Lots of fun
Sometimes you can learn an awful lot just by playing around. Looks like this was one of those occasions. Thanks for letting us "watch".
Tuesday saw the Paper Aircraft Released Into Space (PARIS) team down at QinetiQ's hypobaric chamber in Farnborough, testing the crucial Vulture 1 aircraft release mechanism. As we've previously explained, just how to get the Vulture 1 to separate from the main payload at a more-or-less predetermined height has given us plenty …
Sometimes you can learn an awful lot just by playing around. Looks like this was one of those occasions. Thanks for letting us "watch".
Pretty obvious failure of the ground-glass syringe... you thought it would form a perfect seal?
You need a rubber diaphragm as the seal and something lubricated as the slide, so there's very little stiction. Alternatively you *may* get away with wetting the ground-glass surfaces with a gloopy but low-vapour-pressure oil.
I'm just kidding. Great work! Interesting stuff! I'm looking forward to the culmination of the PARIS project.
Put a balloon inside the syringe? Well sealed, containing at least 15cc air but not inflated.
In fact, you can probably do away with the syringe altogether and use, say a toilet roll carton tube core, closed from one end, containing the balloon and some sort of an actuator (a pencil?).
I would imagine balloon rubber at the seriously sub-zero temperatures of ...
... -56.5 Celcius seen at 20,000m would behave more like flaky pastry. not sure how well vaseline would work at that temp either.
Wrap it all up in a few layers of cotton wool and put a layer of tinfoil on top. The cotton wool will keep it warm while there is still atmosphere and then the foil will reduce the heat loss due to radiation in vacuum.
My thought was that to keep it in tune with the rest of the project, a condom containing some air and with a knot tied in the end, ought to expand at a reasonable enough rate so that if contained in a toilet roll tube, would push something out of the end quite readily.
I have memories of a night in the pub many years ago when someone decided to inflate a condom and it was well over beach ball size when it finally exploded so it'll take the strain.
You've just reminded me, if you're intending to use the flycam without an external power source you need to watch out. Once they get cold they shutdown surprisingly quickly.
In the lab we always smear a light coating on vaseline (or equivalent) on the plunger of our gas syringes against such an event - did you forget this simple precaution?
For the device to work, you should try to apply a coating of oil to the inner glass. It will ( providing the oil don't freeze) seal and lubricate it.
Just one more test.
Nah, the cheap and cheerful method is to use an extremely loose-fitting plunger, such as a large syringe with the rubber bit removed, and a tied-up balloon inside. The balloon will be fairly leak-proof at low pressures, and the loose-fitting piston has very low friction.
Should spend a little time looking at how people actually build low-temp Stirling Engines.
Of course, ripping apart an old pressure gauge is arguably more reliable, and not exactly expensive compared to the electronic kit.
What no pressure balloon trigger? why not just pop down the local aircraft scrapyard and pinch the mechanicals of the back of an altimeter. easy!
as for the test, sounds like not enough vaseline on the plunger...
"....the air had time to sneakily escape between the ground glass plunger and the syringe interior wall."
What happened to the placcy one? Those usually have a ridged rubber thingy* on the end of the plunger which should give a better seal. You might want to apply a smear of silicone grease to the thing first (you want the plunger to move smoothly and contamination of the syringe contents isn't an issue).
I'm impressed with the chamber though. 8,000 to 65,000 feet in 0.1 seconds? Makes my ears hurt just thinking about it.
*Stop laughing at the back there.
> I'm impressed with the chamber though. 8,000 to 65,000 feet in 0.1 seconds?
> Makes my ears hurt just thinking about it.
I cringe when I think about these things because the Nazis put actual living people (well before anyway) in these things.
Makes me ashamed to be a German.
BB icon because he looks a bit like Hitler.
Also, on the upside the Nazis (not just Germans- don't beat yourself up) kept pretty good records of these things. So we'll not need to do this sort of thing again.
We just need to make sure that we never forget those who were tortured and killed for these data.
Go down to Halfords, distract the sales-weasel, and steal one of those cheap'n'nasty turbo boost gauges (or even better, a manifold pressure gauge for a non-turbo car, since they have better resolution). Take the glass off, and use the needle to trigger your release mechanism.
You're looking for about 5kPa at 20,000 metres; another trip to your friendly hypobarycist will confirm the actual position of the needle.
Some Vaseline, or similar, should allow the plunger to slide more easily and make a gas-tight seal.
Alternatively -- put a water balloon filed with air in the syringe?
... put a small sealed balloon to contain the air reservoir inside the syringe? Something thin but very strong would be required. Probably latex would be best, if it were lubricated it might help the movement of the plunger ....
... Hey. now there's an idea that ties into the Paris theme quite well.
What about a latex glove? Inflate the lubricated index finger to press the release mechanism.... in keeping with the (ahem!) theme of the experiment...
Only let down by the inexplicable absence of anyone smoking a pipe.
Could you use a common-or-garden balloon in a tube - partially inflated? As the pressure drops - regardless of the rate of ascent - the balloon will expand, and push against whatever it is you want to push at the end of the tube at the right time.
Or, why not just use a good old-fashioned altimeter? Is it too high-tech for this project?
What about a knotted partially inflated condom as the air reservoir insider the cylinder/piston assembly? No leaks that way, and you can use a simple and light unit as the piston seal is non-critical. This has to be the way to go if only because of the awesome double-entendre potential.
for those who remember the above equation: are you sure that you can take temperature into account properly? Can be really low up there or rather high if you get a bit of sunlight.
Anyway, what'as wrong with a membrane-type manometer? Engineers have optimised devices for the application 200 years ago. A sliding design is obviously plagued by stiction(*) problems and so, said engineering forefathers used a rotating design. You amateur approach to this buys you no geek points.
I'm really interested in the actual craft! When are we being treated to drafts of the paper Aeroplane, please?
P.S. Yes I'm taking this way to seriously: but we all want to see this thing work.
P.P.S Paris icon because <insert pressure-related sexual double-entendre here>
(*) that word rolls off the tounge quite easily if you've heard it before
If anyone is kicking themselves based on th above posts for not thinking of the ideas mentioned above ?
Do you have a photo of the boffins' expressions when you unveiled your, er, impressive high tech equipment?
p.s. I note other correspondents are recommending forms of lubrication for the equipment. Is there not a danger of causing PARIS to be involved in a premature emission?
someone trying to get corporate compensation for using stuff from their 'extreme porn' toy collection?
..put a little person in the aircraft and when they think they're high enough up they can just let go? You could give them a Reg' branded iPod to take pictures on the way down and send out twits at various points of the descent.
I'm no expert (hence eminently qualified to spout forth on this forum), but I'd imagine that rubber balloons would freeze at such chilly altitudes, presumably the reason a glass syringe was chosen.
I reckon the PARIS team should have a 20,000 ft tether and a simple trigger release...
I see a potential problem that could ruin the mission. Civilian GPS units have built in hardware limitations, and won't track if the speed exceeds 999 mph, or altitude goes above 60000'. This to prevent the ilks of Kim Jong-il etc. from building a cheap missile guidance system.
Is it a hardware or software limitation? AC for obvious reasons.
As they've stated more than once, the GPS is NOT intended to track the flight but to allow recovery once it's back on the ground, therefore altitude and speed limits are irrelevant.
The suggestions above to use an altimeter are good, but I have a simpler and probably lighter alternative.
Basically we need the pressure at 20,000m (at 16km it's 0.1 atm) to trigger the release. That implies a 10x expansion... for now I'll imagine the last 4km of pressure change will be consumed by the trigger's mechanical force, to keep things simple.
The problem with the syringe is the small piston area compared with the volume contained therein. Also, the glass syringe is delicate, expensive and fiddly. But if you had a large plunger, say 10cm diameter, the force it exerts will increase by the square of the diameter ratio, so you could get a much larger force to do the work.
Let's suppose you chose a tuna can. Now, obviously an opened tuna tin is lousy at containing pressure, but if the edges were machined smooth it could be a dandy container for a semi-inflated condom (PARIS never leaves home without one, natch). As the rubber expands it will press on the lid; on the lid, perhaps soldered or welded in place, is a single-edged razor blade. The pressure from the lid will push the blade into one or more monofilament fishing lines, which are tensioned and connected to release the plane and what-have-you.
The expansion force from this cylinder should be well above what any syringe can muster, its operation will be basically frictionless and I can't see it weighing as much as a glass syringe. The response of the lid to pressure can be controlled by springs and by the initial volume of air, thereby allowing a pressure response tailored to your needs (another thing PARIS is good at).
The only question to determine is the response to –60°C temperatures found at that elevation. Perhaps latex is not the best choice there, but a latex-free condom may work better. I guess you need to buy a lot of condoms and test them out!
Using this idea but without the need for razor blades and fishing lines:
A Tupperware or similar container with a press on lid.
Container or lid (or both) perforated to allow pressure to equalise.
Container attached to lifting balloon.
Insert semi-inflated balloon into container.
Attach lid to plane and seal container with semi-inflated balloon inside.
When pressure causes balloon to expand enough to pop lid from container, separation has been achieved.
Not sure what container would be best. Perhaps old plastic 35mm film canister?
Also not sure if having lid attached to plane is within percentage of craft made of paper tolerances, but if you're attaching all sorts of electronics I can't see it being a problem.
How about a partly inflated balloon, attached at one end to the plane, and on the other end to the lifting body. At a certain altitude the balloon bursts, and PARIS flys free.
However, I'm not sure how repeatable that would be.
While 'preservatives' are individually tested at manufacture, I don't know what tolerances they work to.
So that's something to try out at Qinetiq - put an entire boxful of thin-walled balloons blown up to equal pressure into the chamber and see whether they burst almost together or widely spaced.
Where is the T shirt???
I want one for my hols.
Mount the syringe vertical - Pointy end up. Add some vege oil plus the 15cc of air. Air should sit on top of oil and push down on the oil/plunger.
So rubber is going to go like "flaky pastry" and batteries will probably die halfway through the journey without protection. So..
..what about those chemical hand warmers that you'll see in hunting and fishing shops? Expose the bag to air and give it a shake and it gets nice and toasty for a couple of hours. Maybe wrap the sensitive components up with a couple of these and something fluffy? How long's the flight expected to be?
For the lovely QinteQ people to offer us another day, and throw it open to Reg readers to design and build devices that'll work at -56C and 70000'. Then we can all get boffining in our sheds, and test the whole darn lot in one go. I think we all //really// want this to work, don't we?
It's not that hard to keep electronics working at -56C if they have been started above freezing. Think of retaining all that lovely waste heat they generate.
Starting them when cold soaked to -60C - now there's where I earn my wages!
Put the paper plane inside the balloon!!
I have one if you need help.
Put the plane inside the balloon. When the balloon pops at altitude the plane is free to fly!
Simple, no plungers or mechanical thing-gummies to choke up the works.
Back to QinetiQ and test balloon pop altitudes.
I believe I saw this experiment on a talk show--or was that YouTube? It was something to do with toy balloons and water. Can't think of what might happen if you mixed those two.
I could have sworn my science instructors did the same things at university, but only in demonstrations to the incoming classes. The upper-classmen would have laughed at these sorts of things.
Re-entry: After decades of research, astrophysicists and aeronautical engineers have identified several fatal flaws in what is commonly called "Non Rigid Technology, or NRT". Strange, and poorly understood, forces come into play at sub-sub-sub-sonic speeds - particularly at the atmospheric littoral. Crumpling, wrinkling, and flapping are common but lesser known forces such as trailing-edge tattering - that can lead to dog-earing - have also been modeled. Moderate to severe dog-earing is predicted to cause such great aerodynamic stresses that the structural integrity of load-bearing creases can no longer be relied upon and catastrophic failure is predicted in nearly all scenarios. Without its rigid heat shields, the Space Shuttle would crumple like a used tissue on re-entry.
Approach: Without a doubt, and unknown to most lay folk, atmospheric transit is the most dangerous stage of any space mission. At post-reentry speeds bird-strike is an ever-present and deadly risk. For NRT craft, bird-peck and bird-crap further threaten the chances of a successful mission. The massive forces of the Earth's atmospheric air currents are also a source of danger. "The Trade Winds", "The Roaring Forties", "Twister Alley", "The Tropical Easterly Jet", "The Middlesborough Zephyr", "The East Covington Highstreet Eddy". An aircraft will be tossed about and beaten a dozen times before it even has a hope of landing.
Landing: Seventy percent of the Earth's surface is covered by ocean. A further twenty percent is covered in seas, lakes, permanent ice, rivers, ponds, hidden bends of streams where summer romance blossoms beneath the willows, standing puddles, half drunk cups of tea, and beer (both pre- and post-micturition). This means that there is a 90% chance of a water-landing. Even with a hull rated to depths in excess of 0.000546806649 fathoms a splash-down is a high-risk exercise for an NRT. A landing on solid ground is similarly fraught. Assuming a suitable landing site can be found with the pre-requisite length, width, and load bearing characteristics, keeping the site clear of vehicles, pedestrians, onlookers and curious puppies, until the NRT can be made safe will be nigh on impossible.
Conclusion: I think few will disagree that the chances of a successful mission outcome are negligible. It is more likely that the PARIS crew will suffer some horrendous calamity upon re-entry or, perhaps more terrible, remain trapped in Low Earth Orbit awaiting rescue, cannibalism, or a ringside seat as the Earth is finally destroyed by some massive global climatic event or nuclear calamity. All that we can hope for, for their sake, is that they might see the insurmountable risk before them, be steeled by resolve and camaraderie, and take their emergency cyanide pills as they sit, waiting, on the launch pad.
We are not talking about orbital reentry speeds here! Vulture 1 will be nearly stationary at the time of the drop. Humans jumped from such heights with nothing but a pressure suit and a parachute and survived - and humans are pretty soft, you know.
Instead of the regular syringe, why not employ a roll-sock seal. If the stiction is the real sticking point, there is always graphite on glass pistons such as the type available from airpot.
I would have thought, given the project's title and sense of humour, some sort of contraption based on a Bulgarian Airbag or a condom might have been used.
I'm just saying.
Yes, mine's the one with 'Benny Hill' on the name tag. yackittyyackittyyackitty....
What do they make weather balloons out of then?
...are made of metallized Mylar, I believe.