The Solid State Heat Capacity Laser (SSHCL) has achieved 67 kilowatts (kW) of average power in the laboratory.
It could take only a further six to eight months to break the “magic” 100kW mark required for the battlefield, the project’s chief scientist told the BBC. Hitting 67kW, said SSHCL programme manager Bob Yamamoto, meant 100kW was now within reach.
SSHCL uses an array of many diodes – not dissimilar to the LEDs used in bicycle lights and remote controls – to generate a beam. SSHCL generates a pulsed beam which fires 200 times a second at a wavelength of one micron. However, other experts place more stock in a continuous wave (CW), or “always-on”, beam format.
One of the biggest hurdles to surmount for solid state lasers is achieving a sufficient beam quality. This is a measure of how tightly a laser beam can be focused under certain conditions.
Dr Yamamoto said improving the beam quality was one of the current goals for his team. The Livermore group is one of a number working on solid state lasers and is looking for further funding.
In 2005, Massachusetts-based Textron Systems won a $40m grant from the US Department of Defense to build a 100kW laser by 2009.
I am less interested in the weapon aspect as the potential for laser launching systems for space applications.
The proof of concept photonic laser propulsion system using mirrors to bounce laser light and multiply the effectiveness of lasers generate 35 micronewtons of thrust using low wattage lasers and 3000 bounces.
It has been proposed that extremely small payloads (10 kg) could be delivered to Mars in only 10 days of travel time using laser-based lightsail caft (Meyer, 1984), but in order to do so, would require a 47 GW laser system.
One thousand 100 kilowatt laser modules and 2000 bounces would be equal to a 200 Gigawatt laser. This would be 4 times the 10 kg system and could deliver 40kg payloads to Mars in ten days. Ten thousand modules would allow for 400 kg payloads to Mars in ten days.
A twenty ton vehicle could be sent to Mars in 96 days using two 1 GW laser source and 1000 reflections. The sail would have an areal density of 10 gm/m**2. For a sail with a 1000 m diameter the resulting total weight would be 7850 kg, within the weight budget of the 20 tonne lightsail craft. The example has a lightsail with a mass of 10 tonne, carrying 10 tonne of cargo.
An equivalent modular system would need ten thousand 100 kilowatt laser modules and 2000 reflections.
The infrastructure for many thousand laser modules is substantial but not impossible in the range of several billion dollars. The cost of the electricity for each launch to Mars is:
Where P is the laser power of 1×10**9 W, the total time the lasers run, t, is 20 hours, and h is the wall-plug efficiency of the laser, which for purposes of this example will be assumed to be 25%. Under these conditions the total energy requirement becomes 8×10**7 kW-hr. The cost of producing electricity in the US is currently on the order of $0.03/kW-hr, which would result in a total power cost of $2.4 million, or only $240/kg for the delivered cargo.