The Internal Radiation Environment of Cylindrical Spacecraft

A laboratory study of the shielding against energetic electrons afforded by cylindrical aluminum satellites is reported. The incident electron flux had a near-exponential integral energy distribution with a folding energy of 500 kev over the range: 140 kev to 3.0 Mev. The angle of incidence was isotropic in the plane normal to the cylindrical axis and randomly distributed within an envelope of approximately 55 degrees in the orthogonal plane. The satellite was thus simulated at an erect attitude to the earth' s magnetic field in a region of trapped radiation. Internal spectral flux measurements were made on the axis and at the periphery of cylinders having height-to-diameter ratios from 1:4 to 4:1 with wall thicknesses from 180 mg/cm2 to 900 mg/cm2 in nominal 25-mil steps.