Advanced Solar- and Laser-pushed Lightsail Concepts

Beam-pushed propulsion systems, such as solarlaser-, or microwavepushed sails, allow the possibility of fuel-free propulsion in space. This makes possible missions of extremely high delta=V, potentially as high as 30,000 km/sec (0.1c), which is required for an fly-by mission to a nearby star. This project analyzed the potential use of dielectric thin films for solar and laser sails. The advantages are extremely light weight and good high temperature properties, which are necessary for both for solar-sail missions inward toward the sun, for solar sail missions outward from the sun that use a close perihelion pass to build speed, and for high velocity laser-pushed missions for the outer solar system and for interstellar probes. Because of the higher temperature capability, the sails can operate under higher laser illumination levels, and hence achieve higher acceleration. This allows large decreases in the minimum size of the sail required. The project also made an analysis of the possibility of microwave-pushed sail propulsion. Microwave sails have the advantage that high-power microwave sources are already existing technology. The study made a new re-analysis of a concept proposed by Robert Forward, and found that a carbon mesh sail is preferable to the aluminum sail proposed by Forward, due to better high-temperature properties. Beam propulsion concepts can be used for lower delta-V missions as well. Candidate missions include fast-transit missions to the outer planets, Kuiper and Oort cloud missions, and interstellar precursor missions. The preliminary analysis indicates that the power required for an interstellar mission using a laser-pushed lightsail could be reduced to 448 MW by the use of a dielectric sail. This is a considerable reduction from the 65 GW required for the baseline mission. It makes the power requirement for the interstellar mission an amount that can be achieved in the reasonable future, and not an unreasonable amount which would require nearly a hundred dedicated electrical power plants. Figure 1: conceptual view of a beam-pushed interstellar probe 1.0 INTRODUCTION Envision a future of space exploration, featuring featherweight microprobes on iridescent sails, tiny vehicles sailing on solar power with trip times of a few weeks to Mars or Venus-a month to Jupiter-with the assistance of a laser push, trip times of a month or so to the outer planets and Pluto. Exploration of the Oort cloud and the fringes of interstellar space would be possible in only a year's travel time, and probes to the nearest stars, traveling at 10% of the speed of light, would return images of planets not generations later, but well within the lifetime of the people who launched them Advanced solarand laser-pushed lightsail concepts [figure 1] will be as a starting point for the development of revolutionary capabilities in spaceflight, with the potential for leaping well past the current technology to enable and expand the vision of NASA's long-range strategic plans. Examining the challenges directed to advanced concepts, solar and laser-pushed lightsails will expand our capabilities by allowing us to directly address the following grand challenges: ■ Space Science: Help to solve the mysteries of the universe by use of probes which can enter the fringes of interstellar space with a short flight time, allowing probes to a thousand astronomical units and ten thousand astronomical units to expand our knowledge of the interstellar medium, the heliopause, and make parallax measurements of the distances to every star and object of interest in the galaxy. ■Exploration of the solar system: A propulsion system which will conduct comprehensive exploration of the entire solar system (including beyond the planets) with micro-sized laserand solar-sail propelled vehicles. ■Exploration beyond the solar system:: Laser-pushed systems for future exploration, to observe planets around other stars directly and identify which, if any, may be Earthlike. ■Search for life beyond Earth. Search for life on planets of other stars by interstellar fly-by probes ■Revolutionize our access to space. Lightsails could be a means to deliver payloads on rendezvous missions to the outer planets within a ten-year mission time frame-in fact, with a one-year or less travel time-and to go beyond our solar system to interstellar distances well within a fifty-year horizon. A space propulsion system capable of continuous laser-pushed thrust to achieve very high speed, one that does not rely on an on-board propulsion system.