NASA learned early on that the decompression problems of soft space suits could be avoided if hard-shelled full pressure suits were used. If a soft suit was full pressurized, the astronaut would be splayed out like a starfish and probably could not bend their arms or legs. A hard suit does not have that problem, but instead has the problem of wearing out the astronaut. They are about as easy to work in as a set of medieval plate armor constructed of pure osmium. So NASA looked into adding a powered exoskeleton to the suit, to reduce the muscle strain on the astronaut. NASA eventually decided it was not worth the effort, but the idea just wouldn't go away. Especially if the powered exoskeleton is attached to a suit of armor. It would be "powered armor".
And it took about five minutes for science fiction writers to figure out if you put weapons on on the armor you'd have an unstoppable one-man-army suit that would let a 99 pound weakling beat the snot out of Superman.
The Operator is the entity operating the man amplifier, either a person or a computer running either simplistic pre-programmed task software (i.e., a Roomba vacuum cleaner) or full-fledged AI software (i.e., Ultron).
If the operator is a computer, the man amplifier is classified as a robot.
The Controls are how the operator issues commands to the man amplifier.
A Game Gontroller is a set of joysticks and a keyboard, or something along those lines.
An exoskeleton motion capture system (exo-mocap) is something attached to various portions of the operator's body to measure body motions, such as waldo hands, power gloves, or even a full-body frame. An exo-mocap for human form fitting man amplifiers sometimes use negative feedback. Exo-mocap for huge man amplifiers or remote controlled drones sometimes use haptic feedback. This means the operator is suspended inside the exoskeleton, and the exoskeleton is forced to conform to the current position of the remote drone. This allows the operator to do things like climb stairs and feel when the drone has walked into a brick wall.
A Brain—computer interface (BCI) uses electronics to directly communicate with the human brain in order to issue commands to the man amplifier. Sometimes the man amplifier can communicate back, with sensory information or with enslaving thought control. Also known as mind-machine interface (MMI), brain—machine interface (BMI), or direct neural interface.
In the movie Pacific Rim, the Humongous Mecha each have not one, but two pilots who do synchronised piloting. This seemed like a pretty stupid idea to me, until I read this report. Apparently with a BCI, a single pilot has an accuracy of 67%, but dual pilots have an accuracy of 90%. Reaction times are halved. And momentary lapses of attention are not quite as fatal, since the other pilot is hopefully still on the job. The technical term is "collaborative BCI".
Sometimes the man amplifier also has "computerized reflexes", to automatically react common situations, e.g., tripping over an obstacle or unexpectedly coming under sniper fire.
A Powered-exoskeleton is a human shaped external skeleton constructed of strong materials, with powerful electronic servomotors or hydraulic actuators replacing human muscles.
Man Amplifier: A more or less human sized powered-exoskeleton controlled by an internal exo-mocap with a human operator. In some cases the powered-exoskeleton and the exo-mocap are merged into a single unit. Generally the exo-mocap uses negative feadback. It is called a "man amplifier" because it literally amplifies the person's strength.
For an in-depth analysis on combat exoskeletons, read this article at the always erudite Future War Stories.
Mecha: A larger than human sized powered-exoskeleton controlled by a human operator in an internal control cabin (generally in the Mecha's head or chest) via a game controller, exo-mocap, or BCI. If controlled by exo-mocap, usually has haptic feedback. Generally armor-plated and be-weapon-ed. According to TV Tropes tank-sized mecha are "Mini Mecha" and mecha which are several stories tall are "Humongous Mecha". As they put it, if the operator can be described as a "pilot" or "driver", then you have a Mini Mecha on your hands.
Telerobotics aka "Drone" or "Remote": In this context, a man amplifier, powered armor, or mecha where the human operator is not inside the machine, but instead is located at some distance using remote control. Control is by either game controller, exo-mocap, or BCI. If controlled by exo-mocap it almost invariably has haptic feedback. If it has weapons, it may or may not have armor, depending upon how expendable it is.
There are several challenges standing in the way of creating a useful man amplifier. The primary difficulty is the power supply. The first Iron Man movie got that right, the most important invention of all was the "arc reactor", the miniature fusion reactor that supplies almost unlimited power. Real world man amplifiers use non-rechargeable primary cells, internal combustion engines, and electrochemical fuel cells. These can only power the amplifier for a few hours. For many applications the designers give up and tether the man amplifier to a huge power generator via a power cable.
The material used to construct the exoskeleton is a problem. Aluminum is inexpensive, lightweight, does not stress the motors, and easy to mold. But if the operator is holding an automobile over their head and the aluminum decides to fold up like an accordion (i.e., "fail catastrophically in a high-load condition), the operator will be left feeling quite flat. There are safer but more expensive options like titanium and molded carbon-fiber plates.
The joint actuators (motors) are a problem. Hydraulics have the power and the accuracy, but are heavy due to the fluid-filled hoses and actuator cylinders, and tend to leak hydraulic fluid everywhere. Pneumatics are lighter but since gas is springy the accuracy suffers. Electronic servomotors are a better choice. They are more efficient and power-dense.
Joints are a problem. Human hips and shoulders are ball and socket joints, it is almost impossible to match all the possible human movements with an exoskeleton using single-axis hinges. This limits the operator's flexibility. An exoskeleton with external ball and socket joints have a problem with the series of joints being forced into misalignment. Using a hollow spherical ball joint that encloses the human joint is a better solution, but requires telescoping plates. And the problem of joints in the arms and legs are trivial compared to the nightmare of duplicating the human spine.
Power control and modulation are a problem. The actuators have to not move too fast, over shoot, or otherwise lag behind the operators movement.
Detection of unsafe motions is a problem. You do not want the man amplifier moving in such a way that it breaks the operator's arm, or damages another part of the exoskeleton.
Pinching and joint fouling is a problem. You do not want any part of the exoskeleton's hinges savagely pinching the skin of the operator, nor do you want environmental dust and grit getting into the joints.
Yes, all you young whipper-snappers think that powered armor is the latest cool thing since the first Iron Man movie came out in 2008. Well, as it turns out, the concept goes a long ways back. Even Iron Man himself goes a ways back, he first appeared in a comic book called Tales of Suspense #39 in March 1963.
The concept of a powered fighting suit arguably dates back to E. E. "Doc" Smith's Children of the Lens (1947) with Kimball Kinnision's armored suit made of pure dureum a quarter of an inch thick. Doc Smith had armored suits back in 1937 with Galactic Patrol but those were not power-assisted. Later came Robert Heinlein's classic Starship Troopers (1959). In "Champion Robot" by E R James (1953), "Creakyfoot" is an eight foot high powered suit for use on farms and in factories. And before that, there were all sorts of bizarre patients for assisted walking/running machines powered by compressed air, wind-up springs, and steam.
Post 1960's powered armor will be covered in the subsequent sections.
The difference between an powered exoskeleton and a mecha is pretty straightforwards, but there is still a gray area. Exoskeletons are form-fitting and thus quite close to the size of the operator while mecha are typically huge with the operator inside a control cabin. Having said that, some mecha are controlled by the operator in the cabin wearing an exo-mocap that looks suspiciously like an exoskeleton with no armor (see the McCauley Walker below for an example). Powered exoskeletons are true "man amplifiers", they augment the operator's strength to do tasks. Mecha act more like an operator with a tractor or front-end loader. Mecha range in size from the size of a tank (Armored Trooper Votoms), to a few stories tall (Gundam), to the size of a skyscraper (Space Runaway Ideon), to the size of a city (Macross), or even larger.
The TV Tropes site calls mecha that are tank-sized or smaller "Mini Mecha" while those that are larger are called "Humongous Mecha." As they put it, if the operator can be described as a "pilot" or "driver", then you have a Mini Mecha on your hands. GURPS Mecha defines a "battlesuit" as powered armour where the pilot's arms and legs extend into the suit's arms and legs. A "mecha" is piloted from a cockpit.
Telerobotics in this context means remotely controlled drone. Ideally we would be talking about a humanoid drone controlled by a remote operator wearing an exo-mocap, but in the real world such drones are conspicuous by their absence.
Unlike robots, drones et al have no on-board brains or AI, they are remotely controlled by a human being. Waldoes are fixed in place, while robot arms like the amazing Canadarm can "walk" from socket to socket like a giant metal caterpillar.
And of course halfway between robots and crew are Cyborgs. Are you old enough to remember the word "bionic?" While it would be a big help to have crew members who do not need to breath or be protected from the temperature extremes of the space environment, there are those who question whether such people are really people at all. More to the point, an SF author has to decide if their readers would rather read about metal men or red-blooded fully human heroes. This is why cyborgs in SF are generally either the main character in a world of humans or a small population of peripheral bit players.
NASA is a little uncomfortable with the concept as well. Which is a pity, since a properly designed cyborg would be far superior space travelers compared to us pathetic humans. Implant internal oxygen tanks to remove the need for breathing, implant food tanks to remove the need for eating, and implant an electrode in the pleasure center of their brain to remove the scourge of boredom. You could really save on life support mass by using cyborgs.
The concept of a cyborg covers quite a broad range though. At one end of the spectrum it is quite common to find people who have intraocular lenses in their eyes due to cataract surgery. At the other end one almost never encounters a robot body controlled by a human brain floating in a tank.
In the role playing game Universe, people with enough money can have an "internal gravity web" surgically implanted. This is a series of strong nets anchored to bone that support the internal organs. It allows the person to undergo accelerations larger than 2.5g indefinitely with no ill effects.
In Anne McCaffrey's Brain & Brawn Ship series, The parents of babies with brilliant minds but severe physical disabilities can opt to have their child become a "shell person" instead of being euthanised. They are not quite just a brain in a tank, but the difference is academic. One of the ways a shell person pays off their training debt is by hiring out on a "brainship", basically becoming a cyborg with a starship for a body.
In the "Professor Jameson" novels by Neil R. Jones, the only organic part left in the Zoromes are the brains inside the conical "heads", the rest is machinery. Zoromes are functionally immortal, as long as their conical heads are not damaged. They require no air, food, nor sleep. They do require a minimum amount of heat, but that's about it. They do have various accessories they can attach to their bodies, such as flying wings.
The Professor Jameson stories were one of the longest running SF series, twenty-one stories between 1931 and 1951. Which is surprising since the writing is so tediously bad. The series did influence several SF authors. Isaac Asimov said they were the inspiration for his benevolent positronic robots. Masamune Shirow paid homage to Jones in his cyborg-populated Ghost in the Shell saga by including a no-frills brain-in-a-box design, even naming them Jameson-type cyborgs.
Hans P. Moravec of the Carnegie-Mellon University invented a unique robot design that he calls "Bush robots." One was featured in The Flight of the Dragonfly (AKA Rocheworld) written by Dr. Robert Forward (called the "Christmas Bush" because it is covered in millions of tiny red and green lasers). It can be described as a "fractal robot." Center pivot with six arms. Each arm subdivided into six smaller arms. This repeats quite a few times. The finest arms can reach into a piece of machinery through a tiny hole, fan out, and repair the inside of the machine. Arm segments can also detach for separate jobs. The entire assembly is controlled by the master computer.
You can read Dr. Moravec's NASA sponsored report here.
In the movie 2001, the arms of the pod have a similar fractal arrangement, each arm splitting into two, each of which further splits into two fingers.