Thus it can be shown that, provided the exhaust velocity is fixed, this means that delta- v can be summed: Increasing the delta- v provided by a propulsion system can be achieved by:īecause the mass ratios apply to any given burn, when multiple maneuvers are performed in sequence, the mass ratios multiply. Therefore, in modern spacecraft propulsion systems considerable study is put into reducing the total delta- v needed for a given spaceflight, as well as designing spacecraft that are capable of producing larger delta- v. The rocket equation shows that the required amount of propellant dramatically increases with increasing delta- v. The total delta- v needed is a good starting point for early design decisions since consideration of the added complexities are deferred to later times in the design process. The actual acceleration vector would be found by adding thrust per mass on to the gravity vector and the vectors representing any other forces acting on the object. The time-rate of change of delta- v is the magnitude of the acceleration caused by the engines, i.e., the thrust per total vehicle mass. But even for geostationary spacecraft using electrical propulsion for out-of-plane control with thruster burn periods extending over several hours around the nodes this approximation is fair.ĭelta- v is typically provided by the thrust of a rocket engine, but can be created by other engines. For low thrust systems, typically electrical propulsion systems, this approximation is less accurate. This approximation with impulsive maneuvers is in most cases very accurate, at least when chemical propulsion is used. It is used to determine the mass of propellant required for the given maneuver through the Tsiolkovsky rocket equation.įor multiple maneuvers, delta- v sums linearly.įor interplanetary missions, delta- v is often plotted on a porkchop plot, which displays the required mission delta- v as a function of launch date.įigure 1: Approximation of a finite thrust maneuver with an impulsive change in velocity having the delta- v given by ( 4). The spacecraft's delta- v is the change in velocity that spacecraft can achieve by burning its entire fuel load.ĭelta- v is produced by reaction engines, such as rocket engines, and is proportional to the thrust per unit mass and the burn time. As used in this context, it is not the same as the physical change in velocity of the vehicle.Īs a simple example, take a conventional rocket-propelled spacecraft which achieves thrust by burning fuel. It is a scalar that has the units of speed. JSTOR ( March 2014) ( Learn how and when to remove this template message)ĭelta- v (more known as " change in velocity"), symbolized as ∆ v and pronounced delta-vee, as used in spacecraft flight dynamics, is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such as launching from or landing on a planet or moon, or an in-space orbital maneuver.Unsourced material may be challenged and removed. Please help improve this article by adding citations to reliable sources.
![kerbal space program dv map kerbal space program dv map](https://i.imgur.com/E23eveq.png)
This article needs additional citations for verification.