Where to Park in Space

In 2012, when I served as the Engineering Director at Langley Research Center, NASA assigned a group of us the task of determining where to park a new outpost in space, one that would provide a waypoint between Earth and the Moon—an essential step to colonizing the Moon and then Mars. For four months, I commuted four days a week between my home in Virginia and the Johnson Space Center in Houston. I joined eight other engineers, mathematicians, and physicists in a meeting room dominated by a projection screen and a whiteboard. My fellow team members included experts in navigation, communications, rocketry, physics, and a bevy of other disciplines, including one astronaut. Taking turns with markers, we scribbled schematics, mathematical formulas, and mechanical drawings. We argued over politics, the sexiness of our locations, and the expense. But mostly we focused on the task at hand: to determine the ideal mission and point in deep space for the new outpost.

We had two good choices between Earth and the Moon: the Lagrangian points named L1 and L2. We had to come up with a plan for getting the station there safely, and parking it—stopping it—in exactly the right spot without wasting fuel. In addition, our job was to help create a railroad grade through space.

Let me explain in the simplest Lagrangian terms. The Apollo program was the equivalent of the Lewis & Clark expedition, a set of explorers who took the straightest possible path (as much as any path that involves multiple orbits around planetary bodies can be straight), over hills and mountains, using whatever energy it took to go from point A to point B. The astronauts went to the Moon, taking everything they needed with them, and then they returned home, all in about a week. My team dealt with the problem of shuttling equipment, supplies, and teams of people back and forth, not once but many times. Following the same path as Apollo would require enormous expenditures of fuel. It would be like trying to build a railroad simply by following Lewis & Clark, with cliffs and canyons along the way. Instead, we needed to discover the best grade, a “flat” course with the most neutral gravitational forces. This meant going a much longer distance to avoid the rough places.

We decided that L1, located closer to Earth than the Moon, was too easy. Getting there meant barely leaving our terrestrial neighborhood. L2, on the other hand, presented a challenge. It lies closer to the Moon than to Earth, and it would stretch our technological prowess to the fullest.
Four days out of every week, we met in front of the whiteboard and hashed out choices and plans. Some weeks, industry teams would join us to show their ideas. Then we went back to our homes and laboratories with individual assignments, enlisting small teams of brilliant NASA and university engineers in a host of disciplines to put meat on the bones of our concept. We presented our findings each following week at the Johnson Space Center. Our end result: a detailed plan consisting of designs, analysis, drawings, trajectories and cost estimates to park a space station at L2 with a direct view of deep space and the far side of the Moon.