Long before the first test flights of the V-2, the Paris Gun of World War I set impressive altitude and speed records for artificial objects. In the 1950s, as the rocket became established as the primary means of reaching space, Canadian engineer Gerald Bull began a lifelong struggle to use guns for cheap access to the high atmosphere and Earth orbit. His Project HARP (High Altitude Research project) in the 1960s showed that a suborbital cannon can be cost-effective for studying the upper atmosphere, between 50 km and 130km, and has the potential to launch vast numbers of satellites each year in all kinds of weather. A further development of this concept was Lawrence Livermore Lab's Project SHARP (Super High Altitude Research project).
Even if shot out of an extremely powerful cannon, a projectile would need to include a rocket in order to enter a stable orbit. This is for two reasons. First, reaching orbital velocity (with an extra margin for air resistance) is difficult using a cannon alone. Second, by Kepler's first law, any orbit is an ellipse with one focus at the Earth' s center. If the payload is launched from a point A on the Earth' s surface, its orbit necessarily would intersect the surface again at a symmetrically placed point B. An orbital adjustment is therefore essential.
Plans also exist for accelerating a payload by magnetic forces on a "rail gun" consisting of parallel conductors, into which a very large electric current is directed. The same problems apply here, plus the added one of storing and then suddenly releasing a great amount of electrical energy. This kind of technology might be appropriate for future use on the Moon but is at an even earlier stage than the space cannon.
Related category BALLISTICS
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