STS-121 - Pre-launch Concerns

Pre-launch Concerns

Following the flight readiness review meeting which concluded on 17 June 2006, NASA's Chief Engineer Christopher Scolese and Bryan O'Connor, who served as pilot on STS-61-B and commanded STS-40 and who is now NASA's Chief Safety and Mission Assurance Officer, decided that from their point of view they were going to recommend that the shuttle not be flown. O'Connor later expanded this to explain that this is due to the potential for the loss of the vehicle; he supports the collective decision to fly, however, especially given the option for the crew to stay on the ISS and await rescue if the shuttle is unable to return to earth. Both Scolese and O'Connor included notes explaining their position in their entries in the official plans.

Statement by Scolese and O'Connor as released by NASA

"Crew safety is our first and most important concern. We believe that our crew can safely return from this mission.

"We both feel that there remain issues with the orbiter – there is the potential that foam may come off at time of launch. That's why we feel we should redesign the ice/frost ramp before we fly this mission. We do not feel, however, that these issues are a threat to safe return of the crew. We have openly discussed our position in the Flight Readiness Review – open communication is how we work at NASA. The Flight Readiness Review board and the administrator have heard all the different engineering positions, including ours, and have made an informed decision and the agency is accepting this risk with its eyes wide open."

NASA's public affairs office had said following the flight readiness review that O'Connor and Scolese would not talk to the media about their objections. On 20 June it was reported that O'Connor was readily agreeing to interviews and also said the statement was actually written by the public affairs office and agreed by the two officials.

On the morning of the first launch attempt, on 1 July, concerns included weather, external fuel tank foam, and a thruster failure. The thruster failure was detected via abnormally low thermostat readings in one of the left Orbital Maneuvering System (OMS) pods. The thruster in question – L5L, one of 38 – is now considered inoperable. The plan is not to fix the problem, but to ensure that any reduction in maneuverability resulting from the failure is within the limits that the crew can cope with on orbit. Thruster L5L became operational again after mission managers decided to use sunlight to warm up the thruster to normal operational levels and it was able to be used during the docking procedures with the ISS.