DeltaV

Deltav, often written delta-v or Δv, is a term used in astronautics to denote the amount of velocity a spacecraft must gain or lose to perform a maneuver. It is a scalar measure of velocity change that helps characterize mission requirements irrespective of thruster type or burn duration. Delta-v budgets are used in trajectory planning for phases such as launch, orbital insertion, rendezvous, orbital transfers, and landings, as well as for interplanetary missions.

The theoretical basis for delta-v is the Tsiolkovsky rocket equation: Δv = Isp × g0 × ln(M0/Mf). Here Isp is the specific impulse of the propulsion system, g0 is standard gravity, M0 is the initial mass before a propulsive burn, and Mf is the final mass after the burn. The equation shows that for a given vehicle, higher effective exhaust velocity or a larger propellant mass fraction yields a larger possible delta-v.

In practice, delta-v is used to estimate propellant needs, compare propulsion options, and assess mission feasibility. It is important to note that delta-v is not a measure of thrust or burn time; two missions requiring the same delta-v may have very different propellant masses and thrust profiles.

DeltaV is also the name of Emerson's DeltaV process automation system used in industrial control environments. While related in name, this software is distinct from the spaceflight concept and serves a different domain.