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#1
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What happened?
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. |
#2
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What happened?
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. Is this your personal guess or the first outcome of the investigations? Boeing made that mistake as well... Turkish Airlines 1951 |
#3
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What happened?
JF Mezei wrote:
On 2016-10-22 16:54, 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. Pardon my ignorance, but which accident are you refering to ? I'm sure he's talking about the recent failure of the European Mars lander. -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn |
#4
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#5
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What happened?
Le 22/10/2016 à 23:11, Rob a écrit :
Boeing made that mistake as well... Turkish Airlines 1951 Yeah, a bug can happen to anyone. Fortunately there wasn't anybody on board of the esa probe. Another advantage of the "toasters". Nobody was killed. |
#6
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What happened?
Le 23/10/2016 à 08:39, Fred J. McCall a écrit :
JF Mezei wrote: On 2016-10-22 16:54, 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. Pardon my ignorance, but which accident are you refering to ? I'm sure he's talking about the recent failure of the European Mars lander. Well of course. And all this is just personal speculation since I have no access to any esa data. But it looks awfully like that. |
#7
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What happened?
Le 23/10/2016 à 15:40, Jeff Findley a écrit :
Seems awfully silly. All bugs are that: stupid mistakes. ESA was able to land on Titan, and now they are unable to land on Mars. Why not copy the opportunity/spirit design? It was robust and very simple. |
#8
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What happened?
Le 23/10/2016 à 15:40, Jeff Findley a écrit :
Sounds like a possibly. But designing the thing to have a single point of failure like this? Seems awfully silly. If you look he http://www.esa.int/var/esa/storage/i...images/2016/02 /exomars_2016_schiaparelli_descent_sequence_16_9/15826994-1-eng-GB/ExoMars_2016_Schiaparelli_descent_sequence_16_9.jp g you see that radar turns on after the heat shield separates. If that radar sent a wrong altitude to the software... mission was doomed to failure. P.S. CAREFUL with the URL being cutted in pieces by the old USENET system. |
#9
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What happened?
JF Mezei wrote:
On 2016-10-23 18:15, jacob navia wrote: http://www.esa.int/var/esa/storage/i...images/2016/02 /exomars_2016_schiaparelli_descent_sequence_16_9/15826994-1-eng-GB/ExoMars_2016_Schiaparelli_descent_sequence_16_9.jp g Sometimes, it has to be "learned". Airbus had fancy software on its A320 to protect against accidental deployment of spoilers and thrust reversers. (which had caused some crashes in the past). It required the nose wheel to spin AND pressure switch indicating wheight on the wheel. Problem happened when plane landed during storm, and hyroplaned, so nose wheel did not spin and pilot unable to deploy spoilers/thrust reversers. They likely changed the "and" to a "or". 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" ? 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. When the radar does not work correctly so there is no correct height figure available, there probably will be no correct vertical speed figure either (which is likely derived from the changing height). In Turkish Airlines 1951 the radar altimeter was defective and indicated a constant value near zero, which caused the plane to flare and the engines to go to idle while it was still 300ft in the air. Curiously there were redundant altimeters (radar and barometric) but only the value of a single radar altimeter was used for this function even when it is defective. Clearly a design error. Redundant hardware also isn't always the solution, especially when it is identical and running the same software. See Ariane 501. |
#10
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What happened?
jacob navia wrote:
Le 23/10/2016 Ã* 15:40, Jeff Findley a écrit : Seems awfully silly. All bugs are that: stupid mistakes. ESA was able to land on Titan, and now they are unable to land on Mars. Why not copy the opportunity/spirit design? It was robust and very simple. It looks like this was an attempt to land a device with much higher mass. It seems like this one was very heavy for what it was intended to do on the surface, they wanted to experiment for the next mission which intends to land a much larger rover. |
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