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Perseverance Rover lands on Mars [video]

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Re: Perseverance Rover lands on Mars [video]

#391

Post by cambalache »

mulmen wrote: post #372
cambalache wrote: post #366

Earlier quoted context omitted.

So 3 mm is a weird measure but 1/8 of an inch is just perfect? You are like those guys who say that Fahrenheit is better because it feels "more natural and obvious"

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 place. At usual "human temperatures" the difference in resolution between the scales is less than 2X, so even assuming only integer values, I am willing to bet against you in a double blind test that you cannot differentiate 68F vs 69F in an statistical significant way.

> I find it easier to say that’s three eighths than 9mm

Just because you are used to. Fractions are more complicated than integers, every elementary school program knows it.

So to summarize, the problem is not with the magnitude of the units which is arbitrary (a degree F and inches are not more human, logical or normal that a degree C or cm)the problem is with the convoluted way of the imperial system for multiples and submultiples of the base unit.

Re: Perseverance Rover lands on Mars [video]

#392

Post by rmonroe »

nwallin wrote: post #384
whuffman wrote: post #189

Earlier quoted context omitted.

Just as a heads up, the HazCams on Perseverance are in fact in color (Source: https://link.springer.com/article/10.1007/s11214-020-00765-9 - "The Mars 2020 Navcams and Hazcams offer three primary improvements over MER and MSL. The first improvement is an upgrade to a detector with 3-channel, red/green/blue (RGB) color capability that will enable better contextual imaging capabilities than the previous engineering cam…

Huh, I guess so. Looking over the study it looks like they had issues by looking at dirt in scoops and being unable to tell whether it's Martian dirt or a shadow. I have a feeling I'd be the angry guy in the meeting who wouldn't accept the consensus. "but what about latency! what about the descend and landing!" shakes fist

Nah, your concerns are 100% reasonable - they just operate on a different context. On Earth, latency is king. On Mars, especially until the Primary Mission is complete, it's all about risk mitigation. Since we're light-minutes away from Earth, a few frames of latency is nothing. At the same time, you want to avoid breaking your $3B machine, which is hard to operate given the time-of-light delay and comms limitations. Just a different set of tradeoffs. IIRC they first tested on-device deep learning for hazard avoidance in Curiosity, but don't quote me on that.

-Worked at JPL for a few years and have dozens of friends, a few in the vision system.

Re: Perseverance Rover lands on Mars [video]

#393

Post by dtjohnnyb »

chrononaut wrote: post #60

I included this the other day in the previous Perseverance thread but if you're excited for the Perseverance EDL video hopefully Doug Ellison's composite video of Curiosity's landing (from a single camera) can tie folks over in the mean time! https://www.youtube.com/watch?v=RZioPhfxnSY

Have we any idea when that video will be released (roughly).

Re: Perseverance Rover lands on Mars [video]

#394

Post by ncmncm »

Plutoberth wrote: post #360
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 GTFO with its remaining fuel and then crash lands. Going back to orbit would require enormous amounts of fuel.

It's funny that they never say. (My mother-in-law asked if it would go back to orbit, too.) Saying "it flies far enough away to be sure it won't hit the lander when it crashes" would sound funny. They never seem to drive over to check it out, either, AFAIK.

It started with ~800 lbs of hydrazine fuel on board that had to slow tons moving at 200 mph to a dead stop, and then hover for 10+ seconds while the lander spun down; and then boost away and crash. ("Crash-land" sounds like entirely more control than what really happened.)

Re: Perseverance Rover lands on Mars [video]

#395

Post by rsj_hn »

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

Thanks for introducing me to the French Space Guy! I am hooked.

Re: Perseverance Rover lands on Mars [video]

#396

Post by L_226 »

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,…

Soil? Though not sure it is prudent to potentially spread active biological material all over a pristine (eco)system.

Re: Perseverance Rover lands on Mars [video]

#397

Post by DiogenesKynikos »

unanswered wrote: post #196
DiogenesKynikos wrote: post #185

Earlier quoted context omitted.

It depends on what coordinate system you're using. Simultaneity is ill defined in relativity. There's only future, past and "spacelike-separated" (neither past nor future). When they say, "X is 1 minute from happening," it's actually neither in the past nor the future. It's currently spacelike-separated, but in 1 minute, it will be in our past.

Yes, yes, you have shown you know what relativity is. But the relative velocity of earth and mars — which I can't convince Wolfram Alpha to tell me, but it's got to be on the order of their orbital velocity so let's say 5x10^4 mph — is a tiny tiny fraction of c so their inertial reference frames are essentially identical. So sitting in our reference frame, we can make inferences about what's happening "now" on mars,s…

It doesn't depend on the relative velocity of Earth and Mars. It depends on your coordinate system. You can use Schwarzschild coordinates centered on the Sun and use the time coordinate to define simultaneity, but that's an arbitrary choice.

Re: Perseverance Rover lands on Mars [video]

#398

Post by blackrock »

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,…

Don’t litter Mars Elon. Stick your landing. LOL.

Re: Perseverance Rover lands on Mars [video]

#399

Post by jcims »

numpad0 wrote: post #365
theelous3 wrote: post #311

Earlier quoted context omitted.

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

Actually more like that you can eject weights to intentionally un-balance the mass of a spaceship so it'll glide rather than falling straight down. Atmospheric drag force center of drag and center of gravity to line up on a same axis, which force the craft to fly slightly sideways if spacecraft isn't perfectly balanced. Done carefully, it leads to direction of flight being slightly sideways, which is awkward but basi…

It’s like hypersonic curling

Re: Perseverance Rover lands on Mars [video]

#400

Post by saberdancer »

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,…

Bunch of 2x4s and screws/nails :D.
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