# Trajectories¶

Trajectories is a mod that displays trajectory predictions, accounting for atmospheric drag, lift, etc.. See the forum thread for more details.

This addon is not associated with and not supported by the creator of Trajectories.

The Trajectories API is accessed through C# reflection, and is designed for the current version. This means that future Trajectories updates may break this addon, in which case ADDONS:TR:AVAILABLE will return false. It is also possible for future versions of Trjectories to remain fully compatible.

Note

Trajectories only predicts the trajectory of the “Active Vessel,” which is the vessel with the camera focused on it. IMPACTPOS, PLANNEDVEC, SETTARGET, and CORRECTEDVEC will throw exceptions if you try to call them from an inactive vessel or if Trajectories has not calculated an impact position. You should always check if HASIMPACT is true before accessing these suffixes.

For example:

if ADDONS:TR:AVAILABLE {
} else {
PRINT "Impact position is not available".
}
} else {
PRINT "Trajectories is not available.".
}


Trajectories does its calculation based on the vessel’s current orientation. Any tiny change in orientation will change the prediction.

Accuracy is not guaranteed.

See this repository for an example of this addon being used to land a rocket on the launch pad: https://github.com/CalebJ2/kOS-landing-script

## Trajectories Version Compatibility¶

The Trajectories mod went through some changes between Trajectories 1.x and Trajectories 2.x. These changes alter the way that the kOS Trajectories AddOn has to communicate with the Trajectories mod, and added new suffixes that kOS could use. However, for backward compatibility kOS will try to support an older version of Trajectories if that’s what’s installed. Places where a suffx only works with newer versions of Trajectories are noted below in the suffix table.

Access structure TRAddon via ADDONS:TR.

structure TRAddon
Suffix Type Description
AVAILABLE Boolean (readonly) True if a compatible Trajectories version is installed.
GETVERSION String (readonly) (only TR 2.2.0 and up) Trajectories version string.
ISVERTWO Boolean (readonly) True if Trajectories version is 2.0.0 or above.
ISVERTWOTWO Boolean (readonly) True if Trajectories version is 2.2.0 or above.
HASIMPACT Boolean (readonly) True if Trajectories has calculated an impact position for the current vessel.
IMPACTPOS GeoCoordinates (readonly) Returns a GeoCoordinates with the predicted impact position.
PLANNEDVEC Vector (readonly) Vector at which to point to follow predicted trajectory.
PLANNEDVECTOR Vector (readonly) Alias for PLANNEDVEC
SETTARGET(position) None Set Trajectories target.
HASTARGET Boolean (readonly) (only TR 2.0.0 and up) True if Trajectories’ target position has been selected.
TIMETILLIMPACT ScalarValue (readonly) (only TR 2.2.0 and up) Seconds until impact
RETROGRADE Boolean (only TR 2.2.0 and up) Descent profile is retrograde mode.
PROGRADE Boolean (only TR 2.2.0 and up) Descent profile is prograde mode.
CORRECTEDVEC Vector (readonly) Offset plus PLANNEDVEC to correct path for targeted impact.
CORRECTEDVECTOR Vector (readonly) Alias for CORRECTEDVEC
TRAddon:AVAILABLE
Type: Boolean Get

True if a compatible Trajectories version is installed. If this is not true, then none of the other suffixes listed here are safe to call (they can cause error and program crash).

TRAddon:GETVERSION
Type: String Get

Only gives the correct answer for Trajectries version >= 2.2.0

For earlier versions, it gives a hardcoded fixed answer, as follows:

• For any Trajectories version earlier than 2.0.0, this returns the empty string “”.
• For any Trajectories version at least 2.0.0 but below 2.2.0, this returns the ‘rounded off’ answer “2.0.0” regardless of the precise version number within that range.
• If your Trajectories version is at least 2.2.0 or above, this returns the specific version string correctly.

For cases where you need to check for a known minimum Trajectories version, it is probably better to use the specific boolean suffix for that version (for example, TRAddon:ISVERTWO, or TRAddon:ISVERTWOTWO.)

TRAddon:ISVERTWO
Type: Boolean Get

True if the Trajectories mod is at least version 2.0.0 or above.

TRAddon:ISVERTWOTWO
Type: Boolean Get

True if the Trajectories mod is at least version 2.2.0 or above.

TRAddon:HASIMPACT
Type: Boolean Get

True if Trajectories has calculated an impact position for the current Vessel. You should always check this before using impactPos, plannedVect, setTarget, or correctedVect to avoid exceptions.

TRAddon:IMPACTPOS
Type: GeoCoordinates Get

Estimated impact position.

TRAddon:PLANNEDVEC
Type: Vector Get

Vector pointing the direction your vessel should face to follow the predicted trajectory, based on the angle of attack selected in the Trajectories user interface.

TRAddon:PLANNEDVECTOR
Type: Vector Get

Alias for PLANNEDVEC

TRAddon:SETTARGET(position)
Parameters: position – GeoCoordinates None

Sets the Trajectories target landing position to the given position.

TRAddon:HASTARGET
Type: Boolean Get

Did Not Exist in Trajectories before 2.0.0!

If :attr:TRAddons:ISVERTWO is false, using this suffix will cause a runtime error.

The Trajectories Addon can be given a target position on the ground. This is true if such a position is selected, or false if it is not.

TRAddon:TIMETILLIMPACT
Type: Scalar Get

Did Not Exist in Trajectories before 2.2.0!

If :attr:TRAddons:ISVERTWOTWO is false, using this suffix will cause a runtime error.

Gives you Trajectories’ prediction of how many seconds until impact on ground or water.

TRAddon:PROGRADE
Type: Boolean Get/Set

Did Not Exist in Trajectories before 2.2.0!

If :attr:TRAddons:ISVERTWOTWO is false, using this suffix will cause a runtime error.

True if the Trajectories descent profile is set to ‘prograde’ mode. You can set this to have the same effect as clicking on prograde mode in the trajectories GUI. Setting this value to true causes TRAddon:RETROGRADE to become false. (They cannot both be true at the same time.)

TRAddon:RETROGRADE
Type: Boolean Get/Set

Did Not Exist in Trajectories before 2.2.0!

If :attr:TRAddons:ISVERTWOTWO is false, using this suffix will cause a runtime error.

True if the Trajectories descent profile is set to ‘retrograde’ mode. You can set this to have the same effect as clicking on retrograde mode in the trajectories GUI. Setting this value to true causes TRAddon:PROGRADE to become false. (They cannot both be true at the same time.)

TRAddon:CORRECTEDVEC
Type: Vector Get

A vector that applies an offset to PLANNEDVEC intended to correct the predicted trajectory to impact at the selected target position. This vector does not use any aerodynamic prediction and is a very simplistic representation. It is also just a unit vector. It contains no magnitude information about how far off the selected target is from the predicted impact - just the way the offset points. Accuracy is not guaranteed, but it should at least help determine if you need to pitch the nose up or down.

TRAddon:CORRECTEDVECTOR
Type: Vector Get

Alias for CORRECTEDVEC