Wasn't sure where to put this, but they aren't really water rockets, so off-topic seemed fine.
The most basic design is stupid easy. Fill a film canister with water, drop in Alka-Seltzer tablet, quickly put on cap, flip over onto the ground, step back, and watch it go without all the effort of building the pressure up yourself. Best of all, a rocket and setup costs probably about 10 cents, and most of the stuff you probably already have (except maybe the film canisters). Alternatively, you don't flip it over, and just set it down right side up, and the top will fly instead (but it is less rockety).
I realized a few days ago that a two stage rocket could be built very easily. Simply hot glue a film canister cap to the bottom of another film canister. This allows you to connect two film canisters together. If you make the top stage tighter by using a slightly different cap or canister and/or put only a piece of an Alka-Seltzer tablet into it, slowing the production of gas, The stage will release after the main stage, especially if you glue or tape the tablet to the cap and don't let it touch the water until you flip it over on the launchpad. I also added some basic rectangular fins and a paper nosecone with a rounded hot glue dome to improve the flight. I have yet to test it though, so the staging is still theoretical.
Thoughts? Ideas? Experiences to Share?
Alka-Seltzer Rockets
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Alka-Seltzer Rockets
Beware the Purple.
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Re: Alka-Seltzer Rockets
The challenge with this idea is getting the second stage to fire off when you want it to. The launch timing is somewhat random because it depends only on friction working against the pressure which builds at a rate depending on the temperature and ambient air pressure. It could probably be done if you were to make a rocket that had a longer flight time which would increase the chance the second stage would fire while in the air.atvan wrote:Wasn't sure where to put this, but they aren't really water rockets, so off-topic seemed fine.
The most basic design is stupid easy. Fill a film canister with water, drop in Alka-Seltzer tablet, quickly put on cap, flip over onto the ground, step back, and watch it go without all the effort of building the pressure up yourself. Best of all, a rocket and setup costs probably about 10 cents, and most of the stuff you probably already have (except maybe the film canisters). Alternatively, you don't flip it over, and just set it down right side up, and the top will fly instead (but it is less rockety).
I realized a few days ago that a two stage rocket could be built very easily. Simply hot glue a film canister cap to the bottom of another film canister. This allows you to connect two film canisters together. If you make the top stage tighter by using a slightly different cap or canister and/or put only a piece of an Alka-Seltzer tablet into it, slowing the production of gas, The stage will release after the main stage, especially if you glue or tape the tablet to the cap and don't let it touch the water until you flip it over on the launchpad. I also added some basic rectangular fins and a paper nosecone with a rounded hot glue dome to improve the flight. I have yet to test it though, so the staging is still theoretical.
Thoughts? Ideas? Experiences to Share?
It sounds like an interesting challenge.
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Opportunity is missed by most people because it is dressed in overalls and looks like work. --Thomas Edison
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Re: Alka-Seltzer Rockets
The cap I have on the second stage is pretty tight, so I think I'm going to use a single tablet in each rocket stage. I hoping for the second stage to fire about half a second after the first stage. Even if it right after the first stage, it will still be a significant improvement over a single canister, because it will essentially be twice the thrust.
Beware the Purple.
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Re: Alka-Seltzer Rockets
If you can set it up so that the first canister causes the second one to release, then you will solve the timing issue. Some latch that releases when the first cap comes off would be a good way to go.atvan wrote:The cap I have on the second stage is pretty tight, so I think I'm going to use a single tablet in each rocket stage. I hoping for the second stage to fire about half a second after the first stage. Even if it right after the first stage, it will still be a significant improvement over a single canister, because it will essentially be twice the thrust.
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Re: Alka-Seltzer Rockets
The wonder of these rockets is their simplicity. If what I have doesn't work, I might try something like that though.
Beware the Purple.