Laser beam

“ Scientists are experimenting with a new kind of “lens”, one that uses variations in the density of gases to focus and guide the beam automatically. Since there are no surfaces in the path of the light beam, and since the gas is transparent and free of turbulence, the laser beam is not appreciably weakened or scattered as it travels through the pipe. ”

“ The earth shook and a great cloud of dust arose from the site, momentarily hiding the laser units. A light morning breeze drifted the dust downstream in a minute.
Ten huge holes gaped in the river bed underneath the laser beam heads mounted on adjustable cranes out and away from their power units.
"Fire," came the order again. This time there was nothing but the trembling of the earth as the beams cut a molten path through rock, clay, sand and boulders.
"Measure," the engineer ordered. A radar gauge bounced a beam off the bottom of one of the holes. ”

“ However, it is often asserted that machining the laser end mirrors to high accuracy may be a major roadblock to automated manufacture of lasing devices. Nazemetz (personal communication, 1980) has pointed out that a laser is accurate enough to surface a rough-hewn mirror to the accuracy required for its own construction. In a pinch, concave mirrors could be hewn from solid metal or basalt blanks simply by sweeping the laser beam radially across the disks, applying higher power nearer the center so more material volatizes there, thus creating a perfect spherical or parabolic surface gradient. ”

“ Laser beam machining is "especially adaptable and principally used for relatively small materials processing applications such as cutting, trimming, scribing, piercing, drilling, or other delicate material removal operations similar to milling or shaping" (Yankee, 1979) .
Dunning (unpublished Summer Study document, 1980) has suggested a variety of space and lunar applications for laser machining, including flash trimming of cast basalt parts; engraving bar codes on parts to enable quick and accurate recognition by robot vision systems; drilling holes in workpieces an inch thick or less ”

“ Is good to know they can't shoot us now, at least in a few minutes now, without getting themselves shot back. But they can shoot at Earth. Any ideas?"
"Well ... I thought some time ago that there was a little fallacy involved in that project when I saw how they hung the beam-director way out in front on those little old balloon-poles. They've got 'em bent, and if any one or two of 'em should happen to get punctured, the other two would move the mirror complete out of the laser beam focus. ”

“ The efficiency and power of weapons-grade tunable lasers now under development by Department of Defense contractors (Robinson and Klass, 1980) already are high enough to fulfill most cutting and sintering needs of the SMF. Heat dissipation is a substantial problem inherent in laser utilization for space manufacturing. Space-qualified heat exchangers must be developed for laser-beam machining to achieve its full potential as a viable macromachining space technology. In addition, industrial lasers must be designed to re-use the working gases. ”

“ It is easy to see how a starting kit might generate production equipment required for other space-compatible manufacturing techniques. (Shearing operations are assumed to be within the capabilities of starting kit laser beam units) . For example, laser techniques for scribing reverse threads onto hardened steel rolling dies is a foreseeable technology (fig. 4.17) . The availability of chromium on the Moon (0.6% by weight and higher in beneficiated iron grains) and lunar basalt for base plates makes thread rolling a valuable adjunct to the starting kit extrusion system. ”

“ On the other hand, the human mind under the discipline of Hemi-Sync acts after the fashion of a laser beam which produces a disciplined stream of light. The stream of energy is projected with total coherence of both frequency and amplitude such that the surface area of a laser beam contains billions of times the concentrated energy found in a similar surface area on the sun. Gateway assumes that once the frequency and amplitude of the human brain are rendered coherent, it is possible to begin accelerating both so that the human mind is soon resonating at ever higher vibrational levels. ”

“ R&D required - Further developments in electron-beam and laser technologies are likely to be highly fruitful. Laser flashlamp lifetimes must be greatly increased. Qualitative Tukey Ratio - The Ratio is somewhat poor for solid-state lasers using present-day technologies, though the components are not too massive and so could be lifted from Earth with only modest penalty. ”

“ In communication between distant space and earth, a light pipe might be a little cumbersome; hence it may prove necessary to set up an intermediate orbiting relay station that will, particularly in cases of poor weather, intercept the incoming laser beam and convert it to radio frequencies that can penetrate our atmosphere with greater reliability.
Powering space-borne lasers will, of course, be a problem. Indeed one of the major unsolved problems in production of spacecraft and long-term satellites is the provision of an adequate supply of power. ”

“ A possible solution is the use of “light pipes”, similar to the wave guides already in use for certain microwave applications over short distances. But as often happens, new developments create new needs; how, for example, can we get the laser beam to stay centered in the pipe and follow curves? ”

“ The next development to fire the imagination of scientists and engineers was the laser—an instrument that produces an enormously intense pencil-thin beam of light. Most of us have heard so much about this invention it seems hard to believe that the first one was built only a few years ago. We were told that the laser was going to have an even greater effect on our lives than the transistor. ”

“ High-frequency resistance and induction welding can also join a wide variety of materials, and with high efficiency. Table 4.29 compares key characteristics of laser and electron-beam processes with those of two less-promising alternatives for space and lunar applications. It is apparent that both E-beam and laser techniques are competitive in most categories whether on Earth or in space. Equipment cost of the E-beam should be much lower in a vacuum environment, since the major expense in terrestrial applications is for the maintenance of proper vacuum. ”

“ Since the beam of laser energy is narrow, it would be possible for the radiation to miss the earth altogether and be lost entirely unless the laser were pointed at the receiver with extreme precision. Aiming a gun at a target 50 yards away is one thing; aiming a laser from an unmanned spacecraft 100 million miles away is quite another. ”

“ The vehicle is single-stage-to-orbit."
"Nothing is burned." Vance had to admit it was a nifty idea. If you could do it.
“That's correct. The laser beam creates a shock wave, a burst of superheated gas moving at supersonic velocity out of the nozzle. By pulsing the beam, we form a detonation wave that hits the nozzle chamber and—"
"So it's really Star Wars in reverse," Vance interjected. "Bates is using all that fancy research in high-powered lasers to put up a satellite instead of shooting one down." ”

“ Television programs must compete for space on cross-country networks with telephone, telegraph, and transmission of data. The increasing use of computers in science, business, and industry will strain our facilities still further. Communication satellites will help, but they will not give us the whole answer; and much development work remains to be done on satellites.
Figure 2 Precision control of a machine tool by laser light.
Why the interest in the laser for communications? In a recent experiment all seven of the New York TV channels were transmitted over a single laser beam. ”

“ You are familiar with a watt and have an idea of its magnitude: think, for example, of a 15-watt or a 150-watt bulb. A watt is a unit of power; it is the rate at which (electrical) work is being done.
Figure 26 High power is demonstrated as a laser beam blasts through metal chain.
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The joule is a unit of energy and can be thought of as the total capacity to do work. One joule is equivalent to 1 watt-second, or 1 watt applied for 1 second. But it can also mean a 10-watt burst of laser light lasting 0.1 second, or a billion watts lasting a billionth of a second. ”

“ Careful co-ordination of the project by ground control was vital, so that no misalignment of the beam could possibly bring it to bear on any civilized portion of Earth's surface. For, fantastic as this Project Hot Rod might be as a source of power for Earth, Major Elbertson knew that it was also the most dangerous weapon that man had ever devised.
Therefore, the scientists were never alone in the control booth, despite the mile-long security records of each. Therefore, he and his men were in absolute control of the men who controlled the laser. ”

“ Mike turned back to the laser milling machine. "Now can we take the focusing lens off of this, and rig something to give me a focus at about 4.5 miles? Or would it need focusing at all? Shooting at that distance?"
"Depends on what you shoot, Mike. The unfocused beam can make a black surface very hot very quick. But from a mirror surface, it would just bounce, unless it's carefully focused."
"It ought to take care of the plastic at least, then."
"Go right through it. You gonna laser Hot Rod?"
"No. Just the anchor tubes that hold the mirror ”

“ Laser cutting speeds typically are as much as 30 times faster than friction sawing (Yankee, 1979) . Cutting accuracy is about 0.01 mm/cm under closely controlled conditions. All metals - including high-strength, exotic, and refractory alloys such as Inconel and titanium, as well as aluminum, stainless steel, and brass - and nonmetals such as diamond, ceramics, and plastics may be vaporized by laser beams. Hence, parts of these materials may be easily machined. Burr-free laser holes may be drilled as small as 10-100 μm. ”

“ When two laser beams touch, they produce an interference pattern of light and dark ripples that can be recorded on a photographic plate. And if one of the beams, instead of coming directly from the laser, is reflected first off an object such as a human face, the resulting pattern will be very complex indeed, but it can still be recorded. ”

“ Glasses and fibers - can be manufactured by using casting, grinding, and die-extrusion operations. Grinding is required for optical-quality glass shapes. Electron-beam and laser techniques are useful for final finishing of optical surfaces. Adhesives and coatings - of metals and ceramics can be applied by the starting kits or a specialized kit suited to the particular geometries of certain parts. ”

“ Lasers are helpful in facilitating annealing and oxidation processes and in trimming fine-tolerance capacitors and resistors. Electron beams have applications in silicon crystal purification and deposition of metals, though lasers also may be employed. Other uses for each beam type are readily imaginable. High-resolution automated control technologies must be developed for implantation, annealing, etching, and trimming processes in particular. ”

“ With proper auxiliary equipment, bursts of several billion watts have been achieved; but the burst lasts only about 100 millionths of a second. For certain uses, that’s just what is wanted: a highly concentrated burst of energy that does its work without giving the material being “shot” a chance to heat up and spread the energy, perhaps damaging adjacent areas.
Figure 27 Active substance for a modern liquid laser is made in an uncomplicated 10-minute procedure. Bluish powder of the rare earth, neodymium, is dissolved in a solution of selenium oxychloride and sealed in a glass tube. ”

“ Gas lasers are employed in continuous mode for nonmetal machining and in pulsed mode for metal machining. Since metallic substances are highly reflective at the CO2 wavelength a pulsed beam (10-9-10-6 sec bursts; Cross, personal communication, 1980) is needed to penetrate the surface and vaporize the metal (which causes a drop in reflectivity, and enhanced energy absorption) . ”

“ Sunlight focused onto the side of the laser (see Figure 32) provides the pumping power, enabling the device to put out 1 watt of continuous infrared radiation, enough for special space applications. Descendents of this device could produce visible light if this is deemed desirable.
Another approach, using chemical lasers, is even more intriguing and may have greater consequences. Chemical lasers will derive their energy from their internal chemistry rather than from the outside. A mixture of two chemicals may be all that is needed to initiate laser action aboard a spacecraft or satellite. ”

“ Figure 29 A miniature gas laser produces continuous output in visible red region.
The semiconductor laser is to solid and gas lasers what the transistor was to the vacuum tube; all the functions of the laser have been packed into a tiny semiconductor crystal. In this case, electrons and “holes” (vacancies in the crystal structure that act like positive charges) accomplish the job done by excited atoms in the other types. That is, when they are stimulated they fall from upper energy states to lower ones, and emit coherent radiation in the process. ”

“ Figure 20 shows the 2-mile-long “klystron gallery” that generates the power for kicking the high-energy particles down the tube. The gallery parallels the accelerator housing and lies 25 feet beneath it (Figure 21) . The large tube houses the optical alignment system and supports the smaller accelerator tube above. Target patterns dropped into the large tube at selected points produce an interference pattern at the far end of the tube similar to the one in Figure 13. Precise alignment of the tube is achieved by aiming the laser at the center dot of the pattern. ”