We've got a series of great mp3 audio clips from a telephone call with ESA's Bob Chesson with a detailed explanation on the propoulsion problem involving the PDE (Propulsion Drive Electronics) that caused excitement on Sunday evening, shortly after orbit injection. The problem's now solved, but Bob mentions what caused the issue to occur, the solution and the incredible teamwork (Astrium, ESA, CNES) behind devising and implementing the fix (click on 'Full story' to access mp3 links). -- Daniel
Admittedly, the audio is a little techie - but after all, it **is** rocket science.
ESA's Bob Chesson is located at ATV-CC in Toulouse, and as the head of the Human Spaceflight Operations team, he's watching every minute of ATV operations very closely. He has first-hand participation in all aspects of ATV activities and spoke to us yesterday on the PDE (Propulsion Drive Electronics) problem.
First off, here is Bob describing the origin of the problem. In the audio, he mentions the two propulsion reactants: "MON" and "MMH" - these are the oxidising agent, MON (mixed or modified oxides of nitrogen) and the fuel itself, Monomethylhydrazine (MMH). These are examples of so-called 'hypergolic' reactants, which ignite spontaneously when they come into contact. Due to their reliability, hypergolic systems are widely used by many spacecraft and rockets, including ATV, the Shuttle, Ariane and others.
Next, Chesson explains the fix: essentially, a set of new commands that were devised by engineers at Astrium, builders of the ATV, tested by Astrium with their engineering model of the ATV and by the ATV mission controllers using their simulation software, and then radioed up to ATV. In the audio, Chesson mentions "OMP" commands - these are Onboard Mission Plans that are uploaded to the Jules Verne computer for subsequent execution.
At the end, Chesson mentioned several times the immense teamwork displayed by everyone involved in the mission: prime contractor Astrium, ESA, CNES and ATV-CC - plus many sub-teams within these organisations. Bob mentions the Astrium engineers - they are working, in part, at the Astrium facility at Les Mureaux, France, where the contractor's core design and qualification teams for ATV are on stand-by.