PhantomWolf
Penultimate Amazing
- Joined
- Mar 6, 2007
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- 21,203
Actually I thought I should clear this up a bit. The path the CSM/LM took to the moon was called a Patched Conic Section Orbit. Interestingly this is actually described the path exactly in its name, but I try and explain it further.
All orbits can be described by passing a Plane through a Cone and looking at the resulting intersection, as is shown in the image below.
With the Apollo trajectory, it was described as a Patched Conic Section, in other words, we take two conic sections, split them up into parts and then patch those parts together to form the orbit shape. As a result we get something that looks like the following image:
Not actually a straight line, but rather parts of two ovals joined together.
The real issue with Fetzer's statement is not that the craft didn't go almost directly there (although it didn't), but rather the assumption that the craft maintained a constant velocity of 25,000 mph in both directions. This is not factual. While the Saturn IVB booster accelerated the craft to 25,000 mph, as soon as that booster cut out, the Earth started to accelerate the craft back towards it, slowing it down. This continues throughout the entire trip. Finally, other manoeuvres (such as the docking with LM and the moving away from the Sat-IVB) influence the coasting speed. So we have three factors that Fetzer had not taken into account for. Firstly that the Vector component of the velocity is neither directly at the moon, nor towards the meeting point, but rather along a conic trajectory, secondly, that the Earth's gravity slows that craft down, reducing the velocity towards the meeting point as the craft travels, and thirdly that the craft did various manoeuvres which slowed it down as well. All of these things are what result in the three day trip.