Ablative Laser Propulsion: Specific Impulse and Thrust Derived from Force Measurements

Specific impulse, thrust, and other dynamic characteristics of solid elemental propellants for ablative laser propulsion are studied experimentally with the aid of a piezoelectric force sensor. This sensor allows direct measurements of applied thrust. Experimental results show that the highest speci...

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Bibliographic Details
Published in:	AIAA journal 2002-11, Vol.40 (11), p.2305-2311
Main Authors:	Pakhomov, Andrew V, Thompson, M. Shane, Swift, Wesley, Gregory, Don A
Format:	Article
Language:	eng
Subjects:	Aircraft Applied sciences Combustion. Flame Energy Energy. Thermal use of fuels Exact sciences and technology Lasers Measurement Miscellaneous Theoretical studies. Data and constants. Metering
Online Access:	Get full text
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Summary:	Specific impulse, thrust, and other dynamic characteristics of solid elemental propellants for ablative laser propulsion are studied experimentally with the aid of a piezoelectric force sensor. This sensor allows direct measurements of applied thrust. Experimental results show that the highest specific impulse, -4.0 x 103 s, occurs for carbon and aluminum, whereas the highest coupling coefficient (8 dyne/W) was observed for lead targets. The ablation time, derived from independent time-of-flight (TOE) experiments and used for the calculation of impulses, was -1.5 mus for the majority of the elements studied. These new measurements confirm a decrease of specific impulse and an increase in thrust with increasing atomic mass of the propellant; the major trend previously determined from TOE experiments. The plasma image analysis also confirms the previously reported angular independence of ion velocity, established after the first 100 ns of plasma life. In previously reported TOE studies, all observations were based on the ionic component ejected from a laser-ablated material. An almost fivefold reduction in the absolute values of the specific impulse was observed in the current effort. This result is attributed to "dilution" of the high specific impulse values for ions by slower atomic neutrals and larger fragments. Among all of the tested elements, aluminum is found to provide the optimum tradeoff for Isp and thrust values.
ISSN:	0001-1452 1533-385X