Per un punto Martin perse la cappa ( Ovvero: il difficile mestiere dell'ingegnere )

[stev66]

non so se vi ricordate che il 22 Agosto è fallita la messa in orbita di due satelliti della costellazione GPS Galileo

L' inquiry board ha finito l'analisi ed ecco quello che ha trovato: ( da russianspaceweb.com )

On October 7, following a meeting at Arianespace headquarters in Evry, near Paris, the Independent Inquiry Board announced its definitive conclusions into the August 22 Soyuz rocket failure to deliver Galileo FOC M1 satellites, the company announced on October 8.

According to Arianespace, conclusions draw on data supplied by Russian partners in the program, and are consistent with the final conclusions of the inquiry board appointed by the Russian space agency, Roskosmos. The Board's conclusions confirm that the first part of the mission proceeded nominally, which means that the three-stage Soyuz launcher was not at fault. The Inquiry Board also eliminated the hypothesis that the anomaly could have been caused by the abnormal behavior of the Galileo satellites.

The anomaly occurred during the flight of the launcher's fourth stage, Fregat, designed and produced by NPO Lavochkin. It occurred about 35 minutes after liftoff, at the beginning of the ballistic phase preceding the second

ignition of this stage.

The scenario that led to an anomaly in the orbital injection of the satellites was precisely reconstructed, as follows:

The orbital error resulted from an error in the thrust orientation of the main engine on the Fregat stage during its second powered phase;

This orientation error was the result of the loss of inertial reference for the stage;

This loss occurred when the stage's inertial system operated outside its authorized operating envelope, an excursion that was caused by the failure of two of Fregat's attitude control thrusters during the preceding ballistic phase;

This failure was due to a temporary interruption of the joint hydrazine propellant supply to these thrusters;

The interruption in the flow was caused by freezing of the hydrazine;

The freezing resulted from the proximity of hydrazine and cold helium feed lines, these lines being connected by the same support structure, which acted as a thermal bridge;

Ambiguities in the design documents allowed the installation of this type of thermal "bridge" between the two lines. In fact, such bridges have also been seen on other Fregat stages now under production at NPO Lavochkin;

The design ambiguity is the result of not taking into account the relevant thermal transfers during the thermal analyses of the stage system design.

The root cause of the anomaly on flight VS09 is therefore a shortcoming in the system thermal analysis performed during stage design, and not an operator error during stage assembly. The system thermal analyses have been reexamined in depth to identify all areas concerned by this issue.

Given this identified and perfectly understood design fault, the Board has chosen the following corrective actions for the return to flight:

Revamp of the system thermal analysis;

Associated corrections in the design documents;

Modification of the documents for the manufacture, assembly, integration and inspection procedures of the supply lines.

These measures can easily and immediately be applied by NPO Lavochkin to the stages already produced, meaning that the Soyuz launcher could be available for its next mission from the Guiana Space Center as from December 2014.

Beyond theses corrective actions, sufficient for return to flight, NPO Lavochkin will provide Arianespace with all useful information regarding Fregat’s design robustness, which is proven by 45 successful consecutive missions before this anomaly, Arianespace said

In pratica la progettazione termica errata di un supporto per le tubazioni del carburante e dell'elio liquido ha mandato a donnine allegre una missione da centinaia di milioni di euro.

Questo per ribadire che anche nella progettazione di oggetti molto più semplici , l'errore è sempre in agguato e si concretizza in modi che non erano neppure pensabili .

[Motron]

Nel lavoro del progettista è sempre dietro l'angolo... e quel che è peggio è che gli errori sono sempre visibili DOPO... qualsiasi idiota si sente in diritto di darti del pirla...

[TonyH]

L'ingegneria è una scienza empirica...è gli FMEA sono la storia

[Ampo]

Ma come è possibile che il problema non si sia mai presentato nei 45 lanci precedenti?

[AleRPM]

E' come quando a 16 anni vuoi entrare nelle grazie (e poi possibilmente sotto la gonnellina) di una tua amichetta. Mesi e mesi di duro lavoro possono essere rovinati da un nonnulla...