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Comment by brlewis | Hacker News Reader

> They also had to use a gravity offload system in the form of a motorized lanyard that tugged at the helicopter as it hovered above the ground

This sounds like something that could make the helicopter more stable. Could a physicist please explain why it's still a good test?

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They were probably just testing the thrust it puts out in that atmosphere by measuring the force applied to the tether.

They could also test the stability by trying to maintain a constant force on the tether (by not simply pulling as hard as possible), but I imagine they have different ways to test stability.

If this were the only test, that would be a bad test. They're probably verifying that the flight hardware has characteristics consistent with all the previous test cases before blasting it to Mars. (I work near this project, but not on it directly).

The concept is to have the object as the input and having ARGOS follow and adapt to make the object behave as if it were on another planet. If a person were testing for Mars, ARGOS would make a 100 pound barbell feel like only 38 pounds. Change the environment to Jupiter and the 100 pound barbell would feel like 240 pounds. It is designed to simulate conditions, not support what is already on Earth.

As for the helicopter, ARGOS had to adapt its weight relative to Earth by pulling it up enough to simulate lighter conditions on Mars.

I expect they probably anchored the tether to the center of gravity.

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