Guest kevo214 Posted July 21, 2004 Share Posted July 21, 2004 I recently received a challenge/project in which I need to shoot a water/air pressure powered bottle rocket into the air and get it to stay in he air for as long as I can while not breaking and egg that has to be somewhere on the rocket. Here are the rules I received. Material: 2- 2 Liter Soda Bottles (minimum) 4 File Folders Duct Tape 1- Large Egg (App. 70 gr.) **No Metal Guidelines: 1- 2 Liter Bottle for Fuselage No more than 60 PSI of air Total Length, 9ft or less Total Weight, 300 grams or less **No Metal, explosives, or other fuel Rules: 2 Chances, 1 with each rocket Add as much or as little water as you want No more than 60 PSI Time is measured from launch to the first item that hits the ground 10 - Seconds to remove the egg -stronaut If egg is broken you get time If egg survives you get time X 2 So from what I gather the materials are not mandatory just suggestions and I can use almost anything. The one thing I am not sure of is if the 300 gr. limit includes the water but I will update later with more info. I wanted to know if anyone can help me with the design and if you can please post or email me at kevo214@si.rr.com Thank you for your time. Link to comment Share on other sites More sharing options...
LucidDreamer Posted July 31, 2004 Share Posted July 31, 2004 If the challenge is about keeping the rocket in the air for as long as possible why not use a parachute that ejects after it reaches maximum height. It would help protect the egg from breaking as well. Of course your instructor may have thought of this and made a rule against it. Link to comment Share on other sites More sharing options...
rbp6 Posted July 31, 2004 Share Posted July 31, 2004 I recommend trying a velcro strap thingie to hold the egg in the rocket. i.e suspend it somewhere in the center of rocket. like the velcro would be holding it in air. Or at least I think that would be the easiest way to hold it. Link to comment Share on other sites More sharing options...
drz Posted August 9, 2004 Share Posted August 9, 2004 A plastic bottle can hold alot of psi. I've had a 20 oz bottle up to 60 psi. I was trying to launch something out of the bottle though. It worked pretty good, would launch a paintball further then walmart guns. Anyhow, if you have to launch the bottle itself, you would need some kinda nozzle that would force the flow of the air out through a smaller hole, maybe several holes. You would want the egg to be about dead center in the craft, to high or to low will cause that side to plummet to earth. The velcro idea sounds like a good idea, but remember, duct tape is good enough for Nascar. Link to comment Share on other sites More sharing options...
Dave Posted August 9, 2004 Share Posted August 9, 2004 Perhaps have the egg located in the nosecone of the rocket for stabilities' sake? Plus that allows for extra padding etc. Link to comment Share on other sites More sharing options...
Stusi Posted August 24, 2004 Share Posted August 24, 2004 We did an experiment similar to the one your doing minus the egg. What we learned is, nose heavy is best for stability. If it is back heavy it will have a very random flight pattern, and will most likely break the egg. Also, no one ever figured out the exact amount of water, but i did make a smaller "nozzle" out of a form of epoxy so my force on take off was greater. Sadly my rocket was very light (had very little weight in the nose) and it didn't go too high. Also small fins for stabilization are good. No need for anything too big. Hope this helps, and let us know how it turns out! Link to comment Share on other sites More sharing options...
swansont Posted August 24, 2004 Share Posted August 24, 2004 Also, no one ever figured out the exact amount of water That should be easy to estimate, if you know the pressure. Assuming an isothermal process, PV will be a constant. P must always be greater than atmosphere to eject the water, so you want to make it so that P is 1 ATM when the volume is that of the bottle. If you can pump to 2 ATM, then you want half air, half water. 3 ATM, 1/3 air. Add maybe a 10% safety margin (more air) to make sure you're ejecting all the water with a downward velocity. Link to comment Share on other sites More sharing options...
5614 Posted September 7, 2004 Share Posted September 7, 2004 i once saw a guy do this, but with slightly different rules, he did electrolysis on water and used the hydrogen and oxygen as a fuel, the only thing was that is was soo powerful it melted the bottle, which was plastic, but i dont think that you can do electrolysis and it wont work in a plastic bottle. remember you said you wanted time in air, not height, something which goes up quickly isnt as good as something which goes up slowly, a massive parachute to slow down the descent and save the egg is a good idea. compact the air as tight as possible [i think there's a limit in the rules] if you are confident that you can do it right, use two different rockets, but if one is likely to fail, use two of the same... remember the rule first thing to hit the ground stops the timer, so you cant have a parachute behind a lid, coz the lid can't fall off as it would hit the ground first. Link to comment Share on other sites More sharing options...
Guest Garyr Posted October 9, 2004 Share Posted October 9, 2004 I did the water/botle rocket thing a while back. The 60lb. air pressure will be the limiting factor. Real short flite if at all. The nossle will be a challenge, start whith a hole in the bottle cap. Get a lot of bottle caps. This will be where 90% of your work will be, not with the egg. Was easy for me, I have a machine shop to work with. GaryR Link to comment Share on other sites More sharing options...
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