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Posted: |
Feb 23, 2021 - 12:09 PM
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By: |
Grecchus
(Member)
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To me, the skycrane came down like a ship. You know, one with a bow, stern, midships, port and starboard sides. So it's falling more or less like a skydiver belly-down with their arms and legs splayed outwards so as to maintain maximum cross-sectional atmospheric drag in the downward, falling sense. A bit like the SpaceX Starship prototypes.
It maintains this horizontally opposed attitude for most of the time, using its on board stable platform/element to maintain an upright sense with respect to the local Martian horizon.
If it needs to move left it heels to port, like a sailing yacht. The same thing happens if it needs to move right, to starboard. It may need to bow or stern dip to move for'ard or aft, depending on how it interprets it's map position. What we don't yet know is if the lander needs a full 3D model of it's immediate surroundings to get around or if just a plain 2D look down, plan position indicator arrangement with north, south, east and west demarcated is sufficient to the task. Either way, those folks had it nailed.
Chris, I think there was more of a dead reckoning approach with Curiosity's touchdown at Gale Crater. The same is largely true of Perseverance with that one AI exception of having a local map to be able to make actual vs purely virtual clockwork-like one-to-one synchronised position estimation. Concorde and B747s used to ply the Atlantic all the time mainly with 3x INS computers voting together to determine a most likely DR Lat/Long instantaneous position fix along the way, which I believe was evaluated as a 2D representation, although I'm not really sure of that. This was before GPS. The pilots would take a radio beacon position fix when leaving the coastline of the departing country. Ater the sea crossing, the last INS (9 max, with internal waypoint registers having to be wrapped around if more than 9 were required) waypoint would lead the way to the next overland radio beacon to bear on the charted course over that particular country's airspace. By the way, none of these methods rely on an active magnetic field for position determination. It's amazing what can be done with the Calculus and precision engineering.
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)
