Abstract: A low orbit optical imaging satellite has a long thin satellite body housing an optical telescope arrangement. A major part of the telescope arrangement has its optical axis roughly parallel to the direction of elongation and includes a mirror arrangement deployed to direct a line of sight of the optical telescope out sideways from the direction of elongation. The transverse dimensions of the satellite body are preferably minimized to be close to the optical aperture dimension of the optical telescope, thereby providing a high ballistic coefficient and high orbit lifetime for orbits in the low thermosphere.

Abstract: A low orbit optical imaging satellite has a long thin satellite body housing an optical telescope arrangement. A major part of the telescope arrangement has its optical axis roughly parallel to the direction of elongation and includes a mirror arrangement deployed to direct a line of sight of the optical telescope out sideways from the direction of elongation. The transverse dimensions of the satellite body are preferably minimized to be close to the optical aperture dimension of the optical telescope, thereby providing a high ballistic coefficient and high orbit lifetime for orbits in the low thermosphere.

Abstract: A pulse combustor apparatus for burning solid fuel comprises a Rijke-type combustor tube and has a rotating fuel bed for defining a primary combustion zone adjacent the fuel bed. The rotating fuel bed tends to minimize agglomeration of solid fuel and accumulation of ash during combustion by agitating the solid fuel. An inlet conduit is provided for introducing a low nitrogen gaseous fuel to the combustion air upstream of the combustion zone to minimize the formation of NO.sub.x in the primary combustion zone. In other embodiments, inlets are provided downstream of the primary combustion zone for introducing additional air or gaseous, low nitrogen fuel for air staging or reburning to minimize the emission of NO.sub.x. Sorbents, such as limestone, are introduced above the bed to minimize SO.sub.2 emissions.

Abstract: A pulse combustor apparatus including a combustor tube having open ends and containing at least one combustion zone where combustion of a fuel occurs and heat is released, resulting in the formation of a standing acoustic mode with nodes and anti-nodes in the tube. The combustion zone is located approximately half the distance between the acoustic pressure node and anti-node where the acoustic pressure oscillation lags the acoustic velocity oscillation by approximately one-quarter wavelength of the oscillation. Furthermore, the combustion air must flow towards the acoustic pressure anti-node. The fundamental principle relating to the occurrence of the pulsations in the combustor is the interaction between the combustion processes and both the non-zero acoustic velocity and acoustic pressure oscillations at the designated combustion zone location.