did take place over the years of the program from lessons learned and the emphasis on quality control got tighter as time went along; the last two Mercury flights were given a level of testing and pre-flight inspection that was unheard of when Big Joe flew in 1959. All launch vehicles would have to be complete and fully flight-ready at delivery to Cape Canaveral with no missing components or unscheduled modifications/upgrades. After delivery, a comprehensive inspection of the booster would be undertaken and prior to launch, a flight review board would convene to approve each booster as flight-ready. The review board would conduct an overview of all pre-launch checks, and hardware repairs/modifications. In addition, Atlas flights over the past few months in both NASA and Air Force programs would be reviewed to make sure no failures occurred involving any components or procedures relevant to Project Mercury. The NASA Quality Assurance Program meant that each Mercury-Atlas vehicle took twice as long to manufacture and assemble as an Atlas designed for uncrewed missions and three times as long to test and verify for flight. Systems modified Abort sensor Central to these efforts was the development of the Abort Sensing and Implementation System (ASIS), which would detect malfunctions in the Atlas's various components and trigger a launch abort if necessary. Added redundancy was built in; if ASIS itself failed, the loss of power would also trigger an abort. The ASIS system was first carried on a few Atlas missile R&D flights, then flown open loop on Mercury-Atlas 1, meaning the ASIS could generate an abort signal but not send a cutoff command to the propulsion system. It was operated closed-loop on MA-3 for the first time. The Mercury launch escape system (LES) used on Redstone and Atlas launches was identical, but the ASIS system varied considerably between the two boosters as Atlas was a much larger, more complex vehicle with five engines, two of which were jettisoned during flight, a more sophisticated guidance system, and inflated balloon tanks that required constant pressure to not collapse. Big Joe and MA-1 had no escape tower, the latter's in-flight failure was possibly due to the lack of the LES negatively affecting its aerodynamic profile and so MA-2 carried a dummy tower. A live LES was carried for the first time on MA-3 (and ended up proving its functionality in an unplanned test). Atlas flight test data