We present results of computer simulations of the launch through the atmosphere of a cone-shaped flyer which demonstrate that laser ablation rockets, using a 1MW ground-based laser, can lift 6kg payloads into low earth orbit. We discuss optimization of delivered mass, mass ratio and energy cost.

Approximately ideal flight paths to low-Earth orbit (LEO) are illustrated for laser-driven flights using a 1-MW Earth-based laser, as well as sensitivity to variations from the optima. Different optima for ablation plasma exhaust velocity VE, specific ablation energy Q*, and related quantities such as momentum coupling coefficient Cm and the pulsed or CW laser intensity are found depending upon whether it is desired to maximize mass m delivered to LEO, maximize the ratio m/M of orbit to ground mass, or minimize cost in energy per gram delivered. A notional, cone-shaped flyer is illustrated to provide a substrate for the discussion and flight simulations. Our flyer design conceptually and physically separates functions of light collection, light concentration on the ablator, and steering. All flights begin from an elevated platform. Flight simulations use a detailed model of the atmosphere and appropriate drag coefficients for sub- and supersonic flight in the continuum and molecular flow regimes. A 6.2-kg payload is delivered to LEO from an initial altitude of 35 km with launch efficiencies approaching vacuum values of about 100 kJ/g.

Nearly 200,000 pieces of debris in the 1 - 20 cm range in low- Earth orbit (LEO), a legacy of 35 years of spaceflight now threaten long-term space missions. An economical solution to the problem is to use a ground-based laser to create a photoablation jet on the objects and cause them to re-enter the atmosphere and burn up. A sensitive optical detector is required to locate objects as small as 1 cm at 1500 km range. Applied when the object is rising and between about 45 and 15- degree zenith angle, the necessary (Delta) v is of order 100 m/s. A laser of 30 kW average power at 5-ns pulsewidth and a 4 - 6 m mirror with adaptive optics can clear near-Earth space of the 1-20-cm debris in 2 years of operation. A high altitude site minimizes turbulence correction, interference from nonlinear optical effects, and absorption. We discuss the effect of nonlinear optical processes in the atmosphere as boundaries on propagation, and how to choose system parameters to guarantee optimum conversion of laser energy to target momentum. The laser might be Nd:glass (1.06 micrometer/530 nm), or iodine (1.3 micrometer).