Meanwhile, the planners keep planning. Maybe the most dramatic use of an L2 outpost is one proposed by the Keck Institute for Space Studies in cooperation with NASA’s Jet Propulsion Laboratory in California. They describe a mission in which a robotic spacecraft chases down a schoolbus-size asteroid, captures it, and brings it to the vicinity of the moon. There, astronauts could practice spacewalking around a small asteroid, extract water to make rocket fuel, and take inventory of its minerals.
The notion of capturing and relocating a half-million-pound asteroid began “as one of those ideas that when you first tell somebody about it, they look at you with glazed eyes,” says Louis Friedman, executive director emeritus of The Planetary Society and a co-leader of the study. “Then you get into it, and all of a sudden it becomes obvious to people that this is the only way to get astronauts to an asteroid in the 2020s.” Friedman says NASA has taken a serious interest in the proposal, and the agency said in a statement that it is examining the plan “to determine its feasibility.”
“The gut feeling is that we like L2, but it turns out that if an object is at L2 and let go, it will be unstable and could drift away” and possibly crash to Earth, Friedman says—although an object as small as this 23-foot-wide asteroid would burn up in the atmosphere. One problem is finding the right asteroid, he says. There are “millions out there,” but NASA and its international partners would need to set up a dedicated program to shop for candidates of the right size and type. The robot spacecraft would approach the asteroid, match its tumbling motion, and use a soft, inflatable bag in the spacecraft’s nose to grab it. Then the spacecraft would “de-spin” the asteroid and bring it near the moon. The entire capture mission would take anywhere between five and a half and 10 years, depending on the asteroid’s initial orbit and its mass.
As of early this year, NASA has not committed to an L2 mission. “The Lagrange points are very intriguing to us,” Gerstenmaier says, but adds that Gateway might turn out to be more challenging than it seems. “We need to know if there are too many unknowns. Am I not pushing hard enough? Or am I pushing too hard?” The most likely message to NASA from space enthusiasts? Push.