Electromagnetic launcher (EML) performance repeatability has been identified as a potential development issue for severa1 years. Investigation of this issue has been difficult since an EML that is powered on a relatively continuous basis to provide long duration operation has not been available. A battery charged capacitor power system has enabled long duration, six to seven seconds, EML experiments. This paper provides a summary of an experiment to investigate EML launch-to-launch performance consistency. A series of 8 ten shot bursts each separated by 15 to 30 minutes was performed in one day using a single set of bore materials. The experiment set-up is described, the experimental results discussed, and key parameters which could affect performance repeatability are identified,.

Public reporting burden for this collation of information is estimated to average I hour per response, including the time for reviewing Instructions, searching existing data sources. gatherng and maintaining the data needed, and completing and reviewing the collection of information. Send comments rerrding this burden estimat or any other apect of txis collcton of information, including suggestions for reducing this burden, A ABSTRACT (Maximum 200 words)As longer projectiles are accelerated, the efficiency (projectile' mass/launch mass) of the launch package decreases. The reduction in efficiency makes launching projectiles with a L/D (length-to-diameter ratio) greater than 20 undesirable.EN guns have several launch characteristics that differ from conventional guns. Higher launch velocities are achievable in EM guns because sonic gas velocities do not limit the projectile velocity. Acceleration profiles for EM guns are more constant.The acceleration forces can be distributed on the projectile easily because the accelerating force can be distributed with multiple armatures. These characteristics combine to make EM guns a very attractive approach for launching very long (i.e.. high L/D ratio) projectiles.Railgun launchers with multiple armatures can distribute the accelerating force. Each armature is supplied gun current for acceleration through its own set of rails. This multi-rail, multi-armature concept was tested at the railgum test facility. The results demonstrated feasibility.We were able to control current distribution to multiple armatures. This paper describes the theory and test results for multi-armature launch of high L/D projectiles.14. SUBJECT TERMS Ahwtraw-As longer projectiles are accelerated, the Sabots are used to transfer accelerating forces to the efficiency (projectile mass/launch mass) of the projectile during launch. As the launch package exits launch package decreases. IS. NUMBER OF PAGESThe reduction in the gun, the sabot separates from the projectile. The efficiency makes launching projectiles with a L/D sabot kinetic energy is wasted since it separates from (length-to-diameter ratio) greater than 20 the projectile at shot exit from the gun. Ideally, the undesirable.sabot mass should be zero to minimize this wasted EM guns have several launch characteristics energy. Longer, higher aspect ratio projectiles which differ from conventional guns. Higher require more sabot support to maintain acceptable launch velocities are achievable in EM guns projectile stresses. As projectile length increases the because sonic gas velocities do not limit the sabot size become so massive that a great deal of projectile velocity. Acceleration profiles for EM energy is wasted. It becomes inefficient to launch the guns are more constant. The acceleration forces package. Fig. I illustrates this point. The efficiency can be distributed on the projectile easily because of the launch package mass decreases with an the accelerating force can be distributed with increase in projectile L/D ratio. This reduction in ...

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