This site has looked at arrays of laser modules for launching into space several times before and considers it a very promising approach.
Jordin Kare had a proposed development plan to demonstrate a one megawatt launch system over 4.5 years for $32 million back in 2005. It did not get funded but Jordin is working at Lasermotive and they are providing the laser power system for the space elevator challenge that will be held in April 26, 2009 [tentative]. Laser power beaming will be demonstrated, but the clock on the laser launch roadmap is not running as well as a funded laser launch program.
UPDATE: Look in the comments of this article for a contribution from Jordin Kare comparing microwave launch system to laser launch.
The laser launch system could reach $250/lb to reach orbit.
Demonstration Laser Launch Project Proposal [Proposal made 2005]
1. Efficient conversion of laser power to thrust at MW scale
2. High (~600 s) specific impulse thruster operation using LH2 propellant
3. Complete propulsion system operation
• Significant laser propagation path -- at least several km
• Laser system acquires and tracks moving vehicle
4. Ground launch of laser-powered sounding rocket
5. Air launch (via booster or aircraft) of laser powered sounding rocket to >100 km altitude
* Phase 0 - 6 - 9 months $ 1 M
– Sample heat exchanger (10 x 10 cm) operating at 1 MW/m2 on GN2
– Preliminary design and development plan for MW-scale test vehicle
– Concept validation for overall launch system
• Top level full-scale vehicle design and CAD model
• Optimized trajectory model
• Propagation loss modeled with existing standard codes
* Phase 1 - 18 months $ 5 - 6 M
– HX and brassboard propulsion system operating on liquid nitrogen
• Demonstrate thruster efficiency
• Use 6 km range test site to demonstrate propagation and get to laser far field
– HX and brassboard propulsion system operating on liquid hydrogen
• Demonstrate high-Isp thrust
– Detailed design for MW-scale test vehicle
– Optional wire-guided “flight” tests at 10 - 100 kW scale using PLVTS or LHMEL lasers
* Phase 2 30 months $ 20 - 25 M
– Integrate MW-scale flight test vehicles
• Laser powered vehicle(s)
• Engineering test vehicle(s) for air towing, stability, tracking tests
– Demonstrate flight operations and low-power tracking with test vehicle(s)
– Full-duration static test of MW-scale vehicle
– Wire/rail-guided “flight” test of vehicle
• Verify high-power tracking and vehicle operation
– Laser-powered launch from ground (tower) to ~10 km
– Laser-powered launch from 10 km to >100 km
• Aircraft- or booster-rocket-launched
• Propellant TBD -- baseline of LN2, goal of LH2
Jordin Kare Provided an Update in 2008
Space Access'08: Friday - Session 3, Jordin Kare: Recent Laser-Launch Technology Readiness Progress
- Hit a heat exchanger with the laser light. The exchanger then heats up the propellant.
- Shows ISP vs altitude. Goes from 440 up to 700s.
- 100MW expendable vehicle concept.
- Pressure fed system.
- What about the laser? No one is building 100MW lasers at the moment. ABL is a megawatt class laser.
- "Liars, damn liars and laser builders"
- Alternative is to combine many small lasers together.
- Can scale up by just adding more lasers.
- Reliable since individual lasers can fail without causing whole beam to disappear.
- Shows conceptual design of laser modules with optics, power, etc.
- "Laser diode arrays are great"
- Off the shelf 1kW laser diode, 50% efficient, 3" square, $10k
- Not quite bright enough. Could be used for propulsion but can do better.
- Combining lasers needed some miracles and several miracles occurred within past 4 years.
- Fiber lasers: convert laser diode light at 90% efficient into single mode freq beam. These are easily good enough for laser propulsion.
- Telescope of Celestron size and cost is good enough.
- So the technology is all there.
- Why do laser launch when cheap chemical launchers are available?
- Need less up front costs to prove laser launch than to prove an orbital RLV (Re-usable launch vehicle).
- Almost had $20M to do a sounding rocket scale system.
- $200M to engineer an orbital scale system. $2B to build an orbital system.
- Laser diodes drive the cost.
- Currently down to $1/watt for the raw diode bar. Few years ago this was $30-$40/watt
- 10 year plan if start now to when you are launching stuff routinely.
- Military has gotten interested again in lasers.
- ABL guys are interested in testing their laser for launch.
- What is new? Building real hardware for the Centennial Challenge power beaming contest.
- Have a 10kW laser for tests
This site had previously reported on the space power conference and developments relevant to laser array launch.
Jordin Kare discussed on laser diode power beaming that will be used at the Space Elevator games.
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. They are estimating 10% efficiency, but actually getting more like 13%. They have 8 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). 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. 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.
Jay Penn, Aerospace Corp, described five different powersat concepts that Aerospace has been working on.
One of their concepts is a laser system that is very scalable (480 satellites for 1.2 GW). It uses a layered approach, with pump-laser diodes, microoptics, and a radiator on the back. Output beam is about a thousand nanometer wavelength. He thinks it the most promising architecture of those considered.
100 KW solid state lasers back in mid-2007