provided a mating structure between the SM and the S-IVB's Instrument Unit, with a structural stiffener substituted for the LM. The launch escape system was jettisoned after S-IVB ignition, while the SLA was left behind on the spent S-IVB when the CSM separated from it in orbit. Following the Apollo 1 fire, the BlockII CSM was extensively redesigned—more than 1,800 changes were recommended, of which 1,300 were implemented for Apollo7. Prominent among these was the new aluminum and fiberglass outward-opening hatch, which the crew could open in seven seconds from within, and the pad crew in ten seconds from outside. Other changes included replacement of aluminum tubing in the high-pressure oxygen system with stainless steel, replacement of flammable materials with non-flammable (including changing plastic switches for metal ones) and, for crew protection in the event of a fire, an emergency oxygen system to shield them from toxic fumes, as well as firefighting equipment. After the Gemini 3 craft was dubbed Molly Brown by Grissom, NASA forbade naming spacecraft. Despite this prohibition, Schirra wanted to name his ship "Phoenix," but NASA refused him permission. The first CM to be given a call sign other than the mission designation would be that of Apollo 9, which carried a LM that would separate from it and then re-dock, necessitating distinct call signs for the two vehicles. Launch vehicle Since it flew in low Earth orbit and did not include a LM, Apollo7 was launched with the Saturn IB booster rather than the much larger and more powerful Saturn V. That Saturn IB was designated SA-205, and was the fifth Saturn IB to be flown—the earlier ones did not carry crews into space. It differed from its predecessors in that stronger propellant lines to the augmented spark igniter in the J-2 engines had been installed, so as to prevent a repetition of the early shutdown that had occurred on the uncrewed Apollo 6 flight; postflight analysis had shown that the propellant lines to the J-2 engines, also used in the Saturn V tested on Apollo6, had leaked. The Saturn IB was a two-stage rocket, with the second stage an S-IVB similar to the third stage of the Saturn V, the rocket used by all later Apollo missions. The Saturn IB was used after the close of the Apollo Program to bring crews in Apollo CSMs to Skylab, and for the Apollo–Soyuz Test Project. Apollo