How to Leave Space and (Safely Crash Back Down to Earth

THERE ARE SEVERAL key things that every spaceship has to do if it wants to leave orbit and come back to Earth. The most obvious is changing its flight path to bend down toward the atmosphere, where the air drag will capture it and bring it relentlessly down to the surface. Next is withstanding the tremendous temperatures of reentry. Changing your flight path angle in an airplane is a relatively easy thing; you push forward on the stick and the air pressure on the elevator moves the nose of the airplane down and the trees get bigger. Pull back on the stick and the trees get smaller. However, in space we have Sir Isaac Newton to thank for a very useful trick that allows astronauts to come home. Orbital mechanics are what determine a spacecraft’s motion once in space, and to change your course to the left or right you need a tremendous amount of delta-v, or change in speed. Because of this, it’s very inefficient to change your inclination, or heading. Most human spacecraft carry only enough rocket fuel to change their heading by a few tenths of a degree to the left or right. The good news is that we don’t have to move left or right to come back to Earth, we just need to go down. Here’s where the useful trick comes in handy—if you slow down, your orbit will descend. Conversely, speeding up makes your orbit climb. The amount of delta-v required for this trick is much less than for changing your inclination.

It was at EI that the shuttle and Soyuz experience diverged. Dramatically. The space shuttle was a magnificent flying machine, roughly the size of an airliner, and once it was back in the atmosphere it could bank and turn and maneuver like a normal plane. Except it was traveling at 17,500 mph and was surrounded by a cocoon of plasma that was as hot as the sun, created by the indescribable friction of the massive shuttle smashing into unsuspecting O2 and N2 molecules of the vanishingly thin upper atmosphere. The view from the pilot’s seat returning to Earth that night in February was spectacular. At first there was a gentle pink glow outside my window, then it began to radiate a brighter orange and then red, accompanied by a flashing white light above the overhead window, reminding me of the scene in Alien when the strobe light was flashing while the ship was getting ready to self-destruct. This final phase of my mission took place in darkness, so I was able to see every nuance of the colorful plasma. It finally turned gray, and I raised the visor on my helmet and leaned over to the window. The plasma was slowly swirling around, like eddies and currents on a pond. I reached up, pulled my hand out of my glove, and felt the window, which surprisingly wasn’t at all hot. The most bizarre thing was a very distinct yet faint sound, like tapping your fingertips gently on a counter. I guess I expected burning sounds or air rushing sounds.