In article ,
Greg D. Moore (Strider) wrote:
...If it had been necessary, and cost was no object, what would
be the earliest time that a lunar landing would have been possible. I
argue that the Germans could have done it with their 1940s technology.

You can look at the Saturn V as a scale-up of the V-2. Just a much bigger
rocket.
That is of course an extremely simplified look at things. Getting the F-1
engines to burn stablely was itself a large task.

However, that was mostly a consequence of its very large combustion
chamber. When the Russians ran into similar problems, they responded
by clustering smaller chambers instead, which worked.

Von Braun's "Das Marsprojekt" -- published in 1952, but based on work done
somewhat earlier -- proposed going to *Mars* with essentially WW2 German
technology.

Then of course you have things like the IU and on-board computation. Even
with the advances there, much of the navigation was helped out by the
ground.

Apollo could have gone to the Moon without ground help, using the on-board
optical navigation system. In fact, completely autonomous navigation was
originally a design requirement, and the capability was retained for abort
cases. (The ability to fly a lunar landing solely on optical navigation
was eventually sacrificed to free up some memory in the computer.) Tests
on Apollo 8 confirmed navigation accuracy comparable to ground-based radio
navigation.

Doing without the on-board computer would have been a bit less easy, but
Gemini demonstrated computerless LEO navigation (including rendezvous).

And of course things like fuel cells. While the science had been around for
I think about a century, making it work effectively was part of the problem.

Alternative approaches would have been used -- either solar-dynamic power
(concentrating mirrors supplying steam for turbogenerators), or possibly,
for the shorter lunar mission, gas turbines tapping propellant from the
rocket tanks. Heavier and involving moving parts, but quite workable,
especially on a larger scale than Apollo.

Ultimately I think it comes down to, "how much brute force and money are you
willing to throw at the problem?"

Quite so. I can't immediately think of any technological issues that
couldn't be finessed by just throwing mass at the problems.

The one area where von Braun's original concepts might have hit a serious
technological snag would be the extensive reliance on orbital assembly
work done in spacesuits. 40s and 50s concepts were (in hindsight) grossly
over-optimistic about both working in free fall and getting adequate suit
flexibility. It wasn't until the mid-60s that we really understood how
big a headache this all was. The discovery of this might have required
replanning around either modular concepts or development of much larger
launchers to minimize dependence on orbital assembly.

(Well, and there would have been the small matter of his favored assembly
orbit -- the "two-hour orbit" -- being right in the middle of the inner
Van Allen belt...)
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |