What is Delta-v?
{{Noreferences|date=October 2016}} [[File:Delta-Vs for inner Solar System.svg|thumb|376x376px|[[Abbreviation|Abbreviations]] key:''[[Escape velocity|Escape Orbit]] ('''C3'''), [[Geosynchronous orbit]] ('''GEO'''), [[Geostationary transfer orbit]] ('''GTO'''), [[Langrangian Points|Earth–Moon L<sub>5</sub> Lagrangian point]] ('''L5'''), [[Low Earth orbit]] ('''LEO''')'' Graph showing the approximate required Delta-V for [[Mars]], the [[Moon]], and [[Earth science|Earth]], both ways. The red arrows show the directions in which it is possible to slow a craft down using the [[atmosphere]] of what it is going toward. ]] '''Delta-v''', meaning '''delta velocity''' and symbolized as '''Δ''v''''','' ''is a measure of a [[spacecraft]]'s ability to change it's [[trajectory]] (the path it will take in the future). Delta velocity in simple terms means 'the change in speed' It is measured by a unit of speed, usually meters per second (m/s).# Factors that go into calculating delta-v are: # The [[mass]] of the spacecraft. # The amount of [[gravity]] in which the spacecraft currently finds itself. # The [[thrust]] and [[Specific impulse|efficienty]] of the [[Rocket engine|engine]]. # The amount of [[Rocket fuel|fuel]] the spacecraft has. As an example of how delta-v is used, we can imagine a goal: flying a spacecraft into [[low Earth orbit]]. (In simple words, getting a rocket to spin around the Earth). We would first calculate how much delta-v will be required for that journey. Then, with the factors in the above list, we can calculate how much delta-v our spacecraft would need to go on that journey. Like if a person were to drive his car from point A to point B, he'd need to know how much fuel he needs in his car first. But in rocket science, using delta-v is much more relevant, as we have to completely design our spacecraft, including all factors mentioned above. To reach [[Low Earth orbit]], (LEO) our spacecraft would need roughly 10,000 m/s of delta-v. Delta-v can be seen a budget, because if our spacecraft were to use