PARIS emerges triumphant from hypobaric chamber We know you lot haven't been able to eat or sleep pending the outcome of Monday's test of our Paper Aircraft Released Into Space (PARIS) Mk 2 release mechanism, so here's the news: it works. For PARIS newbies, we should explain that said mechanism is the pressure-operated device which will release the Vulture 1 aircraft. It's …
Sod the LHC...
However, "One thing is certain, though: the Mk 2 will definitely release the Vulture 1, and whatever the final altitude, it's going to be a bloody long way up" - it looked like about a meter to me in the video... ;)
--Paris, 'cos it's PARIS (and I work there)
With proper calibration, it would allow for much greater precision in the release altitude, and also negate the need for a massive amount of travel for the piston... An inch would be more than enough.
Good thinking, that man.
Otherwise, carry on Lester. Any idea of a launch date yet?
Just posting to agree with Steve. Adding a spring is a damned good idea; that contraption is far too large given the function it's performing.
Furthermore, the accuracy is pretty poor. Didn't you say 20'000 meters was the target? You've barely made half of that with the Mk2. It may not matter given the project has no real purpose, but a system that missed the 20'000 meter target by 50% is making the engineer inside me cry.
To be honest it seems like you've bent over backwards to accommodate this need for a mechanical release mechanism. An electronic system could perform this function with much less weight, size, complexity and much more accuracy.
We didn't miss the (arbitrary) release target by 50 per cent, we missed it by 10,000ft. It's a metres/feet thing. QinetiQ's Tim D'Oyly pointed out that we hadn't taken into account the air contained between the aluminium oxide grit particles, which accounts for the slightly early drop.
We could have added a tad more grit and rerun, but decided that we were happy with the thing the way it is. It's a matter of suck it and see on the day, but it will certainly work, which is the most important thing.
Regarding the other objections to the mechanism, we don't need a spring or a shorter device, because we're going to use the distance of travel of the plunger, and therefore the total length of the main payload box, to our advantage, You'll see why in due course.
The rubber oxygen tube will not freeze, or come anywhere close to it, since the whole mechanism will be heavily insulated.
Finally, we've been over the idea of an electronic release mechanism before. In a word: pah. There's just not enough shed boffinry involved, and its bound to go titsup anyway.
Brilliant solution on the powder. But I'm still not clear on the concept. Why is any "ballast" needed in the tube? It seems to only be there to occupy space, to displace part of the air in the tube. It might have been easier to just use the proper length of tube, which would contain just the right amount of air to yield the proper expansion.
Also, it's good that you dealt with these temperature issues, but I still would be concerned that the rubber tube will freeze up in action. Maybe you should test it at lower temps with dry ice, see if it still stays flexible. It would probably be unnecessary to test it at both low temp and low pressure, if it passes the low temp test separately.
> It would probably be unnecessary to test it at both low temp and low pressure, if it passes the low temp test separately.
Not necessarily...
The amorphous, polymeric structure of the rubber can become brittle at low temperatures, making it much less elastic, and thus more prone to fracture. This brittleness, combined with the higher pressure contained within the expansion tube (relatively, as the outside pressure drops as the device gains altitude), can cause the rubber to crack at the inner/outer "accordion" edges. The problem is that the rubber's amorphous structure makes it difficult to predict its failure modes with a high degree of precision. The only way to know for sure how the device is going to react to the low temperature environment is to test multiple samples under stress, take a weighted average, add a certain amount of safety margin, and then build the production device accordingly.
And the temperatures don't even have to be all that low, either: In 1986, a bunch of bigwigs at NASA and Morton Thiokol were convinced that the rubber O-Rings in the Space Shuttle Challenger's Solid Rocket Boosters would remain elastic and flexible, and thus respond gracefully to the high pressures in the SRB fuel casing, at a mere 34 degrees Fahrenheit (1.1 C). They decided to go ahead with launch, even though a bunch of in-the-trenches engineers indicated that launching at such low temperatures would be very risky. Furthermore, it has been suggested that overnight temperatures at the pad could have fallen to below 20 degrees Fahrenheit (-6.7 C). (During the pre-launch inspection undertaken that morning, a record low temperature of 8 degrees Fahrenheit (-13.3 C) was reported by an infrared camera pointed toward a location on the right SRB, near the joint that failed. The inspectors decided that the reading was "erroneous.")
Won't temperature changes also be a problem with the calibration. If the thing is insulated the air inside will stay warm(ish) and less dense creating a further pressure differential with the air outside essentially releasing the spacecraft early, won't it?
This seems like such an obvious problem I'm guessing you have already thought of it or I'm missing something??
Though whether it's good idea to share all this info is an open question. You've probably got a more reliable, cheaper and less expensive device than BAE has ever managed. You should probably try dropping a nuclear weapon from PARIS 2 and get into the defence/mad dictator business.
This is getting really exciting. I do hope that the Reg will soon have a huge NASA style countdown clock on the front page, perhaps with the very lovely Ms. Bee actually doing the count to zero.
You might want to check these videos for some tips on the payload construction etc.:
http://www.vimeo.com/12421661
http://www.vimeo.com/13891367
Though he has somewhat larger payload allowance - 1240 grams instead of 500... but he used 2 cameras and it was in America, where everything is bigger, as we all surely know.
<PEDANT>
You've got an "oxygen tube" inside a "PVC tube".
PVC is quite rigid and easily formed into a tube. I am happy with that bit.
But how do you make oxygen stay in a tube shape and prevent it from diffusing into whatever surrounds it?
Do you mean "tube with oxygen in"?
Also, it sounds like you're not going to fill it with oxygen, just "air".
Maybe : "rubber tube containing mostly nitrogen" ?
I don't know much about rubber, but it's probably some sort of poly butyl something or other.
And it's got your Aluminium oxide in too.
</PEDANT>
Having previously posted recommending a much lighter approach to this simple problem
( a squash ball or such in a ~ suitably calibrated (cardboard) vessel tripping a (string?) release mechanism ~etc. ) , I must now humbly ask elReg to think of the children.
When the nobly-conceived constructed and, we all fervently hope, airworthy PARIS' luftballon bursts, one " MKII "* of ironmongery and plumbers hardware will plummet to earth somewhere. Are PARIS' risk managers considering the outside chance of clocking say,
< some CTO > worth the equally outside chance of hurting a non-participant ?
* I make an advance claim ( to the " MKII " as a " measure of nasty things falling on your head from altitude " - ?in Nm/cm2? ) in the event of the worst.
Badgers, because if Paris knew, she'd think of the badgers too wouldn't she ?
20100916
THE GRIT MUST BE DRY!
THE GRIT MUST BE DRY!
THE GRIT MUST BE DRY!
Ok is that clear... bake it in the oven if you like. (If it is not dry it will freeze into a solid lump.)
I still think you should pop down the hobby store for some plastic soft air BB pellets. They are about half the weight of ALOX Grit. though youd probably have to fill the whole tube, and rely solely of the void air. Unless of course weight is not an issue...
Having previously posted recommending a much lighter approach to this simple problem
( a squash ball or such in a ~ suitably calibrated (cardboard) vessel tripping a (string?) release mechanism ~etc. ) , I must now humbly ask elReg to think of the children.
When the nobly-conceived constructed and, we all fervently hope, airworthy PARIS' luftballon bursts, one " MKII "* of ironmongery and plumbers hardware will plummet to earth somewhere. Are PARIS' risk managers considering the outside chance of clocking say,
< some CTO > worth the equally outside chance of hurting a non-participant ?
* I make an advance claim ( to the " MKII " as a " measure of nasty things falling on your head from altitude " - ?in Nm/cm2? ) in the event of the worst.
Badgers, because elReg should think of the badgers too.
20100916
Now I'm no engineer but doesn't it make sense to include a back up release mech. Surely pinning all you high altitude release hopes on one device on such an important project seems cavalier. Lots of egg on face if it doesn't release, and it's not egg we wish to see on Paris's face.
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