Introduction
MARY KAE LOCKWOOD
NASA Langley Research Center
Hampton, Virginia
JOHN W. WEATHERLY
U.S. Army Cold Regions Research and Engineering Laboratory
Hanover, New Hampshire
Designing for extreme environments presents unique challenges for engineers. Materials and devices must be able to function in remote locations and under very harsh conditions, such as extreme natural environments (e.g., polar regions, deep oceans, and high-current rivers), man-made environments (e.g., the inside of a nuclear facility or a space vehicle), and in space (e.g., on the surface of the Moon or Mars). In addition, engineering for extreme environments involves many uncertainties—about specific environmental conditions, about the physics under extreme environmental conditions, about the accuracy of laboratory simulations, and about meeting difficult schedule and cost requirements.
The Antarctic plateau is a unique environment for studying the upper atmosphere at very high magnetic latitudes and a range of longitudes. One can envision a “network” of robots, with instruments secured, being deployed from the South Pole station to locations on a geomagnetic grid on the surface of the plateau for long- or short-term observation. The robots might be retrieved or repositioned through iridium-based communication. Very large-scale arrays of robots can provide ground-based, distributed, mobile “antennas” as an alternative, real-time communication and high-bandwidth data-transmission link to the iridium system. With a sufficiently stable robotic platform, a wide range of instruments, from seismometers to radio receivers, could be deployed. Robot networks would enable field workers to take advantage of the value of large sensor arrays for geophysical sciences and ecology. Robots would also be much less expensive than stationary observatories (which are ideal for long-term
observation but prohibitively expensive for the deployment of very large-scale instrument networks).
The construction of the Tacoma Narrows Bridge is an example of engineering in an extreme environment that presented significant technical challenges and strict schedule constraints. A complex, cable-supported anchoring system was necessary to stabilize massive floating concrete caissons 80 × 130 × 150 feet deep. The project required accurate predictions of large current-driven, time-dependent loads on the floating, but stabilized caissons. However, no relevant field measurements for similar structures or experimental scale models were available. Researchers, therefore, used state-of-the-art computational fluid-dynamics methods combined with an aggressive team approach to meet the extreme technical challenges and the tight schedule constraints. A similar approach, with specifically tailored computational fluid-dynamics analyses, was used for the design of a pulsed-jet mixer system for the construction of the largest nuclear-waste processing plant in the United States.
In January 2004, two Mars explorer rover (MER) spacecraft—Spirit and Opportunity—were successfully landed on Mars. The entry, descent, and landing systems were designed to slow the spacecraft from a velocity of almost 6 km/ sec at the edge of the Martian atmosphere to nearly zero velocity approximately 12 m above the Martian surface to enable the safe release of the airbag/landing system. The MER landings followed earlier successes—the landings of two Viking missions and the Mars Pathfinder. Future Mars landings, such as the Mars Science Laboratory mission slated for launch in 2009, will include a sky-crane landing system that can set down larger mass robotic systems on the Martian surface.
The recent announcement by President Bush of a new vision for space exploration, including human travel to the Moon, Mars, and beyond, will present many additional challenges in the design, development, and testing of systems for human missions in extreme environments. Researchers are already assessing systems for supplying astronauts with artificial gravity to minimize bone decalcification and provide an accommodating environment for the long transit from Earth to Mars. Investigations of previously unexplored regions of the Moon, such as the polar caps, are also being considered. Because temperatures in those areas have remained below 40K for millions of years, the environment has remained unchanged for millions of years.
These are only a few examples of the risks and rewards of engineering for extreme environments. Innovative solutions have been, and will continue to be, applied to some extremely challenging problems.
