20

24 people have gone around the Moon on nine Apollo missions (8, 10-17). 3 of those 24 were repeat visitors. I'm not sure if Apollo 13 saw the sight you describe, but all of the others surely did. Apollo 13 only had one chance, and they probably had other things on their minds at that time. Although according to the official transcript, someone said "...


14

I concentrate on Earthrises documented by Hasselblad images. The Apollo 8 earthrise image is part of the question. An Apollo 10 CM photo AS10-27-3888 called Earthrise from lunar orbit. Earthrise as seen from the Apollo 11 CM AS11-44-6547: Another Apollo 11 image AS11-37-5441 taken from the LM: So we got earthrise images from both the Apollo 11 LM and CM. ...


8

Apollo missions 8, 10, and 11 were free-return trajectories, but this greatly limits the choice of landing sites. From Apollo 12 onward, the initial trajectory was a highly elliptical orbit that did not reach the Moon (technically suborbital: the perigee was inside the Earth's atmosphere); once everything checked out, a mid-course correction was used to put ...


7

Apollo 8 was on a free-return trajectory when approaching the moon. If there was a no-go for the lunar orbit insertion, or if the engine failed to fire, they would have returned to Earth needing only minor course correction (doable with the RCS thrusters, which had a terrific amount of redundancy) to get home. Via Americaspace.com: During the translunar ...


6

The Apollo missions braked directly into near-circular orbit around the moon at about 100km altitude, with a 2-hour orbital period, and remained there with various small alterations for the duration of the lunar stay (2-6 days, 25-70 orbits). These were always retrograde orbits; the spacecraft passed the "leading edge" of the moon, which slows the orbit in ...


6

Apollo 13 was not on a free return trajectory when the explosion happened, in order to target their landing site. They had to execute a 30-second burn of the Lunar Module engine to get on a free return trajectory. So, yes, it was planned to not be on a free return for much of the Apollo 13 trajectory. So that must count as "ever".


3

Let's start with the easy bits. The distance from the center of the Moon at the far point. The max distance that the Moon was from Earth was actually at the exit point. The exact distance involves some complex geometry. Another thing to keep in mind is the Earth and Moon are not exact spheres, the radius can vary quite a bit. The Earth's actual radius can ...


3

Animal maintenance over a long time period is next to impossible to be automated with current technology. Humans need to be there to manage the animals. Short term, small animals, sure. But problems crop up. You know how they say "Kids do the darnest things." Animals are worse. A free return Mars mission is a 2 year mission as I recall (6 months there, ...


2

It would certainly be possible. However it would cost a great deal - less than a manned flight but still expensive. We also wouldn't learn much - humans have already flown in space for over a year (Mir astronauts) in low earth orbit and we now know more about the radiation risks in the space between the planets. However; if anyone ever runs an unmanned ...


2

The Apollo missions are the only manned missions thus far to leave Earth's orbit, and as such are the only ones for which a "free return" (to Earth) trajectory has meaning. (As noted by Mark Adler, the Apollos didn't normally fly free-return trajectories, but could easily get on such trajectories.) For near-Earth missions, a "free return" to Earth means a ...


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