Brief:
The Back-Up Box is a simple, low-cost launch controller anyone can build. I built it as part of a NARTREK Advanced project. It can fire any kind of igniter and is entirely self-contained, operating on 18V instead of the usual 12V. It is lightweight, compact, and is intended to be carried in your vehicle at all times as a backup to the "main" club 12V system in the event of failure, rundown batteries, or someone forgetting to bring the main system. It's sort of an Estes Electron Beam controller on steroids.

Construction:
Back-Up Box is no larger than a cigar box for a very good reason: it is a cigar box. The unit housing is a hinged wooden cigar box of the type that can be picked up used at a tobacco store for perhaps 50 cents or a buck, or unused and unfinished at craft stores like Michael's for $1.98. Power comes from two 9V batteries wired in series and will easily fire Copperheads, First-Fire Jr., or e-matches as well as Estes and Quest igniters. Because I built it with only 38' of launch wire for compactness, it's only rated for G impulse launches (H power requires 100' per the NAR safety code). For simplicity and safety, Back-Up Box uses a dual button firing mechanism consisting of two spring loaded buttons that must be held down simultaneously using two hands to effect a launch. This is a common industrial safety procedure. It is therefore self-enabling, self-arming, and self-safeing. Back-Up Box features a separate continuity check circuit powered by a single 1.5V AA battery, which can be used without toggling on main power. Although suitable for mid power, there is no removable launch key, thus it does not strictly meet the NAR code specification for a high power launcher. (Although technically, one could just unsnap one of the easily accessible 9V batteries and put it in your pocket while going out to the pad to fiddle with something). The bottom line: two separate things have to happen to complete the Back-Up Box firing circuit, so it is safety interlocked as the Model Rocketry Safety Code required. It is also childproof: kids won't figure this out unless you show them.

Back-Up Box is an ideal do-it-yourself launcher project for a beginner. It would make a great Boy Scouts or school project. Total cost is less than $12 and no fancy electronic components, resistors, relays, capacitors, transistors, or circuit boards are required, just some Radio Shack buttons and batteries hardwired together. Only a power drill and a cheap 15 watt soldering iron are needed to build Back-Up Box. I had never built anything electrical before in my life or used a soldering iron before. I just followed the instructions on the back of the Radio Shack packaging. I must admit that my wiring and soldering jobs were inelegant and probably nowhere near the workmanship and quality standards of say, Ted "Unabomber" Kaczinski. That said, Back-Up Box works absolutely great--it fires 6 different types of igniters the first time, every time. If I can do it, anybody can do it so we'll just call my 18V launch controller design "robust".

Here are the internal components, all purchased at Radio Shack:

• 22-gauge stereo hook-up wire, part #278-1215 (used for internal wiring)
• Scotch Super 33+ electrical tape
• 1 "AA" battery holder, part #270-401A
• 2 heavy-duty 9V battery snap connectors, part #270-324
• 3 SPST momentary pushbutton switch, part #275-644 (black)/646(red)
• 2 1 1/8" micro smooth test clips, copper plated, part #270-373
• 1 mini-lamp, 1.5V, 25 mA, part #272-1139
• 1 SPST micro-mini toggle switch, part #275-624
• 75ft 24-gauge speaker wire, two conductor clear, part #278-1509

The utter simplicity of Back-Up Box is evident from the attached circuit diagram. [Note: Everything is mounted on the interior lid of the 7"x7"x1 1/4" hinged wood cigar box.]

1. Drill three 1/2" holes in the box lid in a rectangular array for the pushbuttons (two widely separated for firing and one for continuity test), a 1/8" hole for the continuity test bulb, a 1/4" hole for the toggle switch. Drill 2 more 1/4" holes one inch apart in the side of the box for stress relieved launch wire anchor port.
2. Mount the buttons and switches in the proper holes per the package instructions.
3. Cut pieces of 22-gauge wire suitable for connecting everything together, twist them together to attach to the proper components, and solder everything except the launch wire, which is attached last.
4. Using 5 min epoxy, glue the 1.5V battery box in place. [Note: the two 9V battery connectors must be left hanging--not glued--or the batteries will be difficult to attach and remove at will.]
5. Using duct tape, secure loose or dangling wires to the box lid
6. Split the launch wire (clear speaker wire) for 6" at both ends. On one end, solder the 2 copper test alligator clips.
7. Feed the other split end through and back around the two holes in the side of the box (to act as a stress relief to protect the circuit in case somebody trips on the launch wire) and solder the ends in place per the circuit diagram.
8. I used pieces of electrical tape to cover all the solder joints.
9. Label as appropriate all the buttons and switches. I left the finished product unpainted.

Flight:
Before field testing Back-Up Box out at the launch site, I performed a static test in my back yard by taping a C6-7 to a heavy metal post, rigging it with an ignitor, and giving it a shot. I pressed down on the continuity check button and the dinky 25mA bulb lit up! Turned main power toggle on. I pressed down on left and right firing buttons. Nothing! I tried again. Nothing again!

Now what do I do? Then it occurred to me that the main power toggle switch might be wired in backwards and therefore was actually in the "off" position. (Don't they label these things? How is one to know?). I flicked the toggle the other way, pressed the twin firing buttons again and WHOOOOOOSH! The motor fired! I then relabeled the main power switch. Hey, this electronics stuff isn't so hard. My test program for the Back-Up Box consisted of the following, using different rockets:

• Estes D12-3, ignited by Quest Tiger-Tail
• Aerotech E30-7, ignited by AeroTech Copperhead
• Estes D12-5, ignited by Estes ignitor
• Aerotech F23-4 Econojet, ignited by Aerotech FirstFire Jr.
• Aerotech E30-4 ignited by AeroTech Copperhead
• Aerotech F50-6 ignited by Polecat Aerospace hand-dipped e-match
• Cesaroni G79SS ignited by Cesaroni e-match

In every case, the motor fired the first time with no failures. Continuity was checked every time with no inadvertent firings. Over a period of two launch days held two weeks apart, I invited others to try Back-Up Box using the original set of 9V batteries, again with no misfires. After 20+ launches, the system is still operating as new, so the battery capacity is 20+ launches per set of 9V batteries. I did try one more test: cluster firings with Back-Up Box. Using fresh batteries, two motor clusters consisting of Estes D12s and using a clip whip were repeatedly launched with no trouble. However, when I tried a 3 motor cluster, only 2 motors lit. Repeating the test gave the same result. Back-Up Box has the volts but not the amps so therefore cluster launches are limited to 2 motor Estes clusters. That seems to be its only limitation.

Summary:
Back-Up Box is pretty idiot proof respecting both construction and use in mid power rocketry. It is cheap, simple, safe, and perfect for first time junior electricians. It fully meets its design objective as a light, reliable, convenient launch controller to be carried in the car at all times as a backup. As far as I know, it is the only 18V launch system around. All the components could be easily stuffed in a much smaller container by somebody who knows what he's doing but I like the larger 7x7" cigar box as it has plenty of room inside for a spare set of 9V batteries and a small Radio Shack battery tester. Plus it still has room inside for a couple of nice, stinky Garcia-Vega Coronas to enjoy after the launch.

PROs: Small, inexpensive, and easy to build. Powerful enough to fire any single ignitor and safe for the continuity check of even low current e-matches. Simple, effective dual-button interlocked firing that is childproof and unlikely to be triggered by accident. A further layer of safety can be added by unclipping one of the 9V batteries when stepping away from the controller. Easy to troubleshoot circuit is easily accessible and as simple as it gets. Good for 20+ launches per battery set and you can buy fresh batteries for each launch for the cost of an Estes D12 motor.

CONs: Not useable for HPR, due to short (38') launch cable. Batteries are not rechargeable so I recommend fresh batteries for each event. Not to be used for clusters of more than 2 motors. Thin wooden case is not particularly strong (but is rustproof and non-conducting!). Dinky 25mA continuity light is hard to read in direct or bright sunlight. Back-Up Box may get the job done but it's a little funny looking, kind of like Steve Buscemi in "Fargo".