Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Perseverance Rover lands on Mars [video]

youtube.com

Post reply on HN
Print view View original

401–410 of 517 posts

Re: Perseverance Rover lands on Mars [video]

#401

Post by mulmen »

cambalache wrote: post #391
mulmen wrote: post #372

Earlier quoted context omitted.

I don’t understand why it has to be one or the other? Working in fractions is nice sometimes. Inches are a useful size for some situations. I find it easier to say that’s three eighths than 9mm because my ruler doesn’t have different marks for the factors of each mm mark. I use both systems. I do prefer Fahrenheit for HVAC (and weather) because it’s higher resolution and has reasonable values at human scales. Thermos…

> I do prefer Fahrenheit for HVAC (and weather) because it’s higher resolution and has reasonable values at human scales. So you are one of those, lol. There is nothing "less human" about 25 C than say 72 F. Nothing, it just happen to be the scale you are used to.Both are arbitrary. > Fahrenheit for HVAC (and weather) because it’s higher resolution 99.99% of thermostats and thermometer in C had at least 1 decimal pla…

“Human scales” meaning temperatures that won’t burn my skin or give me frostbite. 70 is nice. 60 is cool. 50 is cold. 40 is really cold. 80 is hot. 90 is really hot. 100 is potentially dangerously hot.

I guess 20.5 is nice, 15.5 is cool, 10 is cold, 4.5 is really cold, 26.5 is hot, 32 is really hot and 37.7 is dangerously hot. It’s fine if you are used to it but I don’t really see a benefit.

I was in a hotel room in Japan that only had whole unit adjustments for the A/C. To get 20.5C I had to switch to Fahrenheit. I guess I was unlucky.

I find distances in metric and imperial perfectly usable and use both regularly.

As outlined in detail elsewhere in the thread there are advantages to working in fractions in some situations. Specifically when using a ruler or tape measure with different markings for 1/2, 1/4, 1/8 and 1/16. There’s no reason that has to be unique to inches, it just works out well in some cases.

Re: Perseverance Rover lands on Mars [video]

#402

Post by unanswered »

randomchars wrote: post #388
unanswered wrote: post #378

Earlier quoted context omitted.

Why is it acceptable to use the wrong pronoun, such as "they", for someone who chooses the pronoun "she" or "he"?

> used to refer to a person of unspecified gender. How is this offensive to anyone??

For the same reason referring to anyone with the wrong pronouns is, I would assume. Isn't that offensive? I didn't realize this was up for debate in 2021.

Re: Perseverance Rover lands on Mars [video]

#403

Post by mulmen »

onion2k wrote: post #380
mulmen wrote: post #328

Earlier quoted context omitted.

I'm not aware of any tricks to make mile calculations easier but the fractional scale common with the inch is very useful for real-world mental calculation and practical exchange. Effectively everything is powers of two. Got something between 1/4 and 1/2 inch? Great, use 1/8ths. It's three. Not close enough? How about five 16ths? It infinitely scales to provide another unit that is suited to the measurement at hand.…

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.

Re: Perseverance Rover lands on Mars [video]

#404

Post by stargazer-3 »

jessriedel wrote: post #387
michaelwilson wrote: post #297

Earlier quoted context omitted.

It turns out that they took 640lbs (!) of weight to mars to be tossed off at various points during EDL. The video is worth watching if you'd like some more of the nitty-gritty behind the process: https://www.youtube.com/watch?v=W0NakShgbHY

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, for one, would be uncomfortable with AI removing my accent. I understand it's for other people to understand me better - and I am fine with AI-generated subtitles - but altering the way I speak would reduce the amount of "me" in ways I'm not fully ok with.

Re: Perseverance Rover lands on Mars [video]

#405

Post by DowsingSpoon »

cdelsolar wrote: post #357
yellowapple wrote: post #323

Earlier quoted context omitted.

Yes. Any one of these things would be a massive boon to our understanding of life throughout the solar system and broader universe, right down even to here on Earth. All three of them would arguably mark a new era in Earth's history.

we are very screwed if they find life on Mars. It means life is incredibly common and thus the Great Filter theory is true and we only have a few years left as a species most likely.

Disagree. If there is a filter at all then it could easily be that we’ve already passed it. Maybe the filter is the formation of multicellular life, for example. Also, Earth and Mars have exchanged a lot of material. If we find Mars life, it would not at all be surprising to learn it is related to Earth life.

Re: Perseverance Rover lands on Mars [video]

#406

Post by Aeolun »

theelous3 wrote: post #311
WJW wrote: post #131

Earlier quoted context omitted.

> 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'. :)

What I'm getting from this, is that you can use weights to balance the mass of the spaceship during cruise conditions.

Maybe they have both, and needed a name to distinguish the ejectable weights from the non-ejectable weights?

Re: Perseverance Rover lands on Mars [video]

#407

Post by thiht »

mulmen wrote: post #401
cambalache wrote: post #391

Earlier quoted context omitted.

> I do prefer Fahrenheit for HVAC (and weather) because it’s higher resolution and has reasonable values at human scales. So you are one of those, lol. There is nothing "less human" about 25 C than say 72 F. Nothing, it just happen to be the scale you are used to.Both are arbitrary. > Fahrenheit for HVAC (and weather) because it’s higher resolution 99.99% of thermostats and thermometer in C had at least 1 decimal pla…

“Human scales” meaning temperatures that won’t burn my skin or give me frostbite. 70 is nice. 60 is cool. 50 is cold. 40 is really cold. 80 is hot. 90 is really hot. 100 is potentially dangerously hot. I guess 20.5 is nice, 15.5 is cool, 10 is cold, 4.5 is really cold, 26.5 is hot, 32 is really hot and 37.7 is dangerously hot. It’s fine if you are used to it but I don’t really see a benefit. I was in a hotel room in…

> I guess 20.5 is nice, 15.5 is cool, 10 is cold, 4.5 is really cold, 26.5 is hot, 32 is really hot and 37.7 is dangerously hot.

Or, you know, 20, 15, 5, 30 and 40 instead of the arbitrary decimals you chose to use to prove your point

Re: Perseverance Rover lands on Mars [video]

#408

Post by _-___________-_ »

jessriedel wrote: post #387
michaelwilson wrote: post #297

Earlier quoted context omitted.

It turns out that they took 640lbs (!) of weight to mars to be tossed off at various points during EDL. The video is worth watching if you'd like some more of the nitty-gritty behind the process: https://www.youtube.com/watch?v=W0NakShgbHY

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.

Re: Perseverance Rover lands on Mars [video]

#409

Post by lopis »

michaelwilson wrote: post #297
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,…

It turns out that they took 640lbs (!) of weight to mars to be tossed off at various points during EDL. The video is worth watching if you'd like some more of the nitty-gritty behind the process: https://www.youtube.com/watch?v=W0NakShgbHY

Note: that's 290kg in NASA units

Re: Perseverance Rover lands on Mars [video]

#410

Post by solipsism »

jb1991 wrote: post #355

I can't find any articles that highlight what that component that "flies away" after the landing is going to do next. Does it just get dumped somewhere? Does it go back into orbit?

It flies either forward (with respect to the rover) or backward -- whichever is closer to North -- and crash lands on the surface some distance away.
Post reply on HN