MSL Cruise Phase |
MSL Cruise Phase |
Nov 26 2011, 03:50 PM
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Merciless Robot Group: Admin Posts: 8789 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Okay, we're off and running! Please post all comments relating to MSL's transit to Mars here.
-------------------- 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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Nov 30 2011, 08:17 PM
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Member Group: Members Posts: 206 Joined: 14-April 06 From: Seattle, WA Member No.: 745 |
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." "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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Nov 30 2011, 10:33 PM
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Founder Group: Chairman Posts: 14448 Joined: 8-February 04 Member No.: 1 |
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 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 |
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