I’m all burned out about / space junk / walk and talk about / space junk / it smashed my baby’s head / space junk / and now my Sally’s dead / space junk
That’s from Devo. It was 1978 and a year later Skylab came down to much hype. The station had been in a decaying orbit for years, it’s not like Devo were prescient. And of course other spacecraft had previously fallen from the sky, notably Soviet Salyut/Kosmos stations and such things as Saturn booster pieces. Skylab, however, was big. At roughly 75 tonnes* it was the largest object to ever fall from orbit. The only thing larger happened many years later when the Space Shuttle Columbia disintegrated over Texas on its return voyage in 2003. That was not only a 100+ tonne spacecraft but it held seven human passengers.
This Easter weekend we get treated to another space fall, that of China’s Tiangong-1 space station. Tiangong means “Heavenly Palace.” After its mission life Tiangong was supposed to break up in the atmosphere on a controlled re-entry. But Ground Control, it seems, has lost control of the orbiter and it’s going to come down on its own. Skylab was about ten times more massive than Tiangong. Large pieces of that craft were found in Australia. And no, no one was hit or killed. In fact, there are no known terrestrial casualties from falling space debris. A few dozen much larger objects than Tiangong have dropped out of the sky since 1957’s Sputnik-1. The third-largest, at 45 tonnes, was the second-stage of the Saturn V rocket that launched Spacelab into low earth orbit!
So we’ve been through this before. Stuff that we launch into orbit around our planet doesn’t stay there forever. It falls back to earth at some point, usually because it runs out of fuel. Space stations and other manned spacecraft orbit the earth about 200 miles up. By contrast, communications satellites use “geostationary” orbits over 20,000 miles above the earth. Those are typically boosted to higher orbits (called “graveyards”) at the end of their lifespans so their spots can be claimed by their replacements. Not so for low earth orbits. Those still encounter atmospheric drag, even if it is very small, and have to frequently fire their rockets to maintain their orbital elevations.
It’s hard to get into space and it’s hard to stay in space. And it’s even harder for humans to survive in space. As much as we all like the idea of human astronauts exploring Mars that is a daunting task. I can only imagine it would take many launches of support craft that would create both orbital and surface depots so that any human voyage could have enough supplies to get there, visit, and return. The trips to the moon took three days. A trip to Mars would take about seven months! There about a dozen people on earth who have spent more than 200 continuous days in space and only one to have spent over 400 days. Such a mission would require an enormous commitment of resources and would likely have to be international. In fact there’s a good chance it will be a private venture as governments and taxpayers will probably balk at the costs.
There’s too much to learn from our space-based adventures not to continue them. Most of the work will be carried out remotely by robots and computers, we don’t actually have to go to the moon, an asteroid, or Mars to explore these places. In fact, our drones will do a better job and there won’t be any risk to human life. That’s boring, though. People don’t care about scientific discoveries (unless those discoveries cure cancer or something). But they do like space travel and they like the idea of astronauts investigating extra-terrestrial frontiers.
At some point in the future, if we survive as a species, the synergy between our carbon-based brains and our silicon-based AIs will, I hope, be the breakthrough that enables such things as off-world living. But until then we’ll have to be content with a few astronomical Niñas, Pintas, and Santa Marias that will just barely make it across the gulf of space, and if they are lucky, plant a flag or two and get home in one piece. Don’t expect a flood of emigrants to the new worlds, though. 3500 miles was quite a distance in those days, but a ship could do it in two months, and when they got there they still had air and they could forage for water and food. Our astronauts will find their Promised Land a bit less hospitable.