Arthur Kantrowitz passed away on November 29, 2008 in New York City. He was 95 years old. A founder of Avco Everett Research Laboratories, inventor of ablative rocket nose cones (reentry protection), champion of Science Court and professor of Dartmouth College, Kantrowitz will be always remembered as a forefront figure of American scientific community of 20th century. However, in this brief note I would like to say few words about one of his greatest contributions to mankind: his key role in development of laser propulsion.



Laser Propulsion is a part of rocket science, but dont be discouraged by a silly tag: the idea is simple. We pay on average $10,000 per every pound of payload delivered to low earth orbit. Why that much? Because, we use very inefficient carriers: chemical rockets. These hydrogen gluttons have to carry everything onboard: fuel, oxidizer, cryogenics, tanks, lines, you name it, leaving a small (and very expensive room) for the payload. If we could only find a way to separate the energy source from the vehicle, deliver that energy to the vehicle from some power station, the gain in efficiency of such vehicle will be tremendous.

The energy can be delivered with powerful laser beams! Believe it or not, the original idea was published in 1924 by Konstantin Tsiolkovsky, the space scientist and great visionary, who preceded his own times for at least on half-century. Tsiolkovsky pointed out that energy can be delivered to a space rocket by means of tight light beams (laser was invented 35 years later). The idea of light-beaming energy to a rocket that could be just a dream in 1924, was refined, formulated and delivered by Arthur Kantrowitz as a precise scientific concept of laser propuslion.

In 1972 Kantrowitz published a paper Propulsion to orbit by ground based lasers, with a genius idea: to launch light satellites right from the ground to space with high-power laser beams. In this the vehicle will be just straddling the tip of the beam. When laser beam is focused on a solid surface, it has enough power to vaporize and ionize almost anything with energy release much higher than hydrogen burning, used in modern space rockets. So, comparing to chemical rockets, laser propulsion uses the same rocket principle, excepting much more energetic exhaust and much lighter vehicle structure: no tanks, fuel lines, etc. leaving a lot of room for a payload.

Driven by laser rocket will be composed of very light focusing mirrors, relatively small (energy efficient) solid propellant and, voila: the rest will be payload! Forget heavy liquefied gases (oxygen and hydrogen), cryogenics, fuel tanks and lines, combustion chambers, etc.: Payload, Propellant and Photons, Period! Arthur Kantrowitz called it 4P Rule. Bottom line: scientifically sound calculations have shown that the price of one pound of a payload delivered to low earth orbit will be drop to $100. Laser propulsion offers 100-fold, revolutionary savings on space deliveries.

The original paper of Kantrowitz was like a first milestone at the beginning of a long way, a scientific quest for beamed-energy propulsion. Kantrowitz not mere wrote a fundamental paper, he started the first in the world research program on laser propulsion at Avco Everett Research Labs. Decade later new research projects followed the cause and two decades later first laser-driven vehicles were launched into air (but not to space yet). New countries: Russia, Japan, Germany, China opened their own research programs and hundreds of researchers joined the field. New forms for beamed-energy propulsion were found, such as microwave propulsion. Hundreds of people work on this field today, the work is in progress, there is still a lot to do. Remarkably, this field was opened by one man, Arthur Kantrowitz, and he will be always remembered for that.