Aerospace. Legacy Systems. Unmanned Air Vehicles

Computer technologies have helped provide a continuum of improvements in aircraft performance that has allowed the airspace where aircraft operate to increase in range and altitude. Landau (1) defines aerospace as the Earth’s atmosphere and the space outside it, considered as one continuous field. Because of its rapidly increasing domain of air and space travel, the U. S. Air Force is beginning to refer to itself as the U. S. Aerospace Force.

Modern air-space vehicles are becoming increasingly dependent on information gleaned from ground stations, satellites, other air-space vehicles, and onboard sensors to perform their mission. These vehicles use signals across the electromagnetic spectrum. Antennas can be found in multiple locations on wings, the fuselage, tails, and draglines. If antennas are located too close together, their signals can interfere with each other, called crossed frequency transmission.

This interference reduces the efficiency of each affected antenna. Placement of multiple antennas requires minimizing the effects of crossed frequency transmissions. Techniques for minimization include antenna placement, filtering, and timing, which presents another challenge for aircraft computers to sort and process these multiple signals. Perry and Geppert (4) show how the aircraft electromagnetic spectrum is becoming busy, and thus, dangerous for aerospace communications.

Legacy Systems. Legacy systems are fielded aircraft, or aircraft that are in active use. Probably the only nonlegacy aircraft are experimental or prototype versions. Legacy aircraft are often associated with aging issues, more commonly known as parts obsolescence. A growing problem in these systems is the obsolescence of entire components, including the many computers used on them. Aircraft, like many other systems, are designed with expected lifetimes of 10 to 15 years.

Because of the high replacement costs, lifetimes are often doubled and tripled by rebuilding and updating the aircraft. To reduce costs, as many of the original aircraft components as possible are kept. Problems develop when these components are no longer produced or stockpiled. Sometimes, subsystems and their interfaces have to be completely redesigned and produced at great cost in order to keep an aircraft in service.

System architectures and standard interfaces are constantly being modified to address these issues. Aircraft evolve during their lifetimes to a more open architecture. This open architecture, in turn, allows the aircraft components to be more easily replaced, thus making further evolution less expensive.

Unmanned Air Vehicles. Unmanned air vehicles (UAVs) are aircraft that are flown without aircrews. Their use is becoming increasingly popular for military applications. Many of the new capabilities of UAVs come from the improved computers.

These computers allow the vehicles to have increased levels ofauton- omy and to perform missions that once required piloted aircraft. Some of these missions include reconnaissance and surveillance. These same types of missions are finding increasing commercial importance. UAVs offer tremendous advantages in lifecycle cost reductions because of their small size, ease of operation, and ability to be adapted to missions.