Beamed Energy Propulsion (BEP) in simple words.

"Payload, Propellant, and Photons, ... Period!", Arthur Kantrowitz

What is Beamed Energy Propulsion (BEP) and why should we devote our time and effort to study it?

Beamed Energy Propulsion (BEP) belongs to "rocket science", but you don’t have to be a rocket scientist to grasp the concept, because it is as simple as any ingenious idea. In the next paragraphs I will explain it to you in simple layman’s terms.

Rocket science is of course about rockets. So what makes rockets different from all other means of transportation? Motion on Earth is based on pushing the moving body using feet, wheels, tentacles, etc., against the environment where the motion takes place. For example, we push our feet against the ground when we walk, cars use wheels to push against the pavement, a fish uses fins to push against water and so do propeller blades moving a ship. In order to move, you always have to push against something. It is a problem in space, because space is empty - there is nothing there to push against. So, in order to fly in space every rocket has to use the reaction principle, i.e., burn fuel, form exhaust gases and push that exhaust out the rocket, which pushes the rocket in the opposite direction. Have you ever held a firehose or high pressure water hose and felt the hose push back on you as it squirts the water out? The more gallons per minute, the more the force back on you. It’s the same principle for rockets. Space rockets are the only manmade vehicles that push away from their own exhaust and move that way.

There is no oxygen in space, so if you need to burn something in space, you have to carry the oxidizer as well as the fuel onboard. So, rockets have to carry onboard their fuel (hydrogen), burning agent (oxygen) and everything else that is needed to burn hydrogen and maintain motion in the desired direction (tanks, cryogenics, combustion chamber, fuel lines etc.). This is a heavy burden, and it brings a big downside: the price of cargo gets enormously high. For example, in order to deliver one pound of payload to LEO (Low Earth Orbit, which starts at 100 miles altitude and goes up to 1,240 miles) we have to pay $10,000. At the same time, the cost of the energy needed to lift one pound to LEO is just $30.00. So, why do we have to pay $10,000 and not $30? It’s because of the inefficiency coming from the need to carry fuel and everything else onboard, leaving so little space for useful payload. If we could separately provide the propulsive energy for a rocket, we would be rewarded with a gigantic increase in efficiency!

The only way of doing this is to beam the energy to the rocket from an external source using high-power laser, x-ray or microwave beams. With special mirrors, the rocket will collect and focus those beams on the fuel. Any solid matter can be a fuel, so it’s important to find the best fuel. When a high-power beam of photons is tightly focused on a solid material, the material evaporates and ionizes instantly. The energy density in such a focus is hundreds to millions of times higher than that released by burning hydrogen. Thus, a beam-driven rocket will remain a rocket, it will be pushing from its own exhaust, but the energy of this exhaust is much higher. Returning to the firehose analogy, if the speed of the squirting water is much higher, fewer gallons per minute will make the same force. Because of this, a BEP rocket is much lighter, not having to carry as much fuel to do the same job compared to a hydrogen-burning rocket. Therefore it will have more room for cargo and deliver it to LEO more efficiently.

Payload, Propellant, Photons, Period! – this is the “4P Principle” introduced by Arthur Kantrowitz, the founder of laser propulsion. 4P is the essence of BEP (this is, by the way, why you can see 4P is in the center of our logo). Laser-driven rockets will consist of lightweight focusing mirrors, a modest amount of solid ablative propellant and the rest will be payload! No more heavy fuel, cryogenics, tanks, oxygen, combustion chambers, etc..

Can the efficiency of a beam-driven rocket be compared to that of a hydrogen burner? Yes, this can be done with scientific precision. Calculations (repeated many times by independent researchers worldwide) show that with the laser propulsion the LEO delivery price will be reduced from the current $10,000 to $100 per pound of a payload.

This is a revolutionary hundredfold gain! The effect of such a change will be that the cost of putting a person in orbit goes from 2 million dollars to 20 thousand, and, with further reductions from perfecting the technology over time, you may buy a ticket to LEO in your lifetime! Unlike with airlines, once you’re up there, you don’t have to come down for a while!

Laser propulsion, i.e. use of high-power lasers for terrestrial space launches and in-space transportation is the most developed branch of BEP today. Various types of laser-propelled flights have been already demonstrated in the field by the U.S. and Russia, and by many research groups in the lab (U.S., Russia, Germany, Japan, and China).

Microwave propulsion is another relatively well explored part of BEP. Much less is known about the potential of x-rays and particle beams for BEP. Of course, a rapidly diverging particle beam does not sound right for open space, but think what can be done if such a beam is sustained and confined within a spaceborne accelerator tube. BEP on spaceborne platforms opens numerous opportunities and applications for new technologies, including some with a very limited application on Earth.

Beamed-energy propulsion can be used not only for space transportation, but also for aeronautics - some models of experimental beam-riding aircraft (helicopters, dirigibles) have already been built and flown. Moreover, BEP and its unique capabilities can be applied to the motion of nano-vehicles in microspace. Imagine microsurgery done by a nano-robot driven by BEP inside human arteries. I call it micronautics. The science and engineering of all the incredible applications of BEP are discussed at the meetings of the International Symposium of Beamed Energy Propulsion.

Overall, beamed-energy propulsion remains a field of future technology, and there is still a lot of work ahead on development of BEP systems, but one thing is clear - they have a great future and the days when we will start using beamed-energy propulsion for our transportation and industrial needs are near.

written and posted by Andrew V. Pakhomov

updated and revised by Claude R. Phipps

If you would like to know more about BEP:

You can view slides of Introductory lecture on Laser Propulsion by A.V. Pakhomov.

Read Wikipedia about BEP.

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