MSL Approach Phase |
MSL Approach Phase |
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#1
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![]() Merciless Robot ![]() ![]() ![]() ![]() Group: Admin Posts: 8784 Joined: 8-December 05 From: Los Angeles Member No.: 602 ![]() |
We're now 45 days from landing, so as of 23 Jun please post all comments related to the end of the transit to Mars here.
Go Curiosity!!!! -------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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#2
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Junior Member ![]() ![]() Group: Members Posts: 89 Joined: 25-January 06 Member No.: 661 ![]() |
Hi again,
Doug is correct (he seems to have the knack, me on the other hand...). There is margin well above 0.8 m/s (I forget the number but it depends a lot on surface characteristics if my memory serves). With these sorts of multi-DOF control systems, either it is coming down well within the spec or ... it won't and something is wildly wrong. Ironically the Phoenix and Viking landers could not afford to land slower due to dynamics issues with slower velocity (need for leg stroke for touchdown detection, surface-plume interaction, fuel cost, etc). However the velocity knowledge and control accuracy for Viking and Phoenix was fantastic and about the same as MSL's (in fact MSL and Phoenix both use the same inertial measurement unit (IMU) design). Because of the skycrane architecture, MSL is simply able to capitalize on the IMU and on the fact that the decent engines are a long way from the surface and wheels, that the engines are dynamically uncoupled with the rover touchdown event to allow a much slower terminal descent velocity. If we were willing to use more fuel we could probably have reduced the velocity even more, but we did not need to. The big benefit of a slower touchdown is that the rover's wheels (aka "legs") can be used as landing gear plus that slow velocity really broadens the spectrum of Mars surfaces that are considered "safe". (Of course I am wildly biased - opinions expressed are those of the co-co-co-co-inventer and do not reflect NASA/JPL/Caltech). With "somewhat controlled velocity" landing systems like MER (6 solid rockets) or "nearly controlled velocity" landing systems like Pathfinder (3 solid rockets) the landing system obviously has to be robust to a much wider range of impact velocities (let alone surface characteristics). You know I can't tell you how much fun it is to come by here (I wish I had more time!!!). I get a huge kick from the thoughtful discussions of risk, and the fun walks through memory lane (like the link that SFJCody left on Post#169 to a 1997 bulletin board about the weirdness of Pathfinder's landing system and even a discussion about my old web page on EDL I created back then - what a hoot!) In my opinion, all of these missions (especially the ones that have to land safely on Mars) are experimental vehicles and have a rather substantial element of risk. For all of the Mars lander missions I have worked on (MPF, MER, PHX and MSL) like everyone else, I am initially daunted by the vast array of all the "things that must go right". The mountain ahead seems insurmountable. But then I (we) look down at my (our) feet and move myself one step at a time, one minute detail at a time, oftentimes with insufferable pauses as we ruminate, test and argue over the safety of each tiny step, sometimes having to go backwards and find another path or add new paths that we thought would never be there. Slowly, ever so slowly and with infinite patience we gain altitude, only vaguely aware of the progress we have made. The really hard part is knowing when the mountain has been scaled. Too often it appears that the summit is ahead and we can relax, only to discover that the top is further ahead than it appears, and yet another push must be mustered. Of course the top really can NOT be seen and no one knows for certain, until it is over. I do find though that there is a feeling I get that tells me the top is there in front of me (if only I could see it). It is really a feeling that we have run out of places to put our feet. No more tests left to ponder, no more problem reports to close, no more reviews to hold, only a far away machine waiting for Mars to arrive. I think we have nearly run out of places to put our feet. Could it be that we are there? Almost, I see a couple of more places to step. Next couple of week perhaps? -Rob Manning MSL Chief Engineer and faux climber Opinions expressed are indeed those of the author and do not reflect the opinion of NASA/JPL/Caltech |
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#3
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![]() Member ![]() ![]() ![]() Group: Members Posts: 813 Joined: 8-February 04 From: Arabia Terra Member No.: 12 ![]() |
You know I can't tell you how much fun it is to come by here (I wish I had more time!!!). I get a huge kick from the thoughtful discussions of risk, and the fun walks through memory lane (like the link that SFJCody left on Post#169 to a 1997 bulletin board about the weirdness of Pathfinder's landing system and even a discussion about my old web page on EDL I created back then - what a hoot!) Awesome to know, thanks! I just recently noticed that someone has uploaded CNN's coverage of the Pathfinder landing to youtube. http://www.youtube.com/watch?v=zUaalbRC7KA http://www.youtube.com/watch?v=7Au-S-tjyiU |
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#4
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Junior Member ![]() ![]() Group: Members Posts: 89 Joined: 25-January 06 Member No.: 661 ![]() |
Awesome to know, thanks! I just recently noticed that someone has uploaded CNN's coverage of the Pathfinder landing to youtube. http://www.youtube.com/watch?v=zUaalbRC7KA http://www.youtube.com/watch?v=7Au-S-tjyiU Thank you SFJCody! You made my day. I had never seen the CNN coverage of Pathfinder coverage - at least if I did, I do not recall seeing it. (Yikes! I sounded like a DJ! But I am relieved to see that I have not aged a day! Not). There were moments that I had long forgotten. Those were happy moments. With a little luck we will have another one of those highly addicting moments. I just spent the bulk of the day discussing MSL contingency procedures we have been developing for what we would do if we lost the signal(s) during EDL and immediately thereafter (of course we are considering ODY's targeting situation that Pete talked about - but I am not concerned by it). We have generic contingencies for the rover, but we needed a special one for the EDL - Sol 0 day. There are a lot of nerve-wracking ways for the signals to cease flowing and yet still allow us to recover the rover later on. So spent half the day reviewing and refining the plan. It is amazing how much time we spend on the "negative" (i.e. things that can go wrong). It can easily get us down, but we have to do this in order to find and "mitigate" all of the risks that we face. We do this so that we can get that rush when everything works right and pages of new science text books flow down to us. Years of work trying to find all of the ways it won't work only to have what works left over. -Rob Comments are those of the author and do not represent the views of NASA/JPL/Caltech. |
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#5
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![]() Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 1465 Joined: 9-February 04 From: Columbus OH USA Member No.: 13 ![]() |
There were moments that I had long forgotten. Those were happy moments. I watched that too--it was hard to miss your smile after talking about all the pyrotechnics that went off on the 4th of July: ![]() It was an amazing thing--if I recall correctly I was at someone's house for a party and the TV was on around midnight or the wee hours (ET), showing (practically) live pictures from Mars--mindblowing. -------------------- |
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