The vehicle's onboard guidance system compensated by burning the second and third stages longer, although the resulting parking orbit was more elliptical than planned.

Apollo 6, the second test flight of the Saturn V launch vehicle, was intended to send a command and service module (CSM) plus a Lunar Test Article (LTA), a simulated lunar module (LM) with mounted structural vibration sensors, into a trans-lunar trajectory, with the boost from orbit to trans-lunar velocity powered by the Saturn V's third stage, the S-IVB.

In contrast with Apollo 1's ill-fated CSM, which arrived with hundreds of unresolved issues, CSM-020 had only 23, mostly routine problems.

Containing no flight systems, its ascent stage was made of ballasted aluminum and instrumented to show vibration, acoustics and structural integrity.

[16] Apollo 6 saw the first use of the High Bay 3 of the VAB, and it was quickly discovered that its air conditioning facilities were inadequate.

The mobile service structure could not be moved to the launch pad for two days due to high winds.

The countdown demonstration test began on March 24; although it was completed within a week, the launch had to be postponed one more time.

[19] NASA Associate Administrator for Manned Space Flight George Mueller explained the cause to a congressional hearing: Pogo arises fundamentally because you have thrust fluctuations in the engines.

[22] During the first orbit, the S-IVB maneuvered, changing its attitude towards the horizon to qualify techniques that future astronauts could use in landmark tracking.

Then, after the standard two orbits to assess the vehicle's readiness for trans-lunar injection (TLI), the S-IVB was ordered to restart, but failed to do so.

[23] Deciding on a pre-planned alternate mission,[24] the flight director, Clifford E. Charlesworth and his team in Mission Control chose to use the SM's Service Propulsion System (SPS) engine to raise the spacecraft into an orbit with a high apogee (point of furthest distance from Earth), with a low perigee that would result in re-entry,[3] as had been done in Apollo 4.

[25] While at high altitudes, the CM was able to return data on the extent to which future astronauts would be protected from the Van Allen Belts by the skin of the spacecraft.

[27] In a post-launch press conference, Apollo Program Director Samuel C. Phillips said, "there's no question that it's less than a perfect mission", but that the launch vehicle's reaching orbit despite the loss of two engines was "a major unplanned accomplishment".

To damp pressure oscillations in the F-1 and J-2 engines, cavities in valves leading to them were filled with helium gas shortly before takeoff as a shock absorber.

Tests showed that the propellant lines leading to the spark igniters could fail in low atmospheric pressure or in vacuum.

In the vacuum of space, there was no such protection: the bellows vibrated rapidly and failed at peak flow, causing a burn-through of the propellant lines.

[28] In Apollo 6's wake, NASA engineers debated whether to configure the spacecraft's emergency detection system to automatically abort in the event of excessive pogo; this plan was opposed by Director of Flight Crew Operations Deke Slayton.

As the rocket accelerated through the atmosphere, the cells expanded due to trapped air and water, causing the adapter surface to break free.

In response, engineers drilled small holes in the surface to allow trapped gases to dissipate, and placed a thin layer of cork on the adapter to help absorb moisture.

In late April, the committee reported that the agency had quickly analyzed and diagnosed the abnormalities of Apollo 6, and had taken corrective action.

[21] The command module carried a motion picture camera, intended to be activated during launch and during re-entry.

[33] A 70 mm still camera operated in the CM during part of the mission, pointed at the Earth through the hatch window.

The camera had haze-penetrating film and filter combination, with better color balance and higher resolution than photographs taken on previous American crewed missions.