MSL EDL Options

[Explorer1]

Just to confirm: it is still a go for HiRISE to snap a pic? I didn't hear anything recently, so I'm assuming its not cancelled.

[RoverDriver]

Just to confirm: it is still a go for HiRISE to snap a pic? I didn't hear anything recently, so I'm assuming its not cancelled.

I heard there's 60% probability of successfully capturing MSL during (E)DL.

Paolo

[climber]

Mars as seen from the spacecraft is now about half the size of our Moon as seen from Earth.

[Guest_Oersted_*]

Thanks for that very telling factoid climber: good for visualizing the speed and distance involved.

[climber]

Yes, it's what I like to imagine since Mariner 9 a long long time ago! Kms or miles to go mean a lot more if you can see with your own eyes what they represent. This is very different when a spacecraft nears (no pun intended) Jupiter or Vesta.

[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?

[nprev]

Without knowing the details, the fact that we've succesfully landed six spacecraft on Mars using AFAIK pretty much the same sort of parachute schema (the terminal phases of EDL obviously differ for each spacecraft type & method) strongly implies that this problem has been solved.

[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

[SpaceListener]

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?

According to the publish book: MSLanding, Mars at Glance, the Surface winds at the surface would be between 0 to 32kph, with gust of about 144kph. However the Sky crane will be deselarating and lowering very slow starting from 1.6km from the surface and continue descending at 2.7 kph (walking very slow) and it will release the Curiosity when Sky Crane is hovering at about 20 meters from surface. Besides, at this height, Sky crane must have a very good control of stability before releasing the Curiosity. Its descending will take about 27 seconds (0.75 m/sec). On the other hand, if at this moment there is wind, its wind is so light (1/100 density of Earth's) and the Curiosity is weighing about 341 kg at Martian gravity, then the wind push on Curiosity will be very small. I hope that the lowering controls have greater advantages to control against the spinning and twisting.

[brellis]

Rob Manning suggested:

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.

I tried this, with my cat as the "someone" to swing it. You're right! It even works with my eyes shut!

edit: the 'spin' factor was not helped by my steadying hand, just the swinging back and forth, to and fro. I hope there aren't any giant cats waiting in Gale Crater!

[climber]

I'm pretty sure DAN will show us very soon here what a Catcrane manoeuver would look like

[climber]

To give a rought idea of what is coming up and when (mind, time is approximate and all PST)


Date : August 5th 07h30 am PST / August 4th 16h30 PST / August 3rd 10h30 am PST
Distance to Mars (km) : 192 000 / 384 000 / 768 000
Mars diameter (°) : 2 / 1 / 0,5
Equivalent : Earth seen from the Moon** / Earth-Moon distance / Moon seen from Earth


**: for the happy few that have seen with their own eyes what that really means

[Guest_Oersted_*]

This will be my 5th Mars landing. It never seems to get old.

Been following your landings since Pathfinder/Sojourner... You've come a long way! - I presume the tension is still almost unbearable, but has the emotional experience changed in any way? More cerebral? Better able to "observe yourself"? Enjoying the moment more?

You have got multitudes rooting for you and backing you all over this good Earth!

[ChrisC]

Did this thread go through another delete / restore cycle again today? I had it loaded up on my mobile device yesterday, to start monitoring for the weekend's approach, but when I went to reload it this morning to get the latest, it 404'd on me. I navigated upside down and sideways and the thread simply did not exist anymore. Now it's back. Huh?

Anyway, glad to have it. Thanks, and back to lurking!