Introduction

This section is both for:

  • Antigravity: things that fight the force of gravity; such as matter that "falls upwards", gravitational repulsion and gravity shielding

  • Paragravity: gravity generators, where you put electricity into one end and synthetic gravity comes out the other

Yes, the two categories tend to blur into each other sometimes.


Gravity is such a pesky thing. It prevents us from doing all sorts of wonderful things. Such as floating through the air like a balloon, traveling into orbit without paying an ugly cost in delta V, and being morbidly obese but still light on your feet like Baron Vladimir Harkonnen

By the same token, it would also be incredibly useful to be able to create gravity on command. Then you could do things like create artificial gravity inside your spacecraft without unwieldy centrifuges, preventing the crew from getting killed by multi-gee acceleration, and make attractor beams.

And do idiotic things like make the direction of "up" in your spacecraft at ninety degrees to the direction of thrust like they were space-going passenger airplanes (I'm looking at YOU Star Trek, Star Wars, Battlestar Galactica, and practically every other media SF show and movie).

Science has yet to figure out how to make either device, but they have been popular in science fiction at least since H. G. Wells wrote The First Men in the Moon in 1901.


Of course the easiest way to create an antigravity device is to attach a piece of buttered toast (butter side up) to the back of a cat and drop it.


And as a note on terminology, things in this section will be using "Gravitational Waves." The term "Gravity Waves" has already been appropriated by the science of fluid dynamics, they refer to ocean waves.

Antigravity

"Anti" means "opposed to, against". So antigravity is something that fights gravity. These include:


As a side note, understand that the astronauts in the International Space Station are NOT floating around in microgravity because they are beyond the range of Terra's gravitational field. The gravitational attraction of Terra at the altitude of the ISS is about 93% of one full gee, almost full strength.

The reason that everybody floats around is because they are in a state of "free fall." If you were in an elevator, and the cable snapped, you too would be in a state of free fall and would float around. At least until you hit. The station and astronauts are in free fall because they are in "orbit", which is a clever way to fall but never hit the ground. You can read more about the details here.

So people in the Space Station are in "zero gravity" in the sense of "undergoing an acceleration of 0.0 gs". Just like the Apollo astronauts are crushed by an acceleration of 3.94 g when they lift off. They are NOT in "zero gravity" in the sense of they are out of range of Terra's gravity.

Related terms are "free fall" and "microgravity."

Buck Rogers

Anthony Rogers made his first appeance in a 1928 story called Armageddon 2419 AD by Philip Francis Nowlan (synopsis here, public domain text here). It was followed by a sequel: The Airlords of Han (public domain text here). In 1929 it was turned into a newspaper comic strip: Buck Rogers in the 25th Century A.D.

The main item relevant to our interest is the antigravity material "inertron", which falls upward. Its main use is as "anti-ballast". By loading an aircraft with inertron anti-ballast, its weight (but not its inertia) is reduced. The effect is to drastically reduce the amount of thrust required to just keep the aircraft in the air. Later in the comic strip, this is used to make interplanetary spacecraft.

People use "jumping belts", a back pack full of enough inertron to reduce the user's weight to only a few kilograms. This allows the user to make jumps in excess of 15 meters (50 feet). Later, in the comic strip, small rocket engines are added to make flying belts.

Inertron

[Inertron] is a synthetic element…It reflects 100 percent of the heat and light impinging upon it. It does not feel cold to the touch, of course, since it will not absorb the heat of the hand. It is a solid, very dense in molecular structure despite its lack of weight…It is a perfect shield…in many ways resembles the fabled hypothetical antimatter. It can co-exist with matter from our universe without mutual destruction, but it doesn’t much like to. Given a choice, it will try and head to the nearest perfect vacuum — which, from a terrestrial point of view, is always straight up. Thus it forms an effective anti-gravity agent. It also has the happy faculty of being a nearly 100% perfect insulator against any and all forms of electromagnetic radiation.

From Armageddon 2419 AD by Philip Francis Nowlan (1928)

First Men in the Moon

"Cavorite" is a gravity shield. If you place a sheet of cavorite between an object and Terra's center, the object is no longer subject to Terra's gravity. Cavor's space ship is covered with cavorite roll-up window shades. All the shades are down except for the one facing the planet you want to travel to. The ship will be attracted to the planet; since the attraction of all other planets, moons, and the Sun are cut off.

This of course violates the law of conservation of energy, which is a no-no. But what did you expect from something written in 1901?


     The object of Mr. Cavor's search was a substance that should be "opaque" — he used some other word I have forgotten, but "opaque" conveys the idea — to "all forms of radiant energy." "Radiant energy," he made me understand, was anything like light or heat, or those Rontgen Rays there was so much talk about a year or so ago, or the electric waves of Marconi, or gravitation. All these things, he said, radiate out from centres, and act on bodies at a distance, whence comes the term "radiant energy." Now almost all substances are opaque to some form or other of radiant energy. Glass, for example, is transparent to light, but much less so to heat, so that it is useful as a fire-screen; and alum is transparent to light, but blocks heat completely. A solution of iodine in carbon bisulphide, on the other hand, completely blocks light, but is quite transparent to heat. It will hide a fire from you, but permit all its warmth to reach you. Metals are not only opaque to light and heat, but also to electrical energy, which passes through both iodine solution and glass almost as though they were not interposed. And so on.
     Now all known substances are "transparent" to gravitation. You can use screens of various sorts to cut off the light or heat, or electrical influence of the sun, or the warmth of the earth from anything; you can screen things by sheets of metal from Marconi's rays, but nothing will cut off the gravitational attraction of the sun or the gravitational attraction of the earth. Yet why there should be nothing is hard to say. Cavor did not see why such a substance should not exist, and certainly I could not tell him. I had never thought of such a possibility before. He showed me by calculations on paper, which Lord Kelvin, no doubt, or Professor Lodge, or Professor Karl Pearson, or any of those great scientific people might have understood, but which simply reduced me to a hopeless muddle, that not only was such a substance possible, but that it must satisfy certain conditions. It was an amazing piece of reasoning. Much as it amazed and exercised me at the time, it would be impossible to reproduce it here. "Yes," I said to it all, "yes; go on!" Suffice it for this story that he believed he might be able to manufacture this possible substance opaque to gravitation out of a complicated alloy of metals and something new — a new element, I fancy — called, I believe, helium, which was sent to him from London in sealed stone jars. Doubt has been thrown upon this detail, but I am almost certain it was helium he had sent him in sealed stone jars. It was certainly something very gaseous and thin. If only I had taken notes…

(ed note: Cavor creates a sheet of Cavorite, which immediately causes widespread local devastation on the scale of a tornado strike)

     "But the explosion — "
     "It was not an explosion. It's perfectly simple. Only, as I say, I'm apt to overlook these little things. Its that zuzzoo business on a larger scale. Inadvertently I made this substance of mine, this Cavorite, in a thin, wide sheet…."
     He paused. "You are quite clear that the stuff is opaque to gravitation, that it cuts off things from gravitating towards each other?"
     "Yes," said I. "Yes."
     "Well, so soon as it reached a temperature of 60 degrees Fahrenheit, and the process of its manufacture was complete, the air above it, the portions of roof and ceiling and floor above it ceased to have weight. I suppose you know — everybody knows nowadays — that, as a usual thing, the air has weight, that it presses on everything at the surface of the earth, presses in all directions, with a pressure of fourteen and a half pounds to the square inch?"
     "I know that," said I. "Go on."
     "I know that too," he remarked. "Only this shows you how useless knowledge is unless you apply it. You see, over our Cavorite this ceased to be the case, the air there ceased to exert any pressure, and the air round it and not over the Cavorite was exerting a pressure of fourteen pounds and a half to the square in upon this suddenly weightless air. Ah! you begin to see! The air all about the Cavorite crushed in upon the air above it with irresistible force. The air above the Cavorite was forced upward violently, the air that rushed in to replace it immediately lost weight, ceased to exert any pressure, followed suit, blew the ceiling through and the roof off….
     "You perceive," he said, "it formed a sort of atmospheric fountain, a kind of chimney in the atmosphere. And if the Cavorite itself hadn't been loose and so got sucked up the chimney, does it occur to you what would have happened?"
     I thought. "I suppose," I said, "the air would be rushing up and up over that infernal piece of stuff now."
     "Precisely," he said. "A huge fountain— "
     "Spouting into space! Good heavens! Why, it would have squirted all the atmosphere of the earth away! It would have robbed the world of air! It would have been the death of all mankind! That little lump of stuff!"
     "Not exactly into space," said Cavor, "but as bad — practically. It would have whipped the air off the world as one peels a banana, and flung it thousands of miles. It would have dropped back again, of course — but on an asphyxiated world! From our point of view very little better than if it never came back!"

     "Imagine a sphere," he explained, "large enough to hold two people and their luggage. It will be made of steel lined with thick glass; it will contain a proper store of solidified air, concentrated food, water distilling apparatus, and so forth. And enamelled, as it were, on the outer steel — "
     "Cavorite?"
     "Yes."
     "But how will you get inside?"
     "There was a similar problem about a dumpling."
     "Yes, I know. But how?"
     "That's perfectly easy. An air-tight manhole is all that is needed. That, of course, will have to be a little complicated; there will have to be a valve, so that things may be thrown out, if necessary, without much loss of air."
     "Like Jules Verne's thing in A Trip to the Moon."
     But Cavor was not a reader of fiction.
     "I begin to see," I said slowly. "And you could get in and screw yourself up while the Cavorite was warm, and as soon as it cooled it would become impervious to gravitation, and off you would fly — "
     "At a tangent."
     "You would go off in a straight line — " I stopped abruptly. "What is to prevent the thing travelling in a straight line into space for ever?" I asked. "You're not safe to get anywhere, and if you do — how will you get back?"
     "I've just thought of that," said Cavor. "That's what I meant when I said the thing is finished. The inner glass sphere can be air-tight, and, except for the manhole, continuous, and the steel sphere can be made in sections, each section capable of rolling up after the fashion of a roller blind. These can easily be worked by springs, and released and checked by electricity conveyed by platinum wires fused through the glass. All that is merely a question of detail. So you see, that except for the thickness of the blind rollers, the Cavorite exterior of the sphere will consist of windows or blinds, whichever you like to call them. Well, when all these windows or blinds are shut, no light, no heat, no gravitation, no radiant energy of any sort will get at the inside of the sphere, it will fly on through space in a straight line, as you say. But open a window, imagine one of the windows open. Then at once any heavy body that chances to be in that direction will attract us — "

From First Men in the Moon by H. G. Wells (1901)

What Goes Up

This is a story by Sir Arthur C. Clarke for his collection Tales of the White Hart (a selection of scientific shaggy-dog stories). It is a tall tale, but contains a bit of scientific truth.


     "You'll all recollect, I'm sure, the scientist Cavor in Wells's First Men in the Moon, and the wonderful gravity-screening material Cavorite he discovered?"
     "I'm afraid dear old Wells didn't go into the question of Cavorite very thoroughly. As he put it, it was opaque to gravity just as a sheet of metal is opaque to light. Anything placed above a horizontal sheet of Cavorite, therefore, became weightless and floated up into space."
     "Well, it isn't as simple as that. Weight represents energy — an enormous amount of it — which can't just be destroyed without any fuss. You'd have to put a terrific amount of work into even a small object in order to make it weightless. Antigravity screens of the Cavorite type, therefore, are quite impossible — they're in the same class as perpetual motion."

(ed note: the point being that the Cavorite expends no energy when it degravitationalizes something. However, as we shall see, it is perfectly permissable to degravitationalize something provided you pay the horrific energy cost)


     "Now, our Australian Dr. Cavor wasn't searching for antigravity, or anything like it. In pure science, you can be pretty sure that nothing fundamental is ever discovered by anyone who's actually looking for it — that's half the fun of the game. Dr Cavor was interested in producing atomic power: what he found was antigravity. And it was quite some time before he realised that was what he'd discovered."
     "What happened, I gather, was this: the reactor was of a novel and rather daring design, and there was quite a possibility that it might blow up when the last pieces of fissile material were inserted. So it was assembled by remote control in one of Australia's numerous convenient deserts, all the final operations being observed through TV sets."
     "Well, there was no explosion — which would have caused a nasty radioactive mess and wasted a lot of money, but wouldn't have damaged anything except a lot of reputations. What actually happened was much more unexpected, and much more difficult to explain."
     "When the last piece of enriched uranium was inserted, the control rods pulled out, and the reactor brought up to criticality — everything went dead. The meters in the remote-control room, two miles from the reactor, all dropped back to zero. The TV screen went blank. Cavor and his colleagues waited for the bang, but there wasn't one. They looked at each other for a moment with many wild surmises: then, without a word, they climbed up out of the buried control chamber."
     "The reactor building was completely unchanged: it sat out there in the desert, a commonplace cube of brick holding a million pounds' worth of fissile material and several years of careful design and development. Cavor wasted no time: he grabbed the jeep, switched on a portable Geiger counter, and hurried off to see what had happened."
     "He recovered consciousness in hospital a couple of hours later. There was little wrong with him apart from a bad headache, which was nothing to the one his experiment was going to give him during the next few days. It seemed that when he got to within twenty feet of the reactor, his jeep had hit something with a terrific crash. Cavor had got tangled in the steering wheel and had a nice collection of brusies; the Geiger counter, oddly enough, was quite undamaged and was still clucking away quietly to itself, detecting no more than the normal cosmic-ray background."
     "Seen from a distance, it had looked a perfectly normal sort of accident that might have been caused by the jeep going into a rut. But Cavor hadn't been driving all that fast, luckily for him, and anyway there was no rut at the scene of the crash. What the jeep had run into was something quite impossible. It was an invisible wall, apparently the lower rim of a hemispherical dome, which entirely surrounded the reactor. Stones thrown up in the air slid back to the ground along the surface of this dome, and it also extended underground as far as digging could be carried out. It seemed as if the reactor was at the exact centre of an impenetrable, spherical shell."
     "Of course, this was marvellous news and Cavor was out of bed in no time, scattering nurses in all directions. He had no idea what had happened, but it was a lot more exciting than the humdrum piece of nuclear engineering that had started the whole business."
     "By now you're probably all wondering what the devil a sphere of force — as you science fiction writers would call it — has to do with antigravity. So I'll jump several days and give you the answers that Cavor and his team discovered only after much hard work and the consumption of many gallons of that potent Australian beer."
     "The reactor when it had been energised, had somehow produced an antigravity field. All the matter inside a twenty-foot-radius sphere had been made weightless, and the enormous amount of energy needed to do this had been extracted, in some utterly mysterious manner, from the uranium in the pile. Calculations showed that the amount of energy in the reactor was just sufficient to do the job. Presumably the sphere of force would have been larger still if there had been more ergs available in the power source."
     "I can hear someone just waiting to ask a question, so I'll anticipate them. Why didn't this weightless sphere of earth and air float up into space? Well, the earth was held together by its cohesion, anyway, so there was no reason why it should go wandering off. As for the air, that was forced to stay inside the zone of zero gravity for a most surprising and subtle reason which leads me to the crux of this whole peculiar business."
     "Better fasten your seat belts for the next bit: we've got a bumpy passage ahead. Those of you who know something about potential theory won't have any trouble, and I'll do my best to make it as easy as I can for the rest."
     "People who talk glibly about antigravity seldom stop to consider its implication, so let's look at a few fundamentals. As I've already said, weight implies energy — lots of it. That energy is entirely due to Earth's gravity field. If you remove an object's weight, that's precisely equivalent to taking it clear outside Earth's gravity. And any rocket engineer will tell you how much energy that requires."
     Harry turned to me and said: "There's an analogy I'd like to borrow from one of your books, Arthur, that puts across the point I'm trying to make. You know — comparing the fight against Earth's gravity to climbing out of a deep pit."
     "You're welcome," I said. "I pinched it from Doc Richardson, anyway."
     "Oh," replied Harry. "I thought it was too good to be original. Well, here we go. If you hang on to this really very simple idea, you'll be OK. To take an object clear away from the Earth requires as much work as lifting it four thousand miles against the steady drag of normal gravity. Now the matter inside Cavor's zone of force was still on the Earth's surface, but it was weightless. From the energy point of view, therefore, it was outside the Earth's gravity field. It was inaccessible as if it was on top of a four-thousand-mile-high mountain."
     "Cavor could stand outside the antigravity zone and look into it from a point a few inches away. To cross those few inches, he would have to do as much work as if he climbed Everest seven hundred times. It wasn't surprising that the jeep stopped in a hurry. No material object had stopped it, but from the point of view of dynamics it had run smack into a cliff four thousand miles high. . . ."

From What Goes Up by Arthur C. Clarke (1965)

Perry Rhodan

I wish to acknowledge the help I received from Michel Van for this section. He wishes to acknowlege the work of the late Rainer Castor, who did a yeoman's work on the scientific aspects of the Perry Rhodan universe. And who was a personal friend of Mr. Van.


In the 1960's Perry Rhodan books, an antigrav is a black box where you feed in power then a miracle occurs! It levitates! Useful for making spacecraft gently lift off, and also handy for antigravity elevators. About Perry Rhodan issue #300, antigrav was developed into a propulsion system. It was more versatile than the old fashion Impuls engine, but it was a power hog. Only smaller spacecrafts could use antigrav propulsion with the relatively weak fusion reactors for power. It wasn't until the 35th century with the advent of the Schwarzschild power reactors that huge spacecraft could use antigrav propulsion.

But in the real world year 2000, author Rainer Castor joined the Perry Rhodan writing team. He invented the details of the system inside the antigrav black box.

The primitive antigravity system is Robert Forward's protational field, which is an excellent choice. Field generators rotate Bose-Einstein condensates to generate the gravitational equivalent of a magnetic field. This is used to create a gravitational field for ship propulsion. But the propulsive force is weak and it is a power hog.

The advanced system uses hypercrystals (quartz crystals embedded with five-dimensional particles). The propulsive force is strong. Still a power hog, though.

Finally the Andruckabsorber ("pressure absorber") or Inertial Compensator was invented. It reduces the inertia of the ship and crew, which means the same propulsive thrust will give the ship a much higher acceleration. It reduces inertia by pushing part of the ship's atoms into hyperspace. There is a limit to how much you can push into hyperspace before the ship gets sucked in entirely, makes a random hyperspace jump to a random location, and shreds your andruckabsorber.

As a side note, the FTL drive in E. E. "Doc" Smith's classic Lensman series is the inertialess drive.


Perry Rhodan antigravity is based on manipulating gravitons. The study of graviton manipulation will lead physicist to the development of faster-than-light hyperspace propulsion.

Perry Rhodan Antigravtriebwerk units have three modes:

  • Gravo neutralizer / Gravo damper: reduces an existing gravitational field
  • Gravo amplifier / Gravitator: amplifies an exsisting gravitational field
  • Repulsor: produces an artificial repulsive force, anti-gravity, a synthetic gravity field of opposite polarity to natural fields

Gravo neutralizers and amplifiers are used to generate artifical gravity inside a spacecraft's habitat module, and to adjust planetary gravity to a comfortable level. Neutralizers are also used along with engines for vehicles (from personal backpack flying units to large cargo aircraft). Amplifiers are also used for attractor beams and for prison bondage fields.

Repulsors are used as defensive armor and as repellor rays.

However their main use is as a reactionless propulsion system: "gravo-lift". Dense objects called "effective masses" are acted upon by the repulsors. These objects are anchored to the main thrust-bearing structural members of the aircraft or starship. When the repulsors push the effective mass in the desired direction, thrust is created on the ship's structure. Yes, this violates Newton's Third Law, but this is a relatively mild violation compared to other equipment in the Perry Rhodan universe.

From my attempts to comprehend the Google Translate version of the German language Perry Rhodan wiki entry, I get the impression that the repulsor units can move their associated effective masses in any direction. Repulsors are not limited to repelling the effective mass directly away.

Ironwolf

Ironwolf was a sadly short-lived comic book title by Howard Chaykin. The protagonist: Lord Ironwolf, is the ruler over a planet covered with valuable antigravity wood. Starships are constructed out of the stuff. The evil Empress wants to offer large quantities of the wood as a bribe to the outer barbarians. Ironwolf refuses, is outlawed, and becomes a rebel in his flagship, the Limerick Rake. In order to prevent the wood from falling into the barbarian's hands, he is forced to fusion bomb his own planet to destroy the forests in a firestorm.

Space: 1889

Space: 1889 is a role-playing game that came out about the same time that K. W. Jeter coined the term "Steampunk".

In 1870 Thomas Edison invents the "ether propeller" which can propel Victorian spaceships via the luminiferous aether. He travels to Mars with Scottish soldier of fortune Jack Armstrong, and discovers that Mars is indeed inhabited. The Great Powers of Germany, France, Russia, Belgium, Great Britain, Italy, Japan and the USA rush to establish colonial empires on various regions of Mercury, Venus and Mars.

Mars is particularly valuable, since it is the soul source of the antigravity Liftwood.

Four-Day Planet

In many of H. Beam Piper's novels they use the Abbot Lift-and-Drive aka "contragravity". It is used everywhere, from starships, to aircraft, to armored fighting vehicles, to trucks, to cargo skids, to luggage, to small floating floodlamps.

They apparently require quite a bit of power. However this is not a problem with the widespread availability of tiny radiation-free nuclear power cells, some as small as a AAA battery. They are sheathed in "collapsium", which is condensed matter that will not allow radiation to escape nor allow the batteries to be broken open. Collapsium must be a nice thing to have. But in the real world the closest equivalent is neutronium, which explodes like a supernova if you remove it from the hypergravity of a neutron star.

Murell was interested in everything he saw, in the brief time while we were going down along the docks to where the Javelin was berthed. I knew he'd never actually seen it before, but he must have been studying pictures of it, because from some of the remarks he made, I could tell that he was familiar with it.

Most of the ships had lifted out of the water and were resting on the wide concrete docks, but the Javelin was afloat in the pool, her contragravity on at specific-gravity weight reduction. She was a typical hunter-ship, a hundred feet long by thirty abeam, with a squat conning tower amidships, and turrets for 50-mm guns and launchers for harpoon rockets fore and aft. The only thing open about her was the air-and-water lock under the conning tower. Julio, who was piloting the car, set it down on the top of the aft gun turret. A couple of the crewmen who were on deck grabbed our bags and hurried them inside. We followed, and as soon as Julio lifted away, the lock was sealed.

Immediately, as the contragravity field dropped below the specific gravity of the ship, she began submerging. I got up into the conning tower in time to see the water of the boat pool come up over the armor-glass windows and the outside lights come on. For a few minutes, the Javelin swung slowly and moved forward, feeling her way with fingers of radar out of the pool and down the channel behind the breakwater and under the overhang of the city roof. Then the water line went slowly down across the windows as she surfaced. A moment later she was on full contragravity, and the ship which had been a submarine was now an aircraft.


A hunter-ship looks big on the outside, but there's very little room for the crew. The engines are much bigger than would be needed on an ordinary contragravity craft, because a hunter-ship operates under water as well as in the air.


Finally, however, he quieted down, and the boat swung him around, bringing the tail past our bow, and the ship cut contragravity to specific-gravity level and settled to float on top of the water.


(ed note: from the description, it appears that the contragravity field reduces the influence of gravity on whatever is in the field. Either the submarine is build so it will sink to the bottom of Davy Jone's Locker without an active contragravity field (specific gravity greater than 1.0), or the contragravity can increase the influence of gravity as well as decrease it.)

From Four-Day Planet by H. Beam Piper (1961)

The Secret of the Ninth Planet

The Secret of the Ninth Planet is an archetypal Winston Science Fiction juvenile novel. Evil aliens are stealing Terra's sunlight and diverting the energy to Pluto. Oh noes! And by an outlandish series of events, the eighteen year old protagonist gets the golden opportunity to accompany a mission in an experimental antigravity spaceship to take the battle to the enemy. I mean ordinarily it would be the height of insanity to take a minor on a deadly combat tour in an untested spacecraft, but gee, the plot just gives them no choice. And what a trip it is! Nothing less than a grand tour of the entire solar system, visiting each planet in turn.

Like I said: archetypal Winston Science Fiction juvenile novel


     "We have in my company's experimental grounds one virtually untested vessel which may be able to make a flight to Mars, or any other planet, in the time allowed. This is the craft we refer to as A-G 17, the seventeenth such experiment, and the first to succeed. It is powered by an entirely new method of flight, the force of anti-gravity."
     Burl hung breathlessly on his next words. "You probably know that work on the scientific negation of gravity has been going on since the early 1950's. It was known shortly after experiments had been conducted on atomic and subatomic particles that grounds had at last been found by means of which a counteraction to gravity might be set up. Early subatomic studies showed that such a force was not only theoretically possible, but that certain subparticles actually displayed such tendencies. On the basis of these first discoveries, work has been going on in the development of negative gravitational drive for at least twenty years. As early as 1956, there were not less than fourteen such projects under way in virtually all the leading aircraft industries of the United States, not to mention the rest of the world. In the last few years, at the direction of the Air Force, these projects have been consolidated, placed under one main roof, and brought to its present status, which is, we believe, the one of final triumph."

     It was still, thought Burl, a large crew for a spaceship. No rocket built to date had ever been able to carry such a load. But by then he had realized that the strict weight limitations imposed by rocket fuels no longer applied to this new method of space flight.

     The A-G 17 loomed suddenly above them, and Burl's first impression was of a glistening metal fountain roaring up from the ground, gathering itself high in the sky, as if to plunge down again in a rain of shining steel.
     The ship was like a huge, gleaming raindrop. It stood two hundred feet high, the wide, rounded, blunt bulk of it high in the air, as if about to fall upward instead of downward. It tapered down to a thin, perfectly streamlined point which touched the ground. It was held uprightly by a great cradle of girders and beams. At various points the polished steel was broken by indentations or inset round dots that were thick portholes or indications of entry ports. Around its equator, girding the widest section was a ring of portholes, and there were scattered rings of similar portholes below this.
     As the three men drew near the tail, the great bulk loomed overhead, and Burl felt as if its weight were bearing down on him as they walked beneath.

     Suiting action to the word, the three went over to one of the loading platforms, climbed on the wiry little elevator, and were hoisted up fifty feet to the port in the side of the ship. They entered well below the vast, overhanging equatorial bulge which marked the wide end of the teardrop-shaped vessel.
     They walked through a narrow plastic-walled passage, broken in several places by tight, round doors bearing storage vault numbers. At the end of the passage they came to a double-walled metal air lock. They stepped through and found themselves in what was evidently the living quarters of the spaceship.
     The Magellan was an entirely revolutionary design as far as space vehicles were concerned. Its odd shape was no mere whimsy, but a practical model. If a better design were to be invented, it would only come out of the practical experience of this first great flight.
     It had long been known, ever since Einstein's early equations, that there was a kinship between electricity, magnetism, and gravitation. In electricity and magnetism there were both negative and positive fields manifesting themselves in the form of attraction and repulsion. These opposing characteristics were the basis for man's mastery of electrical machinery.
     But for gravitation, there had seemed at first no means of manipulating it. As it was to develop, this was due to two factors. First, the Earth itself possessed a gravitational phenomenon in this force outside of that intense, all-pervading field. Second, to overcome this primal force required the application of energy on such scales as could not be found outside of the mastery of nuclear energy.
     There was a simple parallel, Burl had been told the day before by Sam Oberfield, in the history of aviation. A practical, propeller-driven flying machine could not be constructed until a motor had been invented that was compact, light and powerful enough to operate it. So all efforts to make such machines prior to the development of the internal combustion engine in the first days of the twentieth century were doomed to failure. Likewise, in this new instance, a machine to utilize gravitation could not be built until a source of power was developed having the capacity to run it. Such power was found only in the successful harnessing of the hydrogen disintegration explosion — the H-bomb force. The first success at channeling this nuclear power in a nonbomb device had been accomplished in England in 1958. The Zeta-ring generator had been perfected in the next decade.
     Only this source of harnessed atomic power could supply the force necessary to drive an A-G ship.
     The nose of the Magellan housed an H-power stellar generator. Within the bulk of the top third of the ship was this massive power source, its atomic components, its uranium-hydrogen fuel, and the beam that channeled the gravitational drive.

(ed note: in fewer words, it's a fusion power reactor)

     "Negating gravity is not a simple matter like inventing a magic sheet of metal that cuts off the pull of the Earth, such as H. G. Wells wrote about," Oberfield had explained. "That is impossible because it ignores all the other laws of nature; it forgets the power of inertia, it denies the facts of mass and density. It takes just as much energy to lift an anti-gravity ship as to lift a rocketship. The difference is only in the practicality of the power source. A rocketship must burn its fuel by chemical explosion in order to push its cargo load upward. Its fuel is limited by its own weight and by the awkwardness of its handling. This A-G ship also must supply energy, foot-pound for foot-pound, for every foot it raises the vehicle. But due to the amount of energy supplied by this new generator, such power is at last available in one compact form in such concentration that this ship could propel itself for hundreds of years."
     He went on to explain that what then happened was that the vessel, exerting a tremendous counter-gravitational force, literally pushed itself up against Earth's drive. At the same time, this force could be used to intensify the gravitational pull of some other celestial body. The vessel would begin to fall toward that other body, and be repelled from the first body, Earth in this case.
     As every star, planet, and satellite in the universe was exerting a pull on every other one, the anti-gravity spaceship literally reached out, grasped hold of the desired gravitational "rope" hanging down from the sky, and pulled itself up it. It would seem to fall upward into the sky. It could increase or decrease the effect of its fall. It could fall free toward some other world, or it could force an acceleration in its fall by adding repulsion from the world it was leaving.
     In flight, therefore, the wide nose was the front. It would fall through space, pulled by the power beam generated from this front. The rear of the spaceship was the tapering, small end.
     As Burl was shown over the living quarters it became plain to him that the actual living spaces in the Magellan were inside a metal sphere hanging on gymbals below the equatorial bulge that housed the power drive. The bulk of this sphere was always well within the outer walls of the teardrop, and thus protected from radiation. Being suspended on gymbals, the sphere would rotate so that the floor of the living quarters was always downward to wherever the greatest pull of gravity might happen to be.
     Burl and the others explored the three floors that divided the inner sphere, all oriented toward Earth. The central floor, housing the sleeping quarters and living quarters, was compact but roomier than might have been expected. There were five bunkrooms, each shared by two men. There was a main living and dining room. On the lowermost floor was the cookroom, a small dispensary, and immediate supplies. On the upper floor was the control room, with its charts and television viewplates which allowed visi n all directions from sending plates fixed on the surface in various areas.
     In the spaces between the inner sphere and the outer shell were the basic storage areas. Here supplies and equipment were being stocked against all possible emergencies. In the tapering space of the tail below the sphere was a rocket-launching tube. Stored in the outer shells were various vehicles for planetary exploration.

     The great generators were beginning to push against Earth's gravity and, as their force moved upward to match Earth's, the weight of everything in their sway decreased accordingly. Lockhart's first move was simply that to reduce the pull of Earth to zero.
     In a few moments that point was accomplished. A state of weightlessness was obtained within the Magellan. Those watching outside from bunkers in the surrounding mountains saw the huge teardrop shiver and begin to rise slowly above its cradle of girders. It floated gently upward, moving slowly off as the force of Earth's centrifugal drive began to manifest itself against the metal bubble's great mass.
     Everyone on the crew had experienced zero gravity, either in the same tests Burl had undergone or on actual satellite flights, and thus far, no one was too uncomfortable. The entire structure of the ship quivered, and Burl realized that the inner sphere which housed their air space was hanging free on its gymbals.
     Lockhart rang a second gong, then turned a new control. The pitch of the generators, faintly audible to them, changed, took on a new keening. The ship seemed suddenly to jump as if something had grasped it. The feeling of weightlessness vanished momentarily, then there was a moment of dizziness and a sudden sensation of being upside down.
     For a shocking instant, Burl felt himself hanging head downward from a floor which had surprisingly turned into a ceiling. He opened his mouth to shout, for he thought he was about to plunge onto the hard metal of the ceiling which now hung below him so precipitously.
     Then there was a whirling sensation, a sideways twisting that swung him about against the straps. As it came, the room seemed to shift. The curved base of the control room, which had been so suddenly a floor, became in a moment a wall, lopsided and eerie. Then it shifted again. and, startlingly, Burl sagged back into his cushioned seat as the hemispherical room again resumed its normal aspect.

From The Secret of the Ninth Planet by Donald Wollheim (1959)

Larry Niven

Flatlander

Her full name was Slower Than Infinity. She had been built into a General Products No. 2 hull, a three-hundred-foot spindle with a wasp-waist constriction near the tail. I was relieved. I had been afraid Elephant might own a flashy, vulnerable dude’s yacht. The two-man control room looked pretty small for a lifesystem until I noticed the bubble extension folded into the nose. The rest of the hull held a one-gee fusion drive and fuel tank, a hyperspace motor, a gravity drag, and belly-landing gear, all clearly visible through the hull, which had been left transparent.


By then we were close enough to use the gravity drag to slow us. The beautiful thing about a gravity drag is that it uses very little power. It converts a ship’s momentum relative to the nearest powerful mass into heat, and all you have to do is get rid of the heat. Since the ST8’s hull would pass only various ranges of radiation corresponding to what the puppeteers’ varied customers considered visible light, the shipbuilders had run a great big radiator fin out from the gravity drag. It glowed dull red behind us. And the fusion drive was off. There was no white fusion flame to hurt visibility.


The red glow of the radiator fin became more pronounced. So did the dull uniformity of the planetary surface. The planet was a disk now beyond the front window; if you watched it for a while you could see it grow. Turning ship to face the planet had made no difference to the gravity drag.


We came out of hyperspace near the two Sirius suns. But that wasn’t the end of it, because we still faced a universe squashed by relativity. It took us almost two weeks to brake ourselves. The gravity drag’s radiator fin glowed orange-white for most of that time. I have no idea how many times we circled around through hyperspace for another run through the system.

(ed note: the ship had been boosted to relativistic velocity when they paid some technologically advanced aliens to do it. But after the mission they have to slow down via gravity drag.)

From Flatlander by Larry Niven (1967)
Grendel

With Lloobee missing and with the hyperwave smashed, the Argos proceeded to Gummidgy at normal speed. Normal speed was top speed; there are few good reasons to dawdle in space. It took us six hours in hyperdrive to reach the edge of CY Aquarii’s gravity well. From there we had to proceed on reaction drive and gravity drag.


“We could find the ship that brought him down. You can’t hide a spaceship landing. The gravity drag makes waves on a spaceport indicator.”


That was at five-gee acceleration, fusion drive and gravity drag, with four gees compensated by the internal gee field.


And I watched the Drunkard’s Walk, its fusion drive off, floating down ahead of me on its gravity drag.

From Grendel by Larry Niven (1968)

The Cruel Sky

And as he walked, there came a faint but unmistakable whine from the bulky backpack he was carrying on his shoulders.

That pack, indeed, was carrying him — or three-quarters of him. As he forged steadily along the last few feet to his once-impossible goal. Dr. Elwin and all his equipment weighed only fifty pounds. And if that was still too much, he had only to turn a dial and he would weigh nothing at all.

Here amid the Moon-washed Himalayas was the greatest secret of the twenty-first century. In all the world, there were only five of these experimental Elwin Levitators, and two of them were here on Everest.

Even though he had known about them for two years, and understood something of their basic theory, the “Lewies” — as they had soon been christened at the lab — still seemed like magic to Harper. Their power-packs stored enough electrical energy to lift a two-hundred-and-fifty-pound weight through a vertical distance of ten miles, which gave an ample safety factor for this mission. The lift-and-descend cycle could be repeated almost indefinitely as the units reacted against the Earth’s gravitational field. On the way up, the battery discharged; on the way down, it was charged again. Since no mechanical process is completely efficient, there was a slight loss of energy on each cycle, but it could be repeated at least a hundred times before the units were exhausted.

Climbing the mountain with most of their weight neutralized had been an exhilarating experience. The vertical tug of the harness made it feel that they were hanging from invisible balloons, whose buoyancy could be adjusted at will. They needed a certain amount of weight in order to get traction on the ground, and after some experimenting had settled on twenty-five per cent. With this, it was as easy to ascend a one-in-one slope (45°) as to walk normally on the level.

Several times they had cut their weight almost to zero to rise hand over hand up vertical rock faces. This had been the strangest experience of all, demanding complete faith in their equipment. To hang suspended in mid-air, apparently supported by nothing but a box of gently humming electronic gear, required a considerable effort of will. But after a few minutes, the sense of power and freedom overcame all fear; for here indeed was the realization of one of man’s oldest dreams.

A few weeks ago one of the library staff had found a line from an early twentieth-century poem that described their achievement perfectly: “To ride secure the cruel sky.” Not even birds had ever possessed such freedom of the third dimension; this was the real conquest of space. The Levitator would open up the mountains and the high places of the world, as a lifetime ago the aqualung had opened up the sea. Once these units had passed their tests and were mass-produced cheaply, every aspect of human civilization would be changed. Transport would be revolutionized. Space travel would be no more expensive than ordinary flying; all mankind would take to the air. What had happened a hundred years earlier with the invention of the automobile was only a mild foretaste of the staggering social and political changes that must now come.


In seconds, the wind had tossed them out over shadowed, empty blackness.

It was impossible to judge the depths beneath them; when Harper forced himself to glance down, he could see nothing. Though the wind seemed to be carrying him almost horizontally, he knew that he must be falling. His residual weight would be taking him downward at a quarter of the normal speed. But that would be ample; if they fell four thousand feet, it would be poor consolation to know that it would seem only one thousand.


He shouted across the wind: “Doctor! Use emergency lift!”

As he spoke, he fumbled for the seal on his control unit, tore it open, and pressed the button.

At once, the pack began to hum like a hive of angry bees. He felt the harness tugging at his body as it tried to drag him up into the sky, away from the invisible death below. The simple arithmetic of the Earth’s gravitational field blazed in his mind, as if written in letters of fire. One kilowatt could lift a hundred kilograms through a meter every second, and the packs could convert energy at a maximum rate of ten kilowatts — though they could not keep this up for more than a minute. So allowing for his initial weight reduction, he should lift at well over a hundred feet a second.


“I’m afraid you’re right — but I’m not sure we can make it, with this wind. Remember — we can’t go down as quickly as we can rise.”

That was true enough; the power-packs could be charged at only a tenth of their discharge rate. If they lost altitude and pumped gravitational energy back into them too fast, the cells would overheat and probably explode.


Five thousand feet above the ground, Harper began to expect the explosion at any moment. They were falling swiftly, but not swiftly enough; very soon they would have to decelerate, lest they hit at too high a speed. To make matters worse, they had completely miscalculated the air speed at ground level. That infernal, unpredictable wind was blowing a near-gale once more. They could see streamers of snow, torn from exposed ridges, waving like ghostly banners beneath them. While they had been moving with the wind, they were unaware of its power; now they must once again make the dangerous transition between stubborn rock and softly yielding sky.


“… still quite young when I realized that there was something wrong with Einstein’s Theory of Gravitation. In particular, there seemed to be a fallacy underlying the Principle of Equivalence. According to this, there is no way of distinguishing between the effects produced by gravitation and those of acceleration.

“But this is clearly false. One can create a uniform acceleration; but a uniform gravitational field is impossible, since it obeys an inverse square law, and therefore must vary even over quite short distances. So tests can easily be devised to distinguish between the two cases, and this made me wonder if …”

From The Cruel Sky by Arthur C. Clarke (1967)

Implications

THE GRAVITY WARS

     Tesla and Edison had the War of the Currents. There was the struggle over gaslights vs. electric bulbs. Then there was VHS vs. Betamax (for those of you old enough to remember videotaping). Mac and Microsoft still aren't talking. Wherever there's a way to build an invention there's likely to be several. But then at Low Stellar and Late Solar levels of technology you get the Gravity Wars!

     Gravity control in most settings makes space so much easier (meaning you can get to it and get killed quicker and cheaper.) Instead of using a honking huge rocket to reach orbit you can use a consumer friendly launch with a reasonable payload to fuel ratio. You just throw a switch and some of the Earth's (or other planet's) gravity is negated. Doing a space time sidestep you find yourself in orbit.

     This is going to piss off many powerful and wealthy people.

     Think about it. You're running a surface to orbit transport company and have invested in a laser launch system or space tower or even just a reusable rocket and launch pad. That's $$$$! Then along comes Pop Jenkins who builds an anti-grav car in his garage for GHU's sake! the cost of getting to orbit becomes the price of some current (pennies unless you're buying it in New York City). What would your reaction be? What would the headlines read?

     Local Inventor Dies in Garage Fire! Plucky Nephew and Brainy Neighbor Girl Feared Dead as Well! Page 2

     Maybe I'm being a little cynical. Maybe Pop Jenkins announces his discovery from orbit in his Solar Winnebago. The secret is out. What the hell do you do with your infrastructure? All those rockets and launch platforms are junk and all your revenue will dry up.

     Even worse, anti-gravity negates many reasons for going into space. A popular form form of MacGuffinite is microgravity manufacture. Now you can have microgravity or true zero gravity anywhere. So why even go to space?

     Wait! Your company has some long term contracts? Smart. Even if transport to orbit costs go from $10,000 a kilo to $0.25 you have contracts! Tough shit! Build an anti-grav transport with a loan or your savings. Use the increased profit from using it to retire your rocket fleet and build more anti-grav transports. Meanwhile delay the anti-grav revolution as much as you can!

     Legislation- You need to carefully monitor and license this new tech. Why you could drive a shuttle up to light speed and have it smack into a planet!

     Economics- If you need Element X to produce anti-grav then Element X becomes very expensive. Or in a rift on legislature processing and acquiring Element X requires special licenses.

     Health Concerns- the long term effects of artificial gravity on the human body are unknown! This needs further study!

     National Security- This new technology can threaten the nation and must be restricted to the military. This might even be a fair cop. Those planet smashing gigs are pretty scary.

     Slander! Anti-gravity is weakening the Earth's gravitational field/causing global warming/immorality and pulling meteors at your ship. Besides a little coriolis force never hurt anyone and keeps the coaster manufacturers in business. Those people have kids!

     More than likely the new tech will have drawbacks and limits. If it's very short ranged it might only be used to provide gravity on space stations and low gravity worlds to keep settlers from becoming anorexic beanpoles. Those beautiful rotating space stations and passenger sections are all suddenly out of fashion though.

     Perhaps anti-gravity is a  repulsive force instead of a shield or nullification. In that case it works when you have a planet or other massive body. The chemical rocket guys are out of business. The ion rocket cartel is still going strong for deep space missions. Just to further ruin Doc Jenkins' day, getting to orbit and being in an orbit are two different things. If anti-gravity lifts you a couple hundred klicks you are just hovering. Shut off the anti-grav and you fall. Worse, there are things moving in orbit that can hit you like little bits of dynamite. So an anti-grav might reduce the fuel and thrust needed to get to orbit but not negate it but Big Rocket stays in business.

     It does feel a little immoral though. Like you build a fusion reactor that uses hydrocarbons as fuel so Big Oil (boo!) stays in business or a super rocket fueled by tobacco.

From THE GRAVITY WARS by Rob Garitta (2016)

Paragravity

"Para" means "at or to one side of, beside, side by side". The idea is that "paragravity" means "ersatz-gravity" or "synthetic gravity". What we want to do is somehow generate 1 Terran gravity without the need of using 1 Terran mass. Preferably by something you can turn on and off with the flick of a switch, and that can be adjusted over a range of gravitational values.

Yes, the Starship Enterprise can have 1 gee of gravity inside if it carries on its belly a planet or black hole that has the same mass as Terra, but this ain't practical. For one thing it means the Enterprise's impulse drive would have to be capable of accelerating Planet Terra to the second star on the right straight on until morning. We want to somehow generate 1 gee of synthetic gravity will something as lightweight as floor decking.


The standard use for paragravity is to provide artificial gravity for crews in spacecraft without the need for cantankerous centrifuges. Artificial gravity is important, due to the severe health risks of free fall.

But if you use paragravity to lay the ship's decks at ninety degrees to the thrust axis like a passenger airplane, RocketCat will kick you in the gonads.

Paragravity can also be used for acceleration compensation, i.e., preventing rocket thrust from turning the crew into a thin layer of chunky salsa on the decks. The acceleration limit for astronauts is about 30 gees for no longer than ten minutes. And that is pushing it. However if the spacecraft is accelerating at 100 gees but the paragravity is pulling the astronauts upwards at 99 gees, the astronauts will experience a net force of only one gee downward. Just like on Terra.

Another use is to use paragravity to create attractor and pressor beams. While they are great for grappling spacecraft and cargo, they can also be adapted into a propulsion system that is almost a reactionless drive. Or a super-efficient mass driver rocket. Or a meteor repellor. Or a defensive repulsor field warding off missiles and other kinetic energy weapons. Or gravitic-confinement fusion power generator. Or super-efficient coilgun. Or super efficient particle beam weapon. Or otherwise weaponized.

Let's face it: paragravity is going to have a thousand and one uses. Just like electromagnetism. Remember when lasers were invented and the only application people could think of was a ray gun? Nowadays they are in everything: from surveying equipment, to laser gyroscopes, to making holograms, to optical tweezers, to scanning the bar-code on your groceries. Paragravity is going to be much like that.

THE RISEN EMPIRE

Scientifically speaking, the Larten Theory of Gravities was three decades outmoded, but it still served well enough for Navy textbooks. So, as far as Lieutenant-Commander Laurent Zai was concerned, there were four flavors of graviton: hard, easy, wicked, and lovely.

Hard Gravity was also called real gravity, because it could only be created by good old mass, and it was the only species to occur naturally. Thus fell to it the dirty and universal work of organizing solar systems, creating black holes, and making planets sticky.

The opposite of this workhorse was Easy Gravity, unrelated to mass save that easy gravity was hapless against a real gravity well. Hard gravitons ate easy ones for lunch. But in deep space, easy gravity was quite easy to make; only a fraction of a starship's energy was required to fill it with a single, easy gee. Easy gravity had a few problems, though. It was influenced by far-off bodies of mass in unpredictable ways, so even in the best starships the gee-field was riddled with microtides. That made it very hard to spin a coin in easy gee, and pendulum clocks, gyroscopes, and houses of cards were utterly untenable. Some humans found easy gee to be sickening, just as some couldn't stand even the largest ship on the calmest sea.

Wicked Gravity took up little room in the Navy's manuals. It was as cheap as easy gee, and stronger, but couldn't be controlled. It was often called chaotic gravity, its particles known as entropons. In the Rix Incursion, the enemy had used wicked gee as a devastating but short-range starship weapons. Exactly how these weapons worked was unclear—the supporting evidence was really a lack of evidence. Any damage that followed no understood pattern was labeled "wicked."

The Lovely particle was truly queen of the gravitons. Lovely gee was transparent to hard gravity, and thus when the two acted upon matter together it was with the simple arithmetic of vector addition. Lovely gravity was superbly easy to control; a single source could be split by quasi-lensing generators into whirling rivulets of force that pulled and pushed their separate ways like stray eddies of air around a tornado. A carefully programmed lovely generator could make a seemingly strewn pack of playing cards "fall" together into a neat stack. A stronger burst could tear a human to pieces in a second as if some invisible demon had whirled through the room, but leave the organs arranged by increments of mass on a nearby table. Unfortunately, a few million megawatts of power were necessary for any such display. Lovely gee was costly gee. Only Imperial pleasure craft, a few microscopic industrial applications, and the most exotic of military weapons used lovely generation.

From THE RISEN EMPIRE by Scott Westerfeld (2003)

Robert Forward

The late Dr. Robert L. Forward was a real physicist whose life's work was gravity research. He invented the Forward Mass Detector and had 18 patents to his name, including the Statite. He was the science fiction writer's friend, writing fiction himself and producting research on juicy SF projects like time travel, negative matter, antimatter rockets, and interstellar laser sail starships.

This means all of his material is not science fiction. It is real.

His most accessable book on these topics is the collection of science essays Indistinguishable from Magic.

Given his life's work, he does have a few things to say on the topic of gravity.

The main thing he said that stuck in my mind was about creating fields. He said modern technology uses electromagnetic fields everywhere, because they are so easy to create. All you have to do is take powerful electric charges (electrons) and move them near the speed of light along a path (as a current in a wire).

So in order to use gravitic fields, all you have to do is take powerful gravitational charges and move them near the speed of light along a path. Unfortunately "powerful gravitational charges" means white dwarf star material (1×109 kg/m3), neutronium (4×1017 kg/m3), or Primordial black holes (up to 1023 kg each). It takes titanic particle accelerators to move tiny subatomic particles near the speed of light, the mind boggles at what you'd need to accelerate something so dense that a teaspoon full would weigh as much as Mount Everest.

Since this is utterly beyond our current technology, we do not use gravitic fields.

Indistinguishable from Magic

(ed note: This is not science fiction, it is reality)

The Einstein Theory of Gravity is more complex than the two previous theories of gravity. In a simplified form it can be expressed as:

"A mass causes space to curve. Other masses move in that curved space."

In the Einstein view of gravity, mass does not cause gravity. Instead mass curves space and curved space causes gravity. A good analogy is to imagine a rubber sheet stretched over a frame. If you put a heavy ball bearing in the center of the rubber sheet, the weight of the ball would cause a curved depression. The mass of the heavy ball bearing has "curved" the rubber sheet "space". If you then drop a tiny marble on the curved rubber sheet, the marble would immediately start to roll toward the center as if the large ball were attracting it. But there is no direct attraction between the ball bearing and the marble, the ball bearing is curving the rubber sheet and the marble is responding to the curvature of the rubber (and the gravity of the Earth). If the marble were tossed properly into the curved depression in the rubber sheet, it would go into an "orbit" around the heavy ball bearing at the center.


Because the Einstein Theory of Gravity is more complex than the Ug or Newton theories, it can give us more handles by which we can control gravity. There are at least two ways that we can use the Einstein Theory of Gravity to negate the gravity field of the Earth. There are also two ways we can use the Einstein Theory of Gravity to make a mass push instead of pull.


(Method One: Special Relativity: Protational Field)

In the scientific studies of electricity, it has been found that electricity and magnetism are related. If you change or move electricity, you make magnetism, and if you change or move magnetism, you make electricity again. This transformation between electricity and magnetism is used to make your automobile run. The electricity in your car battery is only twelve volts, not strong enough to run your spark plugs. This low voltage electricity is used to create magnetism in the spark coil. The magnetism temporarily stored in the coil is then released very rapidly when the points open. This rapidly changing magnetic field then generates the powerful, high-voltage sparks that are used by the spark plugs. By using the magnetic field as an intermediate step, the automotive engineers have found a way to convert weak electric forces into strong electric forces.

The Einstein Theory of Gravity says that gravity behaves the same way as electricity. If you take a mass and the gravity field that surrounds it, and move the mass very rapidly, you can create a new field, the gravitational equivalent of magnetism. It is not magnetism, but a completely new field (Protational Field). If you can then cause that new field to change, then you can create a stronger gravity field than you started with. More importantly, that stronger gravity field can be made to appear at a place where there is no mass, and can be made either attractive or repulsive.

Conceptually, there are a number of ways that such a gravity machine could be made. One idea is to roll up some hollow pipe to form a long coil, like the curly cord on a telephone. [See Figure 10.] We then bend the long coil around until the two ends meet to form a curly closed ring.

If the pipes are filled with massive liquid and the liquid is moved back and forth in the pipes rapidly enough, then an alternating push-pull gravity field will be generated at the center of the ring. If the machine was big enough, and the liquid was dense enough and moving fast enough, then we would have a gravity catapult that could launch and retrieve space ships by its gravity repulsion and attraction.

How big? How dense? How fast? Unfortunately, the machine has to be as big as the distance over which you want the gravity effects to operate (i.e., the range of the gravity field is about equal to the diameter of the coil). The liquid has to be as dense or denser than white-dwarf-star material (1×109 kg/m3), and the speed of the flow has to be so high that the ultradense liquid will approach the speed of light in a few milliseconds (implying that the energy requirements will be astronomical, and maybe implying that the gravity field can only be generated for a few milliseconds).

I am afraid that it will be some time before we have all that gravitational technology well in hand. But we do have the theory needed to design our gravity catapult, and some time in the long distant future we will have college classes full of bright students taking their first course in Gravitational Engineering, studying the turbulent flow in ultradense matter and producing more and more efficient designs for the gravitational attractor and repulsor beam intensities to minimize passenger discomfort during the launch or retrieval of an interstellar passenger liner.


(Method Two: General Relativity: Frame Dragging)

The Einstein Theory of Gravity can give us yet another way to control gravity. One of the strangest facets of the Einstein Theory of Gravity is the concept of curved space. The method by which a massive object causes a curvature in space is difficult to really comprehend. It is as if the mass had grabbed hold of space and pulled the space into it. This grip of mass on space is still maintained when the mass is moving. The space seems to move along with the mass. This effect, called the "dragging of the space-time coordinate frame", is the basis for another future magic type of antigravity machine.

If you are near a rapidly moving dense mass, you will find yourself "dragged" along in the direction of the moving mass. One could envision a "lift" shaft, lined with pipes full of rapidly flowing ultradense fluid that wafts you rapidly up to the top of a mile-high building. But more likely this "drag" effect will be used in space as a gravity catapult for shipping purposes within the Solar System. This machine would again be in the form of a ring of ultradense matter, but this time the ring would be uniformly whirling from inside-out, like a gigantic smoke-ring.

If a spaceship entered such a toroidal gravity catapult through the hole from one side, it would be expelled out the other side of the hole with a greatly increased velocity. If the spaceship were falling in toward the Sun from the asteroid belt with a high velocity, it would be gently stopped in Earth orbit by threading the torus in the opposite direction. Since the forces on the spaceship during acceleration and deceleration are gravitational forces which act equally on every atom in the ship, all the atoms in the spacecraft are stopped at the same rate and at the same time. So, even though the accelerations and decelerations can be at rates equivalent to hundreds of Earth gravities, the passengers on those spacecraft will not even have to turn in their martini glasses for "landing" in the Earth-Moon system, much less buckle their seatbelts, stow their overhead luggage, raise their seatbacks, and secure their tables.

From Indistinguishable from Magic by Robert Forward (1995)

Le Sage's Repulsive Gravity

Le Sage's 1748 theory of gravitation is based on the non-intuitive idea that gravity is a repulsive, not attractive force. The force can be shielded by matter.

How does this work?

Imagine yourself far from any planet. Your body is bombarded by repulsive gravity from the entire universe around you. Since all the repulsion pushing you to the left is balanced by the repulsion pushing you to the right, the net result in the left-right axis is zero. The same applies in any other axis, so if you were in the depths of space you'd experience zero gravitational acceleration.

Now imagine that Terra is below you. Suddenly the gravitational repulsion of the universe coming from below is diminished by the shielding provided by the matter of Terra. The repulsion coming from above is now stronger than the repulsion from below. The net result is one Terran gravity of acceleration, pushing you in the direction of Terra.

Alas, Le Sage's theory is pretty much discredited nowadays, because it makes predictions that do not occur in the real world.

For one thing, it assume a select frame of reference, that is, the repulsive gravity particles are evenly distributed in all directions. Unfortunately, if the object starts to move in relation to that frame, it will be hit with more gravity particles in head-on collisions than in rear-end collisions. The effect is that everything will move like it is embedded in tar or other thick liquid. Which doesn't happen in the real world.

Recall Not Earth

C.C. MacApp's nearly forgotten and definitely underrated novel Recall Not Earth actually uses Le Sage's Repulsive Gravity theory.

In the novel, scientists invent a "gravity shield" where by adjusting a knob the shield will reduce the repulsion effect from the universe to any desired degree. Starships incorporate an array of gravity shields on their hulls facing in all directions. By turning on the appropriate shield, the starship can instantly accelerate in the appropriate direction.

The best part is since gravitational acceleration affects all atoms equally (starship and crew), the crew does not feel the acceleration. The ship can be accelerating at 100 gees but the crew is still floating around inside. The reason this does not happen with a rocket is because the rocket acceleration affects only the atoms of the rocket engine, which pushes on the thrust frame of the spacecraft, which pushes on the spacecraft's habitat module, which pushes on the bodies of the crew, who get mashed into their acceleration couches.

This technique is kind of in a gray area between antigravity and paragravity, since is uses gravity shields (antigravity) to generate gravity (paragravity). I'm filing it under paragravity because effects are more important than causes. You quickly learn that if you play the Hero System RPG. For instance, in the Hero System, a given "power's" cause can be a laser beam, bullet, spray of burning liquid, hypnotic stigmata, thown rock, poison dart, homing missile, boomerange, arrow, swarm of angry hornets or psychokinetic thrust. But the imporant part is the effect: in this case "energy blast", defined as "inflicting damage on your opponent at range". The cause is more or less window dressing.

So the important part is the effect: generating a gravity field for acceleration. The fact that it is done by using gravity shields in a Le Sage universe is window dressing. So I am filing this under "paragravity".

The Chelki, under the direction of a Full Male who was second in command here on Akiel, had done an excellent job of refitting and conditioning the old Vul ship (and the eight smaller ones as well). The grav drive was tuned so precisely that John could lift the sixty-thousand-ton vessel a half-inch from the concrete floor of the vast grotto where she lay hidden and set her down again in increments of a quarter-inch, all without the slightest jar or sensation of inertia. Such tuning was important; in combat, a ship's computers (to say nothing of her flesh-and-blood pilots) might demand that she halt instantly, from a velocity of an appreciable fraction of light-speed, or dart away just as instantly on a different course. The gravs had to act upon every component (including passengers) at the same exact moment and with the same force, else she'd be torn apart or her passengers squashed by acceleration.

It was peculiar, he mused, how so many species (of humanoids, at least) discovered the gray drive (and related null drive) at about the same point in their technological development, almost as if it were programmed into the course of science.


Mankind had developed the grav drive within a reasonable time after two monumental discoveries: first, that gravity was a push, not a pull; second, that the push could be screened off by a sheet of any of several special alloys under the influence of certain force fields distantly related to electricity.

This is why a push had always been mistaken for a pull: one of the basic facts of the "normal" universe is that all of space — every cubic centimeter of it, from all directions and all distances up to (and perhaps including) whatever "infinity" exists — repels matter. It repels matter ceaselessly, as if trying to squeeze it out of existence.

But, as if there were some conscious community of mutual assistance, each particle of matter shields every other particle against this push by space. That is as if one opaque ball cast a shadow upon another. And, while space shoves against matter from all directions, there is nothing correlated in this shove; no transverse action or other baffling peculiarity, as with the front of a light wave. Each discrete quantum of space aims a determined straight-line punch continuously at every particle, as if no other quantum of space existed. The punches do not get tangled up or canceled out or deflected. They do reinforce each other, but only in an additive straight-line way.

In one thing the old physics was partly correct: the force of a push does vary inversely with distance, but not in. direct ratio or in the ratio of squares or cubes. The ratio, which can be measured with some accuracy by an ingenious experiment (which, incidentally, led to the invention of the mass detector), has something to do with the number of dimensions that exist in "normal" space. And that is not a matter to discuss casually.

So, the situation exists that every particle of matter is being shoved at from every direction, but is shielded to some tiny extent by every other particle. But the mutual shielding of two particles is only along the straight line joining them. Therefore, what can two particles do but move toward each other? Along that one line, the pressure upon them is lessened by a very small fraction.

Naturally, two electrons, for instance, separated by a distance of several thousand light-years, would take a very long time to come together (not even considering that they were not the only two particles in space). But time is long, and space is patient. Hence particles become atoms, and atoms molecules, and molecules solid masses (if one can stomach that latter inexactitude).

There are counterforces that prevent space from squeezing all matter into one inconceivable ball. One such force is inertia ("centrifugal force" in the case of two particles or rocks or stars orbiting each other). A second such force is the natural repulsion between particles having like charges: electron repelling electron; positron repellng positron. Another is the pressure of radiant energy, as in the terrific effort of a hot star to explode. And there are others not describable in such simple terms.

So, when a considerable mass has been pushed together, it has a considerable effect of shielding against space. For instance, a man standing upon a planet is partly shielded from almost one hundred and eighty degrees of space. The other half of space pushes him against the planet. Semi-primitive man, with his reasonable but unreliable tendency to see things as they appear, called this effect "gravity" and thought it was a pull by the planet. Null-age man, with his perhaps not reasonable propensity for the complex (fore­shadowed, maybe, by such utterly improbable developments as the internal-combustion engine), seized upon the true nature of "gravity" and put it to work (as had, long before, various other equally antipractical, venturesome, stubborn species).


All particles of matter act as natural shields against the push of space, but with limited efficiency. Artificial shields can be made that perform, at optimum, with awesome efficiency. Thus, if a person standing on Earth held a shield above his head and activated it, he would be propelled violently into the air by the residual "space push" penetrating the planet and shoving at him from below. So would a cone of soil (though, since the shielding falls off with distance from the shield, and also because of the geometry of the situation, the cone would not be very long).

The residual push penetrating Earth could be, and was, calculated at approximately two hundred and fifteen gees, and from that (assuming various things) it was clear that Earth, in effect, screened off slightly less than one-half of one percent of the push from half of space. Or: maximum theoretical "gravity," anywhere, was two hundred and sixteen gees.

John had never found that theory particularly reassuring. Two hundred gees, or considerably less, could make puree of a man!

(Note: it is possible to build a shield that will stop the push from one direction only. That is desirable in self-propelled missiles, in certain instruments, and in special tools.)

(Further note: due to certain peculiar properties of space and of shields, it is possible to design the latter to produce a "lee" of a particular shape: conical, spreading, parallel beam, and so forth. For instance, the use of high shielding and a long tapering cone, combined with the one-way effect, gives the weapon called the "rupter" — intense "push" is applied to the target or a small zone of it, and when the push is applied and interrupted and reapplied at a suitable rate, the target can be shaken to pieces. Rupters have ranges limited, in practice, to a few miles. Another example of special shields is in arranging "artificial gravity" within a ship. Without artificial gravity, passengers would suffer various discomforts, some fatal.)


Obviously, if you build a shield into or onto a structurally strong container, and activate it, the whole container will be urged, to some degree, in the direction of the shield. If you take a cylindrical tank of, say, one thousand gallons capacity, put an airtight hatch in it, and fit a shield flat upon one end, you have the fundamentals of a spaceship. Such a ship, if the shield is designed for variable and closely controlled input of power, can rise slowly and gently from a planet's surface without pulling a divot of the planet with it.

Commonly, ships are cylinders of high-strength steel, less than twice as long as their diameters, with shields at either end (occupying the full cross section as nearly as possible) and smaller auxiliary plates at various points of the cylindrical walls (arid sometimes others distributed along cross sections between the two ends). Application of power to any shield or combination of shields is controlled by a special computer, which is usually in turn controlled by the main computer, since manual control might be jerky and dangerous. A ship in space can. achieve startling acceleration, because passengers arc accelerated by the "space push" along with the rest of the ship. Anomalies exist, off the axis of the ship, and at the rear; but these are canceled or counteracted by properly designed and adjusted auxiliary plates. A combat ship can dart to the sides, too, though not with the acceleration it can achieve along its axis. Due to various limitations of structural materials, power feed, passenger reaction, etc., acceleration (in practice) is limited to about seventeen gees (in normal space, that is). Seventeen gees is not enough to dodge a swarm of computer-coordinated missiles, but it can make them work.


The null drive is something else again. Very soon after development of the new grav-drive technology and science, there were several breakthroughs in understanding the nature of space itself.

The real savants claimed that there must be quite a number of "spaces," each positioned to the others in such a way that time was involved, along with various dimensions. John Braysen was willing to accept that without being harangued at length about it.

There appeared to be no immediate prospect of switching from "normal" space (that is, "our" continuum) to any of the other spaces. However, there was some kind of limbo, or state of existence that was none of the spaces, into which an object could be shifted. The way this was done was awesome: the object (a ship and passengers, for instance) had to have every particle charged with a kind of energy related to, but not identical with, the field that produced gravity shielding. When this charge reached a critical intensity, a little extra surge caused it (to all exterior observations) to cease to exist in normal space. Passengers felt only an instant of odd disorientation.

In this strange limbo (called "null"), ordinary gray drives could accelerate the "ghost" of the ship at a rate fantastically greater than in normal space. That hull acceleration didn't require exceptional power, but to attain readiness for null did. Conduits to feed that power without melting had a practical limitation: the best rate of charging that Earth's or any other known technology could achieve was a little over four minutes.

So you couldn't "break out" of null and reenter immediately.

One of the puzzling things was that the tremendous power thus fed into matter could be discharged so instantly with very little detectable "spill." A little static, a momentary mild blue glow, were the only phenomena yet detected.

Travel in null was not instantaneous. There was a limit of some sort; and, to simplify as much as possible the terrible problems of navigation, the apparatus was standardized to fit some little-understood natural velocity that approximated four hundred and ninety light-years per hour. Usually a ship going, say, one hundred light-years, could judge its breakout point to within one-tenth light-year of its target. From there you made an additional short null hop or hops, like a golfer sinking a putt.

From Recall Not Earth by C.C. MacApp (1970)

Eldraeverse

Handwavium: Paragravity

Okay, let’s talk about paragravity.

First up, a note on nomenclature. Paragravity is one of the two things that an Imperial habtech might be referring to when they talk about artificial gravity, the other being spin gravity. Unlike spin gravity, which is “powered” by good old centrifugal force, paragravity is produced by ontotechnological space magic that does wonderfully complex things involving information physics and grand unified theories and other such things to poke the universe in exactly the right way – basically, one branch of the mass-inertia-and-momentum manipulating vector control.

Which is to say that it is produced by gravity rotors, suitcase-sized boxes with a power connector, a ‘weave connector, and a thermal management connector on the outside, filled with solid-state hardware that is a proprietary product of Mariseth Gravitics, ICC. And into whose internal workings we shall thus respectfully avoid going.

What we’re talking about here is how they work on the outside.

The field of paragravity (the gravity envelope) can only be created between two gravity rotors of opposed polarity. That gets you a straight field (with perhaps some convex distortion at the edges) between the two, which imposes a force functionally identical to mass-generated gravity (i.e., affecting all atoms, etc., equally) on everything with mass inside it. This creates a consistent down direction towards what, for the sake of designation, we shall call the “positive” rotors.

(You have to have a closed envelope, and can’t operate an unpaired gravity rotor even if you wanted to: since the universe is functionally infinite in whatever direction you’re pointing it, energy requirements for the half-field head asymptotically for infinity, at which point the circuit breakers save you from a messy ‘splosion.)

Both momentum and energy are conserved, as they would have to be.

The former is the reason that you gravity rotors should be bolted firmly to the structure of the hab; whatever force they exert is, per Callaneth’s Lemma (or Newton’s Third Law, whatever name you prefer), reciprocally exerted too, half to each rotor in the pair.

While difficult to arrange even deliberately, this does imply that if you can get enough mass in one spot and move it just right, you can get the gravity rotors to tear themselves free and leap in the appropriate reciprocal direction.

With regard to the latter: it takes energy to establish the gravity envelope, but once it’s up and running, maintaining it takes only minimal energy physically speaking. (I.e., it still consumes quite a bit of energy in the rotor while it’s up and going, because rooting the universe ain’t cheap; that energy just doesn’t go into the envelope. It’s this waste that makes paragravity a real expensive thing to run.)

That, however, is only true so long as nothing is moving within it. Falling objects, moving in the down direction of the envelope, take energy from the envelope as they gain kinetic energy. (Likewise, when you lift an object within the envelope against its downforce, that pushes energy into the envelope, which is a surge effect that the hardware has to cope with. Alas, it’s not something that can be harvested in the majority of applications.) You could call this paragravitational potential energy if you like, since it sits in essentially the same place in the relevant equations.

While it takes the rotors a little while to initialize from a cold start (although some of this time is self-diagnostics and the like), once up and running, though, you can change the parameters of the gravity envelope very quickly; and you can generate pretty much any amount of gravity you want up to their capacity so long as you’re willing to spend the energy (which varies proportionately) needed to do it.

This is what lets you use the exact same technology for inertial damping; you just have appropriately oriented gravity rotors cancel out your engine thrust inside the starship – while bearing in mind that this will have certain effects on your structural load. (Likewise, you can use them when grounded – but since they don’t block planetary gravity, if you want 1G in the cabin when landed on a 3G world, you will actually be running the paragravity system at -2G.)

The drawback, however, is that the same lack of “inertia” in operation that lets you change your gravity quickly means that they fail equally quickly – and shut down essentially instantly if the power fails, just like an electromagnet’s field collapses – so failing to keep up maintenance schedules may mean being abruptly smashed to the deck with a force of twelve gravities! Caveat engineer.

Cities in Flight

James Blish's classic Cities in Flight series have paragravity machines called Dillon-Wagoner Graviton Polarity Generators (commonly called "Spindizzies"). They use the (now discredited) Blackett effect aka "gravitational magnetism". Control the spin and you control the gravity. In the novel it has lovingly constructed baffle-gab explanations with just enough real science to stub your toe on and fool you into thinking it is actually plausible. The joker in the deck is that the efficiency of a spindizzy goes up as the mass of the spacecraft increases. The novels center around entire cities uprooted and turned into starships via spindizzies, turning into interstellar migrant laborers escaping the economic collapse of Terra. In the latter novels, entire planets are moved with spindizzies.

Cities in Flight

“Sure. It’s a thing called the Blackett equation. Deals with a possible relationship between electron-spin and magnetic moment. I understand Dirac did some work on that, too. There’s a G in the equation, and with one simple algebraic manipulation you can isolate the G on one side of the equals-sign, and all the other elements on the other.” (Not a crackpot notion this time. Real scientists have been interested in it. There’s math to go with it.)

“Status?” (Why was it never followed, then?)

“The original equation is about status seven, but there’s no way anybody knows that it could be subjected to an operational test. The manipulated equation is called the Locke Derivation, and our boys say that a little dimensional analysis will show that it’s wrong; but they’re not entirely sure. However, it is subject to an operational test if we want to pay for it, where the original Blackett formula isn’t.” (Nobody’s sure what it means yet. It may mean nothing. It would cost a hell of a lot to find out.)

“Do we have the facilities?” (Just how much?)

“Only the beginnings.” (About four billion dollars, Bliss.)

“Conservatively?” (Why so much?)

“Yes. Field strength again.”

(That was shorthand for the only problem that mattered, in the long run, if you wanted to work with gravity. Whether you thought of it, like Newton, as a force, or like Faraday as a field, or like Einstein as a condition in space, gravity was incredibly weak. It was so weak that, although theoretically it was a property of every bit of matter in the universe no matter how small, it could not be worked with in the laboratory. Two magnetized needles will rush toward each other over a distance as great as an inch; so will two balls of pith as small as peas if they bear opposite electrical charges. Two ceramet magnets no bigger than doughnuts can be so strongly charged that it is impossible to push them together by hand when their like poles are opposed, and impossible for a strong man to hold them apart when their unlike poles approach each other. Two spheres of metal of any size, if they bear opposite electrical charges, will mate in a fat spark across the insulating air, if there is no other way that they can neutralize each other.

(But gravity — theoretically one in kind with electricity and magnetism — cannot be charged on to any object. It produces no sparks. There is no such thing as an insulation against it — a di-gravitic. It remains beyond detection as a force, between bodies as small as peas or doughnuts. Two objects as huge as skyscrapers and as massive as lead will take centuries, to crawl into the same bed over a foot of distance, if nothing but their mutual gravitational attraction is drawing them together; even love is faster than that. Even a ball of rock eight thousand miles in diameter — the Earth — has a gravitational field too weak to prevent one single man from pole-vaulting away from it to more than four times his own height, driven by no opposing force but that of his spasming muscles.)


Now all this seemed to me to have nothing to do at all with gravity, and I said so to my team chief, who brought the thing to my attention. But I was wrong (I suppose you’re already ahead of me by now). Another man, Prof. P. M. S. Blackett, whose name was even familiar to me, had pointed out the relationship. Suppose, Blackett said (I am copying from my notes now), we let P be magnetic moment, or what I have to think of as the leverage effect of a magnet — the product of the-strength of the charge times the distance between the poles. Let U be angular momentum — rotation to a slob like me; angular speed times moment of inertia to you. Then if C is the velocity of light, and G is the acceleration of gravity (and they always are in equations like this, I’m told), then:

P = BG½U / 2C

(B is supposed to be a constant amounting to about 0.25. Don’t ask me why.)

Admittedly this was all speculative; there would be no way to test it, except on another planet with a stronger magnetic field than Earth’s — preferably about a hundred times as strong. The closest we could come to that would be Jupiter, where the speed of rotation is about 25,000 miles an hour at the equator — and that was obviously out of the question.

Or was it? I confess that I never thought of using Jupiter, except in wish-fulfillment daydreams, until this matter of the Locke Derivation came up. It seems that by a simple algebraic manipulation, you can stick G on one side of the equation, and all the other terms on the other, and come up with this:

G = (2PC / BU)2

To test that, you need a gravitational field little more than twice the strength of Earth’s. And there, of course, is Jupiter again. None of my experts would give the notion a nickel — they said, among other things, that nobody even knew who Locke was, which is true, and that his algebraic trick wouldn’t stand up under dimensional analysis, which turned out to be true — but irrelevant. (We did have to monkey with it a little after the experimental results were in.) What counted was that we could make a practical use of this relationship.

Once we tried that, I should add, we were astonished at the accompanying effects: the abolition of the Lorentz-Fitzgerald relationship inside the field, the intolerance of the field itself to matter outside its influence, and so on; not only at their occurring at all — the formula doesn’t predict them — but at their order of magnitude. I’m told that when this thing gets out, dimensional analysis isn’t the only scholium that’s going to have to be revamped. It’s going to be the greatest headache for physicists since the Einstein theory; I don’t know whether you’ll relish this premonitory twinge or not.


"But the one job that only the Bridge could do was that of confirming, or throwing out, the Blackett-Dirac equations.”

“Which are—?”

“They show a relationship between magnetism and the spinning of a massive body — that much is the Dirac part of it. The Blackett Equation seemed to show that the same formula also applied to gravity; it says G equals (2PC / BU)2, where C is the velocity of light, P is magnetic moment, and U is angular momentum. B is an uncertainty correction, a constant which amounts to 0.25.

“If the figures we collected on the magnetic field strength of Jupiter forced us to retire the equations, then none of the rest of the information we’ve gotten from the Bridge would have been worth the money we spent to get it. On the other hand, Jupiter was the only body in the solar system available to us which was big enough in all relevant respects to make it possible for us to test those equations at all. They involve quantities of infinitesimal orders of magnitudes.

“And the figures showed that Dirac was right. They also show that Blackett was right. Both magnetism and gravity are phenomena of rotation.

“I won’t bother to trace the succeeding steps, because I think you can work them out for yourself. It’s enough to say that there’s a drive-generator on board this ship which is the complete and final justification of all the hell you people on the Bridge have been put through. The gadget has a long technical name — The Dillon-Wagoner gravitron polarity generator, a name which I loathe for obvious reasons — but the technies who tend it have already nicknamed it the spindizzy, because of what it does to the magnetic moment of any atom — any atom within its field.

“While it’s in operation, it absolutely refuses to notice any atom outside its own influence. Furthermore, it will notice no other strain or influence which holds good beyond the borders of that field. It’s so snooty that it has to be stopped down to almost nothing when it’s brought close to a planet, or it won’t let you land. But in deep space well, it’s impervious to meteors and such trash, of course; it’s impervious to gravity; and it hasn’t the faintest interest in any legislation about top speed limits. It moves in its own continuum, not in the general frame.”

“You’re kidding.” Helmuth said.

“Am I, now? This ship came to Ganymede directly from Earth. It did it in a little under two hours, counting maneuvring time. That means that most of the way we made about 55,000 miles per second — with the spindizzy drawing less than five watts of power out of three ordinary No. 6 dry cells.”


“The fundamental equation of the Blackett-Dirac scholium reads as follows:

P = BG½U / 2C

where P is magnetic moment, U is angular momentum, C and G have their usual values, and B is a constant with the value 0.25 approximately. A first transform of this identity gives:

G = (2PC / BU)2

which is the usual shorthand form of the primary spindizzy equation, called the Locke Derivation. Blackett, Dirac and Locke all assumed that it would hold true for large bodies, such as gas-giant planets and suns. Show on the blackboard by dimensional analysis why this assumption is invalid.”

As far as Chris was concerned, the answer could have been much more simply arrived at; Dr. Braziller could just have told him that this relationship between gravitation and the spin of a body applied only to electrons and other submicroscopic objects, and disappeared, for all practical purposes, in the world of the macrocosm; but that was not her way. Had she only told him that, it would have come into his mind as a fact like any other fact — for instance, like the facts that the memory cells of the City Fathers were constantly pouring into his ears and eyes — but by her lights he would not have understood it. She wanted him to repeat not only the original reasoning of Blackest, Dirac and Locke, but to see for himself, not just because she told him so, where they had gone astray, and hence why a natural law which had first been proposed in the gas-lit, almost prehistoric year of 1891, and was precisely formulated as the Lande Factor in 1940, nevertheless failed to lift so much as a grain of sand off the Earth until the year 2019.

From Cities in Flight by James Blish ()

Tales Of The Flying Mountains

In Poul Anderson's Tales of the Flying Mountains, the solar system is opened up by the discovery of "gyrogravitics" (geegees). Mr. Anderson was probably inspired by Blish's spindizzies, since "spin" and "gyro" are related terms. In the stories, it started off as the director of NASA investigating a crack-pot theory as busy-work in a desperate effort to keep NASA alive until the director could retire. The director was pretty sure it was a dead end, but didn't care since it would keep Congress from killing NASA for a few years. By the time the research crashed and burned the director expected to be safely retired.

Then the Soviet space agency started studying it (probably for the same reason). This sparked an arms race, and the money poured in. The nations could not afford to have a gyrogravitics gap! Amazingly, it actually resulted in a working space drive and a tractor beam. The solar system was inadvertently opened up by two bureaucrats just trying to hang on to their jobs.

Amusingly enough, the tractor beam obeyed a super-duper inverse square law: it had a range of only a few centimeters. It worked, but the ship with the tractor had to be practically in contact with the object it was moving.

"I'm delighted to explain. Have you heard of gyrogravitics?"

Stanhope shook his knaggy head. Carter of Virginia said, slowly, "Has to do with atomic theory, doesn't it."

"That's right," Harleman answered. "I don't claim to follow the mathematics myself, but I've had scientists give me a lay explanation. It grew out of the effort to reconcile relativity and quantum mechanics. Those two branches of physics, both indispensable, were at odds on certain fundamental questions. Is nature or is nature not deterministic—describable by differential equations? Well, you may have read how Einstein once declared he couldn't believe that God plays dice with the world, while Heisenberg thought cause-and-effect was nothing but the statistics of large numbers, and Bohr suggested in his complementarity principle that both views might be true. Later, building on the work of such as Dyson and Feinberg—" Harleman saw them drifting away again. Damn! I spent too much time with Emett last night. That jargon of his soaked into my skin.

"Well, the point is, gentlemen," he said, "in the newest theory, matter and energy are described by their properties from the equations, equations like those of a rotating force-field. Including gravitation."

Carter jerked to an upright sitting position. "Wait a minute!" he exclaimed. "You aren't leading up to antigravity, are you? I happen to know what the Air Force has been doing in that line for the past fifty years. It's no secret they've drawn absolute blanks. Antigravity belongs with witches on broomsticks. I could reach Mars easier by ... by astral projection."

"Not antigravity, sir," Harleman told him. "Gyrogravitics."

"A change of labels doesn't—"

"Please sir. I've had some most interesting discussions with a Mr. Quentin Emett. Some of you may have heard of him: an independent investigator—"

"Means he hasn't got his Ph.D.," Thomasson said grimly.

"Well, yes, he does happen to lack a union card," Harleman replied.


"Mr. Emett's ideas are unorthodox, true. He proposes to develop a generator which, by means of nuclear resonance rotations, will create fields that we can call gravitational, or antigravitational, or pseudogravitational, or whatever we like. I think 'gyrogravitic' is probably the best word, though if we can get this work authorized, the R and D effort should have a more suitable name such as, for example, Project Dyna-Thrust."

Carter sneered. "And you'll make your spaceships weightless and float them right off Earth, eh?"

"No, sir." Emett had carefully rehearsed Harleman. "Conservation of energy and momentum are not violated. In effect, a gyrogravitic drive should react against the entire mass of the ambient universe. You'll still need power to rise, or accelerate, or maneuver in any other way. But it'll be minimum power; you won't be throwing energy out in exhaust gases. The power plant can be minimal too; since you can hover free, or nearly free, you don't need a huge motor to raise you as fast as possible. Any energy source will do—fuel cells, batteries, nuclear reactors, I suppose even steam engines—though no doubt as a side benefit we'll get small, portable fusion plants. A ship like this would be almost one hundred percent efficient, silent, unpolluting, economical to build, capable of going anywhere. The capability would derive in part from interior gyrogravitic fields. These would provide weight though the ship be in free fall, cushion against pressure when it accelerates, ward off solar-storm particles, meteoroids, and similar hazards." Harleman ratcheted up his enthusiasm. "In short, gyrogravitlcs can give us the whole Solar System."

"So can sorcery," Carter grumbled, "if only we can discover how to make it work."

Harleman talked nominally to them all, actually to Stanhope: "My belief is, the United States can't write off its huge investment in NASA, and in any case, positively not overnight. Research must go on. One advantage of Mr. Emett's proposal is its modest cost. If we establish Project Dyna-Thrust, it should be feasible to discontinue various other activities and thus reduce the total budget—without feeling that we have broken faith with our predecessors or abandoned the Endless Frontier of Science."

From "Nothing Succeeds Like Failure" collected in Tales of the Flying Mountains by Poul Anderson (1970)

Carrot On A Stick

This is a surprisingly common piece of handwavium found in science fiction to use paragravity for spacecraft propulsion. The word "handwavium" is a clue that this is utter bilge.

Remember the old "carrot on a stick" trick? You sit on a horse or donkey. You use a stick to dangle a carrot in front of the animal's nose. It then walks forward trying to get the carrot. Since it never gets any closer, it keeps on walking until it collapses. TV tropes calls this "Motivation on a Stick."

The idea is your spacecraft (the donkey) is equipped with a magic handwavium paragravity device (the stick) that creates a bodiless point source of gravity (the carrot) a couple of meters in front of your spacecraft's nose. With lots of gravity. The ship and everything in it falls into the point gravity source. But this includes the paragravity gizmo. Which means the point gravity source moves forward, exactly like the carrot is moved forward by the stick. The ship keeps accelerating until the paragravity gizmo runs out of electricity.

The advantages is that the ship and everything is being accelerated by the force of gravity, which acts on all the atoms equally. Meaning that the ship can accelerate at 500 gees without turning the crew into a thin layer of red chunky salsa all over the deck. Heck, at 500 gees the crew is still floating in free fall.


You can also use this to alter your vector. On your donkey, you can make it turn to the right by manipulating the stick so the carrot moves to the right. This allows you to steer the donkey. In a similar manner, you can use the paragravity gizmo to change the position of the point gravity source. Make it appear to starboard, and the ship will start accelerating in that direction. Make it appear in the opposite direction of the ship's current vector for deceleration.


The disadvantage is it won't work.

First off there is the sticky problem of the "stick", meaning how do you push the point gravity source forwards so the ship does not ram it? If you push it forwards with 500 gees, Newton will insist that the reaction pushes the ship backwards with 500 gees. So the net result is the ship just sit there.

If instead of a point gravity source you are using a physical paragravity machine, the machine will be attracted to the ship with the same force as the ship will be attracted to the machine. They will ram each other. But if you mount the machine on a framework attached to the ship's nose to prevent ramming, then the machine's gravity will attract the ship with a force of X while the machine's motion transmitted through the framework will push back with a force of -X, and the next motion will be X - X = 0.

This is similar to that tired old gag of propelling a sailboat by blowing on a sail with an electric fan. The wind from the fan will hit the sail, the action pushing the boat forward. Alas, the reaction on the fan from expelling the wind will move the fan backwards. If the fan is bolted to the sailboat, the action and the reaction will cancel out. Net motion of zero. If the fan is not bolted to the boat, it will go flying backwards and fall off the aft end. (Airboats do not count since the fan is not blowing on a sail attached to the boat, it is purely using the reaction of expelling the air)

Common hand-waves desperately used at this point are either [a] bodiless point sources of gravity have no inertia or [b] the gravity point is created and held in existence only long enough to yank the ship. Then a new point is created a bit further ahead. The ship moves forward in stroboscopic jerks.

But the major problem is that while paragravity is technically unobtanium, all the plausible techniques have the created gravity field centered inside the gizmo. Not at some distance away.

The entire drive comes under the heading of pulling yourself up by your own bootstraps. Much in the same way Baron Munchausen lifted himself and his horse out of the swamp and into the air, by pulling upwards on his pigtail.


Be that as is may, there are quite a few science fiction novels that use this contraption.

Invaders from the Infinite by John W. Campbell jr. (1961)
The attractive ray makes a section of the mesh of the space-time continuum emit gravity waves. This can be used to move a ship, asteorid, planet, star, or whatever you have the energy for. Since the gravity is coming from the mesh of space, the attractive ray violates Newton's law of action and reaction. Total handwavium.
The Tar-Aiym Krang by Alan Dean Foster (1972)
Kurita-Kita gravity drive ships look like a balloon stuck on the handle of a plumber's helper. The "suction cup" is the ship's nose, the balloon is to the rear. The suction cup is the gravity field generator, the balloon is the habitat and payload module. It operates like a standard carrot-on-a-stick drive.

In addition, in some handwaving way near lightspeed it generates a "cone shaped region of stress" that in some manner allows the ship to travel faster than light. Captains are encourage not to enter FTL travel while inside a solar system, since at that point the gravity field has the mass of a good sized sun and could alter the orbits of the planets. Hmmmm, sounds like a huge case of Jon's Law to me.
The Gentle Giants of Ganymede by James P. Hogan (1978)
The main drive is a torus shaped ring at the ship's nose. It accelerates quantum black holes which travel inside the torus. In some handwaving way this generates a quote "space-time distortion" unquote which the ship continuously 'falls' into.
Path of the Fury by David Weber (1992)
The Fasset drive creates a black hole in front of the ship, which the ship falls into. But the generators move with the ship, pusing the black hole ahead. Standard carrot-on-a-stick drive.
Man-Kzin Wars VIII: Choosing Names edited by Larry Niven (1998)
I have not read this collection, I am getting my information second hand. In Larry Niven's original Kzin stories, the Kzinti use the "gravity planar" aka "gravity polarizer" for propulsion. But apparently one of the authors in this collection didn't get the memo, and invented a totally non-canon propulsion system that was basically a carrot-on-a-stick drive. The author specified that the gizmo used magnetic monopoles in its construction since those are a signature Larry Niven touch.
Earth Strike: Star Carrier by Ian Douglas (William H. Keith, Jr.) (2010)
The spacefighters project a point gravity source capable of accelerating the fighter at 50,000 gees. They can accelerate close to c in about ten minutes flat. In combat though they keep to much slower velocities otherwise aiming their weapons would be impossible. The fighters are crazy maneuverable since the point gravity source can be instantly positioned anywhere to alter the ship's vector in any direction at 50k g.

The huge capital ships and carriers cannot use this drastic propulsion because they are about a kilometer long. At 50k g the gravity gradient across a twenty meter fighter is negligible. But the gradient across a one kilometer battleship will create tidal forces capable of ripping the ship apart.
Gargantia on the Verdurous Planet by Wataru Mitogawa (2013)
The Machine Caliber combat mecha fly by using "artificial gravity sinks." This is a very maneuverable carrot-on-a-stick drive, since a gravity sink can be created at any position nearby the Machine Caliber.
The Tar-Aiym Krang

     He got only the slightest glimpse of their ship, the Gloryhole. That was enough.
     Sandwiched in among bloated freighters and pudgy transports she looked like a thoroughbred in a barnyard. She still had the inevitable shape of a doublekay (Kurita-Kita) drive ship, a balloon stuck on to the end of a plumber’s helper, but the lines were different from most. The balloon at one end was the passenger and cargo space, and the plunger at the other the generating fan for the posigravity field. Instead of being wide and shallow, like a plate, the Gloryhole’s generating fan was narrower and deep, chalicelike. The passenger-cargo area was still balloon-shaped, but it was a streamlined, tapered balloon. Simply on looks alone one could tell that the Gioryhole was faster than any regular freighter or liner aspace.

     ‘Oh, there’s no real danger from change over. The companies like to make a big thing of it to give their passengers a slight thrill. Sure, once in a while you’ll hear about something happening. A meteor will make a millions-to-one infringement on the gravity well of a ship at the moment of shift and the ship will turn inside out, or something equally weird. Those are real exceptions.

     ‘I’ve never been on a doublekay drive ship before. I’m no physicist, but could you maybe give me a quickee explanation of how the thing works? One that even my simple mind could understand’?’
     She sighed. ‘Okay. What the Caplis generator does … that’s what we hold in the “fan” up ahead … is in effect produce a powerful but concentrated gravitational field at the nose of the ship. As soon as the field exceeds the natural one of the ship, the ship moves towards it, naturally attracted by a “body” of greater “mass” than itself. Being part of the ship, the doublekay drive unit naturally goes along with it. But the unit, having moved forward, is set to keep the field at a constant distance from the hull of the craft.
     Therefore the field is moved forward also. The ship will try to catch up to it again, and so on, ad infinitum. The field is in effect pulling the ship instead of pushing it, as the shuttle rockets do, Doublekay vessels actually move in a series of continuous jerks, so rapid and close together that they seem to be one smooth, unbroken pull. The increase or decrease in the size of the field determines the speed of the ship.
     ‘Being a wave and not a particle form of energy, gravity isn’t affected in the same way that mass is on approaching the speed of light. The doublekay field creates a coneshaped zone of stress behind it, in which mass acts differently than it does under normal circumstances. That’s why when we exceed the speed of light I don’t see through you or something. Once we’ve made that initial breakthrough, or “change over,” our rate of travel goes up enormously. It’s something like riding the back of a very tame SCCAM shell.
     ‘Our initial power comes from a small hydrogen “spark-plug” … I wonder sometimes where that word came from … up near the generator housing in the tube section of the ship. Once started up, the field can be “channelled” to a certain extent. That’s where we get our gravity for the ship and power to run the lights and a lit o bar and things.
     “In the event of a drive failure there are provisions for converting the fan loan old ion-type drive, powered by the hydrogen plug. It would take twelve years at its best speed to get from Moth to Power Line, the nearest inhabited planet. Farther out where the stars are more scattered it’s even worse. But twelve years or so is better than never. Stranded ships have been saved that way … those that managed to overcome problems like lack of food and insanity. But the rate of failure for doublekay drives in miniscule. Only rarely can a mere human manage to screw one up.’

From The Tar-Aiym Krang by Alan Dean Foster (1972)
Invaders from the Infinite

(ed note: this is pretty much pure unmitigated technobable)

     “We tried throwing the planet into Sirius. They merely left the planet hurriedly as it fell toward the star, and broke free from our attractive ray.”
     ...Taj Lamor had some of his men bring an attractive ray projector to the ship. The apparatus turned out to be nearly a thousand tons in weight, and some twenty feet long, ten feet wide and approximately twelve feet high. It was impossible to load the huge machine into the Ancient Mariner, so an examination was conducted on the spot, with instruments whose reading was intelligible to the terrestrians operating it. Its principal fault lay in the fact that, despite the enormous energy of matter given out, the machine still gobbled up such titanic amounts of energy before the attraction could be established, that a very large machine was needed. The ray, so long as maintained, used no more power than was actually expended in moving the planet or other body. The power used while the ray was in action corresponded to the work done, but a tremendous power was needed to establish it, and this power could never be recovered.
     Further, no reaction was produced in the machine, no matter what body it was turned upon. In swinging a planet then, a spaceship could be used as the base for the reaction was not exerted on the machine.
     ...“As I see it, the ray is actually a directed gravitational field. Now here is one thing that makes it more interesting, and more useful. It seems to defy the laws of mechanics. It acts, but there is no apparent reaction! A small ship can swing a world! Remember, the field that generates the attraction is an integral, interwoven part of the mesh of Space. It is created by something outside of itself. Like the artificial matter, it exists there, and there alone. There is reaction on that attractive field, but it is created in Space at that given point, and the reaction is taken by all Space. No wonder it won’t move.
     “The work considerations are fairly obvious. The field is built up. That takes energy. The beam is focused on a body, the body falls nearer, and immediately absorbs the energy in acquiring a velocity. The machine replenishes the energy, because it is set to maintain a certain energy-level in the field. Therefore the machine must do the work of moving the ship, just as though it were a driving apparatus. After the beam has done what is wanted, it may be shut off, and the energy in the field is now available for any work needed. It may be drained back into power coils such as ours for instance, or one might just spend that last iota of power on the job.
     “As a driving device it might be set to pull the entire ship along, and still not have any acceleration detectable to the occupants.
     ...“But how is it that the machine is not moved when exerting such force on some other body?” he asked at last.
     “Oh, the ray concentrates the gravitational force, and projects it. The actual strain is in space. It is space that takes the strain, but in normal cases, unless the masses are very large, no considerable acceleration is produced over any great distance. That law operates in the case of the pulled body; it pulls the gravitational field as a normal field, the inverse-square law applying.
     “But on the other hand, the gravity-beam pulls with a constant force.
     “It might be likened to the light-pressure effects of a spot light and a star. The spotlight would push the sun with a force that was constant, no matter what the distance, while the light pressure of the sun would vary as the inverse square of the distance.
     “But remember, it is not a body that pulls another body, but a gravitational field that pulls another. The field is in space. A normal field is necessarily attached to the matter that it represents, or that represents it as you prefer, but this artificial field has no connection in the form of matter. It is a product of a machine, and exists only as a strain in space. To move it you must move all space, since it, like artificial matter, exists only where it is created in space.
     “Do you see now why the law of action and reaction is apparently flouted? Actually the reaction is taken up by space.”

From Invaders from the Infinite by John W. Campbell jr. (1961)

McAndrews Balanced Drive

This was invented by Charles Sheffield, a scientist who was a science fiction author on the side. His "Balanced Drive" is not precisely a carrot-on-a-stick drive. Which is a good thing, since it means this drive can actually work. The bad news is it is unobtanium. The laws of physics do not forbid it, we can calculate its performance, but actually building the monster is way beyond the state-of-the art.

As you recall the advantage of a carrot-on-a-stick is to allow huge acceleration with your spacecraft without killing the crew. The idea is to accelerate the ship at huge levels, but subject the habitat module to an opposed gravitational force in order to counteract the harmful acceleration effects. Sounds simple but as always the devil is in the detail.

The spine of the ship is the "stick." It is 250 meters long and 4 meters in diameter. The combined hab and payload module is threaded on the spine. The module can move along the spine.

The "carrot" part is where the fun begins. It is a disk one hundred meters in diameter and one meter thick. It is composed of electromagnetically stablized compressed matter, with a whopping density of 1,170 tons per cubic centimeter. Less dense than a neutron star, but only just. Mass of the disk is about 9.2×1012 tons, a bit over the mass of Mount Everest.

If you were sitting right in the center of the disk you'd experience exactly 50 gees of gravity and would quickly die. If you were 246 meters away from the disk you'd experience exactly one gee of gravity, due to the distance. This is why the spine is 250 meters long.

The point is: by moving the hab module along the spine, you can alter the gravity it experiences from the disk over a range of 1 to 50 gees.

The ship uses a disk instead of a sphere in order to make the lines of gravitation approximately parallel to the spine, instead of converging to the center of the dense sphere. The tidal forces are about one gee per meter, which isn't much of a problem.

Finally, on the rim of the gravity disk you mount unreasonably strong rocket engines that are powered by a virtually infinite power source. Something that can accelerate a disk of solid neutronium with a mass of Mount Everest at 50 gees for months at a time.

The arrangement is the disk at the top with the rockets firing downward (on the rim so the exhaust does not vaporize the hab module), the spine in the middle, and the hab module at the bottom.

So say you want to crank up the ship so it is accelerating at 32 gees. About the level that will break the crew's bones in five minutes. The rocket engines are gradually throttled up to 32 gees. The crew experiences a rocket acceleration of 32 gees downward, because the rockets accelerate the gravity disk, which tugs on the spine, which tugs on the hab module.

Meanwhile the hab module is moved so it is about 20 meters from the gravity disk. There the crew experiences a gravitational acceleration of 33 gees upward. So 32 gees of rocket acceleration downward plus 33 gees of gravitational acceleration upwards means the crew feels a comfy one gee upward. This is why it is called the "balanced drive."

Naturally you'll need some kind of fail-safe to rapidly move the hab module if the engines fail. The gravity disk can kill you with acceleration just as easily as the rocket engines.


     When the ship was explained to me, I decided that McAndrew didn't really see round corners when he thought. It was just that things were obvious to him before they were explained, and obvious to other people afterwards. I had been saying "inertia-less" to Mac, and he had been just as often saying "impossible." But we hadn't been communicating very well. All I wanted was a drive that would let us accelerate at multiple gees without flattening the passengers. To McAndrew, that was a simple requirement, one that he could easily satisfy—but there was no question of doing away with inertia, of passengers or ship.
     "Take it back to basics," said Wenig, when he was showing me how the Dotterel worked. "Remember the equivalence principle? That's at the heart of it. There is no way of distinguishing an accelerated motion from a gravitational field force, right?"
     I had no trouble with that. It was freshman physics. "Sure. You'd be flattened just as well in a really high gravity field as you would in a ship accelerating at fifty gee. But where does it get you?"
     "Imagine that you were standing on something with a hefty gravity field—Jupiter, say. You'd experience a downward force of about two and a half gee. Now suppose that somebody could accelerate Jupiter away from you, downwards, at two and a half gee. You'd fall towards it, but you'd never reach it—it would be accelerating at the same rate as you are. And you'd feel as though you were in free fall, but so far as the rest of the Universe is concerned you'd be accelerating at two and a half gee, same as Jupiter. That's what the equivalence principle is telling us, that acceleration and gravity can cancel out, if they're set up to be equal and opposite."
     As soon as you got used to Wenig's accent, he was easy to follow—I doubt if anybody could get into the Institute unless he was more than bright enough to explain concepts in easy terms.
     I nodded. "I can understand that easily enough. But you've just replaced one problem with a worse one. You can't find any drive in the Universe that could accelerate Jupiter at two and a half gee."
     "We cannot—not yet, at any rate. Luckily, we don't need to use Jupiter. We can do it with something a lot smaller, and a lot closer. Let's look at the Dotterel and the Merganser. At McAndrew's request I designed the mass element for both of them."
     He went across to the window that looked out from the inside of the Institute to raw space. The Dotterel was floating about ten kilometers away, close enough to see the main components.
     "See the plate on the bottom? It's a hundred meter diameter disk of compressed matter, electromagnetically stabilized and one meter thick. Density's about eleven hundred and seventy tons per cubic centimeter—pretty high, but nothing near as high as we've worked with here at the Institute. Less than you get in anything but the top couple of centimeters of a neutron star, and nowhere near approaching kernel densities. Now, if you were sitting right at the center of that disk, you'd experience a gravitational acceleration of fifty gee pulling you down to the disk. Tidal forces on you would be one gee per meter—not enough to trouble you. If you stayed on the axis of the disk, and moved away from it, you'd feel an attractive force of one gee when you were two hundred and forty-six meters from the center of the disk. See the column growing out from the disk? It's four meters across and two hundred and fifty meters long."
     I looked at it through the scope. The long central spike seemed to be completely featureless, a slim column of grey metal.
     "What's inside it?"
     "Mostly nothing." Wenig picked up a model of the Dotterel and cracked it open lengthwise, so that I could see the interior structure. "When the drives are off, the living-capsule is out here at the far end, two hundred and fifty meters from the dense disk. Gravity feels like one gee, toward the center of the disk. See the drives here, on the disk itself? They accelerate the whole thing away from the center column, so the disk stays flat and perpendicular to the motion. The bigger the acceleration that the drives produce, the closer to the disk we move the living-capsule up the central column here. We keep it so the total force in the capsule, gravity less acceleration, is always one gee, toward the disk."
     He slid the capsule along an electromechanical ladder closer to the disk. "It's easy to compute the right distance for any acceleration—the computer has it built-in, but you could do it by hand in a few minutes. When the drives are accelerating the whole thing at fourteen gee, the capsule is held a little less than fifty meters from the disk. I've been on a test run in the Merganser where we got up to almost twenty gee. Professor McAndrew intended to take it up to higher accelerations on this test. To accelerate at thirty-two gee, the capsule must be about twenty meters from the disk to keep effective gravity inside to one gee. The plan was to take the system all the way up to design maximum—fifty gee thrust acceleration, so that the passengers in the capsule would be right up against the disk, and feel as though they were in free fall. Gravity and thrust accelerations will exactly balance."
     I was getting goose bumps along the back of my neck. I knew the performance of the unmanned med ships. They would zip you from inside the orbit of Mercury out to Pluto in a couple of days, standing start to standing finish. Once in a while you'd get a passenger on them—accident or suicide. The flattened thing that they unpacked at the other end showed what the human body thought of a hundred gee.
     "What would happen if the drives went off suddenly?" I said.
     "You mean when the capsule is up against the disk—at maximum thrust?" Wenig shook his head. "We designed a safeguard system to prevent that, even on the prototypes. If there were a sign of the drive cutting off, the capsule would be moved back up the column, away from the disk. The system for that is built-in."

     The Dotterel worked like a dream. At twenty gee acceleration relative to the Solar System, we didn't feel anything unusual at all. The disk pulled us towards it at twenty-one gee, the acceleration of the ship pulled us away from it at twenty gee, and we sat there in the middle at a snug and comfortable standard gravity. I couldn't even feel the tidal forces, though I knew they were there.

From Moment of Inertia by Charles Sheffield (1980)

Negative Matter Drive

The late Dr. Robert L. Forward was a real physicist whose life's work was gravity research. He invented the Forward Mass Detector and had 18 patents to his name, including the Statite. He was the science fiction writer's friend, writing fiction himself and producting research on juicy SF projects like time travel, negative matter, antimatter rockets, and interstellar laser sail starships.

This means all of his material is not science fiction. It is real. Unlike the carrot-on-a-stick drive, it will actually work. Which is disconcerting because the blasted thing is a reactionless drive, with all that implies.

His most accessable book on these topics is the collection of science essays Indistinguishable from Magic.

Given his life's work, he does have a few things to say on the topic of gravity.

This is not precisely a "carrot-on-a-stick" drive, but it does have a lot of similarities.

INDISTINGUISHABLE FROM MAGIC

(ed note: This is not science fiction, it is reality)

Negative Matter

As unbelievable as these machines for controlling gravity might seem, they at least use a form of matter which we know exists, even if it is presently found only in the interiors of far distant stars. There are speculations that there might exist another type of matter. It has very strange properties. If it ever could be found or made, then a whole new era of gravity control would open up.

All the matter that we know of is the type called regular (positive) matter. Yet both the Newton and the Einstein Theories of Gravity allow the existence of an opposite form of matter, called negative matter. According to the theories of gravity and mechanics, an atom of negative matter would repel all other matter (including other atoms of negative matter).

Now, the first thing you should realize is that negative matter is not "antimatter". Antimatter is different from regular matter in its quantum mechanical properties, not its gravitational properties. Although it has yet to be proven experimentally, we are fairly sure that antimatter attracts other forms of matter, just like normal matter. Negative matter, however, would repel other forms of matter.

We do not know how to make negative matter. But when we do, we will discover that it will not cost us any energy to make that negative matter. Because the rest mass energy of a particle is proportional to its mass (E=mc2), the rest mass energy of a negative mass particle is negative! That means that if we always create equal amounts of positive and negative matter at the same time, it will cost us no net energy to do so! One can imagine a future scene in some huge laboratory, where great machines apply intense electric, magnetic, and gravitational forces to some microscopic point in empty space. The energy levels of the fields are raised higher and higher until the "nothing" itself is ripped apart into a ball of regular matter and an equal sized ball of negative matter, the whole process using no net energy except for the losses in the generating machines.

Once we have our negative matter, we can start using it to make antigravity machines. But we must be very careful how we handle the negative matter. Unlike a chunk of regular matter, which responds to your push by moving away, if you push on a chunk of negative mater, it will come toward you! (If by mistake, you pushed on some negative matter, and it started to move toward you, you must quickly run around behind it and give it a slap on the rear to bring it to a halt!)

Now that we have learned how to control our working material, the simplest antigravity machine that we can make is to form the negative matter into a dense disc and lay it on a good strong floor. If the disc is dense enough and thick enough, then the repulsive gravity field on both sides of the disc will be one Earth gravity. That negative gravity field from the disc would then cancel the gravity field of the Earth. In the region above the disc, the gravity attraction would be zero and you could float there in free fall. (and in a space ship in free fall, such a disc in the ceiling would provide Terra normal gravity by repelling you downward)

The negative gravitational field of negative matter can also be used for gravity propulsion. If you place a ball of very dense negative matter near a similar dense ball of regular matter (which is incidentally attached to your spaceship), you will find that the negative matter ball will repel the regular matter ball, which in turn will attract the negative matter ball. The two dense balls will start to move off in a straight line at a constantly increasing speed. The acceleration will be the strength of the gravitational attraction of one ball for the other, with the negative matter ball chasing after the positive matter ball and the positive matter ball carrying your spaceship along with it. (Question: how do you stop this when you've reached your destination?)

You might at first worry that I'm getting something for nothing. First there were two balls of matter, both standing still, with no kinetic energy. Then, after a while they are both moving off together at high speed with no propulsion energy being expended. You might think that would prove that negative matter is impossible, since it looks like the law of conservation of energy is being violated.

But if you look very closely, you will find that negative mass propulsion does not violate any laws of physics. It is true that the ball of regular mass gains speed and increases its kinetic energy [E=1/2(+m)v2], so it looks like it is getting energy out of nowhere. But while it is doing so, the ball of negative matter is gaining negative energy [E=1/2(-m)v2] and the total energy of the two masses is zero, just as it was when they were standing still. Thus, negative mass propulsion does not violate the law of conservation of energy.

By the same type of argument, you can also show that negative mass propulsion does not violate that other important law of physics, the law of conservation of momentum. For while the momentum of the positive ball of mass is increasing, the momentum of the negative ball of mass is decreasing, resulting in zero net momentum, even though the two balls started out standing still and now are moving off at high speeds.

So far as we know, negative matter doesn't exist. We don't know why it doesn't. After all, both the positive and negative forms of electricity exist, so why not the positive and negative forms of mass? Perhaps there is some yet unknown law of physics that prevents it from forming. But even if we can never obtain this indistinguishable from magic material, we can still devise ways to control gravity with just regular matter, if just work hard and use enough energy and intelligence.

From INDISTINGUISHABLE FROM MAGIC by Robert Forward (1995)
TIMEMASTER

(ed note: Randy's asteroid prospectors discovered an alien creature, which they named the Silverhair. It is apparently composed of negative matter. And so it the "ball", which is basically Silverhair poop.)

     “After I gave him all the facts and showed him some video segments, he conceded that maybe negative matter could exist after all. What really convinced him was the description of my injury, where the cut edges looked like a thin sliver of material had been evaporated.”
     “Why is that?” asked Randy.
     “Well, as Steve explains it, according to one theory, when negative matter touches normal matter, equal amounts vanish—nothing is left, not even energy. The process is called nullification. It’s like the annihilation of matter by antimatter, but in the nullification process, since the normal matter has positive rest mass and the negmatter has negative rest mass, the net rest mass is zero, so zero energy is released. That’s why we didn’t notice any radiation when the Silverhair and I collided.”
     “What else did Steve have to say?” asked Randy.
     “He told us to look for electric or magnetic fields around the Silverhair and the ball,” said Jim. “Negative-matter particles repel each other gravitationally, so they would normally tend to spread far apart from each other. But since the negative-matter particles in the Silverhair and the ball are jammed together at high density, there must be some other force field involved that holds them together.”
     Philippe spoke up. “Hiroshi found a very strong positive electric field associated with both the ball and the Silverhair. It’s as if the material were all made of particles with the same charge.”
     “Normally, particles of the same charge would repel each other and be pushed apart,” said Jim. “But according to Steve, when you attempt to repel a negative-matter particle, it responds in a perverse manner and comes toward you.”
     “That explains one thing,” said Randy. “Siritha noticed some static-cling effects of space dust on her helmet. But there was nothing large—no lightning bolts.”
     “Both the Silverhair and the ball rapidly develop a cloud of orbiting electrons around them,” said Philippe. “They must attract the negative electrons from the plasma in space while repelling the positive ions. The negative electric charge of the electron cloud cancels out the positive electric charge of the negative matter, unless, of course, you get inside the orbiting cloud of electrons and very close to the surface of the negative matter. Hiroshi got some good measurements of the electric field around the ball by enclosing it in a plastic container, sweeping up all the electrons near the ball with a grounded metallic plate, then making measurements inside the container while all the interfering electrons were forced to stay outside the container. We then did some experiments on the ball.”
     “What kind of experiments?” asked Randy, looking intently at Philippe.
     “Since the ball is charged,” Philippe answered, “it’s easy to push it by charging up a metal plate placed near it. Of course, being negative matter, when you push it, it comes toward you.”
     “That can get dangerous, said Jim, holding up his cast. “If it gets too close, you get nullified.”
     “In the experiment Hiroshi did,” Philippe went on, “he used a metal plate with a negative electric charge so it would attract the positive electric charge of the ball. The ball pulled away in the opposite direction, pulling the test apparatus, the power supply, and Hiroshi along with it. When Hiroshi saw what was happening, he quickly turned the field off. He then had to reverse the field and push on the ball for a while to bring it to a halt again.”
     “It was just as Steve predicted,” said Jim in awe. “A true reactionless space drive.”
     “A space drive?” exclaimed Randy in amazement.
     “That is correct,” said Philippe, his voice deepening as his face turned deadly serious. “When that ball of negative matter was pulling Hiroshi and his test apparatus along, there was nothing going in the opposite direction. There was no reaction mass and no energy source involved, but they moved nevertheless. That means a large enough negative-matter ball electrostatically coupled to a positive-matter spacecraft can propel the spacecraft at any acceleration the crew can stand for as long as you want. Flight to the stars at near light speed is no longer a dream . . .”
     When the enormity of the finding hit Randy, a broad smile spread across his face. An interstellar space drive! He had dreamed of exploring the stars and now his dream, could come true! He leaned forward over the table, eyes on Philippe.
     “What are the limitations?” he asked, knowing there must be some.
     “The mass of the negative matter must be exactly equal and opposite to the positive mass of the spacecraft,” said Philippe. “If it isn’t, then the separation distance between the mass and the spacecraft will change with time. If it gets too close, you risk nullification. If it gets too far away, you risk losing it.
     “You have to control the mass of one or the other, then,” mused Randy. “Not easy.” He thought some more. “Didn’t you say the silver ball has a mass of ten tons?”
     “Yes,” said Philippe. “A negative ten tons.”
     “Then that one ball can drive a ten-ton spacecraft. Do you think you could arrange for a demonstration using one of the prospector flitters? They mass around ten tons.”
     “Perhaps,” said Philippe, thinking. His finger rose to feel the mustache under his nose, then followed it across his face and up over his ear as he thought further about the idea. “Yes,” he said finally.
     “Do it!” said Randy. “I’m going to get some breakfast and then go hack out to see the Silverhair. I wonder if Bob can get it to lay more of those silver eggs.”
     “Careful,” warned Philippe. “Don’t kill the goose ...”

(ed note: since the "eggs" are Silverhair poop, Randy now has access to a steady supply of negative matter)


     A week later, Philippe took Randy to the hangar cavity on the other side of Hygiea.
     “We’ve installed the negmatter drive in the hold,” said Philippe, leading the way as he and Randy floated in through the cargo, door in their space suits. “Right at the center-of-mass of the ship.”
     In the center of the cargo bay was a large, cubical metal box nearly twice as tall as Randy. Surrounding the box were some large power supplies. A technician was tying up some stray wires.
     “Is the negmatter ball in there?” asked Randy.
     “Ready to go,” said Philippe. “All six high-voltage supplies are operating and pushing on the ball equally from all directions. In the control room is a three-axis maglev joyball just like the ones that are used in the drop capsules on the rotovators. You push the ball forward, the fore and aft power supplies change their voltages, the negmatter ball gets pushed in the backward direction, and it responds by moving in the forward direction, pushing the spacecraft ahead of it. If you want to go sideways or vertically, just move the ball in that direction and the power supplies for those axes will respond.”

     “Don’t want to get out of sight of the base,” said Randy, he pulled the joyball to one side to bring them around in a large circle.
     “We’re going sideways!” he complained.
     “With only one ball of negmatter, I was unable to obtain any torque control,” said Hiroshi.
     “l’ll fix that,” said Bob, firing some attitude rockets and tuming the ship around so that it faced in the direction it was traveling. “You just do what you want with the drive controls; boy-boss, and granddaddy Bob will follow your every move and keep us lined up with the straight and narrow.”
     After Randy and Bob had completed a few more practice turns, a warning chime carne from the engineering console in front of Hiroshi. Randy instinctively pulled back on the joyball until they were once again in free-fall.
     “ls there a problem?” he asked apprehensively.
     “The ball of negative matter is starting to drift away from the center of the drive control box,” reported Hiroshi. “As Bob uses fuel to control our orientation, the mass of the spacecraft slowly decreases.”
     “Too bad we can’t control the mass of the ship” said Randy.
     “There is a way to do that,” said Hiroshi. “But I didn’t include that feature in this first design.”
     “In that case,” said Randy, pushing forward on the controls again, “let’s head for base and rework the drive. I want to go back to Earth in style!”

     “Hiroshi’s new six-degree-of-freedom negmatter drive is pretty complicated,” said Philippe. “It has linear drive and torque control in all three axes. For control of the ship’s mass, the hull is covered with activated metal foam that absorbs and holds on to any gas or dust that strikes it. With a constant flow of positive matter coming in, we can afford to shoot propellant out from ion engines to provide mass trim and drag makeup.
     “lt’s amazing how fast Hiroshi and the rest of your techs solved the engineering problems of coping with negmatter,” said Randy.
     “Since the negmatter is electrically charged, it turned out to be easy,” said Philippe. “You use radio fields to make the balls vibrate. If you vibrate them at just the right frequency, you can make them break into two, three, or four pieces, or even spit out little droplets.”
     “Glop those small pieces together and you can make any-sized ball you want,” said Randy. “I still think it’s amazing. ”...
     “You sure are a lucky bastard, Randy,” started Steve. “One little find, and you end up owning a spacewarp, a reactionless space drive, and a nearly infinite source of free energy.”
     “Free energy?” Randy repeated, a little taken aback.
     “Yep,” said Steve. “When negative matter and positive matter interact through long-distance forces, the negative matter gains negative kinetic energy, while the positive matter gains positive kinetic energy. Take a drop of highly charged negative matter, push on it with electric fields until it is going at nearly the speed of light, and in return you get electrical energy back. The only limit on the amount of energy you can get is how close to the speed of light you can push the negative matter before losing control of it.”
     “That could cause a serious hazard,” said Randy. “The whole solar system contaminated with high-speed negative-matter particles.”
     “Simple solution,” replied Steve. “Just direct the high-speed negative matter into a beam stop. Generic dirt will do. The negmatter with all its negative kinetic energy will just disappear when it hits the dirt and nullifies.”
     “Hmmm,” said Randy. “Looks like I had better start an energy production division.”

(ed note: and you know that eventually somebody is going to weaponize this)


From TIMEMASTER by Robert Forward (1992)

Star Surgeon

Rattler 1

By the fourth day the attack showed no signs of diminishing. The rattlers on the outer hull were going almost constantly, their power drain making the lights flicker.

The principle which furnished artificial gravity for the floor and compensated for the killing accelerations used by the ships also lay behind the weapons of both sides — the repulsion screen, originally a meteor protection device, the tractor and pressor beams, and the rattler which was a combination of both. The rattler pushed and pulled — vibrated — depending on how narrowly it was focused, at up to eighty Gs. A push of eighty gravities then a pull of eighty gravities, several times a minute. Naturally it was not always focused accurately on target, both ships were moving and taking counter-measures, but it was still tight enough to tear the plating off a hull or, in the case of a small ship, to shake it until the men inside rattled.

There was no fine diagnostic skill required in the treatment of these rattled men. It was all too plain that they suffered from multiple and complicated fractures, some of them of nearly every bone in their bodies. Many times when he had to cut one of the smashed bodies out of its suit Conway wanted to yell at the men who had brought it in, "What do you expect me to do with this. . ."

But this was alive, and as a doctor he was supposed to do everything possible to make it stay that way.

From Star Surgeon by James White (1963)
Rattler 2

The main screen showed a line of heavy cruisers playing ponderous follow-the-leader along the first section of the incision, rattlers probing deep while their pressers held the edges of the wound apart to allow deeper penetration by the next ship in line. Like all of the Emperor class ships they were capable of delivering a wide variety of frightfulness in very accurately metered doses, from putting a few streets full of rioters to sleep to dispensing atomic annihilation on a continental scale. The Monitor Corps rarely allowed any situation to deteriorate to the point where the use of mass destruction weapons became the only solution, but they kept them as a big and potent stick — like most policemen, the Federation's law-enforcement arm knew that an undrawn baton had better and more long-lasting effects than one that was too busy cracking skulls. But their most effective and versatile close-range weapon — versatile because it served equally well either as a sword or a plowshare — was the rattler.

A development of the artificial gravity system which compensated for the killing accelerations used by Federation spaceships, and of the repulsion screen which gave protection against meteorites or which allowed a vessel with sufficient power reserves to hover above a planetary surface like an old-time dirigible airship, the rattler beam simply pushed and pulled, violently, with a force of up to one hundred Gs, several times a minute.

It was very rarely that the corps were forced to use their rattlers in anger — normally the fire-control officers had to be satisfied with using them to clear and cultivate rough ground for newly established colonies — and for the optimum effect the focus had to be really tight. But even a diffuse beam could be devastating, especially on a small target like a scout ship. Instead of tearing off large sections of hull plating and making metallic mincemeat of the underlying structure, it shook the whole ship until the men inside rattled.

From Major Operation by James White (1971)

The Songs of Distant Earth

This is from Sir Arthur C. Clarke's original 1958 short story. He later re-wrote it as a novel in 1986, where the starship crew used a more scientifically plausible but much more boring technique to lift the water.


     "I'm not sure," he replied, truthfully enough. "It depends on how long the repairs take."
     "What went wrong?"
     "Oh, we ran into something too big for our meteor screen to absorb. And — bang! — that was the end of the screen. So we've got to make a new one."
     "And you think you can do that here?"
     "We hope so. The main problem will be lifting about a million tons of water up to the Magellan. Luckily, I think Thalassa can spare it."
     "Water? I don't understand."
     "Well, you know that a starship travels at almost the speed of light; even then it takes years to get anywhere, so that we have to go into suspended animation and let the automatic controls run the ship."
     Lora nodded. "Of course — that's how our ancestors got here."
     "Well, the speed would be no problem if space was really empty — but it isn't. A starship sweeps up thousands of atoms of hydrogen, particles of dust, and sometimes larger fragments, every second of its flight. At nearly the speed of light, these bits of cosmic junk have enormous energy, and could soon burn up the ship. So we carry a shield about a mile ahead of us, and let that get burned up instead. Do you have umbrellas on this world?"
     "Why — yes," Lora replied, obviously baffled by the incongruous question.
     "Then you can compare a starship to a man moving head down through a rainstorm behind the cover of an umbrella. The rain is the cosmic dust between the stars, and our ship was unlucky enough to lose its umbrella."
     "And you can make a new one of water?"
     "Yes; it's the cheapest building material in the universe. We freeze it into an iceberg which travels ahead of us. What could be simpler than that?"

     Lora pretended to work, but she typed the same sentence eight times while Leon delivered his message from the captain of the Magellan. She was not a great deal wiser when he had finished; it seemed that the starship's engineers wished to build some equipment on a headland a mile from the village, and wanted to make sure there would be no objection.
     "Of course!" said Mayor Fordyce expansively, in his nothing's-too-good-for-our-guests tone of voice. "Go right ahead — the land doesn't belong to anybody, and no one lives there. What do you want to do with it?"
     "We're building a gravity inverter, and the generator has to be anchored in solid bedrock. It may be a little noisy when it starts to run, but I don't think it will disturb you here in the village. And of course we'll dismantle the equipment when we've finished."

     By the end of the week, the visitors had built a squat and heavily braced pyramid of metal girders, housing some obscure mechanism, on a rocky headland overlooking the sea. Lora, in common with the 571 other inhabitants of Palm Bay and the several thousand sight-seers who had descended upon the village, was watching when the first test was made. No one was allowed to go within a quarter of a mile of the machine — a precaution that aroused a good deal of alarm among the more nervous islanders. Did the Earthmen know what they were doing? Suppose that something went wrong. And what were they doing, anyway?
     Leon was there with his friends inside that metal pyramid, making the final adjustments — the 'coarse focusing', he had told Lora, leaving her none the wiser. She watched with the same anxious incomprehension as all her fellow islanders until the distant figures emerged from the machine and walked to the edge of the flat-topped rock on which it was built. There they stood, a tiny group of figures silhouetted against the ocean, staring out to sea.
     A mile from the shore, something strange was happening to the water. It seemed that a storm was brewing — but a storm that kept within an area only a few hundred yards across. Mountainous waves were building up, smashing against each other and then swiftly subsiding again. Within a few minutes the ripples of the disturbance had reached the shore, but the centre of the tiny storm showed no sign of movement. It was as if, Lora told herself, an invisible finger had reached down from the sky and was stirring the sea.
     Quite abruptly, the entire pattern changed. Now the waves were no longer battering against each other; they were marching in step, moving more and more swiftly in a tight circle. A cone of water was rising from the sea, becoming taller and thinner with every second. Alteady it was a hundred feet high, and the sound of its birth was an angry roaring that filled the air and struck terror into the hearts of all who heard it. All, that is, except the little band of men who had summoned this monster from the deep, and who still stood watching it with calm assurance, ignoring the waves that were breaking almost against their feet.
     Now the spinning tower of water was climbing swiftly up the sky, piercing the clouds like an arrow as it headed toward space. Its foam-capped summit was already lost beyond sight, and from the sky there began to fall a steady shower of rain, the drops abnormally large, like those which prelude a thunderstorm. Not all the water that was being lifted from Thalassa's single ocean was reaching its distant goal; some was escaping from the power that controlled it and was falling back from the edge of space.
     Slowly the watching crowd drifted away, astonishment and fright already yielding to a calm acceptance. Man had been able to control gravity for half a thousand years, and this trick — spectacular though it was — could not be compared with the miracle of hurling a great starship from sun to sun at little short of the speed of light.
     The Earthmen were now walking back toward their machine, clearly satisfied with what they had done. Even at this distance, one could see that they were happy and relaxed — perhaps for the first time since they had reached Thalassa. The water to rebuild the Magellan's shield was on its way out into space, to be shaped and frozen by the other strange forces that these men had made their servants. In a few days, they would be ready to leave, their great interstellar ark as good as new.
     Even until this minute, Lora had hoped that they might fail. There was nothing left of that hope now, as she watched the man-made waterspout lift its burden from the sea. Sometimes it wavered slightly, its base shifting back and forth as if at the balance point between immense and invisible forces. But it was fully under control, and it would do the task that had been set for it.

From The Songs of Distant Earth (short-story version) by Arthur C. Clarke (1958)

Triton

In Samuel R. Delany's Triton aka Trouble on Triton, the colony has 1 Terran gravity by virtue of the gravity generator plates. The idea is that an object's mass increased near the speed of light due to relativity. So if a plate was moving real close to lightspeed, it would have enough mass to have enough gravity to bring Triton's pathetic gravity up to 1 gee. How do you keep the plate from vanishing into deep space? You don't make the plate move at lightspeed, you make the atomic nuclei composing the plate spin in place at lightspeed.

This won't work because [a] making a small plate have 1 gee of gravity would require it to be denser than neutronium, which would instantly fall through the ground until it reached Triton's core, [b] it would require more power that Sol emits, and [c] spinning a nuclei that fast would make it fission into subatomic particles.

First Lensman

First Lensman

(ed note: the Hill is Terra's main planetary fortress. The Lensmen knew it was going to be attacked by a huge enemy fleet using a huge number of atom bombs. So they took precautions.)

He gritted his teeth. The scouts and light cruisers were doing their damndest, but they were outnumbered three to one, what a lot of stuff was getting through! The Blacks wouldn’t last long, between the Hill and the heavies, but maybe long enough, at that—the Patrol globe was leaking like a sieve! He voiced a couple of bursts of deep-space profanity and, although he was almost afraid to look, sneaked a quick peek. to see how much was left of the Hill. He looked—and stopped swearing in the middle of a four-letter Anglo-Saxon word.

What he saw simply did not make sense. Those Black bombs should have peeled the armor off of that mountain like the skin off of a nectarine and scattered it from the Pacific to the Mississippi. By now there should be a hole a mile deep where the Hill had been. But there wasn’t. The Hill was still there! It might have shrunk a little—Clayton couldn’t see very well because of the worse-than-incandescent radiance of the practically continuous, sense-battering, world-shaking atomic detonations—but the Hill was still there! And as he stared, chilled and shaken, at that indescribably terrific spectacle, a Black cruiser, holed and helpless, fell toward that armored mountain with an acceleration starkly impossible to credit. And when it struck it did not penetrate, and splash, and crater, as it should have done. Instead, it simply spread out, in a thin layer, over an acre or so of the fortress’ steep and apparently still, armored surface!

“You saw that, Alex? Good. Otherwise you could scarcely believe it,” came Kinnison’s silent voice. “Tell all our ships to stay away. There’s a force of over a hundred thousand G’s acting in a direction normal to every point of our surface. The boys are giving it all the decrement they can—somewhere between distance cube and fourth power—but even so it’s pretty fierce stuff. How about the Bolivar and the Himalaya? Not having much luck catching Mr. Black, are they?”

“Why, I don’t know. I’ll check … No, sir, they aren’t. They report that they are losing ground and will soon lose trace.”

“I was afraid so, from that shape. Rodebush was about the only one who saw it coming … well, we’ll have to redesign and rebuild …”


Port Admiral Kinnison, shortly after directing the foregoing thought, leaned back in his chair and smiled. The battle was practically over. The Hill had come through.

The Rodebush-Bergenholm fields had held her together through the most God-awful session of saturation atomic bombing that any world had ever seen or that the mind of man had ever conceived. And the counter-forces had kept the interior rock from flowing like water. So far, so good.

Her original armor was gone. Converted into …what? For hundreds of feet inward from the surface she was hotter than the reacting slugs of the Hanfords.

Delousing her would be a project, not an operation; millions of cubic yards of material would have to be hauled off into space with tractors and allowed to simmer for a few hundred years; but what of that? Bergenholm had said that the fields would tend to prevent the radioactives from spreading, as they otherwise would—and Virgil Samms was still safe!

From First Lensman by E. E. "Doc" Smith (1950)

Robert Heinlein

In his classic novel Time Enough For Love, Robert Heinlein does not go into the details about the paragravity used on starships. But he has the protagonist utilize it in a very unique way.

TIME ENOUGH FOR LOVE

     Sheffield worried these matters while he led auxiliary controls from the gravistat in the control room to the delivery chair. He had decided that, nuisance though it was, his cabin had to be the delivery room; it was the only compartment with enough deck space, a bed at hand, and its own bath. Oh, well, he could stand the nuisance of squeezing past the pesky thing to reach his desk and wardrobe for the next fifty days—sixty at the outside, if he had Llita’s date of conception right and had judged her progress correctly. Then he could disassemble it and stow it...

     ...He positioned the chair, bolted it to the deck, ran it up to maximum height, placed its midwife’s stool in front of it, adjusted the stool until he was comfortable in it, found he could lower the delivery chair ten or twelve centimeters and still have room to work. That done, he climbed into the delivery chair and fiddled with its adjustments—found that it could be made to fit even a person of his height—predictable; some women on Valhalla were taller than he was...

     ...My stool was bolted to the deck, I had added a seat belt. As I strapped myself down, I reminded them that we had a rough ride coming—and this we had not been able to practice; it would have risked miscarriage. “Lock your fingers, Joe, but let her breathe. Comfortable, Llita?”
     “Uh—” she said breathlessly. “I—I’m starting another one!”
     “Bear down, dear!” I made sure my left foot was positioned for the gravistat control and watched her belly.
     Big one! As it peaked, I switched from one-quarter gravity up to two gravities almost in one motion—and Llita let out a yip and the baby squirted like a watermelon seed right into my hands.
     I dragged my foot back to allow the gravistat to put us back on low gee even as I made a nearly instantaneous inspection of the brat...

     ...But more interesting is the Senior’s allegation that he used a pseudogravity field in that year to facilitate childbirth. Was he the first tocologist to use this (now standard) method? Nowhere does he assert this, and the technique is usually associated with Dr. Virginius Briggs of Secundus Howard Clinic and a much later date.

From TIME ENOUGH FOR LOVE by Robert Heinlein (1973)

To his horror, John F. Ptak discovered that some mad scientist actually tried to patent something similar to this back in 1965. Patent 3216423: Apparatus for facilitating the birth of a child by centrifugal force.

Mr. Ptak notes "I found this by accident, and needed to share it immediately, because in the splendid and chilly vastness of the infinite Encyclopedia of Bad Ideas, this entry would seem quite the poster child for such a stupendous effort—the mud to which all dust aspires." I am inclined to agree with him. Marc Abrahams wrote a great piece exploring this idiotic idea.

The attending gynecologist weighs the expectant mother so that the operator can attach the proper amount of balancing counter weights to the other side of the centrifuge. The gynecologist also determines how many gravities of acceleration will be safe.

Upon birth, the newborn rapidly falls into infant reception net (88) which is lined with wad of cotton (97) to protect the baby when impacts on upright switchout plate (93) which turns off the entire clanking mess.

This very bad idea won the 1999 Ig Nobel Prize in the field of Managed Health Care.

I have no idea if Heinlein was aware of this contraption when he wrote his novel. Probably not, the idea is obvious enough.

Space Skimmer

     At first he didn’t realize what he was seeing. Some kind of an altar, he thought. Six giant slabs spaced equally around a —
     Starflake.
     That was his first impression. Something bright and gold and glimmering, Bashing shades of yellow and red and flickering white — copper, bronze, and platinum highlights; dazzling vanes of silver and emerald, amethyst and opal, moonstone and ruby and diamond — something sculptural, clustered, reaching, stretching, describing and making the shape of a spherical sun-burst —
     A frame of some kind — big, more than a hundred feet high —

     A core of silvery shimmering vanes, flashing all colors, diamond-bright; they reached outward in all directions, some farther than others, but almost all ended in planes set at odd angles, no two the same. There were suggestions of platforms and hints of terraces, broad balconies and graceful ramps, places where stanchionlike shapes arced smoothly across from one vane to another. On one of them, he thought he recognized curving steps, but they were upside-down.
     After a long moment, Mass released the breath he was holding; his sigh was the sound of awe.
     He turned his attention to the single bright vane before him, slid his hand back and forth along its still cool, cool surface. It was smooth, almost slippery, so icy and almost greasy to the touch — and so cool, so cool; the touch of his hand warmed it not a bit.
     He stood there looking at it for a long time. A long, long time. The white sun glinted along its surfaces.
     On impulse, he started climbing. He swung himself up into it, arm over arm until he reached one of the wider vanes —
     — tripped and fell sideways — found himself lying flat on his back, a wall of stone and earth to his left, wide emptiness to his right —
     His hands clutched for a hold — slipped along the greasy-feeling, frictionless surface — and realized he wasn’t falling —
     Tentatively, he sat up —
     The emptiness on his right was the sky; the wall of stone and earth on his left, the ground. The horizon was a vertical line ahead, straight where the ocean hung in impossible balance, jagged where the land jutted from it.
     The juxtaposition of earth and sky didn’t hit Mass at first; he was too used to the disconnected orientations of space to be startled and he was too intrigued with examining the surface where he sat. It was untarnished; not a spot of wear or discoloration, no dust, no scratches; just an even, bright plane.
     The feel of it
     — like the feel of a stasis-bite information tab —
     He put his head down close to the surface holding him and looked along it. He straightened and gazed about in wonder — yes, there it was, all around him — the familiar shimmer of a stasis-field, a minute and telltale vagueness describing the edge of every vane and terrace and platform. This metal — if it was metal — would never wear out; it couldn’t — it was motionless in time. This — thing, whatever it was, was indestructible for as long as the stasis endured.
     Mass stood up slowly. Usually a stasis-field was spherical; to generate one that would match the shape of this incredible framework —
     Abruptly he caught sight of the ground below/beside him. He sat down again, suddenly pale.
     He wasn’t falling, he told himself. He wasn’t falling.
     Logically, he knew he wasn’t falling — but his eyes kept telling him he should be. His stomach contracted in fear and confusion. Somehow the ground was twenty feet below him — twenty long feet. A lifetime of conditioning in Streinveldt’s desperate gravity told him a fall that far would be fatal. He clenched his eyes, his fists, his whole body; he went rigid — , He didn’t fall —
     He sat frozen, his eyes tightly shut, and listened to his inner ear. Down was where he was sitting, not where he was looking. He was already down — he wasn’t falling — wasn’t falling —
     He opened an eye.
     He wasn’t falling.
     The sky was to his right, the ground was to his left, the horizon was a vertical division ahead; but he wasn’t falling.
     He forced himself to unclench, forced himself to breathe again, forced himself to swallow. Cold sweat trickled down his side. He relaxed carefully, stifling his fear.
     He even laughed at himself; a hint of a smile on his broad features, embarrassed, almost sheepish.
     Creases appeared at the corners of his wide mouth. He swallowed and his throat still felt tight — and that made him smile some more. He must look silly as hell sitting on the side of a wall and shaking.
     I’m not falling, he told himself again, and stood up slowly.
     He listened to his inner ear; he let that be his guide as to the direction of down and ignored the insistent, but contradictory, information of his eyes. Gradually he became used to this new, surreal orientation. On one side was a wall that stretched up and down, reaching for infinity in each direction.
     On the other side, nothing whiteness. He swallowed, took a breath, then a step.
     Slightly surprised that he didn’t fall, he took another. What had happened was obvious now; there were field-generated gravities here; probably a man could stand on any plane of this framework, at any angle; this “starflake” must be independent of the planet’s influence. Yes, he realized, that would be the source of the singularity he’d detected from space.
     He turned around slowly, surveying the starflake from his vantage point within it. He began moving “upward,” toward its center, walking carefully along a narrowing ramp. He closed his mind against the distorted topography of the planet; he had to. The ramp curved upward, bent through forty-five degrees — but beneath his feet was always down.
     He walked around a twisted shape of sharp metal and suddenly he was at the center. Row, the ground loomed over his head. The empty sky was below the platform on which he stood; he hardly noticed, his attention was focused on —
     An Oracle. Model HA-90.
     He gasped, a sharp intake of breath. Slowly, he approached it, unbelieving. He touched its keyboard and it flashed to life. The scanner plate glowed. Almost without thinking, he slid the translating tab from his pouch and onto the glowing panel. The cuneiforms on the keys became their Streinveldtian equivalents.
     He tapped out carefully, fingers like wooden pegs:
     WHERE — WHAT IS THIS?
     And underneath the question, the answer appeared:
     AE’LAU.
     He typed, WHAT IS AE’LAU?
     And the Oracle answered, SKIMMER NUMBER 312.
     Skimmer number 312!
     Mass jerked as if stung —
     He whirled about in confusion; the shattering vanes dazzled around him —
     Skimmer!
     Of course, he realized, staggering with the suddenness of it — he stared at the skimmer anew. Under-standing blazed fierce in his eyes. Of course, of course The skimmer is a stasis-field ship. lt doesn’t need metal walls — the field is both the hull and the means of moving it.
     All a man needs is a place to stand — these shimmering balconies! There’s neither reason nor need for all of them to be in the same up-down, vertical-horizontal orientation. Any field-generated gravity can be manipulated and up and down can be wherever you want them to be; take advantage of that and make maximum utilization of the stasis-enclosed volume — fill it with a spherical framework.
     Mass imagined the craft hanging in space, men standing on both sides of these wide platforms, standing at odd angles throughout the craft, each man carrying his own up-down orientation with him; wherever one was standing, that was down.
     “Yes, of course —” he breathed in awe. Now he knew why they called it “the ultimate spaceship.” No walls, just a framework and a stasis-field hull.
From Space Skimmer by David Gerrolds (1972)

Paragravity Elevators

RocketCat sez

SF writers sometimes try to convince readers the stories are in the futuristic future by making doors dialate. Some got the bright idea of combining paragravity and elevators to make antigravity elevators. Which makes about as much sense as a nuclear powered dishwasher. And for the same reason. Just think about it! Long open elevator shafts with no carriages, full of magically floating people. Futuristic? Yes. Practical? Oh, come now, let's get real here. Sledgehammer to kill a gnat or what? Just to give your novel a George Jetson atmosphere?

The small problem is: antigrav-elevator users wearing skirts or kilts had best not go commando. Not unless they are exhibitionists or advertising.

But the big problem is failure modes.

The elephant in the room is why throw all this high-tech engineering at a solved problem? The answer "to make my scifi novel look really really kewl" just doesn't cut the mustard. But keep in mind that the idea has been used by some top-notch writers.

Paragravity elevators are conventional elevators where the carriage and cables are replaced by an open shaft with columns of flying people buoyed by paragravity fields. It appears in some older science fiction novels, but appears to have fallen out of favor. Which is not surprising since the concept has problems.

Ignoring the embarrassing peek-a-boo view offered by users wearing skirts or kilts, there is the question of failure modes. If a conventional elevator fails, safety devices will detect the carriage's plummet and slam on the emergency brake shoes. If a paragravity elevator fails, there is no carriage, and no carriage emergency brake shoes. The best it can do is snap shut safety nets at each level and try to catch all the falling people. And good luck getting those people to ever step back into a paragravity elevator for the rest of their lives.

There are also questions about how exactly do the users escape the elevator when they arrive at their destination level. Especially considering the tube contains columns of impatient moving people and a floating user has no convenient carriage floor for locomotion. What are they going to do, flap their arms?

And do you double the elevator footprint by having two dedicated elevator shafts, one for going up and one for going down? Or do you take the footprint reducing but dangerous option of somehow having both up and down traffic in a single tube?

(ed note: The protagonists was a spaceman, until the day he had to go EVA to fix the antenna on the spacecraft centrifuge. While it is still spinning. There is an accident and he is flung into space. He quits his spaceman job since he now has a pathological fear of falling. He takes an assumed name "Saunders")

Tully led the way to the elevator; they crowded in. Most of the employees — even the women — preferred to go down via the drop chute, but Tully always used the elevator. ‘Saunders’, of course, never used the drop chute; this had eased them into the habit of lunching together. He knew that the chute was safe, that, even if the power should fail, safety nets would snap across at each floor level — but he could not force himself to step off the edge.

Tully said publicly that a drop-chute landing hurt his arches, but he confided privately to Saunders that he did not trust automatic machinery.

From ORDEAL IN SPACE by Robert Heinlein (1948)

He led the way straight down the hall to a door at the rear, raising his hand to pass it in a swift, decisive gesture over the plate set into its surface. That triggered the opening, and we stood on the edge of a gray shaft. Lugard did take precautions there, tossing his kit bag out. It floated gently, descending very slowly. Seeing that, he calmly followed it. I had to force myself after him, my suspicions of old installations being very near the surface.

We descended two levels, and I sweated out that trip, only too sure that at any minute the cushioning would fail, to dash us on the floor below. But our boots met the surface with hardly a hint of a jar, and we were in the underground storeroom of the hold.

From DARK PIPER by Andre Norton (1968)

     But to their bafflement there seemed to be no way down at all. They threaded rooms and halls, pushing past the remains of furnishings and strange machinery which at other times would have set them speculating for hours, hunting some means of descent. None appeared to ­exist—only two stairways leading up.
     In the end they discovered what they wanted in the center of a room. It was a dark well, a black hole in which the beam of Kartr’s flash found no end. Although the light did not reveal much it helped them in another way because its owner dropped it. He gave an exclamation and made a futile grab—much too late. Rolth supplied an excited comment, reverting in this stress to his native dialect and only making sense when Kartr ­demanded harshly that he translate.
     “It did not fall! It is floating down—floating!”
     The sergeant sat back on his heels. “Inverse descent! Still working!” He could hardly believe that. Small articles might possibly be upborne by the gravity-dispelling rays—but something heavier—a man—say—
     Before he could protest Rolth edged over the rim, to dangle by his hands.
     “It’s working all right! I’m treading air. Here goes!”
     His hands disappeared and he was gone. But his voice came up the shaft.
     “Still walking on air! Come on in, the swimming’s fine!”
     Fine for Rolth maybe who could see where he was going. To lower oneself into that black maw and hope that the anti-gravity was not going to fail—! Not for the first time in his career with the rangers Kartr silently cursed his overvivid imagination as he allowed his boots to drop into the thin air of the well. He involuntarily closed his eyes and muttered a half-plea to the Spirit of Space as he let go.
     But he was floating! The air closed about his body with almost tangible support. He was descending, of course, but at the rate of a feather on a light breeze. Far below he saw the blue light of Rolth’s torch. The other had reached bottom. Kartr drew his feet together and tried to aim his body toward the pinprick of light.
“Happy planeting!” Rolth greeted the sergeant as he landed lightly, his knees slightly bent, and with no shock at all. “Come and see what I have found.”

From STAR RANGERS by Andre Norton (1953)

It opened at his approach, and he stepped through it into a yawning, brightly lit void over a thousand kilometers deep. He’d braced himself for it yet he knew he appeared less calm than he would have liked—and felt even less calm than he managed to look as he plunged downward at an instantly attained velocity of just over twenty thousand kilometers per hour.

(Ship's Computer) Dahak had stepped his transit shafts’ speed down out of deference to his captain and Terra-born crew, though Colin knew the computer truly didn’t comprehend why they felt such terror. It was bad enough aboard the starship’s sublight parasites, yet the biggest of those warships massed scarcely eighty thousand tons. In something that tiny, there was barely time to feel afraid before the journey was over, but even at this speed it would take almost ten minutes to cross Dahak’s titanic hull, and the lack of any subjective sense of movement made it almost worse.

Yet the captain’s quarters were scarcely a hundred kilometers from Command One—a mere nothing aboard Dahak—and the entire journey took only eighteen seconds. Which was no more than seventeen seconds too long, Colin reflected as he came to a sudden halt. He stepped shakily into a carpeted corridor, glad none of his crew were present to note the slight give in his knees as he approached Command One’s massive hatch.

From THE ARMAGEDDON INHERITANCE by David Weber (1993)

(ed note: this paragravity elevator actually has a carriage)

The elevator was of the new sort that ran by gravitic repulsion. Gaal entered and others flowed in behind him. The operator closed a contact. For a moment, Gaal felt suspended in space as gravity switched to zero, and then he had weight again in small measure as the elevator accelerated upward. Deceleration followed and his feet left the floor. He squawked against his will.

The operator called out, “Tuck your feet under the railing. Can’t you read the sign?”

The others had done so. They were smiling at him as he madly and vainly tried to clamber back down the wall. Their shoes pressed upward against the chromium of the railings that stretched across the floor in parallels set two feet apart. He had noticed those railings on entering and had ignored them.

Then a hand reached out and pulled him down.

From FOUNDATION by Isaac Asimov (1951)

Conspiracy Theory

Ufologists and conspiracy theorists are fond of speaking in breathless tones about something called "electrogravitics", that can convert electricity into gravity. Unfortunately it appears to be about as valid as chemtrails, Bigfoot, the Loch Ness Monster, and sightings of Elvis.

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