RocketRon wrote: ↑Sat Jul 30, 2022 5:41 am
Amazing view. Not many folks will have seen that !
I've always wondered how did they calculate the dynamics of rising off the moons surface and catching up/docking with the lunar orbiter.
There would only be a small margin of error for that to succeed ?. And a large possibility of missing ??
If they were a degree or 2 off on the takeoff, or a few minutes too late, their paths may never intersect ???
Great to imagine those steel-nerved space men!
Astronauting has, at least thus far, been a very hazardous profession.
Thinking about your comment, I did some web surfing and ended up at this document:
NASA Technical Memorandum TM X-58040 "Apollo Lunar Descent and Ascent Trajectories"
John C. Houbolt worked out the main concept and Floyd Bennett and Thomas Price provided further study.
The mission planning documentation shows a lot more attention given to the descent to the lunar surface than to the ascent from the surface. The way they had things worked out, the landing was the harder part. And it had abort contingencies in its planning, which is one of the reasons it shows much more planning evidenced in the documentation. For the ascent phase, there is no abort option!
Happily, for Apollo 11, nothing weird happened on touchdown, so Tranquility Base was sitting straight and solid on a good horizontal surface. And the ascent module engine fired smoothly and ascent went beautifully according to plan. If I read it correctly, once they got into lunar orbit near the Command Module and in the right orbital parameters in the right plane, then they had some propellant to spare in their RCS system and docking was easily managed.
The most unnerving part that happened (that I read in the documents) was during the final phase of the landing, about 400 feet off the surface:
As they were clearing West Crater and approaching the intended landing area, a voltage problem caused an alarm to sound on the guidance computer. It continued to perform priority calculations and everything was okay, but the alarm distracted the crew momentarily. By the time they were reoriented and looking at their landing surface, they had moved over a rough, rocky area. At that point, Armstrong took manual control and flew past the rough terrain. By the time he landed, fuel was getting low.
Another thing I learned while looking around these docs --
James Meador set about to calculate/estimate where the Eagle might have crashed back down to the lunar surface, to see if its remains could be located. In this paper: https://arxiv.org/abs/2105.10088
he came to the surprising conclusion that it is very likely still orbiting the moon!