[ncmncm]

It means that the people who know most about closed-loop vehicle control were not involved in the design of the copter. Such fragility is a really elementary design mistake any experienced engineer would not make. Certainly the vehicle that delivered the lander would not suffer from the same mistake.

My interpretion is that the copter, as an inessential system component, was seen as an opportunity for junior people to get some end-to-end experience. I hope they are learning the right things.

[ehsankia]

The article makes it sound like after the missed frame, every subsequent frame had the wrong timestamp and was processed wrong, so it sounds like more of a bug. If the subsequent timestamps had the right timestamps, and the calculation was based on delta timestamps, then it would basically basically interpolate over the missing frame and then recover. The fact that every subsequent frame was assumed to be 33ms in the past was the issue here.

[mikepurvis]

And that being a system boundary thing, it’s easy to imagine it as an integration issue, where the controls side maybe assumed it would get a dummy frame or something.

[ncmncm]

For a real-time attitude-control feedback loop to have been subject to upset by such a bug is, exactly, the design flaw.

[4gotunameagain]

A quick search would have you know that the lead of the navigation for the copter is David S. Bayard, an awarded scientist in the control field in NASA.

So maybe the issue is not as simple as a news article portrays it

[ncmncm]

Then, apparently the real-time attitude-control feedback loop was delegated to somebody else less experienced. Navigation is a wholly different responsibility that may happen to rely on input from some of the same hardware.

On the other hand, scientists are often not as good at design as engineers. They are not routinely trained in it, and are expected to deduce it from first principles. (If you have seen code written by scientists, you will know what I mean.) When they err, it is typically by assuming that theory and practice are the same.

[avs733]

do you have ANY evidence to support this claim?

or are you relying on a third party article's interpretation and then extrapolating that even further?

[stevenhuang]

If the failure mode is being described accurately then it's clear to those who worked on hardware that these are not the sort of problems that should be encountered this late into the cycle (on Mars). Perhaps we just need more info on the situation. But as it currently stands, things smell a bit amateurish.

See also: https://news.ycombinator.com/item?id=27555761

[ncmncm]

The flight instability is, all by itself, ironclad proof of a design flaw. When a constant time-offset navigational input can affect real-time attitude control, that is a rookie booboo.

The exact nature of the design flaw is subject to further investigation.