Space gun

In

Technical issues

The large

Getting to orbit

A space gun by itself is not capable of placing objects into a stable orbit around the object (planet or otherwise) they are launched from. The orbit is a

In a three-body or larger system, a gravity assist trajectory might be available such that a carefully aimed escape velocity projectile would have its trajectory modified by the gravitational fields of other bodies in the system such that the projectile would eventually return to orbit the initial planet using only the launch delta-v.^[2][3]

Isaac Newton avoided this objection in his thought experiment by placing his notional cannon atop a tall mountain and positing negligible air resistance. If in a stable orbit, the projectile would circle the planet and return to the altitude of launch after one orbit (see Newton's cannonball).^[4]

Acceleration

For a space gun with a gun barrel of length (${\displaystyle l}$), and the needed velocity (${\displaystyle v_{e}}$), the acceleration (${\displaystyle a}$) is provided by the following formula:^{[citation needed]}

${\displaystyle a={\frac {v_{e}^{2}}{2l}}}$

For instance, with a space gun with a vertical "gun barrel" through both the Earth's crust and the troposphere, totalling ~60 km (37 miles) of length (${\displaystyle l}$), and a velocity (${\displaystyle v_{e}}$) enough to escape the Earth's gravity (escape velocity, which is 11.2 km/s or 25,000 mph on Earth), the acceleration (${\displaystyle a}$) would theoretically be more than 1,000 m/s² (3,300 ft/s²), which is more than 100 g-forces, which is about 3 times the human tolerance to g-forces of maximum 20 to 35 g^[5] during the ~10 seconds such a firing would take.This calculation does not take into account the decreasing escape velocity at higher altitudes.

Practical attempts

V3 Cannon (1944-45)

The German

The most prominent recent attempt to make a space gun was artillery engineer Gerald Bull's Project Babylon, which was also known as the 'Iraqi supergun' by the media. During Project Babylon, Bull used his experience from Project HARP to build a massive cannon for Saddam Hussein, leader of Ba'athist Iraq. Bull was assassinated before the project was completed.^[7]

Quicklaunch (1996-2016)

After cancellation of SHARP, lead developer

Ram accelerators have also been proposed as an alternative to light-gas guns. Other proposals use electromagnetic techniques for accelerating the payload, such as coilguns and railguns.^{[citation needed]}

In fiction

The first publication of the concept may be