[bargl]

Mark Rober has an awesome video on this which outlines a lot and gives a very high level bit of info on it. I can't imagine the amount of stress these engineers are feeling watching this delayed feed.

https://www.youtube.com/watch?v=tH2tKigOPBU

[jcims]

I wonder how many of those engineers have woken up, wild eyed in the middle of the night, as their brain excavates some random issue or loose end that surfaced and silently trailed off years ago, never to be properly resolved before launch.

[proggy]

It’s happened. Worst one I’ve heard of is when an engineer got an idea of how things could go south just days before the final decision point, ran to the testbed, tried it out, and their worst fears were proven right. They took it to the team, and after much wailing and gnashing of teeth, everyone collectively decided they were more confident in the level-headed plans they had executed to validate the system over the past 5+ years than this last minute, panic-induced test. So...they decided to let the sequence run as planned, and loaded up on a double helping of peanuts for the big day.

Well, the big day comes and guess what? The spacecraft performs perfectly. Everyone was absolutely ecstatic.

It turns out the test bed had been misconfigured, and there was nothing wrong whatsoever with the spacecraft or any of its command sequences.

Really makes you think about how to make the best possible decisions in a crisis.

[jcims]

I've had microscopic renditions of this kind of thing in my career. There's a cognitive 'dolly zoom' effect where there's an illusion of growth in a given risk because the field of view has been narrowed by the preconditions and/or assumptions that led you to consider it to begin with.

It's like the risk of losing a winning lottery ticket. Broadly the risk is negligible, but when you zoom into the precondition of having won the lottery, it's a big fucking deal.

[bhupy]

This is fascinating. Do you have a link with more info?

[dmos62]

What's the lesson in that story? I would have thought that you'd postpone until having fixed the problem exposed by that last test.

[codeduck]

This is only really a viable option prior to launch, of if the probe is coasting and you have enough time.

If the probe is already near its destination, you have a very narrow window during which you can adjust its velocity for intercept.

If you delay too long you do not have enough deltaV to intercept, and either miss your target entirely, or end up in the wrong final orbit with no ability to correct your inclination or eccentricity to what your mission parameters call for. Then you've basically spent years to send a paperweight to Mars.

[ArnoVW]

If the issue requires physically accessing the payload (which has been prepared and packaged, and is sitting on top of a huge rocket) it's not always that easy.

The minimum-energy launch window occurs every 2 years, and lasts a couple of weeks.

[Taek]

This would make an amazing blog post.

[nuccy]

The Cassini–Huygens mission had exactly such a moment [1,2]. A year or so after it was lunched somebody pointed out that Huygens and Cassini communication may fail due to a flaw in handling of Doppler shifted radio signals on Cassini, which should relay data from Huygens. Luckly the spacecraft used a Venus gravity assist and had a close encounter with Earth again, so the issue was tested and confirmed. Engineers had to adjust the descent profile of Huygens, releasing it earlier than originally planned. This made its batteries last shorter after landing on Titan, but the whole mission was saved and data from the surface was properly relayed to Earth.

1. https://en.m.wikipedia.org/wiki/Huygens_(spacecraft)

2. https://youtube.com/watch?v=3ubr151wrHQ

[throwaway0a5e]

The progress from "we can hit a region and maybe last a year" circa the Spirit/Opportunity era to the current state of "if we don't hit it we're close enough to drive to it" has been amazing.

Better computing resources, better simulations, better materials, better and cheaper process control have enabled engineers throughout the entire supply chain to do more with less and when you take snapshots of progress at multi year intervals like NASA does with its Mars missions the progress really shows.

[BugWatch]

Oh, in Spirit's/Opportunity's case, that was 90 days (if memory serves me). So, they were successful beyond the wildest dreams. Curiosity, too.

[throwaway0a5e]

They knew they would last more than 90 days. 90 was just the number they picked for the "days before we can declare success" threshold. They weren't counting on 10yr.

[4gotunameagain]

I work in aerospace, one of my colleagues is part of the team for one of the instruments on the rover. Tomorrow we will attend a NASA telecon with our new mission t-shirts :)

I asked him if he was stressed, his exact reply: "nah not really, not a whole lot we can do now"

[dmix]

TIL the pacel pirate bomb marker guy worked at JPL for 9yrs. That's a really interesting career trajectory.

[andbberger]

dude mentions it every chance he gets...

[ddingus]

As he should. Nasa is cool.

[Judgmentality]

I understand the dude needs to sell himself, but "hey I'm _____ and I worked at NASA!" isn't really that different from "hey I'm _____ and I went to Harvard!"

[ddingus]

I don't care. He is selling Nasa as much as he is himself.

:D

[dataflow]

Maybe not to you, but to me (and I think others) it is quite different. And he gets people excited about science and NASA that way too.

[ddingus]

That is it. Why I don't care. He's doing good advocacy.

[grishka]

I kinda wonder why he left.

[ddingus]

Same. I am sure he has good reasons. Might just be playful ones.

[dmix]

I avoid those "made for youtube" type channels with a bunch of kitschy experiments. I was just surprised he has a legit resume.

[dataflow]

You should watch the squirrel video!

[duxup]

That's how NASA funding pays off!

[ragebol]

For some more technical details: https://www.youtube.com/watch?v=W0NakShgbHY. This makes me even more anxious, there are just so much things that have to go right.

[ugh123]

This video goes into much better detail on the science experiments loaded up on the river. https://youtu.be/95hMM2u6Fgw