The NASA Safety Standard (NSS) 1740.14 requires that each NASA reentering spacecraft and launch vehicle upper stage be assessed as a human casualty risk to the world's population upon impact of all surviving debris to the Earth. As a first approach, the risk is usually evaluated with the slightly conservative NASA Debris Assessment Software (DAS). However, if the DAS assessment of the risk does not meet the NSS guideline of 1:10,000, the higher-fidelity Object Reentry Analysis Survival Tool (ORSAT) might be required. Various versions of this code have been used in the past 10 years to perform over 20 different spacecraft reentry analyses. The object of this paper is to discuss the new features of the latest version - ORSAT 6.0. These features include replacement of the trajectory model and improvement of the gravitational model; incorporation of the GRAM atmosphere and a user-defined atmosphere model; 2-D heating rate and temperature variation around spheres, cylinders, cones, and flat plates; drag coefficients for cones; and general program improvements. Additional improvements include a Graphical User Interface (GUI), gas cap radiation at high entry velocities, recession for non-metallic insulation materials, structural failure of solar array hinges, tank bursting, Unix/Linux plotting scripts, an expanded materials property database, and trajectory mapping on a world map. Sample results are presented for reentry of the Genesis capsule using these updated features in ORSAT.

The two reentry analysis tools, NASA ORSAT (Object Reentry Survival Analysis Tool) and ESA SCARAB (Spacecraft Atmospheric Reentry and Aerothermal Breakup), are standard codes for the reentry survivability assessment of decaying satellites. These programs determine if and when an object/fragment demises during reentry. The final debris casualty area caused by the surviving objects/fragments is calculated, which is used to determine the reentry risk posed to the Earth’s population. A set of test cases for both tools has been defined which comprises random tumbling or spinning simple geometric shapes (spheres, boxes, and cylinders), consisting of three materials (aluminum, titanium, and graphite epoxy composite). Geometric dimensions, wall thickness, and mass are varied, with the initial orbit conditions kept constant for each case. Both tools use the U.S. Standard 1976 atmosphere model and the same physical material properties. This paper presents the main results of both tools and summarizes the discovered differences.