22-01-2013, 03:57 PM
Seminar on The Utility Fog
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INTRODUCTION
Nanotechnology is based on the concept of tiny, self-replicating robots. The Utility Fog is a very simple extension of this idea. Utility Fog consists of a swarm of nanobots ("Foglets") that can take the shape of virtually anything, and change shape on the fly. Here we discuss the technical details and feasibility of this nanoconcept.
Imagine a microscopic robot (as shown in fig.1) It has a body about the size of a human cell and 12 arms sticking out in all directions. A bucketful of such robots might form a "robot crystal" by linking their arms up into a lattice structure. Now take a room, with people, furniture, and other objects in it it’s still mostly empty air. Fill the air completely full of robots. With the right programming, the robots can exert any force in any direction on the surface of any object. They can support the object, so that it apparently floats in the air. They can support a person, applying the same pressures to the seat of the pants that a chair would. They can exert the same resisting forces that elbows and fingertips would receive from the arms and back of the chair. A program running in the Utility Fog can thus simulate the physical existence of an object.
OPERATING MODES
The Utility Fog operates in two modes: First, the "naive" mode where the robots act much like cells and each robot occupies a particular position and does a particular function in a given object. The second, or "Fog" mode, has the robots acting more like the pixels on a TV screen. The object is then formed of a pattern of robots, which vary their properties according to which part of the object they are representing at the time. An object can then move across a cloud of robots without the individual robots moving, just as the pixels on a CRT remain stationary while pictures move around on the screen.
CONTRAST WITH WATERFOG
Unlike water fog, they do not float in the air but form a lattice by holding hands in 12 directions (corresponding to the struts in an octet truss). Each robot has a body that is fairly small compared to its armspread, and the arms are relatively thin. Each arm is telescoping, an action driven by a relatively powerful motor, and can be waved back and forth (2 more degrees of freedom) by relatively weak motors. One could of course design a Foglet (as the robots are called) with many fewer arms, fig.2 correspond to the easier-to-visualize cubic lattice.
FOGLET DESIGN
Most currently proposed nanotechnological designs are based on carbon. Carbon is a marvelous atom for structural purposes, forming a crystal (diamond) which is very stiff and strong. However, a Fog built of diamond would have a problem which nanomechanical designs of a more conventional form do not pose: the Fog has so much surface area exposed to the air that if it were largely diamond, especially on the surface, it would amount to a "fuel-air explosive".
Therefore the Foglet is designed so that its structural elements, forming the major component of its mass, are made of aluminum oxide, a refractory compound using common elements. The structural elements form an exoskeleton, which besides being a good mechanical design allows us to have an evacuated interior in which more sensitive nanomechanical components can operate. Of course, any macroscopic ignition source would vaporize the entire Foglet; but as long as more energy is used vaporizing the exoskeleton than is gained burning the carbon-based components inside, the reaction cannot spread.
FLOW OF FOG AROUND A MOVING OBJECT
The Fog moves an object by setting up a seed-shaped zone around it. The Foglets in the zone move with the object, forming a fairing which makes the motions around it smoother. If the object is moving fast, the Fog around its path will compress to let it go by. The air does not have time to move in the Fog matrix and so the motion is fairly efficient. For slower motions, efficiency is not so important, but if we wish to prevent slow-moving high-pressure areas from interfering with other airflow operations, we can enclose the object’s zone in a self-contained convection cell which moves Foglets from in front to behind it.
Each moving layer of robots is similarly passing the next layer along, so each layer adds another increment of the velocity difference of adjacent layers. Motors for arm extension can run at a gigahertz, and be geared down by a factor of 100 to the main screw in the arm. This will have a pitch of about a micron, giving a linear extension/retraction rate of about 10 meters per second. We can estimate the inter-layer shear rate at this velocity; the foglets are essentially pulling them selves along. Thus for a 100-micron interlayer distance Fog can sustain a 100 meter-per-second shear per millimeter of thickness.
APPLICATIONS
In Space Exploration
The major systems of spaceships will need to he made with special- purpose nanotechnological mechanisms. In the spaceship’s cabin, however, will be art acceleration couch. When not accelerating, which is most of the time; we’d prefer something useful, like empty space, there. The Utility Fog makes a better acceleration couch, anyway.
Fill the cabin with Utility Fog and never worry about floating out of reach of a handhold. Instruments, consoles, and cabinets for equipment and supplies are not needed. Non-simulable items can be embedded in the fog in what are apparently bulkheads. The Fog can add great structural strength to the ship itself; the rest of the structure need be not much more than a balloon. The same is true for spacesuits: Fog inside the suit manages the air pressure and makes motion easy; Fog outside gives extremely fine manipulating ability for various tasks. Of course, like the ship, the suit contains many special purpose non-Fog mechanisms.
Surround the space station with Fog. It needs radiation shielding anyway (if the occupants are long-term); use big industrial Foglets with lots of redundancy in the mechanism; even so they may get re-cycled fairly often. It also makes a good tugboat for docking spaceships. Homesteaders on the Moon could bring along a batch of heavy duty Fog as well as the special-purpose nanotech power generation and waste recycling equipment.