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Radar

Radar (radio detection and ranging), system or technique for detecting the position, motion, and nature of a remote object by means of radio waves reflected from its surface. Radar systems transmit pulses of electromagnetic waves by means of directional Antennas; some of the pulses are reflected by objects in the path of the beam. Reflections are received by the radar unit, processed electronically, and converted into images on a Cathode-Ray Tube. The distance of the object from the radar source is determined by measuring the time required for the radar signal to reach the target and return. The direction of the object with respect to the radar unit is determined from the direction in which the pulses were transmitted. In most units, the beam of pulses is continuously rotated at a constant speed, or it is scanned (swung back and forth) over a sector at a constant rate. The velocity of the object is sometimes determined by the Doppler Effect: if the object is approaching the radar unit, the frequency of the returned signal is greater than the frequency of the transmitted signal; if the object is receding, the returned frequency is less; and if the object is not moving relative to the radar unit, the frequency of the returned signal is the same as the frequency of the transmitted signal. Most radar units operate on microwave frequencies.

Radial Velocity

Radial velocity, the speed with which a star moves toward or away from the sun. It is measured from the Red Shift or blue shift in the star's spectrum. Also Proper Motion.

Radiation

Radiation is the emission or transmission of energy in the form of Waves through space or through a material medium; the term also applies to the radiated energy itself. The term includes electromagnetic, acoustic, and particle radiation, and all forms of ionizing radiation. According to Quantum Theory,Electromagnetic Radiation may be viewed as made up of Photons. Acoustic radiation is propagated as sound waves. Examples of particle radiation are alpha and beta rays in Radioactivity, and Cosmic Rays.

Radiation Sickness

Radiation sickness is the illness caused by the effects of radiation on body tissues. It may be acute, delayed, or chronic and may occur after repeated (cumulative) exposure to small doses of radiation (as in a plant, a laboratory, or the environment); undue exposure to solar radiation; or exposure to a nuclear explosion. Symptoms may be mild and transitory, or severe, depending on the type of radiation, the dose, and the rate at which exposure is experienced. They include weakness, loss of appetite, vomiting, diarrhea, a tendency to bleed, increased susceptibility to infection, and—in severe cases—brain damage and death. Mild radiation sickness is a common side effect of radiation therapy for Cancer. Exposure to radiation is of concern even in small doses because of possible long-term genetic effects.

Radio

Radio, transmission or reception of Electromagnetic Radiation in the radio frequency range from one place to another without wires. For the propagation and interception of radio waves, a transmitter and receiver are employed. A radio wave carries information-bearing signals; the information may be encoded directly on the wave by periodically interrupting its transmission ( Telegraph) or impressed on the carrier frequency by a process called Modulation, e.g., amplitude modulation (AM) or frequency modulation (FM). In its most common form, radio transmits sounds (voice and music) and pictures ( Television). The sounds (or images) are converted into electrical signals by a Microphone (or camera tube), amplified ( Amplifier), and used to modulate a carrier wave that has been generated by a transmitter. The modulated carrier is also amplified, then applied to an Antenna that converts the electrical signals to electromagnetic waves that radiate into space at the speed of light. Receiving antennas intercept part of this radiation, convert it back into electrical signals, and feed it to a receiver. Once the basic signals have been separated from the carrier wave, they are fed to a Loudspeaker or Cathode-Ray Tube, where they are converted into sound and visual images, respectively. Some celestial bodies and interstellar gases emit relatively strong radio waves that are observed with radio telescopes composed of very sensitive receivers and large directional antennas ( Radio Astronomy). Long-range radio signals enable communications between astronauts and ground-based controllers and carry information from Space Probes as they travel to and encounter distant planets. The invention of the Transistor and other microelectronic devices ( Micro) led to the development of portable transmitters and receivers. Military applications of radio include the proximity fuse and various types of Reconnaissance Satellites. Citizens band (CB) radios, operating at frequencies near 27 megahertz, are used in vehicles for communication while traveling. Also Broadcasting; Communications

Radio Waves

The use of electromagnetic waves in the approximate frequency range from 10 kilocycles/second to 300,000 megacycles/second to transmit or receive electric signals without wires connecting the points of transmission and reception.

Radioactivity

Radioactivity, the spontaneous disintegration or decay of the nucleus of an atom by emission of particles, usually accompanied by . Electromagnetic Radiation. Natural radioactivity is exhibited by several elements, including Radium and Uranium. The radiation produced is of three types: the alpha particle, which is a nucleus (two protons and two neutrons) of an ordinary helium atom; the beta particle, which is a high-speed electron or, in some cases, a positron (the electron's antiparticle); and Gamma Radiation, which is a type of electromagnetic radiation with very short wavelengths. The rate of disintegration of a radioactive substance is commonly designated by its half-life, which is the time required for one half of a given quantity of the substance to decay. Radioactivity may be induced in stable elements by bombardment with particles of high energy. Also Dating; Isotope.

Radiometer

An instrument for the detection or measurement of Electromagnetic Radiation, particularly Infrared Radiation. Radiometers that function by increasing the temperature of the device are called thermal detectors; examples include the bolometer and the Thermocouple.

Radio Frequency Energy (RF)

The energy transferred by electromagnetic wave in the radio frequency spectrum.

Radio Frequency Transmitter

An electronic device that radiates radio frequency waves; the device may be fixed (stationary) or mobile.

Radium

Radium (Ra), is a radioactive metallic element, discovered in Pitchblende in 1898 by Pierre and Marie Curie. It is a rare, lustrous, white Alkaline-Earth Metal that resembles barium in its chemical properties. Radium compounds are found in uranium ores. The Radioactivity of radium and its compounds is used in the treatment of cancer. Radium compounds are mixed with a phosphor in luminous paints. In its radioactive decay, radium emits alpha, beta, and gamma rays and produces heat. Element; Periodic Table.

Radon

(Rn), gaseous radioactive element, discovered by Ernest Rutherford in 1899. A colorless, chemically unreactive Inert Gas, it is the densest gas known. Highly radioactive (emitting alpha rays), it is used chiefly in the treatment of cancer by radiotherapy. In homes and other buildings in some areas of the U.S. radon produced by the radioactive decay of uranium-238 present in soil and rock can reach levels regarded as dangerous, but the seriousness of the problem is unclear.

Ram

1.) To push into position.

2.) To seal a projectile in the bore of a gun.

Rammer

1.) Device for driving a projectile into position in a gun. It may be hand- or power-operated or a part of the receiver mechanism.

2.) Tool used to remove live projectiles from the bore of a gun.

Random Sample

Sample selected without bias or prejudice.

Range

The difference between the smallest and largest measurements in the sample.

Rare Earth Oxides of the Rare-Earth Metals

. The name of an earth is formed from the name of its element by replacing -um with -a. Once thought to be very scarce, they are widely distributed and fairly abundant in the earth's crust. Rare-earth minerals include bastnasite, cerite, euxenite, gadolinite, monazite, and samarskite. Mixed rare earths are used in glassmaking, ceramic glazes, and glass-polishing abrasives, and as catalysts for petroleum refining. Individual purified rare earths are used in lasers and as color-television picture-tube phosphors.

Rare-Earth Metals

Group of chemical elements including those in the Lanthanide series, usually yttrium, sometimes scandium and thorium, and rarely zirconium. Promethium, which is not found in nature, is not usually considered a rare-earth metal. The metals occur together in minerals as their oxides Rare Earths and are difficult to separate because of their chemical similarity. The cerium metals are a subgroup, consisting of the elements with atomic numbers between 57 and 63 and ytterbium.

Rarefraction

Pertaining (among others) to the atmosphere at high altitude or relatively low pressure pulse following a shock wave.

Rated Maximum Pressure

For any type gun, that value of the maximum pressure which is specified in the propellant specification as the upper limit of average pressure which may be developed by an acceptable propellant in the form of propelling charges which will impart the specified muzzle velocity to the specified projectile. The smokeless propellant in propelling charges which, in the acceptance test, develops an average maximum pressure exceeding this value is considered as having failed to pass the test.

RDF (Reinforced Detonating Fuse)

Most frequently applied to reinforced MDF.

RDX (Cyclotrimethylenetrinitramine)

Secondary high explosive used extensively by the military.

A high explosive compound, the term RDX originated as an acronym for research development explosive by the U.S. military. In reality RDX is Cyclotrimethylenetrinitramine - for short cyclonite and is expressed as the empirical formula C₃H₆N₆O₆. Cyclonite is a colorless crystal, with a molecular weight of 222.1, density of 1.82 g/cm³, oxygen balance: -21.6%, nitrogen content: 37.84%, volume of detonation gases: 900 l/kg. Detonation velocity, confined: 8,750 m/s = 28,700 ft/s at r = 1.76 g/cm³. Critical diameter of steel sleeve test: 8mm, impact sensitivity 7.5 N m. RDX is very stable, insoluble in water, sparingly soluble in alcohol, ether and benzene, and soluble in acetone. Cyclohexanone, nitrobenzene and glycol are solvents at elevated temperatures.

RDX is probably the most important high-brisance explosive; its brisant power is owed to its high density and high detonating velocity. It is relatively insensitive (as compared to PETN - an explosive of similar strength). Its performance properties are only slightly inferior to those of the homologous Octogen (HMX).

Reaction Engine

An engine that develops thrust by its reaction to ejection of a substance from it; specifically, such an engine that ejects a jet or stream of gases created by the burning of fuel within the engine.

Recommended Firing Current (Or Energy)

In an EED, the current (or energy) which must be applied to a bridge circuit to cause operation within a specified time.

Recommended Test Current (Or Energy)

In an EED, the current (or energy) that can be applied to a bridge circuit for extended periods without degrading the explosive material or firing device.

Reconnaissance Satellite

An artificial Satellite launched by a country to provide intelligence information on the military activities of foreign countries. There are four major types. Early-warning satellites detect enemy missile launchings. Nuclear-explosion detection satellites are designed to detect and identify nuclear explosions in space. Photo-surveillance satellites provide photographs of enemy military activities, e.g., the deployment of intercontinental ballistic missiles (ICBMs). There are two subtypes: close-look satellites provide high-resolution photographs that are returned to earth via a re-entry capsule, whereas area-survey satellites provide lower-resolution photographs that are transmitted to earth via radio. Later satellites have combined these two functions. Electronic-reconnaissance (ferret) satellites pickup and record radio and radar transmissions while passing over a foreign country. The U.S. and the USSR have launched numerous reconnaissance satellites since 1960.

Rectifier

Rectifier, component of an Electric Circuit that changes alternating current to direct current. Rectifiers operate on the principle that current passes through them freely in one direction, but only slightly or not at all in the opposite direction. Also Diode; Electron Tube.

Red Shift

Red shift, the systematic increase in the wavelength of all light received from a celestial object; it is observed in the shifting of individual lines in the Spectrum of the object toward the red, or longer-wavelength, end of the visible spectrum. Most observed red shifts are the result of the Doppler Effect; they are also produced by gravitation in accordance with the general theory of Relativity. Also Hubble’s Law; Quasar.

Reflection

Reflection, return of a wave, such as light, from a surface it strikes into the medium through which it has traveled. The law of reflection states that the angle of reflection (the angle between the reflected ray and the normal, or line perpendicular, to the surface at the point of reflection) is equal to the angle of incidence (the angle between the incident ray and the normal). Echo; Mirror; Refraction.

Refraction

Refraction, the deflection of a wave on passing obliquely from one transparent medium into a second medium in which its speed is different, as the passage of a light ray from air into glass. The index of refraction of a transparent medium is equal to the ratio of the speed of light in a vacuum to the speed of light in the medium. Snell's law states that the ratio of the sine of the angle i of incidence (angle between the incident ray and the normal, or line perpendicular to the boundary between the two mediums at the point of refraction) to the sine of the angle r of refraction (angle between the refracted ray and the normal) is equal to the ratio of the refracting medium's index of refraction nr to the original medium's index of refraction ni.

Refractory

Very resistant especially to high temperatures; refractive pertains to optics.

Regenerative Cooling

A system for keeping liquid rocket engines cool in which one of the liquid propellants is circulated through the engine thrust chamber walls to protect the metal of the walls from melting under high combustion temperatures.

Regressive Burning

Burning of a propellant grain in such a manner that the surface area decreases as burning progresses.

Relative Force

Ratio of observed maximum pressure developed by a propellant under test to the maximum pressure developed by a standard propellant under identical test conditions.

Relative Strength

The chart below is based on US military explosives used for demolition purposes (tactical breaching is a significantly different task than military demolition).

RELATIVE EFFECTIVENESS FACTOR OF VARIOUS EXPLOSIVES

Explosive Name Principal Use V.O.D. m/s f/s Relative Effectiveness as breaching charge (TNT=1) Intensity Of Poisonous Fumes Water Resistance

TNT Demolition charge and composition explosives 6,900 m/s
22,600 f/s
1.00 Dangerous Excellent

PETN Det cord, blasting caps and demolition charges 8,300 m/s
27,200 f/s
1.66 Slight Excellent

PETN Demolition charges as M118 block or M186 roll 7,100 m/s
23,000 f/s
1.14 Slight Excellent

RDX Det cord, blasting caps and demolition charges 8,350 m/s
27,400 f/s
1.60 Dangerous Excellent

RDX Demolition charges as M118 block or M186 roll 7,100 m/s
23,000 f/s
1.14 Dangerous Excellent

Tetryl Booster charge and composition explosives 7,100 mm/s
23,300 f/s
1.25 Dangerous Excellent

Tetrytol 75/25 Demolition charge,
M2 block
7,000 m/s
23,000 f/s
1.20 Dangerous Excellent

Amatol 80/20 Bursting charge 4,900 mm/s
16,000 f/s
1.17 Dangerous Very Poor

Pentolite 50/50 Booster charge and bursting charge 7,450 m/s
24,400 f/s
--------------- Dangerous Excellent

Composition A3 Booster charge and bursting charge 8,100 m/s
26,500 f/s
--------------- Dangerous Good

Composition B Bursting charge 7,800 m/s
25,600 f/s
1.35 Dangerous Excellent

Composition C3 Demolition charge,
M3 block
7,625 m/s
25,000 f/s
1.34 Dangerous Good

Composition C4 Demolition charge, M5A1 block and M112 block 8,040 m/s
26,400 f/s
1.34 Slight Excellent

Black Powder Time blasting fuse 400 m/s
1,300 f/s
0.55 Dangerous Poor

Ammonium Nitrate Demolition charge and composition explosives 2,700 m/s
8,900 f/s
--------------- Dangerous None

Ammonium Nitrate Demolition charge 3,400 m/s
11,000 f/s
0.42 Dangerous None

Military Dynamite, M1 Demolition charge 6,100 m/s
20,000 f/s
0.92 Dangerous Good

Nitroglycerine Commercial dynamites 7,700 m/s
25,200 f/s
1.50 Dangerous Good

Straight Dynamite
(Commercial 40%)
Demolition charge 4,600 m/s
15,000 f/s
0.65 Dangerous Good if fired within 24 hours

Straight Dynamite
(Commercial 50%)
Demolition charge 5,500 m/s
18,000 f/s
0.79 Dangerous Good if fired within 24 hours

Straight Dynamite
(Commercial 60%)
Demolition charge 5,800 m/s
19,000 f/s
0.83 Dangerous Good if fired within 24 hours

Ammonia Dynamite
(Commercial 40%)
Demolition charge 2,700 m/s
8,900 f/s
0.41 Dangerous Poor

Ammonia Dynamite
(Commercial 50%)
Demolition charge 3,400 m/s
11,000 f/s
0.46 Dangerous Poor

Ammonia Dynamite
(Commercial 60%)
Demolition charge 3,700 m/s
12,000 f/s
0.53 Dangerous Poor

Gelatine Dynamite
(Commercial 40%)
Demolition charge 2,400 m/s
7,900 f/s
0.42 Slight Poor

Gelatine Dynamite
(Commercial 50%)
Demolition charge 2,700 m/s
8,900 f/s
0.47 Slight Poor

Gelatine Dynamite
(Commercial 60%)
Demolition charge 4,900 m/s
16,000 f/s
0.76 Slight Poor

Ammonia Geletine Dynamite(Commercial 40%) Demolition charge 4,900 m/s
16,000 f/s
--------------- Slight Excellent

Ammonia Geletine Dynamite(Commercial 60%) Demolition charge 5,700 m/s
18,700 f/s
--------------- Slight Excellentv

Relativity

Relativity, physical theory, introduced by Albert Einstein, that discards the concept of absolute motion and instead treats only relative motion between two systems or frames of reference. Space and time are no longer viewed as separate, independent entities but rather as forming a four-dimensional continuum called Space Time. In 1905 Einstein enunciated the special relativity theory, in which the hypothesis that the laws of nature are the same in different moving systems also applies to the propagation of light, so that the measured speed of light is constant for all observers regardless of the motion of the observer or of the source of light. From these hypotheses Einstein reformulated the mathematical equations of physics. In most phenomena of ordinary experience the results from the special theory approximate those based on Newtonian dynamics, but the results deviate greatly for phenomena occurring at velocities approaching the speed of light. Among the assertions and consequences of the special theory are the propositions that the maximum velocity attainable in the universe is that of light; that mass increases with velocity; that mass and energy are equivalent; that objects appear to contract in the direction of motion; that the rate of a moving clock seems to decrease as its velocity increases; that events that appear simultaneous to an observer in one system may not appear simultaneous to an observer in another system. Einstein expanded the special theory of relativity into a general theory (completed in 1915) that is principally concerned with the large-scale effects of Gravitation ( Also Cosmology). The general theory recognizes the equivalence of gravitational and inertial mass, and asserts that material bodies produce the curvature of the space-time continuum and that the path of a body is determined by this curvature. The theory predicts that a ray of light is deflected by a gravitational field; observations of starlight passing near the sun, first made by Arthur Eddington and colleagues during a 1919 eclipse of the sun, confirmed this. The theory also predicts a Red Shift of spectral lines of substances in a gravitational field, a result confirmed by observation of light from white dwarf stars. Finally, the theory also accounts for the entire observed perihelion motion of the planet Mercury, only part of which could be explained by Newtonian Celestial Mechanics. Also Motion.

Relay, (electrical)

Material to be added.

Relay, electromechanical

Switch in which the variation of current in one Electric Circuit controls the flow of electricity in another circuit. A relay consists of a movable contact connected to an Electromagnet by a spring. When the electromagnet is energized by the controlling current, it exerts a force on the contact that overcomes the pull of the spring and moves the contact so as to either complete or break a circuit. When the electromagnet is de-energized, the contact returns to its original position.

Relay, (explosive)

An element of a fuze explosive train which augments an outside and otherwise inadequate output of a prior explosive component so as to reliably initiate a succeeding train component. Relays, in general, contain a small single explosive charge such as lead azide and are not usually employed to initiate high explosive charges.

Reliability

A statistical evaluation of the probability of a device performing its design function.

Remaining Velocity

Speed of a projectile at any point along its path of flight. Remaining velocity is usually measured in feet per second.

Remover

An explosive telescoping device designed to remove a canopy from an aircraft.

Resin

Resin, any of a class of amorphous solids or semisolids. Natural resins occur as plant exudations (e.g., of pines and firs), and are also obtained from certain scale insects. They are typically yellow to brown in color, tasteless, and translucent or transparent. Oleoresins contain essential oils and are often sticky or plastic; other resins are exceedingly hard, brittle, and resistant to most solvents. Resins are used in varnish, shellac, and lacquer and in medicine. Synthetic resins, e.g., bakerlite, are widely used in making Plastics.

Resistance

The property of an electric conductor by which it opposes flow of electricity and dissipates electrical energy away from the Electric Circuit, usually as heat. Resistance is basically the same for alternating- and direct-current circuits. A high-frequency alternating current, however, tends to travel near the surface of a conductor. Because such a current uses less of the available cross section of the conductor, it meets with more resistance than direct current. The unit of resistance is the OHM. Also Conduction; Impedance; OHM’s Law; Superconductivity.
Resistance Of Copper & Iron Wire Ohms / 1000’ of wire

AWG Copper Iron

#6 0.395 1.4

#8 0.628 3.7

#10 0.999 6.1

#12 1.590 9.8

#14 2.530 15.6

#16 4.020 24.8

#18 6.380 39.5

#20 10.150 62.7

#21 12.800 76.1

#22 16.140 100.0

#23 20.360 126.0

#24 25.670 159.0

Resistor

Resistor, two-terminal Electric Circuit component that generates heat by offering opposition to an electric current. The most common forms of resistors are made from fine wires of special alloys wound onto cylindrical forms or from a molded composition material containing carbon and other substances in varying amounts. Resistors are rated for the maximum amount of power that they can safely handle.

Restricted Burning Grain

A solid propellant grain in which certain surfaces are restricted or inhibited to provide particular burning characteristics.

Restricted Burning Rate

A solid propellant grain in which certain surfaces are restricted or inhibited to provide particular burning characteristics.

Retrofit

A partial change in older equipment.

Retrorocket

A rocket fired in a direction opposite to the line of flight of the vehicle to which it is attached.

Ricochet

Glancing rebound of a projectile after impact.

Rifle

1.) Any firearm that has rifling in the bore designed to give a spin to the projectile for greater accuracy of fire and longer range (not extensively used in this manner, except for shoulder arms).

2.) To cut spiral grooves (rifling) in the bore of a gun in order to give a spin to the projectile so that it will have a greater accuracy of fire and longer range.

Rifling

Spiral grooves in the bore of a weapon designed to give a spin to the projectile for greater accuracy. Rifling includes both the grooves and the ridges between, called lands.

Rocket

A missile containing combustibles, independent of atmospheric oxygen, which on being ignited, liberate gases producing thrust.

Rocket Propellant

Any agency used for consumption or combustion in a rocket and from which the rocket derives its thrust, such as a fuel oxidizer, additive, catalyst, or any compound or mixture of these. "Rocket propellant" is often shortened to "propellant."

Roll

The rolling of a launch vehicle about its axis as the vehicle continues on its flight path.

Rope (as it pertains to ballistics)

Electromagnetic wave reflectors consisting of long strips of metal foil. Similar to window or chaff, but longer. Dropped from planes or shot into the air in projectile, a small parachute or other device may be attached to each strip to reduce rate of fall.

Rotating Band

Soft metal band around a projectile near its base. The rotating band makes the projectile fit tightly in the bore by centering the projectile, thus preventing escape of gas and giving the projectile its spin as it engages in the rifling.

Round

1.) All the parts that make up the ammunition necessary in firing one shot (also called Complete Round).

2.) One shot fired by a weapon.

Round Of Ammunition

Round.

Rubber

Rubber, any solid substance, usually elastic, that can be vulcanized to improve its elasticity and add strength; the term includes natural rubber, or caoutchouc, and a wide variety of synthetic rubbers, which have similar properties. Rubbers are composed chiefly of Carbonand Hydrogen, but some synthetics also have other elements, e.g., chlorine, fluorine, nitrogen, or silicon. All are compounds of high molecular weight; each consists of a series of one kind of molecule (e.g., isoprene in natural rubber) hooked together in a long chain to form a very flexible, larger molecule, the Polymer. Natural rubber is obtained as latex, a milky suspension of rubber globules found in a large variety of plants, chiefly tropical and subtropical. An important source is the Para Rubber Tree. Latex can be shipped for processing either as a liquid or coagulated by acid and rolled into sheets. For most purposes rubber is ground, dissolved in a solvent, and compounded with other ingredients, e.g., fillers, Pigments, and plasticizers. Known by pre-Columbian Indians of South and Central America, rubber first attracted interest in Europe in the 18th cent. Vulcanization, a process invented (1839) by Charles Goodyear revolutionized the rubber industry. It usually involves heating raw or compounded rubber with Sulfur, causing sulfur bridges to form between molecules. The product is nonsticky, elastic, and resistant to heat and cold. Natural rubber is used chiefly to make tires and inner tubes because it is cheaper than synthetic rubber and has greater resistance to tearing when hot. Natural rubber can be treated to make foam rubber and sponge rubber. The first synthetic rubber was made in Germany in World War I. Today synthetics, e.g., Buna S, neoprene, butyl, and nitrile, account for most of the world's rubber production. Made from Coal, Petroleum, Natural Gas, and Acetylene, synthetic rubbers are resilient over a wider temperature range than natural rubber and are more resistant to aging, weathering, and attack by certain substances, notably, oil, solvents, oxygen, and ozone. Silicone rubbers are used in insulation. Polyurethanes are used in tires, in shoes, and as foams. Neoprene is used for making hose and tank linings. Butyl rubber is used in inner tubes and as insulation.

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