Keywords | Collocation Node File Formats

Throttle Table File Format (*.throttletable)

A Throttle Table file is an ASCII text file formatted for compatibility with STK that ends in a .throttletable extension. It is a representation of a Throttle Table Engine Model. You can tabulate propulsion data either as values of Power level, Specific Impulse and Thrust, or as Power level, Mass Flow Rate, and Thrust.

Keywords

Each throttle table file contains some common elements called keywords. Keywords and their associated values must precede the specification of the actual data points.

The keywords used in throttle table files are not case-sensitive, and do not have to conform to the case scheme utilized here.

Keyword Required Description
stk.v.<major release number>.<minor release number> Yes

The version of STK software for which the file is formatted to be used. Files can be created in and imported to STK software versions consistent with the file version stamp or higher.

The version stamp must be the first line in the initial guess file.

Example: stk.v.11.7

BEGIN ThrottleTable

END ThrottleTable

 Yes Sets off the beginning and end of the throttle table data, including all other keyword phrases and data point specification (except the version stamp). Refer to any of the sample files included in the Throttle Table Format section for examples.
FormatVersion Yes The version associated with this file format. Currently, the only supported version is 1.0.0
EngineName No

A name for the engine under consideration.

Example: NSTAR

Throttle Table Formats

While the sections above outline the basic format for a data table, the sections below outline the formats used to specify actual data points in the throttle table. The format keyword must be included in the file on its own line, after the header keywords and before the actual data point array.

The following conventions must be observed when specifying data points in any format:

  • Each line contains only one data point.
  • The values on each line must be separated by at least one space.
  • You cannot have multiple points at the same time.

ThrottleLevelPowerIspThrust Format

Individual data points following the ThrottleLevelPowerIspThrust format keyword look like this:

<ThrottleLevel> <ThrusterPower> <Isp> <Thrust>

where

<ThrottleLevel> An integer denoting the throttle level. For an engine with N lines of tabulated data, ThrottleLevel would typically run from 1 to N, with the ThrottleLevel of a line being one more than that of the previous line.
<ThrusterPower> The thruster input power in KiloWatts (kW)
<Isp> The Specific Impulse, in seconds, of the engine at the specified power.
<Thrust> The thrust, in milliNewtons, produced by the engine at the specified power.

ThrottleLevelPowerMFRThrust Format

Individual data points following the ThrottleLevelPowerMFRThrust format keyword look like this:

<ThrottleLevel> <ThrusterPower> <MassFlowRate> <Thrust>

where

<ThrottleLevel> An integer denoting the throttle level. For an engine with N lines of tabulated data, ThrottleLevel would typically run from 1 to N, with the ThrottleLevel of a line being one more than that of the previous line.
<ThrusterPower> The thruster input power in KiloWatts (kW)
<MassFlowRate> The Mass Flow Rate, in mg/s, of the engine at the specified power.
<Thrust> The thrust, in milliNewtons, produced by the engine at the specified power.

Example Files

This is an example .throttletable file in the ThrottleLevelPowerIspThrust format:

	stk.v.11.0
	
	BEGIN ThrottleTable

	FormatVersion    1.0.0

	EngineName       NSTAR

	#Columns ThrottleLevel ThrusterPower(kW) Isp(s) Thrust(mN) 

	ThrottleLevelPowerIspThrust

	15 2.29 3120 92.4 

	14 2.17 3157 87.6 

	13 2.06 3185 82.9 

	12 1.94 3174 78.2 

	11 1.82 3189 73.4 

	10 1.70 3177 68.2 

	9  1.57 3136 63.0 

	8  1.44 3109 57.8 

	7  1.33 3067 52.5 

	6  1.21 3058 47.7 

	5  1.09 3002 42.5 

	4  0.97 2935 37.2 

	3  0.85 2836 32.0 

	2  0.74 2671 27.4 

	1  0.60 2376 24.5 

	0 0.47 1972  20.6 

	END	ThrottleTable

This is an example of the .throttletable file in the ThrottleLevelPowerMFRThrust format:

	stk.v.11.0

	BEGIN ThrottleTable

	FormatVersion    1.0.0

	EngineName       NSTAR

	#Columns ThrottleLevel ThrusterPower(kW) MassFlowRate(mg/s) Thrust(mN)

	ThrottleLevelPowerMFRThrust

	15 2.29 2.86 92.4

	14 2.17 2.77 87.6 

	13 2.06 2.66 82.9

	12 1.94 2.65 78.2

	11 1.82 2.35 73.4 

	10 1.70 2.13 68.2 

	9  1.57 1.86 63.0

	8  1.44 1.79 57.8

	7  1.33 1.63 52.5

	6  1.21 1.51 47.7

	5  1.09 1.40 42.5

	4  0.97 1.28 37.2

	3  0.85 1.09 32.0

	2  0.74 1.09 27.4

	1  0.60 1.02 24.5

	0  0.47 1.07  20.6 

	END	ThrottleTable