Climber Melt Test

Monitoring the climber temperature

The next test is the Climber Melt Test.

If you recall, this is the test where the climber is illuminated at 100% power for the full climb duration (plus margin), and we confirm that it can take the heat. We also look at the amount of power produced by the climber, to confirm that it is sufficient to move it up the cable at competitive speeds.

A few posts ago I described how KCSP embellished on this test by designing a beam operated R/C car that that carried the PV panel on its tail

The LM setup is more conventional, and while it does not provide a complete end-to-end functionality test, it allows for much better analysis of what’s going on while beaming. The climber is mounted on a vertical stand, with a 45-degree mirror underneath, and the horizontal beam is bounced onto its underside. The test stand can also be used as a vertical treadmill, but this test is not part of our standard test suite. A ducted blower give the climber the air cooling and aerodynamic loading it would have gotten during a real run. (Air cooling is allowed in the games, even though it is not representative of real space conditions)

The first image shows the climber being hit by the beam (notice how little light is reflected out, even in this point-blank image).

The second image shows how LM track the temperature of the climber – an IR imager for locating hot spots, an IR thermometer for getting an average readout of the front side of the panel, and thermocouples embedded on the back side of the panel.

During this test we also get to see how much power they are able to extract, and just like KCSP, these guys are confident in their performance.

Only I know the comparable performance metrics, but I’m not telling!

Hot dogs, check. Laser goggles, check.

Not your ordinary campfire!

Hot Dog!

No kidding. LaserMotive does not believe in wasting photons. If I’m going to make them fire the system at full power just to see that it does not melt, they are going to make lemonade, well, actually they are going to cook hot dogs.

After all, what tastes better (to a laser geek) than 808 nm cooked meat?

So yeah, to my astonishment, the BBQ roasting forks came out, as did two packages of hot dogs, and away we went. I’m glad to report that cooking was uneventful, and there wasn’t too much grease dripping.

As an aside, cooking a hot dog with a laser is not really much different than cooking it with an electric grill. The power level is comparable, the wavelength is a bit different (and so you want to wear protective goggles), and the toaster is just a bit more expensive, but otherwise there’s an on-off switch, a power dial, a bottle of Haynes, a bottle of Dijon, and squeeshy hot dog buns. There was no beer, even for guests.

As another aside, the laser is indeed invisible, but the camera captures it just fine – camera CCDs are sensitive to this wavelength. As a matter of fact, even the human eye captures a bit of it, but this is misleading – a faint red impression is only the tip of the iceberg in terms of the total light intensity. Hence goggles are worn by everyone)

The official results of the test: need relish, otherwise ok.

Onwards to the climber melt test.

Tom Nugent inside the belly of the beast

Jordin and Tom tracing out the beam

Carsten demonstrating the tracking and control screen

The following couple of posts are from the trip we took to Seattle to evaluate LaserMotive’s power beaming system. Unlike the TRUMPF based teams, LaserMotive own two laser modules of their own (manufactured by Dilas) and so can run full power tests at their facility.

LaserMotive was formed around the competition, but is setting its sights on Power Beaming as a commercial application. They are led by Dr. Jordin Kare, an old hand at the laser business. LaserMotive made its first appearance in the 2007 Space Elevator games, but equipment problems (too many pre-owned components!) got in their way.

Not this year.

LaserMotive is using a pair of vehicles as their power beaming system – a beam director trailer, and a control vehicle. (Both KCSP and USST have integrated both functions into a single vehicle). The main reason is that because of the type of laser source they use, their optical system is just physically larger, as can be seen in the first photograph.

The system uses two parallel beams, which originate in the two cube like devices at the back, are folded over several times as they bounce between the mirrors, and eventually exits through the top hatch after having bounced from the large bottom mirror. For testing, a last mirror is introduced at the top, diverting the beam so it comes out horizontally out the back of the trailer.

During testing, the tracking and control system is located in the beam director trailer (notice the excellent taste demonstrated by the choice of sitting hardware), but during real operations, it will be located in the control vehicle.

Just like when operating the Death Star’s main laser (the original Star Wars, aka Episode 4) Carsten has to lean forward into the instrument panel as the beam radiates over his back. (Well, I’m getting carried away, he doesn’t. I just like to think that he would have to… Star Wars was the first film I ever saw, and so serves as a standard to many things I do.  But I digress.)

Other than minor corrections, the system is definitely ready to go.

Next up, the melt tests.

LM's Jordin Kare and Dryden's John Piatt discussing photovoltaics and reflections

Lightweight mechanical design is as important as efficient electrical design (courtesy LM)

LM's crew handling their climber

LM, now in Red!

LaserMotive is one of the Dilas teams, and since they own their power beaming laser, they have opted to conduct most of their tests at their own facility. This means we only have to conduct a minimum set of tests with them at Dryden - a climber evaluation test in which we poke and prod the climber looking for any mechanical suspect points, and a climber low power reflection test, which tells us what sort of reflection pattern the climber generates.

Any reflections that are not downwards pointing (within 15-degrees of vertical, actually) are considered potentially hazardous, and so have to be characterized. Using the low power test, we found none, but we’ll look for more during the high-power tests at their facility.

The climber also appears both light-weight and robust, and it appears that there is no risk of it coming off the cable and tilting – something we specifically look for as a potential failure mode.

LaserMotive brought a low-power 808 nm laser for the reflection testing, and are letting McGill University use it for their reflection testing as well (McGill is also an 808 nm team).

This level of sportsmanship is mandatory as far as I’m concerned…  The teams are fiercely competitive, and jealous about their secrets, but nobody wants to win on a technicality, and resource sharing is common all around - there’s a real spirit of “may the best team win”, which makes it all worth while.  This is a science and technology challenge, not Survivor… (That said, when the competition is in full force and people are under stress, some sparks might still fly…)

Back to lasermotive though, looking at their climber, it is obvious how much thought went into efficiency – a Space Elevator climber has to be efficient at converting the laser into electricity, efficient at using the electricity to power itself, and lightweight.

This year, there is no minimum weight requirement, and the teams indeed produced some very weight-efficient design. I should probably look at weight comparisons between last year’s climbers this year’s batch – I’d guess they now weigh about 10-20% of what they used to.

We will only see LM’s beam source in about 2 weeks, so I’ll have more pictures then.

LaserMotive are:

• Jordin Kare
• Tom Nugent
• Carsten Erickson
• Don Moore
• Bryan Tillotson
• Steve Beland
• Nick Bratt
• Steve Burrows
• Brent Davis
• Joe Grez
• Mary Kay Kare
• Jeff Alexander
• Stuart Allman
• Michael Brannan
• Dave Bashford
• Bill Boyde
• Nick Burrows
• David Truax