October 2026 critical fixes

Bug 130166: Incorrect fluxes computed for solar and orbital heating requests using the Monte Carlo radiation method due to incorrect beam surface areas and normals

An issue in the Monte Carlo radiation calculation method caused incorrect solar, Earth IR, and albedo fluxes to be computed on beam elements for solar and orbital heating requests.

Solar fluxes were either not written or were incorrectly normalized due to the number of rays not being properly accounted for. Additionally, Earth IR and albedo fluxes were overestimated by approximately 2.5 times because the orientation of beam surfaces relative to the incoming Earth radiation direction was not correctly considered.

These issues have been fixed. As a result, affected models may exhibit changes in computed fluxes and, consequently, temperature results.

Bug 130366: Nodal rotating radius incorrectly detected by user plugins when boundary condition selection includes areas from two different rotations

Fixed versions: 2606.5, 2512.11, and 2506.14

An issue in the thermal solver caused incorrect nodal rotating radius values to be returned through the GetRadius call at nodes shared between regions with different rotational loads, including regions without a rotational load. This could cause user plugins relying on GetRadius to produce incorrect results or encounter errors, potentially affecting computed temperatures.

This issue has been addressed to ensure that the appropriate nodal rotating radius is returned. When multiple rotational loads apply to a shared node, the load with the highest angular velocity is now consistently used.

Bug 130567: Infrared loads are incorrectly reported as zero in per region reports for models with free molecular heating

A defect in the thermal solver caused incorrect heat load values to be reported in per region reports for models with free molecular heating (FMH). The reported orbital loads were inconsistent between models with and without FMH. In particular, the Planet + Rad Sources column incorrectly reported zero when FMH was enabled.

This defect has been corrected to ensure that the orbital loads reported in the Planet + Rad Sources, Albedo + Rad Sources, and Sun columns are consistent regardless of whether FMH is enabled. Additionally, the loads reported in the Other Loads column are now consistent with the FMH loads reported in the MODLF file.

This correction affects only the heat load values in per region reports and has no impact on computed temperature results.

Bug 132134: Incorrect 0D and beam node coordinates used to compute Monte Carlo ray origins can result in inaccurate solar and orbital fluxes and radiative conductances between elements

A bug in the Monte Carlo radiation calculation method caused incorrect ray origins to be used for 0D and beam elements due to overwritten nodal coordinates. This resulted in incorrect ray-blocking calculations and rays intersecting the interior of beam elements, potentially affecting computed solar and orbital fluxes and radiative conductances between elements.

This bug has been fixed to ensure that the correct node coordinates of 0D and beam elements are used to determine ray origins, improving the accuracy of radiation calculations and, consequently, temperature results.

Bug 132323: The thermal solver may produce incorrect results or fail to converge for cyclic symmetry models containing more than 51 instances when radiative rotational periodicity is enabled

A defect in the thermal solver affected cyclic symmetry models containing more than 51 instances when radiative rotational periodicity was enabled. An internal data-reading error caused some radiating elements to remain incorrectly unmerged across periodic instances, resulting in nonphysical temperature values of 0 K and near-zero terms in the solver matrix. This could lead to incorrect temperature results in both serial and parallel runs, as well as divergence in parallel runs.

The defect has been corrected to ensure that all periodic instances are properly processed, resulting in accurate temperature calculations, stable convergence in parallel runs, and consistent results between serial and parallel runs.

Bug 132472: Monte Carlo rays fail to hit the bottom side of non-uniform multilayer shell elements

A bug in the Monte Carlo radiation calculation method caused the bottom side of non-uniform multilayer shell elements to be excluded from ray-tracing intersection calculations. This resulted in incorrect radiative conductances when the affected surfaces were included in a radiation enclosure, potentially affecting computed temperatures.

This bug has been corrected to ensure that both sides of non-uniform multilayer shell elements are properly considered during Monte Carlo ray tracing.