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MSL Video
mars_armer
post Nov 21 2006, 07:14 PM
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A search on youtube for "JPL MSL" came up with this:
MSL EDL Animation
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lyford
post Nov 21 2006, 08:57 PM
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hmmm - i didn't realize that the plan was to lower the MSL from so high above the surface before touchdown..... I imagined the hover in place would have been more similar in height to right before the airbags are cut on MER.

edited for grammar


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Stephen
post Nov 22 2006, 12:06 AM
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QUOTE (mars_armer @ Nov 22 2006, 06:14 AM) *
A search on youtube for "JPL MSL" came up with this:
MSL EDL Animation

Quite a find! (I liked the blurb at the end: "Coming to a planet near you October 2010".)

I notice the video was only posted a few days ago. Have NASA & JPL posted this on their websites yet? The MSL website here keeps saying "coming soon".

======
Stephen
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nprev
post Nov 22 2006, 04:46 AM
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Very cool indeed, but I sure hope they don't put her in the bottom of a canyon unless there's definitely a way out... unsure.gif


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MarkL
post Nov 22 2006, 06:55 PM
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Nice video. Agreed, Lyford. I think they are nuts to depart from the proven payload delivery system that worked perfectly for Pathfinder and the MERs. The long descent with retro rockets will be treacherous and unpredictable. I don't trust a computer to do it as well as a parachute! (But major kudos if it works of course and I will be happy to come back here and eat my words).
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remcook
post Nov 22 2006, 07:14 PM
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"I think they are nuts to depart from the proven payload delivery system that worked perfectly for Pathfinder and the MERs."

I though MER was about the limit of what you can put onto Mars with that technology... huh.gif
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centsworth_II
post Nov 22 2006, 07:41 PM
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QUOTE (MarkL @ Nov 22 2006, 01:55 PM) *
The long descent with retro rockets will be treacherous and unpredictable. I don't trust a computer to do it as well as a parachute!


Lots to be scared about! What if ALL the cords connecting the rover to the decent engine don't detatch before it flys off after landing the rover? ohmy.gif
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lyford
post Nov 22 2006, 07:55 PM
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Scaling up MER to MSL won't work with airbags from what I have read.... and I have even come around to accepting skycrane as a workable concept. What makes me nuts is that they don't seem to be planning full scale live testing in the desert, but rather are relying on modeling. Test as you fly, eh?

Or perhaps someone can clue me in on why I should be happy about this....


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djellison
post Nov 22 2006, 08:11 PM
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If you describe to yourself the process of the MPF and MER landings, and then do the same for the MSL landing...neither is particularly confidence inspiriing.

The thing to remember is that there is only one team of working age in the world that has landed on Mars, and it's done it three times. If they think that the MSL system is the way forward, to be brutally honest there isn't really anyone out there to challenge that imho.

" The long descent with retro rockets will be treacherous and unpredictable."

Well - that's no different to Viking (worked twice) - and indeed given that it's from only 900m altitiude, the MSL decent stage will be working for a shorter period of time than that for Viking probably. We did that 25 years ago.... to call it treacherous and unpredictable today is not true.

There was no full scale testing for Pathfinder, Viking, MER...you just can not test that sort of stuff on Earth - there's no way to replicate the conditions. You can test systems, you can simulate based on those systems - but you just have to build enough smarts and flexibility into the system to mitigate the risk.

And as someone else has mentioned - the bags just don't 'do' bigger....and as it is they take up a HUGE ammount of the payload. For a delivered rover of 180kg, you have 827kg hitting the top of the atmosphere. Scale it all up - a 500kg rover - we're talkig 2300 kg at the top of the atmosphere. The bags are good up to a certain point - but beyond that, they just don't make any more sense.

Doug
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helvick
post Nov 22 2006, 08:53 PM
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QUOTE (centsworth_II @ Nov 22 2006, 07:41 PM) *
What if ALL the cords connecting the rover to the decent engine don't detatch before it flys off after landing the rover? ohmy.gif

The cord cutting event does look awfully risky when you see it on video but it's not significantly different to the risk associated with blowing the backshell\heatshield and the hundreds of other exquisitely choreographed events that are needed for any lander to get to the surface safely.

Now I would be terrified if I was the engineer actually responsible for making sure it was 100% OK but I think it's safe to say that these guys have proven (repeatedly) that they are pretty damn good at that sort of thing.

The SkyCrane is ambitious but it's not insanely ambitious and I remember prior to the Pathfinder just how insane that seemed before it was proven (again, repeatedly).

I'm a fan - and I'm really happy that we've finally gotten to see this animation. Sweet and many thanks to tubeyhowser for posting it, whoever he/she/it/they are smile.gif
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lyford
post Nov 22 2006, 10:29 PM
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QUOTE (djellison @ Nov 22 2006, 12:11 PM) *
There was no full scale testing for Pathfinder, Viking, MER...you just can not test that sort of stuff on Earth - there's no way to replicate the conditions.

I agree, but for some reason I thought they had planned live testing of the "hover and drop" bit but it had been cancelled due to budget. I may be misremembering but I would feel better if they had said that they had cancelled it due to confidence in the simulations.


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centsworth_II
post Nov 23 2006, 11:58 AM
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QUOTE (djellison @ Nov 22 2006, 03:11 PM) *
The thing to remember is that there is only one team of working age in the world that has landed on Mars, and it's done it three times.

No disrespect meant, I'm a big fan of those guys, but this is the point at which one must be on the lookout for hubris. I hope they keep their edge and do not get over confident.
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ustrax
post Nov 23 2006, 12:25 PM
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QUOTE (centsworth_II @ Nov 23 2006, 11:58 AM) *
No disrespect meant, I'm a big fan of those guys, but this is the point at which one must be on the lookout for hubris. I hope they keep their edge and do not get over confident.


I'm sure that when the airbag idea appeared there were also comments regarding the lunacy of the idea... wink.gif
The time is to innovate and...roll! wheel.gif


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MarkL
post Nov 23 2006, 04:13 PM
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Check out this article if interested in more detail on MSL EDL. Doug, no matter how you slice it EDL is treacherous and requires perfect execution. It seems like a miracle that the little guys/gals get down in one piece.

Edit: Sadly, wouldn't be complete without this.
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djellison
post Nov 23 2006, 04:57 PM
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QUOTE (MarkL @ Nov 23 2006, 04:13 PM) *
Doug, no matter how you slice it EDL is treacherous and requires perfect execution. .


I totally and utterly agree 110% and would never suggest otherwise. However - there is much criticism of the skycrane manouver simply because it looks a bit scarey. So did Viking, so did MPF, so did MPL and so did MER. In some respects it is a hybrid of Viking and MER/MPF techniques...the throttled decent of Viking followed by lander seperation on a bridle and bridle cut at the surface.

I thnk I've been through every PDF I can find and I've even swopped emails with some JPL engineers about the MSL system. When you REALLY think about it - if it can be made to work (and I have no reason to see otherwise) it's arguably a more reliable means of getting things on the ground than the MER system, and certainly the most weight efficient way of getting a rover of that size on the ground.

Put it this way - I have a higher expectation of the MSL system than I would of a repeat of the MER/MPF system and arguably higher than the MPL/Phoenix pulse throttle system.

You are very wrong to label them as 'nuts' for leaving the MER system behind. It simply can not scale to MSL weight. They have to come up with a means of getting a rover on the ground outside that platform. The 'long decent with retro rockets' is actually going to be a shorter decent on retro rockets than was the case for Viking - only about 900 metres. Look at the efforts of Armadillo Aerospace with very little money and time to produce something which could be seen as similar to the MSL decent stage.

I'm not trying to ignore the difficulties...being here in Leicester, I really don't need to be reminded how hard landing on mars actually is... but I'm yet to see a sound argument against the MSL design based on anything other than 'it looks scarey'. With an atmosphere not thick enough to be usefull but thick enough to be a problem - landing on Mars will ALWAYS be scarey.

Doug

(PS - other cool docs - http://trs-new.jpl.nasa.gov/dspace/handle/2014/39907 - http://trs-new.jpl.nasa.gov/dspace/handle/2014/39871 and http://trs-new.jpl.nasa.gov/dspace/handle/2014/38898 )
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