字幕列表 影片播放 列印英文字幕 Asteroids impacting Earth can be devastating, just ask the dinosaurs. Oh wait, you can’t because they’re all dead. But even the asteroids that aren’t mass-extinction huge can be a serious threat. We get hit with an asteroid about the size of the Great Pyramid of Giza every few thousand years, and when the next one hits it could cause massive damage to an entire region. So when we spot the next one coming, what’s the plan? Now if it were up to me, plan A would be to train a crew of oil rig drillers led by Bruce Willis and Ben Affleck to be astronauts so they can plant a nuclear bomb inside the murder space rock, splitting it up so its two halves dramatically just miss the Earth... I think that’s a pretty obvious and not at all dumb solution to the problem. But NASA has a whole Planetary Defense Coordination office, whose task is coming up with ways to protect the planet from threats from outer space, and my plan isn’t on that list, somehow. However, one of their ideas is to smack a spacecraft head on with an oncoming asteroid to see if it can be slowed down and deflected. Members of NASA, the European Space Agency, and others are informally collaborating with a pair of missions that together are known as the Asteroid Impact and Deflection Assessment, or AIDA. NASA is up first with a mission called the Double Asteroid Redirection Test, or DART. The launch window opens July 22, 2021, and the goal is to nail an asteroid by late September or early October the following year. The target DART is aiming at is one of a pair of binary asteroids called Didymos B. Didymos is Greek for twin, hence the Double part of DART. While it’s not on a trajectory to hit Earth, it is an ideal candidate to see just how much of an impact will affect it. That’s because Didymos B is a moonlet 160 meters across that’s orbiting the much larger asteroid Didymos A, and as luck would have it, from our perspective it passes in front and behind the larger body, causing changes in the system’s brightness that we can measure. When DART hits Didymos B at 6.6 kilometers per second, the asteroid’s speed will change by a fraction of a percent, but that’s enough to change the time it takes to orbit Didymos A by several minutes. Enough to be detected by telescopes roughly 11 million kilometers away here on Earth. Just because DART’s fate is to go out in a dusty blaze of glory doesn’t mean that any old spacecraft will do. It’s not like we’re flinging a rusty tow truck at Didymos. No, the DART spacecraft will be equipped with the latest in ion engines, NASA’s NEXT-C, and rollout solar panels to power the electric propulsion system. It will also use an autonomous guidance system called SMART Nav that will use the spacecraft’s onboard camera to identify its target and steer DART in for a nearly head-on collision. Huh.. an electric powered self driving vehicle is getting launched into space. Why am I having Deja Vu? About five days before impact, DART will release an Italian-made CubeSat that will record images of the collision, basically a high tech space version of the guy who records you on his phone right before you’re about to do something dumb and hurt yourself and become a gif on the internet. If all goes as planned, the second part of AIDA, the ESA’s Hera mission, will launch in 2023, arriving at Didymos a few years later to take more detailed measurements of DART’s impact on the moonlet. While Didymos can be seen by Earth’s telescopes, DART might kick up dust that makes seeing its effect more difficult. So Hera will use data from visual, lasar, and radio science mapping that will make DART go from an ambitious experiment to a repeatable planetary defense technique. AIDA is the first step in the process towards having a viable defense for planet Earth in case we spot the next disasteroid heading our way. It’s not only a way to test the technology needed to hit a moving target in space, it will also foster cooperation between members of different space agencies. Teamwork is crucial when the world is at stake. Here’s hoping DART hits its mark, then finally the dinosaurs will be avenged. Didymos B has a cute little nickname, Didymoon. Fun fact, that’s also my rap name. If you want to learn more about asteroids, check out this video on NASA’s Psyche mission that’s headed to a metal asteroid. Make sure you subscribe to Seeker to keep up to date will all your space news, and as always, thanks for watching.
B2 中高級 美國宇航局計劃將航天器撞向小行星。 (NASA Plans to Slam a Spacecraft Into an Asteroid) 2 0 林宜悉 發佈於 2021 年 01 月 14 日 更多分享 分享 收藏 回報 影片單字