Location
Cocoa Beach, FL
Start Date
5-4-1965 8:00 AM
Description
Illumination of a metallic surface with focused light from a ruby laser has been shown to produce very high density ion emission, the ionized particles being emitted with substantial initial velocities. Ion currents of several amperes and electron current of hundreds of amperes have been obtained from a surface disc less than 0.020" in diameter. Ion velocities have been measured to be over 4 kilometers per second as emitted, and changed very slowly with changes in laser energy applied to the emitter. Estimates of emitter temperature and plasma density together with electrical measurements of currents and voltages indicate a highly ionized plasma. Mass spectrometer measurements verified that only singly charged atoms were being formed and that ionization of the emitter was over 99 percent complete.
These findings suggest that the laser excited emission technique should find favorable application to two types of thrustors. In one type the impulse caused by the relatively high initial velocity of the emitted particles would be used directly; in the second, the high density relatively monoenergetic and highly ionized plasma would be used as an ion or plasma source in an accelerator type thrustors thus obtaining higher ejection velocities and consequent higher values of specific impulse. The experimental results show that thrusts of about 25 millipounds were produced with 196 watts per millipound power consumption. The specific impulse in the direct thrustor example cited was about 600 seconds. When used as an ion source, several amperes of ion current can be obtained at ionization efficiencies of 600 ev per ion when only the laser is used. The energy required for ion production was found to be as low as 30 ev/ion when ionization was enhanced by the external circuit. Thrust and specific impulse in this case are controlled by the accelerating potentials selected for a given engine.
The laser excited emission process is inherently free of standby or warmup power requirements; therefore, the cycling of thrustors using this technique could be predicated exclusively on thrust requirements and on the desired precision of control -without penalty of added power consumption, or equipment malfunction caused by fast cycling.
A program to establish the applicability of the laser stimulated emission technique to thrustors and to obtain data for design and evaluation of such thrustors is currently being performed under NASA contract NAS 3-5919.
Application of the Laser to Electric Propulsion
Cocoa Beach, FL
Illumination of a metallic surface with focused light from a ruby laser has been shown to produce very high density ion emission, the ionized particles being emitted with substantial initial velocities. Ion currents of several amperes and electron current of hundreds of amperes have been obtained from a surface disc less than 0.020" in diameter. Ion velocities have been measured to be over 4 kilometers per second as emitted, and changed very slowly with changes in laser energy applied to the emitter. Estimates of emitter temperature and plasma density together with electrical measurements of currents and voltages indicate a highly ionized plasma. Mass spectrometer measurements verified that only singly charged atoms were being formed and that ionization of the emitter was over 99 percent complete.
These findings suggest that the laser excited emission technique should find favorable application to two types of thrustors. In one type the impulse caused by the relatively high initial velocity of the emitted particles would be used directly; in the second, the high density relatively monoenergetic and highly ionized plasma would be used as an ion or plasma source in an accelerator type thrustors thus obtaining higher ejection velocities and consequent higher values of specific impulse. The experimental results show that thrusts of about 25 millipounds were produced with 196 watts per millipound power consumption. The specific impulse in the direct thrustor example cited was about 600 seconds. When used as an ion source, several amperes of ion current can be obtained at ionization efficiencies of 600 ev per ion when only the laser is used. The energy required for ion production was found to be as low as 30 ev/ion when ionization was enhanced by the external circuit. Thrust and specific impulse in this case are controlled by the accelerating potentials selected for a given engine.
The laser excited emission process is inherently free of standby or warmup power requirements; therefore, the cycling of thrustors using this technique could be predicated exclusively on thrust requirements and on the desired precision of control -without penalty of added power consumption, or equipment malfunction caused by fast cycling.
A program to establish the applicability of the laser stimulated emission technique to thrustors and to obtain data for design and evaluation of such thrustors is currently being performed under NASA contract NAS 3-5919.
