I remember watching the Apollo moon landings on TV from 1969 to 1972 as a child. Witnessing that very first landing on the moon was inspiring. I was even an eye witness to one thrilling event during those years. I can still recall the sight of the Apollo 17 Saturn V rocket flames rising into the night sky from my front yard in Miami, Florida in 1972. These sights no doubt had something to do with my lifelong interest in all things astronomy and space exploration.
As we prepare to celebrate the golden anniversary of the first manned moon landing on July 20, we should pause to consider what made it possible. The Saturn V rocket was a monumental technological achievement. Some 400,000 people worked to design and build it in the decade leading up to its first launch (see here and here). While we are right to recognize these fruits of human ingenuity and labor, they would not have been possible without a number of just-right aspects of our home world.
A Simple Fact
Consider the simple fact that we can see the stars. Not every world affords its inhabitants clear views of the night sky, or even nights. Some Earth-size terrestrial planets, like Venus, have thick, nearly opaque atmospheres. Others are located closer to the galactic center or within star clusters, where nights aren’t very dark. Planets around red dwarfs tend to have tidally locked rotation, and they are often accompanied by multiple planetary neighbors in close proximity. If any inhabitants of such a planet could somehow live on its dark side, they would likely have bright “planet-lit” night skies.
We live in a relatively sparse region of the Milky Way galaxy around a singleton star. Free from the glaring light of excessively bright or excessively numerous stars, we can see many faint small Solar System bodies, nearby stars and distant galaxies. We do have a bright light in our night skies, but it’s largely out of the way for about two weeks every month. It more than makes up for this inconvenience by giving us “perfect solar eclipses” and a motivation to leave our nest.
Taunted by the Moon
Would we even have thought of developing a space program if we couldn’t see the stars or a nearby large moon taunting us every month? Not only have we known that the moon is the closest celestial neighbor for over 2,000 years, but we’ve known since then how far away it is. The modern answer is that its average distance is between 238,000 and 239,000 miles. I recently experienced a personal sense of how far this is. Just a couple weeks ago the odometer in our 2003 Toyota Corolla reached 238,000 miles (see picture above).
The Moon was an “easy” first destination for space-bound humans, serving as a kind of training ground for us to get our space legs. We were able to put people on the moon with computer technology far inferior to that found in a cell phone.
What made the moon shots “easy” for us were many generally unacknowledged requirements for space exploration satisfied by our environment. Not only should we not take for granted our clear dark nights, we should be thankful that we can gather the raw materials needed to build and fuel a rocket like the Saturn V. Earth’s crust is a ready-made storehouse of concentrated, purified, and accessible minerals and fossil fuels (see here and here). The industrial revolution and modern technology very much depend on our ability to mine these resources with relative ease.
The two propellants employed in the Saturn V were refined kerosene/oxygen in the first stage and hydrogen/oxygen in the upper two stages. Kerosene comes from petroleum pumped out of the ground, hydrogen comes from water and oxygen can be obtained from either water or the atmosphere. The hydrogen/oxygen combination is one of the very best chemical rocket propellants (measured by the thrust force produced for each unit mass of propellant), given the small mass of hydrogen. Think of that next time you take a drink of water (H2O)! The reason kerosene was used in the first stage is because it is a much denser fuel than hydrogen, allowing for a smaller tank for the same mass.
With the rocket and its propellant at the ready, next we need to launch it. Obviously, we need a solid platform — water-worlds and gas giants will not do. The two biggest hurdles to overcome are the planet’s gravity and atmosphere. On a super-earth the weight of the Saturn V would be greater even though the mass would be the same. In such a case less payload can be sent into space, or, to put it another way, the fraction of the payload mass to the rocket mass will be smaller. To launch the same payload mass as the Saturn V did on Earth on a planet ten times Earth’s mass the rocket would have to be almost as massive as the Great Pyramid of Cheops!
I am surprised to see how close we as humans are to end up on a planet which is still reasonably lightweight to conduct space flight. Other civilizations, if they exist, might not be as lucky. On more massive planets, space flight would be exponentially more expensive. Such civilizations would not have satellite TV, a moon mission, or a Hubble Space Telescope. This should alter their way of development in certain ways we can now analyze in more detail.
Do I Dare?
Do I dare bring up the word “purpose?” Is our environment setup for us to be able to leave our nest and travel to the planets and even other stars? It certainly seems that way.
Once we leave Earth, what next? We have already gone to the moon, other planets, and we’ve even sent five spacecraft on their way out of the Solar System. Something else we can try to do is visit the asteroid belt to mine minerals. The fact that asteroids are small makes them relatively easy to mine; there is more surface for a given mass for smaller bodies. Once we start mining the asteroids (again, it should not be taken for granted that any planetary system will have accessible asteroids), we can build large interstellar ships. It can almost be done now. What is required is increased automation in mining and manufacturing. Once we can achieve that, the stars are ours.
This brings up an aspect of intelligent design rarely discussed: predicting the future. If evidence for design also points to a specific purpose (not always the case), then you might be able to predict events that would continue to satisfy that purpose. In the case of space travel, a number of features of our planet have conspired to allow travel beyond Earth. Additional features of the Solar System seem to have conspired to permit travel beyond the Solar System. From these, can we predict that human interstellar travel to other planetary systems is possible? I think so.