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Next year the Planetary Society plans to launch Cosmos-l, the first solar sail. We are planning an experiment to irradiate the sail with the Deep Space Network beam from Goldstone. This can demonstrate, for the first time, beamed propulsion of a sail in space. The 450 kW microwave beam from the large 70-m dish can show direct microwave beam acceleration of the sail by photon pressure, and we can measure that acceleration by on-board accelerometer telemetry. In addition, we describe a mission scenario called 'Sun-Diver' using a powerful microwave beam on a solar-driven sail, to both heat and push the sail, accelerating by "boil-off" of coated materials. Sublimation and desorption work well with the new carbon sail materials which can take very high temperatures >2000 K), can use promising new materials for mass loss, and promise new classes of missions. These missions make a close pass near the Sun, hence the name, to take advantage of high temperature characteristics of the sail by using the large solar flux at perihelion, yielding high velocities of ∼50 km/s for >40 A.U. missions. Within ∼5 years, the sailcraft flies beyond Pluto, giving high velocity mapping of the outer solar system, the heliopause and interstellar medium. [ABSTRACT FROM AUTHOR]

Solar-driven sails which can also accelerate by "boil off" of coated materials offer new high-velocity missions. These can take advantage of high temperature characteristics of the sail by using the large solar flux at perihelion. For the near term use of beamed power, beam illumination at ∼kW/cm² in LEO can simulate conditions any solar grazer mission will experience to within 0.01 A.U. Sublimation (or desorption) thrust from LEO into interplanetary orbit can omit the several-year orbits conventional solar sails need to reach ∼0.1 AU. A second "burn" at perihelion, the highest available orbital velocity in the inner solar system, and thus optimum point for a delta-V, then yields high velocities of ∼50 km/s for >40 A.U. missions. The mission begins with deployment in Low Earth Orbit by conventional rocket. Then the launch begins, driven by a microwave beam (and much smaller solar photon thrust) from nearby in orbit. Beam heating makes a "paint" (polymer layer #1) desorp from the sail. Under this enhanced thrust, in repeated shots at.perihelion in steepening elliptical orbits, the sail attains ∼15 km/s velocity, canceling most of its solar orbital velocity, and so can fall edge-on toward the sun immediately. (This is far faster than using solar pressure to spiral down, which takes years.) It approaches the sun edge-on, to minimize radiation pressure on it in the inward fall. At perihelion the spacecraft rotates to face the sun. Under intense sunlight ∼20 times Earth insolation, the sail desorps away polymer #2, getting a ∼50 km/s boost at its maximum (infall) velocity. It then sails away as a conventional, reflecting solar sail, with the final Aluminum layer revealed. Its final speed is after leaving the solar potential well is ∼ 10 AU/year. Within ∼5 years, it sails beyond Pluto, giving high velocity mapping of the outer solar system, the heliopause and interstellar medium. [ABSTRACT FROM AUTHOR]

Stability is a neglected issue in concepts for propelling ultralight sails by beamed power. Whether the beam comes from a laser or a microwave antenna, power falls with angle from the beam center. This drives a sail sideways under any lateral perturbation—"tumbling down the hill." The basic mechanics of pressures and sail averaging of them across its area remain unexplored in experiment, and have only recently been treated in theory. Here we report the first experiments on beam-riding dynamics in the laboratory, using a slightly over-weighted pendulum. In the experiments, a sail attached to the pendulum bottom is made unstable by adding weight to the top end. Sail stability and oscillation are possible if this is countered by electrodynamic beam pressure on the sail, directed from below, torquing the pendulum into a stable state. We present both data and analysis that shows that the beam-riding effect does in fact occur: microwave powers of a few hundred W can hold an otherwise unstable sail steady. This is made possible because of the gradient in beam power with sidewise angle. Our experiments verify the University of New Mexico simulations, which show similar stability conditions. Beam powers comparable to the strength of perturbing forces can plausibly achieve these stability effects in free sail flight. [ABSTRACT FROM AUTHOR]

Unfurling and deployment of large-area, membrane structures in space is essential for many NASA purposes, such as large ultralight antennas and mirrors, occulters, collectors for SPS, and sailcraft for deep space exploration. Deployment is a complicated electromechanical problem, exacerbated by the difficulty and expense of realistic lab or space experiments. The requirement is to open and control very light but very large structures with a minimum of mechanical contact ('hands-off'), deployed from a minimum stowed volume (maximum packing fraction), while providing for control after deployment. We report here on a project that addresses deployment of carbon and other light materials by use of spin, charge and elastic forces. Last year we demonstrated microwave-driven spin of several types of sail by using polarized microwaves at JPL. In the first phase, we conducted experiments to study microwave beam-driven spin deployment, simulating this deployment and its extension to large structures in space. We will determine how efficiently spin forces couple to sail materials, what geometric shapes and material factors influence this electrodynamic efficiency, and develop analytical scaling rules for spin unfurling. This work is conducted under the Gossamer Program. [ABSTRACT FROM AUTHOR]

We have observed flight of ultralight sails of Carbon-Carbon microtruss material at several gees acceleration. To propel the material we sent a 10 kW, 7 GHz beam into a 10[sup -6] Torr vacuum chamber and onto sails of mass density 510 g/m[sup 2]. At microwave power densities of ∼kW/cm[sup 2] we saw upward accelerations of several gees and flights of up to 60 cm. Sails so accelerated reached >2000 K from microwave absorption, a capability of carbon which rules out most materials for high acceleration missions. Diagnostics were optical and IR video photography, reflected microwave power and residual gas analysis. Data analysis and comparison with candidate acceleration mechanisms shows that photonic pressure can account for 3 to 30% of the observed acceleration, so another cause must be present. Future research will measure the thrust precisely using a pendulum to try to identify the acceleration mechanism. In the future, microwavedriven acceleration might be used to propel probes to very high speeds for science missions to the outer solar system, the interstellar region and the nearby stars. [ABSTRACT FROM AUTHOR]