February 23, 2007

Photonic Laser Propulsion

Photonic Laser Propulsion has had a proof of concept demo it generated 35 micronewtons of thrust using mirrors that generated 3000 times amplification. The low power version would be great for position control of multiple satellites to nanometer precision.

UPDATE: 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. With 47,000 reflections then only a 1MW laser system would be needed. (fifty 20KW lasers). Scaling up 100 times would be able to deliver 1 ton payloads to Mars in ten days.
"Multi-Bounce Laser-Based Sails", written by Robert A. Metzger and Geoffrey Landis


Molecular nanotechnology could help put this technology over the top, with far better mirrors, lighter systems, better lasers, mass production of lasers and other benefits.

The 10 watt laser was based on 100 watts for the total satellite power budget. Thus the best mirrors (20,000 times amplification) would deliver 1.3 milliNewtons.

If they can use the MIT dielectric mirrors those are supposed to reflect 99.999% of the light which would have 100,000 times amplification.

Scaling it up for more power.
130 millinewtons per kilowatt (0.13 N/kw)
But 10 MW lasers would give 1300 newtons.

Continuous beam electric lasers have about 27 kilowatts of power. Although stay on all day lasers seem to be at about 10-13 kilowatts.

more on lasers at wikipedia In some applications you could use more powerful chemically pumped or other types of lasers.

The website for the research group talks about using the system for ground launch and for accelerating to light speed. I could see ground launch.
This PDF looks at another study for using many lasers to ground launch. The mirror system could make such a ground launch system more efficient.

Get a big power source and a very powerful laser(s). As a major propulsion system it would still seem to have issues maintaining targeting between the two mirrors.

Robert forward originally proposed the laser sail concept Robert Forward first proposed the idea of the laser sail, though his ideas used 1000 km lenses, a laser producing 10-million-gigawatts and 1000 km sails.
Geoffrey Landis has done work to advance laser and microwave pushed lightsails
Other laser sail concepts

It would seem that the mirror amplification could be helpful in reducing certain system requirements.

I presume the architecture is to stick the launching system in space where there would not be atmospheric distortion and losses. The mirror on a large asteroid or body without atmosphere and far heavier than the thing being launched. Then firing up the nuclear generator on the asteroid and firing the lasers that bounce between the mirrors. One mirror on the ship and one on the asteroid.

If the problems of making the more powerful lasers, targeting and better mirrors can be overcome. The ISP in the tables for the photonic laser propulsion is 40 million. (between 10**7 and 10**8). This is the highest ISP system that I have seen.
ISP Hours ISP seconds
Photonic drive 11,236 40 million
AM-Beam MAX 2,834 10 million
H->Fe Fusion MAX 1,417 5.1 million
H->He Fusion MAX 850 3.1 million
IC-Fusion MAX 2831 million
ORION MAX 278 1 million
NSWR 90% UTB MAX133 479,000
AIM 17 61200
mag Orion 8.230000
VASIMR (high gear) 8 28800
Mini-Mag Orion 6 21600
ORION Low Altitude414400
Space Shuttle0455

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