Fundamental and Applicational Investigation of Ram Accelerator

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A ram accelerator system has been developed. The test section has a 25 mm bore and a 6m length. Its preaccelerator, a powder gun, is capable of launching a 40-gram payload to 1.2km/s with smokeless powder of 30 grams. The mixture supply system, composed of mass flow controllers and backpressure regulators, is easy to handle and utilizes cylinder pases up to a pressure about 1MPa higher than the fill pressure. Projectile velocity is measured by sensing magnetic induction using home made pick-up coils. The multiplexer system is capable of recording pressure data at plural points in one channel.Sixty ram acceleration experiments were made with methane-oxygen-nitrogen (or argon) mixtures. Sabot separation was made only by unsteady gas dynamics made in the mixture. Starting condition for ram acceleration strongly depended on non-dimensional heat release, entry speed and sabot design.A numerical code which can calculate the thrust performance based on the existing ram accelerator Hugoniot theory has been developed. Moreover, the theory was extended by taking finite-rate chemistry into account. With the extended theory, performances not only of the thermally choked mode but also of the transdetonative mode can be analyzed.It is important through this research project to show that ram acceleration is possible with this small bore apparatus, thereby enhancing understandings of scaling effects of ram accellerators. This technology is promising in being applied to space technology, material technology etc. in Japan.