8 ms·
Breaking after a mere 10 miles, to me sounded really awful, but apparently they planned on this. The construction must have been to save on weight, making the w
by 6DM 10y ago
Breaking after a mere 10 miles, to me sounded really awful, but apparently they planned on this. The construction must have been to save on weight, making the wheels no more reliable than the exact distance they wanted to travel: "...milled out of solid aluminum. The wheels contact ground with a skin that's about half as thick as a U.S. dime, except at thicker treads."
- arethuza 10y agoI wonder if stresses build up from the day night cycles on Mars - which I suspect would be pretty harsh on finely machined bits of metal.
- ceejayoz 10y agoSort of. The early wear was much faster than anticipated, so they've since been using softer ground (sand instead of rock) as much as possible. You don't want to carry around any unnecessary grams on a rover, but I suspect the next one will have sturdier wheels.
- jakobegger 10y agoI 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.
- pc86 10y agoIt's easily Google-able. A little more than half a millimeter.
- jamiethompson 10y agoAgreed. A number of millimetres would be a more helpful comparison.
- vermontdevil 10y agoIt would be about .675 mm. A dime is about 1.35 mm thick
- tossaway1 10y agoThat'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.
- bumblebeard 10y agoI'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.
- 6DM 10y agoGood point, I should have added that translation in.
- tossaway1 10y agoAre 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.
- Cyph0n 10y agoThere really was no need to go through the user's submission history. Try not to overreact next time.
- tossaway1 10y agoI 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...
- planteen 10y agoIt's very likely that the mechanical drawings were in inches for the machinists, even for NASA. The scientists are using metric units.
- mturmon 10y agoNo. That would not be the case.
- planteen 10y agoWhat 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 https://en.wikipedia.org/wiki/Thousandth_of_an_inch
- mturmon 10y agoThe 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.
- planteen 10y agoThanks for the explanation and glad to hear that space is slowly moving towards metric.
- comicjk 10y agoMaybe they should have a second, international press release.
- drdaeman 10y agoJust 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.
- JackFr 10y agoI'd give them a pass for the press release -- it was paid for with U.S. dimes.
- devb 10y agoRemember that the rover weighs almost 2000 pounds, so each wheel is responsible for carrying around 330 pounds on average over very rough terrain.
- arscan 10y agoIs that the weight on Earth or Mars? Sites listing its specs are unclear on that.
- exDM69 10y agoWikipedia says the dry mass is 899 kg, which is about the 2000 pounds of weight (on Earth) mentioned by GP. https://en.wikipedia.org/wiki/Curiosity_(rover) https://en.wikipedia.org/wiki/Curiosity_(rover)
- Cthulhu_ 10y agoWhich would make it about 338 kilos on Mars - wikipedia lists Mars' gravity as 0.376g (vs earth's 1)
- masklinn 10y agoTechnically that would make it 899kg on Mars, the kilogram is a unit of mass. However the Rover would weigh ~8800N on Earth and ~3300N on Mars.
- masklinn 10y agoThe pound is a unit of mass, same as the kg (it's defined as exactly 0.45359237kg). Just as 900kg is 900kg everywhere, 2000lb is 2000lb everywhere. The colloquial weight is literally a force, and its imperial unit is thus the pound-force.
- samcat116 10y agoThis is incorrect. The pound is a unit of force, similar to a Newton. The pound-mass(notated lb-m) is similar to the kg. The conversation you gave above is based on Earth gravity for weight.
- caio1982 10y ago"[...] a mere 10 miles" You must be kidding... this is a robot, which survived a hard landing, driven on exotic alien terrain, with async remote control from another planet :-) The fact that they built it and drove it for over 15km is absolutely impressive by my engineering standards.
- artursapek 10y agoI think he's just commenting on the wheels, not the mission as a whole. We obviously are good at making wheels that last longer than 10 miles here on Earth.
- radiorental 10y agoAgreed but I would call the landing anything but hard. The precision and care with which that vehicle was delivered to the surface is just a mind boggling feature of engineering.
- wlesieutre 10y agoFor anyone who missed this, they lowered the rover to the surface from a levitating rocket-powered skycrane.
- kristjansson 10y agoI don't know if there's another true sentence from which I can derive as much joy as this one.
- cr0sh 10y ago...which was controlled autonomously to boot! Definitely one of the most bad-assed ways to deliver a rover to the surface of another planet. If you had told me as a kid this would be possible, I would have considered it almost impossible, except maybe as a science fiction concept.
- JohnJamesRambo 10y agoIs the terrain any more dangerous or grueling than a desert terrain on earth though?
- syntheticnature 10y agoLet's also note that the top speed of the rover in optimal conditions was 0.09 mph (0.14 km/h), and it took them a full year just to reach the first kilometer of travel.
- jacquesm 10y agoI'm sure you would have done a better job. Now please tell me: How would you have improved on this given the mission constraints? Are you 100% sure that this isn't a case of 'why didn't they?' where laypeople not involved in a project know exactly what should have been done by the experts that were involved in the project?
- JabavuAdams 10y agoWhy the harsh tone? The parent poster outlines their initial incredulity and subsequent learning. Nowhere do they suggest that they could have done better.
- Tepix 10y agoThey planned on this, but the article (and NASA) does not reveal whether the wheel damage was expected at this point or sooner or perhaps even somewhat later.
- anotheryou 10y agoIt was much worse than initially expected.