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Storable Propellant
A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the engine that expels the propellant is called a reaction engine. Although technically a propellant is the reaction mass used to create thrust, the term "propellant" is often used to describe a substance which is contains both the reaction mass and the fuel that holds the energy used to accelerate the reaction mass. For example, the term "propellant" is often used in chemical rocket design to describe a combined fuel/propellant, although the propellants should not be confused with the fuel that is used by an engine to produce the energy that expels the propellant. Even though the byproducts of substances used as fuel are also often used as a reaction mass to create the thrust, such as with a chemical rocket engine, propellant and fuel are two ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reaction Mass
Working mass, also referred to as reaction mass, is a mass against which a system operates in order to produce acceleration. In the case of a chemical rocket, for example, the reaction mass is the product of the burned fuel shot backwards to provide propulsion. All acceleration requires an exchange of momentum, which can be thought of as the "unit of movement". Momentum is related to mass and velocity, as given by the formula ''P = mv,'' where ''P'' is the momentum, ''m'' the mass, and ''v'' the velocity. The velocity of a body is easily changeable, but in most cases the mass is not, which makes it important. Rockets and rocket-like reaction engines In rockets, the total velocity change can be calculated (using the Tsiolkovsky rocket equation) as follows: \Delta\,v = u\,\ln\left(\frac\right) Where: * ''v'' = ship velocity. * ''u'' = exhaust velocity. * ''M'' = ship mass, not including the working mass. * ''m'' = total mass ejected from the ship (working mass). The term working ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Joule Heating
Joule heating, also known as resistive, resistance, or Ohmic heating, is the process by which the passage of an electric current through a conductor produces heat. Joule's first law (also just Joule's law), also known in countries of former USSR as the Joule–Lenz law, Assuming the element behaves as a perfect resistor and that the power is completely converted into heat, the formula can be re-written by substituting Ohm's law, V = I R , into the generalized power equation: P = IV = I^2R = V^2/R where ''R'' is the resistance. Alternating current When current varies, as it does in AC circuits, P(t) = U(t) I(t) where ''t'' is time and ''P'' is the instantaneous power being converted from electrical energy to heat. Far more often, the ''average'' power is of more interest than the instantaneous power: P_ = U_\text I_\text = I_\text^2 R = U_\text^2 / R where "avg" denotes average (mean) over one or more cycles, and "rms" denotes root mean square. These formulas are valid fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cold Gas Thruster
A cold gas thruster (or a cold gas propulsion system) is a type of rocket engine which uses the expansion of a (typically inert) pressurized gas to generate thrust. As opposed to traditional rocket engines, a cold gas thruster does not house any combustion and therefore has lower thrust and efficiency compared to conventional monopropellant and bipropellant rocket engines. Cold gas thrusters have been referred to as the "simplest manifestation of a rocket engine" because their design consists only of a fuel tank, a regulating valve, a propelling nozzle, and the little required plumbing. They are the cheapest, simplest, and most reliable propulsion systems available for orbital maintenance, maneuvering and attitude control. Cold gas thrusters are predominantly used to provide stabilization for smaller space missions which require contaminant-free operation. Specifically, CubeSat propulsion system development has been predominantly focused on cold gas systems because CubeSats hav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delta-v
Delta-''v'' (more known as " change in velocity"), symbolized as ∆''v'' and pronounced ''delta-vee'', as used in spacecraft flight dynamics, is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such as launching from or landing on a planet or moon, or an in-space orbital maneuver. It is a scalar that has the units of speed. As used in this context, it is not the same as the physical change in velocity of the vehicle. As a simple example, take a conventional rocket-propelled spacecraft which achieves thrust by burning fuel. The spacecraft's delta-''v'' is the change in velocity that spacecraft can achieve by burning its entire fuel load. Delta-''v'' is produced by reaction engines, such as rocket engines, and is proportional to the thrust per unit mass and the burn time. It is used to determine the mass of propellant required for the given maneuver through the Tsiolkovsky rocket equation. For multiple maneuvers, delta-''v'' sums ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluid Dynamics
In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids— liquids and gases. It has several subdisciplines, including ''aerodynamics'' (the study of air and other gases in motion) and hydrodynamics (the study of liquids in motion). Fluid dynamics has a wide range of applications, including calculating forces and moments on aircraft, determining the mass flow rate of petroleum through pipelines, predicting weather patterns, understanding nebulae in interstellar space and modelling fission weapon detonation. Fluid dynamics offers a systematic structure—which underlies these practical disciplines—that embraces empirical and semi-empirical laws derived from flow measurement and used to solve practical problems. The solution to a fluid dynamics problem typically involves the calculation of various properties of the fluid, such as flow velocity, pressure, density, and temperature, as functions of space and ti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Energy
Chemical energy is the energy of chemical substances that is released when they undergo a chemical reaction and transform into other substances. Some examples of storage media of chemical energy include batteries, Schmidt-Rohr, K. (2018). "How Batteries Store and Release Energy: Explaining Basic Electrochemistry", ''J. Chem. Educ.'' 95: 1801-1810. http://dx.doi.org/10.1021/acs.jchemed.8b00479 food, and gasoline (as well as oxygen gas, which is of high chemical energy due to its relatively weak double bond and indispensable for chemical-energy release in gasoline combustion). Schmidt-Rohr, K. (2015). "Why Combustions Are Always Exothermic, Yielding About 418 kJ per Mole of O2", ''J. Chem. Educ.'' 92: 2094-2099. http://dx.doi.org/10.1021/acs.jchemed.5b00333 Breaking and re-making of chemical bonds involves energy, which may be either absorbed by or evolved from a chemical system. If reactants with relatively weak electron-pair bonds convert to more strongly bonded products, ene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Relativistic Physics
In physics, relativistic mechanics refers to mechanics compatible with special relativity (SR) and general relativity (GR). It provides a non-quantum mechanical description of a system of particles, or of a fluid, in cases where the velocities of moving objects are comparable to the speed of light ''c''. As a result, classical mechanics is extended correctly to particles traveling at high velocities and energies, and provides a consistent inclusion of electromagnetism with the mechanics of particles. This was not possible in Galilean relativity, where it would be permitted for particles and light to travel at ''any'' speed, including faster than light. The foundations of relativistic mechanics are the postulates of special relativity and general relativity. The unification of SR with quantum mechanics is relativistic quantum mechanics, while attempts for that of GR is quantum gravity, an unsolved problem in physics. As with classical mechanics, the subject can be divided into "ki ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Momentum
In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass and is its velocity (also a vector quantity), then the object's momentum is : \mathbf = m \mathbf. In the International System of Units (SI), the unit of measurement of momentum is the kilogram metre per second (kg⋅m/s), which is equivalent to the newton-second. Newton's second law of motion states that the rate of change of a body's momentum is equal to the net force acting on it. Momentum depends on the frame of reference, but in any inertial frame it is a ''conserved'' quantity, meaning that if a closed system is not affected by external forces, its total linear momentum does not change. Momentum is also conserved in special relativity (with a modified formula) and, in a modified form, in electrodynamics, quantum mechanics, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photon Rocket
A photon rocket is a rocket that uses thrust from the momentum of emitted photons ( radiation pressure by emission) for its propulsion. Photon rockets have been discussed as a propulsion system that could make interstellar flight possible, which requires the ability to propel spacecraft to speeds at least 10% of the speed of light, ''v'' ≈ 0.1''c'' = 30,000 km/s. Photon propulsion has been considered to be one of the best available interstellar propulsion concepts, because it is founded on established physics and technologies. Traditional photon rockets are proposed to be powered by onboard generators, as in the nuclear photonic rocket. The standard textbook case of such a rocket is the ideal case where all of the fuel is converted to photons which are radiated in the same direction. In more realistic treatments, one takes into account that the beam of photons is not perfectly collimated, that not all of the fuel is converted to photons, and so on. A large amount of fuel w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jet Aircraft
A jet aircraft (or simply jet) is an aircraft (nearly always a fixed-wing aircraft) propelled by jet engines. Whereas the engines in propeller-powered aircraft generally achieve their maximum efficiency at much lower speeds and altitudes, jet engines achieve maximum efficiency at speeds close to or even well above the speed of sound. Jet aircraft generally cruise most efficiently at about Mach 0.8 () and at altitudes around or more. The idea of the jet engine was not new, but the technical problems involved could not begin to be solved until the 1930s. Frank Whittle, an English inventor and RAF officer, began development of a viable jet engine in 1928, and Hans von Ohain in Germany began work independently in the early 1930s. In August 1939 the turbojet powered Heinkel He 178, the world's first jet aircraft, made its first flight. A wide range of different types of jet aircraft exist, both for civilian and military purposes. History After the first instance of powered ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solid
Solid is one of the four fundamental states of matter (the others being liquid, gas, and plasma). The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structural rigidity and resistance to a force applied to the surface. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire available volume like a gas. The atoms in a solid are bound to each other, either in a regular geometric lattice ( crystalline solids, which include metals and ordinary ice), or irregularly (an amorphous solid such as common window glass). Solids cannot be compressed with little pressure whereas gases can be compressed with little pressure because the molecules in a gas are loosely packed. The branch of physics that deals with solids is called solid-state physics, and is the main branch of condensed matter physics (which also includes liquids). Materials s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plasma (physics)
Plasma ()πλάσμα , Henry George Liddell, Robert Scott, ''A Greek English Lexicon'', on Perseus is one of the four fundamental states of matter. It contains a significant portion of charged particles – ions and/or s. The presence of these charged particles is what primarily sets plasma apart from the other fundamental states of matter. It is the most abundant form of ordi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
