Rocket #7 - Double TroubleDual Deployment Construction Details

Double Trouble is based on the "Modular Rocket System". The electronics module for Double Trouble contains an altimeter and battery, and runs the apogee charge out thru two brass foil sheets (not shown) on the aft end of the coupling tube. On the fore end there is an ejection charge for deploying the main chute at the switch selectable altitude of 700 ft.

1. Innards (Altimeter and Battery)

Above are the innards of the electronics module layed out for inspection. You can see, from left to right, the aft bulkhead, the foam battery holder and batter, the altimeter/switch assembly, and the already assembled tube in which they go. The fore bulkhead and outer ring (1./5" section of body tube) are already glued on in this picture.

I created this cool foam insert to hold the battery from two pieces of this 1" pink foam I had laying around.

The altimeter is attached to the board with four small screws. The board itself is connected to the two threaded rods via some 1/4" tubing that I glued to the board. The power/arm switch is a 4 pin dip switch and cable that is glued to the board. The board is further secured by the use of a 1/8" "keyed" slot in the aft bulkhead (see picture, top of page).

2. Ejection Charge Socket

The ejection charge socket is made pretty much the same as that on the MRS, except that the wires are run thru a hole on the fore bulkhead into the electronics module. They are attached to the altimeter after the board is inserted into the module.

In the picture on the above left, the apogee charges come out of the module as two stripped wires. I later determined that these would not make good enough contact, and so switched to the "brass-foil" approach, described (but not shown) here. You might want to see the GPARS Construction page for more pictures.

3. Shock Cord and Rigging

One of the threaded rods on the forward bulkhead also has a steel bracket to which the main shock cord will attach. The shock cord slides thru the upper body tube baffle (rather than being connected to the baffle as in the lower body tubes), so that the force is distributed more easily than it would be with screws that connected the forward body tube to the electronics module.

Below you can see the entire rigging of Double Trouble. At apogee the altimeter fires a charge that goes down the body tube to the fin can and ejects the drogue (red) parachute and electronics module (and all things forward of it). As the rocket passes thru 700 ft, the charge on the top bulkhead of the electronics module fires thru the upper body tube (which is attached to the electronics module with screws), pushing the main (green) parachute and nose cone out of the top of the rocket. The whole thing lands gracefully and gently :-)