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Radioss Reference Guide
This manual provides a detailed list of all the input keywords and options available in Radioss.
Obsolete Keywords
Keywords that are still supported, but no longer maintained (*) are considered obsolete.
Obsolete Engine Keywords
Engine Keyword Keywords that are still supported, but no longer maintained (*) are considered obsolete.
/IMPL/SBCS/ORDER (Obsolete)
Engine Keyword Reordering method definition for BCS.

Welcome
What's New
View new features for Radioss 2026.
Radioss Overview
Radioss is a leading explicit finite element solver for crash and impact simulation.
Tutorials
Discover Radioss functionality with interactive tutorials.
Radioss User Guide
This manual provides details on the features, functionality, and simulation methods available in Altair Radioss.
Radioss Reference Guide
This manual provides a detailed list of all the input keywords and options available in Radioss.
- File Extensions and Formats
  Current Radioss format uses the 12x extension format.
- Single File Input
  This format allows running either Starter or Engine with the same file.
- New Keywords in 2026
  New and modified features in Radioss.
- Starter Input
  This manual provides a list of all the model definition keywords and options available in Radioss.
- Engine Input
  This manual provides a list of all the solution definition keywords and options available in Radioss.
- LS-DYNA Input
  This manual provides a list of LS-DYNA input files available in Radioss.
- Multi-Domain
  This manual contains the description of the keywords for the Radioss Multi-Domain.
- Obsolete Keywords
  Keywords that are still supported, but no longer maintained (*) are considered obsolete.
  - Obsolete Starter Keywords
    Block Format Keyword Keywords that are still supported, but no longer maintained (*) are considered obsolete.
  - Obsolete Engine Keywords
    Engine Keyword Keywords that are still supported, but no longer maintained (*) are considered obsolete.
    - /ALESUB (Obsolete)
      Engine Keyword Subcycling on Lagrangian parts.
    - /ANIM/CUT/1 (Obsolete)
      Engine Keyword Defines a section cut on a deformed geometry.
    - /ANIM/CUT/2 (Obsolete)
      Engine Keyword Defines a section cut on the initial geometry.
    - /ANIM/CUT/3 (Obsolete)
      Engine Keyword Defines a section cut on a deformed geometry using three nodes.
    - /ANIM/KEEPD (Obsolete)
      Engine Keyword In animation files, keep deleted elements in their original part; otherwise group all deleted elements in an extra part (named "deleted elements").
    - /DT/GLOB/Iflag (Obsolete)
      Engine Keyword Global time step estimation, enables setting the time step to a higher value than the usual elementary or nodal time step.
    - /DT/NODA/Keyword3/Iflag (Obsolete)
      Engine Keyword Activates the nodal time step control method with the option to apply mass scaling to increase a model’s time step.
    - /IMPL/DYNA/FSI (Obsolete)
      Engine Keyword Defines the settings for Fluid Structure Interaction Analysis with AcuSolve.
    - /IMPL/SBCS/MSGLV (Obsolete)
      Engine Keyword Describes the message level for BCS (Boeing) solver.
    - /IMPL/SBCS/ORDER (Obsolete)
      Engine Keyword Reordering method definition for BCS.
    - /IMPL/SBCS/OUTCORE (Obsolete)
      Engine Keyword BCS solver will use minimum in-core memory.
    - /INCMP (Obsolete)
      Engine Keyword Quasi-incompressible formulation for fluid material (compatible with /MAT/LAW6 and /MAT/LAW11).
    - /MADYMO (Obsolete)
      Engine Keyword Activates MADYMO- Radioss coupling.
    - /SHVER/V51 (Obsolete)
      Engine Keyword The new large rotational body motion formulation for QEPH, QBAT and DKT18 will be deactivated.
    - /UPWIND (Obsolete)
      Engine Keyword Enables you to modify coefficients for standard upwind formulation previously defined from Starter Input or from previous run.
    - /UPWM/SUPG (Obsolete)
      Engine Keyword This describes the Streamline Upwind Petrov Galerkin formulation.
    - /UPWM/TG (Obsolete)
      Engine Keyword Describes the Taylor Galerkin method for momentum advection. This method is not available with multi-material LAW51 (/MAT/MULTIMAT).
    - /VEL/ALE (Obsolete)
      Engine Keyword With ALE links on grid velocities, given nodes are linked to the given main grid velocities. You can specify direction or a combination of directions.
  - Obsolete Optimization Keywords
    Optimization Keyword Keywords that are still supported, but no longer maintained (*) are considered obsolete.
- Other Files
- Definition
Radioss Example Guide
This manual presents examples solved using Radioss with regard to common problem types.
Radioss Verification Problems
This manual presents solved verification models.
Radioss Frequently Asked Questions
This section provides quick responses to typical and frequently asked questions regarding Radioss.
Radioss Theory Manual
This manual provides detailed information about the theory used in the Altair Radioss Solver.
Radioss User Subroutines
This manual describes the interface between Altair Radioss and user subroutines.

/IMPL/SBCS/ORDER (Obsolete)

Engine Keyword Reordering method definition for BCS.

Format

/IMPL/SBCS/ORDER/n

Definition


Field	Contents	SI Unit Example
`n`	= 0 (Default) Automatic choice between method 1 and method 2 according the matrix size. = 1 Multiple Minimum Degree. = 2 Nested Dissection (Metis).