1. NAME AND TITLE
BPPC: Proton Penetration Codes for Space Vehicles.
AUXILIARY ROUTINES
Three codes are included in the proton penetration package:
(A) Secondary Proton Code.
(B) Primary Proton Dose Through Layered Materials.
(C) Proton Spectrum Through Layered Materials.
This code package is retained by RSIC to preserve space technology developed in the 1960s.
2. CONTRIBUTORS
NASA Langley Research Center, Hampton, Virginia.
Nuclear and Space Physics, Aerospace Division, The Boeing Company, Seattle, Washington.
Air Force Weapons Laboratory, Kirtland Air Force Base, New Mexico.
3. CODING LANGUAGE AND COMPUTER
FORTRAN IV; IBM 7090 and 7094.
4. NATURE OF PROBLEM SOLVED
The proton penetration program was developed to predict radiation doses encountered in space missions. It may be used to determine the optimum vehicle structure and arrangement of internal equipment to provide maximum radiation shielding. It can determine the dose received by an astronaut at various body points when the vehicle is subjected to the incident radiations of the space environment.
The program calculates the primary proton dose and the dose from secondary protons, neutrons, and gamma rays produced by the interaction of the primary protons with shield materials within spherical multilayered shields.
5. METHOD OF SOLUTION
A straight ahead approximation technique is used in the proton transport. Basically the method of calculation consists of a set procedure for calculating the spectrum as it emerges from a given shield material thickness. In the case of several layers of different types of material, this procedure is repeated until every layer has been traversed. At this point the dose is computed by forming the integral of the flux spectrum multiplied by the energy loss rate over all proton energies. This set of calculations is repeated for each solid angular section of the vehicle, and the weighted sum of these doses is then the total dose at the point of interest.
The procedure used for each type of secondary radiation is basically the same. Each shield layer is divided into a set of thin sublayers. For each sublayer, the spectrum of secondary particles or photons generated in that sublayer is first determined. This spectrum is then attenuated through the remainder of the shield layers to the point of interest or dose point. The spectrum of each radiation from the shield layers is then the sum of the attenuated spectra, originating in each thin sublayer.
6. RESTRICTIONS OR LIMITATIONS
There are several limitations arising from memory storage limitations. These include the following restrictions on array sizes:
(1) Maximum number of materials considered is 12. This is also the restriction on shield layers in any sector.
(2) Maximum number of solid angle sectors is 350.
(3) Not more than 50 points may be given for the proton energy spectrum.
(4) Not more than 10 angles of incidence may be specified.
(5) Only one spectrum may be considered in one computer run.
(6) In the arrays which specify the differential energy spectrum of secondary protons and neutrons as a function of primary proton energy, up to 50 primary energies and 25 secondary energies may be specified. (These arrays have the code symbols XPMULT and XNMULT.)
(7) Only 10 gamma-ray energy points are considered.
In addition to these limits, the program calculates tissue dose only.
7. TYPICAL RUNNING TIME
The time is dependent upon the number of material layers and solid angles, and it is not possible to give a running time for cases in general. However, for sample problem (A) (two material thicknesses and two solid angle sectors) a running time of 0.02 hours was necessary; for that for (B) and (C), 0.01 hours each.
8. COMPUTER HARDWARE REQUIREMENTS
All routines operate on the 32 K IBM 7090 and 7094 computers. Standard input, output, and punch tapes, plus an on-line printer for operator instructions are required.
9. COMPUTER SOFTWARE REQUIREMENTS
The code system can be compiled and executed on the IBM IBJOB Monitor in FORTRAN IV within the IBM IBSYS Operating System.
10. REFERENCES
Included in document:
J. A. Barton, B. W. Mar, G. L. Keister, W. R. Doherty, J. R. Benbrook, W. R. Sheldon, J. R. Thomas, K. Moriyasu and M. C. Wilkinson, "Computer Codes for Space Radiation Environment and Shielding," WL-TDR-64-71, Volume I and II (August 1964).
Background information:
J. A. Barton and G. L. Keister, "Symposium on Space Radiation Environment," D2-90684-1 (April 1965).
11. CONTENTS OF CODE PACKAGE
Included are the referenced documents and one (1.2MB) DOS diskette which contains the source codes and input and output for a sample problem.
12. DATE OF ABSTRACT
January 1968; updated July 1981, February 1985.
KEYWORDS: SPACE RADIATION; PROTON; STRAIGHT-AHEAD