AS-201 was the first unmanned flight Saturn IB launch vehicle. It launched February 26, 1966 at 16:12:01 UTC from Cape Canaveral's Launch Complex 34. This was not only the first flight of the Saturn IB rocket but the first real flight of a production Command and Service Module. It was a Block I version though, whereas the manned lunar missions would use the Block II.

The Saturn IB was the uprated version of the Saturn I rocket which had already flown ten times in an earlier part of the Apollo program. The main difference between the rockets was that the first stage engines produced 7.1 million newtons as opposed to 5.8 million newtons on the Saturn I. It also featured a new second stage (which was also the third stage of the Saturn V). The S-IVB could be restarted in space and featured a new hydrogen-burning J-2 engine (which would also be used on the S-II second stage of the Saturn V).

The mission profile was for the first and second stages of the rocket to launch the spacecraft into a high ballistic trajectory. The Service Module engine would then fire to accelerate the spacecraft to a high speed reentry to test the heat shield.

The first piece of the rocket to arrive at the Cape was the S-IB stage on August 14, 1965 by the barge Promise. This was built by Chrysler and featured eight H-1 engines built by Rocketdyne. The S-IVB second stage arrived next on September 18. The Instrument Unit, that would control the launch vechicle arrived October 22 and the Command Module arrived three days later and the Service Module on October 27.

The first stage was erected at the pad soon after arriving at Cape Canaveral. The second stage joined it on October 1. After fixing some problems in the Intrument Unit it was mated to the S-IVB on October 25. The CSM was mated in Boxing Day.

The first problem encountered by NASA came on October 7. The RCA 110A computer which would test the rocket, automating the process was ten days behind schedule meaning that it would not be at the Cape before November 1. This meant that by the middle of October little could be done at the pad. When it finally did arrive it continued to have problems with the punch cards and also the capacitors that didn't like operating under a protective coating. In the end however the testing the launch vehicle was still running on schedule.

Testing was running around the clock during December. Technicians were testing the CSM's fuel systems during the day and the testing was running on the rocket at night.

There was even an instance of the a variant of the Y2K bug in the computer. As it ran past midnight, when the time changed from 2400 to 0001 the computer couldn't handle it and "turned into a pumpkin" according to an interview with Frank Bryan, a KSC Launch Vehicle Operations Engineering Staff member.

In the end the testing regime slowly completed and the plugs out tests were completed proving that the rocket could function by itself.

The first launch attempt on February 25, 1968 looked as though it would be the real thing. As always there were several small delays but when the pressure in one of the fuel tanks in the S-IVB fell below the allowed limits, the onboard computer aborted the launch with 4 seconds left.

The problem was easily fixable but it was thought that it couldn't be done in the launch window. However some members of the launch team thought that it could and convinced the managers to let them run a simulated launch and 150 seconds of flight to show that the rocket could operate with the lower pressure in the fuel tank. They found it could be and the launch was de-scrubbed.

So finally after months of delays and problems, the first flight of the Saturn IB lifted off from Pad 34. The first stage worked perfectly lifing the rocket to 57 km, when the S-IVB took over and lifted the spacecraft to 425 km. The CSM seperated and continued upwards to 488 km.

The CSM then fired its own rocket to accelerate the spacecraft towards Earth. The first burn lasted for 184 seconds. It then fired ten seconds later for ten seconds. This proved that the engine could restart in space, a crucial part of any manned flight to the moon.

It entered the atmosphere travelling 8300 m/s. It landed only 37 minutes after launch, 72 km from the planned touch down point and was onboard the USS Boxer (CV-21) two hours later.

There were three serious problems found on the flight. The Service Module engine only worked properly for 80 seconds. It then started to have helium gas in the combustion chamber. Helium was used to pressurise the fuel tanks but should not have got into the combustion chamber. This was caused by a break in an oxidiser line that allowed helium to mix with the oxidiser.

The second problem was that the electrical system failed causing the command module to have to control ability during reentry. Lastly, measurements that were meant to be taken during reentry failed due to a short circuit. Both of these problems came down some bad wiring that was easily fixed.

After the flight the capsule was also used for drop tests at White Sands Missile Range. It is now on display at the Strategic Air & Space Museum, Ashland, Nebraska.

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