The Most Wanted Answers in the E-Age: Space Exploration Edition

Author: Xu Ke
Publisher:
Publish Date: 2005-12-01
Features: Why are launch vehicles essential for space activities? Launch vehicles are indispensable transportation tools for human space activities. They possess enormous thrust and can deliver various types of artificial Earth satellites, manned spacecraft, and interplanetary probes into their respective orbits through different combinations. Launch vehicles are space transportation tools composed of multiple stages and are the only couriers for interstellar travel. Unlike balloons that rely on air buoyancy, launch vehicles fly by generating thrust through the reaction force of expelled gases produced by their own carried fuel. The mission of a launch vehicle is extremely challenging: accurately delivering artificial Earth satellites, manned spacecraft, space stations, or space probes to the predetermined orbits set by scientists.
The principle of rocket flight utilizes the reaction force of objects. Inside the rocket's "belly" is fuel, which, when ignited, produces a large amount of heat, turning into rapidly expanding gas. This gas is forcefully expelled from the rocket's rear, propelling the rocket forward under the reaction force of the gas expulsion. We know that the more heat generated by the fuel, the faster the expelled gas, and the greater the thrust. Scientists have calculated that the exhaust velocity of a typical rocket's gas is approximately 2 kilometers per second. When the fuel weight is 1.72 times the rocket's net weight, the rocket's final velocity equals the gas's exhaust velocity. To achieve a final velocity twice or three times the exhaust velocity, the fuel must be correspondingly increased. However, as fuel is added, the rocket's volume and weight also increase. Pushing lighter and heavier objects with the same force results in different speeds. How can the contradiction of adding fuel while minimizing additional rocket weight be resolved? Scientists devised a brilliant solution: designing the rocket in stages, with each stage carrying fuel. Once a stage is burned out, it is discarded, making the rocket progressively lighter and faster. Combined with other factors such as decreasing gravitational and air resistance as the rocket moves farther from Earth, the rocket can achieve speeds exceeding those of any other mode of transportation.
Generally, launch vehicles are classified into small, medium, and large categories based on their launch mass or the effective payload they can deliver to the predetermined orbit. Their payload capacities vary significantly. For example, the American Corona small rocket can only deliver a payload of 215 kilograms to a low Earth orbit, while the American Atlas V large rocket can carry a payload of 18,150 kilograms to the same orbit. Since the first artificial Earth satellite was launched by the Soviet Union's "Sputnik" rocket on October 4, 1957, over the past four decades, more than 30 series of launch vehicles have been developed and successfully launched by countries and organizations worldwide, including the Soviet Union/Russia, the United States, France, Japan, China, the United Kingdom, the European Space Agency, India, and Israel. They have already...