Implementation of Thrust and Mass Propagation

[carlosbislip]

The following error is produced when using FromFunctionThrustMagnitudeSettings and propagating mass through MultiTypePropagatorSettings.

libc++abi.dylib: terminating with uncaught exception of type std::runtime_error: Error when making environment model update settings, could not find ephemeris of body Vehicle

If mass propagation if obviated, effectively passing only TranslationalStatePropagatorSettings , I am able to identify an additional issue through the declaration of various dependent variables.

libc++abi.dylib: terminating with uncaught exception of type std::runtime_error: Error when getting acceleration between bodies, no translational dynamics models by acting on Vehicle are found Abort trap: 6

I traversed through the code and added some terminal printouts in various places in order to compare the problematic items.

spherical_harmonic_gravity acceleration:
nameOfBodyUndergoingAcceleration: Vehicle nameOfBodyExertingAcceleration: Earth aerodynamic acceleration:
nameOfBodyUndergoingAcceleration: Vehicle nameOfBodyExertingAcceleration: Earth thrust acceleration:
nameOfBodyUndergoingAcceleration: Vehicle bodyUndergoingAcceleration: Vehicle accelerationsForBody: Earth : 0x7fcb67c270a8 mach_number_dependent_variable bodyWithProperty: Vehicle > secondaryBody: <---------------- altitude_dependent_variable bodyWithProperty: Vehicle secondaryBody: Earth single_acceleration_norm_dependentvariable accelerationDependentVariableSettings->associatedBody: Vehicle accelerationDependentVariableSettings->secondaryBody_: Earth accelerationModelList.count( bodyUndergoingAcceleration ): 1 bodyUndergoingAcceleration: Vehicle bodyExertingAcceleration: Earth airspeed_dependent_variable bodyWithProperty: Vehicle > secondaryBody: <---------------- total_aerodynamic_g_load_variable bodyWithProperty: Vehicle > secondaryBody: <---------------- single_acceleration_dependentvariable accelerationDependentVariableSettings->associatedBody: Vehicle > accelerationDependentVariableSettings->secondaryBody_:
accelerationModelList.count( bodyUndergoingAcceleration ): 1 bodyUndergoingAcceleration: Vehicle > bodyExertingAcceleration: <----------------

You will see that various items are empty. For instance, the secondaryBody of both _mach_number_dependentvariable and _airspeed_dependentvariable. I am ignorant as to if this is by design within the code. However, I am certain that the accelerations all have to have a body that exerts an acceleration, field for which is empty.

My issues, however, could be due to improper settings. Especially due to the recent TUDAT updates.

EDIT #1: Per Dominic's comment, link to repository that generates this error: HERE

[DominicDirkx]

Hi Carlos,

Could you add a link to the Github repo with the code you are using to generate this?

[carlosbislip]

Hi Carlos,

Could you add a link to the Github repo with the code you are using to generate this?

Done! Added as edit #1. Thanks!

[DominicDirkx]

Hi Carlos,

Try removing all accelerations from your list of dependent variables, and run again. I know you want to save them, but this will help to track down the problem,

Dominic

[carlosbislip]

Followed your suggestion. Trying to propagate mass yields the following:

libc++abi.dylib: terminating with uncaught exception of type std::runtime_error: Error when making environment model update settings, could not find ephemeris of body Vehicle Abort trap: 6

Without mass propagation, the simulation runs to completion. Similar to before, it seems as thrust does not occur.

[DominicDirkx]

Im not sure why you reach the conclusion that there is no thrust. I think the error is caused by the fact that the total_aerodynamic_g_load_variable dependnet variable does not have a secondary body, see:

http://tudat.tudelft.nl/tutorials/tudatFeatures/propagationSetup/propagatorSettingsDependentVariables.html?highlight=total_aerodynamic_g_load_variable#setting-up-dependent-variables

[carlosbislip]

Absolutely right! My thrust issue was elsewhere. However, I am still unable to propagate mass.

[DominicDirkx]

Thr problem with the mass propagation can be solved (-ish), by turning the throw.... of this error into a std::cerr (printing the error, but not terminating the program). Alternatively, it should also work if you use:

    bodyMap[ "Spaceplane" ]->setEphemeris(
                std::make_shared< ephemerides::TabulatedCartesianEphemeris< > >(
                    std::shared_ptr< interpolators::OneDimensionalInterpolator< double, Eigen::Vector6d  > >( ),   "Earth" ) );

What I think is going on is the following:

• When setting up the propagation, the code checks if all required environment models are available.
• The mass propagation requires the current state of the spacecraft
• The current state of the spacecraft requires that either the spacecraft has an ephemeris, or this state is propagated.
• When propagating the mass and state, the state is propagated. However, when making this check for the mass propagation, the code does not know this, resulting in this error.

Either one of the fixes I give above should work. Let me know if it works out,

Best,

Dominic

[carlosbislip]

I implemented the code snippet you provided. I placed it AFTER setting the global frame.

setGlobalFrameBodyEphemerides( bodyMap, "SSB", "J2000" );

Mass is propagated and I can print out the mass-rate dependent variable.

Thanks!

[DominicDirkx]

Great!

For the record, I think I fixed the problem in a 'proper' way, see:

https://github.com/DominicDirkx/tudat/commit/120ad3fcf8e6ce322e2f7e4eda1c65e1cbf4861f

However, I'd suggest leaving well enough alone, and just using the code you have now :)