A couple of years ago, we noted the effects of intense laser beams on beam stops such as foamed carbon. In that post, we used a 1kW laser at low power, only a couple hundred watts if memory serves. It was also less than one meter from the target, and was on for less than a minute. Yet we still oxidized the carbon, which was evident before seeing the burn mark – it was glowing slightly orange with the laser on.

Last weekend we took our new 2kW+ laser and fired it near full power. It was above 50% power (we ramped up slowly from 50% to ~90%) for nearly five minutes. This time, the target was roughly 7 meters away, and the beam at the target was roughly 2 inches by 8 inches. Not only did we still oxidize the carbon, but we fried off some surface layers of carbon and then wound up cracking the block all the way through! You could still feel the heat coming off the back side of the block a couple of minutes later. Here’s what the block looked like a few seconds after we turned off the laser:

Yes, it’s still glowing red hot (the small red dot is our alignment laser pointer). And here’s a close-up a few minutes later, showing the oxidation damage as well as the crack (we’re pretty sure it was thermal stress that cracked the block):

These images just reinforce that the level of power we’re using for power beaming is beyond “just” eye danger and well into the realm of immediate skin danger – at the peak in the center of the beam, the power density was probably greater than 300 normal solar intensity. Our lasers from 2006 were powerful but the brightness was not as high as the new laser. Dilas has done an impressive job in increasing the brightness of the laser, and as a result the beam is much better collimated, so it stays very intense over a much longer distance. That is part of what enables us to beam adequate power over a kilometer away. It is also why so many safety precautions need to be taken in order to beam power outdoors (e.g., for the Beam Power competition).

I want to welcome Brion Toss Yacht Riggers as the newest sponsor of LaserMotive.

Early on, we tried making our own continuous loop cable, but the quality was not stellar, and the cable eventually wound up fraying and breaking. After much searching, we found a local company that still practiced the old art of making long splices in steel cable. As you can see, the results are pretty nice:

I’m told that the process is somewhat labor intensive, but the quality of the final product is great. We’ve got the pictured cable mounted on our big treadmill, and we’ve also made a much smaller treadmill that also has a Brion Toss cable on it.

Thank you to Brion Toss Yacht Riggers for their support of LaserMotive!

Actually, we did need a hole in our trailer. Since the power beaming competition rules specify that teams must bring their power beaming source in some form of “big box” (a trailer or cargo container) from which they aim their beam roughly vertically, once we bought a trailer, we needed to modify it.

Here’s a view from inside of the ceiling, shortly after we bought the trailer:

And a little while later, after some great work by Brent and Don (new members this year), we have the following view from roughly the same position:

It’s an even more impressive difference in person. In addition to the nice portal for our beam, the inside has lots of wiring and plumbing; the interior is painted; we have lights; and much more. And as part of the safety rules, we needed to install warning lights up top. Here you can see the red light through the roof portal:

There’s lots more exciting progress on multiple fronts, and I hope to be able to tell you about some of it soon.

Here’s a cool photo I took last week during a simple test we were doing outside our shop:

When the camera is very close to the laser beam path, you can ‘see’ much of the beam due to scattering from dust in the air. (And for the record, it’s just a laser pointer, not our dangerous laser.)

Here’s what one kilometer (the travel distance for this year’s Power Beaming competition) looks like, at least when seen horizontally along a bike path near our shop. (All photos were taken at a maximum zoom of 55mm on a Nikon D40 while looking towards the tracking base station set up under the bridge. The two dark blobs under the bridge in the first photo are cars we used to move the equipment down there.)

200m:

400m:

600m:

800m:

Finally, 1,000m:

It will be very interesting to see how that distance looks when oriented vertically.

If you were at the 2007 Beam Power competition, you probably saw our 18′ tall treadmill. It was very useful for testing our vehicle, and so we of course wanted to use it for this year’s system. We’ve “upgraded” it to handle the steel cable for this year’s competition. The cable tensioning mechanism is easier to use than last year too. Last year we had to tighten two bolts to move one of the rollers. This year we have a pneumatic mechanism which angles one of the bicycle wheels (also a new feature) to add tension, so it will be easier to calibrate. There’s a simple DC motor at the base with a small tire which can drive the bicycle wheels, so we can do lots of testing at various speeds.

We’ve also built a smaller, ‘bench-top’ treadmill for on-going development work, shorter testing, and efficiency measurements. But when we want to perform something like an endurance test, we turn to the big one.

We want to again thank one of last year’s sponsors, Pacific Integrated Handling (PIH), for their donation of some great Bosch extruded aluminum hardware, which enables us to build structures like this (the frame itself is from elsewhere, but the mounts for the wheels and various other structural elements are from PIH).

Question: Which wire do you cut (disconnect)? The red one? The yellow one? Which?! Time’s running out!

Answer: All of them!

No, it’s not a bomb. It’s last year’s photovoltaic (PV) array. We’re reconfiguring the PV array for this year’s competition, so I’ve been disconnecting all the wires to each rail and then removing the rail from the support structure. The wiring is quite involved and the spacing on the PV rails is, necessarily, quite tight, so disconnecting things without damaging the PV cells was very delicate work. I’m halfway done, and should finish the rest next weekend.

It’s been a while since I last posted anything to this blog. The LaserMotive team has finally caught up on sleep, and worked out our plans for 2008.The first and most important order of business we had to attend to: our own workshop. I’m glad to report that LaserMotive moved into our very own shop in January.

It started out looking like more space than we’d need, as you can see above, but we were certainly able to move our stuff in easily. But it’s already starting to look a bit crowded, because we’re still getting it fully set up, and we’re stocking it with a variety of tools to make our job easier this year.

One of the difficulties in finding a good workshop was to locate one that was tall enough for our treadmill. Luckily we were able to find a good shop, and the treadmill is standing up, waiting for the ribbon to be replaced with a steel cable.

We want to thank Andrews Space once again for their help and generously allowing us to use some of their shop space last autumn. The space at their shop was awesome, but they have their own exciting projects going on there and growing, so we had to move out.

Oh, and one more thing: we’ve got the coolest conference table and chairs now! At least we would if it were still the 1980s….

For those who are interested in maybe joining the LaserMotive team, I will announce shortly an opportunity for people to visit our shop. Check back soon!

Here’s a cool photo from Utah, when Steve, Tamaira and Brian were shining some halogen lights on our PV array from below and testing electrical connections. Click on the thumbnail for a larger version.

This photo does not truly convey the size and intensity of the mess of aluminum shavings that were generated by that little end mill. The resulting product was certainly useful, though. And the person doing the milling had lots of fun doing it, too. And without fun, we wouldn’t be working on this project, so it’s all good.