Units

MachUp allows the user to specify the unit of measure for values if they desire. For float values, this is done by making the value a list where the first element is the actual value and the second element is a string specifying the units. For example:

"area" : [6.75, "ft^2"]

For vector inputs, such as position and velocity, the units are simply appended to the vector:

"velocity" : [100.0, 13.0, 0.0, "ft/s"]

For array inputs, such as a density profile or chord distribution, the units are appended as another row in the array:

"rho" : [[0.0, 1.225],
         [2000.0, 1.0066],
         [4000.0, 0.81935],
         ["m", "kg/m^3"]]

When specifying column units in files, these are also appended as another row:

# File: density_profile.csv
0.0, 1.225
2000.0, 1.0066
4000.0, 0.81935
"m", "kg/m^3"

If a given column in an array is unitless (such as span fraction when specifying geometry distributions), “-” should be used as a placeholder.

The following measurements can be defined with the accompanying units:

Measurement	Acceptable Units
Position/displacement/length:	"ft", "m", "in", "cm"
Area:	"ft^2", "m^2"
Velocity:	"ft/s", "m/s", "mph", "kph", "kn"
Angular deflection/position:	"deg", "rad"
Angular rate:	"deg/s", "rad/s"
Density:	"slug/ft^3", "kg/m^3"
Weight/Force:	"lbf", "N"
Moment:	"ft lbf", "Nm"
Units must be given exactly as they appear in this table. Otherwise, MachUpX will not recognize the unit specification.

Except for angular measurements, the first unit listed is the default for “English” units. The second is the default for “SI”. For angular measurements of state and control deflections, as well as airframe geometry, the default is always degrees. For airfoil parameters, measurements may only be expressed in radians. When specifying units in an array and one of the measurements is dimensionless (e.g. span fraction), “-” should be used. Any results generated by MachUpX will be output in the default unit for the given system, regardless of how units were specified for the inputs.