In addition to the fixed-base lunar module simulators in Houston and at the Cape, astronauts also practiced at Langley Research Center on the suspended lunar landing trainer which was equipped with realistic surface views and lighting.
The biggest concern before Apollo 9 was the docking maneuver.In early 1969, at NASA there was little confidence in the docking system. At a January program review, Phillips said that problems encountered during probe and drogue testing worried him…
The Command Module probe and the Lunar Module Drogue
McDivitt & Schweickart practice in the LM simulator
Schweickart in the spacesuit with the backpack
Lithograph print of the negative that flew on Apollo 9, with signatures of Grumman engineers and mechanics
Apollo Saturn 201 employed the Saturn IB launch vehicle, which was the up-rated version of the Saturn I rocket flown in ten earlier Saturn-Apollo missions. It featured an upgrade of the first stage engines to increase thrust from 1,500,000 lb-ft of thrust to 1,600,000 lb-ft. The second stage was the S-IVB. This stage used a new liquid hydrogen-burning J-2 engine which would also be used on the S-II second stage of the Saturn V lunar launch vehicle…
Toward the end of January 1967, it was revealed that Lunar Module 1 would not reach the Cape in February, as expected. This meant, the moon landing might be delayed because the lander was not ready. But the mission planners could not wait for the Apollo engineers to iron out all the problems. They had to plan for a landing in 1969 and hope that the hardware would catch up with them.