[X] My Assistant

[nprev]

It's gettin' near that time.

Please post all comments regarding the last portion of Curiosity's voyage to Gale Crater here; thanks!

[brellis]

During the final stage of descent, can a gust of wind start MSL spinning and get the Skycrane cables all twisted up? Would that create a problem with releasing MSL upon landing?

[MarsEngineer]

During the final stage of descent, can a gust of wind start MSL spinning and get the Skycrane cables all twisted up? Would that create a problem with releasing MSL upon landing?

Even a very high speed gust of wind produces a very small force in the low density Mars atmosphere. Remember the force of wind or the dynamic pressure per unit area = 1/2 rho v^2 where rho is the density of the atmosphere and v is the velocity. Mars' density is about 1/100th of earth so in order to "feel" the same force you would get on Earth with a 10 mph breeze, on Mars you would need the velocity of the wind to be 10 times faster (10^2 = 100) on Mars than on Earth. So a 100 mph wind on Mars "feels" like a 10 mph breeze on earth (not counting the sting of entrained dust slamming into your skin at 100 mpg .

In addition we simulated what would happen with a very high speed wind gust while in the skycrane phase and we found that the controller on the descent stage is very responsive. Much as you would be if you were to hold a suspended weight by your fingers. Try this: hang a weight and from a 2 foot string with your hand. Have someone swing it. Now see how fast you can damp the motion by moving your hand with the swinging motion. You will be amazing at how quickly you can stop the swinging. Now do in with your eyes shut. Same.

-Rob Manning
MSL Chief Engineer

PS I am totally focussed on surface now. We are looking really good for Sunday night! ( Knock on wood and pass the peanuts .. then the tums.)
I will be doing a little talking on NASA TV just before landing. If I say anything silly or in error, sorry! You all seem to know more about MSL than normal humans and perhaps even me! (although I try to keep up with you all.) This will be my 5th Mars landing. It never seems to get old.

[djellison]

I will be doing a little talking on NASA TV just before landing.

And so will I - but much earlier than Rob. I'll be on at about 8.50pm local time during the educational pre-show to talk about Eyes on the Solar System and the AR App. Infact, my colleague Jon and I will be sat about 6 feet behind Gay, the presenter of the EDL broadcast, on Sunday night. Rob - I promise not to heckle. :-)

And - tomorrow morning ( at 10am and 11am local ) there is a Science, and an Engineering pre-landing conference. Both should be worth watching.... usual links apply - www.nasa.gov/ntv or www.ustream.tv/nasajpl or /nasajpl2