ALBERT

Description: The Jet Propulsion Laboratory Contamination Analysis Program (CAP) is a generalized transient executive analysis computer code which solves realistic mass transport problems in the free molecular flow environment. These transport problems involve mass flux from surface source emission and re-emission, venting, and engine emission. CAP solution capability allows for one-bounce mass reflections if required. CAP was developed to solve thin-film contamination problems in the free molecular flow environment, the intent being to provide a powerful analytic tool for evaluating spacecraft contamination problems. The solution procedure uses an enclosure method based on a lumped-parameter multinodal approach with mass exchange between nodes. Transient solutions are computed by the finite difference Euler method. First-order rate theory is used to represent surface emission and reemission (user care must be taken to insure the problem is appropriate for such behavior), and all surface emission and reflections are assumed diffuse. CAP does not include the effects of post-deposition chemistry or interaction with the ambient atmosphere. CAP reads in a model represented by a multiple-block data stream. CAP allows the user to edit the input data stream and stack sequential editing operations (or cases) in order to make complex changes in behavior (surface temperatures, engine start-up and shut-down, etc.) in a single run if desired. The eight data blocks which make up the input data stream consist of problem control parameters, nodal data (area, temperature, mass, etc.), engine or vent distribution factors (based upon plume definitions), geometric configuration factors (diffuse surface emission), surface capture coefficient tables, source emission rate constant tables, reemission rate constant tables, and partial node to body collapse capability (for deposition rates only). The user must generate this data stream, since neither the problem-specific geometric relationships, the constituents involved, nor plume distribution functions are a part of CAP. Instead, these are used to generate the data stream model CAP solves. Outputs vary from individual deposition rates of exchange, on an internodal basis and on a constituent basis as a function of time, to deposition on each surface on a constituent basis as a function of time. The type of outputs may be user-specified by control parameters. CAP allows the user to select output intervals within the solution interval and to generate restart nodal data blocks. CAP is composed of several FORTRAN subroutines which serve specific functions and can be easily edited. The code is relatively small (2152 statements), and contains comment statements for all operations. It is written in relatively generic FORTRAN to be adaptable to a variety of computers. CAP was implemented on a DEC VAX 11/780 computer, and is distributed on a 9-track DEC VAX BACKUP format magnetic tape. Virtual memory required is 4.6 MB, which corresponds to a 900 node model capacity. CAP was originally developed under contract for NASA/Goddard Space Flight Center in 1979 by JPL, and was subsequently modified as required for project support at JPL. CAP is a copyrighted work with all copyright vested in NASA.