Ablative Laser Propulsion: Specific Impulse and Thrust Derived from Force Measurements
2002; American Institute of Aeronautics and Astronautics; Volume: 40; Issue: 11 Linguagem: Inglês
10.2514/2.1567
ISSN1533-385X
AutoresAndrew V. Pakhomov, Michael S. Thompson, Wesley Swift, Don A. Gregory,
Tópico(s)Diamond and Carbon-based Materials Research
ResumoSpecie c 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 specie c impulse, » 4:0 ££ 10 3 s, occurs for carbonand aluminum, whereasthehighestcoupling coefe cient (8dyne/W)wasobserved forleadtargets.Theablation time,derived from independenttime-of-e ight (TOF)experimentsand used forthecalculation of impulses, was » 1.5 πs for the majority of the elements studied. These new measurements cone rm a decrease of specie c impulse and an increase in thrust with increasing atomic mass of the propellant; the major trend previously determined from TOF experiments. The plasma image analysis also cone rms the previously reported angular independence of ion velocity, established after the e rst 100 ns of plasma life. In previously reported TOF studies, all observations were based on the ionic component ejected from a laser-ablated material. An almost e vefold reduction in the absolute values of the specie c impulse was observed in the current effort. This result is attributed to “ dilution” of the high specie c 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.
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