ACCELERATION The rate of change of velocity, dV/dt [ms-2]
ACCRETION DISC A structure formed by diffuse material in orbit around a central mass distribution such as a star.
AERONAUTICAL, ENGINEERING The branch of engineering which deals with the design of vehicles that fly through a fluid medium such as air, aerodynamics specifically.
AEROSPACE, ENGINEERING The generic branch of engineering which deals with the design of vehicles which fly through air or space, aircraft and spacecraft specifically.
ANTENNA A technology which converts electric currents into radio waves or radio waves into electric currents, typically using a radio transmitter or receiver.
ANTIMATTER Particles of matter which have the same mass as normal particles but with opposite charge and quantum spin. Typical examples include the positron (anti-electron), the antiproton and antihydrogen. Mixing matter and antimatter can lead to 100% annihilation of the original particle pair.
ANTIMATTER PROPULSION A form of spacecraft propulsion which utilises the energy release from matter-antimatter annihilation after a matter and an antimatter particle come into close contact. A 1kg equi-mixed matter-antimatter reaction would release around 90 billion MJ of energy or an enthalpy of 90 billion MJ/kg.
ARTIFICIAL INTELLIGENCE The science and engineering of constructing intelligent machines, although it is typically used in a popular sence to mean machines which have a level of decision making capability equal to or in excess of human brain capacity.
ASTEROID The name given to a group of objects in space that are left over remnants of the formation of the solar system, usually made of icy mantle comet material, rock or metallic materials such as nickel and iron. They are typically tens of meters across up to 1,000 kilometers across. Also known as minor planets of the solar system or planetoids. There is a particularly large group of asteroids in the solar system, between the orbit of Mars and Jupiter.
ASTRONAUTICAL, ENGINEERING The branch of engineering which deals with the design of vehicles which move through space – Spacecraft – and their navigation, orbits and astronauts specifically.
ASTRONOMICAL UNIT The mean distance betweeen the Earth and the Sun. 1 AU = 1.496*10^11 m
ASTRONOMY A branch of the natural sciences which deals with the study of the evolution, formation, physics, chemistry and motion of a group of objects known as planets, stars, comets nebulae, galaxies as well as cosmology.
ASTROPHYSICS A branch of the natural sciences which specialises in the physics and physical properties of objects in the universe, such as planets, stars, the interstellar medium and cosmology.
BACK OF THE ENVELOPE This is a rapid calculational technique typically employed by astronomers, engineers and physicists to compute a problem in an approximate way to indicate if instincts for the problem are verified by basic theory.
BARNARDS STAR A star system located around 5.9 light years away in the constellation of Ophiuchus. It is a low-mass red dwarf star, spectral type M4Ve, and the 4th nearest star to the Sun. It has an apparent magnitude of aorund 9. In the 1970s it was the target star selected for the Project Daedalus mission, on the belief at the time that it may have planets around it, later found to be eroneous.
BIS The British Interplanetary Society, the oldest space organization in the world still in its original form, founded in 1933.
BLACK HOLES These are stars, large than around 3 Solar masses, which have collapsed at the end of their life to form a singularity and an event horizon, whos escape velocity is so large that not even light can escape. Any light that reaches it is completely absorbed and none is reflected back like a perfect black body in thermodynamics. Although quantum mechanics predicts some residue radiation emission that equates to a finite temperature, which is inversely proportional to the stars mass. Black holes have also been discovered at the center of galaxies. A collapsed star was first predicted in a Physical Review paper by Robert Oppenheimer and his student H Snyder in 1939, in a paper titled “On Continued Gravitational Contraction”,
BOUNDARY CONDITION This is a term frequently used in mathematics and physics to describe a set of conditions for the behaviour of a mathematical solution at the boundary of its domain. They allow a solution to be obtained, once appropriate boundary conditions are assumed.
BOW A nautical term which refers to the front end of a ship. Sometimes used in astronautics to refer to the fron tof a Starship.
BROWN DWARF A type of stellar object known a a sub-stellar object because its mass is too low to allow hydrogen to fuse within its core. This occurs when an object has a mass less than 0.08 solar masses. The mass is typically beteen the range of a large gas giant like Jupiter and an object around 75-80 times Jupiter mass. Another name for a Brown Dwarf is a failed star.
CELSIUS A unit of temperature, also known as the centigrade. Absolute zero is equal to 0 K or -273.15 degrees C.
CETI Communication with ExtraTerrestrial Intelligence. This is a branch of SETI which specialises in teh composition and deciphering of messages from an intelligent civlizations should they ever be received.
DECELERATION The negative rate of change of velocity, -dV/dt, indicative of an object slowing down.
DESIGN A vehicle, component or machine, which has been created according to set rules of engineering, with its dimensions, configuration and performance specified, the fidelity of which depends on whether it is a concept, preliminary or detailed design layout.
ELECTRIC FIELD, UNIT
ESA European Space Agency, a space agency in Europe formed by many countries, founded in 1975.
EXHAUST VELOCITY The speed at which a jet of propellant material, once combusted, will leave the engine. Typically measured in units of km/s.
EXOPLANET Defined to be a planet that is outside of our solar system and so does not orbit our own Sun, but another star. Also known as extrasolar planet.
FISSION PROPULSION A form of spacecraft propulsion which relies upon the energy release from a fission chain reaction process. A 1kg amount of fissionable material will release around 82 million MJ of energy or an enthalpy of 82 million MJ/kg.
FUSION PROPULSION A form of spacecraft propulsion which relies upon the energy release from fusion reactions. A pure Deuterium reaction will release 208 million MJ/kg of useful enthalpy as well as 139 MJ/kg of energetic neutrons. A mixture of Deuterium and Helium-3 will release 347 million MJ/kg of useful enthalpy.
GALAXY A massive gravitationally bound group of billions of stars, gas, dust and interstellar medium, the collection of which may be spiral, eliptical or irregular in shape. The Milky Way is the galaxy that our own star inhabits and is characterised by Spiral arms orbiting around a central nucleus. The Milky Way is around 100,000 LY across, with the galactic center being arond 30,000 LY from our Sun.
GIGA, UNIT This is a prefix meaning a billion.
HERTSPRUNG RUSSEL DIAGRAM
ICARUS, PROJECT A theoretical design study into an unmanned interstellar probe originating out of the British Interplanetary Society, in September 2009. Members of the project went on to form the non-profit, Icarus Interstellar.
ION DRIVE PROPULSION
JAXA Japan Aerospace Exploration Agency, founded in 2003.
JBIS The Journal of the British Interplanetary Society, founded in 1934.
KILO, UNIT This is a prefix meaning a thousand.
KELVIN, UNIT A unit of temperature measurement, part of the System International (SI) units. Absolute zero is 0 K, the temperature at which all thermal motion ceases in classical thermodynamics.
LASER Light Amplification by Stimulated Emission of Radiation. A device which emits electromagnetic radiation through a process of optical amplification of the stimulated emission of photons.
LEO Low Earth Orbit
LOOP QUANTUM GRAVITY
LIGHTNESS NUMBER A quantity used in solar sail technology to define the sail characteristic acceleration due to solar radiation pressure to the acceleration caused by solar gravitation at 1 AU, which is equal to 0.00593 m/s^2. The Lightness number is given by:
LIGHT YEARS A unit of distance measurement for objects in space, where a light year is the distance that light travels in a vacuum in one year, travelling at a speed of 299,792,458 m/s. 1LY=9.4607*10^15 m = 63,241 AU.
MAGNETIC FIELD, UNIT
MASS FRACTION A quantity used to measure the efficiency of the spacecraft design, usually the ratio of the propellant mass and the initial mass of the vehicle, if referring to the propellant mass fraction. However, the ratio of initial payload mass to the otherwise empty spacecraft mass is termed the payload fraction.
MASS RATIO A quantity used to describe the efficiency of a rocket, by measuring the ratio of the intial vehicle mass (including propellant) to the final stagine mass (when the propellant has been used up). For a given mission, the lower the mass ratio with a specific propellant, the more efficient the rocket. Mass ratio is typically denoted mo/mf.
MEAN FREE PATH
METRIC, SPACE TIME
NASA National Aeronautics and Space Administration. US Space agency founded in 1958.
QUANTUM FIELD THEORY
SETA Search for Extraterrestrial Artifacts, the name given to the group of studies that aim to search for technological artifacts in the solar system or beyond left behind by another intelligent race.
SETI Search for Extraterrestrial Intelligence, the name given to the group of studies that aim to search for intelligent life in the universe.
SPECIFIC IMPULSE A measure of efficiency for a rocket or jet engine. It is typically defined in units of seconds (s) but technically it is the force with respect to the amount of propellant ignited per unit of time.
SPEED OF LIGHT The speed that electromagnetic waves travel in a vacuum, usually denoted by the symbol c, and given by 299,792,458 m/s. For Back of the Envelope calculations use 300,000 km/s.
STARSHIP The generic name given to any machine or technology which travels from one Stellar system to another, typically crossing light years distance per trip, crewed or robotic. The word ‘ship’ is a reference to ships sailing across the ocean, with the analogy being that Starships also sail through space to distance stars.
STERN A nautical term used to refer to the back part of a ship. Sometimes used in astronautics to refer to the back part of a starship.
TSIOLKOVSKY ROCKET EQUATION A equation discovered theoretially by the Russian Konstantin Tsiolkovsky in 1903, which describes the motion of spacecraft by the delta-V or the maximum speed change of the vehicle, as a function of the initial total mass mo, final mass mf and exhaust velocity Vex, where the exhaust velocity can also be written Vex=Isp.g0, where Isp is the specific impulse and g0 is the gravitational constant, 9.81 m/s^2.
WARP DRIVE The Science Fiction name given to spacecraft propulsion methods which attempt to move across space by the manipulation of space-time using Einstein’s General Theory of Relativity and Quantum Field Theory. Space-time is expanded (like in Big Bang Cosmology) and collapsed (like in the collapse ofa Black Hole), with the speed of the ‘warp bubble’ being controlled by the expansion/collapse rate. Also known as Metric Engineering. Calculations show that such methods of transport require enormous amounts of negative energy.
WET MASS The mass of a spacecraft which includes all initial contributions from the propellant, vehicle structure and payload.
Go back to Institute for Interstellar Studies main web site: www.I4IS.org