In your lifetime, could it be possible to travel anywhere on Earth in under an hour? Skeptics say no, but that is not stopping some people from trying. Spacex recently began hiring engineers to design and build floating launch/landing platforms for their Starship rocket. The last time that Spacex mentioned floating platforms was in the 2017 Starship (then called BFR) promotional video, which highlighted the possibility of using the rocket for hypersonic Earth-to-Earth transport. While many have dismissed this as a pipe dream, rocket travel is not as crazy as it seems on the surface.
In the world of engineering, complexity is often the enemy of safety. The more parts and components you have in a system, especially moving parts, the higher the probability that something will go wrong during operation. Commercial aircraft, despite taking millions of travelers around the world everyday, have thousands of moving parts. They have jet engines, with compressor blades, turbines, and fans, they also have flaps and other control surfaces. Everything must work perfectly to preserve the safety of occupants.
Rockets, ironically, are in some respects simpler than aircraft. Indeed, despite “rocket science” being equated with something that is difficult to achieve, rocket engines are no more complex (perhaps less so) than the jet engines that power passenger aircraft. Indeed, in the early days of the jet age, jet engines and rocket engines were not seen as all that dissimilar from one another. Today, preconceived notions of jet engines and rockets might be holding industry and society back from important technological breakthroughs.
If rockets are not inherently more complex than jet aircraft, then why are jets so much safer than rockets? Jet aircraft were not always safe. Early jet engines failed often and didn’t last very long. The reason that aircraft have become so safe over the years is that lessons have been learning from flying millions upon millions of flights. Every flight is a test of thousands of components, and each failure, glitch, or bug, tells us a little more about how the system can be refined and improved.
Rockets, on the other hand, have been hamstrung historically by one limitation: expendability. Rockets rarely have been designed to be reused because engineers hadn’t figured out how to land and reuse them. Each rocket launch flew a totally unique specimen, with unproven parts and unknown failure modes. Now that Spacex and others are tinkering with rocket reuse, engineers are finally able to examine rockets after after they return; learning how parts hold up, how we might improve their durability, and make them safer and more reliable. Ironically, reused rockets will be safer than those just off the assembly line.
Rocket reuse has an added benefit: low cost. Expended rockets couldn’t fly often because of the sheer expense and production limitations. Reusable rockets need not be constrained this way. They will fly frequently, uncovering new failure modes and new opportunities to improve.
When we consider that rockets aren’t necessarily more complicated than the aircraft we fly in and reusability makes it possible to test and refine them in the same way that we have with commercial aircraft, suddenly the possibility of rocket travel does not appear as remote.
Human progress has followed ever increasing speeds of transportation and communication. In the 19th century, it was the train, limited to 60 mph, that opened new frontiers. In the 20th, it was the plane, running up to 600mph. If we are smart, society will invest in new transportation modes that will unlock 6000 mph. Maybe someday, when everyone can have lunch in Beijing and at dinner applaud a Broadway show in New York, we will realize just how small, how fragile, the Earth and civilization really is.