MidSTAR-1 uses passive thermal control by design; for simplicity, no active thermal control devices will be installed on the spacecraft. Likewise, no attitude control will be present and, therefore, solar/earth illumination will be chaotic and unpredictable. Temperature extremes will be tempered by the huge thermal mass (85 kg Al) but the limits of this passive restraint are TBD. As a result, payloads are not guaranteed any specific thermal conditions. No MLI is included in the current design. If indicated by the thermal analysis, minor thermal remediation efforts (e.g. add MLI; attach conductive paths to hot spots, etc.) will be undertaken where possible.

The MidSTAR-1 thermal environment is currently being modeled using the Thermal Radiation Analyzer System (TRASYS) and the Systems Improved Numerical Differencing Analyzer v. 2.4 (SINDA-85) programs, provided by the Naval Research Laboratory. The models are executed on Compaq Visual Fortran under the Windows XP operating system.

“TRASYS is a modularized computer program system design for computing the total thermal radiation environment for a spacecraft in orbit. The principal end products are the radiation conductors and total heating as a function of time or averaged. The output is a lumped parameter nodal representation formatted for direct interface with a thermal analyzer. The radiation conductors account for the radiation interchange between a network of nodes that make up the geometric model defined by the user. The radiation interchange includes the direct contribution from the sun, albedo, and planet, plus the intra-network reflections of this energy.” (Thermal Radiation Analyzer System (TRASYS) User’s Manual (JSC-22964)(LEMSCO-22641), Lockheed Engineering and Management Services Company, Houston TX, April 1988; Abstract, p. i)

The TRASYS model (JPEG) (DWG) of MidSTAR-1 is an octagonal cylinder 30 inches tall and 26.5 inches tip-to-tip.  MidSTAR TRASYS Model version 1.1 uses the radiative properties of bare aluminum for all surfaces. Subsequent versions will use the actual radiative properties of the spacecraft surface materials. The bulk of the cylinder sides will be covered with Gallium Arsenide solar cells under cover glass. Exposed aluminum surfaces will be anodized or allodized. Multi-layer insulation (MLI) is currently not included in the design; it will be added if dictated by thermal analysis results and modified models will then be constructed and analyzed. 

 “SINDA is a software system suited for solving lumped parameter representations of physical problems governed by diffusion-type equations. The system was originally designed as a general thermal analyzer that utilizes resistor-capacitor (R-C) network representations of thermal systems: although, with due attention to units and thermally oriented peculiarities, SINDA will accept R-C networks representing other types of systems.”(SINDA/FLUINT Version 2.4 User’s Manual, Martin Marietta Astronautics Group, Denver CO, December 1991; Foreword, p. iii)

The SINDA model (JPEG) (DWG) of MidSTAR-1 is an octagonal cylinder 30 inches tall and 26.5 inches tip-to-tip. MidSTAR SINDA Model version 1.1 includes the exterior shell of the spacecraft only. Subsequent versions will successively add the inner shelves and the on-board systems. The resistors used in the drawings represent the conductive paths of the heat as it flows through and around the spacecraft.

AutoCAD serves as visual support to what is being modeled in TRASYS and SINDA.    These files are view-only files; they allow the user to explore the model in 3-D space, but they have no quantitative worth.