The void made full: The transformation of near-earth orbit from frontier to minefield

“ In his Physics Epicurus did little more than reproduce the doctrine of Democritus. He starts from the fundamental proposition that 'nothing can be produced from nothing, nothing can really perish.' The veritable existences in nature are the Atoms, which are too minute to be discernible by the senses, but which nevertheless have a definite size, and cannot further be divided. They have also a definite weight and form, but no qualities other than these. There is an infinity of empty space; this Epicurus proves on abstract grounds, practically because a limit to space is unthinkable. ”

“ Hence men imagined gods, and attributed those mighty phenomena of nature—earthquakes, tempests, lightning and thunder, and dire eclipses of sun and moon, to the vaguely visible powers which they imagined they saw. There was indeed a soul or spirit of the universe, as there was a soul or spirit of every individual thing that constituted it. But this was only a finer system of atoms after all. All else is convention or dream; the only realities are Atoms and Emptiness, Matter and Space. ”

“ In the Timaeus Plato attempts a vision of the universe as though he saw {151} it working itself into actuality on the lines of those ideas. The vision is briefly as follows: There is the Eternal Creator, who desired to make the world because He was good and free from jealousy, and therefore willed that all things should be like Himself; that is, that the formless, chaotic, unrealised void might receive form and order, and become, in short, real as He was. ”

“ Some comfort it would have been, could I, like a Faust, have fancied myself tempted and tormented of the Devil; for a Hell, as I imagine, without Life, though only diabolic Life, were more frightful: but in our age of Down-pulling and Disbelief, the very Devil has been pulled down, you cannot so much as believe in a Devil. To me the Universe was all void of Life, of Purpose, of Volition, even of Hostility: it was one huge, dead, immeasurable Steam-engine, rolling on, in its dead indifference, to grind me limb from limb. ”

“ No trace is left of their destructive powers, save the huge, unstratified, unfossiliferous deposits of clay and stones and bowlders, locked away between great layers of the sedimentary rocks.
Can it be that there wanders through immeasurable space, upon an orbit of such size that millions of years are required to complete it, some monstrous luminary, so vast that when it returns to us it fills a large part of the orbit which the earth describes around the sun, and showers down upon us deluges of débris, while it fills the world with flame? ”

“ All the stars are endowed with such movements more or less rapid, and not only all the stars—each of them a sun and most of them the centres of planetary systems, dispensers of light, heat, and harmony, around which gravitate habitable earths, the present, past, or future abodes of various beings and terrestrial things—not only, I say, are all the stars thus driven through the void, but all the planets, all the satellites, all the worlds and systems, all creation. ”

“ And so through the eons, as ever the comet's glory, the coma's power, has waned, they have driven it through another universe, destroying that universe to restore it. On through the limitless void of outer space they have driven it, a cosmic vampire looting the life of universes to restore its own! And now, when the comet's glory has again waned, they have turned it toward our own galaxy, to destroy it as they have done countless others. And within less than a scant half-dozen hours now the comet will have thundered so close to our galaxy that no power in existence can turn it aside! ”

“ In the ages to come man may be able to predict, perhaps even to control, the wayward courses of the winds and clouds, but hardly will his puny hands have strength to speed afresh our slackening planet in its orbit or rekindle the dying fire of the sun. Yet the philosopher who trembles at the idea of such distant catastrophes may console himself by reflecting that these gloomy apprehensions, like the earth and the sun themselves, are only parts of that unsubstantial world which thought has conjured up out of the void, and that the phantoms which the subtle enchantress has evoked to-day she may ban to-morrow. ”

“ All the pride and hope of human life goes to and fro in a little shell of air between this ancient globe of rusty nickel-steel and the void of space; faint specks we are within a film; we quiver between the atom and the infinite, being hardly more substantial than the glow within an oily skin that drifts upon the water. The wonder and the riddle of it! Here she and Trafford were! ”

“ In orbit, typical relative velocities are so high (~10-15 km/s) that even small pieces of debris can cause considerable damage if they collide with something else in orbit (i.e. bullets are small but cause significant damage due to their kinetic energy) , and create a growing risk for satellites.
Fig. 2 Visualisation of the currently tracked objects in Low Earth Orbit. Height is the average of apogee and perigee, relative to a mean Earth radius of 6,378 km. Blue dots are active satellites; red dots are "left overs" such as derelict satellites, rocket bodies and other large parts ”

“ Collision impacts on space operations
Growth of space debris The space community loosely divides objects in space into ‘active satellites’, ‘dead and leftovers’ such as derelict satellites and rocket stages, and ‘debris’, resulting from fragmentations, explosions and collisions. As described above, debris can in turn be divided into ‘tracked debris’, down to 10 cm size, and smaller ‘untracked’ debris, which can only be estimated. ”

“ Many human activities have a locally constrained environmental impact. Most space activities are however inherently global. A satellite may launch from California, but an hour later it is flying over France. Conversely, a Chinese or Russian system will soon appear in the sky over the USA. A coordinated international approach is therefore crucial, but this has to start with each sovereign state recognising its global responsibility. ”

“ We set sail on this new sea because there is new knowledge to be gained, and new rights to be won, and they must be won and used for the progress of all people. For space science, like nuclear science and all technology, has no conscience of its own. Whether it will become a force for good or ill depends on man, and only if the United States occupies a position of pre-eminence can we help decide whether this new ocean will be a sea of peace or a new terrifying theater of war. ”

“ In every actual case of motion the moving bodies are subject to friction and to collision, their energy is dissipated and they come to rest. This dissipation of energy is always accompanied by the generation of heat, and experience shows that the amount of heat generated is equivalent to the energy dissipated (first law of thermodynamics) . It is important to understand that the term dissipation of energy refers to the conversion of mechanical energy into heat by friction or collision. ”

“ When, however, we spoke of the conservation of force, in the case of elastic collision, we meant neither a pull nor a push, which, as just indicated, might be exerted upon inert matter, but we meant force invested in motion — the vis viva, as it is called, of the colliding masses.
Force in this form has a definite mechanical measure, in the amount of work that it can perform. The simplest form of work is the raising of a weight. ”

“ Calculating the likelihood of disabling damage by debris with size > 1 cm to active satellites is a complex problem requiring many physical variables. Note that disabling a satellite leaves an uncontrolled derelict that may then be a danger to other spacecraft. ”

“ The heat generated by such collisions is, however, vastly greater than that developed by the collision of a projectile against armor-plate, for the reason that the velocity of celestial bodies is so much greater, being commonly from thirty-five to fifty miles per second, and sometimes as high as two hundred miles per second, instead of but three-quarters of a mile per second. The heat developed by the collision of worlds is sufficient not only to fuse them, but also to gasefy them, and reduce them to their ultimate elements. ”

“ The physics of our century shows another great advance in what is called the kinetic theory of gases, for which Clausius and Maxwell paved the way, and which permits us a deep insight into the infinite fineness of matter and the inconceivable velocity of its internal motion. ”

“ In a gas under ordinary tension the molecules are in sufficient number to suffer almost constant collision with one another; but if the tension be low enough, say the one five-millionth of an atmosphere, the collisions become infrequent, and the molecules travel in almost uninterrupted straight lines until they come into contact with the sides of the containing vessel. ”

“ Under all known conditions these gaseous molecules are actually in rapid motion, each one moving at its own rate and in its own path, unaffected by any known force except gravitation. Each molecule will, accordingly, move in a straight line until it collides with another molecule. When two molecules collide, their direction of motion will be changed according to the angle of collision, but on account of their high elasticity they rebound with the same force with which they collide, and the sum of their motions will be practically the same as before. ”

“ The evolution of the satellite population, debris population and cumulative collisions for two possible satellite constellation scenarios at a height of 600 km with frequent deorbiting. a. 2,000 launches per year aimed at a stable population of 10,000 satellites. b. 10,000 launches per year aimed at a population of 40,000 satellites. ”

“ It is an established mechanical truth that if a body moving at a given velocity, strikes an equal body at rest in such wise that the two move on together, their joint velocity will be but half that of the striking body. Now it is a law of which the negative is inconceivable, that in passing from any one degree of magnitude to another all intermediate degrees must be passed through. Or in the case before us, a body moving at velocity 4, cannot, by collision, be reduced to velocity 2, without passing through all velocities between 4 and 2. ”

“ From the motion of sensible masses, by gravity and other means, we now pass to the motion of atoms towards each other by chemical affinity. A collodion balloon filled with a mixture of chlorine and hydrogen being hung in the focus of a parabolic mirror, in the focus of a second mirror 20 feet distant a strong electric light was suddenly generated; the instant the concentrated light fell upon the balloon, the gases within it exploded, hydrochloric acid being the result. Here the atoms virtually fell together, the amount of heat produced showing the enormous force of the collision. ”

“ The red point that was Mars hung almost above them, it seemed, almost in the center of the vitrolite dome of the bridge. "We are not heading directly for the planet," Captain Brand told Bill. "Its orbital velocity must be considered. We are moving toward the point that it will occupy in twenty days."
"We can make it in twenty days? Three million miles a day?"
"Easily, if the vitalium holds out, and if we don't collide with a meteorite. There is no limit to speed in space, certainly no practical limit. Acceleration is the important question." ”

“ A form of matter so different from any that can be found or produced on the surface of the earth can hardly be explained by our ordinary views of matter. A theory has, however, been propounded by Sir Norman Lockyer, so ingenious as to be worthy at least of mention. It is that these objects are vast collections of meteorites in rapid motion relatively to each other, which come into constant collision. Their velocity is such that at each collision heat and light are produced. ”

“ The speed v, then, at which a satellite must be moving round the planet to have the same velocity as the average particle within the planet's orbit, is
This velocity is, for the several planets:—
If the satellite be moving in its orbit less fast than this, its space-speed will exceed that of the average particle; it will strike the particle at its own rear and be accelerated by the collision. If faster, the particle will strike it in front and retard it in its motion round its primary. ”

“ For the law of gravity teaches that the same causes which tend to change the direction and velocity of the planet's motion tend in precisely the same degree to change the direction and velocity of the ring's motion. But when Huyghens made his discovery it must have appeared a most mysterious circumstance that a ring and planet should be thus constantly associated—that during thousands of years no collision should have occurred whereby the relatively delicate structure of the ring had been destroyed. ”

“ As we shot away we saw the little white body gleaming in the sunlight like a thistledown, and then it disappeared forever.
"It is a new planet born," said Edmund, "and the law of gravitation will pay it as much attention as if it were a Jupiter. It may wander in space for untold ages, and sometime it may even fall within the sphere of the earth's attraction, and then Jack's wish will have been fulfilled ”

“ Uneasiness became alarm a month173 later when, with American satellites still sitting on the launching pad, Sputnik II roared into space. A ball of fire floating over a field in western Texas provided the small stimulus needed to turn alarm into hysteria, and for several weeks people tended to see spaceships in every cloud and every unfamiliar light in the sky. The reasoning seemed to be that if man with his limited powers could launch satellites to orbit the planet, why shouldn’t interplanetary ships already be visiting the earth? ”

“ Medium Earth Orbit (MEO) is at altitudes around 20,000 km, within a broad range. This is the regime of global navigation satellite systems such as GPS and GLONASS, but also recently of some internet communications systems such as O3B. Satellites in MEO take around 12 hours to orbit the Earth, and each satellite can communicate with a fairly large portion of the Earth’s surface. From the perspective of a person on Earth, a spacecraft in MEO will move across the sky much more slowly, and remain in the field of view for an hour. ”

“ Without avoidance methods, the current debris density means there will on average be one collision per satellite every 50 years in LEO, with a piece of debris that is 10 cm or larger [4] . However, large objects are tracked and orbital elements made publicly available, so that potential collisions can be predicted and actively avoided. ‘Conjunctions’, where one satellite passes within a few km of another, happen many times every year, but so far only one major accidental collision has taken place. ”

“ Satellites can even have their electronics overloaded and be permanently disabled. With the huge increase in the number of satellites and the increased collision risk, active collision avoidance by many satellites will be frequent. If satellites are disabled, even temporarily, they will lose the ability to manoeuvre around hazards and the collision risk will increase dramatically every time a satellite enters “safe mode” or is disabled. ”

“ Ground and airspace collision
It is unlikely that all de-orbited satellites will burn up completely, or that all surviving rocket parts, including unspent fuel, will be successfully dumped in the sea, so damage to property and even life will be an increasing risk. Disposing of satellite remnants in a marine environment has environmental risk, which has been successfully challenged in the past [28,29] . The risk to life and impact on the environment is non-trivial. ”

“ Descending debris also poses a risk to aircraft. From the same UN presentation, predictions suggest a 1 in a 1000 chance of an aircraft being struck each year, but with some 300 passengers per aircraft, that means 0.3 casualties per year. A possible population of 100,000 satellites increases the casualty rate by many times. The first aircraft strike or ground casualty is only a matter of time. ”

“ Far away in that blackness the eye could in time make out, hardly to be seen, a few faint little patches of misty light, glowing feebly to our eyes across the mighty gloom of space; faint patches of light that were, I knew, galaxies of stars, island-universes like our own, separated from our own by a titanic void of millions of light-years of space, an immensity of emptiness into which even the swiftest of our ships could not venture, and beside which the distances between our own stars seemed tiny and insignificant. ”