High Heat Flux Measurement In An Electrothermal Launcher

The incident high heat fluxes during the operation of electrothermal and electromagnetic launchers my exceed 10
¹⁰
W/m
²
, which causes surface melting and ablation of the launcher components. The experimental facility SIRENS simulates typical heat loading conditions in such devices by exposing material surfaces to heat fluxes in the range between 5x10
⁹
to 4 x 10
¹⁰
W/m
²
over a 100 μsec duration, for input energies 1-5 kJ. The source heat flux may be evaluated via the ablation depth of the source insulator by utilizing an algorithm for the heat flux as a function of the heat of sublimation of the insulator, its exposed area, the exposure time, and the energy transmission factor through the vapor shield layer. The transmission factor is a fraction of the blackbody radiation emitted from the plasma through the vapor shield. An independent heat flux diagnostic has been devised. The temperature increase ΔT of a target material is an indication of the incident heat flux. A thermocouple is connected to the back of copper disk (5 cm diam.) which acts as a target for the plasma emerging from SIRENS. The thermocouple is interfaced to a waveform digitizer and the temperature as a function of time is recorded. A 1-D, time dependent heat conduction code (SURFHEAT) was written to calculate the response of the thermocouple to the incident heat flux. SURFHEAT automatically compares the digitized thermocouple data to calculated profiles to determine the best estimate for the incident heat flux.