Setting values in mission file

Any parameter value in the mission file can be provided in several ways:

hard-coded value and unit

The standard way is to set the parameter as value, with or without unit.

Note

If no unit is provided while parameter needs one, SI units will be assumed.

Provided units have to match OpenMDAO convention.

Examples:

altitude:
    value: 10.
    unit: km
altitude:
    value: 10000.   # equivalent to previous one (10km), because SI units are assumed
mach:
    value: 0.8
engine_setting:
    value: takeoff   # some parameters expect a string value

hard-coded value with no unit

When no unit is provided, the value can be “inlined”. As for hard-coded value and unit, if the concerned parameter is not dimensionless, SI units will be assumed.

Example:

mach: 0.8                   # no unit
altitude: 10000.            # == 10 km
engine_setting: takeoff     # string value

OpenMDAO variable

It is possible to provide a variable name instead of a hard-coded value. This variable will be declared as input of the OpenMDAO component.

Unit can be specified. In that case, it will be the unit for OpenMDAO declaration and usage. In any case, the unit for computation will be the internal unit of the segments (SI units). Conversion will be done when needed.

Also, a default value can be specified, which will be the declared default value for OpenMDAO. It has to be consistent with declared unit. If no default value is specified, numpy.nan will be used in OpenMDAO declaration.

Example:

altitude:
    value: data:dummy_category:some_altitude
    unit: ft
    default: 35000.0

As for numeric values, the definition can be inlined if no unit or default value has to be declared:

altitude: data:dummy_category:some_altitude

Using opposite value

Sometimes, it can be convenient to use the opposite value of a variable. It can be done by simply putting the minus sign “-” just before the variable:

delta_mass:
    value: -data:dummy_category:consumed_fuel
    unit: kg
    default: 125.0

Important

The specified default value is for the declared variable, even when the minus sign is used. Therefore, if default value is set as negative and the variable is preceded by a minus sign, the actually used value (if the default value is kept) will be positive.

Contextual OpenMDAO variable

By using the tilda (~) in the variable name, it is also possible to make the variable name contextual according to the hierarchy the defined parameter belongs to.

When a parameter value is defined as prefix~suffix, the actual variable name will be prefix:<mission_name>:<route_name>:<phase_name>:suffix.

It is useful when defining a route or a phase that will be used in several missions (see Mission file).

Note

• <route_name> and <phase_name> will be used only when applicable (see examples below).

• A contextual variable can be defined in a segment, but the variable will still be “associated” only to the phase.

If no prefix is provided (~suffix), the default prefix will be data:mission:.

If no suffix is provided (prefix~), the default suffix will be the parameter name.

It is also possible to have no prefix nor suffix (~). Then the 2 rules above apply.

Example

routes:
  route_A:
    range: ~distance                # Example #1: here the suffix is customized.
    parts:
      - phase_a
      - ...

phases:
  phase_a:
    thrust_rate: ~                  # Example #2: default prefix and suffix will be used
    time_step: settings:mission~    # Example #3: Here the prefix is customized

missions:
  mission_1:
    parts:
      - ...
      - route: route_A
      - ...
  mission_2:
    parts:
      - ...
      - phase: phase_a
      - ...

Example 1

route_A contains the parameter range where a contextual variable name is affected, that will use the default prefix (data:mission:) and the customized suffix (distance).

route_A is used as a step by both mission_1 and mission_2.

Then the mission computation has among its inputs:

Variable names

#	Prefix	Hierarchy	Suffix	Full name
1	data:mission	mission_1:route_A	distance	data:mission:mission_1:route_A:distance
1	data:mission	mission_2:route_A	distance	data:mission:mission_2:route_A:distance

Examples 2 & 3

phase_a contains the parameters thrust_rate and time_step where contextual variable names are affected. For thrust_rate, default prefix (data:mission:) and suffix (thrust_rate) will be used. For time_step, prefix is customized (settings:mission) and default suffix (time_step) will be used.

phase_a is used as a step by route_A, that is used as a step by mission_1. phase_a is also used as a step directly by mission_2.

Then the mission computation has among its inputs:

Variable names

#	Prefix	Hierarchy	Suffix	Full name
2	data:mission	mission_1:route_A:phase_a	thrust_rate	data:mission:mission_1:route_A:phase_a:thrust_rate
2	data:mission	mission_2:phase_a	thrust_rate	data:mission:mission_2:phase_a:thrust_rate
3	data:settings	mission_1:route_A:phase_a	time_step	data:settings:mission_1:route_A:phase_a:time_step
3	data:settings	mission_2:phase_a	time_step	data:settings:mission_2:phase_a:time_step