A picture of a proposed Mars airplane from NASA Ames Research Center.
By John F. McGowan, Ph.D.
December 3, 1999
Neither manned landings nor stationary or slow, short range robotic probes such as Mars Pathfinder can explore the surface area of Mars, 144 million square kilometers comprising as much surface as all the continents and islands on Earth. For example, a half million manned or robotic landings capable of surveying a 300 square kilometer region of the Martian surface will be needed to survey the surface of Mars once (1). The handful of astronauts likely to be sent to Mars in manned missions, even equipped with rocket planes or ballistic hoppers, will directly survey only a tiny fraction of the planet. A complete survey of Mars will require high speed low altitude or ground based devices, either remotely piloted, semi-autonomous, or autonomous, such as airplanes, balloons, or high speed rovers (2-7). Fast moving robotic explorers will need high frame rate imaging, such as digital video, to properly survey the planet and for remote operation either by astronauts on Mars or mission control on Earth. They will also generate very high data rates compared to current Mars to Earth communication data rates.
NASA emphasizes the search for water and past or present life on Mars. On Earth, liquid water is an absolute requirement for life. Mars is currently quite desolate by terrestrial standards. The thin carbon dioxide atmosphere is less than one percent of Earth's atmosphere. Ultraviolet light bombards the surface. Mars lacks the magnetic field that appears to protect the Earth from a variety of radiations. There is very little water. However, Mars contains a number of canyons that appear to have been cut by flowing water and various other features that suggest a large amount of liquid water in the past. According to one theory, Mars was much warmer and wetter in the past. Life may have developed and even flourished during this period, leaving traces or even surviving life. Traces of past or present life may require an extensive search of the planet to locate or to conclusively demonstrate that life never existed on the planet.
The gigantic Valles Marineris canyon on Mars is of particular interest. The canyon is approximately 2,000 miles long, 300 miles across in places, and several miles deep. The canyon or parts of the canyon may have been formed by water in the past. It is a good place to look for sedimentary rocks, that is rocks laid down by water over time. However Valles Marineris was formed, it is a rift several miles deep into the surface of Mars, probably revealing rocks and other features inaccessible on other parts of the planet. The canyon appears to contain gigantic landslides that may have exposed materials from deep beneath the surface. Thus there is considerable interest in exploring the canyon.
There have been a number of proposals to fly airplanes on Mars. Development Sciences Incorporated published a study of a remotely piloted Mars aircraft for NASA's Jet Propulsion Laboratory (JPL) in 1978 (2). This vehicle was designed for a short, few hour flight. Anthony Colozza of NASA Lewis Research Center (now Glenn Research Center) and Sverdrup Technology Inc. presented a paper on a long-endurance Mars aircraft at the 1990 AIAA/SAE/ASME/ASEE Joint Propulsion Conference (3). He proposed a solar or radioisotope powered airplane that would fly for months or even years in the Martian atmosphere.
In 1998, Malin Space Science Systems, Orbital Sciences Corporation, the Naval Research Laboratory, and NASA's Ames Research Center proposed a mission formally known as the Mars Airborne Geophysical Explorer (MAGE) to send an airplane dubbed the "Kitty Hawk" to Mars to make a three-hour flight over the Valles Marineris canyon on Mars. The flight was planned to take place on December 17, 2003, the centennial of the first successful powered flight by the Wright brothers. This proposal was submitted to NASA's Discovery program. The Discovery program funds low-cost innovative solar system exploration missions. Larry Lemke of NASA's Ames Research Center played a leading role in this proposal and made several presentations during the summer of 1998 including a talk at the founding convention of the Mars Society in Boulder, Colorado. This proposal was not selected during the competition for the Discovery program missions.
NASA included a stripped down Mars airplane as the first in a series of planned micromissions to Mars in its Fiscal Year 2000 Budget Proposal, unveiled at a press conference on Monday, February 1, 1999. The micromissions are relatively low cost, small and light-weight spacecraft, weighing no more than 220 kilograms (485 pounds), that can be piggybacked on Ariane rocket launches by the French space agency CNES. In principle, the micromissions will cost no more than $50 million. NASA Administrator Daniel Goldin featured the Mars Airplane mission and several other proposed missions in his presentation. This smaller airplane, with fewer instruments, would have flown down the Valles Marineris canyon for about thirty minutes, again on December 17, 2003.
Subsequently, NASA staged a competition between several NASA centers including Ames Research Center, the Jet Propulsion Laboratory, and the Langley Research Center to lead the effort. Each center assembled a team to draft a proposal for the Mars Airplane. NASA selected Langley Research Center to lead the effort. The Mars Airplane was then subsequently dropped as the first Mars micromission in favor of a Mars communication satellite proposed by NASA's Jet Propulsion Laboratory. The Jet Propulsion Laboratory has proposed a constellation of communication satellites orbiting Mars, known as the Mars Network, to improve communications on Mars and from Mars to Earth. NASA announced the decision on Monday, November 29, 1999.
Communication issues are quite important for Mars Airplanes and other mobile robotic explorers. From a scientific point of view, to be worthwhile, these robots must take data frequently to provide complete coverage of their journey across the surface of Mars. If the robots only provide data from a few locations along their journey, they are not much better than the stationary landers. The mobile robots will generate large amounts of data that must be shipped back to Earth for analysis. From a political point of view, the mobile robots can generate the most public support for space exploration if they can televise their journeys, which typically requires a data rate of at least one million bits per second using current video compression technologies (8,9). These data rates exceed the 5,000 to 100,000 bits per second data rates currently possible from Mars to Earth.
Mars Airplanes cannot carry the directional high gain antennas needed to beam data directly back to Earth at high data rates. Many other mobile robots will suffer similar limitations. Similarly stationary landers such as Mars Pathfinder have relied on orbiters to relay data back to Earth at high rates. Thus a strong case can be made for establishing a powerful store and forward relay system on or near Mars. With current and near future communication technologies, Mars Airplanes and other mobile robotic explorers will almost certainly require such a relay system.
© 1999 2003, by John F. McGowan, Ph.D.
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