The ice gun is a very long tunnel cut through antarctic ice sheet and filled with hydrogen. There are three versions of the ice gun: nuclear, balloon, and chemical.
The nuclear version is a ramjet powered by nuclear reactor. The nuclear ramjet accelerates its cargo to about 9 km/s, drops it off, decelerates, stops, and picks up another cargo. The nuclear ramjet is simple and cheap, but it contaminates the tunnel with radioactive waste.
The balloon version accelerates the cargo with fast flowing hydrogen gas released by a multitude of unloaded balloon guns.
The rest of this file describes the chemical version of the ice gun.
The tunnel is divided into four compartments: breech, vacuum, middle, and muzzle. A barbell-shaped projectile is accelerated in the vacuum compartment by hydrogen stored in the breech compartment. The middle compartment is filled with hydrogen except for cavities which are filled with explosive mixture of hydrogen and oxygen. The projectile flying in the middle compartment ignites the mixture and generates thrust in a way similar to ramjet and two stage light gas gun. Having reached about 4 km/s, the projectile enters the muzzle compartment and generates thrust as a liquid rocket in tube or a solid rocket in tube. Hydrogen is difficult to transport, so it has to be produced on site, probably by wind-powered electrolysis.
To reduce the stress of acceleration force on the cargo, the tunnel is about 1000 km long and the cargo employs hydrogen injection during its flight through the atmosphere. There is no bibliography. The minimum mass (for 1-ton cargo) is only 100 tons not counting the ice.
The ice gun stands out due to its low cost (about 1% of chemical rocket launchers cost), and the ability to carry fragile cargo and people. Its only shortcoming is the reliance on the ice sheets which are melting due to global warming.
Ramjets have no thrust at takeoff, so the projectile has to be accelerated by pressure of hydrogen held in the breech compartment to about 1 km/s before it can generate thrust in ramjet mode. As the projectile gains speed inside the vacuum compartment, several valves (not shown) are opened to raise hydrogen pressure behind the projectile. Some hydrogen leaks into the evacuated tunnel in front of the projectile through the gap between the projectile and the tunnel. Helical grooves cut in the tunnel ensure uniform thickness of hydrogen cushion around the projectile and thus make good gas bearing. Upon reaching 1 km/s the projectile bursts through a thin plastic membrane separating the vacuum and middle compartments and generates thrust in ramjet mode.
The middle compartment is a gas gun. Among many viable options are ideas based on ramjet, ram accelerator, and vortex gun. Ramjet option has the advantage of simplicity, so it is preferable, at least in the short term. Its maximum velocity is about 5 km/s.
Breech and vacuum valves are closed as soon as the projectile enters the middle compartment. A few seconds before launch a mixture of oxygen and hydrogen is injected into cavities made in the middle compartment. The rest of the compartment is filled with hydrogen. When the projectile flies in the middle compartment, the mixture ignites and generates thrust in a way similar to ramjet and two stage light gas gun. The ice gun is superior to the ordinary ramjet because it does not carry its own fuel. It is very cheap, but cannot match performance of the two stage light gas gun because the projectile is accelerated by a mixture of hydrogen and steam rather than pure hydrogen.
Wet, frozen newsprint may be needed as reinforcement in the middle compartment if the gas pressure is high. The strength of plain ice is about 3.8 MPa for crushing, 1.4 MPa for bending, 0.9 MPa for tensile, and 0.7 MPa for shear. Frozen newsprint is one order of magnitude stronger.
The passage of the projectile vaporizes 1 millimeter thick layer of ice. As the vapor cools down, tiny ice crystals cover the middle compartment. Repeated vaporization distorts the tunnel, but each passage of the round projectile corrects tunnel shape.
Having reached about 4 km/s, the projectile enters the muzzle compartment. The aft part of the projectile generates thrust as a liquid rocket in tube or a solid rocket in tube. The projectile reaches about 9 km/s and leaves the ice gun. Hydrogen is injected from its nose cone into the adjacent atmosphere to reduce aerodynamic drag, noise, and temperature of the nose cone.
Tunnel excavation will consume large amount of energy. Fortunately, wind power is abundant on the coast of Antarctica and can be harnessed with the help of wind turbines. The wind energy is stored inside partially excavated tunnel in the form of air pressure. Air pressure outside the tunnel is about 58% of the pressure at sea level, so the elevated pressure inside the tunnel provides comfort for people working there.
Wind turbines and housing for the workers must be designed to withstand the harsh antarctic environment. Housing for the workers must be mobile, able to ride over crevasses, and resist hurricanes. The most powerful antarctic wind turbine is being build by german company Enercon. This gearless turbine will generate up to 300 kilowatts of electric power and will withstand winds up to 300 kilometers per hour.
It is not clear what is the best way to excavate the tunnel. The front runners are:
Gravity moves the antarctic ice sheet. At the South Pole the ice sheet flows at a rate of about 10 meters per year. A tunnel excavated perpendicularly to a fast flowing ice would soon be deformed so much that the cargo would experience excessive forces. To avoid this problem, the tunnel must be excavated in a nearly stagnant ice. Another potential problem is gradual collapse of the tunnel due to stress in the ice.
C. R. Bentley, "Ice Thickness and Physical Characteristics of the Antarctic Ice Sheet," Antarctic Map Folio Series, Folio 2, American Geographical Society, New York, 1964.
C. R. Bentley, "Subglacial Rock Surface Topography," Antarctic Map Folio Series, Folio 16, American Geographical Society, New York, 1972.
L. Crossley, Explore Antarctica, Cambridge University Press, Cambridge, 1995.
N. K. Vasiliev, "On development of fibre-ice-composites," Cold Regions Science and Technology, Vol. 21, No. 2, January 1993, pp. 195-199.