Space: Unsafe at What Speed?
This morning, Sir Richard Branson went to space. Virgin Galactic did an impressive job, and the flight went off without a hitch, but this article isn’t about that; it concerns the much more significant threat our space travel poses. Our species is advancing technologically forward at an unprecedented rate, and that rate of change is also dramatically increasing. Even with all the advances since the Mercury and Apollo programs nearly five decades ago, we are still bound to earth as a species. From this May, our best speed record in space to date is only 1/20th of one percent of the speed of light, achieved by NASA’s Parker Probe. Until we’re capable of traveling between stars, at speeds much greater than that of the Parker Probe, we are only a threat to ourselves, and humanity will be left believing we’re alone in the universe.
The real question is, at what speed does humanity pose a threat to other space-faring species? Also, speed may be only one of several possible triggers that force them to make the first contact. Others may be developing a mastery of technology to manipulate gravity, space, or even time itself (assuming that’s even possible). Today we’ve been left chiefly alone, evolving relatively undisturbed in our little corner of the galaxy. Unfortunately, over the past 80 or so years we’ve created a number of extreme electromagnetic events that have escaped our ionosphere to the point where space-faring lifeforms would have noticed them. I’m not talking about Hitler’s 1936 broadcast of the Olympics or even the original airings of “Gilligan’s Island” or “I Dream of Jeannie.” None of these likely escaped to outer space; I’m talking about nuclear weapons tests.
Since the USA tested the tiny Gadget Plutonium device in 1945, which opened the age of nuclear weapons, there have been over 500 atmospheric tests of atomic weapons. Each test released an enormous amount of energy, some in the form of electromagnetic radiation capable of escaping to space. Particularly Hydrogen bomb weapons tests like Russia’s 57 Megaton Tsar Bomba (initially planned for 100 Megatons, but at 57 Megaton, it was still 3,800 times more powerful than what the US dropped on Hiroshima). After it exploded in October 1961, the atmospheric shock wave it created circled the globe three times, and radio communications were knocked out for an hour. If space-faring species didn’t take us seriously before 1961, they certainly did afterward. Additionally, in the 1970s, we regularly used radio telescopes to transmit signals, some as powerful as a megawatt, directly at star clusters where we believed at the time we were most likely to encounter intelligent life. Today, in this universe, we’re passive players in a game where the rules, the board, and even the other players have yet to reveal themselves.
Suppose for a moment that we viewed space travel as primarily a problem of speed. With our current scientific understanding, the speed limit is the speed of light, which in space is 300 million meters per second. To make an extended journey through space, it is strongly recommended that artificial gravity, roughly equal to that of earth, be provided. While our species can live in zero gravity for extended periods, zero-G isn’t ideal for our long-term health. The current thinking is that artificial gravity could be achieved by continuously accelerating or decelerating a ship at 1G or 9.8M per second squared. Assuming we eventually develop engine technology capable of sustain 1G of acceleration over extended periods, think decades, with virtually an unlimited supply of fuel, a significant fraction of light speed may be achievable. To reach half-light speed by accelerating a human crew at 1G would take nearly a year. At some point during this acceleration, the effects of relativity will start to become significant. The ship’s mass will begin to increase as its speed increases, time will dilate (observers on earth will view time for those on the vessel as having slowed down), and how the ship accelerates will change with its ever-increasing mass.
As mentioned earlier, our fastest ever spacecraft, the new unmanned NASA Parker probe to explore the Sun, in May 2021, achieved 330K mph. Eventually, Parker is expected to reach 430K mph or 0.064% of the speed of light. By contrast, the Apollo 10 mission in 1969 set the speed record at that time for a human-crewed flight at 24,791 mph or 1/13th of what Parker is traveling today. Humankind will need a whole new approach to accelerating our vehicles if we ever intend to become a starfaring species.