SHIELDING PROBLEMS IN MANNED SPACE VEHICLES. Semiannual Technical Summary Report for Period December 31, 1959-June 30, 1960

Technical Report · Tue Oct 31 04:00:00 EST 1961

OSTI ID:4120346

Allen, R I; Dessler, A J; Perkins, J F; Price, H C

Results are presented from the first phase of a study of the shielding requirements for manned space vehicles, as imposed by the natural radiations to be encountered in space flight and the radiations from auxiliary nuclear power sources. The penetrating radiations in space are discussed and the reliability of various data is considered. Initensity, energy spectra, and spatial and time dependence of the various types of radiation are summarized in graphical and tabular form. The spatial distribution of trapped protons and electrons is presented in the form of contours of constant flux. The significance and general shielding implications of the more important penetrating radiations are treated. Computational methods for predicting dose rates due to trapped protons and electrons are formulated, and results of calculations are presented. Proton dose- rate calculations are based on the energy spectrum as determined by Freden and White; bremsstrahlung dose rates are calculated on the basis of the low-altitude electron spectrum measurements of Walt et al., and of Holly and Johnson. It is found that attenuation of protons in shields of moderate thickness is governed largely by ionization energy losses; whereas inelastic nuclear collisions result in attenuation of the primary flux of protons and in the production of secondary radiations, which become significant for very thick shields. Proton dose rates at the center of the proton belt range from 20 rads/hr behind a 2 g/cm/sup 2/ shield to about 1 rad/hr behind a 100 g/cm/sup 2/ carbon shield. Light elements are most effective for proton shields since they offer combined advantages of large stopping power and relatively small production of low-energy secondary radiation. Carbon is a particularly effective element for proton shielding; its stopping power is exceeded only by that of hydrogen and helium. Hydrogenous compounds may prove to be suitable since the stopping power of hydrogen is more than twice that of any other element; and such compounds offer advantages of attenuation of both protons and secondary neutrons by nuclear collisions. Production of bremsstrahlung by electrons stopped in the vehicle exterior can be minimized by use of a thin outer layer of low-Z material. Bremsstrahlung dose rates in a lightly shielded vehicle reach values of several r/hr but are reduced to acceptable levels by 3 or 4 g/cm/sup 2/ of lead or uranium. ( auth)

• Research Organization: Lockheed Nuclear Products, Marietta, Ga.
• NSA Number: NSA-15-006979
• OSTI ID: 4120346
• Report Number(s): NP-9502; NR-104
• Country of Publication: United States
• Language: English

Related Subjects

BREMSSTRAHLUNG
CARBON
COLLISIONS
COMPUTERS
DISTRIBUTION
ELECTRONS
ENERGY
HELIUM
HYDROGEN
IONIZATION
LEAD
PERSONNEL
PHYSICS
PROTONS
RADIATION BELTS
RADIATION DOSES
RADIATION SOURCES
SHIELDING
SLOWDOWN
SPACE FLIGHT
SPACE VEHICLES
SPECTRA
URANIUM
USES