1. NAME AND TITLE

BED: Electron Penetration Code for Space Vehicles.

This code package is retained by RSIC to preserve space technology developed in the 1960's.

2. CONTRIBUTORS

NASA Langley Research Center, Hampton, Virginia.

Air Force Weapons Laboratory, Kirtland Air Force Base, New Mexico.

The Boeing Company, Seattle, Washington.

3. CODING LANGUAGE AND COMPUTER

FORTRAN IV; IBM 7090 and 7094.

4. NATURE OF PROBLEM SOLVED

BED computes the space radiation dose produced by electrons being transmitted through a radiation shield.

Required inputs for the code are: electron flux-to-dose conversion table, energy spectrum being used, atomic number of shield material, and layer thickness for solid angle for each sector.

5. METHOD OF SOLUTION

From an empirical study, it is found that electrons from radiation belts encircling the earth will produce a radiation dose equal to the integral over energy of the product of T(E), phi(E), and dE/dx(E) where:

1. T(E) is the transmission of one electron through a shield of thickness x and atomic number z,

2. phi(E) is the energy spectrum from a particular radiation belt, and

3. dE/dx(E) is the ionization loss for an electron of energy E(MeV) of the material for which the dose is calculated.

For each thickness x, the product of T(E), phi(E), and dE/dx(E) is integrated over the range of possible values of E to obtain the dose. If the dose is desired through a particular solid angle of shield, say omega, then the integral is multiplied by omega. The total dose through the shield is then taken to be the sum of the individual doses through particular thicknesses and at various solid angles.

6. RESTRICTIONS OR LIMITATIONS

The mathematical formula for transmission of electrons is derived from theoretical electron Monte Carlo data which is lacking in experimental verification.

The analysis is for one material only, and a shield of more than one kind of material must be treated as though every layer consists of the same material.

7. TYPICAL RUNNING TIME

No study has been made by RSIC as to typical running time. Estimated running time of sample problem: 0.03 hour.

8. COMPUTER HARDWARE REQUIREMENTS

A 32 K computer is required. Code is operable on the IBM 7090 and 7094 with standard I-O equipment.

9. COMPUTER SOFTWARE REQUIREMENTS

The code is operable on the IBM FORTRAN IV IBJOB Monitor within the IBSYS Operating System. Only systems, input, and output tape assignments are made.

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 code and input and output for a sample problem.

12. DATE OF ABSTRACT

January 1968; updated July 1981, February 1985.

KEYWORDS: SPACE RADIATION; ELECTRON; ENVIRONMENTAL DOSE