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Perseverance Rover lands on Mars [video]

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Re: Perseverance Rover lands on Mars [video]

#321

Post by m4rtink »

Nekhrimah wrote: post #268
Daho0n wrote: post #210

Earlier quoted context omitted.

They really didn't. SpaceX is not cheaper than the shuttle no matter how many times it gets repeated. That SpaceX fudges the numbers so it is hard to compare doesn't make it true. In reality SpaceX is more expensive than not only the shuttle but also their own projections. Here's a breakdown: https://youtu.be/4TxkE_oYrjU

> Here's a breakdown: https://youtu.be/4TxkE_oYrjU I watched the first 90 seconds of this. On the cost of re-usability of a falcon 9 point, the figures are shown as from Wikipedia. So 1) not a primary source. 2) fails to calculate the percentage correctly between $62m and $50m as "around 10%". It's almost 20% on those figures. 3) and most importantly, those numbers are the cost to the customer, not SpaceX's internal…

Yeah, they are certainly not launching so many Starlinks at the same price they charge to the customers. A very big benefit having your own partially reusable rocket (especially as long as no one other has one yet).

Re: Perseverance Rover lands on Mars [video]

#322

Post by mulmen »

heisenzombie wrote: post #315
mulmen wrote: post #310

Earlier quoted context omitted.

If working with simple units of ten is beneficial then every mission should redefine units in terms of expected velocities and vehicle size so they are optimized for the actual calculations at hand. That's not realistic, obviously, so we just pick one. The units in the system are arbitrary, really. In reality regardless of the system you choose every calculation is going to end up with fractions of something. You are…

Physicists are quite fond of redefining units so that the constants they care about are all just 1. ( https://en.wikipedia.org/wiki/Natural_units ). For example, you could define mars units where the gravitational acceleration on mars is 1. Now your velocity in freefall is just equal to the time you've been freefalling! You don't even have to do a calculation! (note: Don't actually do this. Gravitational acceleration…

Honestly I would expect something like that to be happening at a hardware level. The number of bits in a memory address for the ground sensing radar is very interesting. Or the algorithm to determine vehicle acceleration given the voltage reading of a solid-state sensor vs the baseline. The metric system vs the imperial system is not an interesting distinction in these contexts.

Re: Perseverance Rover lands on Mars [video]

#323

Post by yellowapple »

frabbit wrote: post #308
koheripbal wrote: post #165

Earlier quoted context omitted.

Any idea when they will start experimentation? I want to find microbial life!

What is it about that that excites you so much? Is it the idea that life could originate elsewhere and that there might really be aliens? Or is it the idea that Mars could support some sort of colony? Or the hope of completely novel microbiology?

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.

Re: Perseverance Rover lands on Mars [video]

#324

Post by m4rtink »

joe_91 wrote: post #68
raphaelj wrote: post #56

Earlier quoted context omitted.

How could you know? SpaceX never landed or sent a craft on a foreign body.

Haha, good point - we'll have to come back in 4-5 years time when SpaceX have touched down on the moon and mars and check the cost. Considering their low cost & speed at getting things into orbit these days and the plans they have for starship I hope that the data will prove me right in a few years

While this timeline might be optimistic, this is what came to my mind when I heard about the current timeline for Mars sample return - samples returning back to Earth in 2031.

https://en.wikipedia.org/wiki/Mars_sample-return_mission#NAS...

Like it's nice to finally have a firmer timeline for that, but damn, 10 years from now. A SpaceX employee gathering the sample tubes into his backpack in a couple years time to be returned on the next milk-run flight back to Earth is just so much cooler! :)

Re: Perseverance Rover lands on Mars [video]

#325

Post by killjoywashere »

Melkman wrote: post #307
mulmen wrote: post #269

Earlier quoted context omitted.

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…

Consistency is not the only value of a system of units. Convenience is also of importance. And that is where the metric system shines. Having all measures of a unit in multiples 10 combines perfectly with our decimal calculations. Having as few as possible magical numbers to convert and combine between units makes making mistakes harder. How many calories in kinetic energy has a pound going 10 miles per hour ? I know…

Can’t talk to the statute mile, but the nautical mile is sublime: one minute of latitude. The amount of math you can do in your head with a system with so many factors of 2, 3, and 5 is truly amazing.

Re: Perseverance Rover lands on Mars [video]

#326

Post by russtrotter »

frabbit wrote: post #308
koheripbal wrote: post #165

Earlier quoted context omitted.

Any idea when they will start experimentation? I want to find microbial life!

What is it about that that excites you so much? Is it the idea that life could originate elsewhere and that there might really be aliens? Or is it the idea that Mars could support some sort of colony? Or the hope of completely novel microbiology?

Some interesting reasons: the proverbial "2nd genesis", panspermia possibilities of our own planet, and answering lots of questions on formation of life on ours and any other planet we might encounter.

Re: Perseverance Rover lands on Mars [video]

#327

Post by Koshkin »

natosaichek wrote: post #279
Koshkin wrote: post #262

Earlier quoted context omitted.

What do you mean “abstraction”? The colors that I am seeing look very concrete to me. (Also, the “wavelength theory” of color perception does not explain why TV screens work.)

The human retina is composed of cells that are responsive to different wavelengths of light. Color is the word that we use to describe the subjective sensations associated with certain patterns of stimulation of those cells. There is no "yellowness" in a bananna. We cannot construct an instrument capable of measuring "yellow" as such. What we can measure are the intensities of wavelengths of light. We can notice that…

> We cannot construct an instrument capable of measuring "yellow" as such.

Of course we can. We can capture the signal sent through the optical nerve and then reproduce it as a stimulus which will make the brain “see” yellow color.

Besides, humans are capable of distinguishing literally millions of colors, of which just a tiny fraction can be attributed to measuring particular wavelengths (or, more accurately, particular energies of the incident photons). In that way the eye is different from the ear (which performs a kind of Fourier analysis of the sound wave).

Re: Perseverance Rover lands on Mars [video]

#328

Post by mulmen »

killjoywashere wrote: post #325
Melkman wrote: post #307

Earlier quoted context omitted.

Consistency is not the only value of a system of units. Convenience is also of importance. And that is where the metric system shines. Having all measures of a unit in multiples 10 combines perfectly with our decimal calculations. Having as few as possible magical numbers to convert and combine between units makes making mistakes harder. How many calories in kinetic energy has a pound going 10 miles per hour ? I know…

Can’t talk to the statute mile, but the nautical mile is sublime: one minute of latitude. The amount of math you can do in your head with a system with so many factors of 2, 3, and 5 is truly amazing.

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. In some contexts you might just say you pick the closest 1/8th. In others you might use 32nds. You can use the same measuring devices to agree on an ad-hoc standard that everyone understands.

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.

Adjusting HVAC in degrees-C is infuriating to my Fahrenheit sensibilities. 20C is cold, 22C is hot. 21C is probably ok but really I want something like 20.5C. The comfortable range for a room is 3-5 whole units of F, but requires a bunch of fractions in C that you may not even have available on your thermostat.

Sure, converting between units is easy in the metric system. That doesn't make it the best thing to use all the time. Hell, the idea of thousandths of an inch is used commonly, so even the imperial system is base 1000 in some cases. But I've never seen anyone utilize the fractional scale with metric units, probably because the units are the wrong size for that to be useful.

Re: Perseverance Rover lands on Mars [video]

#329

Post by yellowapple »

blach wrote: post #22
distortedsignal wrote: post #4

My personal preference is the JPL raw feed (here: https://www.youtube.com/watch?v=kPrbJ63qUc4 ) but I think that more people watching space here is better! Great link!

From the JPL feed: "My computer was having trouble with Webex, I'll restart Webex and try the visualization again." Hope Percy isn't running Webex.

I mean, I'd be pretty impressed if NASA managed to get Webex to run on a 133MHz PowerPC CPU and 128MB of RAM.

Re: Perseverance Rover lands on Mars [video]

#330

Post by tomc1985 »

mu_killnine wrote: post #31

The Nasa person they have helping narrate what's going on is so genuinely happy the landing went well. It made me kinda tear up. It's infectious just how excited all these people are about this project. Also, I was a bit worried he was going to pass out. 10/10, would watch again (and probably will with my kids)

I love the fact that you could hear people saying things like "yes yes yes YES YES!" in the background as data came in. Like you say, very infectious
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