Abstract: A launching system is provided having a launch cylinder with an open bottom and propulsion means in the form of a rocket motor attached within the cylinder adjacent the top thereof. The cylinder is formed of a lightweight material which floats with a substantial portion thereof beneath the surface of the sea. The spacecraft is attached to the upper end of the cylinder in a vertical position for launching. Water cooling apparatus is provided for cooling the cylinder walls in proximity to the exhaust gases. On initial firing of the rocket motor, the hot exhaust gases from the rocket motor are confined therebelow and create expanding pressure within the cylinder in the space above the water surface, while generating steam, which also expands, thus lifting the cylinder and spacecraft from the water until approximately three-quarters of the cylinder is out of the sea. Thereafter, the engines of the spacecraft are ignited, while release of the craft from the cylinder is effected.