Leaping Lunar Landers!
Can a spacecraft hop its way to winning the Google Lunar X prize?
- By Michael Belfiore
- Air & Space magazine, September 2011
(Page 3 of 4)
Still, Joyce and his partners feel that their rover’s hopping ability gives them significant advantages over the other teams, which all use wheeled designs. Other teams will have to build a separate spacecraft to get to the moon as well as a rover, which the spacecraft will release after landing. But in the case of Next Giant Leap, the spacecraft is the rover, or, rather, hopper. Besides having to build and test only one vehicle, the team can also greatly reduce its launch weight, and thus expense. Instead of the Falcon 9 that Astrobotic plans to use, Next Giant Leap will be able to leave Earth on the smaller and less expensive Falcon 1e (that vehicle costs $10.9 million, versus $54 million for the Falcon 9).
If all goes well with the launch, the Next Giant Leap vehicle will jettison its protective aeroshell and detach itself from the Falcon in low Earth orbit. Next it will fire and then jettison the first of three booster rocket stages to head to the moon. Five days later, the second stage will fire to insert the craft into lunar orbit. The vehicle will then use the last stage for most of the descent, jettisoning it within just a few miles of the surface to make a gentle touchdown with its onboard thrusters—small rocket motors rather than the cold-gas thrusters that were tested in the Draper lab. One of its first tasks will be to send an encrypted data package back to Earth that will include the first high-definition video broadcast, e-mail, and Twitter and Facebook posts from the moon. That accomplished, the machine will relight its thrusters to make the prize-winning 500-meter hop. Then it will make one more hop to cover the remainder of the five kilometers for the distance bonus.
According to Sierra Nevada’s Mosher, not much has to be done to his company’s standardized satellite bus to make it moon-worthy. Aside from adding landing gear, communications equipment, thrusters, and cameras, he says, the major physical modification will be the addition of the propulsion stages.
As this article went to press, Cohanim and his MIT students had gotten their terrestrial vehicle to hover for short periods and then descend smoothly. Still to accomplish were stable ascents to a hover, and long-duration hovers. A stable ascent has proven especially elusive. “It always seems like it’s just one issue away: If we solve this next issue, then we’ll be done,” says Cohanim. He attributes much of the difficulty to the spinning, vibrating ducted fans and their temperamental output. That won’t be a problem on the all-thruster lunar vehicle. Says Cohanim: “We always assumed that the lunar problem actually would be easier.”
“None of the technical challenges are insurmountable,” says Mosher. “We understand how to do this job technically. The challenge is how do you make the financial/business model work for this.”
Draper is committing $1 million for the development of the TALARIS testbed vehicle. The vehicle provides a platform for developing the guidance, navigation, and control software for Next Giant Leap. The software that enables TALARIS to use its cold gas thrusters to seamlessly transition from ascents to hovers to descents, says Cohanim, will transfer directly to the actual lunar vehicle; only the hardware will change.
The software and hardware for imaging and recognizing such ground hazards as craters and boulders and for plotting landing patterns around them, as well as for firing thrusters in finely timed bursts for precision-control flight—all will work the same way on the moon as in the lab. But SpaceX will have to be paid for the rocket launch, as will Sierra Nevada for the modified satellite bus. While the technical challenges are on their way to being solved, the financial side of the equation is daunting, especially for a team leader who isn’t independently wealthy.
Joyce is no stranger to financial risk. He bet his livelihood that a business selling full-scale versions of a 1960s TV show robot would succeed—and he won. Shooting the moon might seem harder, but he’s never been one to play it safe. “You can choose to follow your dreams,” he says. “Or you can choose to do what everybody tells you is the right thing to do—the right career move, the right job to get, car to buy, place to live. But I recommend following your dreams. There are no guarantees, of course. We might end up bankrupt here in the next few years, but I’ve never been too concerned about losing it all.”
Joyce’s major task now is to try to raise money from researchers who want to send science payloads to the moon and from corporate sponsors who hope participating in the mission will have marketing value (first logo on the moon, anyone?).
Draper’s director of space systems, Seamus Tuohy, takes the long view. He feels the hopper concept regardless of who ends up buying it, will have its day in the sun. The hopper, he says, will be able to go where no planetary robot has gone before: exploring the interiors of craters or the tops of mountains, for instance. He likens it to a kind of helicopter that will be able to explore wide regions of a planet or moon, limited only by the amount of propellant on board. Says Tuohy: “What I keep telling the engineers is this: ‘We ain’t going next year. If it’s not next year, it could be the next year, maybe the year after. We’re sowing the seeds right now that may take 10 years to capitalize on. But we’re going to look back and say that it started here.’ ”