During this morning’s browsing session of the blogs I follow, I came across this post from Self Aware Patterns, which led me to a brilliant article about the realities of space travel titled The Tyranny of the Rocket Equation by Don Pettit, a NASA astronaut and flight engineer. I say brilliant, because his writing is simple and succinct, and he explains complex engineering challenges in everyday language for the likes of me to understand.
If you are not into science and engineering, you won’t want to read the NASA article. However, I know that a good portion of my readers are engineering and science buffs. Every one of you will enjoy Pettit’s article – unless you are a rocket scientist yourself, in which case this is Rockets 101.
The majority of the human race will never know what it’s like to launch – and then land – in a space shuttle. Fourteen humans died trying it. No human from here on forth will ever again experience the space shuttle. It’s now a historic vehicle. But the trusty old Soyuz capsule still flies and is currently the only human rated spacecraft available to reach the International Space Station (ISS) and return from it. I got a kick out of Pettit’s one sentence description of what it’s like to land in a Soyuz capsule:
The Soyuz goes thump, roll, roll, roll; aptly described by one of my colleagues as a series of explosions followed by a car wreck.
Most of the article deals with the complexities and the physics involved in rocket science, and its practical limitations based on today’s technology. He compares the shuttle’s external tank with a soda can:
The common soda can, a marvel of mass production, is 94% soda and 6% can by mass. Compare that to the external tank for the Space Shuttle at 96% propellant and thus, 4% structure. The external tank, big enough inside to hold a barn dance, contains cryogenic fluids at 20 degrees above absolute zero (0 Kelvin), pressurized to 60 pounds per square inch, (for a tank this size, such pressure represents a huge amount of stored energy) and can withstand 3gs while pumping out propellant at 1.5 metric tons per second. The level of engineering knowledge behind such a device in our time is every bit as amazing and cutting-edge as the construction of the pyramids was for their time.
The stunning revelation is that the external tank has proportionally less material than a soda can, yet it flies into space. No wonder things did not go so well when the Challenger O-rings failed.
This article was first written in May 2012, before SpaceX made its major headline and surfaced as a viable player in the rocket world. I appreciate all the more the successes of SpaceX after reading The Tyranny of the Rocket Equation.