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this instructableWater Bottle Rockets are a terrific demonstration of Newton's Laws of Motion. I have been launching these rockets with my 7th graders for the past 10+ years. After a number of prototypes, I'm ready to share a project that anyone can build and test. The best part, it only takes about an hour to build! These rockets will easily fly 150 feet with some of the better projects traveling well over 300!

Warning! There is always risk involved when subjecting bottles to high pressure. There is also risk due to the uncertainty of where a rocket may land. Keep all spectators behind and away from the launch area / anticipated landing area.

Step 1: Reduce, Reuse, Recycle

Picture of Reduce, Reuse, Recycle

Want to know what's better than buying your own 2 Liter soda bottles? Raiding a neighbors' recycling or taking a few bottles home from a party you've attended/crashed. Although it only takes about 1 hour to build one of these rockets, I give my students 3 weeks notice (so they can find creative ways to collect the bottles). If your hunt for used bottles is a bust, you can almost always find a brand on sale. This year, I found a 5 for $5.00 deal on Pepsi products. I prefer the Pepsi bottles over the Coca-Cola brand bottles because of the shape of the bottles. We purchased A&W Rootbeer to make a few rootbeer floats and poured the rest down the drain.

flagman121 month ago
what is the propellant
They use compressed air - there is no chemical propellant.
And H2O!
Yes, of course! The water is important too.
Biodynamic (author)  flagman121 month ago
Don't forget the water!
Eh Lie Us!1 month ago
Wait, they got rootbeer floats before the hard work was done? I'm calling FOUL! :)

So, so, so great to see kids (especially the girls!) doing this. Thanks for posting and good luck. The sky is the limit.
Biodynamic (author)  Eh Lie Us!1 month ago
Thank you! One of the girls for my cover image is my daughter. My son wrote his name in big green letters across her project when she asked him to help decorate it. I love seeing all of the kids be successful, but it's especially satisfying when I can convince a young lady she's great at science/engineering despite her own preconceived notions.
Yes, indeed! We all have a lot more work to do. Every bit gets us closer and closer. Thanks again for what you do.
chhackm1 month ago
A great reminder: I used to do this as a kid - a very long time ago. Back then I used a single bottle... which is the reason for this comment: it was only at the very end and on review that I realised there was no apparent purpose for any bottle other than the bottom one! Can you make it clear at the outset that the other ones are not going to have any propellant function, and also why they are there? My guess is for aerodynamic stability - which might also be achieved by angling the fins, but it's a trade-off between increased drag from angled fins and increased weight from adding length.
Biodynamic (author)  chhackm1 month ago
After launching hundreds of these rockets I've found that 3-4 bottles work best. A single bottle doesn't have enough mass to fly very far. The weight of the fins on a single bottle makes the majority of the mass towards the back of the rocket so the rocket tries to flip around mid flight. You would have to add some weight to nose to get it to work. The center of mass of the rocket should be centered or a little towards the nose. Thanks for the feedback!
DavidR8851 month ago
Tip 1: Before hot gluing the fins on, fill the bottle with water so the plastic bottle does not melt.
Tip 2: use ballast weights in the nose
Tip 3: Check out Air Command Rockets. They are boss at this. They show how to join multiple bottles to make a larger pressurised volume as well as multiple stages, parachute deployment and flight recording.
Biodynamic (author)  DavidR8851 month ago
I like the idea of filling the bottle with water before gluing the fins on. The bottles often warp due to the temperature change when they're empty.

I know some extra weight in the nose is great, but it also makes me nervous because it makes them a lot more dangerous on the way down!

I'm definitely going to encourage a few kids to try joining bottles next year. Thanks for the link.
LeeDr8501 month ago
We did these with my Cub Scout pack with a few differences;

We figured out that a garden hose in some areas has about 90 PSI pressure so we just slide a bottle down onto a PVC pipe that we had heated up (like with a candle) and pushed to make it swell a bit. Push the bottle down pretty hard on to that and turn on the hose. You end up with about the right amount of water and compressed air in the bottle. The bottle releases once the pressure gets high enough. I know, it's not very accurate but it's super-simple. I'm sure there's instructables showing this technique.

I purposely angled all the fins on one bottle the same direction so it would spiral as it flew (like how a bullet goes through a rifled barrel). This seemed to make it fly straighter.

We generally used a single bottle for ours. We hot glued foam board fins on. We made nose cones out of paper and taped them on (they didn't last once they got wet but they also won't hurt anybody if they fall on you).

WARNING: A 2-liter bottle like these falling down on a car could put a small dent in it so make sure you're clear of parking areas.
Biodynamic (author)  LeeDr8501 month ago
One year I parked under a big maple tree about 130 yards out. A rocket came straight down and knocked the grill out of the front of my car. Ever since, I have sent emails to all the teachers and staff not to park down range. I put up signs the week before. I still have teachers who park up on the nearby hill despite the warnings and the high probability they may end up with a dent in their car.
I have done these for many years as an introduction to powered rockets for students, the use of a compressor is one I used myself. The best tip I can give though (and I tested this Idea many many times) don't pour the lemonade or contents away but use it to power the rocket instead. I found a pretty significant gain in distance. I think the CO2 bubbles in the fizzy drink compresses a little.
Nothing to lose.
Best wishes
Biodynamic (author)  Dragonavionics1 month ago
Very interesting! As much as I'd love to try it, I'm not sure I want to get sprayed with soda all day. I'll probably test it with one or two rockets for comparison though. Thank you.
paskidog1 month ago
Nice project! My only concern is your choice of launch sites. It looks like you sent the "rockets" up directly beside a 3-phase power line..... not a good idea! just sayin.
Biodynamic (author)  paskidog1 month ago
Thanks for the warning! Since I know very little about 3-phase power lines, what could potentially go wrong? We don't have parachutes that might cause a rocket to get hung up on the wires.
"Use packing tape or duct tape to join the bottles at the seams. "

I think the 'flimsy' plastic packing tape (that brown stuff) would prove a better/lighter choice than the thicker, heavier duct tapes I am familiar with.

That flimsy stuffs been good enough for UPS for decades!

Great project, looks as if you've inspired a few rocket scientists and creative 'types' too!
Biodynamic (author)  charlessenf-gm1 month ago
Thank you! I agree that the duct tape can add too much mass, especially if they cover the whole rocket with it.
How does the launching mechanism actually work? I couldn't find a
close-up video of it in operation, and Amazon and the other retailers
featuring it didn't give any details or sufficiently helpful pictures.
PRR54061 month ago
I was at an NSTA conference where we were told these bottles are pressure tested to 5,000 psi. Whether that's true or not, I can verify. You have a flight testing situation where you have to balance the weight of the water content versus the amount of air pressure introduced into the bottle. This can be graphed and figured out for lifting payloads (like eggs).
The thing that has always baffled me has been building staged water rockets. People have done it, but I have never been successful in getting a pressure resistant air seal. My kids loved doing this project each year. I think we did get one to hit about 300 feet. I believe there was once an altitude prize offered for the perfect rocket! There are hobby groups for this technology on line.
Blue Hawaii1 month ago
Step 2, first paragraph, "This bottle will serve as the bottom of your rocket and must hold the
water and air pressure. This bottle will not be referred to as the
BOTTOM BOTTLE." Change "not" to "now".
MyrrdinCCR1 month ago
I launched these rockets in my classroom for 27 years. In the later years, I made sure I used a low temp glue gun/glue sticks. I had students put the glue directly on the bottles and melt a hole or weaken it enough to cause failure.
jwhit2 months ago
Do you pressurize both bottles simultaneously? I'm a middle school science teacher (Grade 8) and have done water bottle rockets in the past and would like to do them again. My launch mechanism kept breaking down but yours looks interesting.
Biodynamic (author)  jwhit1 month ago
I pressurize one bottle at a time. After hooking up the air compressor I count to 10 and then move to the second bottle and do the same. You can hear/see the air rush into the bottles. By the time I count to 10 there are usually just a few bubbles trickling in so I know the pressure is about equal between the bottle and the compressor.
Dumbphone1 month ago
Excellent tutorial! Looks like everyone had a great time. Thanks for sharing.
AnglinaSmith2 months ago
its very nice presentation i am very glad about you
JGB2 months ago
Bravo.... It is a nice presentation.

You may want to go back and revise where you tell us where to order the kit and to ignore reviews as you will show in step 6, how to fix it... as you simply do not. I do think that a promise that will be covered in another instructable might want to make an appearance at this point as opposed to the end. I could not help but feel disappointed when it was promised earlier and then did not make a presence here.

I hope this makes sense as I truly enjoyed the clarity of what you wrote here.
AnglinaSmith JGB2 months ago
go to this link for more detail
Biodynamic (author)  JGB2 months ago
Your comment makes perfect sense! I just needed to find the time to make another instructable and insert the links. Thanks for the push. The links have been updated.
JGB Biodynamic2 months ago
I would have hated for this detail to cause friction in others as you presented very well. I will make this build with my kids and then maybe some students... either way, its a win!
Kink Jarfold2 months ago
That was awesome!
sturific2 months ago
me and my friends had so much fun with these, when we were young. never put this much effort in to them though.
AussieAlf2 months ago
That's pretty cool biodynamic. Wish teachers taught subjects like yours back when i was a kid.
Biodynamic (author)  AussieAlf2 months ago
Thank you! One of the reasons I decided to teach middle school was the lack of excitement in my own experience.