Published on June 11th, 2013 | By: Eileen De Guire0
Ceramic Engineering in AerospacePublished on June 11th, 2013 | By: Eileen De Guire
[Image above] Credit: NASA
Engineered ceramics are increasingly being used in commercial and military aircraft, and have been used in the space shuttle and its equipment for many years. Ceramic applications include thermal protection systems in rocket exhaust cones, insulating tiles for the space shuttle, engine components, and ceramic coatings that are embedded into the windshield glass of many airplanes. These coatings are transparent and conduct electricity for keeping the glass clear from fog and ice.
Ceramic fibers are used as heat shields for fire protection and thermal insulation in aircraft and space shuttles because they resist heat, are lightweight and do not corrode. Other significant characteristics include high melting temperatures, resiliency, tensile strength and chemical inertness.
A non-oxide ceramic called silicon nitride has excellent high temperature strength, excellent fracture toughness, high hardness and unique tribological properties. Silicon nitride aerospace applications result in superior mechanical reliability and wear resistance allowing components to be used under minimal lubrication without wear. These include jet engine igniters, bearings, bushings, and other wear components.
Making Space Travel Possible
Advanced ceramics are playing a critical role in the development of highly-efficient and cost-effective new technologies for space travel. Morgan Technical Ceramics’ division in Erlangen, Germany has been working with a European space development program for a number of years to support its research of ion propulsion systems. A lightweight alternative to traditional chemical propulsion, ion engines have the potential to push spacecraft up to ten times faster with the same fuel consumption, thereby significantly decreasing vehicle size and increasing travel distance.
Ion propulsion technology, which uses electricity to charge heavy gas atoms that accelerate from the spacecraft at high velocity and push it forwards, traditionally incorporated quartz discharge vessels. Quartz has now been replaced by a ceramic oxide called alumina because of the need for a material with the same dielectric properties but with higher structural stability. Alumina is easier to fabricate and offers good thermal shock resistance, ensuring that the chamber can withstand the extremes of temperature that occur during plasma ignition. It is also lighter, which reduces the costs associated with each launch.
Providing Accurate Fuel Measurements
One of the most successful commercial aircrafts in recent times, the Boeing 777, uses piezoelectric ceramic material within the 60 ultrasonic fuel tank probes located on each aircraft. The ultrasonic transducers are installed at a variety of locations in each fuel tank. A pulsed electric field is applied to the ceramic material, which then responds by oscillating. The resulting sound waves are reflected off the surface of the fuel and picked up by the piezoelectric ceramic transducer. A digital signal processor interprets the ‘time of flight’ measurement of the sound waves in order to continually indicate the amount of fuel present. Similar ultrasonic fuel probes are also used in fighter aircraft and other level sensing applications because of their ability to provide highly accurate readings, regardless of the orientation of the aircraft.
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