Science News I’ve been Following Closely – The return of the Hayabusa2 space craft to Earth. Launched by the Japanese Space Agency JAXA in 2010, the Hayabusa2 is establishing itself as one of humanity’s most impressive technological achievements in space. The space craft was sent from earth in 2014. Since then, it has orbited the sun with us, deviating its course ever so slightly from ours, so that it could catch up to an asteroid. The asteroid is named 162173 Ryugu, and it is of special interest to researchers since it is expected to be an exceedingly old piece of rock, remaining unchanged since the formation of our solar system.
Hayabusa2 shadowed the astroid for over a year. In that time, it mapped every corner of the astroid with impressively clear photography, and it dropped an incredibly engineered box on the surface of the asteroid, which collected all manner of data, from information on the asteroids magnetic field, to close up photos, such as the one bellow. This box even had a mechanism by which, with a swinging weight inside of it, the box could hop around the surface of the asteroid to collected data from a variety of locations.
The craft did more than just that. It dropped a payload, which detonated on the surface of the asteroid, creating a crater. After this bombing run, the Hayabusa2 descended onto the surface, and with a probe extended, it dug into the crater, and collected a sample of the asteroid’s innards.
After departing from the Ryugu near the end of 2019, the Hayabusa2 has been on a trajectory to drop off the materials collected by the probe. One hundred milligrams of asteroid rock, locked in a small metal capsule, will arrive on earth in December of 2020. It doesn’t sound like much, but it is nearly ten thousand times more than any other mission has brought back before (the first time being Hayabusa1, which because of an error, could only deliver micro grams).
As you might know, the speed of objects coming at earth from space, combined with the friction caused by the Earth’s atmosphere. usually results in the incineration of the object. Most objects the size of the Hayabusa2 earthbound capsule would not survive the transition from solar system speeds to Earth speeds, but this capsule is another incredible piece of engineering. It will use an ablative heat shield to dissipate the heat caused by friction with the atmosphere.
Ablative shields are very simple, and very interesting. The best way to explain an ablative heat shield is to compare it to a traditional lead pencil, like those you used in school. As you push down on a page with the pencil, shards of the lead are slowly rubbed off from the pencil, and onto the sheet of paper. Eventually you have to sharpen your pencil because you’ve lost too much lead. An ablative shield is like a big, thick piece of lead infront of the craft, which gradually breaks off as the surface becomes too hot (or to be precise, the heat caused by the friction is energy, and this energy is transfered to the ablative shield, and when enough is absorbed by the top layer of the heatshield, the ablative material gassifies, and slips off the surface, taking the friction’s energy with it, thus dissipating heat).
The Hayabusa2 is not near the end of its journey. As it drops off this capsule, it will continue on to visit two more asteroids, but only on fly-by missions. The completion of these missions, as well as others, will keep the Hayabusa2 potentially employed until 2031. Who knows, maybe they’ll find something new for it to do once we’re closer to that date. I hope you will follow the landing of the capsule containing the precious astroid rocks. I encourage you to watch the video linked bellow. It shows an animated video, about 5 minutes long, of the Hayabusa2’s trip to the asteroid and back. Watch this video here.