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Comment by jakobegger | Hacker News Reader

I thought NASA used metric units; would be nice if their press releases did too. I have no clue what "half as thick as a U.S. dime" means.

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That's a description that most Americans can more easily picture than something like 0.68 mm (including people who are comfortable with metric units like myself) and they seem to be focusing a lot in recent years on making the information they provide more accessible to average Americans, undoubtedly to help drive interest in and support for what they're doing.

I'd prefer if they wrote something like "0.68 mm (about half as thick as a US dime)." That way the number is still there for people who don't want to look up how thick a dime is.

I'd give them a pass for the press release -- it was paid for with U.S. dimes.

It would be about .675 mm. A dime is about 1.35 mm thick

Agreed. A number of millimetres would be a more helpful comparison.

It's easily Google-able. A little more than half a millimeter.

Good point, I should have added that translation in.

Are you implying you're the author of this press release? It looks like you were job hunting 6 months ago (based on your one HN submission) -- now you're writing press releases for NASA??

Edit: Nevermind, I'm a dummy.

There really was no need to go through the user's submission history. Try not to overreact next time.

I was interested to see his profile if he worked at NASA in this capacity. He had one submission -- it's not like I pored over his history. I don't think I overreacted -- I was impressed that someone could get to a point that they're authoring NASA press releases so quickly.

Like I said, though, I'm a dummy...

It's very likely that the mechanical drawings were in inches for the machinists, even for NASA. The scientists are using metric units.

No. That would not be the case.

What makes you say that? I've worked for two spacecraft companies in the US who supply parts (and whole spacecraft) to NASA. Both of them did drawings for small parts in mils (thous) for both electrical and mechanical parts. It seems like most machinists in the US are used to working in mils.

I remember on my first day (year 2012), I was shown an E-sized drawing of a spacecraft bus at 1/10 scale. The unit was inches. I was surprised it was in inches and said something. The person showing me just laughed and said welcome to aerospace.

The Wikipedia for mil is full of machinist lingo: https://en.wikipedia.org/wiki/Thousandth_of_an_inch

The mechanical specifications I've seen for newer (post-2000, say) components at the lab that built this particular robot have all been in metric units. I just checked, and the current requirement is that metric "shall" be used, unless (a) a particular mission waived that practice - I don't think MSL did; or (b) for parts from "industries that are historically in another unit of measure." Two examples I know of are gears and printed wiring boards, which are indeed in mils.

And you're right, it is possible, barely, that the wheels were an exception. I don't know if they were fabricated on lab or not.

Thanks for the explanation and glad to hear that space is slowly moving towards metric.

Maybe they should have a second, international press release.

Just a "10 miles (16km)" and "half as thick as U.S. dime (0.68mm)" - either directly in text or as on-hover/on-tap tooltips (for web) - would've did the trick just perfectly.

"half as thick as U.S. dime (0.68mm)" is ambiguous: is the dime that thick, or the wheel?

Or you could say something like:

...10 miles on a tire only 0.68mm thick, about half as thick as a US dime.

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