This short note proposes a concept of two stage accelerator which can attain more than 4 km/s with fairly high acceleration level under the condition of tolerable heat damage of accelerator tube. Here the electro-magnetically pre-accelerated projectile with a charge by a composite armature is further accelerated by the pressure and the jet thrust of the ignited charge. The ignition of travelling charge is performed by the ohmical explosion of a metallic filament in the composite armature at a pre-determined moment. A possiblity of this ignition is discussed briefly with a result from a basic experiment.
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