By Douglas R. Pratt
Thousands of model rockets are built and flown every year by schools, summer camps, Scout groups, church groups, and organizations of every description. It’s a great way to do some hands-on teaching in a wide range of subjects, and the motivation is built in. Teaching with fun is teaching that works.
So you have a group of kids who would like to give model rockets a try, but you don’t know the first thing about it. This article is meant to give you that "first thing" without flooding you with information. Don’t worry about the details; after the first time, you’ll be an expert. Let’s get you through the first time, so you don’t feel like you’re learning to swim by being kicked off a bridge.
There are five things you need to build and fly a model rocket:
A rocket motor of the correct size for #1.
A safe place to fly.
A launch pad.
An electrical launch system to fire the rocket motor.
1. Rocket. There are a lot of rockets to choose from. We are fortunate to have companies in this business that make excellent products; I can personally recommend every one of them. You will not be disappointed with rocket kits from either of the two big manufacturers, Estes and Quest. There are also many outstanding small manufacturers with kits you will want to look at, including Apogee Components, Semroc, Fliskits, Edmonds Aerospace, Aerospace Specialty Products, and Pratt Hobbies.
Your choice of rocket kit should be guided by your group. If they are on the younger side (under 10), consider a kit with a plastic fin unit. These generally have fewer parts, are faster to assemble, and fly straight. The Quest Viper and Estes Alpha III are two popular rockets in this category. I particularly like the Quest Viper because it does not require plastic cement to attach the fin unit.
If you want more actual construction, you have a lot of good choices. To keep things simple, I recommend avoiding kits with plastic parts that need to be glued. White (casein) glue is safe and non-toxic, with none of the cleanup worries of solvent-based glues or “super glue” cyanoacrylates. You should also look for kits with all the parts pre-cut, so you don’t need anything more than a pair of scissors.
2. Motor. The kit you select will have a list of recommended rocket motors. Go with the smallest of these for your first flights. Model rocket motors have letter designations that describe their relative lifting ability. You will probably be dealing with “A,” “B” or “C” motors. I recommend “A” motors for your first flights.
Two companies make model rocket motors in the US: Estes and Quest. Their A-C motors are the same size (18mm diameter, 70mm long), and can be used in almost all the rocket kits you are considering. They are also available in economical bulk packs of 24-25 motors. All motor packs include the electrical igniter that you will insert into the motor nozzle and attach to your launch system to fire it.
3. Flying field. Most of the rockets we’re talking about can be flown safely on a typical school athletic field. You can set up on one end of the field or the other, depending on the wind direction; the rockets will drift with the wind after their parachutes or streamers come out.
Tall trees are not helpful. Never fly where a descending model might get tangled in overhead wires, and never try to recover a model that has done so.
Do not fly on one end of the field while there is a game in progress on the other end. Make sure that everyone around you is aware of what’s going on. Counting down in a loud voice before launching isn’t just for the thrill; it’s also a safety measure.
4. Launch Pad. The launch pad consists of a 1/8 inch diameter rod, a support to hold the rod straight up, and a blast deflector to keep the rocket’s exhaust from hitting the ground. Model rockets require guidance for the first few feet of their flight, until they have built up enough speed for the fins to keep them flying straight. The rod fits through the launch lug, a small tube that is glued to the side of the rocket. Sliding up the rod keeps the rocket pointed in the good direction.
Launch pads can be very simple. I have a “redneck launch pad” that consists of a piece of two-by-four with a hole drilled in it, a welding rod stuck in the hole, and a piece ceramic tile under the rocket. I wouldn’t want to use it all day, or if there is any wind, but it works.
Plastic tripod launch pads are more common. Both Quest and Estes make these, and they are a good value. You can purchase launch pads separately, but they are more common as part of a “starter kit” that includes a rocket, a couple of motors, a launch pad and a simple electrical launch system. These are readily available at stores like Wal-Mart, Toys R Us, Michael’s Crafts, and hobby shops.
For larger groups, having two launch pads will make things a lot easier. Many groups build or buy a launch rack, a stand based on a sawhorse that supports five or six launch rods.
5. Launch System. The electrical launch system is probably the main reason that we can claim to have launched over 45 million model rockets in the USA without a serious injury. We never, ever use fuses or matches to fire model rocket motors. The electrical system gives us complete control over the launch. It teaches us about physics and chemistry. And it’s a lot more fun to be able to push the button!
The “starter kits” described in item 4 above usually include a simple electrical launch system. These are powered by common alkaline batteries, and are generally good for 20-30 firings before the batteries need to be replaced.
Other launch systems use a 12 volt battery for power. You should look for a 12 volt launch system for bigger groups or all-day launching, since they are much more reliable. The best power source is a car battery, since it was freshly charged the last time the car was driven. The current required to heat a model rocket igniter is so small, a typical car battery will never notice it. Sealed lead-acid (gell cell) batteries and nickel-cadmium (ni-cd) or nickel-metal hydride (ni-mh) packs are also excellent power sources for launch systems.
The launch system must provide at least 20 feet of wire between the launch pad and the person pushing the button. There must be a positive safety interlock, to make certain that no power can get to the igniter while it is being connected. This interlock can be a key switch or a plug that is removed from the launch controller. Our “Go Box” system has the cable completely unplugged from the launch controller until you are ready to launch. This is good for single pad launches, but not very convenient for multiple pad setups.
The sources that I list at the end of this article will give you some designs for building your own launch system, if you want to give it a try. This can be a good way to save money, if you have the time and the tools.
When you plan your rocket session, you will make life easier if you do things in this order, or close to it.
a. Select a rocket kit.
b. Order enough. Get a couple of extras.
c. Order rocket motors.
d. Order or build launch pad and electrical launch system.
e. When the kits arrive, BUILD ONE BY YOURSELF. Avoid humiliation.
a. White glue (a big bottle shared in small paper cups with Q-tips for applying it works just fine).
b. Scissors and any other tools called for in the kit instructions.
c. Paper towels for cleanup.
d. Markers or highlighters for decorating.
3. Building session
a. Plan for an appropriate amount of time. If you have to go more than one class, have bags or small boxes for the students to keep their unfinished parts in.
b. Having extra adult helpers is a Good Thing.
c. Hand out the instructions first, and go through them before starting construction. Have your finished model handy to show.
4. Flying session
a. Plan your launch site with safety as your most important goal.
1. No power lines, tall trees or buildings nearby.
2. Plan for wind drift. Never fly if the wind is over 5 mph.
3. A central Launch Control area (a table is best) where you can direct activities.
4. At least 25 feet clearance all around the launch pad.
5. No one within 100 feet or so who is not paying attention or involved.
6. No running. The most dangerous part of this operation is the tip of the launch rod; tripping and falling on the pad can produce a puncture wound.
b. Prepare the rocket motors inside before you go on the field. See the rocket motor instructions for details on how to install the igniter. See the kit instructions to install the motor in the rocket.
c. Have an adult helper at the launch pad to assist in connecting the launch system to the igniter.
d. Place the launch system in Safe mode (remove the key, or whatever interlock the system provides) before allowing anyone near the pad.
e. Follow standard launch procedure:
1. Clear the pad area.
2. Look for spectators; if everyone is in position, announce “Range is clear.”
3. Look for aircraft. Announce “Sky is clear.”
4. Count down in a loud voice: “5, 4, 3, 2, 1, Ignition.”
5. Watch the rocket until it lands.
6. Return the launch system to Safe mode before allowing the next rocket on the pad.
f. Misfires: If the rocket doesn’t fire when you hit the button, return the system to Safe mode and wait at least 60 seconds before approaching the pad. Remove the rocket and proceed to the next flier.
g. Recovery: Do not permit spectators to run after a rocket; it’s a great way to trip over something and get hurt. Never attempt to climb a tree after a rocket. If a rocket lands on a building, ask a maintenance person to recover it for you. If it drifts off the field, make sure you ask permission before going on anyone’s property to recover a model. If models are drifting toward obstructions, move your launch pad to a better position.
These procedures have been worked out since 1959 by members of the National Association of Rocketry and folks involved with model rocket manufacturers. We know that rocketry can be done safely, because our sport has an outstanding safety record. Do it right, and you and your students will enjoy your rocket sessions for years.
National Association of Rocketry (www.nar.org). Highly recommended. They have many useful materials, lesson plans, and excellent student programs. Join.
Quest Aerospace (www.questaerospace.com ). Major manufacturer of kits, rocket motors, and launch systems. Good bulk-packs of kits and motors. Excellent resource materials. Excellent web site. Helpful folks.
Estes Industries (www.estesrockets.com ). Oldest, largest, best-established model rocket manufacturer. Outstanding resource materials for educators.
Apogee Components (www.apogeerockets.com ). Excellent books, software, and resources for educators.
Rocketry Online (www.rocketryonline.com). Excellent online resource, with plans for launch systems and many other things.
Federation of Galaxy Explorers (www.foge.org). New group organizing activities all over the country. Unique approach, integrating many disciplines into space science and exploration. This is the answer to, “Okay, we flew some rockets, what next?”
If I can help you, or if you have any comments or suggestions, I will be glad to hear from you at email@example.com.