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Field propulsion is the concept of spacecraft propulsion where no propellant is necessary but instead momentum of the spacecraft is changed by an interaction of the spacecraft with external force fields, such as gravitational and magnetic fields from stars and planets.
A reactionless drive is a hypothetical device producing motion without the exhaust of a propellant.A propellantless drive is not necessarily reactionless when it constitutes an open system interacting with external fields; but a reactionless drive is a particular case of a propellantless drive that is a closed system, presumably in contradiction with the law of conservation of momentum.
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The first design of a resonant cavity thruster claiming to be a reactionless drive was by Roger Shawyer in 2001. He called his conical design an "EmDrive", and claimed that it produced thrust in the direction of the base of the cone. Guido Fetta later built a "Cannae Drive", based in part on Shawyer's concept, [18] [17] using a pillbox-shaped ...
Also Abrams' water-cement ratio law. A law which states that the strength of a concrete mix is inversely related to the mass ratio of water to cement. As the water content increases, the strength of the concrete decreases. abrasion The process of scuffing, scratching, wearing down, marring, or rubbing away a substance or substrate. It can be intentionally imposed in a controlled process using ...
MLWN – mean low water neaps; MLWS – mean low water springs; mm – millimetre (SI unit) MM – prefix designating a number in millions (thousand-thousand) MMbod – million barrels of oil per day; MMboe – million barrels of oil equivalent; MMboed – million barrels of oil equivalent per day; MMbpd – million barrels per day
A rotovator is a rotating tether where the lower tip is moving in the opposite direction to the tether's orbital velocity, reducing the difference in velocity relative to the ground, and hence reducing the velocity of rendezvous; the upper tip is likewise moving at greater than orbital velocity, allowing propellantless transfer between orbits.
The twin-cylinder steam engine could be used either to drive the plough winch or to drive the vehicle along, at a speed of up to 150 cm/min (5 ft/min). Although the machine weighed 30 tons complete with 6 tons of fuel, its ground pressure was only 869 kg/m 2 (178 lb/sq ft), considerably less than a man.