Outgassing Events

Top  Previous  Next

The OutgassingEvent object, when used with the Maneuver command or WhileManeuvering command, models the effect of accelerations due to a leaking thruster on a Spacecraft. The accelerations are modeled using an analytic exponential decay model. The OutgassingEvent object specifies the time constant and the minimum magnitude of the burn as a percentage of the initial value, which determine the total duration of the event. The effective magnitude of the force generated by the event is added to the Force Model of the Spacecraft for the duration of the event. OutgassingEvent maneuvers do not deplete mass from the Spacecraft.

 

The sample script below provides an example of modeling an OutgassingEvent in FreeFlyer. The acceleration in this particular case is in the velocity direction of the orbit.

 

OutgassingEvent OutgassingEvent1;

 

OutgassingEvent1.AttitudeSystem   = 1;   // VNB

OutgassingEvent1.BurnDirection = {4e-7, 0, 0}; // km/s2

 

OutgassingEvent1.TimeConstant     = 100; // seconds

OutgassingEvent1.MinimumMagnitude = 0.1; // percent

 

Report OutgassingEvent1.EventDuration.ToMinutes();

 

Maneuver Spacecraft1 using OutgassingEvent1;

 

Note: When maneuvering with an OutgassingEvent, FreeFlyer takes into account the length of the event in the spacecraft propagation. For example, if the OutgassingEvent.TimeConstant property is equal to 100 seconds and the OutgassingEvent.MinimumMagnitude is 0.01% of the initial value, the spacecraft epoch will advance about 460 seconds during the maneuver event.

 

 

Coordinate Systems


The direction of the maneuver can be specified in any of the following attitude reference frames.

Coordinate System

Attitude System

X-Component

Y-Component

Z-Component

International Celestial Reference System (ICRF)

0

GCI X

GCI Y

GCI Z

Velocity-Normal-Binormal (VNB)

1

Velocity

Orbit Normal

Binormal

Local Vertical Local Horizontal (LVLH)

2

Co-Velocity

Negative Orbit Normal

Nadir

Spacecraft Body Fixed

3

Body coordinate X-directed component of maneuver

Body coordinate Y-directed component of maneuver

Body coordinate Z-directed component of maneuver

Geodetic

4

Geodetic X

Negative Orbit Normal

Normal to Earth's surface

UVW

5

U (Position)

V (Along Velocity Direction)

W (Orbit Normal)

RIC

6

R (Position)

I (Along Velocity Direction/"In-Track")

C (Orbit Normal/"Cross-Track")

 

 

See Also


OutgassingEvent Properties and Methods

Maneuver Command