ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Hypersonic test vehicles require extensive data acquisition in order to accurately determine and refine engine performance. The increasing speed of scramjet engines places new constraints on data manipulation and system control. A compact modular flight computer has been developed that has high speed analog data acquisition, a programmable high data rate PCM (Pulse Code Modulation) encoder, compact data storage, and high speed I/O (Input/Output) capabilities. Principle to the design is the thermal management required for space environments. A functional overview is presented together with a summary of the analog performance. The integration of future capability requirements is also discussed.

ITC/USA 2009 Conference Proceedings / The Forty-Fifth Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2009 / Riviera Hotel & Convention Center, Las Vegas, Nevada / At about Mach number 10 and above, a high energy plasma field forms around a vehicle. This plasma sheath has a high attenuation factor that can cause communications black out. No practical solutions to communicating through a plasma sheath are known. In addition to standard real time data needs for test, a driving requirement to solve this problem is that most solutions will have to be designed into the vehicle. Modifications of vehicles designed to travel at these Mach numbers, especially any exterior modifications, will be extremely difficult due to effects on aerodynamics, thermal protection, and the materials used. A list of possible solutions to communications through hypersonically induced plasma has been collected over several years. This list was added to and verified during the Workshop on Communications through Plasma during Hypersonic Flight. Pros and cons of these potential solutions have been discussed and documented as well. The workshop also included a vote by the attending experts on what solutions are most promising. This paper reviews these solutions, their pros and cons, and a recommended way forward to solving this problem.

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<p dir="ltr">Hypersonic flight is the key to unlocking a nation’s strategic advantage in this century’s military theater. Military powerhouses such as the United States, Russia, India, China, Australia, and the EU publicly possess hypersonic weapons capabilities. Such technology enables intercontinental travel orders of magnitude faster than conventional flights. A trip halfway across the world would take not twenty hours, but two. However, the level of thermal and chemical load the aircraft and these electronic equipment experience while at such high speeds cause them to fail. Thus, ceramic window materials are used to act as a barrier between the hypersonic flight environment and this sensitive electronic equipment. Such materials need to be both mechanically robust, but transparent within the relevant infrared ranges used for target detection. Single-crystal sapphire (alumina) is an infrared window material readily available, plentiful, and easy to microstructurally control and manufacture, but not optimal. Its transparency range is limited to the optical and near-infrared, while it exhibits poor mechanical and dielectric strength. Polycrystalline alumina (PCA) has recently been shown to possess more favorable infrared window characteristics as opposed to its single-crystal counterpart. This is achieved by processing using a platelet powder morphology in a single processing step – hot-pressing. Full densification (> 99.5%) of PCA samples was achieved, demonstrating maximum of 84% optical transparency, but accompanied by grain growth (60+µm), resulting in lower mechanical strength. This research thus works on a two-fold approach to minimizing the grain growth of PCA. Optical tests demonstrated favorable results for lowering isothermal temperatures to reduce grain growth. Weibull values of m = 28.8 and m = 9.7 from 4 point-flexure tests were obtained (ASTM 1161a). Thermal loading via ablation testing compared PCA samples to industry alternatives (single-crystal sapphire) and (equiaxed alumina). Ablation tests revealed the benefit of polycrystalline alumina over sapphire. The benefit of lower isothermal sintering temperatures for reduced grain growth resulted in higher peak load before failure, resulting in greater characteristic strength and minimal transmission lost during a minute of oxyacetylene heat flux exposure. Finally, additional work was done on nanoceramic MgO-Y₂O₃, in a ceramic-processing method like that of PCA. These findings will also be discussed.</p>

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