Deep Space Maneuvers

**Deep space maneuvers** are engine burns done at far distances from Earth. Their purpose is to adjust the trajectory of a rocket, so that it will enter the Sphere of Influence of a targeted body.

## Examples

NASA's *OSIRIS-REx* mission performed deep space maneuvers on its way to asteroid Bennu. In the same way, NASA's *Juno* probe performed deep space maneuvers to get in position for an Earth gravity assist to reach the orbit of Jupiter. JAXA's mission to Venus, *Akatsuki*, failed to get to orbit because of some problems in its fuel tank. It then got to Venus ater 4 TCMs and 5 years of orbiting at heliocentric orbit.

## Principles

Deep space maneuvers are done usually at the furthest or closest point of the orbit (usually aphelion or perihelion) to slightly correct the trajectory to enter the sphere of influence of a celestial body.

Deep space maneuvers don't benefit from the Oberth effect, so the fuel consumption is greater. So, it's important to use them for minor course correction only.

## How to do this?

Such maneuvers are largely used for Venus flybys, in a Mercury return mission. However, they can be used for Moon, Mercury and Earth flybys.

An advantage of Spaceflight Simulator is that you can accelerate time and endure long missions without repercussions.

1. Set target to the celestial body you want to use for gravity assists. Your orbit path must intersect that body.
2. Accelerate time until the rocket gets very close to cross the sphere of influence. This may take patience.
3. When the rocket will get very close to the target, wait until the rocket is positioned at the apoapsis on its orbit.
4. When the rocket is at the apoapsis on its orbit, zoom in and examine the closest approach point (the dashed line). See if the rocket will get there *before* or *after* the target. The dashed line shows where the target will be when the rocket will hit the crossing point between orbits.

### Basic principles

Here are the basic engine burns:

1. If the rocket arrives at orbit crossing point **before** the target and the target is **closer** to the Sun, fire the engines forward.
2. If the rocket arrives at orbit crossing point **after** the target and the target is **closer** to the Sun, fire the engines backward.
3. If the rocket arrives at orbit crossing point **before** the target and the target is **further** to the Sun, fire the engines backward.

Point **after** the target and if the target is **further** to the Sun, fire the engines forward.

### Additional principles

Sometimes, it may not be possible to get to target like this. When you do the engine burns, zoom in and see if the distance to the target is really decreasing. This is important especially when the target is not at the aphelion or perihelion (closest or furthest point to the Sun) of your rocket's orbit. Sometimes, it simply may not be possible to get too close.

Some players try to perform radial engine burns, towards the Sun and away from the Sun. Because you can only influence the height of the opposite point in your orbit, these maneuvers aren't as efficient as burning prograde or retrograde at the apsides.

## High cost maneuvers

These kind of maneuvers are done when a rocket burns a lot of fuel and strongly changes trajectory while in a heliocentric orbit. They are performed when in these situations:

1. A rocket tries to reach the Sun.
2. A rocket failed to reach its target.
3. The astronaut finds out it has not enough fuel and tries to return home.
4. Others (for example, a suicide mission).

## See also

* Advanced Orbital Mechanics
* Aerobrake
* Gravity Assists
* Oberth Effect
* Trajectory Correction Maneuvers