Rockets and Rocket Experiments
Including Videos

WARNING AND DISCLAIMER:  If you are underage, then consult with your parents or guardians before attempting any of this.  You are on your own - I'm not responsible for your actions or harm you may bring to others because of your actions.  Making the items described below  can result in injury or death to you or people in your vicinity. Some things mentioned here may be illegal to make in your city, county, state, or country so check the laws that apply to you before you attempt anything described here. These notes are not complete on purpose. If you are reading them and new to pyrotechnics, then you are making a mistake. Stop now - this page is not for you. Get a beginning book on fireworks (see Skylighter or American Fireworks News (very quick shipping)  for a start) and read up. You can't make any of this work without more information so read up or join a club or ask someone to help you.

Rockets
(General)

Cases

Rocket cases are generally made from convolute tubing rather than spiral wound tubes. Toilet paper tubes are spiral wound - most of the rocket cases in the pictures below are convolute except the 1/4" tubes - notice that the wrapping seam on the convolute tubes is not spiral but just a straight seam that runs down the tube. A 1/2" case should have about a 1/8" sidewall to insure it can hold the pressures from the burning composition. Usually, a 1/16" wall tube is for salutes - not rocket motors. You can wrap your own small cases easily - use gummed paper tape and a waxed stick of the proper size. Keep it 1/2" or less for your first few tries - go easy on the water on the tape - pull case off stick quickly. You may have to figure a way to hold the outside flap on the case until everything dries.

Nozzle Size

A good starting nozzle diameter for a rocket is usually 1/3 the I.D. of the case. However, the nozzle can be opened up to 3/8 of tube I.D. which allows very hot fuel, gets fair altitude, and is much more reliable (less likely to CATO).

Nozzle Composition

Clay can be straight kitty litter or dry pottery clay. Do not wet the clay. It will compact hard as a rock. Having said that, some people like to add 10% or so WD-40 or thinned toilet wax (thin it with Coleman fuel) to make the clay compact easier. Others like to add grog (ceramic dust) with the oil/wax thinking that it grabs the sides of the cardboard better. I don't like to add grog because, if I have to ream the clay out or make a passfire, the grog is a spark producer. For medium performance rockets, you can get by with straight clay.

Bulkhead

 

Here is how the pass-through hole is made. A wire is placed on top of the delay, clay is poured around it,
the whole thing is tamped with a hollow drift (same one that is used to tamp the fuel). Notice the clay pulled away around the wire. That is because it wasn't pressed in hard enough. Below is another picture of a couple of 5/8" motors that had the bulkhead pressed on. Nice and clean, eh?

 

Stabilizing Sticks

Make them thin but not weak. The length should be about 6 times the length of the motor (minimum). Use pine and rip them out on a table saw or use cat-tail reeds or bamboo garden stakes or 1/8" round dowel or food skewers (for 1/4" motors) or ....???

Delay Charges

The most common delay composition is just more of the fuel packed above the end of the core.

Any of the various charcoal star compositions work well as a delay charge. Try Chrysanthemum #6 (see the compositions section).

Cheap Tooling

Rocket tools can be expensive or cheap. The cheapest tools are just pieces of hard wood doweling.   To make an inexpensive set of 1/2" tooling:

Buy the following from a hardware store:

1 length of 1/2" dowel
1 piece of 3/16" brass rod
If you don't have an old piece of wood, then buy a short 2x4 while you are at it.

Drill a 3/16" hole about 1" deep in a 4" or 5" piece of wood.

Cut a piece of the 3/16" brass rod to about 3" to 3 1/2"

Smooth the ends of the rod with a file or sandpaper - you can also taper it a bit if you wish by putting it in an electric drill and running it across some sandpaper. But you might not have to do so and it might be worth trying it 'as is' since getting the taper right and then getting it smooth afterwards is a pain.

Cut a 6" piece of dowel and drill a 1/16" hole in it. Be sure the dowel fits easily over the brass rod (it is ok to ream it out to 1/64" over if necessary).

Put the brass rod in the hole in the wood and put a cardboard tube over it.

Proceed to fill the tube with clay/propellant/delay/bulkhead. Put in no more than 1 diameter of material, then tamp with the hollow dowel. Use 10 firm smacks with a dead blow hammer or wooden mallet. Don't hit it hard but DO make the increments small (very important!).

For smaller rockets (1/4" to 1/2") I use a dead blow hammer or arbor press depending on the composition - only ram BP! If your BP is granular (pulverone or similar) then you need to compact it harder to consolidate the granules into one long grain (see the fuel section below). Generally, powdered BP (meal powder) compacts easiest - especially if you use small increments. 

For BP on 3/4" and higher I use a 4 to 6 pound hard split hammer or the press. I was using a dead blow for the bigger tubes and was getting an occasional CATO. Dan Thames lent me his 'Barney Rubble' hammer at PGI and that eliminated the CATOs. (see: http://www1.mscdirect.com/CGI/NNSRIT?PMAKA=97133417&PMCTLG=00 ). It works much better for larger motors - you can actually feel the composition compact and you know when it is properly smooshed. I use the hard tips (http://www1.mscdirect.com/CGI/NNSRIT?PMAKA=63282263) which give the best feel. It is a bit big for motors less than 3/4"- use a one or two pound dead blow hammer for those.

When the core is covered with powder, then finish tamping in one more increment (one more diameter) of powder, a delay (which is usually more of the same powder), and the kitty litter bulkhead. Use a piece of dowel that doesn't have a hole in it. If you need a passfire (a hole in the bulkhead to allow fire to get to your header) then you can consider adding it in but get the basic rocket motor working first.

When done, remove the brass core with a pair of pliers - gently work it back and forth. If you crack the grain at this stage, it will CATO (explode) when you try to launch it so be gentle.

Fuse the rocket with Visco or similar.  It is easiest to just tape the fuse in the hole with masking tape - although a more elegant approach is to use tissue paper and wedge the fuse in the hole.

An Easter Egg Payload (works great!) The stick is a bamboo garden stick

Tape the motor to a stick that is about six times the motor length.  After the basic length is met, don't worry too much about balance, it will probably fly if the motor is good.

 

Above are some machined rocket tools made from scrap material in a shop. You can also just make the tooling from wooden doweling. The longer core on the left will require a much cooler fuel (RP or similar). The one on the right can take a hotter fuel

 

Above is a general guide for creating BP rocket tooling from aluminum stock. You can vary these measurements slightly depending on your particular need. If you are just starting to make your tooling, try to get it close to these measurements and vary your fuel to get the performance you desire. This tooling works fine for nozzleless designs, too.

A. Spindle that is 6 1/2 diameters long (approximately). The diameter at the throat (where the 30 degree taper starts) should be more than 1/3 the width of the tube. Commercial tooling is usually just a bit under 1/2 the width and the nozzle then tapers inward so that the clay bulkhead ends up choking the nozzle just a bit smaller before the fuel grain starts. The length of the spindle should be about 2/3rds the length of the tube (commercial spindles are sometimes up to 3/4 the length but they don't leave enough room for delay/garnish or headers).
B. Base. Keep it small enough that you can put it in a vice
C. First ram - note the taper on the end. The center hole does not have to go completely through (and probably shouldn't). Ram is usually marked to indicate if it is too close to the bottom of the tube (thus ruining the spindle). The length is the length of the tube plus 2".
D. Second ram. Ram is usually marked to prevent jamming on spindle. It is 2/3 length of the first ram.
E. Third ram - solid - also marked. It is 1/2 length of the first ram.
F. Cheater bar to free stuck rams. When pressing the material will sometimes ooze around the ram and stick it. The cheater bar helps to free the ram. The usual solution to sticking rams is to use smaller increments of composition.

 

More Expensive Tooling

Commercial 3/4" (one pound) Whistle Rocket Tooling
Whistle rockets use a shorter and wider spindle.

You can get custom tooling from several sources on the web. Look up Wolter Pyro Tools, Skylighter, FireFox, Cannonfuse, Pyrocreations, and more for some quotes.  You can also make your own if you have a small lathe or mill. Custom tooling is very nice but usually not necessary at first.

Fuel

Fuel should be hot enough so the rocket doesn't 'chuff' and cool enough so it doesn't blow up. Lots of factors affect this so start with a cooler mix and work up to something that provides good performance and doesn't blow up (CATO). See RP and RPH in the composition section for example fuels. Here is a rocket that still worked but 'chuffed' listen to the sound when it launches: fiveEighthsShell1a.wmv The solution was to put hotter fuel in it.

Note that fuel issues can drive you a bit buggy. Super-hot paulownia based BP that is ideal for a nozzleless design (see nozzleless) will cause CATOs after it has been on the shelf for a few months. The best that can be figured is that the fuel dries up completely and the grains become hard enough that light packing isn't sufficient to consolidate the grains - thus causing cracks and CATOs.  The same fuel when re-milled and packed in as dust works fine. So, if you start running into strange CATO situations think about either ramming really hard or milling your BP to dust and tamping it that way.