How To...

Define a Finite Maneuver from an Impulsive Maneuver with Astrogator

You can convert an Impulsive Maneuver segment to a Finite Maneuver with the same properties, either manually from an Impulsive Maneuver segment's properties window or automatically as an outcome of a Target Sequence.

Astrogator applies the results of the last run of the impulsive maneuver to each corresponding parameter of the finite maneuver. The results are based on the parameters (including the engine model and thruster set) that you specified for the impulsive maneuver. If you did not specify a duration stopping condition for the finite maneuver, then Astrogator creates one based on the estimated burn duration of the impulsive maneuver. Astrogator adds this new duration stopping condition to the list of stopping conditions. In either case, Astrogator makes all other stopping conditions inactive unless you enable the option to leave other stopping conditions active.

The following is a description of the finite maneuver seeding process and data.Closed

When a finite maneuver is seeded from an impulsive maneuver, Astrogator executes the follow process:

  1. It copies the impulsive maneuver data into the finite maneuver. If you used actual values to define the impulsive maneuver, Astrogator copies those values to the finite maneuver. Otherwise, it copies default values. This data comprises the following:
    • Engine model(s)
    • Thruster set
    • Impulsive Delta-V vector (Cartesian and spherical values)
    • Delta-V vector representation choice (Cartesian or spherical)
    • Quaternion values
    • Euler angle values
    • Attitude type
    • Attitude 'override' choice (from the More Options... window)
    • Attitude lead and trail durations
    • Body Constraint Vector (BCV) values, BCV (selected VGT vector), and BCV sign
    • Engine direction
    • Attitude file path, time offset, and interpolation order
  2. If you did not specify a duration stopping condition for the finite maneuver, then Astrogator creates one using the estimated burn duration based on the impulsive maneuver. Astrogator adds this new duration stopping condition to the list of stopping conditions. In either case, Astrogator makes all other stopping conditions inactive unless you enabled the option to leave other stopping conditions active.
  3. Astrogator normalizes the thrust vector.

To manually seed a Finite Maneuver, take the following steps:

  1. Select a Maneuver segment in the MCS or create a new one.

  2. Set the Maneuver Type as Impulsive, and then set the other parameters, including the engine model and thruster set, as desired.

  3. Run the MCS.

  4. Select the Maneuver segment and click the Seed Finite From Impulsive button. The Maneuver Type will change to Finite, and the other parameters will be configured as explained in the paragraph above.

To seed a Finite Maneuver using a Target Sequence, take the following steps:

  1. Insert a Change Maneuver Type profile as the first target profile for the Target Sequence. Set the Type to change to field to Impulsive.

  2. Insert a Differential Corrector profile after the Change Maneuver Type profile, and target the Maneuver segment to achieve the desired results.

  3. Insert a Seed Finite Maneuver profile after the Differential Corrector profile.

  4. Insert a second Differential Corrector profile after the Seed Finite Maneuver profile, and target the finite burn to achieve the desired results.

  5. Run the MCS. The Target Sequence will calculate the Maneuver segment as an Impulsive maneuver, targeting the desired results, and then define a Finite maneuver from the calculated Impulsive maneuver; finally, the Target Sequence will use the seeded Finite maneuver to achieve the results specified in the second Differential Corrector profile.