How far did Nazi Germany get in researching the "sun gun?"

Question

Nazi Germany tried to win World War II by creating "wonder weapons." They actually produced the V-2 Missiles capable of reaching England, and tried, but failed, to develop the atomic bomb.

One of the weapons on the drawing board was the Sun gun. It was supposed to work as a "space station" from which the sun's rays could be concentrated, and fired onto enemy cities.

Arguably, the rocket program was a prelude to a "space program," not an Apollo (moon-walk) program, per se, but the creation of a space station from which "bombs," either the sun's rays, or other space material, could be "fired" onto enemy cities on earth. The end goal was a weapon, like the atomic bomb, that was an order of magnitude more destructive than conventional bombs.

How far along did the Germans get in creating such a "space station," or at least the means to access outer space? Was the "sun gun" just on the drawing board of a few "mad scientists," or something within the realm of technical possibility, given enough time?

Answer 1

It never got off the drawing board (literally).

I have a few sources that suggest that the scientists never got beyond some basic technical drawings and schematics related to the Sun Gun. Admittedly, they aren't the best sources I could hope for, but they agree, so I'm inclined to believe them.

The idea was conceived by Hermann Oberth in 1923 (and published as part of a book in 1929). He was a rocket scientist, not a military man, and he originally wanted to use it for the purposes of capturing energy and heat transfer. He called his concept the "space mirror", and it was envisioned - well, exactly as it sounded: a giant mirror in space. It could have been part of a space station, with a manned crew. It was extremely implausible at the time, but later developments made it seem possible. In the 1940s, Germany was undergoing an incredible acceleration of scientific and engineering ideas, courtesy of the Nazis, and Oberth's idea was turned into a weapon. But, fortunately, it never got far.

From here, we find out what the United States got:

In addition, they [the German scientists] handed over the schematics and calculations for their formidable Sun Gun concept.

From here:

In 1945, when the victorious Allies began sifting through captured war plans, it emerged that the Nazis had updated Oberth’s proposals and begun looking into the possibility of the Third Reich building a mirror weapon in orbit 22,236 miles above the Earth.

Interestingly enough, though, this suggests that the plans are lost:

No schematics survive to show how the Nazis might have built the mirror.

Read through these sites more and you'll come to the same conclusion the Allies did: The scientists made very elaborate calculations and blueprints, but there was no testing of any prototypes, or any other form of experimentation.

Answer 2

In the Oddly Historical web article The Sun Gun: The Nazi Plan to Build an Orbital Death Ray, the idea started by Dr. Hermann Oberth, a German engineer and rocketry pioneer who had already started developing plans for a space station in the 1920's. The Nazi's liked this idea, and made plans to turn it into a weapon, using a sodium mirror.

Plans for the logistics of this plan were even drawn up, from the article:

Nazi scientists working on the project envisioned using rockets to lift prefabricated sections into orbit.

The planning was very intricate, even to the point that the workers in the station would wear magnetic boots!

In the end, it was the fact that a lot of the technology required did not exist. Even with their advanced (for the day) rocketry

Their best rocket, the infamous V-2, would not have been able to reach the 5100 mile orbit called for in the plan by itself, much less with enough payload to begin building the mirror.

So, the scientists envisaged that it would take several decades to perfect their technology and techniques - the end of the war put an end to that.

An interesting twist, when analysed, the feasibility of such a weapon is not so good, with

It turns out that a quirk of optics mean that rather than destruction from on high, the sun gun would probably unleash nothing more horrifying than a pleasant spring day.

Answer 3

Even today, I suspect making a space mirror capable of reflecting sunlight accurately onto a region of Earth as a weapon or for agricultural would be extremely difficult. A group of astronauts working together to construct a large mirror I think is unprecedented; if we tried it today, it would be done robotically which would require AI that only in the past 20 years or less has become available and it would still be a hard problem.

Before 1945, the multiple manned space craft coordinating efforts to assemble the mirror were easily half a century away. I don't think any kind of space-based weapon even today would be very effective against Earth, and if we wanted one, it would likely be just a missile base in space or a killer satellite. One thing about a space mirror -- impossible to hide and easily destroyed by a single projectile perhaps fired from the Earth's surface. Also: I do not think "space lasers" will ever work due to beam spreading and power loss due to atmospheric absorption -- I do not think we have lasers with anywhere near that kind of range. (In 2021, a crazed congress member will suggest that space lasers are deployed and used to set wildfires -- but lasers as weapons are only effective at ranges of a mile or less.)