Here’s the answer of what we did in response to the recent question of what to do after having a ribbon tear in the late afternoon on a Friday right before a weekend we wanted to do testing in.

First, we blunted the tear by (perhaps counterintuitively) punching a bigger hole, which was round and smooth. Machinists and techs mostly know about this kind of solution, but I knew the same thing from a different perspective (my materials science background) – if you have a crack, blunt the tip to reduce the stresses and prevent it from continuing.

Next we took some steel staples and put them across the rip. Since we were only planning on loading the ribbon to a few hundred pounds of tension, we knew that the unripped portion would be able to handle the load by itself, we just needed to keep the rip from growing, and keep the ribbon flat an untwisted.

The ribbon worked fine over the weekend. Since our vehicle rollers are aluminum, we didn’t take the risk of running them over the steel staples, even though it probably would have been fine. We just stopped the ribbon before the staples got to the vehicle, then we backed up the ribbon.

On Monday I brought the ribbon to a local belt shop, and they fixed it by the end of Tuesday (we sacrificed a short straight piece of ribbon so that there would be 2 instead of 3 splices, and to keep the loop the same length):

The splices are a bit more noticeable than in the original, but overall they look great. Now it’s time to go onwards with more testing!

Pop quiz: It’s 4pm on a Friday, and you’re planning on doing many important runs with your loop ribbon on a treadmill over the weekend. There’s only two weeks left for testing. You don’t need to tension the ribbon much beyond 300 lbs. You accidentally tear the (tensioned) ribbon one quarter of the way through its 4 inch width. The shops that could repair the ribbon are closing in less than an hour. What do you do? What do you do?

I will post what we did later this week. In the meantime, post your ideas in the comments section.

What do you do when you need to produce a video of your power beaming system powering a vehicle to climb at least 20′ up, but the available indoor space is not quite tall enough and you’d rather not rent every single day you want to test? Build your own test rig!

It’s quite the monster. This contraption is roughly 30 feet tall, and the loop ribbon (which we purchased back in the spring, long before we designed the exact test rig) is of such a length that it doesn’t even start until nearly 7 feet up (but we made it 30 feet tall because of the height of the loading dock, our mirror at the bottom, etc.).

Let me tell you, standing that thing upright is quite a chore for 7 or more people, but it goes smoothly. And since it has segments, it can be reduced in height and used indoors as well. It’s not quite as high tech as a laser, but it’s still a very cool device.

I’m constantly amused by the kinds of things it is possible to purchase nowadays. Here’s a case (literally!) in point:

It’s a custom-built case to hold some electronics. Carsten sketched out the box size and hole locations in the supplier’s software, then submitted it and had them make the box and screen print our logo on it. And all for not much more than it would cost to buy some other box that wouldn’t have fit as well. Spiffy!

The ANSI Z136.1 rules outline what laser warning signs should look like for various classes of lasers, and where they should be placed. Here’s a photo of one of ours (with one piece of info Photoshopped out):

If you’re using a Class IV laser, you need to have signs like this posted in the appropriate places. When you go outdoors, regulations get a little trickier (because of the fear of a laser’s effect on airplane pilots), and ANSI Z136.6 comes into play. We’ll be working with the FAA to obtain proper permits for all outdoor operation of our laser.

Here’s Kim Hicks, the first person to “drive” our vehicle when it was powered solely by laser, looking via our big mirror at the vehicle with some PV cells hanging off it:

The reflected image has a yellow tinge for a reason. That’s the same mirror as in my last post, except now you get to see the coated side. The coating reflects our (near-IR) laser beam very nicely, but does not reflect visible light evenly, hence the color cast.

Sorry for the delay in posting lately – we’ve all been (unsurprisingly) very busy with testing and development.

There’s not much I’m going to say about our mirror, at least not now. But while we were doing some work on it, I took this photo, which I think looks cool.

After we received our laser back in May, we started testing it. First came a set of bench-top tests. We used a foamed carbon block as our beam dump, and here’s what it looked like during the second test of one session:

After the tests, you could see some permanent marks on the beam dump:

Those marks on the foamed carbon block are from the carbon oxidizing, which doesn’t happen until well over 1,000 degrees C. The calculated power density from the test is somewhere over 220 times normal solar intensity (outside Earth’s atmosphere), i.e., on the order of 330 kW/m^2. The intensity is this high not because the laser put out so much power (it was actually low for what the laser can put out), but because the beam stop was close to the laser and therefore the laser energy was concentrated into a very small area.

These photos highlight yet another reason why everyone must be extremely careful when working with class IV lasers. Even if the total power used in one test is relatively low, it comes out of a small area and hence is very intense. Safety is the highest consideration when working with lasers, and we take the ANSI Z136.1 safety rules very seriously.

Oh, and as a result of our tests, we now know the laser stack output at low power, and overall we’re happy with the performance of the laser stack. We’re testing regularly, and will have more to report on in the future.

A video team from the BBC brought along Michio Kaku to interview us and to video some of LaserMotive’s early hardware during May as part of a documentary they’re working on about future technhology (the episode we’re featured in also talks about carbon nanotubes, for example). The series will air sometime this fall; we’ll post more info once we have it.

The interviews were focused more on the space elevator than power beaming itself, but we were proud that they thought LaserMotive would be the best group for them to showcase power beaming technology. Dr. Kaku had some very good questions, and for someone whose prime work is in string theory, he was very professional in his job as a TV interviewer – he easily handled multiple takes, making it always appear fresh.

Regardless of what the focus of the filming itself was, having media guests come from overseas was a great way to give us a hard deadline, and we accomplished a lot of work. I was too busy throughout the day to do much photography, but I did manage to capture their video guy and audio guy doing some prep shots:

During the day of filming, we were able to borrow a neat contraption from their videographer to mount our own camcorder to our vehicle and get some video of the vehicle’s ascent of the ribbon, from the vehicle’s perspective (1.8 MB, Quicktime 7 required). The ribbon height is only about 15 feet or so; it’s limited by the height of the building we’re in.

We want to thank the BBC for their visit, and their patience (the producer commented about TV, “Never work with animals, children, or scientists!”). We’re looking forward to seeing the episode, probably around the same time we’re heading to this year’s Power Beaming competition!

The little device below (still in its protective packaging; a one-foot ruler sits in front for scale) can put out one kilowatt of laser light. That’s roughly 1.3 horsepower. Light comes out the small inset area at the end.

For comparison, modern push lawn mowers seem to have 5 or 6 horsepower. This laser is roughly 25 times as powerful as one of the bars used in earlier tests, which was already well past the threshold to classify as a Class 4 laser. Safety precautions are critical whenever a laser like this is powered on. We may talk in a future post about ways in which we’ll reduce the dangers from operating the lasers. For now, we’ll just marvel at great things coming in small packages.