Accession Number : AD0647694

Title :   PRECURSOR INFRARED RADIATION FROM HYPERVELOCITY ABLATING VEHICLES,

Corporate Author : BALLISTIC RESEARCH LABS ABERDEEN PROVING GROUND MD

Personal Author(s) : Mermagen,William H.

Report Date : SEP 1966

Pagination or Media Count : 102

Abstract : Infrared radiation was observed from the cold, unshocked air as far as thirty body diameters ahead of ablating, hypervelocity vehicles. This precursor radiation is attributed to various constituents of air such as CO2 and H2O, as well as C2 and CN contamination. Resonance radiation due to photon flux absorption from the excited air and ablation products around the vehicles is considered as the dominant mechanism for the production of an infrared precursor. Both wideband and spectrally filtered measurements of the precursor radiation were made. Ablating and non-ablating cylinders and spheres were fired at velocities up to 18,000 feet per sec at ambient pressures of from 20 to 75 Torr. Indium antimonide infrared detectors and photomultiplier tubes were used to observe the precursor radiation. Some approximate theoretical formulas were derived to account for precursor intensities. The firing data are compared with theoretical estimates and fair agreement is observed. The most important contributor to the precursor signal was seen to be water vapor. The effect of ambient carbon dioxide on both precursor and peak radiation was small. The presence of C2 and CN as contaminants in the apparatus was suggested as a result of measurements in the infrared for the C2 Phillips and Ballik-Ramsay systems and the CN red system. (Author)

Descriptors :   (*REENTRY VEHICLES, *INFRARED RADIATION), (*ABLATION, INFRARED RADIATION), (*ATMOSPHERE ENTRY, SIMULATION), HYPERVELOCITY PROJECTILES, GUIDED MISSILES, FLOW FIELDS, LIGHT GAS GUNS, ATMOSPHERE MODELS, CONTAMINATION, INFRARED DETECTORS, AERODYNAMICS

Subject Categories : Guided Missile Dynam, Config & Cntrl Surfaces
      Infrared Detection and Detectors
      Spacecraft Trajectories and Reentry

Distribution Statement : APPROVED FOR PUBLIC RELEASE