This is how the U.S. Army
developed the first combat laser in the 1960s and 70s, but refused to deploy it
because it was considered too cruel. It all started with the Advanced
Propulsion Technology Branch of the Propulsion Directorate in the Army Missile
Command at Redstone Arsenal in the 1960's. Their mission was the development of
advanced propulsion concepts such as liquid monopropellants, bipropellants,
hybrids, air breathing etc. for application to Army missiles.
after a staff meeting with the Generals, Dr. Walter Wharton, our supervisor,
announced, "Men I've got a new and unusual project for you. It's not
propulsion, but needs all the technology and skills of propulsion. Here's the
pitch: Over the past two years, one of our Army contractors has failed to
demonstrate chemical lasing in a hardware device. The General asked us to take
over the effort. And, if we achieved a satisfactory demonstration of the
chemical laser we would be the nucleus of a new laboratory and weapons effort.
I told the General the problem was a natural fit to our skills. With the
chemists, physicists, engineers and technicians on our staff and our background
in hardware development and testing we could do the job expeditiously."
problem with using a laser as a weapon is power. A laser is focused light
energy, being sent from the laser to the target in a short burst. Using batteries
or generators and capacitors are too heavy for this to be practical. But the right
combination of chemicals can provide the needed energy, at least in theory. The
solution is a bit more complex.
led us in the analysis and evaluation of the contractor's effort and data.
Their device used gaseous hydrogen and gaseous fluorine. The attempt at lasing
was through the kinetic reaction states in the laser cavity to form the end
product HF. Dr. Wharton, a skilled chemist, immediately determined the critical
issue. To allow the intermediate activated molecules the time and space to lase
to ground states in the laser cavity, would require supersonic injection by the
mixing nozzles, and very low cavity pressure. That environment would slow down
the kinetics and stretch out the reaction zone allowing the species to lase.
designated me ( Joe Connaughton, a chemical engineer) as team leader for chemist Tony Duncan, laser device operator,
physicist Bill Friday, cavity optics and power, and mechanical engineer, Ben
Wilson facility design and development. We had top priority in obtaining
hardware, shop and other support services. In a matter of weeks we had the
device set up and ready for operation. The big day came when we were ready to
test. Dr. Wharton said, "Get that machine cranked up and don't stop till you
get it to lasing. I'll be in the office, so call me if you have any problems or
when it starts lasing."
most of the day adjusting the flow of the gases, and setting our liquid
nitrogen trap and pumping speed. But near the end of the day, Bill Friday held
a piece of strip recorder paper three feet from the cavity optics and yelled,
"Hey! Look guys at me burn holes in this paper by that invisible laser beam!"
We probably didn't project more than a hundred watts of power but it worked. We
had an operating HF chemical laser, and we were in business. The next day was
show time, which included all day demonstrations to various levels of management
including the Commanding General.
We were off
and running to build a ten kilowatt HF laser that would define the operating
parameters for scale up to weapon grade hardware. It was a large modular
boilerplate device designed for research studies. Calorimetric cavity mirrors
for precise power measurements and ports for optical flow field visualization
were included. The modular design allowed the evaluation and development of
laser components to advance the technology of high-energy lasers.
quickly expanded to include PhD level scientists, who began to study all
aspects of the chemical laser and extrapolate data to weapon system needs. Dr.
Barry Allen, with contractor support, researched solid sources for the
reactants. He found hydrides and fluorides that had reactant densities greater
than the cryogenics were appropriate. He also worked on the successful
development of chemical pumps that would replace the huge vacuum blow down
system required to pump the boilerplate laser.
Patterson and Miles Holloman were analyst who developed computer models that
helped guide the experiments. They also performed significant optical flow
visualization measurements that showed the deleterious effects of large
boundary layers in mixing nozzles and shock structures in the laser cavity
(refs. 2 & 3).
next decade we had fully characterized and optimized the chemical laser for
scale up to an army mobile weapon system. One major problem we were unable to
solve was getting lethal power onto a mobile vehicle. We were, however, able to
propose a mobile broad beam laser battlefield weapon that could destroy
battlefield and missile sensors. It would also burn out the eyeballs of enemy
presented our mobile battlefield laser concept (including supporting design
data) to several layers of army brass. He was surprised to learn that it was
turned down. The weapon was quite feasible, with a solid development schedule.
Amazingly, the generals turned it down on the basis that it was too cruel to
use in battle, because it would burn out foot soldiers eyes. Apparently, they
considered it to be in the same weapon class as poison gas.
of this initial decade or more of chemical laser effort by the Army is that the
program was cancelled and the unique laser laboratory and test facility
dismantled. The chemical laser group of specialists was disseminated into other
missile research and development units. At the time of the termination of the
chemical laser program, an Army Missile Command reduction in force also took
place. The Army downgraded many chemical laser specialists, because they were
no longer in the mainstream of the propulsion effort.
this early Army chemical lasers effort died at the time, the results were a
significant contribution to the Air Forces' airborne laser and fixed
installation lasers later developed by the armed services. -- Joseph