A spacecraft performs propulsive maneuvers to adjust orbital parameters. There are two categories of such maneuvers: statistical (often called trajectory correction maneuvers (TCMs)), which are usually small and deterministic, which are usually large. When designing a maneuver, the maneuver analyst uses a simplified (impulsive) burn model, but then relies on precision (Category A) software to compute the maneuvers that are sent to the spacecraft in flight. This chapter considers maneuver design and the precision velocity changes are treated in Chap. 8.

Statistical maneuvers are performed to remove the effects of orbit determination and execution errors experienced at previous TCMs or the launch and other small errors, for example, attitude correction maneuvers.

Deterministic maneuvers can be designed that do not change the orbit plane, for example, single-maneuver adjustments, the two-maneuver Hohmann transfer (a fundamental result), and a three-maneuver bi-elliptic transfer. For interplanetary flight, the spacecraft follows a hyperbolic trajectory for escape from the Earth and for approach to the target body or flyby body. For some missions, the gravity-assist technique of navigation can greatly reduce the amount of propellant required to move the spacecraft to the target body as illustrated by 11 mission examples. The patched conics trajectory model uses two-body mechanics in each of four conic segments to describe an interplanetary trajectory. The encounter aiming plane or B-plane is used to aim the interplanetary trajectory so the spacecraft will encounter the target body correctly.

Other maneuvers include orbit insertion maneuvers, which are illustrated by 7 examples, maneuvers that move the spacecraft into another orbit plane, and combined maneuvers, which produce a plane change and in-orbit parameter change as a vector sum of ΔVs.

The “cost” of orbit maneuvers has been measured so far in terms of the ΔV required to implement a trajectory correction maneuver, transfer or adjustment. The final section of this chapter shows how to convert ΔV into the amount of propellant needed by using the Rocket Equation.