Apollo 6 (AS-502)
At 7:00 a.m. on 4 April 1968, the Saturn V AS-502 rose thunderously from its Florida launch pad to boost
Apollo 6 into orbit, but that was just about the last normal thing the big rocket did.
For the first two minutes, the five huge F-1 engines in the first stage roared, shook the ground, and
belched fire evenly. Then there were thrust fluctuations that caused the vehicle to bounce like a giant pogo
stick for about 30 seconds. Low-frequency modulations (known as the pogo effect) as high as 0.6g were recorded in the command module, which exceeded design criteria (0.25g was the
upper limit permitted for manned flight in Gemini). Except for the bouncing and the loss of a piece of the
panel in the adapter (which held the Lunar Module or the mock up of one in this flight), the first stage did
its job, however.
Not long after the first stage dropped away and the second stage started burning, 2 of the 5 J-2 engines stopped. This meant the other 3 had to burn longer to get the required altitude, but the S-II ran out of fuel and it too then dropped away. To get the speed they wanted they also had to burn the third stage (S-IVB) longer than originally planned. It didn't make it into the orbit they wanted but it would have to do
The next thing was to light the S-IVB J-2 engine again to simulate a de-orbit burn to put it on course for the moon. But the S-IVB refused to re-ignite. The only thing to do now was to separate the CSM from the now dead S-IVB.
The main obectives for this flight were to test the seperation of the stages, test the electrical systems and speed simulation from a lunar return. With the rest of the objectives for Apollo 6 now unattainable, mission control turned to an alternative mission. They burned the Service Module engine for a lot longer than its Lunar requirements, this then produced the simulated Trans lunar injection manoeuvre that the S-IVB should have done. While this gave the spacecraft enough altitude to simulate a returning spacecraft from the Moon, because of the long burn from the SM they no longer had the fuel to simulate the speed of the approach.
The Command Module was nearly 4500 Kilometres per hour slower than planned on its re-entry. Apollo 6's splashdown was over 80 Kilometres out from where it should have been. The U.S.S Okinawa picked it up and its 10 hour mission was over, and far from successful.
NASA's press release said "Apollo 6 had done its job well". Not quite the case though. Its mid 1968, and John F. Kennedy's pledge to put a man on the moon by the end of the decade was not looking promising. After John F. Kennedy was assassinated in 1963 NASA was very keen to fulfil his dream and his promise.
Apollo 6 had been bad! Had there been any astronauts inside, they would have been killed by the Pogo Effect the LM adapter was shook so hard a chunk came of during launch. Engines cut-out, didn't start and didn't restart. It was bad.
NASA was working on an alphabet system. A-G, G being a manned landing on the Moon. Its 1968 and so far NASA had launched 2 "A" missions (Saturn V) and a "B" mission (Saturn 1-B).
Mission Number Objective Vehicle Trajectory Duration
======= ====== ========= ======= ========== ========
A 4+6 Launch vehicle, Saturn V 16,600-km About
spacecraft development, apogee 8.5
lunar-return entry hours
B 5 Lunar module development, Saturn 1-B Low About
propulsion and staging elliptic 6 hours
C * Command and service Saturn 1-B Low earth Up to
module evaluation crew orbit 11 days
D * Lunar module evaluation Saturn V Low earth Up to
command and service or dual 1-B orbit 11 days
modules crew performance
E * Command and service Saturn V High Up to
modules lunar module earth 11 days
combined operations orbit
F * Lunar mission deep Saturn V Lunar Up to
space evaluation orbit 11 days
G * Lunar landing
* Mission number dependent on success in steps A and B.
Although the CSM for Apollo 6 had no objectives to fulfil. it was assigned a Block I with many Block II fixes. It was also fitted with a 70mm camera. Apollo 6 was able to take some very good photos of the Earth despite all its problems.
With the failure of the Saturn V launcher of Apollo 6, NASA was not sure what to do about Apollo 7. Apollo 4 was a success as was Apollo 5. But still, they had to get a manned mission completed, which was a big step in morale and maybe budgets after Apollo 1. They might be able to skip a letter to get to the all important G a little quicker. NASA had some thinking to do.