Designing a Star Tracker for Astronaut Don Pettit to Use on the ISS

https://petapixel.com/2025/01/14/designing-a-star-tracker-for-astronaut-don-pettit-to-use-on-the-iss/

by wallflower • 2 years ago

75 25 2 years ago

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mkmk• 2 years ago

Don is a bit of a machinist himself, so we decided to have some fun with the device name.

I don’t get it, anyone able to explain?

petee• 2 years ago

I think its just them being overly technical on the naming the mechanism, ie "Rotational Coil Spring Powered", rather than just being a plain ol Windup Star Tracker

snypher• 2 years ago

My only thought is 'RCSPAST' is the joke, but I still don't get it.

Edit: I think maybe Don's reputation as an in-space inventor (first patent for something invented in space) means the clock spring device got a long and contrived name for it's quite basic function.

ColinWright• 2 years ago

This tripped me up:

  "I was not a big fan of designing a
   mechanical clock unless there was
   another option."

So either this should be "... unless there was no other option", or I'm completely misunderstanding.

lysace2• 2 years ago

Neat.

Debbie Downer: Looks like it fairly easily could have been made with like 50% less mass.

Perhaps that wouldn't have mattered though.

echoangle4• 2 years ago

True, I wonder how that would not be a factor, surely they always have stuff they could send up to the ISS as a backup. So if they would have made this 500g lighter, they could have sent 500g more food, for example.

I also can't imagine that the resupply flights are volume limited instead of mass.

imglorp2• 2 years ago

NASA's 2-year cert for electronics requirement is puzzling. I understand rules about mission critical electronics: you want to (a) depend on it and (b) avoid fire, magic smoke, and blowing breakers on the Station. But for a non-critical application, you don't care about (a) and the risk of (b) from a 5V/2A microcontroller with a worm drive motor seems reasonably remote.

polishdude20• 2 years ago

They've got the camera mounted to it using a long moment arm in one of the photos. The tracker needs to be really rigid to hold it I'd think.

lysace2• 2 years ago

"Long" = like 70 cm.

dylan6044• 2 years ago

fairly easily how? bold statement with no explanation of your ideas on where the wasted mass is.

the front/back plates? looks like your standard 3/8" aluminum plates. could they have used 1/4"? other materials like plastic/carbon would probably not have passed NASA requirements. plastic/carbon could chip into small pieces which is a very bad thing on the ISS. so you're left with a metal, and aluminum is pretty safe choice. it's clear there are several holes in these plates that are not tapped and are there solely as a means to reduce the weight.

moving the pieces closer for a tighter fit resulting in a overall smaller unit size? this thing is meant for ease of use. extra space affords that, and making it more compact complicates its use.

echoangle4• 2 years ago

You could have made a lot of holes on those plate to reduce weight while still having it very rigid. Those plates are extremely oversized right now.

dylan6044• 2 years ago

Looking at the way the system is rigged to the wall of the station is quite humorous to me in how it is taking full advantage of being weightless. From the arm the camera is attached to the tracker, and then the tracker being mounted to the one arm just seems like it would collapse on itself if it were on terra firma.

I've seen some crazy/shitty rigging done, but this one gets a pass because it's in spaaaaaaaace

zokier• 2 years ago

I do kinda struggle to understand the geometry here though. Especially in the picture with the black-out fabric, how is the camera rotating to track stars?

4gotunameagain3• 2 years ago

In the image you referenced, the camera is tilting (or pitching, if you think in aircraft terms). Since the axis of rotation (the axle coming out of the tracker) is not super offset from the camera, the arc that the camera traces is not that wide. It seems like the surrounding blanket is mounted loosely enough to allow quite a bit of movement.

It also seems like it does not need to be capable of very long exposures, as also betrayed by the traces of the bright terrestrial lights in the demo photograph at the end.

Stevvo• 2 years ago

People are often quick to dismiss the impact of Starlink satellites on space photography, but here the impact is clear. Starlink ruins the photo.

AstroJetson• 2 years ago

So the real magic is the clock mechanism, these guys bolted a 60:90 gear pair and called it a day. How about some kudos to the engineers that made the clock and the company that made them. They can then say to their friends / family, hey one of my clocks is in space. Lots of glory to go around.

Designing a Star Tracker for Astronaut Don Pettit to Use on the ISS

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