When the Mars Sample Return mission faces the chore of collecting rock cores to bring back to Earth, sometime during 2004, the whole mission will be standing on the head of a pin, Stephen Gorevan likes to say.
"We're going to be that pin."
Gorevan is chairman and co-founder of Honeybee Robotics, a small firm doing big business with NASA.
From the second and third floors of an industrial loft above a muffin factory in Manhattan's Little Italy, Honeybee's inventors build miniature machines for NASA -- components bound for Mars, wayward asteroids and distant comets.
Now, Honeybee is finessing the final details of a crucial component of the Mars Sample Return missions -- a robotic drill that will bore into martian rocks, remove core samples, and place them in a cache that will eventually be returned to Earth on a French orbiter.
Honeybee is building the drill that will be carried by the Athena Rovers NASA plans to send to Mars in both 2003 and 2005. About four feet long and four feet wide, the six-wheeled buggies will weigh about 150-pounds (near 70 kilograms) and will be able to travel up to 100 meters a day. They will carry a suite of scientific instruments for studying the surface of Mars. The budget for the two rovers is about $100 million.
Each of the rovers will carry Honeybee's mini-corer, a miniature robotic drill capable of boring about two inches (five centimeters) into a rock and removing a core about an inch long and slightly thicker than a pencil.
Gorevan and his partner Chris Chadman founded Honeybee in 1983. That year they began working on robotics for space station components. In 1989 later they began research for a drill for interplanetary missions, and have been dabbling with drills ever since.
"On Earth you have apparently unlimited power, unlimited torque, and in all cases there is a human there to fix it if anything breaks," Gorevan said. "On Mars, everything has to be super-efficient and hyper-reliable."
Honeybee's mini-corer relies on a unique bit design that operates efficiently using very little energy. There is only one way to cut into strong rocks with low power -- thrust and torque, Gorevan said. That is accomplished by using a super strong and sharp bit with only one cutting tooth. Honeybee's engineers have found a design that spreads the cutting area of a single tooth to three points of a cylindrical bit. This gives the drill adequate cutting surface while minimizing the friction.
The key to the drill's success will be patience. "It takes a little bit of time, but that's something we have plenty of," Gorevan said. Depending on the hardness of martian rock, it could take four hours to drill two inches.
The drill passed its first milestone earlier this summer during tests of an Athena Rover prototype in California's Mohave Desert. A team of rover engineers and scientists used the cameras to guide the vehicle around the rocky terrain. They choose targets for drilling and cored into them with the Honeybee drill. "It really worked wonderfully," said Steven Squyres, the principal investigator for the Athena rovers and a Cornell University planetary scientist.
The mini-corer's bit is hollow in the center. It cuts a circular channel around a narrow cylinder of rock as it bores. When the drill reaches a target depth, it breaks off the core inside, removes the rocky ladyfinger and inserts it into a cache in the rover.
The cache will hold as many as 45 cores. After about 90 days of exploring the surface and drilling into rocks to collect core samples, the rover will return to the lander and insert its cache of rocky cylinders into a rocket that will launch the cargo into Mars orbit. Years later a French spacecraft will attempt to rendezvous with the orbiting samples to bring them back to Earth.
With just 18 engineers on staff, Gorevan said Honeybee's size is an asset when it comes to building many one- and two-of-a-kind components for NASA missions. "We're a small company, but we're very nimble."
The chore of building interplanetary spacecraft components presents obstacles rarely encountered when making devices for terrestrial use. Gorevan and his team have had to use specialized metals, some even toxic, in order to build a machine that will be least affected by extreme temperature shifts on Mars.
Temperatures during a martian day can rise as much as 180 degrees Fahrenheit (82 degrees Celsius) over the pre-dawn chill. Engineers must find materials that expand and contract as little as possible through such temperature variations. They also must find materials that expand and contract at the same rate.
Testing for martian conditions is also tough. No one is certain how fine the red martian dust is, but many planetary scientists think its grains are smaller than anything that exists on Earth, perhaps ten times smaller than the finest talc. Sealing out such fine-grained powdery dust is a high priority in equipment design, but there is no way to test whether the designs for sealing Honeybee's drill will actually work. Gorevan said Honeybee is having about a hundred grams of such fine-grained particles made in order to test the drill in simulated martian dust. The cost of grinding such dust could be several thousand dollars, he said.
With only seven months remaining before a complete drill must be delivered to NASA, the pressure is on. The first engineering model must be delivered to NASA's Jet Propulsion Laboratory by April, and many of the custom manufactured parts will take at least 12 weeks to fabricate. Figuring time for assembly, the deadline for completion of the engineering is essentially now, Goreven said.
"We're kind of awestruck here because this whole project, including the French orbiter, is costing well over a billion dollars and the feeling is that the whole purpose of this mission is to get these samples back. The whole world of the planetary science community, and more -- because of the possibility of life on Mars -- is watching, so the pressure is enormous. But it's exciting, too."
