GREEN AND RED-TAILED ROCKETS

Thanks to Dave Stoddard for supplying this little article. These magnalium (magnesium-aluminum alloy) rockets are really quick to make using a rocket press, and uncomplicated, yet very different than your average black powder rocket. Enjoy.

I have developed a couple of magnalium-based compositions over the past year that work well for rockets in the one pound to four-pound range. The benefit of magnalium-based compositions is that they can be mixed, pressed, and flown in a matter of minutes. There is no potassium dichromate to mess with, and no drying time or extended prep time required for the composition. This makes these rockets ideal for people to be able to build and fly on the same day.

First, some background -- Doc Steinberg and Doc Barr originally came up with a magnesium red rocket that was published in the PGI bulletin in the late 1990's. The problem with the magnesium rockets was that it took too much time to prepare the composition, and the use of potassium dichromate in the mix made it nasty to work with. I developed a magnalium formula based on the original magnesium formula, and Doc Steinberg worked with me to tune the choke, pressing forces, and other elements to get the rockets to perform well. If you build these correctly, a four pound rocket will fly at least 1500 feet high, or more.

Doc Steinberg and I published the first formula, for red magnalium chuffer rockets, in the December 2004 PGI journal. I have since gone on to develop formulas for green and yellow as well. I flew four-pound versions of the red, green, and yellow compositions at the recent FPAG 4F event in November. Note that all of these compositions are pressed on standard black powder rocket tooling using a choke (nozzle) that is as tall as the inside diameter of the tube is wide (on a tube that is 1-1/4 inch inside diameter, the choke would be 1-1/4" tall). The height of the choke is important as it makes the size of the exit smaller due to the taper of the spindle. The formula for red magnalium chuffer rockets is as follows:

Red Magnalium Chuffer Sky Rocket
Strontium Nitrate	55%
Magnalium, -325 mesh powder	28%
PVC powder	10%
Parlon	7%
Vaseline (dissolved in Naphtha)	+2%

I grind the strontium nitrate in a coffee grinder to get it as fine as possible. DO NOT grind mixed ingredients! I have since discovered that the VM&P Naphtha is responsible for the chuffing effect, and allowing the naphtha to evaporate completely from the mix results in no chuff whatsoever. With good strong paper tubes, like the parallel tubes sold at Skylighter, you could probably omit the Vaseline all together. Do not use Vaseline if you are making this composition for one pound (3/4 inch ID) rockets or smaller.

If you look at the oxygen percentage in the strontium nitrate (by molecular weight), you find that Sr(NO3)2 is 45.36 percent oxygen. I suspected we could make a green version of this formula by substituting barium nitrate for strontium nitrate. Barium nitrate is 36.73 percent oxygen, so you need to increase the percentage of barium nitrate to get the same quantity of molecular oxygen as in the red formula. We had the first successful flight of this formula at a Crackerjacks shoot. Here is the formula for the green magnalium rockets:

Green Magnalium Sky Rocket
Barium Nitrate	60%
Magnalium, -325 mesh powder	25%
PVC powder	9%
Parlon	6%

The barium nitrate is ground fine in a Wal-Mart coffee grinder before use. Note that there is no Vaseline in this formula. We omitted it, as barium nitrate is not as vigorous an oxidizer as strontium nitrate.

These four pound rockets fly perfectly. You could probably add 5% VM&P Naphtha if you wanted to get them to chuff (a nice effect), although I have not tried this for the green rockets yet.

Finally, if you look at the color spectrum, you will find that yellow is between red and green, based on angstrom wavelength of the emitted light. I estimated that a mixture of 60% green formula and 40% red formula would create a nice yellow magnalium rocket. I flew these at the FPAG 4F shoot in November 2005 with excellent success. In one particular flight, we estimated that one of the yellow rockets went over 2500 feet by counting the time between rocket heading broke and the time we actually heard the report (about 2.5 seconds). If you were to mix a yellow composition without mixing the individual red and green compositions, the formula would look like this:

Yellow Magnalium Sky Rocket
Strontium Nitrate	22%
Barium Nitrate	36%
Magnalium, -325 mesh powder	26.2%
PVC powder	9.4%
Parlon	6.4%

With my rocket press, I have been using 2600 pounds of force to press these rockets. If you have a copy of the PGI article John and I published in December 2004, I provide a calculation for converting pressure to force based on the size of the ram in your press. You can use more force, but the additional compaction slows the burn rate somewhat. All of the chemicals and paper tubes that were used to make these rockets were purchased from Skylighter.

For four-pound rockets, we used sticks that were 1/2" square and 7 feet long. The rocket tooling we used was standard black powder rocket tooling (from Skylighter, Wolter or Harrison).

The choke (nozzle) is made from bentonite clay. I add 30% grog and 5% additional paraffin (Gulf Wax) dissolved in VM&P Naphtha. The percentages are very loose here. Some people use more fire clay; some do not use any. Mix the bentonite and fire clay together. Then melt the paraffin wax in the naphtha and mix the melted wax into the clay. Spread the clay out on newspaper and let the naphtha evaporate from the mix. It only takes 30 minutes for the naphtha to evaporate in 70 degree, sunny weather.

A few safety notes: Don't hammer these comps. They are equivalent to a form of flash powder. Wear cotton clothing and appropriate safety gear when mixing and pressing these. Don't make these rockets if you do not have a legal place to make them. It isn't worth the risk.

Dave Stoddard


NEW! Misch Metal. 1/2-inch diameter x 4 inches long, gray rod. Also called Swedish steel, magnesium and steel, or metal match. Misch metal is an alloy of cerium and several rare-earth metals. It is used to make sparks in movie special effects and for other applications. Scrape it with a knife, or a hacksaw blade or scissors and watch the sparks fly. Look for it on the Special Effects page.

Use Misch Metal as an Emergency Fire Starter. Can be used as an emergency fire starter for survival. One easy way is to use it with 100% cotton balls saturated with petroleum jelly. They catch fire easily. You can use them to make the base of a small, hot fire. Just add dry, fluffy tinder (such as grass), and then add small kindling to it. Make up some cotton balls ahead of time with the petroleum jelly and stash them in zip lok bags. You can really make your starter fire hot by adding magnesium chips or turnings (#CH1004) or embedding them in your saturated cotton balls.
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