Digital Mission Engineering (DME): Hypersonics and EOIR (Part 2 of 4)

STK Premium (Air) or STK Enterprise
You can obtain the necessary licenses for this tutorial by contacting AGI Support at support@agi.com or 1-800-924-7244.

Required Capability Install: This lesson requires an additional capability installation for STK EOIR. The EOIR install is included in the STK Premium software download, but requires a separate install process. Read the Readme.htm found in the STK install folder for installation instructions. You can obtain the necessary install by visiting https://support.agi.com/downloads or calling AGI support.

The results of the tutorial may vary depending on the user settings and data enabled (online operations, terrain server, dynamic Earth data, etc.). It is acceptable to have different results.

If you have not completed Part 1 of the DME lessons, a starter scenario is provided. It requires STK 12 or newer to open. The DME lessons are in the Training - Level 3 - Focused tutorials section of the STK Help.

Capabilities covered

This lesson covers the following STK ;capabilities:

  • STK Pro
  • Aviator
  • Aviator Pro
  • Analysis Workbench
  • Electro-Optical Infrared Sensor Performance (EOIR)

Problem statement

Across the industry, the digital engineering process is becoming more complex. Systems of systems are changing and updating in different stages of the mission life cycle. In this series, you will address these challenges by creating a fully connected digital thread with a common mission environment at the core. You will design and test a new satellite constellation for persistent, stereo coverage of hypersonic vehicles across the world. You will address this topic in stages: satellite constellations, hypersonic flight, EOIR sensors, communications links, and triggering events and systems. The vision is to integrate the mission environment and operational objectives into the digital thread early and throughout the entire product life cycle. Through digital mission engineering, you are now capable of quickly evaluating the overall mission impact of the smallest change to any component. This session will advance to the detailed engineering phases where you will demonstrate how to incorporate higher-fidelity, third-party models of sensors and vehicle heat signatures into the mission model and understand the respective analytical results.

Solution

In this section of the DME series, you will focus on using externally created CFD results to populate the performance model of an aircraft and its thermal signature for use with STK's Aviator and EOIR capabilities, respectively.

What you will learn

Upon completion of this tutorial, you will be able to create the following:

  1. Experience building new vehicle profiles in STK's Aviator Pro capability.
  2. Design a flight in Aviator.
  3. Practice comparing results at varying levels of fidelity.
  4. Build an EOIR sensor and tracking an object.
  5. Gain experience loading in external files from other tools.

External files

  • DME_Session2_Starter_Aviator_EOIR.vdf - This is the starter scenario for this lesson.
  • X-43.mdl - This is the custom aircraft model.
  • X-43_ANSYS_CFD.aero - This is an external file generated by AGI with ANSYS Fluent® fluid simulation software of the hypersonic vehicle's computational fluid dynamics.
  • x-43_eoir_v03.obj - This is a thermal model for the hypersonic vehicle.

These files are available for download from the STK Data Federate. The file path is AGI > Document Library > STK 12 > Starter Tutorials > DME_Session2_Hypersonics and EOIR in the Operational Environment.

Video guidance

Watch the following video. Then follow the steps below, which incorporate the systems and missions you work on (sample inputs provided).

Opening the starter scenario

AGI has built a starter scenario for you that contains the flight and the Pegasus hypersonic vehicle. You can open the scenario from the SDF or from a local copy you downloaded from the SDF.

Choose one of the three methods below to open a starter scenario.

Signing in to access the SDF

You can access your scenarios or objects from the STK Data Federate (SDF).

  1. Click Open a Scenario () in the Welcome to STK dialog box.
  2. Change the Location to STK Data Federate at the bottom of the Open dialog window.
  3. Click Guest in the top-right corner to sign into your account.
  4. Click Switch User... when the SDF Server Login dialog box opens.
  5. Enter your Account name and Password on the Log In: AGI SEDS dialog box.
  6. Click Log In.

Option 1: Opening a starter scenario from the SDF - use the Browse method

If you want to open the starter scenario from the SDF, you can open it by browsing to the VDF file.

  1. Select the Browse tab.
  2. Go to Sites/AGI/documentLibrary/ STK 12/Starter Tutorials/DME_Session2_Hypersonics and EOIR in the Operational Environment.
  3. Select DME_Session2_Starter_Aviator_EOIR.vdf.
  4. Click Open.

When the scenario loads, ensure the HXLV_Pegasus aircraft is in the scenario. The aircraft contains the notional aerodynamics model from ANSYS.

Option 2: Opening a starter scenario using the URL

If you want to open the starter scenario from the SDF, you can open it by copying and pasting the VDF's URL.

  1. Copy the following URL: https://sdf.agi.com/share/page/site/AGI/document-details?nodeRef=workspace://SpaceStore/d3668deb-fdc1-419f-ad26-b22d46422859
  2. Right-click in the File name field.
  3. Select Paste.
  4. Select DME_Session2_Starter_Aviator_EOIR.vdf.
  5. Click Open.

When the scenario loads, ensure the HXLV_Pegasus aircraft is in the scenario. The aircraft contains the notional aerodynamics model from ANSYS.

Saving your scenario

First you want to save your scenario. The way to save your scenario varies slightly depending if you opened the starter scenario from the SDF or from a local file.

Choose the appropriate save method below based on how you opened the starter scenario.

Option 1: Saving your scenario after opening it from the SDF

If you opened the starter scenario from the SDF, follow the steps below to save your scenario.

  1. Click File on the menu bar.
  2. Select Save As...
  3. Click the STK User folder in the Navigation Pane of the Save As dialog.
  4. Select the DME_Session2_Starter_Aviator_EOIR folder.
  5. Click Open.
  6. Change Save as type to Scenario Files (*.sc).
  7. Ensure the File name is DME_Session2_Starter_Aviator_EOIR.sc.
  8. Click Save.
  9. Click Yes. to replace the existing file.

Option 2: Saving your scenario after opening it from a local file

If you opened the starter scenario from a local file, follow the steps below to save your scenario.

  1. Click File on the menu bar.
  2. Select Save As...
  3. Click the STK User folder in the Navigation Pane of the Save As dialog.
  4. Click New Folder.
  5. Name it DME_Session2_Starter_Aviator_EOIR.
  6. Select the DME_Session2_Starter_Aviator_EOIR folder.
  7. Click Open.
  8. Ensure the Save as type is Scenario Files (*.sc).
  9. Set the File name to DME_Session2_Starter_Aviator_EOIR.sc.
  10. Click Save.

Modeling a hypersonic flight and evaluating sensor responses with EOIR

You will recreate NASA's 2004 X-43 Hypersonic test flight path using ANSYS Fluent–generated performance characteristics. You will also incorporate test range assets and evaluate how well they should be able to monitor the flight based on the thermal signature also provided by the CFD analysis.

The original X-43 test was composed of several procedures that you will include in your Aviator mission. The mission begins with a B-52 aircraft carrying the combined launch vehicle and hypersonic test vehicle. The B-52 takes off from Naval Base Ventura County - Point Mugu and flies out to the Point Mugu Sea Range. Once the B-52 has entered the test region, it releases the modified Pegasus launch vehicle known as the Hyper-X Launch Vehicle (HXLV). This launch vehicle accelerates the X-43 Hyper-X Research Vehicle (HXRV) to Mach The ratio of the aircraft's speed and the speed of sound at the aircraft's altitude, with local atmospheric conditions. 9 and an altitude of 110,000 ft before separating. At that point, the X-43 conducts a short test of the scramjet to maintain velocity before finally gliding down to the sea. You will use the lift and drag coefficients found with computational fluid dynamics CFD) to define how the vehicle behaves over the flight envelope.

Once you've modeled the flight path, you will switch your focus to evaluating various sensor responses with EOIR based on the thermal signature, again from the CFD runs. This will tell you how well the test assets will be able to monitor the test mission as it progresses.

Inserting an Aircraft object

You can model the hypersonic vehicle by using an aircraft object.

  1. Bring the Insert STK Objects tool () to the front.
  2. Insert an Aircraft object () using the Define Properties () method.
  3. Set the Propagator to Aviator.
  4. Click the Select Aircraft () icon.
  5. Right-click on User Missile Models.
  6. Select New Item.
  7. Rename the new missile "X-43".
  8. Click OK.
  9. Click Apply.

Handling the flight path warning

Aviator performs best in the 3D Graphics window when the surface reference of the globe is set to Mean Sea Level. You will receive a warning message when you apply changes or click OK to close the properties window of an Aviator object with the surface reference set to WGS84. It is highly recommended that you set the surface reference as indicated before working with Aviator.

  1. When the Flight Path Warning dialog opens, click Optimize STK for Aviator .
  2. Click OK.

    3. The reason you are using the Missile Model is this is a unique Hypersonic Vehicle in that it is mainly a Gliding Hypersonic Vehicle. Depending on the application, you may want to model the hypersonic vehicle as an aircraft.

Setting hypersonic properties

You can begin by designing the hypersonic vehicle. Define the performance models by assigning the upper limit to the altitude and speed of the vehicle. The vehicle flies around 100,000 feet, but may raise a bit above that value. The value just provides a tolerance value. The same can be said about the Mach number. Even though this aircraft flies at Mach 10, it is closer to Mach 9.6-9.7.

  1. Click the Aircraft Properties () icon.
  2. Ensure the Performance Models tab is selected.

Level Turns

  1. Locate the Level Turns field.
  2. Set the Max Load Factor to 15 G-SeaLevel.
  3. Select Scale by Atmosphere density from the drop-down menu.

Cruise

  1. Locate the Cruise field.
  2. Set the Max Airspeed to Mach 10.
  3. Set the Default Cruise Altitude to 110000 ft.

Descent

  1. Locate the Descent field.
  2. Set the Airspeed to Mach 10.

3D Model

  1. Locate the model field.
  2. Click the ellipsis () to browse to the location of X-43 model file. If the file has not been downloaded, you can search for and load it in from the STK Data Federate.
  3. Select x-43.mdl.
  4. Click Open.
  5. Click Save.

Setting aerodynamic properties

You can set the aerodynamics properties of the aircraft. The values were disclosed in the public NASA papers and schematics on the x-43.

  1. Select the Aerodynamics tab.
  2. Set the following options:
    3. Option Value
    Reference Surface Area 43 ft^2 (3.99483 m^2)
    Cl Max 0.085
    Cd 0.015
    Calculate AOA On
    Max AOA 20 deg

    The angle of attack The angle between the body X axis and the projection of the velocity vector onto the body XZ plane. The velocity vector is the velocity of the object as observed in the object's central body fixed coordinate system. change is to add tolerance. It is the max AOA based on certain Cl curves that were made publicly available.

  3. Click Save.

Reviewing the Propulsion tab

You won't make any changes to the Propulsion tab, but take a look at the settings.

  1. Click the Propulsion tab.
  2. Review the settings.
  3. Click Save.

Adjusting the Thermal tab settings

STK v12.1 or newer provides new thermal performance models to support the design and operations of hypersonic vehicles and related defensive systems. These models, based on the NASA TFAWS analysis, employ a variety of techniques to determine heat flux, heat load, and wall temperatures for any Aviator trajectory. These new thermal performance models can also interface directly with CFD models. This is key for both vehicle design and the analysis of offensive and defensive systems and tactics, where aerodynamic heating plays a significant role in the vehicle signature.

  1. Click the Thermal tab.
  2. Review the settings. The Strategy being used is a Basic Thermal model using the Sutton Graves Heat Flux. Users with their own model can plug it in here.
  3. Modify the Heat Flux Model Params - Leading Radius by setting the value to 1 cm (0.01 m). This will model a sharp leading edge.
  4. Click Save.
  5. Click Close.

Updating the Mission Window

You have defined the performance model, but before you start designing the flight, you should update the Mission Window. Use the Mission Window to define the aircraft's route when Aviator has been selected as the propagator. You want to know what the Mach number is throughout the flights. Add that next.

Mission Window

  1. Right-click in the Mission Profile Window.
  2. Select Profile Options/Properties.
  3. Select the Secondary Y Axis checkbox.
  4. Click Mach # to select it.
  5. Click OK.

    6. The Mission Profile Window now displays an additional Y axis.

  6. Click Apply.

Designing the X-43 flight

You created the flight profile and can begin designing the flight. This test flight involved a B-52 carrying a modified Pegasus rocket with the X-43 strapped to the front. Due to this, there are a few settings that you need to set to recreate this mission.

The first part is to attach the modified Pegasus launch vehicle. During the test it was referred to as the Hyper-X Launch Vehicle (HXLV).

  1. Right-click on Phase 1.
  2. Select the Insert First Procedure for Phase () icon.
  3. Allow the Calculation Progress to finish.
  4. Select the STK Vehicle site.
  5. Select the HXLV_Pegasus in the Link To field.
  6. Click Next >.

Setting a Vector Geometry Tool point

  1. Select VGT point ().
  2. Set the following:
    3. Option Value
    Name AttachedToHXLV
    Start Time 1.000 EpSec

    The one second is due to Aviator's interpolation. Aviator needs at least 0.5 seconds of simulation time.

  3. Click the ellipsis () beside Formation Point.
  4. In the Formation Point section, select the HXLV_Pegasus HXRV_X43_LaunchLocation in the Select Position Point window. This is custom point off the body of the vehicle.
  5. Click OKto close the Select Position Point window.

Setting the Duration

  1. Set the Duration to 1500 sec (0.416667 hr).
  2. Select the Use Max PointStopTime (no error if <= Duration) checkbox.
  3. Set the Fuel Flow Source to Override.

    4. By default, Aviator attempts to expend the fuel even if this object is attached. During the test, the X-43 only expended its fuel during the time it was at approximately Mach 10 while attempting to maintain the Hypersonic speed that was achieved by the HXLV.

  4. Set the Override Fuel Flow to zero (0) lb/hr. This number is because it is attached to the vehicle.
  5. Set the Flight Mode to Forward Flight - Cruise.
  6. Set the Display Step Time to 0.1 sec.
  7. Click Finish.

Setting the custom time

  1. Double-click Start:1.000 in the procedure.
  2. Select the Set Interrupt Time checkbox.
  3. Select Time Component from the drop-down menu.
  4. Select HXLV_Pegasus in the left column and DeployFromPegasus from Time Instants. This is a custom time to model the aircraft's attachment. This is to model the approximate time at which the charges were set off that released the X-43 from the HXLV.
  5. Click OK in the Select Time Instance window.
  6. Click OK in the AttachedToHXLV Time window.
  7. Click Apply.
  8. Save () the scenario.

Inserting an Ejection procedure

Within Aviator, there isn't a direct way of modeling an ejection of one aircraft from another. Instead, you can represent this stage with a duration of 2.5 seconds of ejection time.

  1. Right-click on the STK Vehicle Site.
  2. Click the Insert Procedure After () icon.
  3. Click the End of Previous Procedure () icon.
  4. Click Next >.

Defining the Ejection Maneuver

  1. Select the Basic Maneuver () option.
  2. Set the name to Ejection.
  3. Set the Basic Stop Conditions Time of Flight to 00:00:02.500 HMS.
  4. Disable the following options:
    • Fuel State
    • Downrange
  5. Ensure the Strategy is set to Straight Ahead.

Defining the Vertical/Profile strategy

  1. Select the Vertical/Profile tab.
  2. Set the following options:
    3. Option Value
    Strategy Autopilot - Vertical Plane
    Mode Specify Altitude Change
    Relative Altitude Change 100 ft
    Control Altitude Rate 2400 ft/min
  3. Locate the Control Limits section.
  4. Select Specify Max Pitch Rate from the drop-down menu.
  5. Set the following options:
    6. Option Value
    Specify Max Pitch 10 deg/sec
    Damping Ratio 2
    Airspeed Maintain current airspeed
    Maintain Airspeed type TAS True Airspeed: the speed that the aircraft is moving relative to the airmass that it is flying in.

Defining the Attitude, Performance, and Fuel controls

  1. Select the Attitude/Performance/Fuel tab.
  2. Set the Fuel Flow Source to Override.
  3. Set the Override Fuel Flow to zero (0) lb/hr. The X-43 at this point is ejected via a release controller on the Pegasus.
  4. Click Finish.
  5. Click Apply.
  6. Save () the scenario.

Modeling Fuel Off Performance PreScram

This is the phase where you can model the PreScram measurement phase of the x-43. This is when the vehicle took in data for approximately three (3) seconds before beginning the actual hypersonic gliding process.

  1. Right-click on the Ejection procedure.
  2. Click the Insert Procedure After () icon.
  3. Click the End of Previous Procedure () icon.
  4. Click Next >.

Defining the Fuel Off Performance PreScram maneuver

  1. Select the Basic Maneuver () option.
  2. Set the name to Fuel Off Performance PreScram.
  3. Set the Basic Stop Conditions Time of Flight to 00:00:03.000 HMS.
  4. Disable the following options:
    • Fuel State
    • Downrange

Defining the navigation direction

  1. Set the following options in the Horizontal/Navigation tab:
    2. Option Value
    Strategy Fly AOA
    Roll No Roll
    AOA 6 deg

    From the public data, the X-43 maintained an AOA of six (6) degrees, which you just modeled.

  2. Set the Airspeed to Maintain current airspeed.

Defining the Attitude, Performance, and Fuel controls

  1. Select the Attitude/Performance/Fuel tab.
  2. Set the Flight Mode to Forward Flight - Cruise.
  3. Set the Fuel Flow Source to Override.
  4. Set the Override Fuel Flow to zero (0) lb/hr. It is a glider and currently using Pegasus' energy.
  5. Click Finish.
  6. Click Apply.
  7. Save () the scenario.

Modeling the Hypersonic phase

  1. Right-click on the Fuel Off Performance PreScram.
  2. Click the Insert Procedure After () icon.
  3. Click the End of Previous Procedure () icon.
  4. Click Next >.

Defining the hypersonic maneuver

  1. Select the Basic Maneuver () option.
  2. Set the name to Hypersonic.
  3. Set the Basic Stop Conditions Time of Flight to 00:00:11.000 HMS.
  4. Disable the following options:
    • Fuel State
    • Downrange

The vehicle doesn't technically use fuel unless it is in the hypersonic phase. It cannot get to hypersonic, but can only maintain and glide. This is where you are burning all the fuel the hypersonic vehicle has within it to maintain the hypersonic speed the HXLV has brought to it. You can set the throttle to 100% because there was no throttling on the glider to control this.

Defining the navigation direction

  1. Set the following options in the Horizontal/Navigation tab:
    2. Option Value
    Strategy Fly AOA
    Roll No Roll
    AOA 6 deg
    Airspeed Accel/Decel using Aero/Propulsion with Throttle setting
    Throttle 100%

Defining the Attitude, Performance, and Fuel controls

  1. Select the Attitude/Performance/Fuel tab.
  2. Set the Flight Mode to Forward Flight - Cruise.
  3. Ensure the Fuel Flow Source is set to Cruise Perf Model.

    4. This stage is where the hypersonic phase is active. You want to use the fuel, which is why you are not setting the fuel flow source to override.

  4. Click Finish.
  5. Click Apply.
  6. Save () the scenario.

Modeling the deceleration phase

  1. Right-click on the Hypersonic procedure.
  2. Click the Insert Procedure After () icon.
  3. Click the End of Previous Procedure () icon.
  4. Click Next>.

Defining the deceleration maneuver

  1. Select the Basic Maneuver () option.
  2. Set the name to Deceleration.
  3. Set the Downrange option to 500 nm. This is an arbitrary distance.
  4. Disable the following options:
    • Fuel State
    • Time of Flight

Defining the navigation direction

  1. Ensure you are in the Horizontal/Navigation tab.
  2. Set the following options:
    3. Option Value
    Strategy Fly AOA
    Roll No Roll
    AOA 6 deg
    Airspeed Accel/Decel using Aero/Propulsion with Throttle setting
    Throttle 0%
    Min Speed Limit Ignore Limits
    Max Speed Limit Ignore Limits

Defining the Attitude, Performance, and Fuel controls

  1. Select the Attitude/Performance/Fuel tab.
  2. Set the Flight Mode to Forward Flight - Descend.
  3. Set the Fuel Flow Source to Override.
  4. Set the Override Fuel Flow to zero (0) lb/hr.
  5. Click Finish.
  6. Save () the scenario.

    7. The Profile Window should look similar to this:

    3D View: Hypersonic flight window

  7. Click OK.
  8. Rename the aircraft X43_Notional.

Viewing the flight in the 3D Graphics window

Take a look at the flight in the 3D Graphics window.

  1. Set the Scenario Time Period to 1000.282 EpSec. This is the time the Hypersonic vehicle separates from the Pegasus.
  2. Zoom To the X43_Notional () in the 3D Graphics window.
  3. Animate () the scenario to watch the flight.
  4. Pause () the animation when complete.
  5. Save () the scenario.

    6. 3D View: Hypersonic flight

Examining the flight

The hypersonic flight was initially created with a low-fidelity performance model. You can now compare it to the performance model based on the CFD data generated with ANSYS tools. This data is generated by running the X-43 in ANSYS Fluent at various stages throughout the flight envelope, varying velocity and angle of attack. From the CFD analysis, you were able to obtain the Coefficient of Lift (Cl) and Coefficient of Drag (Cd) values associated with each pair of AOA and velocity. With those values, you were able to construct the performance profile for this vehicle.

Generating a Downrange vs Altitude graph

  1. Extend the Analysis menu.
  2. Open the Report & Graph Manager ().
  3. Set the Object Type to Aircraft.
  4. Select X43_Notional from the list of objects.
  5. Click the Create new graph style () icon.
  6. Set the Name to DownrangeVsAlt.
  7. Click Enter.

Defining the axes

  1. Set the Graph Type to XY.
  2. Expand the Flight Profile by Time directory.
  3. Set the X Axis to Downrange.
  4. Set the Y Axis to Altitude.
  5. Click OK.

Generating the graph

You can generate the data for more than one flight. To do this, you can select both aircraft objects from the list.

  1. Multiselect the X43_Notional and HXRV_X43 from the list of aircraft.
  2. Generate the DownrangeVsAlt graph.
  3. Examine the data and note the similarities and differences.

    4. 3D View: Hypersonic flight window

The X-43 flights (X43_Notional and HXRV_X43) have the same behavior, especially in the Hypersonic phase. The differences begin after the hypersonic phase. Both the CFD model (HXRV_x43) and the notional hypersonic model (X43_Notional) leverage the same aerodynamic specs of the hypersonic glider. The biggest difference is that the notional model uses internal physics to model the Cl and Cd of the aircraft. This is a general approximation of the flyout of the hypersonic vehicle. However, the CFD data provides a more accurate representation of the Cl and Cd of the aircraft.

Generating the thermal summary

STK v12.1 or newer provides thermal performance models to support the design and operations of hypersonic vehicles and related defensive systems. The X-43 thermal model from the initial setup can be reported on. If a hypersonic vehicle goes high and fast enough, you will see that the vehicle doesn’t get very warm on the boost, but gets very hot on the reentry. The more speed you add where the air is thin or nonexistent on the boost, the hotter it will get on reentry. For a depressed trajectory, the vehicle might get pretty hot during boost. It all depends on how much air there is, how fast the vehicle is moving, and the reference area of the leading edge.

It is important to model a system's thermal signature because it is of extreme interest to engineers and operators for both offensive and defensive systems. Lots of effort is being expended throughout the market on thermal environment effects for hypersonic vehicles. This feeds into signature analysis. Structures and signatures and the areas those aspects drive are where a lot (if not most) of the money goes for both offensive and defensive systems. The ability to model this in STK, and move to the EOIR thermal models, makes it clear as to how detectable and, therefore, vulnerable a given trajectory is, and provides key measures for building these vehicles. Examine these parameters of your own hypersonic notional flight.

  1. Open the Report & Graph Manager ().
  2. Set the Object Type to Aircraft.
  3. Select X43_Notional from the list of objects.
  4. Click the Create new graph style () icon.
  5. Set the Name to HeatFlux.
  6. Click Enter.

Defining the axes

  1. Set the Graph Type to XY.
  2. Expand the Flight Profile by Downrange data provider group.
  3. Set the X Axis to Downrange.
  4. Set the Y Axis to Thermal Model Heat Flux.
  5. Click OK .

Defining the Head Load and Wall Temperate graphs

The Heat Load and the Wall Temperature are vital to know when modeling a hypersonic flight.

  1. Repeat the steps above to create graphs with the Thermal Model Heat Load and the Thermal Model Wall Temperature on the Y Axis.
  2. Rename the new graphs HeatLoad and WallTemp, respectively.

Generating the graphs

  1. Select the X-43_Notional from the list of aircraft.
  2. Generate the HeatFlux, HeatLoad, and the WallTemp graphs.
  3. Click OK on the Down Range Parameters dialogs as the graphs are generating.
  4. Examine the data and note the increase in temperature as the Notional X-43 is ejected and reaches hypersonic speeds. When measuring the Wall Temperature, the temperature reaches ~3000 K. This will be relevant information when you examine a thermal infrared camera's ability to image this target.

Analyzing the mission with EOIR

The flight is modeled and is being monitored by multiple systems around it. You can examine how a satellite tracks and views the hypersonic in flight. Using EOIR, you can build and analyze how well a system on board a satellite would be able to image the hypersonic vehicle. Later you can examine how a UAV nearby would image the same target.

You can start by inserting a single satellite, not the full constellation from session 1. Because for the scope of this study, you just want to understand how well the system on board the satellite is able to image the X-43.

  1. Bring the Insert STK Objects tool () to the front.
  2. Insert a Satellite () using the Define Properties () method.
  3. Set the following options:
    4. Option Value
    Semi-major Axis 8112.14 km
    Eccentricity 0
    Inclination 50 deg
    Argument of Perigee 0 deg
    RAAN 0 deg
    True Anomaly 60 deg
  4. Click OK.
  5. Rename the satellite LEOSat.

This is just one satellite from the constellation that you will use to detect the X-43.

Inserting a Sensor object

  1. Using the Insert STK Objects tool, insert a Sensor () object using the Insert Default method.
  2. When the Select Object window appears, select the LEOSat in the list and click OK.
  3. Rename the sensor "Imager".

Defining the sensor

Now that you have the sensor object in the scenario, define its properties.

  1. Open the Imager's () Properties ().
  2. Go to the Basic - Pointing page.
  3. Set the Pointing Type to Targeted.
  4. Move () HXRV_X43 to the Assigned Targets field.

    5. This object has a predefined EOIR thermal model you can use.

  5. Click Apply on the properties.
  6. Save () the scenario.

Setting EOIR Spatial parameters

Set the EOIR spatial parameters for the sensor.

  1. Select the Basic - Definition page.
  2. Set the Type to EOIR.
  3. Select the Spatial tab.
  4. Set the following field-of-view options:
    5. Option Value
    Horizontal Half Angle 0.002 deg
    Vertical Half Angle 0.002 deg
  5. Set the following number-of-pixels options:
    6. Option Value
    Horizontal 1000
    Vertical 1000
  6. Click Apply.
  7. Save () the scenario.

Setting EOIR Spectral parameters

The Spectral tab enables you to set the spectral band wavelengths. This study analyzes the Mid-wavelength infrared (3-5.5μm) otherwise known as the thermal infrared. This band enables you to narrow down the infrared signature of the hypersonic vehicle designed earlier in the lesson.

  1. Select the Spectral tab.
  2. Set the following Spectral Band Edge Wavelengths options:

    3. Enter the high number first, to keep all values within the limits.

    Option Value
    High 5.5 μm
    Low 3.0 μm
  3. Click Apply.
  4. Save () the scenario.

Setting EOIR Optical parameters

On the Optical tab, you can set the Image Quality and the Optical Transmission. When you set the two optical inputs, the third is automatically calculated for you.

  1. Select the Optical tab.
  2. Set the following options:
    3. Option Value
    Input Focal Length and Entrance Pupil Diameter
    Effective Focal Length 415.00 cm
    Entrance Pupil Diameter 100.00 cm
    Image Quality Negligible Aberrations
  3. Leave the Optical Transmission and Diffraction Wavelength as the defaults.
  4. Click Apply.
  5. Save () the scenario.

Setting EOIR Radiometric parameters

The Radiometric tab enables you to define the radiant energy measurement properties. At a high level, the sensitivity defines the noise floor of the sensor.

  1. Select the Radiometric tab.
  2. Ensure the Input to High Level.
  3. Leave all other parameters as the defaults.
  4. Click OK.
  5. Save () the scenario.

Examining the EOIR settings for the hypersonic vehicle

The sensor is now defined, and you can see the thermal model of the hypersonic vehicle. The EOIR configurations have already been designed for the HXLV_X43. This was modeled in the starter scenario.

  1. Open HXRV_43's () Properties ().
  2. Select the Basic - EOIR Shape tab.
  3. Ensure the Shape is set to CustomMesh.
  4. Ensure the Max Dimension is set to 30m.
  5. Confirm the Mesh File is set to x-43_eoir_v03.obj.
  6. Ensure the Material Specification is set to Geometric Groups.
  7. Examine the Material Elements and confirm the following values:
    8. Material Elements Temperature
    TopFront 2931 K
    TopBack 3114 K
    Stab_Vert_Outside 3041 K
    Stab_Vert_Inside 3114 K
    Stab_Horiz_Top 3078 K
    Stab_Horiz_Btm 3078 K
    Outlet 3030 K
    LeadingEdge 3188 K
    Intake 2894 K
    Inlet 3151 K
    Exhaust 2600 K
    BottomFront 2790 K
    BottomCenter 3041 K
    BottomBack 3041 K

    These values were generated from ANSYS Fluent with the CFD results. The custom mesh you are designing is for the actual aircraft object itself. If you wanted, you could also model the plume coming from the vehicle to add another dimension on the sensor scenes that would be generated.

  8. Do not change any of the parameters.
  9. Click OK.
  10. Save () the scenario.

Setting up a target object

In the EOIR Target Configuration panel, you can select STK objects to use in the generated sensor scene. You can add the HXLV_X43 to the list of objects. If the EOIR toolbar is not visible, then open the View - Toolbars menu and enable the EOIR option.

  1. Open the EOIR Target Configuration ().
  2. Move () the Aircraft/HXRV_X43 to the Selected Target field.
  3. Click OK.
  4. Save () the scenario.

Generating a sensor scene

EOIR can create an image of what the system on the LEOSat would see. This sensor is tracking the hypersonic vehicle. You can jump to a moment in the scenario when the hypersonic vehicle is in view.

  1. Set the scenario time to 1200 EpSec. This is the time where the satellite is overhead of the test flight.
  2. Select the Imager ().
  3. Click the EOIR Sensor Scene () icon. STK might take a few moments to generate the sensor scene.
  4. Use the scroll bars and the middle scroll of the mouse to resize the view.

    5. EOIR sensor Scene: Hypersonic flight

The HXRV_43 is approximately ~3500 km away at this point in time. This explains the low resolution of the sensor scene.

Changing the visual details

  1. Right-click in the Sensor Scene window.
  2. Select the Details option.
  3. Set the Color Map to BGRY as the EOIR Scene Visual Details.
  4. Click OK.

    5. EOIR sensor Scene: Hypersonic flight BGRY

  5. Close the sensor scene.

It is clearer to see the different thermal effects of the HXRV. However, this is still not clear. Continue to examine the EOIR capabilities of STK, this time closer to Earth.

Placing an EOIR sensor on a UAV

EOIR sensors are flexible tools that you can use in all domains. EOIR can create an image of what the system on a UAV flying near the HXRV can see. You can copy the sensor attached to the satellite to save on setup time.

  1. Copy the Imager () from LEOSat.
  2. Paste it on RQ-4B_Globalhawk ().
  3. Rename it UAV_Imager.

Modifying the field of view

The UAV is much closer to the HXRV. You can modify the field of view of the sensor because it does not need to be so small.

  1. Open UAV_Imager's () Properties ().
  2. Browse to the Basic - Definition page.
  3. Ensure the Spatial tab is selected.
  4. Set the following options:
    5. Option Value
    Horizontal Half Angle 0.01 deg
    Vertical Half Angle 0.01 deg
  5. Click OK.
  6. Save () the scenario.

Generate a sensor scene

  1. Set the scenario time to 1095 EpSec. This is the time when the distance between both objects is shortest .
  2. Select the UAV_Imager ().
  3. Click the EOIR Sensor Scene () icon. STK might take a few moments to generate the sensor scene.

    4. EOIR sensor Scene: Hypersonic flight

    Notice the difference between the Imager on the satellite and the Imager on the UAV. The UAV is flying much closer to the HXRV and so it has a more defined sensor scene. In this recreation of the hypersonic flight, you did not model the plume and just focused on the "what if" of a vehicle going this fast.

Examining the scene

Changing the visual details

  1. Right-click in the Sensor Scene window.
  2. Select the Details option.
  3. Set the Color Map to BGRY as the EOIR Scene Visual Details.
  4. Click Apply.

    5. EOIR sensor Scene: Hypersonic flight BGRY with points selected

  5. Select various points on the display to get additional data. Note the Temperature when clicking on various points of the X-43.
  6. Close the sensor scene when done.
  7. Save () the scenario.

Analyzing the Sensor System

Data providers enable you to pull relevant data from their mission. You can create a custom graph that measures the signal-to-noise ratio throughout the flight.

  1. Open the Report & Graph Manager ().
  2. Set the Object Type to Sensor.
  3. Select the sensor attached to the RQ-4B_Globalhawk from the list of sensors.
  4. Click the Create new graph style () icon.
  5. Rename the graph SNR_Hypersonic.
  6. Expand the EOIR Sensor To Target Metrics data provider.
  7. Double-click 'Signal to noise ratio' to add it to the Y Axis.
  8. Set the Step Size to 120 sec.

    9. EOIR can take a while to calculate, so it is a good idea to start with coarse settings and refine them later.

  9. Click OK.

Generating the graph

  1. Double-click SNR_Hypersonic to generate the graph.
  2. Select HXRV_X43 () as the target.
  3. Click OK. It may take a moment to generate the graph.
  4. Take a look at the results and notice how the system behavior changes over the time of the flight. Unlike the previous graphs of data you've looked at, the X axis is the time in the graph. You'll want to look at the behaviors of the HXRV_X43 at various times in the mission to understand the data.

EOIR sensor Scene: EOIR sensor to Target Metrics

Modifying the time step

The data from the graph is rough. Modify the time step to get additional information. This will take additional time to process, about 45 minutes, depending on your machine. Alternatively, you may use the image below as reference and jump to the times specified.

  1. Bring the graph to the front.
  2. Set the Step size to ten (10) seconds.

    3. EOIR sensor Scene: EOIR sensor to Target Metrics with 10 second time step

    From what you modeled of the launch, the first ~15 min (900 EpSec) are when the HXRV_X43 is attached to the HXLV_Pegasus. At ~925 EpSec there is a dip. The HXLV_Pegasus is raising to a higher altitude before the HXRV_X43 is deployed. Set the scenario time to 1000.00 EpSec and step forward in time to observe the deployment. It corresponds to the slight bump in the SNR before the peak. The peak at ~1100.00 EpSec corresponds to the moment the HXRV_X43 is the closest to the RQ-4B_Globalhawk, which is the platform for the thermal infrared sensor. Finally, recall that the HXRV_X43 descended into the ocean, which you be follow in the remainder of the graph.

    The HXRV_X43 Trajectory modeled using Aviator and imaged with EOIR

Summary

You have modeled the X-43 flight with a basic performance model and then compared that to a performance model derived from CFD using Aviator. With this tool, you can verify and validate their flights. Once the data is in STK, you can conduct post-flight analysis. With EOIR, you can model what their on-board systems see and how well they can detect an object traveling at Mach speeds.

DME Lesson 3

The next lesson in the DME series focuses on the test or mission planning phase of the life cycle. Using the same models constructed through the design phase, you will evaluate relationships between assets like communications link availability and how that influences the overall mission timeline.