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Perseverance Rover lands on Mars [video]

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Re: Perseverance Rover lands on Mars [video]

#421

Post by mikewarot »

jws wrote: post #344
Azrael3000 wrote: post #55

It's a great achievement with some really interesting work done on the landing algorithms with terrain recognition and it seemed to have worked exceptionally well. Looking forward for the next landing in May of the Chinese rover and all the science these robots will produce. Also, the test of Ingenuity, the helicopter, will be very interesting to watch, that could really pave the way for a different exploration style…

Early starships got me thinking: given the high likelihood of a failed starship landing, and maybe having the ability to send one before fully engineering a payload… What would you ballast a starship with for the practice missions? Useful materials which might survive a RUD and aim for someplace near a likely landing zone? If you crash the parts of a milling machine, a lathe, some tooling, some assorted metals stock,…

Why not work on some very small machines that can mine and refine materials to make more of themselves?

Re: Perseverance Rover lands on Mars [video]

#422

Post by onion2k »

mulmen wrote: post #403
onion2k wrote: post #380

Earlier quoted context omitted.

But with the metric system you only really get cm (too coarse) and mm (too fine) but you don't get something like 9/16 so you can't "work in 16ths" and have everything be whole units again. People who use metric units are perfectly happy rounding to the nearest 0.5cm or 0.25cm if that's what's needed, exactly as people do with inches. Why on earth would you imagine people use mm if something doesn't call for them?

But does anyone say 1/8th centimeter? Seems easier to just drop down to millimeters at that point. Which is fine, but it loses out on the convenience of fractions.

People do say things like 1.25mm, which is 1/8th of 1 cm.

Presumably someone who uses Imperial would say 5/128th inches if they wanted to describe something that's equivalent to 1mm?

Re: Perseverance Rover lands on Mars [video]

#423

Post by Cthulhu_ »

mulmen wrote: post #269
spaetzleesser wrote: post #236

Earlier quoted context omitted.

They should make km the default unit and not miles....

Ever been on an airplane? Altitude was almost certainly measured in kilofeet. As noted in other comments, NASA (like the rest of the United States [1]) does use the metric system. But it doesn’t matter. Nothing about the metric system makes it uniquely suitable to landing on Mars. Or space travel in general. What matters is a consistent standard. Internally NASA could use Armstrongs. Where 1 is the weight or height o…

Quick, how many miles is 26357 feet?

With metric it's a matter of shifting the decimal.

How much is a sixteenth inch anyways.

Re: Perseverance Rover lands on Mars [video]

#424

Post by jerven »

bernulli wrote: post #356
mulmen wrote: post #337

Earlier quoted context omitted.

Ok, so? First off, you linked to a list of english measures which are not used in the US. Nobody uses fathoms or barleycorns. Here is the list of actual US customary units: https://en.m.wikipedia.org/wiki/United_States_customary_unit... Second, none of that is relevant to landing on Mars. The only problem space where metric has an advantage is in converting between meters, kilometers and millimeters. That’s great, an…

Yes I understand. Imperial is awesome because you can divide a foot by exactly 2, 3, 4 , and 6, which of course, is the main problem everyone has every day. Metric on the other hand sucks because none of my measurements will ever be nice round numbers. The hardware doesn’t think in base 10, but having more than that in imperial makes it better? Your document lists 12 mass units alone. I rest my case, what could possi…

I just want to add. It's quite common in carpentry to work with 120cm base wood. Which devides just as nice. And even then it's easier to convert when moving into bigger or smaller units.

Re: Perseverance Rover lands on Mars [video]

#425

Post by aardshark »

_-___________-_ wrote: post #408
jessriedel wrote: post #387

Earlier quoted context omitted.

Great video! I am also surprised by the fact that they bring that much mass just to jettison. In theory they could mounted some of the useful mass on a slider/rail system to achieve the necessary adjustment to the mass distribution without dropping mass overall, but apparently it wasn't worth the complexity/volume cost. I'm sort of surprised we don't yet have ML powered "de-accent-ization". His french accent isn't ha…

I’m amazed that people still say things like “de-accent” as if there was such a thing as “no accent”. You are asking for a button that makes his French accent more like your own. It’s a separate thing from native vs. non-native speakers - there are plenty of native English speakers with accents that you would also find challenging.

There is no such thing as "no accent". There is such a thing as a more neutral accent, or an accent more widely understood.

Re: Perseverance Rover lands on Mars [video]

#426

Post by george3d6 »

mikewarot wrote: post #421
jws wrote: post #344

Earlier quoted context omitted.

Early starships got me thinking: given the high likelihood of a failed starship landing, and maybe having the ability to send one before fully engineering a payload… What would you ballast a starship with for the practice missions? Useful materials which might survive a RUD and aim for someplace near a likely landing zone? If you crash the parts of a milling machine, a lathe, some tooling, some assorted metals stock,…

Why not work on some very small machines that can mine and refine materials to make more of themselves?

Because "refine" really means "melt at temperatures ranging from 500 to 4000 degrees celsisu and then extract via various mechanical processes and/or using various reactants which often require gigantic plants to produce and are highly unstable".

Basically all of the history of science until 200 years ago was figuring out "mine and extract" and the course of civilization is very much linked with the price & quality of metal structures they could produce. But it's gotten so good we take it for granted.

However that is because of gigantic plants situated in specific areas where energy is cheap that do this thing at an amazing scale.

Aluminum is cheap as chips, except that it used to be more expensive than platinum (and at a much higher impurity ratio than the stuff we use for baking or for making cheap cases).

Heck, gold is "a thing" because we could purify and mold it without bringing it to a melting point and it was, for a very long time, the only metal available to us to do anything with, way before the bronze age.

And the problem with the refinement process is that you can't really "be smart" about it, reaching very high temperatures is one of those things you can't really scale down in an efficient way. You'd have to propel 100,000 tons of factory to mars in order to efficiently refine anything remotely close to the metals we had access to 100 years ago.

Which is not to touch on the mining bit, that is in itself very complicated (see how slowly and shallowly rovers are currently able to drill).

Are there workarounds for this? Maybe, I don't think anyone knows them though, they are not the kind of thing that's within easy reach. Maybe if we happen to stumble upon large reserves of bismuth or lead or gallium or mercury close to the surface of Mars, and build a whole branch of engineering around using those to build machinery... ? But my limited knowledge of geophysics and geology tells me that finding those in large amounts is very unlikely.

For reference, if you take an oven, that can reach, say, 450 degrees celsius (home) and up to 700 (industrial). Those aren't enough to refine any "useful" metal (e.g. iron) and building them requires materials that were produced at 1500+ degrees.

IANAChemist/IANAMaterialScientist/IANABlacksmith though, so take with a spoon of salt.

Re: Perseverance Rover lands on Mars [video]

#427

Post by enriquto »

jessriedel wrote: post #415
_-___________-_ wrote: post #408

Earlier quoted context omitted.

I’m amazed that people still say things like “de-accent” as if there was such a thing as “no accent”. You are asking for a button that makes his French accent more like your own. It’s a separate thing from native vs. non-native speakers - there are plenty of native English speakers with accents that you would also find challenging.

You are reading something into my comment that wasn't there in order to pick a boring fight. There is of course no such thing as no accent a priori, but there is such a thing as "accents understood by (vastly) more people" and "accents closer to the mean accent of native speakers". When I learn Russian, my English accent is not on the same footing as a Muscovite's; the intended notion of "de-accenting" the English ac…

> accents closer to the mean accent of native speakers

Notice that, for the case of English, most speakers are not native, by a huge margin! Native English speakers are a biased minority, and with a lot of variation within. Not sure that an "average native" accent is a useful concept at all. I, for one, tend to find most non-native English speakers vastly easier to understand than many native speakers.

Re: Perseverance Rover lands on Mars [video]

#428

Post by flemhans »

mulmen wrote: post #363
spaetzleesser wrote: post #346

Earlier quoted context omitted.

People often say something is 1 and a half meters long. I don't understand how people can work with inch measurements. How do you divide 7"3/8 by 5? This seems a major pain.

One and a half seems natural. What about something like a quarter meter? I guess that just becomes some number of centimeters? > How do you divide 7"3/8 by 5? Same way I divide 4.7625 cm by 5. With a calculator.

> I guess that just becomes some number of centimeters?

25, yes. It's not too hard to do the math.

> Same way I divide 4.7625 cm by 5. With a calculator.

That's roughly 0.95 right by intuition, but (7"3/8) / 5 doesn't come easy to me.

Re: Perseverance Rover lands on Mars [video]

#429

Post by rkagerer »

WJW wrote: post #131
tectonic wrote: post #14

You can also watch an EDL visualization in your browser: https://eyes.nasa.gov/apps/mars2020/#/home And read about how it will use Terrain Relative Navigation to find a safe landing spot: https://www.jpl.nasa.gov/news/a-neil-armstrong-for-mars-land... Perseverance is phenomenally complex, its Sample Caching System alone contains 3,000+ parts and two robotic arms. So exited for all the sciencing this nuclear-powered,…

> is this what NASA calls 'weights'? Well no, the Cruise Mass Balance Devices are intended to Balance the Mass of the spaceship during Cruise conditions. That these Devices are single-part and constructed out of a single chunk of metal each should not be construed as merely being 'weights'. :)

Got it. Fancy weights.

Re: Perseverance Rover lands on Mars [video]

#430

Post by mikewarot »

george3d6 wrote: post #426
mikewarot wrote: post #421

Earlier quoted context omitted.

Why not work on some very small machines that can mine and refine materials to make more of themselves?

Because "refine" really means "melt at temperatures ranging from 500 to 4000 degrees celsisu and then extract via various mechanical processes and/or using various reactants which often require gigantic plants to produce and are highly unstable". Basically all of the history of science until 200 years ago was figuring out "mine and extract" and the course of civilization is very much linked with the price & quality o…

We don't have to be efficient, just small and reliable, no matter how slow... if there were enough small machines to turn out enough materials to build new ones faster than the failure rate, then geometric growth wins, and you can build whatever you want, eventually.
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