Water Rocket Mortar




Hi guys today I will be showing you a fairly simple but awesome water rocket mortar I made!!!!

Materials you will need:

-500ml drinks bottle(with standard bottle cap)

-Car tire air valve (or bike inner-tube valve)

-empty pringles tube(or somthing the same diameter as the pringles tube along with an end ). !|!other savoury snaks are avaliable!|! xD

-a small self threading (not self tapping) screw about 2.5cm long but no shorter than 1.5cm

-a crisp packet wrapper or chocolate bar wrapper(as long as its the same material as the crisp packet)

-a rubber o-ring about 25mm - 28mm wide

-water! if you class that as a material (=

Tools you will need:

-a screwdriver

-a drill


-a pump or some sort of air supply that will fit the air valve

-a 20mm drill bit

-a 10mm - 11mm drill bit (depends on the air valve)

-a hot glue gun or an air tight sealant(reccomended)

Enjoy!!! :D

Step 1: Step 1:The Rockets Valve

1) Take your bottle and drill a hole on the bottom, get it as centrall as you can the hole will depend on the size of your valve but generally it should be about 10mm wide as you want to get a nice snug fit with your valve AND REMEMBER you can make the hole bigger but not smaller, so start with a slightly smaller hole and go from there.

2) Take your valve and put it on the inside of the bottle and pull through the hole... it should look like the one shown in the pictures

3) (optional) You can put sealant or hot glue around the bike valve to form a "super reliable air tight seal"

Step 2: Step 2:The Rockets Cap


1) Take you drill with the 20mm drill bit and center it ontop of the bottle cap (it is crutial that it is centered).

2) Drill the hole in the top of the bottle cap so it looks like a ring with a bit of an edge(see white bottle cap picture(yes it is a broken one... but you get what im trying to say)

3) (This step is not crucial but it helps) Take your rubber o-ring and place inside the bottle cap ensuring a snug fit, if you do not have an o-ring big enough simply find the largest one you have and cut it so it can go in the bottle cap. (see yelow bottle cap picture) Alternitavely you could use a rubber band!

Step 3: Step 3:The Mortar Tube

This is the easy part of the build!

1) Grab your pringles tube and find the very center on the bottom, mark it.

2) Take your screw and screw it throug the bottom of the pringles tube GET IT AS STRAIGHT AS POSSIBLE(pointy end pointing inside the pringles tube)


1) Ok so you need to grab your crisp packet and cut out 40mm by 40mm squares.

2) Fill you bottle about half way with water, different quantities get different results experiment with different quantities and let me know how it worked out for you!

3) Place the crisp packet wrapper square on the bottle lid (not the cap! the cap should be off!)

4) Put the lid on the bottle so it creates a nice seal

5) Attach your pump to the valve and keep pumping, (make sure to keep track of the amount of pumps) after a few pumps the crisp wrapper will give way and burst( don't get in the way xD ) once you've done this you will know the rockets limit!

6) Simply repeat steps 2,3 and 4 and pump the bottle up just under its limit (make sure to put the plastic dust cap on the valve)

7) Aim your mortar tube and drop your rocket in lid first and watch it go! :D

USE COMMON SENSE Don't aim it at living things or possessions that could be important AKA Don't be STUPID

Disclaimer xD : I do not except any responsibility for any bad things that may happen as a result of of this mortar.

Step 5: Alternatives

Instead of a 500ml bottle you could use a 2ltr bottle and a large pipe with an end cap!

All so try making parachutes and fins.. its up to you!

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    4 Discussions


    Thanks for the info! I was thinking of making a water rocket Launcher that uses a trigger mechanism to puncture the seal,

    like a spring loaded hammer with a screw poking out so when it makes contact with the wrapper, it will burst.

    Also it could be held over your shoulder like an RPG.

    Thanks again,


    Wow! Nice concept! I'll definitely want to build this! Great job!!

    Also I was wondering if I could use plastic wrap or aluminum foil instead? Thanks

    1 reply


    I'm afraid aluminium or plastic wrap will not work as during testing of different mediums for the "burst disk" I tried using both mediums in varying thicknesses and the combination of the two... Crisp packet wrappers of most chocolate bar wrappers seem to be the only thing that has the ability to withstand the pressure and rupture violently when even slightly lacerated.

    I hope this helps!

    If you have any further questions or ever need any help I would be more than happy to assist you (:

    -Aiden :D