A space gun, sometimes called a Verne gun because of its appearance in From the Earth to the Moon by Jules Verne, is a method of launching an object into space using a large gun- or cannon-like structure. Space guns could thus potentially provide a method of non-rocket spacelaunch. It has been conjectured that space guns could place satellites into Earth's orbit (although after-launch propulsion of the satellite would be necessary to achieve a stable orbit), and could also launch spacecraft beyond Earth's gravitational pull and into other parts of the Solar System by exceeding Earth's escape velocity of about 11.20km/s (40,320km/h; 25,050mph). However, these speeds are too far into the hypersonic range for most practical propulsion systems and also would cause most objects to burn up due to aerodynamic heating or be torn apart by aerodynamic drag.
Therefore, a more likely future use of space guns would be to launch objects into Low Earth orbit, at which point attached rockets could be fired or the objects could be "collected" by maneuverable orbiting satellites.[citation needed]
In Project HARP, a 1960s joint United States and Canada defence project, a U.S. Navy410mm (16in) 100 caliber gun was used to fire a 180kg (400lb) projectile at 3,600m/s (12,960km/h; 8,050mph), reaching an apogee of 180km (110mi), hence performing a suborbital spaceflight. However, a space gun has never been successfully used to launch an object into orbit or out of Earth's gravitational pull.
Technical issues
The large g-force likely to be experienced by a ballistic projectile launched in this manner would mean that a space gun would be incapable of safely launching humans or delicate instruments, rather being restricted to freight, fuel or ruggedized satellites.
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 parabolic orbit, a hyperbolic orbit, or part of an elliptic orbit which ends at the planet's surface at the point of launch or another point. This means that an uncorrected ballistic payload will always strike the planet within its first orbit unless the velocity was so high as to reach or exceed escape velocity. As a result, all payloads intended to reach a closed orbit need at least to perform some sort of course correction to create another orbit that does not intersect the planet's surface.
A rocket can be used for additional boost, as planned in both Project HARP and the Quicklaunch project. The magnitude of such correction may be small; for instance, the StarTram Generation 1 reference design involves a total of 0.6km/s (1,300mph) of rocket burn to raise perigee well above the atmosphere when entering an 8km/s (18,000mph)low Earth orbit.[1]
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 (), and the needed velocity (), the acceleration () is provided by the following formula:[citation needed]
For instance, with a space gun with a vertical "gun barrel" through both the Earth's crust and the troposphere, totalling ~60km (37 miles) of length (), and a velocity () enough to escape the Earth's gravity (escape velocity, which is 11.2km/s or 25,000mph on Earth), the acceleration () would theoretically be more than 1,000m/s2 (3,300ft/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 V-3 cannon program, during World War II was an attempt to build something approaching a space gun. Based in the Pas-de-Calais area of France it was planned to be more devastating than the other Nazi 'Vengeance weapons'. The cannon was capable of launching 140kg (310lb), 15cm (5.9in) diameter shells over a distance of 88km (55mi). It was destroyed by RAF bombing using Tallboyblockbuster bombs in July 1944.[6]
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 John Hunter founded the Jules Verne Launcher Company in 1996 and the Quicklaunch company. As of September 2012, Quicklaunch was seeking to raise $500 million to build a gun that could refuel a propellant depot or send bulk materials into space.[8][9][10]
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]
The 1992 video game Steel Empire, a shoot 'em up with steampunk aesthetics, features a space gun in its seventh level that is used by the main villain General Styron to launch himself to the Moon.
In the 2004 role-playing game Paper Mario: The Thousand-Year Door, a village of Bob-ombs operates a space gun to send Paper Mario and company to the X-Naut's base on the Moon.
Gerald Bull and Project Babylon are integral to the plot of Louise Penny's 2015 novel The Nature of the Beast.
Clarke, Victor C. Jr. (1970-04-10), An Essay On the Application and Principle of Gravity-Assist Trajectories For Space Flight(PDF), Jet Propulsion Laboratory, California Institute of Technology, p.7, archived from the original(PDF) on 2016-04-18, retrieved 2013-08-13, By induction then, it is obvious that the process of diverting a spacecraft from one planet to another might be continued indefinitely, if the planets were in favorable positions.
"David Purley Bio". Anton Sukup's Autographs of F1 Drivers. Retrieved July 31, 2006. Purley was subjected to the highest G-forces ever survived by a human being - 179.8G - when the car went from 108mph to zero in just over half a meter
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