The freight train

What about the astronauts up top? Riding a Saturn V was never a relaxing experience for the crews, but a few - usually those taking their second flight -exhibited much lower heart rates than their rookie colleagues. Bill Anders, a rookie astronaut, was part of the first crew to experience the rocket on Apollo 8. ''The thing that impressed me about the early stages of lift-off was the very positive control during the gimballing of the S-IC engines. It was very positive.'' In the initial moments of its flight, most of the weight of a Saturn V was at the bottom, particularly in the huge kerosene tank just above the engines of the first stage. The upper stages, although large, were taken up with massive tanks of relatively light hydrogen and, consequently, the centre-of-gravity of the stack was quite low, somewhere in the first stage. Bill found himself on the end of a very long lever and was able to feel the steering motions of the four outer engines at the bottom of the first stage although they were occurring nearly 100 metres below him. All the steering of the first stage was achieved by swivelling the four outer F-1 engines in response to commands from the instrument unit's computer. Roll manoeuvres were made by moving opposite engines in opposite directions to give a slight screw effect to the vehicle. Moving them in the same direction at once allowed control for pitch and yaw manoeuvres, causing the vehicle to rotate about its centre-of-gravity. Because the crew sat far away, on the opposite side of this point, they felt the vehicle's rotation doubly as it shook them from side to side. Anders had expected this from rides the crew had taken in a simulator, one that was capable of moving and shaking them while they practised their procedures but, as he noted, the simulation failed to live up to the real thing. ''In fact, it felt to me on the first stage ride like an old freight train going down a bad track.''

Later in that mission, the commander, Frank Borman, gave his impressions of the very high noise levels at lift-off to a voice tape, the contents of which were later replayed to Earth on a separate channel. ''The launch was nominal in almost every respect. There was no difficulty determining lift-off. Vibrations were noticed before the thrust came up to commit to launch, and then when the hold-down arms released, the vibration went away.'' Anders by then had firmed up his impressions of the launch. ''The thing was still rattling like a freight train as it became clear of the tower.''

Ed Mitchell on Apollo 14 concurred with Anders's observation. ''Just can't beat it, huh?" he told his crewmates. ''Just like a railroad coach in this couch,'' he added. In his post-mission debrief, Eugene Cernan on Apollo 17 even took the railway analogy right back to the start of the flight. ''You could feel the ignition. You could feel the engines come up to speed. Ignition was like a big old freight train sort of starting to rumble and shake and rattle as she lifted off.''

The crew of Apollo 16 had similar recollections at their debrief as John Young brought up the next subject to talk about: ''S-IC Ignition?'' ''Wow!'' was Charlie Duke's instant reaction. ''Wow is right,'' Young agreed. ''There goes a train that is leaving. Lift-off - you can tell lift-off because everything is moving.'' Duke elaborated further: ''It is like an elevator slowly lifting off. It just kept shaking at the same frequency throughout the whole S-IC burn. You felt yourself going faster and faster and faster. I had the feeling it was a runaway freight train on a crooked track, swaying from side to side. That was all the way through the first stage.''

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