Beamed Energy Propulsion: an Introduction
Beamed Energy Propulsion (BEP) is a rocket science, but you dont have to be a rocket scientist to grasp the concept. Because it is simple as any ingenious ideas are. In the next four paragraphs and in simple layman terms I will explain it to you.
It is all about rockets. What everyone knows about them? On Earth motion is based on pushing from the medium, wherever the motion takes places: cars pushing from pavement by wheels, swimmers pushing from water by limbs, etc. Rockets fly in space and space is mostly a vacuum, it is empty. Rockets move in space using reactive principle, i.e. exhausting hot gases (backward) and pushing away from exhaust in opposite direction (forward). Rockets have to carry all their fuel and burning agent onboard, because there is nothing in space that can be used for burning fuel (like air for burning gasoline in automobiles on earth).
Rockets cargo space is very expensive. Why? Because with so many elements onboard: fuel, oxidizer, cryogenics, tanks, lines, you name it, there is a small (and very expensive room) for the payload. If we could only find a way to separate the heavy energy source from the rocket, the gain in efficiency of such rocket will be tremendous.
This can be done if instead of carrying energy source onboard, we will beam that energy from a remote power station. What kind of beam it can be? Laser beam, microwave beam, even x-ray, in all cases energy will be delivered to the rocket with speed of light. When a great number of photons is focused (even loosely) on a solid matter, such matter is evaporated and ionized almost instantaneously, i.e. the release of energy is much higher than one used from burning hydrogen. So, laser-driven vehicle will be still flying on the same rocket principle (pushing away from its exhaust), but exhaust energy and structural lightness will be incomparably superior to hydrogen-burning rockets.
Payload, Propellant, Photons, Period! ” 4P Principle introduced by Arthur Kantrowitz, the founder of modern laser propulsion, is an essence of BEP. Laser-driven rockets will consist of lightweight focusing optics (mirrors), modest amount of solid ablative propellant and the rest: the rest will be payload! No more fuel, cryogenics, tanks, oxygen, combustion chambers, etc.
How much beamed energy is more efficient than traditional hydrogen burning? About hundred times! Currently, for reasons disclosed above we are paying $10,000 per pound of payload delivered from ground to low earth orbit only. If space launches will be done with high-power lasers, the price per pound of payload will fall to $100! This is 100-fold gain!
The most developed today branch of BEP is called laser propulsion, it is based on energy transfer with high-power laser beams. The next in development is microwave propulsion, followed by barely explored BEP with x-rays and particles. The number of in-lab demonstrations of BEP grows every year, and the time of actual demonstration of beam-driven space rocket is getting closer. No question, there is still a lot of work ahead on development of BEP systems, but one thing is clear, they have a great future.
