11. What is delta V? (A K2S Question)
From The Space Library
Another measure of rocket performance is the amount of velocity that can be achieved starting from rest, usually called "delta V." Amateur rockets have limited performance but can occasionally provide a delta V of almost 328 feet per second. With this velocity change the rocket can reach an altitude of more than 1,300 feet. High performance military rockets can provide about 3300 feet per second of delta V. Space travel requires a very large delta V. The first objective of a launch to space is to get into orbit. To remain in orbit the force of gravity must be balanced by the centrifugal force of the satellite going around the Earth. This is similar to the centrifugal force of a ball whorled around, constrained by the tension of a string. The satellite velocity needed to provide the necessary centrifugal force for low Earth orbit (LEO) is about 25,600 feet per second. However, the trip to orbit suffers several kinds of losses and some extra velocity is required to overcome losses such as steering, altitude, drag and gravity losses. To get a vehicle into LEO from the Earth's surface requires about 30,000 feet per second of delta V. To escape the Earth's gravity field from LEO requires another 9,800 feet per second. Landing on the Moon or other planets and returning home requires even more total delta V capability.
Answer provided by John W. Cole
Question and Answer extracted from the book Kids to Space - by Lonnie Schorer
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