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Preparing for launch
MahFL
post Jun 29 2011, 10:46 AM
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I have few of questions about the desent stage thrusters.
Are all 8 used in the landing ?
Why are the thrusters in each pair pointing in different directions ?
What happens if the thrust is not enough ?


Thanks.

Also I read the thrusters run at 107 %, which seems an odd figure to me.
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paxdan
post Jun 29 2011, 11:20 AM
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Yes
For stability
Lithobraking

100% is the original engine rating. 107% represents a 7% performance increase over the original design spec.
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MahFL
post Jun 29 2011, 11:29 AM
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I assume safe landing could be made with less than 100 % thrust, and any extra needed then would be available ?
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centsworth_II
post Jun 29 2011, 01:05 PM
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QUOTE (MahFL @ Jun 29 2011, 05:46 AM) *
I have few of questions about the desent stage thrusters.
Just going by the animation, all eight thrusters are firing at release from the back-shell but the four inner ones shutdown shortly thereafter. I only see the outer four thrusters firing from then on even at descent stage flyaway. I also don't see any movement of the nozzles so their orientation looks fixed. But all I know is what I see in the video.
Attached Image


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djellison
post Jun 29 2011, 01:51 PM
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QUOTE (MahFL @ Jun 29 2011, 03:46 AM) *
I have few of questions about the desent stage thrusters......


This document has much of the info you require... it has been linked to before from this forum. Anyone serious about understanding MSL EDL would find it via google quite easily.
http://trs-new.jpl.nasa.gov/dspace/handle/2014/41629

In particular

"Beginning at an altitude of approximately 50 m above the surface, the PDV begins the constant deceleration segment. During this sub-segment, the PDV is decelerated from 20 m/s to 0.75 m/s. This is done at a constant deceleration rate
roughly equivalent to 90% throttle setting......
Throttle Down
At this point in the landing sequence, more than half of the initial 400 kg of fuel has been consumed. In order to maintain thrust equal to weight, the MLEs would need to be throttled back to thrust levels on the order of 20-25%. Since the MLEs operate less efficiently at these throttle settings, four of the MLEs are throttled back to their near- shutdown condition of 1%. This allows the four remaining MLEs to function in the more efficient range of 50% throttle.
The transition from eight to four MLEs introduces disturbances to the system. Therefore, a 2.5 second period of time is allotted for the disturbances to settle allowing for predictable and stable conditions for the next major segment of the landing: Sky Crane."


QUOTE
What happens if the thrust is not enough


Then the project doesn't get through Preliminary Design Review. That was about 5 years ago. What a strange question.

107% sounds like the Space Shuttle thrust level. Where did you read that the MSL MLE's would be running at 107%?
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MahFL
post Jun 29 2011, 02:52 PM
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It was a wrong assumption by me the thrusters would be running full tilt all the time.
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djellison
post Jun 29 2011, 03:05 PM
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How could that possibly work anyway - the vehicle is always getting lighter and needs to come to a near hover for the sky-crane phase.

Even Phoenix, which had constant thrust engines, pulsed them to manage the total 'thrust' provided.
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g4ayu
post Jul 18 2011, 06:28 PM
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Looks like a lot of activity at the Cape today.
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peter59
post Jul 29 2011, 07:40 PM
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Mars Science Laboratory's page is slightly changed. Changes are not great, but quite important.
http://mars.jpl.nasa.gov/msl/
If anyone did not noticed, here is the most important fragment of new page.
Attached Image

Seriously, I did not know that the launch date is so precisely determined. 118 days, when will it be? Nov 24 ?


--------------------
Free software for planetary science (including Cassini Image Viewer).
http://members.tripod.com/petermasek/marinerall.html
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djellison
post Jul 29 2011, 08:00 PM
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QUOTE (peter59 @ Jul 29 2011, 12:40 PM) *
Seriously, I did not know that the launch date is so precisely determined. 118 days, when will it be? Nov 24 ?


Each launch opportunity, within the launch window, is calculated to the second, years in advance.
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Lewis007
post Aug 2 2011, 07:54 AM
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The first and Centaur stages of the Atlas-V rocket (to be used for the MSL launch) have arrived at KSC.
Pictures available at the KSC gallery page http://mediaarchive.ksc.nasa.gov/
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sgendreau
post Aug 2 2011, 03:37 PM
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QUOTE (peter59 @ Jul 29 2011, 12:40 PM) *
Seriously, I did not know that the launch date is so precisely determined.


The EDL team's common area has two large countdown clocks, one to launch, one to landing. Both count down by seconds. Flick flick flick flick....
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Drkskywxlt
post Aug 4 2011, 11:25 PM
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Just got to see and stand near MSL's engineering model at JPL and it is AWESOME! Beast of a thing.

Was interesting to find out that it's actually run off the batteries the whole time and the RTG just keeps the battery fully charged. Tour was by Scott Maxwell and one of the project scientists...the scientist said 14-16 years of operations is certainly possible...as is driving OUT of Gale. Now let's just launch and land this thing smile.gif
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pospa
post Aug 7 2011, 01:05 PM
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Whose was this idea? Somebody we know here? rolleyes.gif
Bender as "Official Unofficial MSL Mascot" at KSC Payload Hazardous Servicing Facility.
Good choice, I love it ! biggrin.gif

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cIclops
post Aug 8 2011, 04:45 PM
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Video of Curiosity flight hardware being prepared for launch at KSC with detailed views of the arm and mobility system: http://www.youtube.com/watch?v=aEhfEZZhKa0


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