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O

Obturate

To stop or close an opening so as to prevent escape of gas or vapor, to seal as in delay elements.

Obturation

Any process that prevents the escape of gases from the tube of a weapon during the firing of a projectile.

Obturator

A device for making the tube of a weapon gas-tight, preventing any escape of gas until the projectile has left the muzzle.

Octane Number

Octane number, a quality rating for Gasoline indicating the ability of the fuel to resist premature detonation and to burn evenly when exposed to heat and pressure in an Internal Combustion Engine. Premature detonation, indicated by knocking and pinging noises, wastes fuel and may cause engine damage. The octane number can be increased by varying the relative amounts of the different Hydrocarbons that make up the gasoline or by additives, e.g., tetraethyl lead. Federal regulations in the U.S. require commercial gasoline pumps to indicate the octane number, which is usually 87 or 89 for regular grade gasoline and 93 for premium grade. Since the early 1970s most Automobiles have been built to operate on low octane gasoline with little or no lead added.

Octogen

Material to be added.

Octol

A mixture of Octogen (NMX) and TNT 70/30 and 75/25. Performance values:

70/30 75/25

detonation velocity, confined: 8377 8643 m/s

at r = 1.80 1.81 g/cm³

volume of detonation gases: 847 830 l/kg

heat of explosion (H₂O liq.): 1074 1131 kcal/kg

4497 4735 kJ/kg

Office of Surface Mining (OSM)

An agency of the U.S. Department of the Interior regulating surface coal mining and the surface effects of underground coal mining.

Ogive

The shape of the head of the projectile, often a convex solid of revolution generated by an arc of a circle whose center lies on the side of the axis of revolution opposite to the arc.

Ohm

Ohm, symbol O, unit of electrical Resistance, defined as the resistance to the flow of a steady electric current offered by a column of mercury 14.4521 grams in mass with a length of 1.06300 m and with an invariant cross-sectional area, when at a temperature of 0°C.

Ohm’s Law

where: V = voltage of power source

I = current in amperes

R = resistance of circuit in ohms (W)

Solving for current (amps): 

Solving for voltage (volts): 

Solving for resistance (ohms): 

One Watt - One Ampere Cartridge

An EED which will not fire or degrade when one ampere and / or one watt is passed through the bridgewire circuit (usually for a five-minute period).

Optics

Scientific study of light. Physical optics is concerned with the genesis, nature, and properties of light; physiological optics with the part light plays in vision; and geometrical optics with the geometry involved in the reflection and refraction of light as encountered in the study of the mirror and the lens.

Optimum Charge

Web and propellant weight combination which produces maximum velocity at a specified pressure.

Orbit

Orbit, path in space described by a smaller body revolving around a second, larger body where the motion of the orbiting body is dominated by their mutual gravitational attraction ( Celestial Mechanics; Gravitation; Kepler’s Laws). The size and shape of an orbit are specified by

(1) the semimajor axis (a length equal to half the greatest diameter of the orbit) and

(2) the eccentricity (the distance of the larger body from the center of the orbit divided by the length of the orbit's semimajor axis). The position of the orbit in space is determined by three factors:

(3) the inclination, or tilt, of the orbital plane to the reference plane (the ECLIPTIC for sun-orbiting bodies; a planet's Equator for natural and artificial satellites);

(4) the longitude of the ascending Node (measured from the vernal Equinox to the point where the smaller body cuts the reference plane moving south to north); and

(5) the argument of pericenter (measured from the ascending node in the direction of motion to the point at which the two bodies are closest).

These five quantities, plus the time of pericenter passage, are called orbital elements. The gravitational attractions of bodies other than the larger body causes perturbations in the smaller body's motions that can make the orbit shift, or precess, in space or cause the smaller body to wobble slightly.

Ordnance

Military material, such as combat weapons of all kinds with ammunition and equipment for their use.

Organic Chemistry

Organic chemistry, branch of Chemistry dealing with Carbon compounds. Of all the elements, carbon forms the greatest number of different compounds; moreover, compounds that contain carbon are about 100 times more numerous than those that do not. Compounds containing only carbon and Hydrogen are called Hydrocarbons. Organic compounds containing Nitrogen are of great importance to Biochemistry. Organic chemistry is of importance to the petrochemical, pharmaceutical, and textile industries; in textiles a prime concern is the synthesis of new organic molecules and Polymers.

Oscilloscope

Oscilloscope, a device based on a Cathode-Ray Tube used to produce a visual display of electrical signals. Typically the horizontal position of the illuminated point is controlled by the value of the independent variable (often time), while the vertical position is controlled by the dependent variable. A third signal is often used to control the brightness of the point.

OSHA

Occupational Safety and Health Administration. An agency of the Department of Labour in the United States, active in eliminating occupational hazards and promoting employee health and safety.

Output Characteristics

The characteristics of an explosive component which determine the form and magnitude of the energy released when the component functions.

Overturning

Moment (of a projectile in flight) Couple about an axis through the center of gravity, perpendicular to the plane of yaw.

Oxidizer

That portion of a chemical mixture or compound which furnishes the oxygen for burning a fuel or propellant

Oxidizer or Oxidizing Material

A substance, such as a nitrate, that readily yields oxygen or other oxidizing substances to stimulate the combustion of organic matter or other fuel.

Oxygen Balance

1.) The percentage excess or deficiency of oxygen as compared to that required to convert the carbon in an explosive to CO and the hydrogen to HO.

2.) The theoretical percentage of oxygen in an explosive material or ingredient that exceeds (+) or is less than (-) what is needed to produce ideal reaction products. The amount of oxygen, expressed in weight percent, liberated as a result of the complete conversion of the explosive material to CO₂, H₂O, SO₂, Al₂O₂, etc. (“positive” oxygen balance). If the amount of oxygen bound in the explosive is insufficient for the complete oxidation reaction (“negative” oxygen balance), the deficient amount of the oxygen needed to complete the reaction is reported with a negative sign. Commercial explosives must have an oxygen balance close to zero in order to minimize the amounts of toxic gases, particularly carbon monoxide, and nitrous gases, which are involved in the fumes.

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