AS-201

• 1. Introduction

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  AS-201 lifted off from Pad 34 on the 26th of February 1966, and it was over in 37 minutes. The spacecraft splashed down in the south Atlantic Ocean, and within two hours it was on board an aircraft carrier. Short as it was, that suborbital hop carried stakes that few missions its size had ever carried. It was the first time an entire production Block I Apollo command and service module flew on a Saturn IB. The heat shield worked. The engine restarted in space. And yet three things went wrong. What exactly was being tested that day, what broke, and why did a 37-minute flight matter so much to the program that would eventually send people to the Moon?

• 2. The Spacecraft

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  CSM-009 was not a complete Apollo spacecraft by later standards. Its designers built it before the decision to use lunar orbit rendezvous, so it had no ability to dock with a lunar module. Block I was also heavier than the Block II version that would carry crews to the Moon, and it used preliminary designs for several subsystems. CM-009 was the second production Block I command module to fly; the first had been CM-002, launched on a Little Joe II rocket for the final abort test of the launch escape system, a mission designated A-004.

  CM-009 differed from a fully configured spacecraft in notable ways. It was missing the guidance and navigation system along with crew couches, displays, and associated equipment. In their place were a control programmer and an open-loop emergency detection system, tools suited for an unmanned test rather than a crewed flight.

  SM-009 was the first production Block I service module to fly. Its fuel cells, which would normally generate electrical power, were replaced with batteries. The S-band communication equipment was also removed. The flight also carried the first example of the Spacecraft-LM adapter, the conical structure that connected the spacecraft to the launch vehicle and would later cradle lunar modules on Saturn V missions.

• 3. The Saturn IB

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  Saturn IB was itself a new machine, an upgraded descendant of the Saturn I that had flown in ten earlier Apollo missions. Its first stage engines were uprated to raise total thrust from 1,500,000 lbf to 1,600,000 lbf. The more significant change was the second stage, now an S-IVB burning liquid hydrogen through a J-2 engine, the same engine that would power the S-II second stage of the Saturn V.

  A modified S-IVB, carrying a restartable J-2 for use in space, would become the third stage of the Saturn V as well. The Saturn IB also introduced a new Instrument Unit for guidance and control, a system that would be carried forward onto the Saturn V. AS-201 was therefore testing hardware that would fly on the rocket designed to reach the Moon.

• 4. Getting to the Pad

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  The first piece of the rocket to arrive at Cape Kennedy was the S-IB stage, delivered on the 14th of August 1965 by the barge Promise. Chrysler had built that stage, and its eight H-1 engines came from Rocketdyne. The S-IVB second stage arrived on the 18th of September, followed by the Instrument Unit on the 22nd of October, the command module three days later, and the service module on the 27th of October.

  Stacking proceeded steadily, though not without friction. An RCA 110A computer that would automate rocket testing arrived ten days behind schedule, leaving technicians with little they could accomplish at the pad through the middle of October. When the computer finally arrived it kept failing, first with its punch cards and then with capacitors that did not perform reliably under their protective coating. By December, crews were running tests around the clock, fuel system checks on the command module during the day and rocket tests at night.

  One incident stood out among the testing stories. As the computer crossed midnight, transitioning from 2400 to 0001, it could not handle the changeover and locked up. Frank Bryan, a Kennedy Space Center Launch Vehicle Operations Engineering staff member, later described this as the computer turning into a pumpkin. The issue was a foretaste of the kind of software edge cases that would occupy engineers for years. Despite everything, testing finished on schedule, and plugs-out tests confirmed the rocket could operate independently.

• 5. Launch and Flight

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  The first launch attempt on the 26th of February 1966 nearly ended before it began. Several small delays accumulated, and then, four seconds before liftoff, the onboard computer aborted the launch because pressure in one of the S-IVB fuel tanks had dropped below acceptable limits. Engineers determined the problem could be fixed, but initially believed there was not enough time left in the launch window. A simulated launch and 150 seconds of simulated flight showed the rocket could operate at the lower pressure, so the countdown was reinstated.

  When AS-201 finally lifted off from Pad 34, the first stage performed without fault, carrying the vehicle to 57 km before the S-IVB took over and pushed the spacecraft to 425 km. The command and service module then separated from the adapter and climbed further to 488 km. The service module engine fired for 184 seconds on its first burn, then again for ten seconds on a second burn. That second ignition was not incidental: restarting an engine in the vacuum of space was a requirement for any mission that would send people around the Moon. Re-entry came at 8,300 meters per second. Splashdown followed 37 minutes after launch, landing 72 km from the planned touchdown point.

• 6. What Went Wrong

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  Three failures marked the flight, and all three were consequential enough to be catalogued as problems rather than minor anomalies. The service module engine ran properly for only 80 seconds before helium pressurant gas entered the combustion chamber and interrupted the burn. Helium was used to pressurize the fuel tanks and was never meant to reach the combustion chamber. Investigators traced the intrusion to a break in an oxidizer line that let helium mix with oxidizer before it reached the engine.

  The second problem was an electrical failure that stripped the command module of steering control during reentry. The third was a short circuit that prevented planned measurements from being recorded during reentry. Both of these were traced to incorrect wiring. The investigation found them straightforward to correct, but their presence on the first flight of an entire vehicle stack illustrated how much refinement remained ahead. After the flight the capsule was taken to White Sands Missile Range for drop tests before eventually going on display at the Strategic Air Command and Aerospace Museum in Ashland, Nebraska.