NASA Debris Assessment Software (DAS) version 3.2.4 (4 April 2023) ====================================================================== https://orbitaldebris.jsc.nasa.gov/mitigation/das.html Version 3.2.4 provides upgrades for the user-defined material model in the reentry modules, a new project file upgrader for improved backwards compatibility, and a new file format for solar flux tables. Installation ------------------------------------------- - Download and run the new DAS installer. -- DAS is optimized for Windows 10. -- DAS must be installed in a location to which the user has both read and write permissions. - The default installation type for DAS is for the "Current User" only. If the user needs to install DAS for "All Users", then the installer must be run as Administrator (Right-click on installer file, select "Run as Administrator") to avoid any run-time errors or crashes. - If necessary, download the latest update of the solar flux data file from the DAS web page and replace the version in the DAS data\ folder. - The orbital debris population files needed for ORDEM runs for the years 2016-2030 are included with the installer. To analyze the debris flux on a spacecraft of rocket body for years 2031 or beyond, users must download the additional ZIP files included in the Software Catalog and extract them into the /data/ folder where DAS was installed. Changes and fixes in DAS 3.2.4 (2023-04-04) ------------------------------------------- 1. Added ability to use linearly-varying specific heat and emissivity for user-defined materials in Req. 4.7-1 assessments and the reentry survivability Science and Engineering utility 2. Upgraded Fortran routines to F95 standard 3. Improved PMD "suggested altitude" routines 4. Improved contour calculations for Science and Engineering utilities 5. Added project file upgrader to automatically convert old DAS projects to v3.2.4 standard format (i.e., number and name of columns) 6. Removed "delete after run" feature for Req. 4.5-1 and 4.5-2 7. Removed "fail early" feature for missions with multiple payloads; if one of the payloads fails Req. 4.5-1 or 4.5-2, the others will still run 8. Fixed bug where ORDEMext model was not called at the correct intervals during Req. 4.6-3 assessment (long term reentry) 9. Fixed assessment for MEO objects with PMD orbit lying entirely within SSO region (20182 +/- 300km altitude) Changes and fixes in DAS 3.2.3 (2022-09-08) ------------------------------------------- 1. Fixed bug where DAS would enter an infinite loop when analyzing certain Graphite Epoxy 1 or Graphite Epoxy 2 components. Changes and fixes in DAS 3.2.2 (2022-07-20) ------------------------------------------- 1. Fixed bug where DAS crashed when project folder path contained spaces when running Requirement 4.5-1 or 4.5-2 assessments. 2. Added temperature-varying specific heats 3. Added temperature-varying emissivity values 4. Updated drag and heating models for cylinders and flat plates 5. Updated timestep from 2 days to 1 day in internal orbit propagators Changes and fixes in DAS 3.2.1 (2022-02-28) ------------------------------------------- 1. Updated ORDEM files to version 3.2. Changes and fixes in DAS 3.2 (2021-12-03) ------------------------------------------- 1. Added long-term reentry option for postmission disposal 2. Updated requirement 4.6 to align with new Standard 8719.14 Revision C. 3. Corrected inclination for rocket body reentries 4. Corrected error in atmospheric density calculation in PROP3D Changes and fixes in DAS 3.1.2 (2021-01-27) ------------------------------------------- 1. Fixed erroneous 'incomplete' result returned when 4.5-1 flux exceeded 0.001 Changes and fixes in DAS 3.1.1 (2020-12-31) ------------------------------------------- 1. Added error handling for users with ORDEM 3.1.0 installed -(DAS 3.1 uses ORDEM 3.1.2) 2. Fixed errors where DAS would sometimes crash when adding lines to a grid. 3. Added limits to Cross-Sectional Area tool number of facets and additional guards in backend code to prevent memory leaks. 4. Fixed error where DAS would sometimes crash when cancelling ORDEM run. Changes and fixes in DAS 3.1 (2020-04-30) ------------------------------------------- 1. Updated the orbital debris environment model from ORDEM 3.0 to ORDEM 3.1. 2. Removed calls to obsolete Gruen meteoroid flux model from the assessment of small-object penetration probability (Req. 4.5-2). - Probability of small-object penetration must be assessed outside DAS at this time. 3. Fixed logic error in Fortran subroutine that produced invalid probability of collision calculation for Requirement 4.5-1 under certain conditions of launch date, mission duration, and PMD. 4. Fixed a bug in the cross-sectional area estimation tool that caused the tool to fail for large inputs. 5. Minor readability and usability changes to the GUI and Help system. Changes and fixes in DAS 3.0.1 (2020-01-31) ------------------------------------------- 1. Fixed two issues that prevented the GUI from saving and using new data in GUI grid boxes. Now the "Run" and "Save" buttons record the new data, save it to the project files, and pass it to the computational routines. 2. Fixed a multi-thread memory limit that caused DAS to crash on certain PC configurations. Changes and fixes in DAS 3.0 (2019-02-01) ------------------------------------------- 1. Improved support for Microsoft Windows 10. 2. Updated the Help files to current format. 3. Updated assessment to address the revised NASA Standard 8719.14B. - New MEO protection zone, removed limit on operational lifetime. 4. Updated reentry material model to reflect recent research. - Increased survivability of carbon-fiber material. 5. Increased number of unique hardware components that can be modeled in the reentry survivability module from 200 to 1500. 6. Removed assessment of intentional breakups: There has been no demand for assessment of this discouraged practice, and cases that can be well predicted are so narrowly defined as to be useless to the general user. 7. Removed assessment of tether systems: Due to the complicated dynamics of tether systems, cases that can be well predicted are so narrowly defined as to be useless to the general user. 8. Removed ORDEM-intensive Science & Engineering Tools: Run-times of days to weeks made several of the tools impractical at this time. 9. Updated User’s Guide with expanded technical appendices and references to latest NASA Standard 8719.14B. Changes and fixes in DAS 2.1.1 (2017-01-18) ------------------------------------------- 1. Fixed logic error in Fortran subroutine that produced invalid probability of collision calculation for Requirement 4.5-1. 2. Updated Help file to reflect version 2.1.1. Changes and fixes in DAS 2.1 (2016-03-31) ------------------------------------------- 1. Updated the orbital debris environment model from ORDEM2000 (a.k.a. ORDEM 2) to ORDEM 3.0. 2. Increased the precision of the cross-sectional area estimation tool. 3. Fixed a typographical error in the list of built-in materials used in reentry survivability calculations. NOTE: Old (DAS 2.0.1, DAS 2.0.2) projects that use the updated materials will need to be updated with the new material names. Old material name New material name ---------------------- ---------------------- Polyamide Polyimide 4. Updated the DAS User's Guide to address the inclusion of ORDEM 3.0 and emphasize the affects and limitations of that change. 5. Updated the software packager/installer (NSIS) and script to be compatible with multi-user Windows machines and with and non- privileged user accounts. Changes and fixes in DAS 2.0.2 (2011-12-01) ------------------------------------------- 1. Fixed a logic error in the ORDEM2000-derived routines that produced incorrect collision risk results for missions that began and/or ended in the second half of a given year. The error was most obvious in missions with short durations. 2. For collision risk assessments, moved the ORDEM sample date to mid- year (except for first and last years) to remove debris flux inconsistencies caused by fractional-year-contribution calculations. 3. Fixed a logic error that caused DAS to skip processing collision risk at altitudes above 2000 km. 4. Fixed a formatting error in the ORDEM2000-derived routines that yielded a bad intermediate file, causing the collision risk assessment to crash at high altitudes. 5. Changed orbit propagator time-step to 2 days. Different modules were using various time-steps, including small steps that could produce singularities in the calculations. 6. Fixed naming and typographical errors in the list of built-in materials used in reentry survivability calculations, and reordered some lines. NOTE: Old (DAS 2.0.1) projects that use the updated materials will need to be updated with the new material names. Old material name New material name ---------------------- ---------------------- Brass- Munthz Brass- Muntz CU/Be (1.9% Beryllium) Cu/Be (1.9% Beryllium) Mag. AZ31 Magnesium AZ31 Mag. HK31A Magnesium HK31A Niobium (columbium) Niobium (Columbium) Polymide Polyamide Stainless Steel 304L Steel AISI 304 Stainless Steel 347L Steel AISI 347 Steel 410 Steel AISI 410 Uzrh Uranium Zirconium Hydride 7. Moved to a new software packager/installer (NSIS) compatible with current Microsoft Windows operating systems (both 32- and 64-bit). 8. Removed an unused input ("Retraction Year") from the GUI for assessment of Requirement 4.8-1. 9. Updated the software User's Guide to reflect the new installation/ removal procedures, and to clearly state the assumptions of the assessment of tethers (Requirement 4.8-1). 10. Included the current solar flux data file, dated 04 April 2012. Changes and fixes in DAS 2.0.1 (2008-02-05) ------------------------------------------- 1. Fixed a bug that resulted in incorrect rocket body mass and A/M data being transferred from the Mission Editor to the assessment routines for Requirements 4.7-1 and 4.8-1. 2. Fixed a bug in the material properties of Nickel and mp35n which resulted in an incorrect specific heat (Cp) value in one temperature range.