[HN Gopher] Designing a Star Tracker for Astronaut Don Pettit to...
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Designing a Star Tracker for Astronaut Don Pettit to Use on the ISS
Author : wallflower
Score : 47 points
Date : 2025-01-14 18:31 UTC (4 days ago)
(HTM) web link (petapixel.com)
(TXT) w3m dump (petapixel.com)
| mkmk wrote:
| > 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 wrote:
| 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 wrote:
| 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 wrote:
| 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.
| lysace wrote:
| Neat.
|
| Debbie Downer: Looks like it fairly easily could have been made
| with like 50% less mass.
|
| Perhaps that wouldn't have mattered though.
| echoangle wrote:
| 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.
| imglorp wrote:
| 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.
| echoangle wrote:
| Did you mean to post this under my comment? I don't see the
| connection.
| imglorp wrote:
| Yes - it might have been 500g lighter if it wasn't fully
| mechanical.
| echoangle wrote:
| True, but even for a fully mechanical one, the one shown
| seems very heavy. It looks like weight wasn't a real
| concern, which is strange. The plates are very thick and
| a lot of material could have been removed to reduce
| weight.
| someguydave wrote:
| Nobody involved wants to take the risk, no matter how
| trivial
| polishdude20 wrote:
| 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.
| lysace wrote:
| "Long" = like 70 cm.
| dylan604 wrote:
| 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.
| echoangle wrote:
| 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.
| dylan604 wrote:
| 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 wrote:
| 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?
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