MILITARY GEOGRAPHY
FOR PROFESSIONALS AND THE PUBLIC
7. INNER AND OUTER SPACE
Icarus was a brave boy,
feathered wings his pride and joy.
He flew high and had fun
'til he neared the hot sun,
which melted his fragile toy.Anonymous
The First Space Flight
A Cautionary Limerick
MILITARY SPACE FORCES, UNLIKE MYTHOLOGICAL ICARUS WHO FLEW TOO CLOSE TO THE SUN, CURRENTLY confine their activities to inner space, where they perform crucially important reconnaissance, surveillance, target acquisition, tracking, communications, navigational, meteorological, missile warning, and verification missions in a medium quite different than land, sea, or air.1 Combat operations eventually may occur,2 but interplanetary warfare seems far in the future for political, economic, military, and technical reasons. Round trips to Mars, for example, would take 2 or 3 years. The following discussions therefore concentrate on four distinctive regions within the Earth-Moon System: Aerospace Interfaces, Circumterrestrial or Inner Space, the Moon and Its Environs, and an amorphous Outer Envelope, beyond which outer space begins (map 23).
SPACE COMPARED WITH LAND AND SEA
Air, water, weather, climate, and vegetation within the Earth-Moon System are exclusively indigenous to this planet.3 Land forms and natural resources are restricted to the Earth, Moon, and asteroids. Cosmic radiation, solar winds, micrometeorites, and negligible or neutralized gravity are unique properties of space. Near vacuum is present everywhere except on Earth and vicinity.
Space and the seas are superficially similar, but differences are dramatic:
Space moreover has no north, east, south, or west to designate locations and directions. A nonrotating celestial sphere of infinite radius, with its center at Earth's core, is the reference frame. Declination, the astronomical analog of latitude, is the angular distance north or south of the celestial equator, right ascension is the counterpart of longitude, and the constellation Aries, against which spectators on Earth see the sun when it crosses Earth's Equator in springtime, defines the prime meridian. Angular positions in space are measured from that celestial counterpart of Greenwich Observatory.
Distances in space are meaningful mainly in terms of time. Merchant ships en route from the U.S. Pacific coast to the Persian Gulf typically take about a month to sail 12,000 nautical miles (22,240 kilometers). Apollo 11 flew to the Moon, 20 times as far, in slightly more than 3 days. Real time communications, transmitted at 186,000 miles per second (the speed of light on Earth and in space) are possible despite great distances--the delay between Earth and Moon amounts to about 1 second.
REGION I: AEROSPACE INTERFACES
Four geographic factors in Region I influence transits to and from space: atmosphere and gravity, together with Earth's rotation and inclination. Some effects are militarily adverse, whereas others are advantageous.
ATMOSPHERE
Half of Earth's atmosphere is located less than 3 miles above sea level (4.6 kilometers), in the bottom of the troposphere (figure 22).4 Most humans need supplemental oxygen to sustain efficient performance well before they reach that elevation. Pressurized suits or cabins become obligatory at about 9 miles, because crew members, unable to expel carbon dioxide and water vapor from their lungs unassisted, otherwise would suffocate. Their blood literally would boil above 12 miles in the absence of such protection. Military aircraft and space vehicles depend on pure air produced in a sealed environment after they approach altitudes that approximate 15 miles, where heat transfer is excessive and poisonous ozone is present. Turbojet engines refuse to function much above 20 miles; ramjets sputter and stop when altimeters register 28 miles (45 kilometers); rockets are required beyond that point.
High winds, extreme turbulence, lightning, and ice often cause launch and landing delays, even for remotely-piloted aircraft and unmanned space vehicles on tight military schedules. The top-heavy U.S. piggyback space shuttle, which often transports sensitive cargo for the U.S. Department of Defense, might capsize if it tried to take off
Figure
22. Aerospace Interfaces
when crosswinds exceed the currently permissible 15 miles per hour (24 kph). Thunderbolts, such as the one that destroyed a U.S. Atlas-Centaur rocket laden with a multimillion dollar communications satellite in March 1987, pose similar hazards.
Spacecraft must overcome strong aerodynamic drag immediately after launch, but resistance becomes progressively weaker as they rise through the troposphere, because thinner air bears down with less pressure and the amount of fuel expended lightens the load they must lift. They break free for practical purposes where the mesosphere and thermosphere merge at an altitude that averages about 60 miles (95 kilometers). Frictional heat consumes space vehicles of all kinds when they reenter Earth's atmosphere at high velocities unless a shield protects exteriors and insulation keeps crews (if any) and other contents acceptably cool. Apollo command modules returning from the Moon, for example, had to offset 5,000 oF (1,900 0C), four times that of blast furnaces.
Friction nevertheless exerts some positive effects. Aerodynamic drag at the interface where atmosphere and space imperceptibly merge can act as a brake or alter orbit configurations without burning fuel, provided computers calculate reentry angles correctly. Spacecraft skip or bounce back erratically when trajectories are too shallow and incineration results when they are too steep, but reentry windows as a rule open wider for powered vehicles than for those that glide.
GRAVITY
Propulsion systems must be powerful enough to boost military spacecraft into orbit, despite atmospheric drag and gravity (g), which keeps objects on Earth without an anchor and pulls unsupported bodies from atmosphere or space toward the surface.5 Astronauts and payloads both experience enormous stress during vertical liftoffs, because net force, acceleration, and velocity all increase rapidly when engines consume propellants (about 90 percent of the original weight) and expel mass in the form of exhaust. Gravitational attraction decreases with altitude, but is still 1 full g at 100 miles (160 kilometers), well beyond the upper boundary of Region I.
Spacecraft in orbit maintain constant speeds that are little affected by atmospheric drag or gravity. Those that follow circular paths fall the same distance every second that Earth's curved surface seems to recede and thus stay in proper position, aided only by minor adjustments to prevent drifting (figure 23). Braking enables them to attain lower orbits or return to Earth, whereas additional energy propels them farther out. All spacecraft and contents not battened down become "weightless" unless slow rotations create artificial gravity, because they free fall constantly at the same rate.
ROTATION AND INCLINATION
The entire Earth-Moon System, with its center of mass 1,000 miles beneath Earth's surface, completes one elliptical orbit around the sun every 365.25 days at a mean linear velocity of 666,000 miles per hour (1+ million kph).6 The Earth, tipped on its axis 23 degrees 27 minutes with respect to that orbit, rotates (spins) west to east 1,040 miles per hour at the Equator (1,675 kph), half as fast at the 60th parallels, and remains stationary only at the North and South Poles. One complete turn equals one day. Military spacecraft launched due east get a flying start from Earth's rotation, which makes it easier to attain orbital velocities. Benefits are greatest for vehicles near the Equator and progressively less toward each pole, where advantages are nil. Rotation neither assists nor resists launches that point north or south.
Figure 23. Gravity Versus Space
Vehicle Velocity
Orbital altitudes determine the time it takes to complete one circuit around Earth. The period is 90 minutes for circular orbits at 125 miles (200 kilometers), less at lower altitudes, and longer higher up where paths are lengthy and less velocity is needed to counteract gravity. The period of elliptical orbits averages the nearest and farthest distances from Earth. Spacecraft achieve geosynchronous orbits at a mean altitude of 22,300 miles (35,885 kilometers), where their 24-hour flight around the world corresponds precisely with the time it takes Earth to rotate once on its axis. Geosynchronous orbits that are circular and equatorial are called geostationary, because they seemingly hover over a single spot, while other Earth orbits make figure eights from center lines over the Equator. Sun synchronous orbits pass over prescribed spots at the same local time every day, come winter, summer, spring, or fall. Such options are useful for many military purposes, especially intelligence collection and communications.
REGION II: CIRCUMTERRESTRIAL SPACE
Circumterrestrial or inner space, as defined herein, 7 is a harsh region that begins about 60 miles above Earth, where aerodynamic drag and frictional heat lose most of their significance. Asteroids and meteoroids that weigh many tons hurtle through the void at 30,000 to 160,000 miles per hour. Catastrophic collisions with spacecraft seem improbable, although manmade "trash" is potentially troublesome and high-speed particles that pepper capsules and space suits over long periods not only pit optical lenses but chip temperature control surfaces. The latter are particularly important, because surface temperatures of objects in the thermosphere sometimes exceed 2,500 0F (1,400 0C). Sunlit sides anywhere in circumterrestrial space figuratively fry, while shady sides freeze, unless reflectors and insulating shields protect them. Moreover, systems must be designed to expel excessive heat generated on board.
Space, which lies beyond "the wild blue yonder," is absolutely black because light cannot scatter in very thin air or hard vacuums. Total silence also prevails, and there are no shock waves or sonic booms, regardless of vehicle velocities. Earth's gravity, in combination with other perturbations such as solar winds, electromagnetic forces, and lunisolar gravitation above geosynchronous levels, radically warps spacecraft orbits over time unless corrected. "Cold welding" can occur if metals touch accidentally, because no film of air separates exposed surfaces, while structures that are frigid on one side and torrid on the other undergo great stress.
X-rays, ultraviolet light, and infrared flood the ionosphere and magnetosphere. Two Van Allen radiation belts, separated by a low-density slot, girdle the globe with magnetic fields between latitudes 45 degrees north and south. The inner belt begins between 250 and 750 miles above Earth and tapers off at about 6,200 miles. The outer belt expires at 37,000 to 52,000 miles, depending on solar activity. Adequate shielding, coupled with prudent flight planning that reduces time in the most dangerous zones, is the best way to avoid overdoses and electronic disruptions that could interfere with important military missions.
Cosmic rays beyond the Van Allen belts pose additional problems. Sporadic solar flares cause proton storms that project high-energy, high-charge, high-density, long-range flux a million times more powerful than particles in routine solar winds. Less potent doses can damage or destroy human cells, including components of the central nervous system, cause communication blackouts, and discombobulate poorly protected guidance systems. Forecasts that defer flights or recall them in time to avoid solar flares consequently are crucial.
REGION III: MOON AND ENVIRONS
The voyage from Earth to the Moon averages 240,000 miles (386,000 kilometers) of cislunar space that is environmentally much the same as circumterrestrial space above the Van Allen belts (map 24). Lunar attributes and the significance of lunar libration points, however, merit special mention.
EARTHLY AND LUNAR GRAVITY WELLS
Military space forces at the bottom of Earth's "gravity well" need immense energy to leave launch pads and climb quickly into space. Adversaries at the top, in positions analogous to "high ground," have far greater maneuver room and freedom of action. Put simply, it is easier to drop objects down a well than to throw them out. Gravitational pull on the Moon is one-sixth as strong and related launch problems consequently are miniscule in comparison, as figure 24 shows.8
LUNAR TERRAIN
The Moon's square mileage is essentially the same as Africa's. The diameter at its Equator is 2,160 miles (3,475 kilometers), a little more than one-fourth that of Planet Earth. That bleak orb rotates once on its axis in 27.3 days, the same time it takes to complete one revolution around our world, so lunar days and nights each last 2 weeks, and the Moon eternally presents the same face to observers on Earth. Temperatures at a depth of 3 feet or so consistently register about -46 0F, but sunlit equatorial surfaces sizzle well above the boiling point on Earth, 212 0F (86 0C), and dip below -245 0F (-104 0C) after dark.9
Lunar terrain, devoid of atmosphere, vegetation, and water (except perhaps for ice at the poles), features rough highlands on the far side, while huge shallow saucers predominate on the side we see--Galileo called them maria, because they looked like seas through his telescope. Ridges and canyons known as rilles cross-hatch to form a lunar grid. Bowl-shaped craters, some of which have extremely steep sides, boulders, blocks, dimples, and hummocky debris make smooth topography hard to find. Lunar dust, called fines, mantles most of the level land, but abundant natural resources such as iron, titanium, aluminum, manganese, calcium, and silicon lie just beneath the surface. Construction materials also are accessible.
Map makers and armed forces lack any criterion comparable to sea level from which to define elevations and depths. Each molehill and mountain therefore must be measured from base to crest, each canyon and crater from top to bottom. Pike's Peak in the Colorado Rockies would loom slightly less than 9,000 feet instead of 14,110 if calculated in that fashion, because its base is more than a mile above sea level.
LUNAR LIBRATION POINTS
Five so-called lunar libration points are not points at all, but three-dimensional positions in space, shaped somewhat like kidney beans 10,000 miles (16,000 kilometers) long (map 24).10 Spacecraft theoretically could linger there indefinitely without expending much fuel if calculations are correct, because Earthly and lunar gravitational fields seem to cancel each other. Mathematical models and computer simulations conclude that free-floating objects at semistable L1 through L3, on a line with Earth and Moon, would gradually wander away, while substances at stable L4 and L5, which are 60 degrees ahead and behind the Moon in
Figure 24. Earthly and Lunar Gravity Wells
its orbit, would resist drift more vigorously and thus remain in the
general region. Those hypotheses, however, have not yet been verified. There are no known
counterparts of the Trojan Asteroids that inhabit areas similar to L4 and L5 along
Jupiter's orbit, nor have captive particle clouds been proven.
REGION IV: OUTER ENVELOPE
Region IV, which radiates from Earth in all directions, shares most characteristics of cislunar space. Its immense volume affords valuable maneuver room devoid of sizable matter, except for small asteroids (some rich in raw materials) that cross Earth's orbit. Region IV terminates at twice the distance to the Moon, beyond which solar and other planetary influences dominate.
TIPS FOR MILITARY SPACE PLANNERS
ORBITAL OPTIONS
Orbital options, which are virtually limitless, hypothetically could connect all points in the Earth-Moon System, but atmospheric interfaces, gravity, and radiation in fact confine flexibility.11 Aerodynamic drag and gravitational pull rule out high-speed Earth-to-space launches with currently envisioned vehicles, even in perfect weather. Enemy land-based defenses may straddle well-known launch trajectories that take advantage of Earth's rotation. Routes in space are relatively easy for opponents to predict, sharp altitude and inclination changes are costly to make in terms of fuel and time, and even minor deviations demand fine-tuned activation by auxiliary thrusters. Loop-the-loops, barrel rolls, violent evasive actions, and other flamboyant tactics popularized in movies like Star Wars will remain science fiction until technologists develop new ways to maneuver in a vacuum. Polar orbits could bypass both Van Allen radiation belts, which further restrict the choice of routes for manned flights, but in so doing would encounter parts of the magnetosphere that serve as funnels for intermittent solar flares that could cripple military operations in the absence of better shielding than currently is available. Reentry angles that avoid excessive frictional heat when spacecraft hit Earth's atmosphere also canalize approaches, and thereby reduce prospects for strategic or tactical surprise.
STRATEGIC LOCATIONS IN SPACE
A few fixed orbits confer valuable advantages in space. Three geostationary communications satellites positioned equidistantly around the circular track that runs 22,300 miles (35,885 kilometers) above our Equator can receive signals from, and relay them to, any place on Earth except the poles. Reconnaissance and surveillance satellites that make north-south great circles around the world sooner or later get a good look at every place on this globe.
All five lunar libration points constitute strategic locations in space. L1, the lowest energy transfer site for 230 million mile trips between Earth and Mars, could be fitted with military facilities as well as the "motel/gas station/warehouse/restaurant/garage" that the U.S. National Commission on Space once envisaged.12 L2 is a potentially important clandestine assembly area, since cislunar and Earth-based sentinels cannot see it. L3 could become a semi-stable staging base for military operations directed against Earth or spacecraft in orbit around it Nature, however, has reserved decisive advantages for L4 and L5, the two stable libration points, which theoretically could dominate Earth and Moon because they look down both gravity wells. No other location is equally commanding.
Occupying armed forces would possess great strategic leverage with which to mount operations from the Moon. Offensive and defensive warfare on the Moon, however, would be a catch-as-catch-can proposition until technologists produce the equivalent of a Global Positioning System (GPS) for lunar use or cartographers develop large-scale maps that identify precise elevations and include a military grid upon which to plot ranges and pinpoint positions.
WEAPON EFFECTS
Geographic influences on nuclear, directed energy, chemical, biological, and conventional weapon effects are far-reaching and fundamental. Atmospheric interfaces, gravity, and vacuum are the most important factors.
Nuclear Weapon Effects. Nuclear weapons detonated in Earth's atmosphere create shock waves, violent winds, and intense heat that inflict severe damage and casualties well beyond ground zero.13 No such effects would occur in space, because winds never blow in a vacuum, shock waves cannot develop where no air, water, or soil resists compression, and neither fireballs nor superheated atmosphere could develop more than 65 miles (105 kilometers) above Earth's surface. Consequently, it would take direct hits or near misses to achieve required results with nuclear blast and thermal radiation.
Initial nuclear radiation from beta particles and gamma rays would radically alter the ionosphere, warp or weaken radio and radar waves, and cause lengthy high frequency (HF) blackouts over vast areas on Earth (the megaton-range TEAK test shot, detonated in the mesosphere over Johnson Island on August 1, 1958, degraded HF radio traffic for several thousand miles in every direction from shortly after midnight until sunrise). X-rays, which Earth's atmosphere absorbs within a few feet, travel thousands of miles at the speed of light in space. Strong doses can peel spacecraft skins and destroy delicate mechanisms. Electromagnetic pulse (EMP), widespread and potentially paralyzing to electronics on land, at sea, or in the air, would occur if a cascade of gamma rays from any high altitude nuclear explosion collided with Earth's upper atmosphere (figure 25). A prodigious surge that peaks 100 times faster than lightning would bolt toward ground, then attack unshielded electronics. Solid state circuitry would be especially vulnerable, because miniature components cannot tolerate high currents and immense voltages able to melt semiconductors would instantaneously turn sophisticated systems into trash.
Directed Energy Weapon Effects. Directed energy weapons, if and when perfected, will project energy at or near the speed of light over great distances, but none now under serious consideration could perform equally well on Earth and in space. Problems consequently will arise if they try to cross the interface.14
Space is a nearly perfect environment for high-energy lasers, because light propagates unimpeded in a vacuum. Power output is the principal range limitation. Diffraction is significant over long distances, but is controllable. High-powered microwave weapons in experimental stages reportedly would work well in space, but break down dielectrically in atmosphere at relatively low energy levels, which would fatally impair space-to-Earth or Earth-to-space lethality. Particle beams suffer from similar shortcomings, because charged particles propagate well only in Earth's atmosphere and neutral particles only in a vacuum. The boundary between will remain a barrier to both unless scientists and technologists facilitate better conduction. Vehicles designed to survive intense reentry heat, however, would be vulnerable in space, where charged particle beams could penetrate hardened exteriors without burning a hole, then successfully attack components, propellants, and explosives not specifically protected.
Figure 25. Electromagnetic Pulse Propagation
Chemical and Biological Weapon Effects. Self-contained biospheres in space afford a superlative environment for chemical and biological warfare compared with Earth, where weather and terrain virtually dictate delivery times, places, and techniques.15 Most spacecraft and installations on the Moon, which must rely on closed-circuit life support systems that continuously recirculate air and recycle water, are conceivable targets for special operations forces armed with colorless, odorless, lethal, or incapacitating agents that would be almost impossible to spot before symptoms appear. Cumbersome masks and suits could protect individuals only if worn constantly. Sanctuaries comparable to the toxic-free citadels that eat up precious room on some ships would be infeasible for most spacecraft and safeguard only a few selected personnel. Any vehicle or structure victimized by persistent chemicals probably would become permanently uninhabitable, because vast quantities of water and solvents required for decontamination would be unavailable.
Conventional Weapon Effects. Tanks, cruise missiles, and other systems with "air-breathing" engines would be inoperative on the Moon's airless surface.16 Alternatives currently under exploration include battery-powered motors and rocket-propelled engines that oxidize fuel on board. Newton's Third Law of Motion (to every action there is an equal and opposite reaction) establishes requirements for recoilless weapony in the vacuum of space, because blast otherwise would propel spaceborne firing platforms backward with momentum equal to that of the ammunition in flight. Newton's First Law of Motion (bodies in motion move in a straight line until another force intervenes) would basically regulate projectile trajectories on the Moon, where velocity and low lunar gravity unopposed by atmospheric drag make "fire-and-forget" systems attractive. Conventional explosives would have to hit targets directly or detonate nearby, because no shock waves amplify blast effects in a vacuum, but even bird shot-size fragments could easily puncture the thin walls of pressurized lunar facilities built to repel nothing much larger than micrometeoroids.
PERSONNEL PROFICIENCY
Humans in space need support systems that not only provide air, food, and water but regulate temperatures, humidity, pressures, light, noise, vibrations, and radiation. Such requirements would be difficult to satisfy for armed forces on extended deployments.17
Subsistence and Sanitation. A one-month supply of oxygen, food, and drinking water just for a crew of three amounts to more than a ton stored at the expense of precious propellant and military payloads. Each crew member in turn would deposit an equal amount of waste in the form of feces, urine, perspiration, internal gases, carbon dioxide, and other exhalation vapors that could quickly reach toxic proportions in a sealed capsule unless quelled, expelled, or sterilized. Life support systems currently dump or stow organic waste on short missions, but such practices do little to alleviate long-term resupply problems. High-priority research projects consequently emphasize alternative techniques.
Radiation Risks. Military space forces would enter a perilous realm of radiant energy as soon as they leave Earth's protective atmosphere. Risks would be least in low Earth orbits but rise rapidly in the Van Allen belts and beyond, where high-energy, high-charge cosmic flux poses persistent hazards, while solar flares and other eruptions on the sun, always of concern, reach peak intensities every eleven years. Human central nervous, blood, digestive, and reproductive systems are particularly vulnerable to such radiation, which assaults reproductive cells. Delayed effects that could include leukemia, solid tumors, cataracts, and infertility might retard military recruitment and retention programs. Flight plans that limit time in the Van Allen belts and forecasts that warn of acute solar activity would reduce military flexibility along with radiation dangers, but permissible exposure may have to fit on a sliding scale, because personnel under age 35 apparently can tolerate higher levels and recuperate more quickly than older persons, who seem better able to withstand moderate overloads for longer periods.
Motion Sickness and Weightlessness. Motion sickness, somewhat like an aggravated form of sea sickness, afflicts about half of all space travelers whose responses to medical suppressants are unpredictable. It conceivably might undermine mission proficiency enough during the first few days of each flight to mark the difference between military success and failure, depending on which crew members suffer worst from symptoms that variously include drowsiness, indifference, and severe vomiting.
Weightlessness impairs response times, precision movements, and the work capacities of the best-trained, best-conditioned spacecraft crews. Dehydration occurs when the brain tells bodily organs to discharge fluids that pool in the chest. Blood, which thereafter thickens and flows less freely, supplies needy tissues with smaller than usual amounts of fresh nutrients and oxygen. Reduced abilities to exercise in turn cause muscles to lose mass and tone. Evidence so far suggests that most physically fit humans tolerate weightlessness reasonably well and recover completely after they return to a 1-g environment, although irreversible bone demineralization may be a significant exception. Artificial gravity may some day alleviate or eliminate the most debilitating aspects of weightlessness in large, slowly rotating space stations, but not in small, tactical space vehicles.
Group Proficiency. "Cabin fever" might affect teamwork adversely during very long military deployments, unless commanders took positive steps to limit and control psychological stresses caused by close confinement in space vehicles where the absence of identifiable days and nights deranges work-rest schedules like jet lag magnified many times. Manifestations range from emotional instability, fatigue, and short attention spans to impaired vital functions such as heartbeat, pulse, brain activity, body temperature, and metabolism. Some individuals perform best before breakfast, others after supper. Optimum unit efficiency therefore is possible only if crews contain a beneficial mix of biorhythms and schedules assign each member duties during his or her period of peak proficiency, because many military tasks make it impossible for all to work and relax simultaneously.
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