Here’s where I’ll be picking up from yesterday, and blogging today’s session, as I get time.
The first speaker this morning is Jay Penn of Aerospace (again) talking about laser power beaming demonstrators. He’s describing the same apps as yesterday for the military, but also talking about space-to-space beaming for other spacecraft. Reviewing yesterday’s talk with concept that can put 2.5 MW into the grid per satellite. Two solar panels, two laser transmitter panels on a deployable backbone. Providing more of a description of the “halo” orbits than yesterday, but I still don’t understand it from an orbital mechanics standpoint. I’ll have to read the paper or talk to Jay later.
He’s showing several charts that demonstrate how inserting technology into the laser system can dramatically increase the power available per EELV flight (not sure how relevant this is, other than as a benchmark, because it’s very unlikely that an economically viable system is going to go up on EELVs). Also shows that you don’t save much money by scaling down the system to smaller power levels–R&D dominates the costs. His bottom line is that we could do a 125kW demonstrator on an EELV, that could scale up to 200kW with technology insertion. Laser appears to be the only practical means to provide acceptable small spot beams from GEO. Laswers have 10,000 times smaller spot for the same range and aperture compared to microwaves. In response to a question, he notes that the individual lasers are not phased, and they don’t need to be. There is a question about maintenance/repair. They hadn’t looked in detail but a quick look suggested that degradation wasn’t a major issue. he makes one other point–the system was self-lifting from LEO to GEO using ion propulsion, to save mass.
Now another talk by Jordin Kare, on laser diode power beaming. Talking about the NASA beamed power Centennial Challenge. While it’s about elevator climbers, it is essentially a contest to build a beamed-power system. Prize has almost been won, but not quite, and is now at $500K. None of the teams are using lasers. Laser-Motive (his company) was formed to develop laser power beaming technology, but the current focus is on winning the prize. Their concept uses a fixed set of laser diodes and optics, with a steering mirror below the climber. Operating on a shoestring. They are estimating 10% efficiency, but actually getting more like 13%. They have eight kW of laser power to deliver a kilowatt to the climber. Got good price on “seconds” for the lasers (a little less than $10/watt so about $80K) Didn’t care about beam profile, as long as they got the power on target. Didn’t do custom optics–used float-glass and amateur telescope mirrors, with old HP stepper motors to drive them. Lasers share (more expensive) parabolic mirrors. Bought some 50% efficiency cells that can operate at ten suns, with help from Boeing. Unfortunately they had some final integration issues (smoking a power supply) that prevented them from winning, but no on else won either.
The 2008 contest is a kilometer climb up a rope hung from a helicopter (the faster the climb, the more the money)–lasers are the only option. DILAS is offering to build a custom system ($35,000 for 2.5kW), and will set a new radiance standard. Can go to much more range with bigger optics and more power. deliver tens of kilowatts at tens of kilometers with this technology.
Laser-Motive is ready to build these kinds of systems tomorrow. Could be used for ground to aircraft or ground vehicles of mirrors on aerostats, or air to ground to simulate space-to-ground. ISS to ground is also a possibility. Next steps: higher radiance, coherent systems (e.g., fiber lasers), lightweight low-cost optics, and then operational systems.