Borman argued with test pilot Scott Crossfield, who was in charge of safety engineering at North American, over the design of an effective emergency oxygen system. Borman refused to accept the design because it did not protect the crew from noxious fumes. Crossfield then opposed the delivery of North American's S-II, the second stage of the Saturn V Moon rocket, which Crossfield deemed unsafe. Borman informed management at North American that he could not work with Crossfield, and Crossfield eventually left the company. A redesigned hatch that allowed the astronauts to exit within seconds instead of minutes added to the weight of the spacecraft. The parachutes had to be redesigned to ensure they could hold the additional weight, and re-testing them cost $250,000. This led to a clash with George Mueller, who thought the cost was excessive.