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#11
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What happened?
JF Mezei wrote:
What if the heat shield did not get out of the way and the craft got within 4m from it, triggering the radar to say "4m altitude, turn off the thrusters" ? Aerodynamics - get some. The "software" solution would have to consider vertical descent speed "do not turn off thrusters if vertical speed is greater than 4km/h no matter what altitude you're at". So the shield obstructig radar would not have caused thrusters to turn off. But as long as hield was in the way, it would have to use IMU to deduct its vertical speed and be flying bnlind. Where do you think the craft gets its vertical descent speed from? IMUs can only measure accelerations. -- "Ignorance is preferable to error, and he is less remote from the truth who believes nothing than he who believes what is wrong." -- Thomas Jefferson |
#12
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What happened?
Le 22/10/2016 Ã* 22:54, jacob navia a écrit :
Altimeter failure. The instrument indicates a much lower altitude than the real one. So, thinking they are much lower, software ejects the parachutes, then when the rockets are turned on, the altimeter tells that they have landed and software shuts down the rockets. Then it goes from there till the crash at 300Km/h with no parachute and no rockets... Single point failure. All mission relies on the altimeter. This is being confirmed by the french journal "liberation" today. The inertial altimetre that took the relay from the radar altimetre got "saturated" and stayed at its maximum value for a second. That led to the crash. The computer received a negatiuve measure (it thought it was under the soil) and started the soil sequence at 3 Km over the real martian soil. |
#13
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What happened?
On Tuesday, October 25, 2016 at 12:06:31 AM UTC+13, Fred J. McCall wrote:
JF Mezei wrote: What if the heat shield did not get out of the way and the craft got within 4m from it, triggering the radar to say "4m altitude, turn off the thrusters" ? Aerodynamics - get some. The "software" solution would have to consider vertical descent speed "do not turn off thrusters if vertical speed is greater than 4km/h no matter what altitude you're at". So the shield obstructig radar would not have caused thrusters to turn off. But as long as hield was in the way, it would have to use IMU to deduct its vertical speed and be flying bnlind. Where do you think the craft gets its vertical descent speed from? IMUs can only measure accelerations. http://web.mit.edu/digitalapollo/Doc...progreport.pdf https://www.youtube.com/watch?v=vFv-B_2OV0s https://www.youtube.com/watch?v=YIBhPsyYCiM https://www.youtube.com/watch?v=4Vf6Y98ZjwQ https://www.youtube.com/watch?v=kKIBGY2zaQg A famous user of an IMU system to travel from Earth to Moon speaks about a primitive guidance system https://www.youtube.com/watch?v=FD0jUvcMoD4 https://www.youtube.com/watch?v=xQ1O0XR_cA0 -- "Ignorance is preferable to error, and he is less remote from the truth who believes nothing than he who believes what is wrong." -- Thomas Jefferson |
#14
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What happened?
On Sunday, October 23, 2016 at 9:54:03 AM UTC+13, jacob navia wrote:
Altimeter failure. The instrument indicates a much lower altitude than the real one. So, thinking they are much lower, software ejects the parachutes, then when the rockets are turned on, the altimeter tells that they have landed and software shuts down the rockets. Then it goes from there till the crash at 300Km/h with no parachute and no rockets... Single point failure. All mission relies on the altimeter. That's why airliners have multiple altimeters on board. http://www.pmflight.co.uk/wp-content...deck_panel.jpg The pilot and co-pilot have separate altimeters and rate of climb indicators. The digital flight system has two separate radar based altimeter and rate of climb indicators on the CRTs, and the guidance computer has a separate altitude readout that can also be set to show vertical speed at the press of a button. |
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