It is 1984. Space travel is real, extensive and highly militarized. Nukes shove the big Orions between planets, Gemini and Soyuz duel in orbits across the solar system, and elite forces fight on mars and the moons of Jupiter. Space is the battlefield of the cold war where Nukes are allowed. What happened ?
A real atomic war happened. Sometime around 1950, with both sides tossing nasty little fission nukes and invading western Europe, China, the Mideast and etc.
In this timeline, in 1945, soviet forces captured SS Scientist Klaus Debner and much of his Nuclear weapons lab, research and prototypes. Stalin, already hard at work terrorizing Soviet science into replicating the Fat Man bomb, shoved this to the head of the queue and had a working micro nuke/dirty bomb by 1948. Accordingly, as the post war period began and the allies fell apart into east and west, Uncle Joe (having his own bomb, even if he misunderstood the American version) was much more aggressive and belligerent. Result: three to five years of ABC war in Europe ( spreading to China and Korea) with no clear winner, but several clear losers (Korea, China, Japan, Germany). Europe and SE Asia were essentially trashed, but the homelands of the two alliances ( USA and USSR) suffering significantly less damage (no ICBMs, and not too many ways to deliver bombs across intercontinental distances); both sides locked in a brutal stalemate, which has turned to space for resolution.
More hot clashes follow as the space race starts up in 1953, and is even more frenzied, makeshift, and armed. By 1984, the earthside damage from two orbital wars and a series of smaller orbital clashes across the 1960's has lead to demilitarization of CisLunar space, administered by a very different United Nations. Beyond that, as the sea dogs of Elizabetan England said, " no peace beyond the line !"
Meanwhile, at home
Earth is not a nice place to live; the situation is like the present day Koreas writ huge. The DMZ in this timeline is across central Germany down to the Adriatic, and across current Iraq and Iran and Afganistan, as far as what is now the Pakistani border. The USA has become a fortress state, with a permanent wartime economy, facing the fortress state of the Soviet Union across fortified continental demilitarized zones marking the last lines of the still unresolved war.
And that's not all....
The mid to late 1950’s were marked by massive third world crop failures and famines due to climate alteration from the wars. Relief, when offered, usually resulted in amalgamation with the helper – and even then was often unsuccessful. As a result, a lifeboat strategy adopted by both east and west. Nations worldwide collapsed in anarchy and rioting. Emigration, famine and war have combined to significantly reduce Europe’s population; in particular, the UK experienced a massive wave of emigration to the commonwealth countries, especially Australia) in addition to the mass evacuations of 1952-53
Another Big change
Due to the need to keep buffers between the East and the West, and to attempt to administer wrecked countries the United nations has essentially been absorbed by its own Peacekeeping Authority Directorate (UNPAD, or PD) (created in the early war years in aresponse to the 1949 Korean conflict). It has become an aggressively neutral and extranational organization, initially responsible for policing the Asian and European Exclusion zones (the DMZ’s). It has moved all offices to the old Benelux region, and holds national jurisdiction over the refugee choked lands therein.
The First and second orbital wars resulted in the treaty of new Dehli (1963), demilitarizing and internationalizing cis lunar space adding it to the jurisdiction of the UNPAD. Post 1968, after the UNPAD concentrates on orbital policing, CisLunar space is off limits to any non UN craft or satellite except for transit. Yes, this means that they own all the satellites; the orbital "cleaning" of 1968 surprised all powers, and resulted in the UNPAD gaining complete control of LEO. However, extralunar space, and the rest of the Solar system is wide open. Ground and sub orbital combat is common on the moon, mars and in Jovian space. Skirmishes and suborbital clashes along the bamboo curtain, and Mitteleuropa are common.
More to come !