Editing Orbital maneuver (section)

== Propulsion ==
{{unreferenced |section |date=February 2024}}
===Impulsive maneuvers===
[[File:Impulsive maneuver.svg|thumb|Figure 1: Approximation of a finite thrust maneuver with an impulsive change in velocity]]
An '''impulsive maneuver''' is the mathematical model of a maneuver as an instantaneous change in the spacecraft's [[velocity]] (magnitude and/or direction)<ref>{{cite book |doi=10.1016/B978-0-12-374778-5.00006-4 |chapter=Orbital Maneuvers |title=Orbital Mechanics for Engineering Students |date=2010 |last1=Curtis |first1=Howard D. |pages=319–390 |isbn=978-0-12-374778-5 }}</ref> as illustrated in figure 1. It is the limit case of a burn to generate a particular amount of delta-v, as the burn time tends to zero.

In the physical world no truly instantaneous change in velocity is possible as this would require an "infinite force" applied during an "infinitely short time" but as a mathematical model it in most cases describes the effect of a maneuver on the orbit very well.

The off-set of the velocity vector after the end of real burn from the velocity vector at the same time resulting from the theoretical impulsive maneuver is only caused by the difference in gravitational force along the two paths (red and black in figure 1) which in general is small.

In the planning phase of space missions designers will first approximate their intended orbital changes using impulsive maneuvers that greatly reduces the complexity of finding the correct orbital transitions.

=== Low thrust propulsion ===
Applying a low thrust over a longer period of time is referred to as a '''non-impulsive maneuver'''. 'Non-impulsive' refers to the momentum changing slowly over a long time, as in [[electrically powered spacecraft propulsion]], rather than by a short impulse.<ref>{{Cite web |date=2020-10-22 |title=The Propulsion We're Supplying, It's Electrifying - NASA |url=https://www.nasa.gov/humans-in-space/the-propulsion-were-supplying-its-electrifying/ |access-date=2025-01-03 |language=en-US}}</ref>

Another term is ''finite burn'', where the word "finite" is used to mean "non-zero", or practically, again: over a longer period.

For a few space missions, such as those including a [[space rendezvous]], high fidelity models of the trajectories are required to meet the mission goals. Calculating a "finite" burn requires a detailed model of the [[spacecraft]] and its thrusters. The most important of details include: [[mass]], [[center of mass]], [[moment of inertia]], thruster positions, thrust vectors, thrust curves, [[specific impulse]], thrust [[centroid]] offsets, and fuel consumption.