Fifty years have passed since humans first left the gravitational pull of their planet of origin.  Even the achievement of Earth orbit requires the tug of the Earth’s mass to maintain the spacecraft’s path around the globe. The period of true space travel, when humans went beyond not just the Earth’s gravitational influence but also its protective atmosphere and magnetosphere, was exceptionally brief and lasted only four years, from December 1968 to December 1972.

There will be much celebration in the media of this era and rightly so.  It is almost cliché to note that by traveling into space, humans gained more of a perspective about Earth.  The boundaries familiar from maps are not seen from space.  The oasis of life that is the “blue marble” is correctly seen as fragile against the cold blackness of space.  Much of our 2018 perspective about our home planet was shaped by the events of fifty years ago.

Since 1972, human space travel has consisted only of circling Earth in a low orbit just a few hundred miles above the surface, about the driving distance between Los Angeles and Las Vegas.  While this type of space trip is anything but routine, it certainly is familiar.  So familiar that people are proposing Earth orbit as a type of luxury vacation trip for the super-wealthy.

But on Christmas Eve in 1968, humans circled the Moon for the first time.

And much of the technology that allowed that feat is still state-of-the-art fifty years later.

Unlike the rockets behind the Mercury and Gemini programs, the rocket that powered Apollo was not a converted ballistic missile.  The Saturn V rocket was the first American launch vehicle with no other purpose than to provide for deep space travel.  Yes, a trip to the Moon was – and is – considered “deep” space.  The cost of the Saturn V rocket was great.  It required the United States to assume the ethically ambiguous position of using ex-Nazi engineers as key members of the design team.  It also required 4.5% of the total United States Federal Budget during the mid-1960s.  Nearly a nickel out of every tax dollar went to NASA.  Since the Apollo program, it has been a penny or less.

That’s why billionaires who talk of “private” missions to the Moon – let alone Mars! – are not playing straight with the public.  Space travel is costly because, despite the mind-boggling progress in electronics over the past fifty years, elementary Newtonian mechanics – the physics of forces and masses – has always been the show-stopper.  Fuel has weight.  So to lift a chemically-fueled rocket off the ground requires the ability to also lift the fuel.  But that additional fuel adds additional weight which means even more fuel is required.

Pretty soon you end up with a rocket the size of a Saturn V.  Twice the size of the Space Shuttle.  Or the SpaceX Falcon 9.

No amount of Moore’s Law progress – the steady, exponential shrinking of electronics that enabled the digital age – alleviates these basic physical limitations.

So there is a premium in reducing fuel weight.  You won’t have a lot of it available once you get the rocket launched off the ground.  As long as we are using chemical rockets to create propulsion, humans aren’t going to be jetting around the solar system like a dogfighting Millennium Falcon or a hard-banking Federation Constitution-sized Enterprise.   No, our few journeys to the Moon were highly planned affairs where the spacecrafts were carefully aligned and pointed, the rockets burned for several minutes, and then the spacecrafts coasted most of the trip along a straight line to the target objective hundreds of thousands of miles away.

This is the reality of space travel.  And this is why a tremendous amount of infrastructure and personnel is required to develop, launch, monitor, and complete any manned mission beyond low Earth orbit.  In fact, the infrastructure and personnel costs are not only well beyond the means of billionaires (who are already piggy-backing on the taxpayers’ bought government research and infrastructure) but also beyond the means of individual nations.  There’s a reason, for example, why the International Space Station is international.  The United States decided the costs of this orbital platform, in the relative safety of low Earth orbit, were beyond its means.

So, let us look back at 1968 and celebrate.  Let us marvel at the ingenuity of humans for its exploitation of physical laws.  Let us be awed by the first time we, as a species, saw our planet in a new, interconnected and unified way.  Let us applaud the determination of astronauts who pressed on with their mission despite puking and shitting in their spacecraft.

But let us never forget that space is cold.  Space is harsh.  Space travel is expensive.  And dangerous.

And never, ever routine.

The Apollo 8 mission of December 1968 still represents our best ideas in physically rocketing away from the Earth.  Our parents’ and grandparents’ space propulsion technology is still, at its core, state-of-the-art.  As we contemplate journeys into the endless void, let us remember that the Moon is still just as distant for us today as it was during that initial brief period of human deep space travel.  And it will require just as much determination and treasure to simply return to it.