Beneath this, separated by a valve, is a chamber filled with compressed air. Opening a vent equalizes the pressure above and below the valve, allowing it to be released. The chamber is open-bottomed so water rushes in from below and discharges up the barrel. The rising volume of water provides a constant force and pressure onto the compressed air, which propels the shuttle capsule, explains Taylor. The air expands rapidly as it tries to equalize with atmospheric pressure, which pushes the rocket ahead of it.
Water rushing up the barrel increases the thrust.
The final exit speed at the mouth of the barrel depends upon the diameter and length. The force of the air, says Taylor, would enable the vehicle to exit the barrel at speeds in excess of 1000 kilometers in an hour. But Barry Moss, a space launch expert at Cranfield University has his doubts, according to New Scientist. When factors like friction and air resistance are taken into account, he doesn't believe there will be enough thrust. Taylor says that although the speed is nowhere near the 29,000 kilometers per hour escape velocity required, it does mean that the craft would be traveling at immense speeds when it reaches sea level, at which point the on board rockets are fired.