> This paper discusses the use of solar system-based lasers to push large lightsail spacecraft over interstellar distances. The laser power system uses a 1000-km-diam. lightweight Fresnel zone lens that is capable of focusing laser light over interstellar distances. A one-way interstellar flyby probe mission uses a 1000 kg (1-metric-ton), 3.6-km-diam. lightsail accelerated at 0.36 m/s2 by a 65-GW laser system to 11% of the speed of light (0.11 c), flying by a Centauri after 40 years of travel. A rendezvous mission uses a 71-metric-ton, 30-km diam. payload sail surrounded by a 710-metric-ton, ring-shaped decelerator sail with a 100-km outer diam. The two are launched together at an acceleration of 0.05 m/s2 by a 7.2-TW laser system until they reach a coast velocity of 0.21 c. As they approach a Centauri, the inner payload sail detaches from the ring sail and turns its reflective surface to face the ring sail. A 26-TW laser beam from the solar system, focused by the Fresnel lens, strikes the heavier ring sail, accelerating it past a Centauri. The curved surface of the ring sail focuses the laser light back onto the payload sail, slowing it to a halt in the a Centauri system after a mission time of 41 years. The third mission uses a three-stage sail for a roundtrip manned exploration of e Eridani at 10.8 light years distance.

Very cool.

This is very interesting. Apparently beam collimation is much less of a show-stopper than I would have assumed.

But I don't see us putting a a 1000 kilometer lens into orbit anytime soon, and that multi-terawatt (sustained!) laser system sounds like a bit of a headache, too...

The Mote in God's Eye

I guess this will be the Niven-Pournelle thread.