快猫短视频

SPACEPLANES may one day lift off from the backs of huge seaplanes that skim
the ocean鈥檚 surface at half the speed of sound, say space scientists in Russia
and Japan.

The developers believe that the technology could be highly competitive with
traditional vertical take-off systems such as the space shuttle. The plan is to
mount a spaceplane on the back of a 1500-tonne, rocket-propelled seaplane, known
in Russia as an 鈥渆kranoplan鈥�.

Flying just a few metres above the water, the ekranoplan rides along on the
cushion of air that forms under large flat objects near a surface, the 鈥渨ing in
ground鈥� (WIG) effect. Powered by jet engines, the ekranoplan reaches speeds of
over 600 kilometres per hour (Mach 0.5) at which point the spaceplane鈥檚 rockets
fire and the two vehicles separate. The spaceplane continues to climb until it
reaches its escape velocity of around 966 kilometres per hour.

The chief advantage of the system, says Alexander Nebylov, director of the
International Institute for Advanced Aerospace Technology in St Petersburg, is
the high initial launch speed. With vertical take-off, most of the fuel in
the space shuttles鈥� boosters is spent lifting more fuel. But with a horizontal
launch, the spaceplane gains low-cost aerodynamic lift from the forward velocity
of the ekranoplan. The spaceplane has to carry slightly more fuel than if it was
taking off vertically, but the ekranoplan will use less fuel than a rocket
engine.

Because the launch will effectively be a single-stage affair, no massive
external fuel tank or pair of solid rocket boosters, as used on NASA鈥檚 space
shuttle, is required. Furthermore, WIG craft have high fuel efficiencies due to
low drag.

But if take-off sounds bizarre, consider the landing. Nebylov says the
spaceplane will dock with a moving ekranoplan when it returns to Earth. The lack
of landing gear will help balance out the extra fuel, he says.

Nebylov, together with Nobuyuki Tomita of the Musashi Institute of Technology
in Tokyo, plans to undertake some initial sea trials next year with a
scaled-down ekranoplan, weighing a mere 400 tonnes.

鈥淲e can launch from any point in the ocean, which is very important in
achieving a necessary orbit,鈥� Nebylov says. Rocket scientists like to launch as
near as they can to the equator, as the Earth鈥檚 extra rotational velocity there
helps spacecraft into orbit.

Jay Jayawant, who is working on a horizontal spacecraft take-off system using
magnetic levitation at the University of Sussex, has his reservations. 鈥淣othing
travels at these speeds without having serious problems with stability,鈥� he
warns.

But Nebylov says its size is the key to its stability. To work, the
ekranoplan has to be three times larger than the Caspian Sea Monster
鈥攁n enormous military ekranoplan built during the Cold War. 鈥淚t
must also be rather big to have good seafaring abilities,鈥� says Nebylov. A
larger craft will make a more stable platform that is capable of reaching
take-off speeds even with waves 5 metres high, he says.