1. NAME AND TITLE

LSVDC4: Space Vehicle Dose Calculation.

AUXILIARY ROUTINES

DIP: Data Input Program.

GEOM: Geometry Processor.

GEOTST: Geometry Data Test Program.

LMFC: Mission Flux Generator (Trapped Radiation).

FLARE: Mission Flux Generator (Solar Flux Events).

LSSC: Source Spectrum Converter.

DOSE: Dose Calculator.

2. CONTRIBUTOR

Lockheed-Georgia Company, Nuclear Analysis Department, Marietta, Georgia.

3. CODING LANGUAGE AND COMPUTER

FORTRAN II, FORTRAN IV AND MAP; IBM 7090 AND 7094 (A); FORTRAN IV; IBM 7090 (B).

4. NATURE OF PROBLEM SOLVED

LSVDC is a computer code system which provides an estimate of proton and alpha particle dose within realistic space vehicle configurations. The DOSE program combines radiation source data and geometric data and calculates proton, alpha, and electron physical doses (or dose rates) at points associated with a geometric configuration. The doses due to proton and alpha induced secondaries are included in the dose estimates. GEOM manipulates geometric data and computes line-of-sight penetration thicknesses and solid angles associated with vectors emanating from a detector point. The resulting data are written on magnetic tape for use by the DOSE code. The GEOTST code provides assistance in determining the validity of the geometric input data by scanning for character and format errors, checking for certain logical inconsistencies, and plotting, off-line, selected cross sections of the geometric representation. LMFC calculates proton and electron flux spectra integrated over trajectories through the trapped radiation belts of earth. Arbitrary trajectories or orbital parameters may be specified. The FLARE code provides a stochastic estimate, at various probability levels, of proton and alpha spectra which arise from solar flux events. LSSC facilitates preparation of proton input spectra for LPPC.

5. METHOD OF SOLUTION

The DOSE program approximates the proton and alpha input spectra with power law representations over the energy range of interest. Analytic solutions of radiation transport through multi-layer shields of diverse materials are evaluated. The electron input spectrum is in tabular form. Shield materials are represented by an equivalent thickness of aluminum for the electron calculation. A transmitted dose is calculated for each input spectrum value; the total electron dose is computed by numerical integration.

GEOM constructs a vector array emanating from each detector point and determines material penetration lengths for each vector associated with a geometric configuration. The number of vectors is determined by input criteria for the maximum solid angle permitted. A configuration is determined by a set of volume elements. A volume element is determined by the surfaces that bound it. Bounding surfaces may include planes, ellipsoids, elliptic cylinders, and elliptic cones with arbitrary attitude and orientation. Volume elements may be noncontiguous, contiguous, overlapped or nested. A volume element need not be simply connected. GEOTST uses the techniques and input data of the GEOM program to plot arbitrary cross sections of the geometric configuration.

LMFC converts geographic coordinates to B-L coordinates and performs logarithmic interpolations in flux maps.

The FLARE code uses Monte Carlo techniques to estimate the occurrence, magnitude, and spectrum of solar flux events over the duration of a mission. An inverse square correction is applied to interplanetary missions.

LSSC converts five types of spectra to spectra differential in energy. Spectra integral in energy are fitted with an approximating function which is differentiated. Spectra integral in rigidity are converted to spectra integral in energy, then treated as described above. Spectra differential in rigidity are converted by transforming from rigidity to energy units. Power law spectra, integral in energy, are differentiated directly.

The DIP code is a subroutine designed to facilitate the preparation of data for acquisition by a calling program (DOSE, GEOM, GEOTST). The routine accepts format free input data and places it in assigned storage locations.

6. RESTRICTIONS OR LIMITATIONS

The codes have fixed dimensions.

7. TYPICAL RUNNING TIME

Each sample case executes in less than two cpu minutes.

8. COMPUTER HARDWARE REQUIREMENTS

All routines were designed to operate on the IBM 7090 and 7094. (The FLARE code was also designed to operate on the IBM 360/50.) The (B) version of the code was developed on the Univac 1108 and tested by RSIC on the IBM 7090.

9. COMPUTER SOFTWARE REQUIREMENTS

The (A) version of this package requires a standard monitor system with a MAP assembler and a FORTRAN II compiler with the exception of the FLARE code which requires the FORTRAN IV compiler. The arithmetic subroutines furnished with this package should be used. The (B) version includes GEOTST, GEOM and DOSE written in FORTRAN IV.

10. REFERENCES

a. Included in documentation:

C. W. Hill, W. B. Ritchie, and K. M. Simpson, Jr., "Data Compilation and Evaluation of Space Shielding Problems, Volume IV, LSVDC4 Program System, "ER-7777 (February 1967).

b. Background information:

C. W. Hill, W. B. Ritchie, and K. M. Simpson, "Data Compilation and Evaluation of Space Shielding Problems, Volume II, Dose Calculations in Space Vehicles," ER-7777 (August 1965).

C. W. Hill, W. B. Ritchie, and K. M. Simpson, Jr., "Data Compilation and Evaluation of Space Shielding Problems, Volume III, Radiation Hazards in Space," ER-7777 (April 1966).

C. W. Hill, C. C. Douglass, Jr., W. B. Ritchie, and K. M. Simpson, Jr., "Computer Programs for Shielding Problems in Manned Space Vehicles," ER-6643 (January 1964).

11. CONTENTS OF CODE PACKAGE

Included is the referenced document in (10.a) and one (1.2MB) DOS diskette on which is written all the source codes and input and output for sample problems.

12. DATE OF ABSTRACT

July 1967; updated July 1981, February 1985, May 1988.