Looking for a new hobby? Nothing can be more rewarding than sending a
rocket screaming into the air, watching it explode into a firey coulage of colored flame, and then fleeing the area before the
local authorities arrive.
Based on my experience with building homemade rockets, here is a short and simple guide with some do's and don'ts to rocket building. Please note this is a poor-mans guide to rocket building, hence I'll explain how to use simple, easily obtainable items. Generally anyone of any age can buy all of the items you'll need. I won't get into how to add color with
Magnesium dust, or any other unobtainable substances.
Disclaimer: I'm in no way responsible for any injury you may obtain while trying to do this, or any trouble you get into with the law. Working with some of the substances I have included is extremely dangerous and should be done so with great care. Build at your own risk
Step 1: Preparing your Explosives
When designing a rocket with an
explosive payload, consider the overall weight of your explosives first, this will help with engine sizing and actual rocket selection. There are essentially two or more parts to your explosive payload:
Primary charge, and your
visual effects.
Primary charge: If you have access to
black powder or
gun powder, this is ideal. 75-100mg is usually a good amount. A pound of black powder can be bought at
Wal-Mart for about $25. This is by far the easiest and cheapest way to go, but depending on state laws you may not be able to get it. The alternative is to buy
Estes rocket engines, which are a solid cylinder of black powder, and grind them up. One package of three D engines will do it. The engines come in a cardboard wrapping that must be removed. To do so cut the wrapping long ways a few times to get a couple of layers deep, and peel off. Once you get down to the core, you'll have a black cylinder with a little bit of glue and cardboard stuck to the outside, and a clay nozzle on the end. The nozzle breaks off easily, and the rest of the wrapping should be scraped off. Place your engine in a pan or box, and strike it repeatedly with a hammer. It is a good idea to place a peice of cloth or plastic in between so everything stays in the pan. Grinding it into a powder takes time, but the finer you can get it, the more power it will explode with.
Visual Effects: My visual effect of choice is the
match head. Buy a couple boxes of 250-count
Strike on Box wooden matches. Cutting the heads off several at a time with any pair of basic
cutters (scissors don't work too well). I've measured one 250ct. box to yield approx. 33 cubic-cm of match heads. You can stop here, but I highly recommend picking up some
firecrackers if you have the means. They add a lot to the noise and color effects.
Step 2: Selecting your rocket/engine
First weigh your explosives.
Next, based on the volume of your explosives select an appropriate sized Estes model rocket.
Finally you can use this
equation to determine which engine to buy based on how high you want you want it to go.
Height(meters) =
( (T/2m - 4.9)u²
) +
( -4.9v² + (T/m - 9.8)uv
)
u = engine
thrust duration in seconds
v =
parachute delay duration in seconds
m =
net mass of the rocket in
kilograms
T = Avg. thrust of engine in
newtons (not the
impluse, the average thust, ex: 120ns impulse for 1.5s = 80n avg. thrust)
Here are T and u for Estes and
Aerotech engines. Use Estes for smaller rockets, and the more powerful Aerotech engines for bigger projects. v, the parachute delay, or in our case the detonation delay, will be listed on the box. Either go for the shortest time, or plug different times into the equation. Be careful however, using too long of a detonation delay with a heavy rocket can cause the rocket to hit the ground (getting a negative value for height from the equation) before exploding. This happened to us once and we almost blew up somebody's house (see
The Infamous Rocket Mishap of 2002).
Estes engines:
C Series 5.88N 1.70s
D Series 11.76N 1.70s
E Series 12.03N 2.60s
Aerotech engines:
D21 21N 1.05s
E15 15N 2.67s
E30 30N 1.33s
F25 25N 3.20s
F50 50N 1.60s
G40 40N 3.00s
G80 80N 1.50s
Step 3: Construction
Estes rockets are easy enough to build, just follow the directions. Construct the entire rocket, including engine, except for the parachute. The engine's parachute charge will act as your detonator. Place your primary charge right above the engine. Doing this will assure your entire payload is ignited. Fill the rest of the rocket with your visual effects, or until the desired weight is achieved. Dont go out and buy all the expensive
launch pads and detonators. Just go to your local hobby shop and buy some
piano wire (not wire used in pianos, steel rods of varying diameters) for your launch rod, and hook up a
9v battery to some
speaker wire for your
detonator.
Soldering small
alligator clips to your speaker wire will help you to attach it to your ignitor leads.
Step 4: Adrenalin
Of course find a nice remote spot for launch, but not so remote that you have to hike back to your car. If you do this in a
suburban township like we do you'll need to be able to get out of there quick. Also night launches are prefered, not only do they provide the cover of darkness, but obviously the greater contrast for your
fireball.