NASA’s Double Asteroid Redirection Test (DART) vehicle will collide with the asteroid Demorphos on September 26, carrying out the first asteroid deflection test that took years in planning.
Demorphos, which is 150 meters wide, is the “little moon” of a binary asteroid system, orbiting the larger companion asteroid, Didymos (800 meters). The momentum of the 600 kg spacecraft, traveling at about 6 km/s, will cause a small change in velocity to Dimorphos, which will be detectable from ground-based telescopes as a change in the orbital period of the asteroid system.
As part of this mission, Lawrence Livermore National Laboratory (LLNL) researchers have contributed multi-physics simulation expertise to this planetary defense technology pilot mission since 2014, developing new methods for simulating the range of potential asteroid targets and modeling the DART spacecraft using higher resolution.
new paper in Planetary Science Journal“The Effects of Spacecraft Engineering on Kinetic Impact Missions” led by Mike Owen of LLNL, explores the consequences of including realistic spacecraft engineering in a multi-physics simulation.
Previously, most crash designers considered ideal shapes for the DART spacecraft, such as a ball, cube, or disk. The use of detailed computer-aided design (CAD) models provided by spacecraft engineers was not a readily available capability for many impact codes. Owen simplified the process in Spheral, the LLNL-based adaptive smooth particle dynamics (ASPH) code that he created and serves as lead developer. Collaborators across the United States and internationally also worked to implement CAD-based DART architecture, providing software comparisons of both detailed and simplified geometries for spacecraft, as part of the study.
“Over the years, many researchers have done a lot of work studying how kinetic stimuli like DART would perform if we had to shift an asteroid, using both Numerical models and lab experiments,” Owen said. Nearly most of that research focuses on the effects of how different properties of the same asteroid might affect the outcome, but of all the unknowns in these scenarios, perhaps the only factor we know most about is the spacecraft itself, which is generally approximated using a simple solid geometry such as a cube. steel or ball. “
Now that a full-scale live experiment is being conducted on the DART mission, Owen said, it makes sense to consider how important the geometry of the actual spacecraft launched is, especially given how different the spacecraft’s appearance is compared to the typical simplification.
“These realistic models are very challenging to set up and operate, and we had to develop new capabilities in our modeling tools in order to be able to address this problem,” he added.
The geometry of the DART spacecraft, consisting of a vending machine-sized central body (1.8 x 1.9 x 2.3 m) and two 8.5 m solar panels, creates a much larger “footprint” than a solid sphere of aluminum of the same mass. This affects the drilling process and, ultimately, the momentum given to the asteroid, reducing it by about 25%. While this is a measurable effect, uncertainty in the properties of the asteroid’s target can result in larger changes in deflecting effectiveness.
However, full CAD geometry modeling usually requires finer precision, and can be computationally expensive. Owen also explored cylinders of different thicknesses and three-ball approaches to solve the problem, finding a “middle ground” that was easier to simulate but also behaved like a real DART spacecraft. The three-domain model was able to account for most of the full use effect Space ship Engineering. This three-domain simplification enables many DART effect models, across different codes and users, to be run accurately.
“While it might seem counterintuitive that a perfect spherical representation of DART would overestimate the aberration, determining this effect was important for understanding the limitations of previous methods,” said Megan Brooke Seal, LLNL’s Planetary Defense Project Lead. “Conducting this study was a key component of preparing for the DART trial, and it redefined best practices for both LLNL and other impact modeling groups.”
J. Michael Owen et al, Effects of spacecraft engineering on kinetic impact missions, Planetary Science Journal (2022). DOI: 10.3847 / PSJ / ac8932
Lawrence Livermore National Laboratory
the quote: Revealing the effects of spacecraft engineering on the collision simulation of NASA’s DART mission (2022, September 20), retrieved September 20, 2022 from https://phys.org/news/2022-09-revealing-spacecraft-geometry-effects- impact.html
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