How to Build Lunar Homes From Moon Dirt
An illustration of a planned moon rover that could carry the pneumatic digger, which excavates lunar dirt by injecting gas into the ground.
Credit: DigitalSpace/Jeroen Lapre

NEW YORK - When humans finally set up residence on the moon, our lives there will look very different.

Since many of the tried and true tools we use on Earth will be impossible to carry along, some scientists are hard at work inventing from scratch the machines we'll need to make life possible on the moon.

One such example is building equipment.

"Bulldozers and excavation systems are pretty bulky and heavy," said Kris Zacny, director of drilling and excavation systems at Honeybee Robotics in New York City. "We came out with a different method of digging that uses gas."

Zacny's invention digs up ground by injecting gas into the dirt, thereby creating a high-pressure situation from which the gas naturally wants to escape. When it does fly upward, the gas' strong momentum ends up taking dirt up with it.

Digging up the moon

In July 2008 Honeybee Robotics was awarded a contract to develop tools that will help astronauts live and work on the moon as part of NASA's Constellation program. Zacny has relied on the wisdom he gained working in diamond, coal and gold mines in South Africa, as well as his doctorate research on extraterrestrial excavation, to devise creative methods for digging up the moon, including the gas-blowing digger. Working with their NASA technical contacts, Rob Mueller and Greg Galloway, Zacny and his team hope to create tools that will one day prove their usefulness on the moon.

In detail, this so-called pneumatic excavation mechanism involves gas pumped into the ground through a thin tube encased by a wider hose. When the gas escapes, carrying along material from the ground, it travels up through the hose to a storage container.

"It's kind of like a vacuum cleaner, but the reverse," Zacny said. Instead of using suction, the machine injects gas down to draw material up.

The contraption weighs a lot less than conventional digging tools, though it begs the question: Where will future moon-dwellers get the gas needed to operate the machine?

One good source could be the carbon dioxide breathed out every day by astronauts, he said. Another option is to burn any leftover fuel in the rocket thrusters on the moon landing vehicle, and collect the exhaust.

"When a spacecraft lands on the moon, it has a little extra fuel left over, just in case you have to fly longer than you planned," Zacny said. "Once you land it's a deadweight."

But burning this fuel to create gas is great way to power the pneumatic excavator, he said.

Reduce, reuse, recycle

Once the device has sucked up lunar dirt, or regolith, this material could be conveniently diverted and used as a protective covering over homes (regolith is good for shielding from radiation). The dirt could also be processed to extract the oxygen bound up in its minerals.

In order to free up the oxygen trapped inside, regolith must be heated to high temperatures. Greg Mungas from Firestar Engineering, working with Zacny, proposed passing the material through a heat exchanger after it is extracted. Or, if the source of gas for the excavator is from leftover rocket fuel, then the exhaust will already be hot, and as it passes into the regolith it can heat the dirt up.

Since every bit of material that we carry to the moon adds expensive weight to the spacecraft travelling there, engineers must design as many thrifty ways as possible to get what they need from the moon and reuse resources.

"You're going to be recycling quite a bit," Zacny said. "It's like Lewis and Clark, living off the land."

For example, instead of carting up heavy water, astronauts could travel with hydrogen, and then add oxygen later. Since oxygen is the heavier ingredient in water, and it can be extracted from the surface, this approach saves precious cargo weight.

And once a store of water has been created for the lunar colony, most of it can be recycled without having to create more from scratch.

Lingering issues

Though engineers are well on their way toward preparing us for life on the moon, some major issues have yet to be resolved.

"Something that we'll have to consider is radiation," Zacny said. "We can close ourselves in habitats, but radiation protection requires a lot of shielding. We cannot solve this problem yet. Radiation can kill us."

Moon dwellers will also have to contend with the ubiquitous dust on the surface of the moon, which gets into everything and can wear down joints and connectors and prevent sealing off doors. It also poses a health risk to people, as it can cause breathing problems and is difficult to filter out of habitats.

Other difficulties may lie in the astronauts themselves, as opposed to the environment.

"You can have a lot of psychological issues," Zacny said. "On the International Space Station you can see Earth. If there's an emergency, in an hour and a half you can come home and be in the hospital. On the moon the Earth is farther away and you can feel detached."

Why go to the moon?

While many scientists are busy planning humanity's future on the moon, some people question whether we ought to be even trying to make it back to a place we conquered in 1969.

But Zacny argues the pursuit is worthwhile, not just in itself, but for the opportunity to invent new technologies and prepare for our eventual quest to Mars. Plus, we can't help but want to try living on another world besides Earth.

"We're going to explore. It's human nature," Zacny said. "It's just a matter of time before we establish some kind of base on the moon."

And when we do, Zacny would sign up in a heartbeat.

"I would go right now. I wouldn't even go back home first," he said. "It's the adventure of a lifetime."