microwave spacecraft
Thales Alenia Space has proposed a radical way to launch small satellites on a beam of microwaves
Thales Alenia Space has proposed a radical way to launch small satellites on a beam of microwaves
Imagine taking a flight where the airliner jettisoned a batch of fuel tanks and possibly an engine or two; flights would be rather unnerving, and a lot more expensive! But this what we have to do to launch stuff into space. We don't need to do this with aeroplanes, both because they need much less energy, and because they can use the air to create lift, as a reactive mass to create thrust and to provide oxygen for the engines. Launch vehicles, however, are travelling to an environment where they must take all their oxygen and reactive mass with them.
Rocket engines are presently the only propulsion we have that can provide a big enough thrust, travel from sea level into vacuum and from a standstill to orbital velocity (at least 28,164 kilometres/17,500 miles per hour). But rockets are limited by the chemical energy that is available from their propellants. This is why launch vehicles are built in stages, so they can leave behind any tanks or engines as they are emptied.
The staging of rockets and the limitations of chemical propellants contribute to the difficulty and expense of accessing space. US- based SpaceX have built a rocket which can land vertically to return to base allowing multiple uses, while UK's Reaction Engines are hoping to create Skylon, a spaceplane using a Synergetic Air-Breathing Rocket Engine (SABRE), a hybrid jet engine and rocket, to take off and land like an aeroplane.
Recently, the UK arm of aerospace prime, Thales Alenia Space (TAS), have just completed a study, funded by the UK Space Agency’s National Space Technology Programme, of a radically different approach; the MicroLaunch Rectenna. Its aim: to launch small satellites from the ground via a microwave beamed propulsion system.
Chemical rocket engines work by releasing chemical energy via a combustion reaction between a fuel and oxygen, which also releases heat. This heat is transferred to the exhaust where the increase in pressure causes the hot gases to squirt out from the rocket nozzle as thrust. MicroLaunch TAS aims to break the link between these traditional sources of energy and reactive
mass, and ultimately keep the source of energy firmly grounded.
The MicroLaunch vehicle would look like the canopy of a wire-mesh umbrella, with a small bullet-shaped pod at the top. This metal canopy is the rectenna (rectifying antenna), that transforms microwave beam energy transmitted from a ground station into a direct electric current (that is the rectifying part).
This electricity can then be used to power an ingenious engine called a Hybrid Plasma Thruster (HPT). This electrically heats either neutral air or an on-board supply of nitrogen to use as a reactive mass. Rocket engines are theoretically more efficient at a higher temperature and because the HPT is not limited to a combustion temperature (verses chemical propellants) it can theoretically run hotter and produce more thrust per mass expelled. In addition, because its power source is a transmitter based on the ground, it can take off much more gently (such a vehicle could hover indefinitely in the atmosphere), reducing vibration and enabling the structure to be lighter.
The transmitter need only be a large, flat field of aerials – rather than some big dish – as a highly directional beam is used to transmit microwave power from the ground to the rectenna and track the MicroLaunch as it climbed and pitched over into orbit. These novel developments in the ever advancing world of space travel promises to meet the needs of post2025 space industry allowing us to continue exploring the mysteries of our universe.