For the obvious reasons, I invariably get too busy to blog exactly when things get interesting...
 Brian inspecting the load-simulator car |
 Simulator car on its way |
 Simulator car pulling away, image getting distorted |
 Mirage effect kicking in. (This won't happen in vertical lasing) |
 Infra-Red image of car, showing the laser illumination |
 Mirage effect in IR |
The last bit of testing is what has affectionately come to be called “The melt test” – running full power through both the beam director and the climber, for the expected duration of the climb, and looking for smoke.
Smoke can originate in either of the two subsystems.
The beam director has to handle the entire 8 kWatts, and when the optical pass narrows, the beam becomes very intense. The lenses and mirrors have to be of high quality and kept very clean – if they absorbe even a small fraction of the light they begin to warm up, which causes distortion, and can increase the rate of heat absorption, resulting in, well, smoke.
The climber takes a much more diffused beam, but it is not transparent – it actually captures most of the light, converting some of it to electricity, and regrettably, some of it to heat. If it gets too hot, its electrical conversion efficiency drops, and this creates more problems, since (for example) if the climber slows down, air cooling drops significantly, causing it to grow hotter.
For this reason, the teams monitor the health of the beam directors and climbers, and adjust parameters such as laser power, beam divergence, and throttle settings, in order to keep the climber operating in its sweet spot. It’s a bit like drag-racing – if you just “floor it”, you’ll most likely either choke your engine or tear your vehicle apart.
And keeping with the drag-racing motiff, KCSP chose to implement a rather ingenious load-simulating system. Instead of connecting an electrical load to their climber, and using a fan to simulate air flow, they chose to mount their panel on an eMaxx R/C car, and hook a second electric motor in reverse so it impedes with the first motor – as a matter of fact the load on the first engine of the horizontally moving car closely resembles the load on the motor of a vertically moving climber moving at the same speed.
The upshot of this design is that they get to have a lot of fun (which was a big part of the motivation for it, no doubt…) driving a beam-powered R/C car across the lakebed.