[X] My Assistant

[toddbronco2]

The view from the High Bay viewing gallery this morning.

[nprev]

[MahFL]

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.

[djellison]

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."

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%?