As of 2020, colonizing outside of Earth and into the other bodies that orbit our sun--planets, moons and even asteroids--is all talk and no do. Sure, we have stations like the International Space Station and Skylab, but they are merely orbiting from the air and not planted on any ground. Space telescopes like Cassini and New Horizons don't count, either, as they merely observe rather than directly involve.

In an alternate 2020, the human population on Earth is noticeably lower, as are the populations of livestock, giving Earth more room for the wild places. That is because, in 2020, there are millions of people living in fully established cities on both the moon and Mars, meaning that Earth has less people for more balance.

What point--or points--of departure would I need to make this kind of scenario believable?

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – L.Dutch
    Nov 3 '20 at 15:26
  • 13
    $\begingroup$ "millions of people" don't put a dent in earth's popolation. $\endgroup$
    – ths
    Nov 3 '20 at 16:06
  • 4
    $\begingroup$ For reference: The moon has only triple the area of Europe! $\endgroup$ Nov 3 '20 at 17:22
  • 1
    $\begingroup$ we had skylab, not anymore however $\endgroup$
    – Topcode
    Nov 3 '20 at 19:05
  • $\begingroup$ Millions of people on the moon doesn't reduce the overall population of the earth very much. $\endgroup$
    – kutschkem
    Nov 4 '20 at 13:47

14 Answers 14


3000 BC

To make Space colonization now viable, safe, and common, you need to start back in ancient Egypt. Instead of war between different cultures, the pharaohs will have to unify humanity more than it is in our timeline. The first Milestone of Egypt is the expansion to the Roman Empire's dimensions in 1500 BC. It's a society that will be united by one goal: to bring the pharaohs home to the stars. To this aim, talent is driven forward and technology flourishes. And the empire grows, unifying the Eurasian and African continent.

ca. 750 BC

A splinter group in the far fringes of the empire, declares their Prince-Gouverner (a relative of the pharaoh) to be a true Pharaoh in what in our timeline would be China. While unprecedented, this act of rebellion goes unpunished, as it was the most liked nephew of the Pharaoh. China and Egypt both aim to get their respective lines to the stars now. As the years pass, other splinter lines join the developmental race, but it is all guided by the peaceful aim of getting the Pharaohs into space - after all the one that will do so first will have proven to be the real line of Pharaohs!

ca. 900 AD

Several lines have come and gone, split off and merged in again. The political landscape is entirely different, the idea of a republic has never been born. However, the prevailing system is a meritocracy: teaching is universal, and whoever shows potential is brought forward.

In Religious terms, there are only various variants of Egyptian Pharaoh cults, all of them having syncretistically absorbed local ancient gods: In Scandinavia the Pantheon is centered around Odin-Thoth, in Magna Graecia it's Zeus-Atum, on the British Isles the duality of Morrigan-Anubis and Dagda-Osiris center the gods, just to name a few.

The year 900 brings finally the discovery of America. New Pharaohs establish there, but sadly enough, the new offshoots of the empire don't get along with the natives. This is when the empire has to learn war for the first time in about 1000 years. But the war with the natives spurred developments that were previously unknown, and soon they manage to wipe out the resistance as firearms get developed from the peacefully used black powder that was used only to honor the gods for the last 300 years. While a war against other Pharaohs is unthinkable, guns propagate as ritualistic objects and hunting implements.

ca 1300 AD

All of the world is in Pharaohnic hands for two hundred or three hundred years. The Industrial Revolution has started some and is in full-blown steam. We only look at this point, because around this time man has managed to build the first motorized airplanes.

ca 1400 AD

The first rocket reaches space. Twenty years later, the first artificial satellite is a Pharaohnic burial. The first Pharaoh has returned to the stars, but this doesn't stop the attempt of each pharaoh to get better than the last.

1620 AD

The first interplanetary ship has been built and launches with a pharaoh, his family, and thousands of servants, priests, and craftsmen. It aims for Mars. About a hundred years later Mars is filled with colonies, and they need to look for different planets. So they build generation ships instead.

2020 AD

It has become a rite to launch generation ships instead of fracturing the empires further. About every 50 to 100 years a wave of ships leaves earth, each ship better than the ones before. Humanity is currently putting the finishing touches to the eighth exodus.

  • 38
    $\begingroup$ While this deserves an upvote, I hate to say it, but this is too perfect. People could do this, but wouldn't. There would always be the conflicts and plagues that tear apart civilization. Pharaohs would split violently like Alexander's empire, or destroy knowledge like the destruction of the library of Alexandria. I don't think people are this good. :( $\endgroup$
    – DWKraus
    Nov 2 '20 at 2:51
  • 3
    $\begingroup$ Yup, this is straight-up /R/HFY stories alley though. $\endgroup$
    – mishan
    Nov 2 '20 at 8:55
  • 10
    $\begingroup$ Ancient empires like Rome and China largely stopped growing because they couldn't effectively control territory that far from the capital. Uniting Afro-Eurasia without significant communications innovations on par with the telegraph would be next to impossible. $\endgroup$
    – Grollo
    Nov 2 '20 at 15:34
  • 3
    $\begingroup$ @Grollo almost autonomous Governers make communications much less of an issue, which was the Egyptian model. $\endgroup$
    – Trish
    Nov 2 '20 at 16:36
  • 9
    $\begingroup$ This reads like a summary of my games of civilization :-) $\endgroup$
    – quarague
    Nov 3 '20 at 8:09

Let's use the 1989 Rockwell International Integrated Space Plan as a reference point. It had a biplanetary civilization (i.e., permanent presence on the moon) by 2010 (we didn't make it). But it shows you in pretty good detail what you'd need to do to make it. Said simply, you need to have everything it shows between 1989 and 2010 happen by 2020.

Once someone opens that chart and looks at it, you'll see why I've not taken the time to summarize it here. It's MASSIVE. There's a LOT OF TECH that hasn't been invented yet that Rockwell thought could be invented quickly.

(If you're thinking biplanetary i.e. Mars... That wasn't expected to happen before 2023.)

So, what "point of departure" could exist? You need everything that happened from 1955 until what Rockwell thought would happen by 2010 and have it actually happen by 2020. What the world has proven is that Rockwell's well-intentioned plan was INCREDIBLY short sighted. It's frankly unfair to say that about them — after all, that chart embodies a mind-bogglingly large amount of tech.

I therefore submit this answer as being the best you're going to get — because explaining how hundreds of industries would need to change over 70 years is way, way, way beyond the scope of this Stack.

BTW, the only reason I didn't VTC this question as too broad/opinion-based is the existence of Rockwell's ISP. Had that not existed, this question would have been impossible to answer in any practical way. It would have violated Stack Exchange's book rule.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – L.Dutch
    Nov 4 '20 at 5:46

About 4.5 billion years ago. You'd have to tinker with the formation of the inner planets, making Mars large enough to hold on to its atmosphere & water (and give it a stronger magnetic field, working plate tectonics, and so on). Venus could be spun up to give it a day of around 24 hours, and perhaps a moon similar to Earth's moon.

Then, assuming the evolution of compatible life (panspermia, anyone?) you'd have planets like the Mars & Venus of '50s SF. People would actually be able to live there, instead of having to stay in cramped, temporary habitats, supported at vast expense by Earth.

  • 1
    $\begingroup$ Venus could have been habitable at an earlier point in the solar system’s history when the sun was cooler, but not now. Even the Earth is now right on the inside edge of the habitable zone — with almost no CO2 left in the atmosphere, it still gets uncomfortably hot, and will be sterilised in a billion years or so. Even if Venus had a moon and spun faster, it would have lost all its water long ago. $\endgroup$
    – Mike Scott
    Nov 2 '20 at 7:56
  • 1
    $\begingroup$ @Mike Scott: OK, so you move it a bit further away from the Sun. My point is that there's no motivation for large-scale space colonization (that is, beyond research bases & perhaps mining/industry) without decent places to live. $\endgroup$
    – jamesqf
    Nov 2 '20 at 16:16
  • $\begingroup$ I think this is a good answer, but is insufficient on its own. Having somewhere to go is go is a good spur to bring forward interest in the Spade race. $\endgroup$
    – Jontia
    Nov 2 '20 at 19:16
  • 2
    $\begingroup$ Thanks for awakening my interest @Jontia ecns.cn/hd/2019-12-02/detail-ifzrhrks8237748.shtml $\endgroup$
    – bytepusher
    Nov 2 '20 at 23:53

Make Nixon more ambitious, (and make Apollo 13 a success)

After the lunar landing, Nixon was presented with 4 choices. Ranging from "Lets colonise mars" to "lets play it really safe and not go past LEO". Nixon chose to play it safe and we spent the next 50 years using a space shuttle to go up to LEO only.

Nixon's choice was validated by the Apollo 13 near miss.

Had Nixon instead choose to pursue Wernher von Braun's "Das Marsprojekt" (or more specifically the 1956 "2 ship, 12 crew" proposal), instead of the ISS, we'd conceivably have bases on the moon and Mars by the late 80s early 90s.

It's a stretch to imagine these growing to millions over 40 years, but I'd say just within the realm of plausibility.

To get a more likely outcome - you probably would need to rewrite the 20th century all together. Remove the great war of 1914 (maybe replace it with a friendly "tech race" cold-war style between super powers, first in aviation - try to get the jet engine in the 20s, V2 in the early 30s, etc) and keep the roaring 20s going through the great depression by the increased government research. With no great depression, WW2 or Manhattan project but still the research motivation we might of got to the moon a few decades earlier. Then mars colony by the 50s, etc.

  • 1
    $\begingroup$ And I think that just because there are millions of colonists doesn't mean the colonies are self-sustaining. They can be vanity/pride projects of various world governments. They could even be a sort of gulag - export your smart but disliked people somewhere they can't sustain themselves and must constantly work to stay alive. Rebellion means supplies are cut off... $\endgroup$
    – DWKraus
    Nov 2 '20 at 2:28
  • 1
    $\begingroup$ Trying to eliminate wars seems a bit counterproductive; the V2 mentioned was a direct war product. Perhaps you could do better by breaking up the wars in shorter struggles, with more cold wars. Have a truce in mid 1916, and a tech race because of the unresolved conflict. $\endgroup$
    – MSalters
    Nov 3 '20 at 13:27

You can conceive a alternative reality where Orion Project suceeded in the 1950s

The Orion project researched the feasibility of building spaceships using uncontrolled nuclear chain reactions (nukes) as propulsive means. As it's written in the back cover of a book telling its history, by the son of one of the physicists involved :

In 1957, a small group of scientists, supported by the U.S. government, launched an attempt to build a four-thousand-ton spaceship propelled by nuclear bombs. The initial plan called for missions to Mars by 1965 and Saturn by 1970. After seven years of work, political obstacles brought the effort to a halt.

If the space programs we have today, based on high-tech thin metal can spaceships, are the equivalent to planning a transatlantic crossing using only kayaks, then the Orion project can be thought as a bold attempt to build a proper ocean liner to do the crossing. To build a spaceship would be less like assembling a plane, and more like dock shipbuilding, or large-scale civil engineering. The super orion reference design would be a 8,000,000 ton spacecraft, with a diameter of 400m.

For more information:

  1. Dyson, George. Project Orion: The True Story of the Atomic Spaceship. Reprint edition, Holt Paperbacks, 2003.

  2. Dyson, George. The Story of Project Orion. www.ted.com, https://www.ted.com/talks/george_dyson_the_story_of_project_orion. Accessed 2 Nov. 2020.

  • 1
    $\begingroup$ It might also be worth pointing out that the primary thing that killed the Orion Project was politics - in particular, the nuclear test ban treaties that forbid the civilian use of nuclear explosives. $\endgroup$
    – nick012000
    Nov 3 '20 at 3:50
  • 4
    $\begingroup$ @nick012000 Also, a series of technical realities. Orion nuclear pulse vehicles are better launched from orbit than the Earth's surface. Surface based launches looked good in theory, further work showed they weren't too good. Plus extremely dangerous. The amount of radioactive fallout would have been prohibitive. The treaty that halted the Orion Project, which hadn't got started properly, was the ban on nuclear weapons in space. $\endgroup$
    – a4android
    Nov 3 '20 at 4:18
  • 2
    $\begingroup$ @a4android The amount of nuclear fallout caused by surfact launches would have been minimized with properly-designed launchpads (giant steel plate coated with graphite powder, IIRC), and you could also minimize it by launching the rocket a few hundred meters into the air with another propulsion method so that the fireball no longer touches the ground. Fallout is caused by objects being sucked into the nuclear fireball and disintegrated; if there's no objects to get sucked in, there's no fallout. $\endgroup$
    – nick012000
    Nov 3 '20 at 4:21
  • 3
    $\begingroup$ @nick012000 I will consider minimization as plausible. However, launching from orbit was found to be a better option. The main advantage for Orion spacecraft was their potential size & higher payloads if surface launched. Launching from orbit loses that, which is a pity. I was always fond of the Orion concept. But we can't have everything. $\endgroup$
    – a4android
    Nov 3 '20 at 4:29

The Sovietunion should not collapse.

The real cause of the collapse were:

  1. The political elite has lost its belief in the System.
  2. The economical weakness (compared to the Capitalism) could not have further polished.

While the communism existed, there were race. Space race, nuclear race, science race, and so on.

All of them catalyzed the technological development on the whole world.

In a monopolar world, where the USA has no real competitors, not even they have real interest to develop. They are interested in the stabilization.

This caused the stop of various X-projects (incl. X-37 which could have been an SSTO in the late 90s), this is why the U.S. seems to give up nuclear energy, this is why both the ISS and the Hubble will be soon crashed.

If the communist block could have survived the crysis of the late 80s, early 90s, probably serious events had happened in the whle block, similar to Ukranian famine of the 30s. This had caused civil unrest, anti-communist revolutions. The System had crushed them with force and terror, as it was usual by the commies. Probably a North Korean-style government would rule in many countires of the Block. The other parts would work like China.

The USA had both the money and the technology to have a Moon base already at the early 80s. What they did not have: the interest of the voters, and the will of the political elite.

They had no competitors.

Give them the competitor. And you get the Moon base.

  • $\begingroup$ Is there no race with China and Europe? If the US think that not, they've lost for real... $\endgroup$
    – Anderas
    Nov 7 '20 at 19:13
  • $\begingroup$ @Anderas Europe is the w* of the U.S. China is quickly growing, but despite that their population is 2x more than USA+EU, their GDP is about that of the EU. And they needed 30 years to grow even to this level. I think the world will be monopolar in the next decades, and no one knows what will later. That China simply gets to the top and nothing happens, well I think it is unlikely. $\endgroup$
    – Gray Sheep
    Nov 10 '20 at 12:35

Three things: earlier rockets, free energy and something bad.

1. Move space race earlier. As laid out in this concept: Spaceflight without transistors and nuclear power - how to bend the history of physics?

In this timeline the Treaty of Versailles is enforced and Germany does not rearm. WW2 does not happen. Germans instead find their pride in a space race, which begins in earnest in 1931 and is not interrupted by a world war. The Soviets and Americans hustle to catch up.

  1. Cold fusion.

The ability of palladium to absorb hydrogen was recognized as early as the nineteenth century by Thomas Graham.[18][19] In the late 1920s, two Austrian born scientists, Friedrich Paneth and Kurt Peters, originally reported the transformation of hydrogen into helium by nuclear catalysis when hydrogen was absorbed by finely divided palladium at room temperature. However, the authors later retracted that report, saying that the helium they measured was due to background from the air...

In this timeline, the Austrians do not retract their work, the shadowy forces coercing them in our timeline being otherwise occupied in theirs. Cold fusion develops apace and is ready to power the first Moon colony in 1955. Unsurprisingly given where the power is from and the rockets are from, these lunar colonists speak German.

3. Something bad. Fewer people on Earth is not because they leave Earth for the moon and Mars. Yes people do leave Earth for the moon and Mars but it is because they hope to escape the fate of many persons who remain on Earth. Wild lands are reclaiming Earth from the humans and the number of humans is dwindling because Earth is becoming a bad place for humans, and space seems relatively attractive. The nature of this change is left as an exercise for the worldbuilder.

  • $\begingroup$ Or something good. Find 'gold' on the moon or chlorophyll on Mars. $\endgroup$
    – KalleMP
    Nov 3 '20 at 19:44
  • 1
    $\begingroup$ @KalleMP - it would have to be pretty dang good. Earth is nice. $\endgroup$
    – Willk
    Nov 3 '20 at 20:53

About the 12th century.

To have millions of humans located in space by 2020, you need a significant improvement in launch technology, and it needs to have been in place for long enough for the required space migration.

How could you easily bootstrap greater technology? move back the invention of the modern printing press by a few centuries. The Gutenberg press was developed sometime around 1440 AD. But, the needed precursor inventions had been around for hundreds of year. Movable type had been invented in China around 1040 AD, and the screw press dates back to 1st century Roman empire. Had Chinese been an alphabetic language, it is possible that movable type would have spread faster than it did.

In any case, inventing the modern press could easily have occurred a few centuries earlier than it did, sparking the Renaissance sooner and making the technological rise occur correspondingly sooner.

It was a clearly technology enabling innovation that could have occurred hundreds of years earlier than it did.


Three words:

Lest Darkness Fall.

That novel by L. Sprague de Camp describes the adventures of an accidental time traveler, a historian who is thrown back to 535 A.D.

This is in the aftermath of the fall of the West Roman Empire. The antique knowledge and civilization is still there; the dark ages which will stall Western European development for a whopping thousand years have not begun yet.

As a historian, he is able to prevent some key events which were causal to the disintegration of society and the descent of darkness upon Europe. He establishes a newspaper, a semaphore system, the Arab numbers — in short, he jump-starts the Renaissance a millennium early.

Plenty of time to get them rockets cooking :-).

Edit: As steveha says, this is not suggesting time travel as a means to have space flight earlier; instead, the story alters a few key events after the fall of the Roman empire. de Camp considers that a time of great volatility in which the actions of a single man can nudge Western history to take an entirely different course. Certainly the randomness of history has greater power than a single man, knowledgeable as he may be...

  • $\begingroup$ Time travel is cheating. $\endgroup$ Nov 3 '20 at 22:51
  • 1
    $\begingroup$ Time travel is cheating, but imagining those key events went differently for some other reason than time travel isn't cheating. This answer is good if it means "read Lest Darkness Fall and come up with world-building that causes those events to happen and jump-start the Renaissance". $\endgroup$
    – steveha
    Nov 3 '20 at 22:56
  • 1
    $\begingroup$ @JohnWDailey I meant it as steveha said: The novel points out what would need to happen in order to get modernity going a thousand years early. The time traveler has no physical means to alter things in 535: It's all ideas only. Everything he does is within the means of the times, that's what's fascinating. In fact, the novel was written in response to unrealistic time travel stories. Sprague de Camp strove to realistically explore the constraints the year 535 would impose on progress. $\endgroup$ Nov 4 '20 at 2:14

As a German I could not resist. Writing this made me feel equally elated and sick in the stomach.

Hitler dies shortly after starting the WW II. A saner and more capable commander in chief leads Germany to victory over the European neighbors, an armistice with Britain and an arrangement with the U.S. The Soviet Union is never invaded. Under the new leadership the all-out Holocaust does not happen. The war ends in 1942, sparing the Reich and its neighbors the worst destruction. Consequently, the Manhattan Project is stopped before it really started. The Reich and its allies/vassalles now consists of most of continental Europe. Its vast natural, human and industrial resources make it the leading world power.

This victory and Hitlers death lead to an air of optimism in the leadership and public. The Nazi ideology becomes less paranoid; instead, influenced by the Italian Fascists, it fully embraces modernity. Industrial, technological and scientific progress is the new paradigm. The Fascist government, much like China's today, is able to devote resources at will wherever it desires.

A new beginning is declared; a host of ambitious new projects is publicly funded in order to boost the civilian economy after the war. Chiefly among them are two futuristic new discoveries: Nuclear power and space flight, of which leading proponents are already in Germany. The German race policies are softened. The new elite of scientists and engineers enjoy special status and are exempt from any remaining restrictions.

In 1946 the Generaltechnikmarschall (Chief Marshal of Technology) holds his famous speech in front of an audience of 1,000,000 at the Volkshalle construction site:

Wie wir uns bisher von allen Widersachern befreit haben, so werden wir auch die Fesseln der Schwerkraft abschütteln und frei sein! Das heldenhafte Deutsche Volk wird die Menscheit zu den Sternen führen, wie es ihm vorherbestimmt ist!1

Oberth and von Braun are given virtually unlimited resources to develop manned spaceflight. The DWA (Deutsche Weltraum-Agentur, German Spaceflight Agency) becomes the global hub of spaceflight development, attracting scientists and engineers from all over the world. Frank Malina and Theodore von Kármán move to Germany and establish a jet propulsion laboratory at the Technische Universität Berlin, joined by Sergey Korolev and Friedrich Zander from Moscow. Fermi returns from America and, together with Otto Hahn, leads the newly founded Institut für Nuklearforschung in Berlin-Wannsee.

These pioneers remember this as the best time in their life. The enthusiasm, the collaboration, the discussions through the night. Oberth writes in his memoires:

And the best thing was: When von Braun and I agreed in our nightly discussion, we would go to the Herr Technikmarschall right in the morning, unkempt and all. He would beam at us like a child on Christmas morning when the secretary let us in: "What have you got for me?" We would pitch our idea. He would ask "does it serve progress?". We would nod. He would ask "and can you do it?", and we would look at each other because we were not at all sure we could. But nothing seemed out of reach. There simply was no ceiling, quite literally. So we would nod. And he would smile, and nod, too. And then he would with a stroke of his pen provide funding, for the Moon, for Mars, for the Asteroids. I think he would much rather have been in our Institut than behind his desk, but these signatures were the only way he could participate. So he was, in a way, our most reliable team member, for more than 20 years.

Money is never an issue. The post war economy is running hot, given the convergence of German engineering, a decisive lead in key technologies and the state-sponsored cooperative Fascist economy. One example of many is that Germany by the late 1950s basically powers the world with the reliable, standardized Fermi-designed nuclear power plants it exports by the hundreds. They are sold as a turn-key leasing model including staff and fuel. The revenue of the state-owned IG Atom soon eclipses the budget of many mid-level countries. Not only is there no dearth of money, to the contrary: The huge trade surplus must go somewhere.

In 1949 the first satellite reaches orbit, followed by the first manned flight two years later. From there the development is exponential. The moon is reached in 1956. Nuclear propulsion is hard to get right, but the world's brightest minds achieve the first successful launch in 1957. The massively increased launch capacity makes it possible to establish a moon base and have a number of space stations in orbit by 1964, providing a stepping-stone for Projekt Mars. The planet is reached in 1969, a first colony established in 1980. Asteroid mining is explored in 1985; the first asteroid is nudged into an Earth orbit in 1992 where it is mined for metal and water, followed by many more. The solar system is literally swarming with swastikas.

1 As we have freed ourselves from all adversaries before, we will shed the shackles of gravitation, too, and be free! The German people shall lead mankind to the stars, as it is its destiny!

  • $\begingroup$ What does the "Dai Tōa Kyōeiken" aka Japan's Greater East Asia Co-Prosperity Sphere do? I bet they might not agonize the US with pearl harbor, and instead securing china... The Solar system might swarm with Swastikas and Rising Suns... $\endgroup$
    – Trish
    Nov 4 '20 at 15:33
  • $\begingroup$ @Trish Yeah. I wondered about Japan as well. But I know next to nothing about the Asian side of the war, and the post was long enough as it was, so I left it blank. $\endgroup$ Nov 4 '20 at 16:01
  • 1
    $\begingroup$ Let me draw up a rough idea... Japan did get the plans for a jet engine in '45 from Germany. Because the Japanese also own a lot of close to equator islands, and most of the rubber after they overran China and southeast Asia, leaving Russia and the Philippines alone, they act as the DWA's junior partner. While their program at first is smaller, they ramp up production massively because they have one thing over Germany: Labor force. They pull even in numbers of spaceflights around 1985, and their colony on Mars surpasses the german one in size in 1990. $\endgroup$
    – Trish
    Nov 4 '20 at 16:03
  • $\begingroup$ I am not sure, how a sane Führer could have helped. Germany was very strong, compared to the rest of the world, but it was still lesser than 10% of the world population. It was a wonder that they nearly won, even so. I think not his insanity caused the lost war, but the foreseeable loss caused his insanity. $\endgroup$
    – Gray Sheep
    Nov 17 '20 at 21:21

To build and habitate cities on other planets - you will need about 100 yeares timespan minimum. Since we would be able to complete it by around 2100 at best even if we start right now you have to shift first orbiting launchers to 1900 , end of XIX century.

Yes, good old steampunk.

Its not that fantastic. At the end of XIX century advanced countries had everithing to begin rocket building. They even had more then that - they were not so concern about life, death and honor. So couple of (or ten) expeditions lost on the way to Moon would just add chalenge and fame to the winner. (If you a warry about computers - you don't need them if you have skills, tables,"orbital" arithmometer and lots of courage - 10% chance of success should not frightening you.)

In RL all that spirit and technology was "utilized" to conquer the skyies and fight World Wars.

So for space exploration to happen great nations of XVII-XIX need to:

  • become less aggressive
  • become less religiouse (may be greater influence of French Revolution?)
  • invent internal combustion engines 50 years earlier (together with steam engines?)
  • invent flight 50 years earlier
  • have futurists like Tsiolkovsky appere 50 years earlier
  • do not held any Wold Wars
  • start race for speed and height instead

It's pure fantastic assumptions. But only form sociological point of view. Just like now, technlogy then were far ahead of human's mentality.


Someone has to get serious about reusable rockets much earlier than SpaceX.

In our world, spaceflight is rare; airplane travel is common. The most significant difference between the two is that airplanes are reusable: you don't expend an airplane to travel. The fuel cost to fly something to orbit is only something like 40 times as much as the fuel cost to fly it from Los Angeles to Australia; but with disposable rockets the cost to send something to orbit is nearly four orders of magnitude greater than flying it to Australia.

The USA, obsessed with winning the space race, developed the Saturn V; this allowed the USA to send an entire moon mission in one launch. But after the excitement died down, the cost was prohibitive. Then NASA made things worse by trying to develop the Space Shuttle without anywhere near enough design/fly/test cycles. (They tried to design the first fully reusable launcher on paper without flying any prototypes, and further made it a heavy-lift vehicle! Hardly surprising that the Shuttle turned out to be not very reusable.) This mistake was partly due to severe budget cuts making it difficult for NASA to afford multiple design/fly/test cycles, IMHO a direct consequence of everyone being tired of how much money space flight cost.

If, instead of trying to win a race to the moon, the USA had tried to win a race to have a reusable spacecraft, costs would have been much reduced and we would have fuel depots in orbit and routine flights to the Moon now. We can imagine that instead of a race to land on the moon, the race was to make a space station, and they focused on making the rockets more and more reusable as time went on. They never built the Saturn V (they didn't want something like Skylab, they wanted something so big it had to go up in pieces) so they did iterate their way to something reusable. Why did it have to be so big? Maybe it needed to be an orbiting missile launch platform?

Another possible point of departure: when Ronald Reagan proposed the Space Defense Initiative, someone could have gotten really serious about reusable spacecraft, to launch all the space weapons and defenses. The "Delta Clipper" project, instead of being an unwanted thing NASA was forced to accept, could have been the hot new project (the project everyone wanted to work on, the one that most of the spending was for, etc.) and if lots of money and people were thrown at it could have turned into a reusable technology. Just imagine that someone like Jerry Pournelle had somehow been made head of NASA in Ronald Reagan's first year as President, and had been given lots of resources. The DC/X did quite a lot on a shoestring budget; what could it have done if given lots of support?

Finally, I'd say you can simply imagine that a billionaire like Elon Musk had founded a company like SpaceX much earlier. That doesn't even require a particular date to make it work. (Maybe Howard Hughes was even richer than in actual history, and also obsessed with reusable rockets?) The billionaire has to be willing to lose money for years until the reusable rockets start to really work, at which point the company starts charging 1/10 as much as anyone else can charge to launch things, and the company starts making huge profits and grows rapidly.

All the above could result in things like advanced space stations, or a moonbase, by 2020. But I re-read your question and saw that you are imagining millions of people on Mars by 2020. That would require reusable spacecraft much earlier, requiring substantial changes to how history actually went (maybe Rome never fell? maybe the Renaissance happened 100 years earlier? maybe the Islamic Golden Age lasted two or three centuries longer than in our history, or even never ended?)... and/or discovering some new science like antigravity or teleportation. (If you could have some kind of "stargate" like device where people could walk to Mars by walking through a gate, it becomes much easier to imagine millions of people doing it quickly.)

I just checked and according to the US FAA web site, the FAA provides service to more than 45,000 flights and 2.9 million airline passengers per day (probably a bit less now, thanks to COVID-19). Airplanes are roughly 1.2 centuries old. It's true that the flight to Mars is worse than any air travel, requiring months, so fewer people will travel by spaceship to Mars; but still, it seems safe to imagine millions of people on Mars about one century after reusable rockets become practical. So to make your timeline work with only known technology, imagine that we somehow got SpaceX-style rockets in 1920.

If reusable rockets make space travel affordable, space travel becomes routine, and colonies become possible.

P.S. To put colonies on Mars it would really help a lot to have some better technology than chemical rockets. Rockets just can't carry enough chemical fuel to fire the engines for very long, so they have to coast for much of their travel. A nuclear engine that could run much longer (even at lower thrust) would dramatically reduce the time to travel between Mars and Earth.


  • $\begingroup$ "A nuclear engine that could run much longer (even at lower thrust) would dramatically reduce the time to travel between Mars and Earth." By how much? $\endgroup$ Nov 5 '20 at 1:30
  • 1
    $\begingroup$ @JohnWDailey "how much" depends on the specifics: how much thrust, how long it can operate, etc. I provided a link to Wikipedia with a whole discussion you can read. But I'll give you one specific example: we have sent probes to Mars on coasting paths that took around 300 days, but the Wikipedia page for a VASIMIR engine discusses a flight to Mars in only 39 days. en.wikipedia.org/wiki/… $\endgroup$
    – steveha
    Nov 5 '20 at 20:37

These two books are frequently available in many used book stores with an SF section:

Heppenheimer "Colonies in Space" Stein "The Third Industrial Revolution"

Reading them will give you serious background for how to do it.

Stein's book is based on the following concepts:

  • It's feasible to transmit microwave power long distances with phased array antennas. This has been demonstrated at the 60% level, and it scales better with larger antennas.

  • After the moon program develop a heavy lift reusuable rocket and get the price to orbit down to ~200/Kg. He cites a Rand Corporation report I think that this would be possible (1975 dollars)

  • Phase one is lunar mining. Lunar regolith -- dirt -- is shoveled up put in 10 kg fiberglass fabric bags.

  • A lunar induction catapult is used to launch the bags to one of the Lagrange points in lunar orbit.

  • There, orbital factories break the dirt down to silicon, oxygen, aluminum, magnesium. Serious handwaving needed here. No one knows how to refine with limited water and unlimited heat and zero G.

  • Most of the structure of the lagrange colony is glass fiber and foamed glass.

  • Initial industrial energy comes from large solar mirrors. In zero G it's reasonable to blow a 1 km plastic bubble a few microns thick, and then silver half of it. This gives you a circular km of sunlight that comes to an approximate focus about 30 meters across.

  • Silicon is processed into solar cells. These are set up by the square km. A solar powersat is built with a few GW of microwave energy.

  • electricity is converted into microwave energy, and broadcast from a sparse array about 3 km across. The ground station is about 10 km across. The array requires a diode and a dipole antenna about every meter. These are about 4" across. The land underneath it is still usable for crops. A duck flying across the array will experience it's temperature rise about 1 degree. Farm equipment under the array is easily shielded against this low flux density.

  • Initial cost for the first unit is 1 trillion dollars over a 25 year period. After that they come off the line at 1 per year for about 20 billion each.

Time Line: (Not in the books above.)

  1. U.S. quits the Vietnam war. President authorizes part of the peace dividend to start development of Heavy Lifters, and grants tax breaks to companies that independently develop orbital capacity.

  2. Results from the Apollo mission are sufficient to pick a base for mining regolith.

  3. Luna Station catapult starts test shots. Catcher net at L5 works flawlessly.

  4. Solar cell fabrication plant reaches 1 MW production/day

  5. First powersat is moved into position. First grid is in the Mohave desert and is used to power desalinization plants for southern California.


You can't decrease earth population by spaceship migration. Doesn't work.

Imagine the Queen Mary. Queen Mary 2 from Wikipedia

4000 people aboard, employees and passengers. The Queen Mary is dirt cheap compared to a space craft, because it doesn't need life support, monster engine or other spacecraft features. It also doesn't need to be self sufficient.

Earth population is growing by roughly 80 million per year. So you would need 20 000 flights of our hypothetical Queen Mary to just suck up the population growth. As a cost efficient flight to Mars costs 3 years, you'd need 60 000 ships the size of Queen Mary just to take the growth. One Way.

The Queen Mary was costing 870 million euros in 2002. You need it times 60 000. Multiplied with the factor you need for all the spaceship technology and these embarrassing amounts of fuel to lift these out of the gravity well. And then the Mars can't feed these people.

So, for the point of significantly reduced earth population: It can be policy change, to reduce the birth rate. Or something truly catastrophic which will also kill the ability for space travel. Space ships don't work for this purpose

For the other points of your question, I agree that early development of fast long range data transfer (telegraph later, semaphore earlier) will stabilise big empires and help development. Early intensive use of printer press would have been possible already in the middle to late Roman Empire, had they just thought of it. They had all the prerequisites, just not the idea. They had an alphabetization rate of estimated 50% so it would have been worth it straight away.

The printer press kicked off our current era: huge storage capabilities for data and huge multiplicator ability for technology and ideas. It kicked off the witch hunt: You can spread rumours and conspiracy theories, too. Invent the press1500 years earlier and you can maybe get into space earlier?


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