Satellite communications and the progressive replacement of cables by
fiber optical communication (again, the best optical fibers could be
produced in orbital factories) will lead to a communications explosion.
Much has been said about it and about the revolutionary aspects for
education in both industrially developed and developing countries.

To educate without offering prospects for utilizing the improved human
resources through meaningful employment can have destabilizing social effects.
In the industrialized countries, and even more so in developing countries,
dication must go hand in hand with economic growth to ensure adequate
job markets in the production and services sectors. Here the key is
energy.

Our present energy world is shrinking rapidly as continued global
industrialisation demands its expansion. To reverse this process, the
development of coal, fission, solar and fusion sources must be pursued.
The age of cheap, abundant energy need not be over, but it is not only
vital to our time, it is the most important heritage we can bestow on
succeeding generations to ensure their quality of life on a planet from
which we skimmed the richest and most readily accessible resources.
In the energy sector, more than in any other, the future depends on
our problem-solving capacity, for, as our bodies cannot exist long
without breathing, our industrial civilization cannot last through a
prolonged period of lack of available energy. Therefore, we cannot
leave this problem to posterity. Our problem-solving capacity, in turn,
is enhanced by adding a new, industrial option bank in space.

In the space energy sector, one must distinguish between using energy
in space for material processing and production, in order to reduce
energy consumption within the biosphere, and utilizing space as a
source of energy for use on Earth.

Photovoltaic systems are a natural for supplying energy to orbiting
information and manufacturing systems. Here ·
NASA-planned power
units from 50 to perhaps 100 kwe size will be adequate, at least for
the 1980s. For example, a very advanced person-to-person comsat with
1.2 million channels requires about 600 kwe.

Most anticipated space manufacturing processes indicate power requirements
within 500 kwe. Due to the strength of the gravitational pull of Earth
and the associated transportation costs, only items of relatively low
mass but high quality and product value are economically competitive.
In the lunar-industrial product sector, on the other hand, larger masses
and cost-effective extraction of desired elements from lunar materials

and oxides are the key to aconomic viability. Here much higher power
levels are involved. Unavailability of solar energy during lunar night
and the desirability of underground extraction render fusion power
particularly attractive.

Controlled fusion power is the key to the ultimate economy and versatility
of space industrial productivity. Consequently, plasma research and
experiments toward fusion reactors should be given high priority early in
space industrial research and development planning. Fusion reactors are
complex, with complex auxiliary systems for plasma heating and fueling,
complicated blanket and shield structures, energy storage and tritium
recovery, and handling. Nevertheless, it appears that operation in space
can reduce many of the most difficult engineering problems. A magnetically
confined fusion plasma requires a surrounding vacuum of 10-6 torr (1.3
billionth of an atmosphere). At lesser vacuum, the plasma pressure be-
comes impractically high. Space offers a vacuum of 10-8
torr • greatly
reducing both plasma pressure and required magnetic pressure.

Terrestrial vacuum chambers are relatively small, because of the
difficulties and cost of maintaining such high vacuum on the ground.
Since 80 percent of the energy released by a deuterium-tritium reaction

In comparing the optical and microwave transmission mode, the advantages of the latter are reduced atmospheric losses (low sensitivity to overcast,

except at hail formations), low thermal waste (most of the incoming energy converted back to electricity) and the ability to shape the beam through phase control, thereby avoiding the optical situation where a reflector's focal area increases with distance (barring costly special arrangements), due to the fact that the Sun is not a point source. For this, however, the space/ground system pays with greater complexity of Primary energy must be converted to electricity. The electricity must be converted to microwave energy which, in turn, its space component. must be shaped to a coherent beam and, on the ground, be re-converted to electricity.

Low atmospheric losses, therefore, are negated by multiple conversion losses.

The disadvantages of microwave transmission are rooted primarily in the fact that radiation at significant power densities is not part of the solar radiation input into the terrestrial environment (this is also an intrinsic disadvantage of the Power Relay Satellite concept proposed several years back by this author for transmitting large amounts of energy from remote primary sources on Earth to places of consumption; however this method was to be applied to some 10 to 20 systems, not to hundreds). One consequence of this concerns ionospheric radio frequency interference, which causes By limiting maximum power power loss and can cause ionospheric heating. intensity to about 17 percent of the Sun's optical radiation energy flux in the ionosphere of about 1.35 kw/sq. meter, this ionospheric effect can However, biological safety limits force be kept within acceptable limits. the power density at the beam's periphery to much lower values. Consequently, including a safety zone around the receiver system, the required land area corresponds to an energy influx of about 2.5 percent of the For the optical system kw/sq. meter solar constant on the ground. (Powersoletta) the output per unit land area is about twice as large. Therefore, microwave transmission requires significantly more receiver land area than Powersoletta, for equal output, even though the microwave The limitations are physical and biological, hence beam can be shaped. cannot be overcome by technological improvements.