The Flying Christmas Tree

As most readers know by now (I hope!), we want to eject two free-falling units (FFUs) from the rocket. Most of the really complicated stuff is on the one we call Rx: It has IR sensors, a tracking camera and all the mechanisms needed to point the sensors towards the other FFU, the Tx. A description of the Rx would certainly fill several blog posts. But in this one I want to talk about the Tx, particularly its mechanical design.

The mission for the Tx is fairly simple: shine as bright as possible! We need two kinds of light sources: the IR sources for the spectroscopy measurements, and visible red light (LED) for the tracking. To pack as many as possible of these lights into the Tx was the first task when starting the mechanical design. And since the shape of the FFU is given as cylindrical, the first idea for the LED boards was to basically just stick them to the wall.

TxSU_assembly v1

The first version of the Tx with the light sources. The red dots are LEDs, soldered onto the green boards. The cylinders are the parabolic mirrors where the IR sources will go inside.

As usual, the first idea is not the best: since the LED boards are flat and the cylinder wall is curved, this solution requires a lot of complicated and expensive machining, it is actually almost impossible to manufacture. After some brainstorming a second version was designed:

TxSU_assembly v2 (frames)

The second version: the LED boards are mounted onto frames, which are part of the unit’s structure.

The version with frames was definitely more realistic than the first one, but still, it is a relatively complicated concept. Thanks to helpful feedback from our supervisors it evolved into a third version, where the frames are replaced by pillars, making the design a bit lighter and simpler.

TxSU_assembly v3 (pillars)

The third version: pillars replace the frames. Also, a mounting for the IR sources is implemented: to avoid too much thermal conduction they rest on three pins.

Still, the pillars are quite complicated parts, with unusual angles and a lot of holes in a small volume. But they are feasible, and this current design is a good compromise with respect to feasibility, cost, weight and space constraints. Having sorted out the placement of the light sources, it is now time to add the other components. That is what I am currently doing, and I also started today to make the drawings of the parts.

TxSU_assembly v3

The current state, now with a few more components: PCBs, batteries. Only a few more small things to add and it will be ready.



One thought on “The Flying Christmas Tree

  1. Pingback: “Shit just got real!” | The ISAAC Rocket Experiment

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