## Eclipse Phase | AUSTIN, TEXAS | 2015-2019 A.D.

## Spacecraft Maneuvers

Spacecraft can perform a variety of special maneuvers and operations due to the nature of their movement system and the milieu in which they operate. The following rules apply to all vehicles equipped with Space movement.

**Aerobraking**

Aerobreaking consists of dipping into a planetary atmosphere to shed velocity, the spacecraft’s kinetic energy being converted to heat. This means that less fuel is needed to brake, either decreasing transit time or increasing cargo payload. The vehicle must have a re-entry system in order to aerobrake. The pilot must make a Piloting roll against a Threshold of 2 to keep the craft correctly oriented or suffer one Fire attack as per normal reentry rules. Modifiers due to damage apply in full. For each successful Piloting roll, the craft loses ten percent of its speed. If there is no re-entry system present, one can still aerobrake in the tenuous upper atmosphere for a one percent reduction of speed and only half damage.

**Coasting**

Many of the ships don’t have enough fuel or reaction mass to keep on accelerating throughout a long trip, since some must be kept as combat reserve. Fortunately, a spacecraft will keep moving even if no acceleration is applied. The following formula shows the travel time of a spacecraft based on the amount of Burn Points the captain or pilot is willing to use during the trip. For the sake of simplicity, the actual acceleration time is ignored since it will account for only a short part of the total trip time.

**COASTING**

|1|Travel Time = Distance/Burn Points x 15 x Efficiency)|

|2| Efficlency = Actual Thrust/Drive Section Thrust|

|3|Time is in seconds (Divide by 3600 for the result in hours), Distance is in meters, BPs is the total Burn Points spent|

**Gravity Whip**

The term “gravity whip” is used to describe the manuever by which a planet’s momentum is used to accelerate (or decelerate) a spacecraft. Many space probes used this effect to save fuel and travel time, notably the Voyager space probes. A gravity whip can only be used in an orbital system -the spacecraft gains or loses speed when viewed from the entire system, not the body around which it whips. If the spacecraft is slower than the celestial body, it will accelerate; if faster, it will decelerate.

A Space Navigation Skill test is made against a Threshold equal to the target’s velocity in km/s, divided by ten (round up any fraction). If failed, the spacecraft gains or loses only half the speed it would normally have. If fumbled, the spacecraft misses its orbital rendezvous completely. Find the speed of the vehicle and the orbital speed of the celestial body used (making sure the units of measure are the same). The spacecraft gains twice the difference between its own (pre-whip maneuver) speed and the celestial body’s orbital speed. For example, a spacecraft moving at 5 km/s whips near Jupiter (13 km/s); it gains 2 x (13-5) = 16 km/s, for a final speed of 21 km/s. A revised travel time based on the new speed can then be recalculated if precision is required.

If the spacecraft intersects the orbit at an angle, only its parallel speed vector will be affected. In the interest of playability,the actual equations for calculating the new speed and direction of a spacecraft following a gravity whip are ignored. Those preferring exactitude can find them in any basic astrophysics manual. A game approximation of the new speed can be made by multiplying the spacecraft’s final speed by an angle multiplier. Assume that the greater the angle between the spacecraft’s original trajectory and the celestial body’s, the more the spacecraft’s trajectory will curve. For example, if a ship crosses the orbit of a world at a ninety degree angle, its post-whip trajectory will lie almost parallel to the world’s orbital path.

**Angle Multiplier**

Planet Position |
Angle* |
Multiplier |

Far | 15 | x1.05 |

Average | 30 | x1.1 |

Close | 45 | x1.3 |

*Angle between spacecraft’s trajectory and body’s orbital trajectory

**Hyperthrusting**

Hyperthrusting is a risky maneuver in which the safety parameters of an engine are widely exceeded in order to provide increased thrust. Classic rocket engines can rarely do this, but plasma combustion chambers can greatly increase the available thrust. Such a maneuver is very dangerous since the thrusters may be damaged by overheating, or even explode. It is highly suggested that this rule be allowed only in Cinematic campaigns. (such as ours!)

When hyperthrusting is selected, the engine immediately supplies twice its maximum Overthrust, at a cost of 3 Burn Points for each MP spent. A Piloting Skill test versus a threshold of 50% is required. If failed, the thruster permanently loses a number of MPs equal to the Margin of Failure because of heat damage. Should the total reach -50%, the thruster explodes, causing 1d10 times the Overthrust rating (in MP) worth of damage points to the vehicle.