December 26, 2015

Gravity is the next challenge

As the year closes, I find myself thinking about space.

I ended up reading several science fiction books this year. What I realized this morning is that I’ve spent a recognizable chunk of the year considering the logistics of space travel.

The Martian, which later became a successful movie, spent time considering Mars—getting to it, getting back to it, and getting off of it. Consider Phlebas, the first of Iain M Banks’ Culture series, has the protagonist entering and exiting multiple planets and solar systems with varying methods and levels of success. (I also read Player of Games and Use of Weapons (highly recommended!), which are the next two books in the series, but in general I think Banks spends more time in the culture (duh) than in space). Seveneves talks nearly exclusively and extensively about things in orbit or crossing earth’s orbit with the moon. Chinese author Liu Cixin dazzled me with The Three-Body Problem and its sequel, The Dark Forest, which tells of Earth’s response to the threat of extraterrestrial invasion—I expect the trilogy-concluding Death’s End to be my first book completed in 2016.

All this said, I’ve learned four things about this kind of travel.

  1. Nearly all energy expended in space travel is to escape gravity. The NASA spacecraft we easily envision is attached to enormous rocket thrusters which propel astronauts into space with a force that exceeds gravity’s pull.

  2. How much energy is expended is proportional to how much you’re carrying. As soon as they get into orbit, they jettison those big things because hauling around empty weight is going to limit how far you’re going to be able to go.

  3. Travel is limited by how much propulsion you have. Since we haven’t come up with perpetual machines, space travel depends on how much you have in the tank. And if that’s the case, you have to conserve for a round trip or accept a one-way ticket.

  4. Things settle into an orbit. Once you’ve run out of fuel (or you’ve just stopped thrusting) you don’t just stay in place; lesson number one kicks back in. Whatever gravity is around will have its way on you and you’ll follow the trajectory it takes—whether in a circle like the moon or on a far-reaching arc like a comet. How much hold gravity has on you determines which of these will be your course.

Having thought about this, I suddenly realized its analogy for my life.

Let’s say that birth was my takeoff. Successful launch, but I expend tremendous amounts of energy building an understanding of my orbital system. For me, that was Delaware. Then I went away my final two years of high school, propelling to another system. Moving from one system to another became my style, and I became efficient at it.

Do do that, though, you have to travel light and time your arrivals/departures well. You’ve only the energy of one life, after all. You become very strict about what you hold on to and how long you hang around. Alternatively, you find a group heading in the same direction and distribute the expense of propulsion to the next destination.

At some point, though, you may find yourself a long way from home with few others headed in your direction (whether that direction is home, a past destination or somewhere new). You’re in orbit of a gravity source that isn’t very interesting to you, and you don’t want to waste precious fuel. Maybe the group you’re with wants to stay around a little longer than you do, or they’ve decided they no longer want to travel further. Or maybe you went on solo and now are in search of the next target.

Here’s where the perpetual question arises again: should I stop planet hopping and become a satellite? Is this the best there is? Better than both moving, better than going back? And each time the question is asked, I imagine the lure of settling down becoming more inviting. You can add on more weighted comforts since you’ll only be adjusting position rather than charting a course. The orbit provides things like days and nights—things you can build life around.

I think that’s where I am right now. I think my wife is wanting to find a system where we can establish a low-power orbit. Increasingly, more friends are orbiting systems of their own with a scant few traveling their own course far, far away. The idea of permanent orbit, to me, sounds foreign; jetting back to another place to orbit with friends seems both permanent and wasteful; and catching up with far flung travelers seems downright illogical. So the natural thing for me to do is to look for a new planet to target.