First successful climb, by LaserMotive, climb time: 4:02.  Second successful climb, by LaserMotive, climb time: 4:01. Unofficial climb distance: 899 m. Unofficial climb speed is therefore 3.7 m/s, which is squarely in the $900k bracket – Congratulations to Lasermotive!

Unofficial empty weight is 4.8 kg. The unofficial payload is 0.58 kg. So the score, unofficial, is (speed times payload ratio) 3.7 * 0.59 / 4.8 = 0.45. If other teams make it into the $900k bracket, the scores will be used to determine the order of the winnings.

Kansas City Space Pirates also climbed, but a lot slower, getting to 850 m at 8:00, where we had to stop them due to a satellite lasing window closing. They were still moving when we shut them down, and their average speed was approximately 1.875 m/s.

Today’s Schedule is promising to be very exciting:

• USST will go first, since they didn’t get a climb window yesterday.
• LM will go next, and will sure be trying to get into the 5 m/s bracket, for the larger prize purse.
• USST will then get their second climb window, and lastly
• KCSP will get their second climb window and try to improve their performance.

Keep in mind that all teams have the ability to go 5 m/s – the games are ON!

“We predict too much for the next year and yet far too little for the next 10.” — Neil Armstrong

Regrettably, Team NSS had to withdraw at the end of last week as they were running out of money (and time) to get everything ready for the games. A shame really, since they were able to put together a remarkable system in a relatively short amount of time. (If you recall, they were trying to rebound from a loss of a major component in their system).

Team Overview:

We’re thus left with three teams: KCSP, USST, and LM.

This would be a good time to make a little comparative study among them. The formulation of the power beaming problem (The range, the fact that the receiver is mobile) drove all the teams to use laser-based systems, but beyond that, the teams are very different from each other.

Perhaps the most visible difference between the teams is not in their technology, but in their backgrounds (and character). Since none of them are newcomers, we know a thing or two about them:

Lasermotive (LM) is our “industry” team, led by long time laser industry expert Dr. Jordin Kare, and really almost doing this as a hobby. Another of their hobbies is this. They are based in Seattle, and one look at their sponsor list makes it clear that they are a force to be reckoned with. Laser motive is on its second year at the games, having made their debut in 2007	USST is our university student team (Team Captain is Bill Voss, also from Seattle, and the students are from the town of Saskatoon, Saskatchewan), except that nothing about it is typical of a student team – they are organized, highly professional, calm and collected – and have outperformed all other teams in all previous competitions so far. USST is the most experienced team at the games, having participated in all challenges since 2005.	Kansas City Space Pirates (KCSP) are our robotic-club hobbyists, except (guess what…) nothing about them says “amateur”. Their engineering is superb, they have recruited a top-notch panel of consultants, they are consistently the most prepared team, perform the most detailed testings and rehearsals, and their attention to detail is unmatched. Team Captain and chief engineer is Brian Turner, and they are based in Kansas City, MO. This is KCSP’s third appearance at the games.

Technically, the teams ended up spanning the gamut in practically every trade-off in the design space: We have different laser wavelengths, different PV technologies, different beam intensities, different thermal designs, different tracking and aiming mechanisms…

(Another reason to miss NSS, btw, since they have settled on yet another operating area, completely different in all respects from each of the other three)

I cannot yet give up specific information, but I can guarantee to you that we have a very good race coming up. None of the teams is a clear winner by any stretch of the imagination. All three are very capable, and all three are shooting for the 5 m/s prize level.

Break-downs and other unforced errors notwithstanding, if the teams get to fully exhaust their capabilities, it will be very interesting to see which system ends up on top. Having invested two years and a lot of personal funds into the development of their systems, I truly hope all three make the prize threshold.

We will be able to divulge much more about the technical aspects of the systems during the games, but until games day (11/4), some cards need to remain face down.  Maybe we’ll some more information leak out as the week progresses :)

One of the nice things about Near Infra-Red light is that it gets picked up by regular cameras, showing up as some combination of colors, unique to each camera.  In the case of my camera, it shows up as this pink-purple hue.  To the naked eye, the climber seems unlit.

For more videos from this test session, check out the Space Elevator Blog (”There’s cool, and then there’s Über-Cool”), especially the last video, where Ted’s Maniacal laughter reveals his true nefarious character – who knew.

(The test was conducted at TRUMPF’s facilities in Detroit – they make the cool lasers that put your car together.)

Robert Winsor, NSS's Laser man, and Nic DeGrazia, our filmographer in residence, observing the NSS climber during the power test.

NSS's TPV array

Moving to photovoltaics, NSS settled on a PV technology called TPV – Thermal Photovoltaics. These cells are optimized to operate with thermal IR radiation (longer wavelength than TRUMPF’s NIR 1030 nm beam) but have acceptable performance at this wavelength as well. More importantly, these cells can work with high light intensities, which means that you can get more power out of a smaller (and thus lighter) array, if only you can get the transfer the excess heat away from the cells.

What this calls for is a good heat exchanger – and this turned out to be the highlight of the day.

Check out the images of the climber. The TPV cells are completely immersed in acetone (4 ounces) which is vigorously boiling away under the heat load of the beam, completely evaporating every 15 seconds – only to be continuously captured by the bags and dripped back down onto the cells.

Acetone was chosen since it has the lowest boiling temperature, and so will be most effective as the working fluid.  This is a basically a cooling tower (or heat pipe) – something that was used by Centaurus Aerospace back in the 2005 games – using water in vacuum, in their case. The acetone solution is a lot lighter, and yes – more flammable.

We’ve looked into this issue, and we recognize that there are failure modes under which the system can develop a leak, but we feel that a) the acetone is far removed from any spark sources, b) there is only a small amount of acetone in the system, and c) there is no place for leaking acetone to accumulate, and so the consequences of an acetone leak are acceptable. We will also be monitoring the temperature of the PV receiver, and if we see it rising above the boiling point of acetone, we will know that the acetone is depleted and the climb is over.

So after observing the climber operating under full laser power, and with some modifications required, we’ve decided to ok the design, and allow NSS to catch up and participate in this year’s challenge.

One of the nice things about having multiple teams is that you get to see different ideas at work, and NSS is definitely not short on ideas.

Their first climber design featured a thermal (rather than photovoltaic) receiver, based on a Stirling engine. (Stirling engines are high efficiency engines often used for solar power generation) Stirling engines are a difficult proposition for a Space Elevator climber, since they typically weigh a lot more than a PV panel, and so NSS had to design and manufacture their own engine – and it is indeed a beauty. Using Helium as the working fluid, this engine also uses a transparent cylinder head in order to get the laser beam directly into a thermal absorber that is placed inside the cylinder – a perfect way to avoid the latency associated with the thermal mass of a regular absorber plate.

The problem NSS ran into was with properly sealing the engine while keeping the weight down. Anyone who’s ever worked with Helium knows how difficult it is to seal – it is a noble gas, and so is monatomic, which means its molecules are really small, and they get around most seals.

The other problem faced by thermodynamic engines is that while they are able to capture 100% of the energy of the beam (unlike the 30-50% of PV cells) they have to waste a good fraction of it at the heat exhaust side, and this gets worse the hotter the exhaust is. Which means that a thermodynamic engine needs to be coupled to an efficient heat exchanger – something that NSS started to design as well.

As it turned out, NSS was not able to solve the He sealing issue, and started working fast towards a photovoltaic “plan B” climber. However, not all of the effort was wasted – the heat exchanger design turns out to be very important in keeping their PV cells cool – more on that on the next post.

As a side note, Bert Murray and Matt Abrams have vowed that if the prize money is not awarded this year, they will solve the Helium seal issue and be back next year with a working Stirling climber.

To the point – Team NSS Bert Murray, Captain) has used the delay in the games to their advantage, and have notified us a couple of weeks ago that they are ready to try to qualify. (NSS originally took a hit when sponsorship of a major part of their hardware fell through)

We are expecting to finalize the competition date any day now, and so NSS has really cut it close. We’ll be traveling to the TRUMPF facility in Detroit early next week to witness the qualification, which will involve a demonstration of the transmitting and receiving optics operating at full power, tracking, reflection measurements – 2 days of testing overall. (we did something similar, if you recall, with LaserMotive about 3 months ago.)

Since Chicago is practically next door, both Ted Semon of the Space Elevator Blog and Nic Degrazia of Bitter Jester Creative will come over to watch and report.

Expect some preliminary reporting on Monday, and an Aye or a Nay late Tuesday evening then.

Meanwhile, we’re working hard on finalizing the date for the games – real soon now!  I will of course let you all know just as soon as I find out myself.

If you’ve been following the games, you must have noticed that the last 2 months were taken up by solving a problem that has nothing to do with power beaming – constructing and controlling the 1-km vertical raceway.

Done.

And just in time, USST produced this nice video about what the games are all about – enjoy!

Oh, and btw, I believe USST’s 1 km battery-powered climb must have broken some record of some sort (sorry Shui!) – more on that as soon as I get the footage ready for posting.

The image was taken from the mock climber, at the climb starting altitude of 100m (330′). The helicopter will be flying at a height of 1300 m (~4500′)

While over the last week (and the next two, most likely) we are pre-occupied with helicopter flights, I do promise to get back to the main business at hand – power beaming – just as soon as possible.

A quick teaser – team NSS are racing against the clock to qualify in time for the games. They were not ready when we held the test flight in Dryden in July, and have been racing to take advantage of our misfortune. I’ll keep you posted on their progress.

Ben

Targets at 1 km

Mark Boots and Nathan Windels in front of the main "barrel cam" display, showing the dark (unlit) target at 1 km

Note the bright (lit) PV target at 1 km. In the background, Ariq Chowdhury is monitoring the climber telemetry data.

USST's beam director station

Tuesday and Wednesday were dedicated to field testing – as much as we can get done before the helicopter flight on Thursday.

While KCSP are here for their second round of testing, USST is here for their first, and so they get priority on the laser.

Because of several late-in-the-game design changes, quite a bit of USST’s system is still untested, so there’s a lot of tension in the air – if a major flaw shows up, there might not be enough time for them to fix it.

The initial tests are successful, and establish that tracking works, that the beam director can handle full power (that was a big unknown) and that the climber can take this photonic power and extract enough electrical power out of it to make them competitive. This is also the stage where we look at reflections coming off of the climber,  and confirm that no significant reflection go outside of a 15 degree cone from the vertical.

In true USST fashion, everything just falls into place. They might be late coming into the party, but once they’re there, they catch up awfully quick.

With qualification behind them, USST spends Friday on system optimizations, measuring power and temperature profiles, and making sure they can get the most amount of power out of their PV array.