Remember the difference between Unobtainium and Handwavium:
UNOBTAINIUM: We can't build a physical example of it, but insofar as we can postulate that it can be built at all, the laws of physics say it would behave like thus and so. While Handwavium and Technobabble tell you what you CAN do, Unobtainium usually tells you what is NOT possible. Examples: gigawatt laser, antimatter weapons, ladderdown reactors.
Science fiction authors can make up handwavium on their own with no help from this website, it ain't that hard. As long as you are not scared of RocketCat and his dreaded Atomic Wedgie. Trying to keep it internally consistent enough so it does not turn around and bite you on the gluteus maximus, on the other hand, is quite difficult. There are some guidelines here.
The popular conception of a black hole is that it sucks everything in, and nothing gets out. However, it is theoretically possible to extract energy from a black hole, for certain values of "from."
Due to their extreme conditions, black holes have a thousand and one uses. A pity there doesn't seem to be any closer that a few light-centuries.
And by the way, there appears to be no truth to the rumor that Russian astrophysicists use a different term, since "black hole" in the Russian language has a scatological meaning. It's an urban legend, I don't care what you read in Dragon's Egg.
In case it wasn't obvious, these are all ultra-high tech. The closest known black hole is about 3,000 light-years away, neutron stars and close orbit white dwarfs are not much closer (for practicality's sake you'll need a faster-than-light starship). And creating ultra-dense objects is a little beyond our ability.
Of course it does require a sizable black hole moving at high velocity. Which should not be a surprise, since this is the page about unobtainium.
As with the Dyson slingshot, the energy used to accelerate the spacecraft is coming from the motion of the hypergravity object. It is just that you could use the blasted thing daily for ten-thousand years before the slowdown of the black hole became detectable.
The spacecraft starts at a reasonble distance from a moving black hole. It fires a beam of photons (laser beam) at the edge of the black hole. The beam skims the black hole's photon sphere, being bent by gravity into a path around the far side of the black hole. The beam breaks free of the opposite edge, and travels back to the spacecraft. What's more, the black hole's relative motion has given the beam a blue-shift. Translation: the beam's energy has been increased and the black hole's relative motion has been slowed by an undetectable microscopic amount. The black hole acts like a gravitational mirror.
The spacecraft loses energy when it emits the photon beam, and normally it gains back exactly the same energy when it reabsorbs the reflected beam. Except that the beam has been blue-shifted, so the spacecraft gains the blue shift energy. This is used to accelerate the spacecraft. The old energy is used to send another bit of photon beam to go harvest some more blueshift. Keep this up until the spacecraft is too far away from the black hole for the beam to reach.
The end result is the spacecraft has been accelerated to 133% (4/3rd) the black hole's velocity, using none of its own energy. As previously mentioned, all the energy is coming from the black hole, but it has energy to spare. The spacecraft does not get close enough to the black hole to be damaged by dangerous gravitational tides nor deadly radiation. The only thing that gets dangerously close is the beam of photons, and photons are much more durable than a spacecraft.
Once the spacecraft has accelerated to 100% of the black hole's velocity, the halo drive will not get any more blue-shift energy. But by that point, it will have gathered enough blue shift energy to eventually accelerate to 133% of the black hole's velocity.
When using a black hole binary to make a halo drive, the spacecraft will be accelerated best if it is moving in a direction along the plane of the binary orbit. To move out of the plane of the orbit the spacecraft will have to use onboard propellant and use up some of the blue-shift energy. Kipping said he has not run the numbers but thinks that a spacecraft could move up to 20° out of the binary orbit plane and still have a final acceleration of 100% of the black holes orbital velocity.
Also interesting is the fact this drive is not limited to low-mass spacecraft, such as solar sail. The spacecraft can be arbitrarily large. "Arbitraily" being defined as "much less mass than the black hole". In other words it could accelerate a spacecraft with the mass of Jupiter.
If you are lucky enough to find a black hole moving near relativistic velocity, then you can kick your ship to relativistic velocities as well. Then you'd really better have a relativistic black hole at the destination or you'll never slow down.
To be practical, you had better set up another black hole halo drive at the destination in order to decelerate to a halt. If your ship can brake to a stand-still using its internal propulsion, it can probably perform the initial acceleration unaided as well, In which case you don't need the blasted black holes in the first place.
It is not required, but the scheme works better with a pair of black holes orbiting each other in compact binary configuration. Especially at relativistic speeds. For details see the paper.
Predictably for this to work the photon beam has to be aimed incredibly precisely. The radius of a black hole is called the Schwarzschild radius (rs). For the photon beam to boomerang, it has to approach the black hole's center closer than 2rs(yes, I know theoretically the distance to a black hole's center is infinity, just roll with it, OK?). But if it approaches too close, 1.5rs, the beam will become trapped in orbit around the hole (the "photon sphere").
Bottom line, the typical boomarange distance is one skillinth of a whillimeter above 1.5rs
The paper points out that this effect can be used for other things besides accelerating spacecraft. Instead of using the energy for propulsion, store it and use it for some other useful purpose. It could also be used to manipulate a binary black hole into a desired configuration, using the halo drive like titanic optical tweezers.
This was a totally silly sci-fi idea when I was a young man. The idea was since a pocket transistor radio could pick up music broadcasts from radio stations with no wires invovled (wirelessly), perhaps it would be possible for an engine to pick up electricity broadcast from a power station with no wires involved. The technical term is Inductive Charging or Wireless power transfer.
Nikola Tesla found out the hard way the drawback to this little scheme. The lions share of the power radiates into the wild blue yonder and is wasted, since Tesla's attempt to channel the energy into standing waves around the entire globe was an utter failure. This means the inverse square law is your enemy.
True, there was lots of work done in the 1960s on transmitting power with beams of microwaves aimed at rectennas. However, while this was wireless, it was not a "broadcast." It was a narrowcast beam, if the rectenna wandered outside the beam the power would be cut off.
Broadcast power was officially confirmed to be a handwavium idea.
Until everything changed in 2006 when some geniuses at M.I.T. figured out how to use resonant coupling to transfer large amounts of power over a distance of a few times the resonator size. You sometimes see this used to charge smartphones, by laying the phone on a "charging mat".
For now, broadcast power seems to have made the jump from pure handwavium into fringe unobtanium.
The main practical problem is how does the power company determine who tapped some power, so the company knows where to send the bill?
This is an ancient idea that is hard-core unobtanium. The idea is if you pick a spot on Terra, somehow dig from that spot to the core of the planet and continue until you emerge at the antipode, in some manner (left as an excercise for the reader) prevent the tunnel from imploding, you will have a gravitationally powered subway. Unobtanium, we can calculate exactly how it would operate, but there is no way we could make one.
You can get a more precise view of a given tunnel's antipodes locations by using the online Antipodes Map. Though a cursor glance at the map above shows that most tunnels have both ends located in the ocean (white areas), and of the ones that involve dry land most have an oceanic end (gold and blue areas). Very frew location have both ends on dry land (orange areas).
Actually, the tunnel does not require the ends to be at the antipodes, it does not have to pass through the center of the planet. All straight-line tunnels (using only gravity as the propulsive force) take the same amount of time to transit, regardless of where the end points are. Transit time is faster if the tunnel is a hypocycloid curve between the points. Sadly if the two points are antipodes, the hypocycloid curve becomes a straight line. For the equations to calculate the transit time, go here.
Dating back to the Orichalcum that was all the rage in Atlantis, to modern-day Wolverine's indestructable Adamantium bones, fiction is full of marvelous materials that would be oh so useful if we could only lay our hands on some.
Material composed of nothing but closely packed neutrons. Found in the core of neutron stars. The best figure I can find for the density of neutronium is 4×1017 kilograms per cubic meter, and dwarf star matter 1×109 kilograms per cubic meter.
No, you can't us it as the ultimate armor because if you somehow take a chunk out of the neutron star's core, the accurséd chunk explodes.
Outside of the core the neutrons undergo beta-decay with a half-life of 10 minutes and 11 seconds (611 seconds) with each cubic centimeter emitting energy at a rate of 19 megawatts average over the first half life.
Translation: sitting next to a cube of neutronium will be like having four and a half sticks of TNT blow up in your lap every second for 611 seconds.
As with all half-life decays, the second half-life will only have half the energy (two and a quarter sticks TNT per second) but by that point there won't be much left of your miserable carcass anyway.
Physicist Luke Campbell points out to me that my understanding is imperfect. Beta-decay is the least of your worries. He told me "An additional thing I didn't see mentioned in the section on neutronium is that all the neutrons are unbound. That means, there is nothing sticking them together. Once removed from the crushing gravity of a neutron star, all the individual neutrons fly off on their own independent happy trajectories. In an instant, you no longer have any kind of -ium any more, but rather a flash of highly penetrating energetic ionizing radiation."
In atomic nuclei, neutrons and protons stick together due to the strong nuclear force. Since the neutrons in a neutron star are not in a nucleus, there ain't no strong nuclear force gluing them. They are unbound.
The only thing keeping them together is the neutron star's outrageous gravity field. Once you take a chunk of neutronium away from the neutron star's gravity, the unbound neutrons composing the chunk instantly go flying in all direction at relativistic speeds. In other words it becomes a blast of neutron radiation with a flux strong enough to shred you into subatomic particles.
Higgsinium and Monopolium
Higgsinium may or may not be handwavium. It depends upon a subatomic particle called the negative Higgsino predicted by supersymmetry theory. So far there is no evidence for supersymmetry from any physics experiment, and obviously no proof the negative Higgsino exists.
Monopolium may or may not be handwavium. It depends upon a subatomic particle called a magnetic monopole. There have been a couple of experiments which produced candidate events that were initially interpreted as monopoles, but are now regarded as inconclusive. On the other hand, pretty much all of the various theories of subatomic physics predict the existence of monopoles.
Nanotechnology(and it's extension nanorobotics) is the concept of molecule sized machine. The idea is attributed to Richard Feynman and it was popularized by K. Eric Drexler. It didn't take long before military researchers and science fiction writers started to speculate about weaponizing the stuff. A good science fiction novel on the subject is Wil McCarthy's Bloom.
There are many ways nanotechnology could do awful things to a military target. One of the first hypothetical applications of nanotechnology was in the manufacturing field. Molecular robots would break down chunks of various raw materials and assemble something (like, say, an aircraft), atom by atom. Naturally this could be dangerous if the nanobots landed on something besides raw materials (like, say, an enemy aircraft). However, since they are doing this atom by atom, it would take thousands of years for some nanobots to construct something (and the same thousands of years to deconstruct the source of raw materials).
But using nanobots for manufacturing suddenly becomes scary indeed if you make the little monsters into self-replicating machines(AKA a "Von Neumann universal constructor") in an attempt to reduce the thousands of years to something more reasonable. Suddenly you are facing the horror of wildfire plague spreading with the power of exponential growth. This could happen by accident, with a mutation in the nanobots causing them to devour everything in sight. Drexler called this the dreaded "gray goo" scenario. Or it could happen on purpose, weaponizing the nanobots.
Drexler is now of the opinion that nanobots for manufacturing can be done without risking gray goo. And Robert A. Freitas Jr. did some analysis that suggest that even if some nanotech started creating gray goo, it would be detectable early enough for countermeasures to deal with the problem.
What about nanobot gray goo weapons? Anthony Jackson thinks that free nanotech that operates on a time frame that's tactically relevant is in the realm of cinema, not science. And in any event, nanobots will likely be shattered by impacting the target at relative velocities higher than 3 km/s, which makes delivery very difficult. Rick Robinson is of the opinion that once you take into account the slow rate of gray goo production and the fragility of the nanobots, it would be more cost effective to just smash the target with an inert projectile. Jason Patten agrees that nanobots will be slow, due to the fact that they will not be very heat tolerant (a robot made out of only a few molecules will be shaken into bits by mild amounts of heat), and dissipating the heat energy of tearing down and rebuilding on the atomic level will be quite difficult if the heat is generated too fast.
Other weaponized applications of nanotechnology will probably be antipersonnel, not antispacecraft. They will probably take the form of incredibly deadly chemical weapons, or artificial diseases.
Some terminology: according to Chris Phoenix, "paste" is non-replicating nano-assemblers while "goo" is replicating nano-assemblers. Paste is safe, but is slow acting and limited to the number of nano-assemblers present. Goo is dangerous, but is fast acting and potentially unlimited in numbers.
"Gray or Grey goo" is accidentally created destructive nano-assemblers. "Red goo" is deliberately created destructive nano-assemblers. "Khaki goo" is military weaponized red goo. "Blue goo" is composed of "police" nanobots, it combats destructive type goos. "Green goo" is a type of red goo which controls human population growth, generally by sterilizing people. "LOR goo" (Lake Ocean River) nano-assemblers designed to remove pollution and harvest valuable elements from water, it could mutate into golden goo. "Golden goo" are out-of-control nanobots which were designed to extract gold from seawater but won't stop (the "Sorcerer's Apprentice" scenario). "Pink goo" is a humorous reference to human beings.
ACE Paste (Atmospheric Carbon Extractor) designed to absorb excess greenhouse gasses and covert them into diamonds or something useful. Garden Paste is a "utility fog" of various nanobots which helps your garden grow (manages soil density and composition for each plant type, controls insects, creates shade, store sunlight for overcast days, etc.) LOR paste: paste version of LOR goo. Medic Paste is a paste of nanobots that heals wounds, assists in diagnosis, and does medical telemetry to monitor the patient's health.
Computronium is a material hypothesized by Norman Margolus and Tommaso Toffoli of the Massachusetts Institute of Technology to be used as "programmable matter," a substrate for computer modeling of virtually any real object. It also refers to a theoretical arrangement of matter that is the best possible form of computing device for that amount of matter.
Room Temperature Superconductor
Superconductors are nifty wires that have exactly zero resistance to the flow of electricity. They are vital to the construction of ultra-powerful magnets (for coilguns, particle beam weapons, and some propulsion systems) and for hyperfast computers.
The first superconductors had to be cooled with expensive and troublesome liquid helium. They became practical when new superconductors were discovered which could work with cheap and easy liquid nitrogen.
But the holy grail is a superconductor that doesn't need to be cooled at all. These are high-temperature superconductors, colloquially called "room-temperature superconductors."
Larry Niven used superconductors a lot in his Known Space series, especially Ringworld. His electrical superconductors are also superconductors of heat, which I have so far failed to find a reference on that topic.
This is an unnaturally strong thread one molecule thick. This means it has remarkably low mass per towing capacity, which makes it popular for moving asteroids and for waterskiing spacecraft and starships.
It will basically cut through anything except another molecule chain. Naturally it is also used to make edged weapons.