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Among a variety of alternatives considered at the time, the Apollo configuration of 3-person CSM and 2-person LM, launched atop a single vehicle was considered the optimal choice for its day.

With today's accumulated experience in spaceflight and almost 50 years of technological advancement, would a mission mounted today to fulfill Kennedy's mandate "land a man on the Moon and return him safely to the Earth" look similar?

First, let's exclude from consideration any spaceflight systems currently existing or under development capable of transporting humans beyond low Earth orbit (we can consider the Space Shuttle, but not Orion).

Let's say that the mission must deliver at least one person to the lunar surface such that the astronaut can walk on the surface, and perform physical tasks similar to what was done during Apollo. Let's also say that the science payload (all equipment delivered to surface and samples returned) are mass equivalent, and the durations of both moonwalk and surface stay are similar.

Would such a mission have the same complement (3 to lunar orbit, 2 landing), or would it be more, or less?

Would there be a separate CM and LM at all (perhaps a combined CM/LM, leaving only an unmanned SM in lunar orbit to rendezvous with after lunar ascent and power the ride home)?

Would the mission vehicle(s) be similar in size and configuration? Would a single launch vehicle for the entire mission requirement be optimal or would multiple launch with orbital rendezvous be favoured? Would the Space Shuttle (if not retired) have been a practical way to deliver as far as LEO (by multiple launches) the people and equipment required?

The point of the question is whether 50 years of technological advancement and spaceflight experience has "changed the equation" which was calculated back then, or whether the best answer then would still be the best answer today.

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    $\begingroup$ What do you wish me to focus on? I can write a feasibility paper and show the differences and it would take me days to write it, containing 20+ pages of figures showing trends. Ranging from material choices to automated landing. And from human training to computer automated engineering. So what part is most important to you? $\endgroup$ – paul23 May 11 '15 at 16:18
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    $\begingroup$ The ideology has changed. Now NASA HSF must find a "stepping stone" before they can go anywhere. Like sending a probe into the Sun or something. I suppose the Apollo industry is gone by now, otherwise it would've been politically impossible to do it in any other way than repeating the old way. At least the shuttle industry is now converting to a deep space launcher, and it is politically impossible to go to the Moon without giving the contract to whatever kind of space industry happens to be already established. They have a hammer and are searching for a nail. $\endgroup$ – LocalFluff Jun 7 '15 at 7:04
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    $\begingroup$ @LocalFluff my question was meant as a sort of "thought experiment" regarding the optimal vehicle architecture and mission profile to accomplish the objective and how it would differ from that actually used. It was about how technological advances and accumulated space flight experience to-date could inform the selection/development process for the space vehicles/major modules required, and in what ways the 1960s solutions have been outdated. $\endgroup$ – Anthony X Jun 7 '15 at 18:45
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    $\begingroup$ Elon Musk suggested loosly that the return vehicle could be preplaced and the Moon thus be reachable with two Falcon Heavy launches. Apollo 12 landed within walking distance from a Surveyor lander, so why not send an entire base before humans land there? $\endgroup$ – LocalFluff Jul 29 '15 at 3:33
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A big difference is that you wouldn't need to leave someone in lunar orbit. We now have experience and confidence in the remote operation of an uncrewed vehicle. So you could have a crew of two instead of three. Or perhaps a crew of three to the surface with a larger LM. Overall, there would be much more automation, especially for the landing process, pinpoint landing, and hazard avoidance. Also rendezvous and docking would be automated.

The overall architecture would be quite similar. If you don't have a big enough launch vehicle handy, you could add an Earth orbit rendezvous to launch the CM/SM and LM separately. You could consider electric propulsion to put the LM in lunar orbit on the slow boat, ahead of the CM/SM, for mass savings or more capability to the surface.

You would need something like Orion or crewed Dragon, qualified to enter at lunar return velocities. You can't "exclude from consideration" new systems, since we would have to recreate the capabilities of most of the Apollo systems.

Our management of large engineering projects has advanced considerably, so with all the management processes we now engage in, it will take 20 years to complete the project instead of eight.

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    $\begingroup$ So, without need to support a crew member in lunar orbit, would that lead to a single crew compartment complete with aerodynamic exterior and re-entry thermal protection making the entire round trip down to the lunar surface and back to Earth? Or would it still end up more efficient to park the return/re-entry vehicle in lunar orbit and only fly a purposed lander to the surface and back to lunar orbit, just like Apollo? $\endgroup$ – Anthony X Jan 13 '15 at 2:00
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    $\begingroup$ +1 for "Our management of large engineering projects has advanced considerably, so with all the management processes we now engage in, it will take 20 years to complete the project instead of eight." $\endgroup$ – Erik Jan 13 '15 at 4:07
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    $\begingroup$ Unlikely. There's no good reason to bring the mass of an Earth entry, descent, and landing (splashing) system down to the surface of the Moon and back up again. $\endgroup$ – Mark Adler Jan 13 '15 at 4:07
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    $\begingroup$ @AnthonyX: You've got the cause and effect backwards. The human was left in orbit to maintain the Earth-landing craft. The craft was not left in orbit to sustain the human. $\endgroup$ – dotancohen Jan 13 '15 at 8:22
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    $\begingroup$ Another +1 for the advanced management techniques that make us ever more efficient. $\endgroup$ – David Hammen Jan 15 '15 at 3:14
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There's an assumption in your question.

the Apollo configuration of 3-person CSM and 2-person LM, launched atop a single vehicle was considered the optimal choice for its day.

The simplest mission profile would have been a direct flight. The docking required for both EOR and LOR schemes seems to have been distrusted at the time; hence a major objective of the Gemini flights was to demonstrate rendezvous and docking.

As every popular history points out, the Saturn 5 was "not large enough" to launch a direct flight, thus the LOR scheme. There's an unmentioned assumption in this statement...

I've seen a photo of a concept model from the 1960s, a Saturn 8. Basically a fatter Saturn V with 8 engines in stages 1 and 2 (don't remember what stage 3 was). It was conceived to launch a direct flight with the 3-man CM.

Wait a minute! If that's the needed size for that mission, might it be possible to scale the CM down for 2 crew and launch a direct flight with a Saturn 5?

The answer is "yes". The CM wasn't a mass-efficient design even for 3 crew. The Lunar Gemini proposal used this approach.

Basically, NASA settled on the CM design too early. Then settling on a Saturn 5 too small to launch a direct flight with that, they were forced to a rendezvous scheme.

Incidentally, a similar lock-in situation occurred in the Soviet Moon program. In their case, with the booster. They had designs for all-new Moon rockets, but they rushed into the program and decided to repurpose an already-designed but not yet built rocket: the infamous N1. It was not sized for a lunar landing, having been designed around a manned Mars-and-Venus flyby mission.

Broadly, we're in a similar situation now in terms of available options.

Some possible differences, major and minor:

Would we settle for the low science payload and surface stay time of Apollo? Particularly the latter could be increased at little cost in mass. And I expect a rover would be there for the first landing.

The launch vehicle might have solid boosters or an all-solid first stage.

EOR might be more accepted. However, I expect this would still use launch vehicles larger than those currently in use. The Shuttle is horribly inefficient in terms of payload fraction, and I assume any EOR scheme would be limited to rendezvous and docking rather than assembly needing workers.

I suspect LOR might be replaced by L1R - using Earth-Moon Lagrange 1. Easier access to high-latitude landing sites, can launch from Moon at any time and still rendezvous, and the craft left in space can maintain line-of-sight communication with Earth.

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The closest to a "mandate" in recent times was George Bush's "New Vision" in 2004. We would not be satisfied with a mere lunar lander today, with a few walks, we would want instead to have a longer base, perhaps more people, etc. The New Vision program was to develop 2 new spacecraft, the Ares I and Ares V/ Altair. Ares I later evolved into the COTS program/ , it was intended for LEO orbit. One part of that still remains, the Orion program. Ares V was intended to launch a much larger payload to space, with the Moon being the primary target. The goal was to have Ares I in 10 years, and Ares V/ Altair about 5 years after that. This of course all changed after George Bush left office as president.

The Altair mission was to send humans to the Moon for up to 7 days initially at a time, turning the Moon into a research base similar to the Antarctic research base. It would land 4 people on the Moon, with an orbiting Orion vehicle for Earth return. Orion would remain unmanned for its duration around the Moon.

I imagine that if the mandate were given today, it would be very similar to the Altair mission, in that it would have an Earth rendezvous, unmanned capsule remaining around the Moon, and a longer mission on the Moon with more people.

If it became really important to make this happen quickly, it could be done, at more cost and risk. The US public isn't as willing to spend huge sums of money on the Moon as it once was, nor take significant risks. The end result is that additional time would be required to make this happen, at a lower cost and risk.

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