{"680685":{"#nid":"680685","#data":{"type":"news","title":"AE Professor Masatoshi Hirabayashi Studies Compelling Way to Deflect Asteroids From Earth","body":[{"value":"\u003Cp\u003ESmall rocks and debris fly near Earth, many just passing by. Some, however, come too close to Earth, with a potential threat of collision. Defending Earth from these unwanted objects is a growing concern globally. Planetary defense explores threat characterization, risk mitigation, and policy to defend Earth. One mitigation approach is sending an impactor to collide with the target object to deflect its trajectory from the original course toward Earth. This approach, known as kinetic deflection, is practical for intruders with a diameter up to a few hundred meters.\u003C\/p\u003E\u003Cp\u003E\u003Ca href=\u0022https:\/\/science.nasa.gov\/mission\/dart\/\u0022\u003E\u003Cstrong\u003ENASA\u2019s Double Asteroid Redirection Test (DART),\u003C\/strong\u003E\u003C\/a\u003E led by Johns Hopkins University\u2019s Applied Physics Laboratory, was the first full-scale kinetic deflection mission to test how kinetic deflection could effectively push an asteroid measuring 150 meters in diameter. The 580-kg spacecraft (impactor) collided with the target asteroid, Dimorphos, at a speed of 6.1 km\/second on September 26, 2022, making the target\u2019s speed 2.7 mm\/s. This speed change could gradually make the course deviate from the original one. The more time that elapses after impact, the further it moves away from the Earth. Even though Dimorphos was not a threat before the impact, it was chosen as a test target for DART\u2019s kinetic deflection test.\u003C\/p\u003E\u003Cp\u003EGeorgia Tech Professor \u003Ca href=\u0022https:\/\/ae.gatech.edu\/directory\/person\/masatoshi-toshi-hirabayashi\u0022\u003E\u003Cstrong\u003EMasatoshi Hirabayashi\u2019s\u003C\/strong\u003E\u003C\/a\u003E critical contribution to DART was recently published in \u003Cem\u003ENature Communications\u003C\/em\u003E. The study, \u201c\u003Ca href=\u0022https:\/\/www.nature.com\/articles\/s41467-025-56010-w\u0022\u003E\u003Cstrong\u003EElliptical ejecta of asteroid Dimorphos is due to its surface curvature\u003C\/strong\u003E\u003C\/a\u003E\u201d analyzed the behavior of fragments coming out by the high-speed DART impact and their push of the asteroid. This work was in collaboration with Professor \u003Cstrong\u003EFabio Ferrari\u003C\/strong\u003E from Politecnico di Milano, who jointly published the study, \u201c\u003Ca href=\u0022https:\/\/www.nature.com\/articles\/s41467-025-56551-0\u0022\u003E\u003Cstrong\u003EMorphology of ejecta features from the impact on asteroid Dimorphos.\u201d\u003C\/strong\u003E\u003C\/a\u003E \u0026nbsp;\u003C\/p\u003E\u003Cp\u003EImagine a cannonball flying through the air and hitting a concrete wall. The wall shutters and fragmented pieces disperse at high speeds. Those smaller fragments, called ejecta, are known to be a key factor in controlling the asteroid push.\u003C\/p\u003E\u003Cp\u003EThe study found that the ejecta from the impact site on Dimorphos highly depends on the asteroid\u2019s shape. As a rule of thumb, a cannonball hitting a flat concrete wall creates ejecta departing from the wall at an angle of about 45 degrees from the wall\u2019s surface. The cloud of ejecta thus looks like a waffle cone. However, if the concrete wall\u2019s surface is tilted against the impact direction, the fragment ejection changes, making the ejecta structure differ even if the impactor has the same mass and speed.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u201cThis changes the asteroid push dramatically. Dimorphos has a squashed round shape, like an M\u0026amp;M,\u201d Hirabayashi explained, \u201cIf the impact is large, more ejecta fly out of the surface but are more affected by surface tilts. This process makes the ejecta deviate from the ideal direction, reducing the asteroid push.\u201d\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EFor the DART impact on Dimorphos, the study identified the impact scale and the asteroid\u2019s rounded surface lowered the asteroid push by 56% compared to when Dimorphos was tested as an entirely flat wall. Thus, sending a large impactor does not mean a big push, and considering how to send impactors strategically is necessary. One way to keep the asteroid push effective is to send multiple small impactors rather than a single large impactor. This way, each small impactor may avoid the target\u2019s rounded shape, and the net asteroid push by multiple impacts can be more efficient than the single impactor.\u003C\/p\u003E\u003Cdiv\u003E\u003Cp\u003E\u201cSending multiple smaller impactors not only results in a higher asteroid push but also potentially saves operational cost and \u0026nbsp;increases tactical flexibility for deflection,\u0022 Hirabayashi said.\u003C\/p\u003E\u003C\/div\u003E\u003Cp\u003EFerrari\u2019s study offered crucial information for Hirabayashi\u2019s conclusions. \u201cWe used Hubble Space Telescope\u2019s images and numerical simulations to quantify a viable mechanism of the ejecta evolution and successfully estimated ejected particles\u2019 mass, velocity, and size. We also found complex interactions of such particles with the asteroid system and solar radiation pressure, i.e., sunlight pushing ejecta particles,\u201d Ferrari said. \u201cDocumenting how ejecta looks over time offers crucial insights into how the DART impact acted on ejecta, giving tight constraints on the target asteroid\u2019s properties.\u201d\u003C\/p\u003E\u003Cp\u003ENASA\u2019s DART mission was a success, and Hirabayashi\u2019s study discovered an innovative approach to kinetic deflection, offering new potential for its future demonstration in space. He is building a new capability of characterizing a target\u2019s properties beneficial for planetary defense, such as mass, size, composition, etc., at limited observational conditions. This is aligned with the fast reconnaissance concept, a new community effort that develops planetary defense strategies to identify these properties within a limited time and resources. This work continues to evolve Georgia Tech into a key player in planetary defense, connecting international communities.\u0026nbsp;\u003Cbr\u003E\u0026nbsp;\u003C\/p\u003E","summary":"","format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EGeorgia Tech Professor \u003Ca href=\u0022https:\/\/ae.gatech.edu\/directory\/person\/masatoshi-toshi-hirabayashi\u0022\u003E\u003Cstrong\u003EMasatoshi Hirabayashi\u2019s\u003C\/strong\u003E\u003C\/a\u003E critical contribution to DART was recently published in \u003Cem\u003ENature Communications\u003C\/em\u003E. The study, \u201c\u003Ca href=\u0022https:\/\/www.nature.com\/articles\/s41467-025-56010-w\u0022\u003E\u003Cstrong\u003EElliptical ejecta of asteroid Dimorphos is due to its surface curvature\u003C\/strong\u003E\u003C\/a\u003E\u201d analyzed the behavior of fragments coming out by the high-speed DART impact and their push of the asteroid. This work was in collaboration with Professor \u003Cstrong\u003EFabio Ferrari\u003C\/strong\u003E from Politecnico di Milano, who jointly published the study, \u201c\u003Ca href=\u0022https:\/\/www.nature.com\/articles\/s41467-025-56551-0\u0022\u003E\u003Cstrong\u003EMorphology of ejecta features from the impact on asteroid Dimorphos.\u201d\u003C\/strong\u003E\u003C\/a\u003E \u0026nbsp;\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"A Georgia Tech study analyzes NASA\u2019s DART mission and proposes an innovative approach for kinetic deflection."}],"uid":"36345","created_gmt":"2025-02-21 19:40:26","changed_gmt":"2025-02-21 19:52:51","author":"gwaddell3","boilerplate_text":"","field_publication":"","field_article_url":"","location":"Atlanta, GA","dateline":{"date":"2025-02-19T00:00:00-05:00","iso_date":"2025-02-19T00:00:00-05:00","tz":"America\/New_York"},"extras":[],"related_links":[{"url":"https:\/\/ae.gatech.edu\/news\/2024\/06\/hirabayashi-chosen-nasa-join-european-space-agencys-planetary-mission-study-results","title":"Hirabayashi Chosen by NASA to Join European Space Agency\u2019s Planetary Mission to Study Results of Asteroid Deflection"},{"url":"https:\/\/ae.gatech.edu\/news\/2022\/11\/aes-third-space-imaging-workshop-creates-hub-imaging-experts","title":"AE\u2019s Third Space Imaging Workshop Creates Hub for Imaging Experts"}],"groups":[{"id":"1188","name":"Research Horizons"},{"id":"1239","name":"School of Aerospace Engineering"}],"categories":[{"id":"136","name":"Aerospace"}],"keywords":[{"id":"1325","name":"aerospace"}],"core_research_areas":[{"id":"193657","name":"Space Research Initiative"}],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EMonique Waddell\u003C\/p\u003E","format":"limited_html"}],"email":["monique.waddell@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}