TLL – a 'Trivial Launch Light'

by Roger L. Deran, LUNAR #534

I just love those night launches, and maybe by writing an article about a simple night launch light, I can encourage another one soon. How about having a night contest? How about trying something like C-altitude/night?

The basic problem I found when trying to lash together the simplest possible light was the mounting system. Having the light just rattling around in the payload section just won't cut it. The reversal of acceleration at burnout or, of course, the shock of ejection would throw the light around and could take off the nose cone or do other damage. The solution I found was to cut a short piece of 3/8" dowel to use as a "chassis". The length is such that it fits exactly in the payload section.

The batteries are just taped onto this chassis. I used two AA cells, but AAA would probably work even better, being lighter. I just wanted plenty of current to keep the light bright. A simple flashlight bulb is then taped onto the dowel above the batteries. Black electricians tape is good, duct tape probably would work. I would worry about the strength of masking or clear tape.

The whole circuit is then soldered together with a fine wire. I used Kynar, which is a very high quality, very tough, single-strand wire used in the electronics industry for prototyping digital circuits by wrapping on posts using special tools. You can get some free from your local wire-wrap fiend. Any good electronics shop has it too. Use a good soldering Iron to get the ends of the batteries hot quickly and to avoid "cooking" the entire battery. I use lead-free solder.

The reason for the fine wire is simply that it makes the easiest switch you can possibly build: none at all! Just run two of the wires together out of the top of the payload section and place the nose cone on. They will hang out where you can twist their stripped ends together to turn on the light.

If the wires are fine, there will be negligible wind resistance, and we are not trying for altitude anyway. You might be concerned that the added drag will cause the rocket to veer to one side, however. To reduce the possibility of that, you can tape them onto the side of the payload section after twisting them together. Also, put them on the opposite side of the launch lug. Don't forget a launch lug represents a significant drag, but never seems to deflect the ship.

My payload section is clear plastic, since it is a Nova, and I recommend the use of a clear section because the light radiates in all directions, unlike lights that are mounted on the side and unlike holes in the body tube. You can put in a clear, colored plastic liner, too. If you use a variety of different colors, each visible from a different direction, the color of the light will appear to vary as the rocket rotates on the way down. Check office/art stores for clear colored plastic.

My first and only flight with this contraption was on a B6-4. There was only slight wind, from the usual direction, so the risk of extreme weathercocking was low, even though the bird was loaded down and the CG was well forward of the CP. (I believe a large CG to CP distance increases both the stability and the tendency to weathercock. This would be an interesting thing to experiment with. Does anyone know whether this is true?) The flight was a gentle curve to the right of the crowd to about 300' so that on recovery, the rocket drifted slowly to the left and landed on the left end of the field. The light was one of the brightest I saw and would have been easy to see up to 1000' or more.

I hope you have fun with this TLL ('Trivial Launch Light'). See you at the next night launch.

Information date: September 18, 1998 lk