NASA plans giant spacecraft to defend Earth by nuking deadly asteroids
Baku, March 22, AZERTAC
Lawrence Livermore National Laboratory (LLNL) scientists are part of a national planetary defense team that designed a conceptual spacecraft to deflect Earth-bound asteroids and evaluated whether it would be able to nudge a massive asteroid - which has a remote chance to hitting Earth in 2135 - off course. The design and case study are outlined in a paper published recently in Acta Astronautica (link is external), according to Space Daily.com.
The 9-meter-tall, 8.8-ton spacecraft - dubbed HAMMER (Hypervelocity Asteroid Mitigation Mission for Emergency Response vehicle) - features a modular design that would enable it to serve as either a kinetic impactor, essentially a battering ram, or as a transport vehicle for a nuclear device. Its possible mission: deflect 101955 Bennu, a massive asteroid around 500 meters (more than five football fields) in diameter, weighing around 79 billion kilograms (1,664 times as heavy as the Titanic), circling the sun at around 63,000 miles per hour. Based on observation data available, Bennu has a 1 in 2,700-chance of striking Earth on Sept. 25, 2135, and it is estimated that the kinetic energy of this impact would be equivalent to 1,200 megatons (80,000 times the energy of the Hiroshima bomb).
The effort is part of a national planetary defense collaboration between the National Aeronautics and Space Administration (link is external)(NASA) and the National Nuclear Security Administration (link is external) (NNSA), which includes LLNL and Los Alamos National Laboratory. (link is external)(LANL). Of the three prongs of planetary defense, NASA is responsible for the first, detecting asteroids with enough time to mitigate the risk. The LLNL planetary defense team is the technical lead on the second prong, mitigation of the threat. The LLNL team also supports the third prong, emergency response should mitigation fail.
The preferred approach to mitigating an asteroid threat would be to deflect it by ramming a kinetic impactor into it, delivering a gentle nudge large enough and soon enough to slow it down and change its collision course with Earth, but not so large that the object breaks apart. This study helped quantify the threshold where a kinetic impactor would no longer be an effective deflection option. To evaluate this threshold, researchers focused on determining how many HAMMER impactors it would take to deflect Bennu.
If the decision was made to embark on a mission to deflect Bennu, researchers estimate that it would take a minimum of 7.4 years before an impulse could be delivered to the Earth-bound object. This includes the time it would take to build the spacecraft, plan the mission and travel to the object. Assuming the impactor successfully hits the asteroid, slowing it down slightly, it would take many years for the small change in speed to accumulate into a sufficient change in trajectory.
The researchers evaluated a number of deflection scenarios in this study, ranging from launching 10 years before impact to 25 years before. In the 10-year scenarios, it was determined that it could take between 34 and 53 launches of the Delta IV Heavy rocket, each carrying a single HAMMER impactor, to make a Bennu-class asteroid miss the Earth. If there were a 25-year lead time, that number could be reduced to seven to 11 launches. The exact number would depend on the desired Earth-miss-distance and the impact conditions at the asteroid.
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