Regarding the starting point: we already have an interesting discussion on the subject, you're welcome to take part.
Regarding the end of the era: what about Europe? Are you sure we can call 1950s Paris or 1960s Berlin or "Swinging London" Dieselpunk? What about countries behind the Iron Curtain? I was born in Russia, where in mass conscience the history was split in two: "before the War" and "after the War", with WWII in between. If we take Dieselpunk as purely American phenomenon, a mix of 20s Prosperity, Great Depression and Golden Era, so OK. But I prefer to see it as something global.The bottom line is: Dieselpunk is what you build. But in my very humble opinion, anything we're trying to build here doesn't go well with an H-bomb or first space flights.
Why does it have to end so early? ... Still, I'd say a hard line on Dieselpunk is actually the beginning of the Nixon Adminitration. It represents a decline into the muck that was 70s style, and a turn in the Cold War that would lay the foundations of American foreign policy until 9/11 in a lot of cases.
I could see space flight happening in Dieselpunk. However, in a different style that which took place in the 60's and beyond. I think different aspects of the Diesel culture end at different times. I heard a historian say that many day-to-day technologies after the war were much like before the war. One example could be a typewriter that was a technology used during the Diesel era. Now, I'm not expert about typewriters as they are not particularly interesting to me. However, they continued to be used in the office and household until the advent of the personal computer.
But I don't really know if something ends for an era as a result of it falling out of style or being replaced by a better technology that is not like the classic. I personally think that the end of the Diesel era should be based on technologies rather than a specific date. That may be harder or more complected to define than saying "19YZ" but it works better for me.
One thing I try to do when I write dieselpunk is separate the technology from earth and place it in a completely new setting.
Yes, I think the Dieselpunk legacy goes almost until the the end of the 60s. In the end, as I understand the punks, the technology is what defines the era within, but the opening and closings are defined by emmense social changes. Steampunk begins with the defeat of Nappoleon, which leads to British hyperpower and the begining of industrialization in Europe and the end of serfdom. World War I with the catastrophic chan ges that made mosters like Stalin and Hitler possible. World War II represents a reactionary victory; the re-imposition of the dominance of liberalism and capitalism mostly because of the United States. World War II did not change much of life in Western Europe once the rebuilding was done. The social changes that end Dieselpunk are the rise of the New Left, the Frankfurt School, mass immigration from non-white countries, the Hippies, the Civil Rights struggles, and in the USSR, the removal of Khruchev. And yes, decolonialization was important too, but only when the states of Europe realized that their empires were gone and they were, like it or not, vassals of the US. All of this is squarely at the end of the 60s. And strictly speaking it is this time when modernism gives away to post modernism among intellectuals. But I am baised and see most, but not all of these things as very, VERY bad.
That said, in world affairs, how steampunk can you get outside Europe? Any world that is steampunk, is not going to see much change when Pearl S. Buck writes the Good Earth. To need a 'worldwide' paradigm of any punk is specious, because most of the world will remain unchanged. Punk is about supercharging the best tech of the day, and for a woman in Afghanistan, it means all rot, unless the British decide to test their new submachine guns on the armies of Kabul.
Typewriter... Well, well. It's a Steam Era artifact, actually: most common type was developed before WWI. I used it through 1980s. And I know an office of the Israeli Broadcasting Service where for some idiotic reasons typewriters were used until 1999! Should we see the end of the 20th century as the end of Steampunk?
Or take steam locomotive. Swept away by diesel and electric power, it retired from American, Russian and British mainline service in 1950s - 1960s. But in South Africa, India, Eastern Germany and China it continued to work through 1990s. Again, we have to decide whether the last decade of the past century was also the last decade of Steam, or the steam locos were just the relics of long gone era.
Yeah I could see space flight in a Diesel era alternate world - but it would either be more in line with Buck Rogers/Flash Gordon or the Raygun Gothic Rocket than the actual cold war Space Race of the 60s... and it would certainly have a different 'flavour' to it than your 'Earth Vs the Flying Saucers' type flick of the 50s
Isn't Diesel era space flight the basis for "Iron Sky"?
I'm looking forward to seeing that !!!!