Chinese scientists have created a new spaceship antenna to prevent the communications blackout that occurs when a craft is entering the atmosphere. When a vehicle travels at hypersonic speeds far above that of sound, it heats up and causes an envelope of hot, ionized air to develop around it. This is called a plasma sheath and it cuts off radio communications with any source outside it.
The modified spaceship antenna is expected to keep the communications lines open when it is coated with a double-positive material layer to match the plasma sheath wrapping the craft. Even Russian researchers are working on this vexing problem, and have suggested the possibility of using the plasma properties to force the sheath to appear transparent, thus stopping it from acting as a mirror against electromagnetic signals.
Harbin Institute of Technology’s Xiaotian Gao and Binhao Jiang explain that maintaining communications even while a spaceship reenters Earth’s atmosphere could be achieved by setting up resonance in the plasma sheath. The last mentioned and the matched layer are required to be thinner than the wavelengths of the radio signals employed for communications. The properties of the sheath are likely to vary when in flight.
So the electromagnetic properties are required to be altered electrically via an automatic control mechanism. Published in the Journal of Applied Physics, the scientists behind the study have not constructed the proposed hypersonic communications system, but have only laid out the theory. They hope that their findings will help engineers across the globe who wish to bring such an antenna system into practical use.
The advantage of using the redesigned spaceship antenna is that it seems to be fairly simple to execute in theory and does not need the vehicle to obey any rules of aerodynamic shaping in order to function as promised. Additionally, it might come in handy for hypersonic passenger jets, military planes, intercontinental ballistic missiles and so on.