This project uses vacuum to try and launch a model of the Saturn V rocket into space !
It is is quite impressive to watch the forces involved, and guaranteed to impress anyone regardless of age. Firing one of these vacuum rockets, is an excellent way of understanding just how much one atmosphere of pressure actually is, and how much the air from ground to space weighs.
It is a great project for getting kids interested in science, including a bit of space exploration history.
Here is a slow motion launch of the Saturn V:
How does it work?: The rocket launcher consists of a long acrylic tube, with a thin layer of packing tape at both ends. To begin with the pressure inside and outside the tube is the same. When you then turn on the vacuum pump, you remove the air inside the tube, whereby the pressure inside the tube approaches zero, and remains one atmosphere outside. If you image doing this under water, then all the water above the tube, would try to enter the tube, with a pressure equal to all the water above the tube. The deeper under water you are, the more water above it, and the higher the pressure. On land the same thing happens, only air weighs much less than water, but the air above the tube stretches up all the way to the border of space ! You then rupture the tape at the bottom of the acrylic tube, whereby the the air is very rapidly pressed into the tube, pushing the Saturn V rocket upwards. Because there is no air above the rocket i the tube, there is little resistance, and it can be accelerated unobstructed to a very very high speed.
The project is partly based on 3D printed partes, and the final step explains how to get help printing the parts if you do not have a 3D printer, and which files to adapt to non-metric materials. If you do not own a 3D printer or a vacuum pump, this project is all the excuse you need :)
Step 1: Bill of Materials
- Piece of wood 50x50x1000mm (1)
- Heavy garden tile for base
- Acrylic tube 100cm. Inner diameter 40mm. Outer diameter 50mm. (2)
- Printed parts (See file names in images)
- Mold making silicone (3)
- Vacuum pump (4)
- Vacuum tube. Inner diameter 6mm
- Packing tape, or another self adhesive foil min. 50mm wide
- Epoxy glue, or another strong glue
- A few grains of rice
- Screws, nails and paint
- Eye and ear protection, it is loud !
- Optional: Vacuum manometer and 6mm T-piece
(1) It can be anywhere between 45-52mm.
(2) If you can not get an acrylic tube in these metric measurements, the 3D parts can be changed +-20% to accommodate some variation. See the last step on 3D printing.
(4) You can get one- and two-stage vacuum pumps on eBay. One-stage is the cheapest, and sufficient for this project.
Parts needed for the Gantry:
- 1x GantryA
- 10x GantryB
- 1x GantryC
- 4x SupportArm
- 1x Crane
- 1x Hatch
- 1x Trigger
Step 2: Gantry Base
The base of the Gantry is a heavy garden tile. You want to make sure that the rocket launcher does not tip over. Place it towards one side, to allow room for the acrylic tube.
Place one of the Gantry elements on the garden tile, and mark with chalk where the wooden beam is going to be.
Step 3: Gantry Fixation
Drill four holes all the way through the tile.
Step 4: Gantry Fixation
Insert four long screws so that they just peaks through. Press the wooden beam onto the screws to mark where the screws are going to enter. Drill holes where the marks are, to prevent the wooden beam from splitting. Screw the beam securely in place.
Step 5: Gantry Paint
Paint red :)
Glue GantryA and a GantryB together, and screw onto base. Add the remaining nine parts, and GantryC on top.
Step 7: Support Arms
Mount the four SupportArms, and the Crane at the very top.
Unscrew the Crane again, and glue it onto the acrylic tube using epoxy or another strong glue.
Insert some loose zip ties into the support arms. Add glue and tighten the zip ties. Screw in the Crane again
Step 10: Trigger
Press the trigger into the socket. If you insert the socket into some hot water first, it becomes a bit more flexible, and less likely to break.
Insert and glue a small nail into the end. You can cut the head of a nail if you haven't got one without head. The nail is used for rupturing the packing tape at the bottom of the rocket launcher.
Step 11: Trigger
Mount the trigger on the base, so that the nail hits the opening of the acrylic tube in the middle.
Step 12: Vacuum Pump
Attach the vacuum tube to the Crane and the vacuum pump. The vacuum tube fits inside the Gantry.
Step 13: Hatch Silicone Seal
The rocket launcher has a removable hatch at the bottom with a silicone seal. If you do not want to play around with silicone, you can just glue on the hatch like you did the Crane, but it makes loading the rocket and applying packing tape much more difficult.
I have recently discovered a two component moldable silicone called Copy Flex, and it is now one of my favourite materials for DIY projects. Super easy to work with, and it creates a great flexible, durable and food safe part.
Mix them 1:1 and pour into the channel inside the hatch.
Scrape off any extra silicone to get an even surface. Just dump it into the middle, it is easy to remove afterwards.
Step 14: Hatch Silicone Seal
When cured, remove any overflowing silicone. This is easily done with your fingers.
Remove the inside guard, which was only there to keep the liquid silicone in place.
Use a knife to remove the last bits.
Step 15: Paint
Paint the rocket black in the recessed parts.
Step 16: Launching the Rocket
Put packing tape on the hatch, and press it on the bottom of the acrylic tube. Add a few grains of rice on the tape, to prevent the rocket from sticking to the tape.
Prepare the rocket by gluing on the three spacers. (I found that the spacers are actually not necessary)
Place the rocket on the support plate, and drop it into the acrylic tube. (the plate prevents air from rushing past the rocket)
Put packing tape on the top of the acrylic tube, the Crane.
Put on eye and ear protection !
Turn on the vacuum pump, and wait until the pressure does not drop anymore. If you do not have a manometer, this takes about 4 seconds.
Pull the string on the trigger.
Go look for your rocket in the neighbourhood :)
Step 17: 3D Printing and Files
When you print 3D files yourself, or get them printed somewhere, there are some parameters that are important, and some that are not. Only a few of the parts have some important parameters, so these are mentioned below, the rest does not matter:
Hatch and Crane: Print 100% to make them air tight.
Support arms: At least 4 outside layers to make them sturdy.
The .stl files are the ones you should print, or give to a print shop.
The .scad files are the ones you need to change, in order to accommodate non metric sizes, or other sizes of acrylic tubes. If you need to change them, I will gladly help, and upload a set a files for another tube size. Just let me know, I would be glad to see another Saturn V rocket launcher :)