iTopSpin

NSTR => Non SpinTop Related => Topic started by: Jeremy McCreary on February 17, 2021, 11:16:37 AM

Title: Perseverance lands on Mars tomorrow!
Post by: Jeremy McCreary on February 17, 2021, 11:16:37 AM
Same bonkers EDL (entry, descent, and landing) sequence used by Curiosity...

https://youtu.be/M4tdMR5HLtg

Took a lot of hutzpah to think that EDL would ever work, but it did last time -- flawlessly! And the entry vehicle at 0:52 looks a lot like our favorite toy.

How to watch...

https://mars.nasa.gov/mars2020/timeline/landing/watch-online/
Title: Re: Perseverance lands on Mars tomorrow!
Post by: ta0 on February 17, 2021, 03:58:44 PM
Thanks for the heads up. I'll try to watch tomorrow at 1:15 PM CST
Title: Re: Perseverance lands on Mars tomorrow!
Post by: Texture on February 17, 2021, 07:24:22 PM
That'll be fun to watch. Thanks for letting us know.
Title: Re: Perseverance lands on Mars tomorrow!
Post by: jim in paris on February 18, 2021, 01:25:44 AM
Wahoo ! 13 000 mph before entry!

Mad!☻

Jim
Title: Re: Perseverance lands on Mars tomorrow!
Post by: ta0 on February 18, 2021, 03:44:58 PM
A few minutes!
Title: Re: Perseverance lands on Mars tomorrow!
Post by: ta0 on February 18, 2021, 03:59:48 PM
Landed successfully!  8)
Title: Re: Perseverance lands on Mars tomorrow!
Post by: Jeremy McCreary on February 18, 2021, 06:19:14 PM
One mission bigwig just said that every time they have a landing, there's a plan and a contingency plan. He then held up the latter and tore it up to great applause in Mission Control. :)

America at its best -- doing the hard things with science and engineering as our guides. Hope the rest of the US government gets back into that habit soon.
Title: Re: Perseverance lands on Mars tomorrow!
Post by: the Earl of Whirl on February 18, 2021, 10:03:47 PM
Yes!  Science is not a four letter word.
Title: Re: Perseverance lands on Mars tomorrow!
Post by: Jeremy McCreary on February 19, 2021, 10:02:19 AM
Excellent comparo of the Mars Science Laboratory and Mars 2020 rovers we call Curiosity and Perseverance, respectively...

https://youtu.be/UEO77UEFGT4

The engineering on both machines is beyond incredible. As for the new stuff, gotta love that sample-handling robotic arm tucked in Perseverance's belly.
Title: Re: Perseverance lands on Mars tomorrow!
Post by: Jeremy McCreary on February 19, 2021, 11:21:04 AM
If we didn't have snow on the ground, I'd celebrate by taking my toy rover for another walk...

https://youtu.be/MobwYuhkSVE

The NASA rocker-bogie mobilty system modeled here schematically turns out to be amazingly effective at any scale. But snow's not its long suit.
Title: Re: Perseverance lands on Mars tomorrow!
Post by: Jeremy McCreary on February 20, 2021, 01:33:52 PM
NASA's getting really good at these animations of how a mission is supposed to go. Perseverance's improbable EDL sequence in its entirety with the actual scenery it will encounter...

https://youtu.be/rzmd7RouGrM

Never gets old. With both Perseverance and Curiosity, EDL went exactly as planned. Boggles the mind.

During Curiosity's 6-month shakedown process, only one function out of thousands failed to meet its performance goals  -- a mast-mounted weather instrument of minor importance that still produced some useful data.

Hoping Perseverance's shakedown goes as smoothly -- only much faster. Ready for this rover to get roving!
Title: Re: Perseverance lands on Mars tomorrow!
Post by: Jeremy McCreary on February 20, 2021, 02:45:33 PM
Sorry to keep posting this stuff, but I can't help myself, as I came down with FPPD (Fulminant Perseverance Perseveration Disorder) on Thursday.

Mars is a place of stark beauty, with evidence of active wind- and fossilized water-driven motion everywhere you look. Stunning 2-part documentary compiled in 4K from scenery shot by the Curiosity, Spirit, and Opportunity rovers...

https://youtu.be/ZEyAs3NWH4A

https://youtu.be/W7FcE7yZl4M

Think private National Park tour on Mars!
Title: Re: Perseverance lands on Mars tomorrow!
Post by: ta0 on February 20, 2021, 03:32:10 PM
Am I the only one who looks at those amazing images and searches for a good spot to spin a top?  ;D ;D ;D

By the way, with lower gravity a top would spin longer before falling. Also it will provide more time in the air to catch the top on a trick. But slower precession will require some adjustments. Texture is young enough that he could try one day ;)

Title: Re: Perseverance lands on Mars tomorrow!
Post by: Jeremy McCreary on February 20, 2021, 06:15:02 PM
Am I the only one who looks at those amazing images and searches for a good spot to spin a top?  ;D ;D ;D

By the way, with lower gravity a top would spin longer before falling. Also it will provide more time in the air to catch the top on a trick. But slower precession will require some adjustments. Texture is young enough that he could try one day ;)

Pretty sure you'd have to pay a big extra baggage fee for Figaro.

Wouldn't it be fun to turn down the gravity in a physically correct top simulator?

Though precession rates and critical speeds would decrease, nutation rates wouldn't change -- at least not directly.

The von Karman aerodynamic braking torque is proportional to air density and the square root of the air's kinematic viscosity. The viscosity is ~100 times larger on Mars than on Earth, while the density is ~100 times smaller.

Net effect: The von Karman torque on Mars would be ~10% that on Earth.

I say we go to Mars ASAP!
Title: Re: Perseverance lands on Mars tomorrow!
Post by: ta0 on February 21, 2021, 01:21:01 AM
The von Karman aerodynamic braking torque is proportional to air density and the square root of the air's kinematic viscosity. The viscosity is ~100 times larger on Mars than on Earth, while the density is ~100 times smaller.

Net effect: The von Karman torque on Mars would be ~10% that on Earth.

This table from Aerodynamics of Mars 2020 Rover Wind Sensors (https://www.intechopen.com/books/mars-exploration-a-step-forward/aerodynamics-of-mars-2020-rover-wind-sensors):

(https://api.intechopen.com/media/chapter/70846/media/Table1.png)

gives the kinematic viscosity 35 times bigger and the density 64 times lower on Mars than the Earth, but the end result is the same: about 10% the von Karman drag torque.
Title: Re: Perseverance lands on Mars tomorrow!
Post by: Jeremy McCreary on February 21, 2021, 01:44:01 AM
Kinematic viscosity measures the rate at which momentum diffuses through a fluid. Wasn't expecting it to be higher on Mars.

It's not very sensitive to pressure, so must have to do with the low mean temperature, the high CO2 content, or both.
Title: Re: Perseverance lands on Mars tomorrow!
Post by: ta0 on February 21, 2021, 09:40:07 AM
I was also very surprised that the kinematic viscosity would be bigger in Mars and that's why I checked.
The dynamic viscosity on Earth is still about two times bigger than on Mars.
Title: Re: Perseverance lands on Mars tomorrow!
Post by: jim in paris on February 21, 2021, 11:57:53 AM
Thanx jeremy for the links
and for tuning us to this fascinating project
Time to read again the trilogy on Mars by kim stanley Robinson

Superb videos  ,
Although there are no Martians ( yet)

Ciao
Jim
Title: Re: Perseverance lands on Mars tomorrow!
Post by: Jeremy McCreary on February 21, 2021, 05:35:35 PM
Superb videos  ,
Although there are no Martians ( yet)

Glad you enjoyed them! As you can see, I'm totally obsessed at this point.

You didn't see Martians because they all moved to Titan when they saw us coming.
Title: Re: Perseverance lands on Mars tomorrow!
Post by: Jeremy McCreary on February 23, 2021, 12:40:39 PM
NASA footage of EDL from onboard cameras...

https://mars.nasa.gov/news/8870/nasas-mars-perseverance-rover-provides-front-row-seat-to-landing-first-audio-recording-of-red-planet/

Can't get a ride like that at Disneyland.