Total manpower, of course, is much more than that: there are probably 700,000 engineers and industrially oriented scientists in the United States today, as against 2,000 even as late as Edison's first high voltage light bulb. Whereas Edison worked with 20 to 100 scientists in his laboratory, and Fulton labored alone, there are 5,000 industrial laboratories today employing from 20 to 7,300 technical men each.[30]
New power sources
One of the greatest demands of spacecraft of the future will be for new sources of power. While rocket propulsion power is part of this picture, the power needed to operate space vehicles after launching may prove to be the larger and more important need. Progress has already been made in this direction by use of special kinds of batteries and solar cells which convert the sun's rays into electric current. But these will need supplementing or replacing eventually as greater power becomes necessary.
It would be rash to predict the outcome of this complicated field, but certain very promising methods can be listed.
One is the fuel cell, which converts fuel directly into electric power without the necessity for machinery or working parts. Much progress has been made on the fuel cell in recent months. In England a 40-cell unit has been used to drive a forklift truck and to do electric welding. It develops up to 5 kilowatts.[31] In the United States a 30-cell portable powerplant developing 200 watts has been delivered to the Army and Marine Corps,[32] while a 1,000-unit cell has been developed in the Midwest which provides 15 kilowatts and drives a tractor.[33]
Another method is plasma power, or power generated through the use of hot ionized gas. Such gas acts as a conductor of electricity and when employed as a "magnetohydrodynamics" generator it can be used for a variety of purposes. It has the advantage of being simple, rugged, and efficient. Some day it may also prove very economical. Already 10 municipal areas along the Mason-Dixon line are preparing to experiment with electric power derived from this source.[34] It has been estimated that "as much as 1 million watts could be generated by shooting a stream of plasma at speeds three times that of sound through a magnetic field only 3 feet long and with the magnetic poles 6 inches apart."[35]
Figure 7.—The possible power source for space ships of the future, the ion jet, has significant counterpart uses for the commercial world.
Another possible source is photoelectric power. While a number of very difficult problems block the practical generation of this kind of power, the astronautics research division of one American company has now succeeded in increasing the efficiency of photoelectric cells by a factor of more than 300.[36] So the possibilities in this area are looking up. As discussed in section II, photon power derived from the ejection of electromagnetic rays may someday prove a source for accelerating vehicles once they have escaped from Earth's gravity.
Another possibility, of course, is atomic energy about which much has been said and written. If, as some scientists believe, extensive space exploration by manned crews will depend on harnessing this great source of energy—both for booster purposes and for operating spacecraft in the distant parts of our interplanetary system—this fact alone may assure that the obstacles to practical nuclear energy are overcome faster and more completely than would otherwise be the case. It is interesting to note that the science of controlling nuclear fusion (as opposed to fission) has come so far in the past several years that 11 private power companies are pooling their resources to advance this state of the art.[37]