[2] The critical decision to use LOR was viewed as vital to ensuring that man reached the Moon by the end of the decade as proposed by President John F. Kennedy.

Some engineers were concerned about the risks of space rendezvous, especially in lunar orbit, where there would be no fallback options in case of a major mishap.

[21] After Houbolt presented the LOR concept to a series of dismissive high-level panels, he ignored the chain of command and complained in a long letter dated November 15, 1961, to Associate Administrator of NASA Robert Seamans that his proposal had been derided as "a scheme that has a 50 percent chance of getting a man to the moon and a 1 percent of getting him back.

"[22] Indeed, at one of the earliest NASA panels on December 14, 1960, Houbolt was attacked in the presence of both Seamans and Wernher von Braun by fellow engineer Max Faget, who announced, "His figures lie.

[11] While some aspects of Houbolt's initial estimates were off (such as a 10,000 pound Apollo Lunar Module which was ultimately 32,399 lb (14,696 kg)), his LOR package proved to be feasible with a single Saturn V rocket whereas other modes would have required two or more such rocket launches or a rocket much heavier than the Saturn V to lift enough mass into space to complete the mission Leading up to the first mission of the Space Shuttle, STS-1, in 1981 Houboult co-wrote a letter[23] with structural engineer Holt Ashley to Chris Kraft, director of Johnson Space Center, imploring him to delay the launch believing the orbiter would suffer major loss of thermal protection tiles, and potentially lose the vehicle.

While the tiles had been an ongoing concern since the original development of the Shuttle, the teams involved believed it was safe to fly by that point.

On reaching orbit some tiles were visibly missing around the tail of the Shuttle, and fears that the more-critical tiles on the underside of the vehicle were damaged led to a hastily arranged effort to use KH-11 KENNEN spy satellites and the Kuiper Airborne Observatory to acquire imaging of the Shuttle in orbit to assess the damage.