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Posted by: Airbag Dec 21 2005, 03:59 AM

At the afternoon seminar on Dec 12, 2005 at the Hayden Planetarium, Steve Squyres also talked a little about MSL (he is a member of MSL's review board). I apologise if some of these notes are redundant in this forum:

- MSL's skycrane technology will be tested via a physical simulator in addition to computer simulations; quite an elaborate setup is being constructed for this purpose at JPL.

- There will be no "local" landing control, i.e. if unlucky, MSL could land right on top of a rock.

- The re-entry capsule's center of gravity will be offset from the geometric center and thus dynamic steering (a la Apollo) will be possible - and indeed required, to meet the much smaller landing ellipse [10km instead of 50km I think he said?].

Airbag

Posted by: ljk4-1 Dec 21 2005, 04:57 AM

I thought the whole point of having the skycrane was so that MSL would *not* land on top of a big rock?

Posted by: BruceMoomaw Dec 21 2005, 08:42 AM

I'm bewildered by that too -- the whole purpose of the scanning-radar landing hazard detection system (which is separate from Skycrane) is to avoid both big rocks and dangerously steep slopes. Is he saying that this has been deleted from MSL? I find that very hard to believe; it has a much firmer association with the program than Skycrane does.

Posted by: Airbag Dec 21 2005, 03:25 PM

Well, that is what he said. There was not much time for Q&A unfortunately. Perhaps it all depends on what he meant by "local" and how big "big" is? No doubt we'll learn more as MSL progresses.

Airbag

Posted by: lyford Dec 21 2005, 06:01 PM

Oh noes! Could the http://www.unmannedspaceflight.com/index.php?showtopic=765&view=findpost&p=7442 come back to haunt us?

I don't doubt what you heard, Airbag, but methinks this really must be a misstatement somehow - hazard avoidance is one of the main reasons for the new system! It would be more than tragic to have the last meter defeat you after safely completing the many millions kilometer journey.

I am slowly warming to the skycrane concept, and though I hunger for more testing details, but they would belong http://www.unmannedspaceflight.com/index.php?showtopic=765

Posted by: djellison Dec 21 2005, 09:34 PM

Perhaps what he meant is that it wont be able to navigate itself to a specific point (i.e. Land in Eagle Crater) - but it does retain the ability to find something safe whereever it DOES end up.

Doug

Posted by: RNeuhaus Dec 21 2005, 10:40 PM

MMmm... It is just the opposite. First the model must be the real ones and when it is made, then the simulation will be made according to the real input. With that input model will help to refinate and improve the defect controls. I am supossing that this first step of software simulation will yield the estimates properties before to build the skycrane and later during the real simulation will feed back the results in order to refine the landing performance.

If the MSL won't be incorporated the hazardous avoidance landing, then the most probably landing places would be MER's alike, flat, low rocks, and perhaps very few dangerous mini-craters...

Rodolfo

Posted by: Airbag Dec 22 2005, 03:25 AM

I assume he was refering to a rock big enough to damage the rover (e.g. puncture its belly or damage the wheels etc.) but not big enough to clearly see and avoid. He specifically mentioned it could land on a boulder in a bad way.

Airbag

Posted by: mars loon Dec 22 2005, 03:32 PM

I also attended the afternoon Hayden seminar and can confirm Airbags comments.

Steve specifically said there is no "local hazard avoidance". That was surpising to me also. So yes, a "big" rock could doom the mission at virtually the last second, as currently concieved, and it could land "in a bad way". (Another big reason for 2 MSL's vs 1 MSL, and a direct consequence of recent budget cuts). They will have to think long and hard about a landing site

But, Steve also said MSL will have steering jets for use at various points during the atmospheric entry for some guidance to achieve the 10 km long landing ellipse requirement (MER was ca. 60 miles).

Steve was extremely generous with his time, over 90 min. This came up at the end when there was limited time for Q&A follow-up on these highly detailed items of great interest to all of us (ie what exactly does "local" and "big" etc mean). Understandably, he had to depart for the evening seminar and some time with his hosts

we were able to engage in exciting give and take during his talk and he had tons of info to present. he was rapidly flipping back and forth between files and even asked us if we would like to hear about the newest stuff vs older stuff. We replied "new stuff". We were extremely fortuneate to be in a small conference room with him and the astrophysics staff of the Hayden

As for as the "Sky Crane" concept: The purpose is to deliver the rover directly to the surface and avoid the ca. 2 week egress cycle. This concept also allows the redistribution of the mass otherwise associated with the landing pad to the Rover, sky crane, etc. Again, we couldn't really follow up on these points and MSL was not the focus of his talk.

soon I hope to put a summary into the hayden thread along with airbag

Posted by: lyford Dec 22 2005, 04:29 PM

Thanks for your clarifications - looking forward to a "full report"