rubber ring end until pressure starts to drop and observe the effects from a safe distance.
If the chamber can be smaller, a bottle with a big mouth may be easier.
You can also evacuate air with pirotechnically assisted methods, bur are trickier.
And for the electronics, i reaffirm myself that a HTC Dream / Hero is the way to go, beacuse it has it all included and tested, so you ONLY need to write the software (he he he).
How about using a (suitably scaled down) set of these?
Just put the weight of the plane on the end of one, put it in your chamber and fine tune the vacuum level you would need between them to get separation?
David63's comment about temperature prompts me to note that it would probably be a good idea to wrap the camera (not the lens, obviously) in a thermally protective jacket. The temperature gets pretty frosty at interesting altitudes, and it wouldn't be much fun if the most interesting photos were missing because the camera or its battery had packed up.
On a structural note, papier maché presumably counts as paper and can make surprisingly strong, lightweight structures.
And another vote for PICs, but remember that if there's soldering involved get a home constructor to do it, as we (sorry, they) are still allowed to use *proper* solder with lead in it rather than that dodgy lead-free stuff. (I'm assuming we want it to work reliably :)
Avoid the hassle of making the electronics and enjoy ready made software platform you can customise, all the hardware you need can can be got here for $350 + cost of radio modem:
Just add styrofoam plane, pressure sensor for release control and a time lapse camera and your done, it should even glide back to the launch site if setup right.
Signed up specifically to vote against pics-- done way too much development with them in the past. Their performance is worthless, their compilers are frequently buggy, and the errata lists are enormous. You'd be much better served by an ARM or Atmel AVR (both supported by GCC so you won't need to shell out extra for a compiler). Though I'm a worthless Yank, I'd plump for some sort of ARM, this being a British space effort.
Depending upon budget and resources, you'll also need to make a decision on surface mount vs. DIP (DIP is bigger, heavier, but easy for hobbyists and prototyping). There used to be a "tiny arm" DIP with a surface mount ARM and supporting hardware in a 40 pin package which was quite nice, and I also seem to remember liking the AT-mega 70 series (interrupts available on every pin).
You'll need to browse a lot of spec sheets also to find a part that can tolerate extreme cold-- you may have some success looking for military spec parts. Spraying the whole assembly in insulating foam to hold in the heat might help too.
Your local secondary school should have a perfectly adequate vacuum pump, and the chamber would only need to be big enough for the release mechanism (and possibly the rest of the payload), not the whole model. I'm sure a school physics lab supplier could sort it out.*
* Always assuming that kids these days are actually allowed to actual experiments - I wouldn't be surprised if some H&S twat has banned them from chucking lumps of sodium into water troughs etc. Killjoys.
Has anyone discussed the aerodynamic problems yet? It'll be tricky to design something that can 'fly' in any meaningful sense at both 100,000ft and 0ft - the air is just too thin at that altitude. I suspect that the plane will drop like a stone and reach quite a high speed, before needing to decelerate and transition to a more normal flight mode.
I don't know enough to suggest a solution but I suspect it won't be easy......
Here's my $0.02 on barometric release mechanisms. Keep it simple, and think about the COLD. I was about to suggest an electronic solution based on a chip pressure sensor (the electronics weigh little if you use tiny surface-mount chips and avoid heavy packaging for the circuitry), but batteries tend to freeze at -40 C. Still, it may be more workable than a mechanical system. You may need to use heaters (probably left behind on the balloon at release) to keep the electronics functional.
For a mechanical release system, consider the flat, disk-shaped bellows used in an aneroid barometer (but filled with air so it expands at altitude to trip a release lever); simple, can be calibrated to operate at the right pressure/temperature, should be very reliable.
Speaking of very cold temperatures, that's going to be THE major issue at altitude; making the systems (primarily the batteries) function at those cold temps. By the way, the cold will raise hob with most mechanical release mechanisms like the syringe-plunger actuator.
Hypobaric testing is of minor importance compared to low-temperature testing that mimics the temperature profile of the intended ascent.
Here's another thought on electronics, light weight, and thermal issues: Sandwich the electronics between flat sheets of thin foam plastic that form the fuselage/wings; you can get flat batteries that can be insulated this way, too. For structural strength, you cannot go wrong with a strip of carbon-fiber tape as a wing spar. This is frequently used for RC model sailplanes; glue the tape to the top and bottom of a floppy foam wing, it becomes MUCH stiffer.
Another thought on weight: If using off-the-shelf electronics, strip off all the plastic cases from everything to pare down the weight.
Y'all really should look at some of the high altitude ballooning groups on this (left) side of the pond. There are quite a few groups in the US which launch high altitude balloons with payloads consisting of amateur radio equipment to down-link the data in real time. As for cut-down mechanisms, be aware that the flight is not a smooth event. Once the balloon hits the jet stream, the ride can be exceedingly violent (300+ mile per hour winds!). Thus, the suspension and cut-down mechanism need to be able to handle such roughness.
As for running a string around the balloon, you really don't want to do that. Latex is exceedingly delicate, and any friction against it can easily poke a hole in it. The best case result is that you have a premature burst, with the payload floating down from a few thousand feet. The worst case result is that you make a pinhole in the balloon, which allows a bit of the lifting gas to escape, producing a "floater" which can float for days (Couple this with 300 mile per hour ground velocities due to the jet stream, and it becomes highly unlikely you'll ever see your payload again!).
Here's one of the groups where some of the amateur balloonists hang out:
Oh, by the way, one of the guys has constructed his own hypobaric chamber, complete with low temperature conditioning, and ultraviolet light exposure.
And El Reg in general...
I seem to recall on Blue Peter or something many years ago seeing them make 'helicopters', whereby you take a strip of paper and tear it lengthways then fold the two halves out into 'blades'. When you realease it from a height it spins like a sycamore seed.
If you were to produce a similar albeit more advanced/sturdy version with your electronics at the bottom it would have the advantage of being able to freefall at high altitudes where the atmosphere is thin, then when it gets into denser air you wouldn't have to worry about changing from freefall to flight mode - the drag of the blades should keep it the right way up and it'd start spinning and slowing itself down (or at least reaching some maximum velocity).
If you were feeling particularly clever, you could make the blades adjustable so you could used the accumulated rotational energy to actually slow the descent and even hover.
I think I see a problem with your "string around the balloon" possibility.
The payload has to be light enough that the weight won't cause enough friction to hold the pin locked between the downward force of the payload attachment and the upward force of the balloon attachment.
Note here that I'm assuming something like this:
0 0 0 --------- Release Pin
...Now, you may have another suspension system planned that doesn't pull down on the pin at the same time that it's ALSO lifting up on it but I can't see it at first glance.
Further, given the above friction-lock problem, it seems to me that the total weight of payload and balloon attachment has to be enough that the horizontal force of the tightening string doesn't just pull the whole thing to the side until the combined horizontal and vertical forces on the two strings (hanging and pin-puller) are equal, leaving the payload hanging from a V-shaped cradle. And, since you presumably don't want the plane itself to be that heavy, then you might need to think about a way of making sure that the brick hanging from the bottom of your balloon ALSO lands at non-destructive velocities if the balloon bursts.
Just a couple of thoughts that occurred...
Another vote for a PIC based microprocessor approach here, there are quite a few different projects offered online you can base a design on, (such as http://www.gedanken.demon.co.uk/gps-sd-logger, built myself a nifty little cycle computer based on this), which are incredibly small and light and offer the opportunity to continuously log the flight to a SD card.
Also a PIC would allow a number of different 'height measurement' & 'release mechanisms' to be incorporated simply (GPS & pressure sensor for measurement, smart wire or micromotor for release).
And as Nebulo suggests, get a hobbyist to solder it all together so they can use 'proper' solder!!
(And if you want to load up a frikin' laser beam I can recommend a certain TAT market...)
If you are going for a record flight of a paper plane it might be worth checking with the Guinness people what evidence would be needed. The electronics package would need to provide this. It might also be worth checking their definition of a paper plane.
Would it be possible to get the Ubuntu bloke to just chuck it out the door when he next goes to the space station?
Why not an airplane shaped zeppelin with a pressure vent that releases one way as the external pressure goes down in relation to the internal pressure.
The balloon/plane goes up and reaches a balance between the lift of the gas/weight of the plane and the pressure difference releasing gas.
Once the vent reaches a balance the vent no longer releases gas and the plane/balloon (now heavier than the air) glides back down.... eventually.
You can carry more weight this way, (a signal?) and reuse the device later. (when you find it)
/Do not use Hydrogen....
Used them all over the place myself- just remember to code it in Assembler. You lose the compilation problems and solve the speed issues someone above mentioned. You'll only need a pretty simple program, so the extra irritating bits of Assembler are compensated for.
Small (~3mmx2mx2mm for the 10F222), light, tolerant to -40C, 175uA @2V power consumption (i.e. a week of a watch battery) and sufficiently fast. Sounds perfect for this project- now we've just got to find the other equipment!
" "...and before you know it we've become Lockheed Martin."
Does this mean that those of us who are Lockheed Martin employees cannot assist in this project, due to a desire to avoid becoming Lockheed Martin?" ... By Anonymous Coward Posted Tuesday 11th August 2009 20:50 GMT
A Passionate Desire to be a Lead AIReplacement Component Element for Lockheed Martin would Server Everyone Better with Cutting Edge Virtual Technology and Astute HyperRadioProActive IT Methodology, AC. Although that takes an Offensive Defence Contractor/War Scenario Producer like Lockheed Martin into Imaginative Territory which Realises War as the Tool of Fools and the Mad and the Bad and/or the Criminally Insane if you want to be Insanely PC.
* In a Gangster/Family Movie context, that would be as a SMART Offer IT would be Foolish and Insulting to All Parties not to Savour and Enjoy and Support.
With Ye Olde Trojan Horse's Head in the Bed Routine, a Following Folly for the Slower Witted and/or Unreasonably Implacable/Unnecessarily Obstructive ...... the Ignorantly Impudent.
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