Hermann Oberth reasoned that as one section of the rocket cylinder becomes expended, and therefore also becomes dead weight, why not just get rid of it?
This idea is especially important, in light of the fact that in space, velocity is additive. If there is a small rocket on top of a big one, and if the big one is jettisoned and the small one is ignited, then their speeds are added. His scholarly pursuits, however, were interrupted by the First World War. When the war was over, Professor Oberth returned to the University of Munich, but this time to study Physics with several of the most notable scientists of the time. I should like to point out, however, that I am not such and shall never think of becoming one.
But looking forward things are barely discernible. This was followed by a longer version pages in , which was internationally celebrated as a work of tremendous scientific importance. However, three years later Professor Oberth retired and returned to Germany. That Hermann Oberth is one of the three founding fathers of rocketry and modern astronautics is, I think, indisputable.
That all three have advanced the science of rocketry is also indisputable - Professor Oberth, though, possessed a vision that set him apart, even from these great men. By all accounts Hermann Oberth was a humble man especially considering his achievements who had, in his own words, simple goals. Experiments with nuclear-powered rockets, pursued in the mids, were discontinued for similar reasons. Saturn was, therefore, a typical of American rocket development after Specialization, rather than a continual push for more power and heavier payloads, was the dominant trend.
The navy, for example, developed the Polaris—a solid-fuel missile capable of being carried safely aboard submarines and launched underwater. The air force developed the Minuteman as a supplement to the Atlas and Titan. It was smaller, but because it used solid fuel easier to maintain and robust enough to be fired directly from underground "silos.
Heat-seeking and radar-guided missiles had, by the Vietnam War — , replaced guns as the principal weapon for air-to-air combat. They also emerged, in the course of that war, as the antiaircraft weapons most feared by combat pilots. Warships, after nearly four centuries serving principally as gun platforms, were redesigned as missile platforms in the s and s.
Conceived as a vehicle for cheap, reliable access to space, it was powered by three liquid-fuel engines aboard the winged orbiter and two large solid-fuel boosters jettisoned after launch. Both were designed to be reusable. The orbiter's engines would, according to the design specifications, be usable up to fifty times with only limited refurbishing between flights. The boosters, parachuted into the Atlantic Ocean after launch, would be cleaned, refurbished, and refilled with solid fuel for later reuse.
By the early s the shuttle, since becoming operational in , had achieved neither the high flight rates nor the low costs its designers envisioned. Its reusability was, nonetheless, a significant achievement in a field where, for centuries, all rockets had been designed as disposable, single-use machines. Bromberg, Joan Lisa. Baltimore: Johns Hopkins University Press, Surveys NASA's evolving partnership with aerospace companies. Heppenheimer, T. Countdown: A History of Space Flight. New York : John Wiley, Places rocket development in its social, political, and military context. Ley, Willy. Rockets, Missiles, and Men into Space.
New York: Viking, Dated, but useful for its lucid explanations and insider's view of early rocketry. MacDougall, Walter A. The Heavens and the Earth. New York: Basic Books, Definitive history of the interplay of Cold War politics, military missiles, and the U.
Winter, Frank. Rockets into Space. Cambridge, Mass. A compact, nontechnical history of rocket technology. Cite this article Pick a style below, and copy the text for your bibliography. September 22, Retrieved September 22, from Encyclopedia. Then, copy and paste the text into your bibliography or works cited list. Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.
Rockets are used in fireworks, as military weapons, and in scientific applications such as space exploration. Rocket Propulsion The force acting on a rocket, called its thrust, is equal to the mass ejected per second times the velocity of the expelled gases.
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This force can be understood in terms of Newton's third law of motion, which states that for every action there is an equal and opposite reaction. In the case of a rocket, the action is the backward-streaming flow of gas and the reaction is the forward motion of the rocket.
Another way of understanding rocket propulsion is to realize that tremendous pressure is exerted on the walls of the combustion chamber except where the gas exits at the rear; the resulting unbalanced force on the front interior wall of the chamber pushes the rocket forward. A common misconception, before space exploration pointed up its obvious fallacy, holds that a rocket accelerates by pushing on the atmosphere behind it. Actually, a rocket operates more efficiently in outer space, since there is no atmospheric friction to impede its motion. Rocket Design The key elements in designing a rocket are the propulsion system, which includes the propellant and the exit nozzle, and determining the number of stages required to lift the intended payload.
Rocket navigation is usually based on inertial guidance; internal gyroscopes are used to detect changes in the position and direction of the rocket. A propellant consists of two elements, a fuel and an oxidant; engines that are based on the action-reaction principle and that use air instead of carrying their own oxidant are properly called jets. Propellants in use today include both liquefied gases, which are more powerful, and solid explosives, which are more reliable. The chemical energy of the propellants is released in the form of heat in the combustion chamber.
A typical liquid engine uses hydrogen as fuel and oxygen as oxidant; a typical solid propellant is nitroglycerine. In the liquid engine, the fuel and oxidant are stored separately at extremely low temperatures; in the solid engine, the fuel and oxidant are intimately mixed and loaded directly into the combustion chamber.
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A solid engine requires an ignition system, as does a liquid engine if the propellants do not ignite spontaneously on contact. The efficiency of a rocket engine is defined as the percentage of the propellant's chemical energy that is converted into kinetic energy of the vehicle. During the first few seconds after liftoff, a rocket is extremely inefficient, for at least two unavoidable reasons: High power consumption is required to overcome the inertia of the nearly motionless mass of the fully fueled rocket; and in the lower atmosphere, power is wasted overcoming air resistance.
Once the rocket gains altitude, however, it becomes more efficient.
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Although all known rockets currently in use derive their energy from chemical reactions, more exotic propulsion systems are being considered. In ion propulsion, a plasma ionized gas consisting of a mixture of positively charged atoms and negatively charged electrons would be created by an electric discharge and then expelled by an electric field. The engine could provide a low thrust efficiently for long periods; on a lengthy flight this would produce very high velocities, so that if there is ever a trip to the outer planets an ion drive might be used.
Deep Space 1, a space probe launched in to test new technologies, was propelled intermittently by an ion engine. Even nuclear power has been considered for propulsion; in fact, a nuclear ramjet was developed in the early s before it was realized that because the exhaust gases would be highly radioactive such a drive could never be used in earth's atmosphere. Design of the Exit Nozzle A critical element in all rockets is the design of the exit nozzle, which must be shaped to obtain maximum energy from the exhaust gases moving through it.
The nozzle usually converges to a narrow throat, then diverges to create a form which shapes the hypersonic flow of exhaust gas most efficiently. Hence multistage rockets, such as the two-stage Atlas-Centaur or the three-stage Saturn V, became necessary for space exploration.
In these systems, two or more rockets are assembled in tandem and ignited in turn; once the lower stage's fuel is exhausted, it detaches and falls back to earth. Soviet systems clustered several rockets together, operated simultaneously, to obtain a large initial thrust.
Development of Rockets The invention of the rocket is generally ascribed to the Chinese, who as early as AD stuffed gunpowder into sections of bamboo tubing to make military weapons of considerable effectiveness. The 13th-century English monk Roger Bacon introduced to Europe an improved form of gunpowder, which enabled rockets to become incendiary projectiles with a relatively long range.
Rockets subsequently became a common if unreliable weapon. Major progress in design resulted from the work of William Congreve , an English artillery expert, who built a lb 9-kg rocket capable of traveling up to 2 mi 3 km.