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MSL Cruise Phase
Ron Hobbs
post Nov 30 2011, 08:17 PM
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From what I thought was a very informative article in the January 2011 issue of Aerospace America from the AIAA:

"Things begin to happen fast at backshell and parachute separation, but the first thing the sky crane and Curiosity do is nothing." ohmy.gif "The contraption is programmed to free-fall for 1 sec to be well clear of the ... parachute canopy, risers, and backshell."

"Next (after MLE ignition) the vehicle maneuvers laterally to prevent having the backshell and parachute collide in midair or land on top of each other - the worst of luck 150 million miles from Earth."

This may have changed, although some kind of collision avoidance must still be included.

Ron
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djellison
post Nov 30 2011, 10:33 PM
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Ron - as far as I know, that article has it about right. (Apart from semantics of MLE fire up.... they're just warming up at 1% before the drop)

http://trs-new.jpl.nasa.gov/dspace/handle/2014/41629 was our go-to document for EDL

QUOTE
At initiation of BSS, separation nuts are fired to release the PDV from the backshell. For one second, the PDV freefalls out of the backshell to provide sufficient separation to avoid inadvertent recontact when maneuvering begins. Once this one-second freefall is complete, the eight MLEs are throttled up from their 1% near-shutdown condition and the PDV begins a 2.2 second period during which any residual attitude rates from the BSS event are removed and the PDV assumes a pre-defined attitude for the beginning of powered descent...
...During Powered Approach, the PDV follows a 3-D polynomial trajectory which was computed at BSS. As the PDV follows the polynomial, horizontal velocity is smoothly brought to zero while vertical velocity is simultaneously brought to 20 m/s. The end point of the trajectory is about 100 m above the surface and 300 m perpendicular to the plane of the entry trajectory. Since the PDV is actively slowing, the parachute and backshell will actually travel past the PDV and reach the surface ahead of the PDV. The 300 m divert distance is adequate to ensure the PDV does not land on the parachute or backshell. Once the endpoint of the Powered Approach trajectory is reached, the Constant Velocity Accordion begins


So there isn't a discreet avoidance maneuver as there was with PHX ( although PHX didn't actually need it's after all ) - but avoidance is part of the mix of the trajectory design from BSS to the CVP

Enough TLA's smile.gif

Thanks John - the heavy lifting was Bohemian Grey - I just pointed them in the right direction. The BSS is the moment I'm most proud of...and showing it to the EDL team for the first time one the highlights of my short time at JPL so far. It involved a spontaneous high-five across a conference room table smile.gif
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MahFL
post Dec 1 2011, 12:23 AM
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Well I should have known better the tragectory maneuvers would not be done with a single thruster , confidence is restored smile.gif.
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Syrinx
post Dec 2 2011, 07:42 AM
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http://www.sciencedaily.com/releases/2011/...11201220357.htm

Almost entirely good news. The one small bit of unexpected news (nothing to worry about):

QUOTE
The spacecraft experienced a computer reset on Tuesday apparently related to star-identifying software in the attitude control system. The reset put the spacecraft briefly into a precautionary safe mode. Engineers restored it to normal operational status for functions other than attitude control while planning resumption of star-guided attitude control.
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stevesliva
post Dec 2 2011, 07:56 AM
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Seems to be regurgitating the same source:
http://spaceflightnow.com/atlas/av028/111201noburn.html
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MahFL
post Dec 2 2011, 03:10 PM
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The Eyes on the Solar System make my IE 8 crash after a while, does anyone have the same problem ?, says "too many heap" entries.
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B Bernatchez
post Dec 2 2011, 05:42 PM
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No problems for me (that wouldn't be fixed by a better video card). blink.gif
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djellison
post Dec 2 2011, 06:52 PM
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QUOTE (MahFL @ Dec 2 2011, 07:10 AM) *
The Eyes on the Solar System make my IE 8 crash after a while, does anyone have the same problem ?, says "too many heap" entries.


Hence the Beta label. It happens. Just don't use it too look at too much stuff before restarting it ( I know, sounds lame, but it does work ) It's a Unity plugin problem that we're looking at, but is mainly outside our control.
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Mars Attack
post Dec 4 2011, 02:57 PM
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I'm a bit concerned about the reported reset of the MSL computer and safemode due to a star tracker. If this reset had happened in the middle of the upcoming trajectory correction burn, originally schedules a week or so post anomaly, wouldn't this have been disastrous? MSL is on a course to miss Mars by 38000 miles. Could it be that the delay of this course correction might have been influnenced by this potentially serioius malfunction? If I'm wrong, please write some words of assurance. Thanks
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ElkGroveDan
post Dec 4 2011, 03:42 PM
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There is extra fuel aboard and my understanding is that due to a precise initial burn they have already delayed the first TCM by a month or so. Typically these craft are built with redundancies and contingencies built upon redundancies and contingencies. One common and predictable anomaly is not going to sink the entire mission. Chill.


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Hiwayman
post Dec 4 2011, 03:56 PM
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Sorry for this being posted in the wrong forum, but the launch topic is closed. Did anyone notice the "umbilical" or "hose like" aperture that was still attached to the fairing during launch? It was about 10' - 15' ft from the top of the nose and protruded out about 3-4 feet? Not all cameras caught it, but it was clearly visible on the camera that showed the fairing separation, and another ground based camera. Once the fairing was ejected, the aperture went with it, so it became a mute point, but it sure looked like it was something that should have been left on the ground rather than fly with the vehicle. Did anyone see it? It obviously did not affect the trajectory as it was close to perfect.
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elakdawalla
post Dec 4 2011, 04:19 PM
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Someone else pointed this out to me on the Atlas fairing on the Juno launch -- I think it's an Atlas V thing, and is normal.


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Hiwayman
post Dec 4 2011, 04:28 PM
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QUOTE (elakdawalla @ Dec 4 2011, 09:19 AM) *
Someone else pointed this out to me on the Atlas fairing on the Juno launch -- I think it's an Atlas V thing, and is normal.


Thanks, Emily!
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stevesliva
post Dec 4 2011, 04:55 PM
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QUOTE (Mars Attack @ Dec 4 2011, 10:57 AM) *
If this reset had happened in the middle of the upcoming trajectory correction burn, originally schedules a week or so post anomaly, wouldn't this have been disastrous?


Nope.
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Mars Attack
post Dec 4 2011, 05:20 PM
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QUOTE (stevesliva @ Dec 4 2011, 04:55 PM) *
Nope.

Thanks folks for the reassurance!
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