When NASA launched the Pathfinder mission last summer, the world got a glimpse of the Martian surface. Now, we may get an even closer look at the planet with the help of a custom-built plane.
To date, Mars exploration has been limited to a small geographical area and to information gleaned from imaging systems. But now, NASA is dangling the prospect of a US$299 million grant to the organization that comes up with the most compelling space exploration proposal. So far, 29 groups have submitted proposals, and of those, seven are Mars exploration missions. NASA has set the expedition date for 2003, the centenary of the Wright brothers' first flight at Kitty Hawk, North Carolina.
One proposal, dubbed the Kitty Hawk, is designed to be the first airplane flight on Mars, and would cruise 1,100 miles across the Valles Marineris, a canyon system about 1,860 miles long and up to 5 miles deep.
"Its primary purpose is to deduce the history of Valles Marineris," said Larry Lemke, chief of the advanced projects branch at NASA's Ames Research Center in Mountain View, California, and the chief engineer behind the Kitty Hawk project. "Depending on what the outcome is, it could have implications as to whether there was, is, or could be life on Mars."
Designing a plane for Mars poses significant challenges for the scientists. Both the Kitty Hawk project and another proposal involving a glider would use a rocket to send the plane to Mars, a 48.6 million-mile journey that would take seven to eight months. Given that Martian atmospheric pressure is only 1 percent that of Earth's, it's a safe bet that the plane designs will require space-age technology. But in many respects, the plane designs are rather ordinary, which could work in their favor.
"The simpler the aircraft, the less things that that can go wrong," said Lemke.
The Kitty Hawk project leader, Michael Malin, is the president of Malin Space Science Systems, a San Diego company that designs instruments that fly on robotic space craft. Malin is working with the Ames facility, the Naval Research Laboratories in Washington, DC, and Orbital Sciences Corp. of Dulles, VA. on the project.
The second Mars project is being advanced by Pasadena's Jet Propulsion Laboratory, in conjunction with the US Geological Survey in Flagstaff, Arizona. The plan is similar to the Kitty Hawk project, but substitutes a glider plane for the proposed 20-minute reconnaisance mission.
Some observers compare the challenge of flying a plane on Mars to the Wright brothers' original flight.
"I imagine that trying to build an aircraft that would fly on Mars would be an enormously complex task," said Tad McGeer, president of The Insitu Group, an aerospace research and development firm that was recently involved in flying the first unmanned aircraft across the Atlantic Ocean. "You would need ridiculously low wing loading and with no oxygen on Mars, you couldn't even use an internal combustion engine."
Given the extremely low atmospheric pressure, the scientists said it will be difficult to generate the lift needed to keep the plane in the air. The good news is that the gravitational pull on Mars is approximately one third of that on Earth, so less overall lift is needed. And in general, the wider the wingspan the greater the lift. Combining these factors, scientist Mike Ravine, advanced project manager at Malin, said that the mission would be the rough equivalent of flying an aircraft at 80,000 feet.
Lemke explains, "The amount of aerodynamic lift is equal and opposite to the aircraft's weight." Therefore, it becomes a balancing act between weight and wingspan.
"Our aircraft looks more like a flying wing than an airplane," said Ravine. "The wingspan will be approximately 32 feet across. It will be powered by a push propeller from behind."
Another consideration is that the aircraft has to be rocketed through 48.6 million miles of space, limiting the overall size of the craft. To combat this problem, both projects propose planes with wings that can be folded during the rocket phase, and then opened out for the flight.
"NRL has a lot of experience building aircrafts that can both fold their wings and fly at very high altitudes, while Orbital Sciences can build the rocket and capsule that will get the aircraft to Mars," said Lemke.
The Kitty Hawk aircraft would be powered by hydrazine, or rocket fuel, which does not require oxygen. The proposal also calls for the plane to be built using aluminum and carbon composite material, which is light but durable.
The proposed Kitty Hawk flight will last about three-and-a-half hours, with the airplane traveling roughly 1,000 miles at 1.2 kilometers above the canyon. During the flight, 20-30 gigabits of data will be collected and transmitted to the rocket orbiting overhead, which will relay the information to Earth. The aircraft will house instruments to measure gravity and both magnetic and electrical fields. Other instruments on board include a laser altimeter, several high-resolution cameras, and an infrared spectrometer.
"By measuring the electric[al] and magnetic fields, we will get some idea of what the Martian sub-surface is like, giving us some indication if there could be, for example, underground aquifers," said Ravine.
The JPL's glider proposal also aims to survey the Valles Marineris, but would only be aloft for about twenty minutes.
If either project goes ahead, it will be one of only several Martian expeditions planned in the next five years. In December 1998 and January 1999, NASA will send up two missions: the Mars Global Surveyor Orbiter and the Lander. The agency also plans to send up expeditions in 2001, 2003, and possibly 2005.
