Electric aircraft power plants and associated methods are provided. One power plant includes an emergency power unit (EPU) for providing electric power in the event of a malfunction of a battery pack of an electric aircraft to permit the electric aircraft to make an emergency maneuver. The EPU includes a rocket engine for generating a stream of exhaust fluid using a rocket propellant, a turbine operatively connected to extract energy from the stream of exhaust fluid generated by the rocket engine, and an electric generator operatively connected to be driven by the turbine and to supply electric power to an electric motor propelling the electric aircraft.

A photonic reflector device includes a first layer, a second layer, and a third layer. The first layer, which functions as a retro-reflector, is formed of a first material contacting a second material and having a non-planar interface therebetween. The second layer, which functions as a photonic crystal, includes third and fourth materials that have different refractive indices from one another and are configured such that the second layer has a periodic optical potential along at least one dimension. The third layer, which functions as a Lambertian scatterer, includes a plurality of inclusions in a first matrix material. In combination, the layers may be optimized to synergistically reflect targeted wavelengths and/or polarizations of light.

A photonic reflector device includes a first layer, a second layer, and a third layer. The first layer, which functions as a retro-reflector, is formed of a first material contacting a second material and having a non-planar interface therebetween. The second layer, which functions as a photonic crystal, includes third and fourth materials that have different refractive indices from one another and are configured such that the second layer has a periodic optical potential along at least one dimension. The third layer, which functions as a Lambertian scatterer, includes a plurality of inclusions in a first matrix material. In combination, the layers may be optimized to synergistically reflect targeted wavelengths and/or polarizations of light.

A method of reprocessing a metal product includes a welding step for welding a dummy member to the metal product, a reprocessing step for reprocessing the metal product in a state where the metal product is supported by a first support unit and the dummy member is supported by a second support unit, and a removal step for removing the dummy member from the metal product after the reprocessing step. The reprocessing of the metal product while the metal product is fixed is thus enabled without restriction from the shape of the metal product.

A preceramic resin formulation comprising a polycarbosilane preceramic polymer and an organically modified silicon dioxide preceramic polymer. A ceramic material comprising a reaction product of the polycarbosilane preceramic polymer and organically modified silicon dioxide preceramic polymer is also described. Articles comprising the ceramic material are also described, as are methods of forming the preceramic resin formulation and the ceramic material.

A preceramic resin formulation comprising a polycarbosilane preceramic polymer and an organically modified silicon dioxide preceramic polymer. A ceramic material comprising a reaction product of the polycarbosilane preceramic polymer and organically modified silicon dioxide preceramic polymer is also described. Articles comprising the ceramic material are also described, as are methods of forming the preceramic resin formulation and the ceramic material.

A heat exchanger which may be used in an engine, such as a vehicle engine for an aircraft or orbital launch vehicle. is provided. The heat exchanger may be configured as generally drum-shaped with a multitude of spiral sections, each containing numerous small diameter tubes. The spiral sections may spiral inside one another. The heat exchanger may include a support structure with a plurality of mutually axially spaced hoop supports, and may incorporate an intermediate header. The heat exchanger may incorporate recycling of methanol or other antifreeze used to prevent blocking of the heat exchanger due to frost or ice formation.

A device for mounting a load to a carrier is described. The device includes a first support configured for fixation to the carrier; a second support configured for fixation to the load. The first and second supports are spaced away from each other viewed along a main load bearing axis of the device. The device further includes an outer shell extending along the main load bearing axis, and an inner member that is within the outer shell. The device includes a damping material connecting the inner member to at least the outer shell, wherein one of the outer shell and the inner member connects the first support and the second support to each other.

Passive reactivity control technologies that enable reactivity control of a nuclear thermal propulsion (NTP) system with little to no active mechanical movement of circumferential control drums. By minimizing or eliminating the need for mechanical movement of the circumferential control drums during an NTP burn, the reactivity control technologies simplify controlling an NTP reactor and increase the overall performance of the NTP system. The reactivity control technologies mitigate and counteract the effects of xenon, the dominant fission product contributing to reactivity transients. Examples of reactivity control technologies include, employing burnable neutron poisons, tuning hydrogen pressure, adjusting wait time between burn cycles or merging burn cycles, and enhancement of temperature feedback mechanisms. The reactivity control technologies are applicable to low-enriched uranium NTP systems, including graphite composite fueled and tungsten ceramic and metal matrix (CERMET), or any moderated NTP system, such as highly-enriched uranium graphite composite NTP systems.

A networked electronic ordnance system is provided. The system includes a first plurality of pyrotechnic devices connected to a first network bus. The system further includes a first bus controller connected to the first network bus. The system further includes a second plurality of pyrotechnic devices connected to a second network bus. The system further includes a second bus controller connected to the second network bus. The system further includes a bus interface circuit connected to the first bus controller by a first electrical connection and connected to the second bus controller by a second electrical connection.