The Perseverance rover confirmed a successful touchdown yesterday, February 19th at ~3:55PM EST. The mission is one of the most ambitious we’ve sent to the red planet - but not just because of the rover (which, itself, is the most complex and featured rover we’ve sent).
The EDL (Entry, Descent, and Landing) platform was also for more advanced than any other we’d sent - with the descent into the Martian atmosphere being yet another part of the experiment. The ablative heat shielding covered the bottom of the capsule - with a type of plating covering it which upon heating would vaporize and be carried away from the Perseverance capsule.
The Perseverance also carried 661lbs of tungsten weights. However, just because they’re dead weight doesn’t mean they won’t serve a purpose.
Two 165 pound blocks of tungsten kept Perseverance in a stable and balanced spin on its journey from Earth. This prevented any one side of the capsule from getting too hot. These are jettisoned 900 miles or so above Mars as they’d no longer be needed. Waste not, though. These two tungsten blocks will slam into the surface of Mars at 9,000 mph or so and is part of a very vital experiment. The InSight lander has a seismometer and even at 2000 miles away it’ll be listening for Perseverance knocking with these tungsten payloads.
Removing those two tungsten blocks is an important part of the entry phase because while balance is required during the journey, the entry requires debalancing. Because one side of the capsule is heavier than the other the entry angle will be at 16°. This leads to a slight amount of lift experienced by the craft, allowing the descent to be controlled via RCS (Reaction Control System) powered rotation - rotate left to cause the lift to push you one way, right to push the other, and go left and right consistently to burn off speed. This is all autonomous!
There’s also six 55lb tungsten masses that ensure landing is aligned. These are jettisoned right before firing the parachute and are used to ensure that the radar will be oriented in the correct direction. While the RCS was fired roughly 2,256 times during atmosphere entry, at this point they aren’t a whole lot of use. These tungsten blocks are jettisoned two at a time, and will cause the craft to roll into the exact orientation needed for the rest of the descent.
Haven’t heard yet if InSight heard Perseverance’s hello to start a welcome party, but all of this was fantastically interesting to me and I’m always surprised at how much NASA can achieve.
Wanna watch it? They streamed the landing on twitch! What an amazing future we live in.