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.

A wee bit off target

Bull's Eye

Catch me if you can

Having completed the first set of tests, the pirates are now moving to the integrated testing - tracking, and full power/duration.

This set of images shows the fine calibration process. A truck carrying the target beacon drives down range, and the system locks on and starts following. Using a manual process, the laser spot is brought right to the center of the beacon. (In the first image, the laser spot is about half a diameter away)

Once locked, the system is tenacious – As fast as Danni (image 3) can weave and run, the green spot could just as easily have been painted on the beacon panel.

With basic tracking demonstrated, KCSP is getting ready for their grand finale – an all systems combined full-power tracking demo also known as the RC car test.

The day is drawing short now, and we still have two more teams to schedule. UMichigan is up next, and USST is getting ready with their equipment – they were held up at both the border and the base gate, and so are more than a day behind.

Aim Here.

Reflection Testing

First Light - Panel lit at 100m - Click to zoom in

It's a long walk back up the range

The first thing we do during field testing is look at beam control and reflections, at low power.

The pirates self-sufficient as ever, have their own sponsor-laden calibration target. The calibration process is straight forward – you aim for the center of the cross, and see where the laser hits (and how big the spot is). Adjust, and done.

Calibration is best performed at 1 km, but atmospheric disturbances (hot air shimmering all over the place, and even the mirage effect) make that difficult as the day grows longer.  One lesson learned – calibration during the games will have to take place before 8am.)

Once we know the pirates can shoot accurately, we want to look at the reflections the climber generates. For that we use the same U-Haul (A thousand uses and two now, and counting) as a portable darkened room. We locate it away from the laser, with the climber near the back wall, and illuminate it. The reflection are easily visible on the projection screen.

Or are they? We see nothing. Is our equipment mal-functioning?

As it turns out, the Pirates’ climber is almost completely diffusive. There are no direct reflections – whatever light is reflected, it comes out in all directions, and so does not generate any visible spots.

We use a sensitive power meter to look for the reflected light intensity, and only from about 10 m does it register in the mWatt range. (In the games, the climber is always at least 100 m away from the goggled operators, and 1000 m away from anyone else.)

Finally, we want to remove the climber and measure the truck itself, so we can eliminate the background measurement. As we do this, we already realize what is about to happen – the measurement without the climber is actually more reflective… Since the climber is a better diffuser than the truck, it was actually shading it…

In short – KCSP passes these two tests. Next up is full power/duration testing, and tracking testing.

KCSP's Ryan monitoring the climber tracking system

KCSP's tracking system showing nice performance (The green laser sits right at the center of the Red beacon)

KCSP's optical system, showing the path of the green practice low-power laser

For calibration, the beam exits through this opening, traveling horizontally. During the games, the beam will exit through a similar aperture in the roof of the trailer.

The pirates are back in force this year, no longer relying on helio beaming – this year it is lasers, and only lasers…

This series of images shows the transmitting end of the system – the beam director. During the games, the beam director is fed 8 kWatts of photonic power delivered by fiber optic from TRUMPF’s laser truck. During practice, the fiber optic is replaced by a green low-power laser designator, so the system is eye-safe.

KCSP’s robotic mirror senses the position of the Red beacons attached to the climber, and aims the laser beam into them. This tracking method (called TTL, or through-the-lens) has the advantage that if atmospheric disturbances affect the beam going out, they also affect the image of the beacon coming in, and so the effect cancels out.

The image of the target is produced by the beam-monitoring camera, which is a safety feature designed to show us where the system is aiming, just so we have a sanity check on the state of the tracking system – we’d like to know if it is oscillating, or dead, or maybe just lost, so we can shut off the beam. Ideally, throught the climb, the image on the screen will always have the climber sitting steadily at its center, even though the background sky will be moving.

To the unaided eye, btw, the competition lasers are invisible (they are in the Infra-Red part of the spectrum) but the tracking cameras will pick them up just fine.

An interesting feature of the optics box are the blue air tubes (with the orange nozzles) which serve to keep the optics cool – with 8 kWatts of power going through them, even high-quality optics get warm, and the change in temperature can cause them to reduce the quality of the beam. The whole box is also pressurized with clean air, so dust is kept out – dust particles can both damage the lens mechanically, or become local heating spots that will damage it thermally once the beam is turned on.

The Kansas City Space Pirates are:

• Rich Brull
• Ravi Durgavathi
• Terry Fredrick
• Chad Hampy
• Duane Johnson
• Martin Lades
• Dan Leafblad
• Warren Moore
• Frank Smith
• Ryan Smith
• Don Stowers
• Brian Turner – Captain