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Apollo 8 orbited the moon, and obviously Apollo 11 landed. I'm wondering if there were any test missions to get unmanned ships to the moon and safely back to Earth? It seems like a big jump to suddenly send manned ships there.

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  • $\begingroup$ This is an interesting question and makes me wonder 1) would all of that have been possible without the Apollo guidance computer and IMU(s), and 2) would those have functioned reliably without the humans on board tending to them? $\endgroup$ – uhoh Aug 1 '19 at 1:26
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    $\begingroup$ @uhoh AGC worked well enough controlled from the ground on Apollo 4 and 6. $\endgroup$ – Russell Borogove Aug 1 '19 at 2:11
  • $\begingroup$ @RussellBorogove thanks, that's something to think/ask about ;-) $\endgroup$ – uhoh Aug 1 '19 at 3:54
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    $\begingroup$ Near duplicate of Why didn't the Apollo program do an uncrewed landing/ascent rehearsal? -- but I like my answer here better. 😉 $\endgroup$ – Russell Borogove Aug 1 '19 at 14:22
  • $\begingroup$ when lindberg flew to europe he took enormous risks given the time and period. without men daring nothing is really possible $\endgroup$ – JP VDB Aug 2 '19 at 15:34
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I'm wondering if there were any test missions to get unmanned ships to the moon and safely back to Earth?

There were no uncrewed round-trip missions to the moon prior to Apollo 11.

Several one-way missions landed safely on the moon without crew before 1969, but did not return, including the American Surveyor series. The first of these, Surveyor 1, landed on the moon on June 2, 1966.

In 1970, the first robotic round-trip mission, the USSR's Luna 16, returned samples from the moon.

There weren't any huge technical obstacles to robotic lunar round-trip missions. The Luna round-trips used a clever return trajectory that required only a single burn from the moon's surface with no course corrections afterwards, but that technique constrained when and where they could land on the moon; a multiple-burn return would have required a little more sophistication in the probe's guidance and navigation system (and thus more mass and cost), but it wouldn't have been impossible to do pre-Apollo-11.

Returning from the moon takes a vehicle several times larger than one that just needs to get there; if you don't do a lunar orbit rendezvous like Apollo did, then you need to carry all the fuel for your return journey all the way to the moon's surface. Luna 16 was more than 5 times as massive as Surveyor 1, for example, requiring a 700-ton Proton booster to go to the moon instead of a 140-ton Atlas-Centaur.

Lunar orbit rendezvous offers a path to a lunar landing mission with a smaller vehicle at the cost of additional mission complexity, and automatic docking had been demonstrated by the USSR in 1967.

The USSR's lunar landing plan would possibly have landed one LK uncrewed as a backup, followed by a second LK with a single crew member, but they never got the necessary N1 booster to work. The LK itself had a backup ascent engine, so this plan provides 8 times as many ascent engines per crew member as Apollo. They clearly didn't want to strand a cosmonaut on the moon.

It seems like a big jump to suddenly send manned ships there.

It would have been technically feasible to land an Apollo LM (with some modifications) uncrewed. However, one of the major lessons of the X-15 program was that the combination of automation and human capabilities in a complex system was far more reliable than either human or automation alone. If, for example, Apollo 10 had flown its LM to the surface without a crew, it would have had substantial risk of crashing (having no way to know if it was coming down in a field of boulders) and the program would have missed out on the first-hand observations of the crew.

As with other apparently-risky steps taken in the Apollo program (particularly Apollo 8, discussed here and here), skipping an unmanned landing attempt was a calculated risk to save time and money.

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    $\begingroup$ This is a superb answer! $\endgroup$ – Organic Marble Aug 1 '19 at 2:47
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    $\begingroup$ I think your answer should mention the tortoises on Zond 5. It's an intermediate step between unmanned craft and the manned missions, showing that life support systems could remain operational, and keeping the passengers alive long enough to survive the journey. $\endgroup$ – Innovine Aug 1 '19 at 11:53
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    $\begingroup$ @Innovine And in fact the USSR did a remote control docking in ‘67. $\endgroup$ – Russell Borogove Aug 1 '19 at 13:23
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    $\begingroup$ @user That was considered by the US, but the USSR’s final plan was a one-lander LOR plan not too unlike Apollo. A return lander still has to descend and ascend safely (albeit without crew mass on the descent) then you need a whole second ship for descent only, so it’s less efficient. $\endgroup$ – Russell Borogove Aug 2 '19 at 13:57
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    $\begingroup$ @RussellBorogove I think their plan was to do the entire landing automatically. Soviet spacecraft tended to be more automated than US ones. So the first lander would be a test of the landing system, and also offer a spare craft if the ascent engine on the later manned one failed. $\endgroup$ – user Aug 2 '19 at 14:01
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No. NASA was focused on manned missions. The unmanned Surveyor series proved that a Moon landing was possible, and launching from the lunar surface wasn't considered risky enough that an unmanned trial run was considered worth doing. The closest any of the Surveyors came to "Earth return" was Surveyor 6, which performed a "hop" reaching an altitude of four meters, landing three meters to the side of the original touchdown point.

The Soviet Union took two shots at it: an unnamed mission that failed on launch in June 1969 and Luna 15 (crashed into the Moon 13 hours after the start of Armstrong's moonwalk), but the first successful unmanned sample-return mission was Luna 16, in September of 1970.

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    $\begingroup$ Zond 5 performed a successful circumlunar flight in '68, and its passengers, a pair of tortoises, returned safely to earth. $\endgroup$ – Innovine Aug 1 '19 at 16:14

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