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Commercial Space Vehicle Emissions Modeling (2021)

Chapter: 6 AEDT Integration Plan

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Suggested Citation:"6 AEDT Integration Plan." National Academies of Sciences, Engineering, and Medicine. 2021. Commercial Space Vehicle Emissions Modeling. Washington, DC: The National Academies Press. doi: 10.17226/26142.
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Suggested Citation:"6 AEDT Integration Plan." National Academies of Sciences, Engineering, and Medicine. 2021. Commercial Space Vehicle Emissions Modeling. Washington, DC: The National Academies Press. doi: 10.17226/26142.
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Suggested Citation:"6 AEDT Integration Plan." National Academies of Sciences, Engineering, and Medicine. 2021. Commercial Space Vehicle Emissions Modeling. Washington, DC: The National Academies Press. doi: 10.17226/26142.
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Suggested Citation:"6 AEDT Integration Plan." National Academies of Sciences, Engineering, and Medicine. 2021. Commercial Space Vehicle Emissions Modeling. Washington, DC: The National Academies Press. doi: 10.17226/26142.
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Suggested Citation:"6 AEDT Integration Plan." National Academies of Sciences, Engineering, and Medicine. 2021. Commercial Space Vehicle Emissions Modeling. Washington, DC: The National Academies Press. doi: 10.17226/26142.
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Suggested Citation:"6 AEDT Integration Plan." National Academies of Sciences, Engineering, and Medicine. 2021. Commercial Space Vehicle Emissions Modeling. Washington, DC: The National Academies Press. doi: 10.17226/26142.
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Suggested Citation:"6 AEDT Integration Plan." National Academies of Sciences, Engineering, and Medicine. 2021. Commercial Space Vehicle Emissions Modeling. Washington, DC: The National Academies Press. doi: 10.17226/26142.
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Suggested Citation:"6 AEDT Integration Plan." National Academies of Sciences, Engineering, and Medicine. 2021. Commercial Space Vehicle Emissions Modeling. Washington, DC: The National Academies Press. doi: 10.17226/26142.
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Suggested Citation:"6 AEDT Integration Plan." National Academies of Sciences, Engineering, and Medicine. 2021. Commercial Space Vehicle Emissions Modeling. Washington, DC: The National Academies Press. doi: 10.17226/26142.
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Suggested Citation:"6 AEDT Integration Plan." National Academies of Sciences, Engineering, and Medicine. 2021. Commercial Space Vehicle Emissions Modeling. Washington, DC: The National Academies Press. doi: 10.17226/26142.
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Suggested Citation:"6 AEDT Integration Plan." National Academies of Sciences, Engineering, and Medicine. 2021. Commercial Space Vehicle Emissions Modeling. Washington, DC: The National Academies Press. doi: 10.17226/26142.
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Suggested Citation:"6 AEDT Integration Plan." National Academies of Sciences, Engineering, and Medicine. 2021. Commercial Space Vehicle Emissions Modeling. Washington, DC: The National Academies Press. doi: 10.17226/26142.
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Suggested Citation:"6 AEDT Integration Plan." National Academies of Sciences, Engineering, and Medicine. 2021. Commercial Space Vehicle Emissions Modeling. Washington, DC: The National Academies Press. doi: 10.17226/26142.
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Suggested Citation:"6 AEDT Integration Plan." National Academies of Sciences, Engineering, and Medicine. 2021. Commercial Space Vehicle Emissions Modeling. Washington, DC: The National Academies Press. doi: 10.17226/26142.
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Suggested Citation:"6 AEDT Integration Plan." National Academies of Sciences, Engineering, and Medicine. 2021. Commercial Space Vehicle Emissions Modeling. Washington, DC: The National Academies Press. doi: 10.17226/26142.
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Suggested Citation:"6 AEDT Integration Plan." National Academies of Sciences, Engineering, and Medicine. 2021. Commercial Space Vehicle Emissions Modeling. Washington, DC: The National Academies Press. doi: 10.17226/26142.
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Suggested Citation:"6 AEDT Integration Plan." National Academies of Sciences, Engineering, and Medicine. 2021. Commercial Space Vehicle Emissions Modeling. Washington, DC: The National Academies Press. doi: 10.17226/26142.
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Commercial Space Vehicle Emissions Modeling 59 6 AEDT Integration Plan The projected growth of the commercial space industry will increase the demand for a standard emissions model to assess the environmental impacts of commercial space transportation. AEDT is the standard tool used to model emissions and noise from commercial aviation in the United States. Integrating the commercial space vehicle emissions model with AEDT is a logical step toward achieving a comprehensive suite of software tools for assessing the environmental impacts of both aircraft and spacecraft. The following sections describe the necessary software and user interface modifications to achieve a seamless integration of the commercial space vehicle emissions model with AEDT:  Section 6.1 summarizes the database and modeling modifications needed to accommodate elements of the emissions model unique to commercial space vehicles,  Section 6.2 presents a conceptual design of the user interface modifications needed to accommodate inputs unique to commercial space vehicles,  Section 6.3 provides pseudocode for the commercial space vehicle emissions algorithms,  Section 6.4 discusses a spreadsheet emissions estimator tool that provides programmers with a simple implementation example, and  Section 6.5 provides recommendations for software verification and validation. 6.1 Elements Unique to Commercial Space Vehicles The commercial space vehicle emissions model was developed with the intent to be integrated with AEDT. However, due to the design and operational differences between spacecraft and aircraft, some elements of the emissions modeling methodology are unique to space vehicles. The following sections discuss AEDT integration considerations for the unique elements of the fleet database, emissions indices, operational data, and emissions inventory for space vehicles. 6.1.1 Fleet Database As discussed in Section 3.1, the commercial space vehicle fleet database contains the vehicle- and engine-specific data required by the commercial space vehicle emissions model. The fleet database is comprised of independent spacecraft, airframe, and engine tables that are relationally linked via unique identifiers, as illustrated in Figure 18. This structure was designed for compatibility with the existing AEDT fleet database, which organizes commercial aircraft, military aircraft, and helicopters in separate tables. To integrate the commercial space vehicle emissions model with AEDT, a new table for spacecraft must be added to the existing AEDT fleet database. In AEDT, only a single type of engine is associated with an airframe during an analysis. However, space vehicles may be propelled by a combination of different types of engines, such as main engines and solid rocket boosters, that use different types of propellants. The ability to associate multiple types of engines with a single spacecraft is already defined in the commercial space vehicle fleet database via relational links between the spacecraft, airframe, and engine tables. This functionality needs to be incorporated into the AEDT fleet database during AEDT integration.

Commercial Space Vehicle Emissions Modeling 60 Elements unique to space vehicles:  Space vehicles may be propelled by a combination of different types of engines that use different propellants. AEDT integration considerations:  Add a new table for spacecraft to the existing AEDT fleet database.  Incorporate functionality to associate multiple types of engines with a single spacecraft. 6.1.2 Emissions Indices As discussed in Section 4.1, the emissions indices for space vehicles are defined as the grams of pollutant emitted per kilograms of propellant consumed. The propellant includes the fuel plus the oxidizer. In AEDT, the emissions indices for aircraft are defined as the grams of pollutant emitted per kilograms of fuel consumed. No modifications to AEDT are required to accommodate the different definitions of emissions indices for aircraft and spacecraft. However, the AEDT documentation should be updated to clearly inform users of the differences. The commercial space vehicle emissions model requires the final emissions indices in order to estimate the quantities of pollutants emitted into the atmosphere by a space vehicle. However, the commercial space vehicle fleet database only contains the primary emissions indices, which describe the chemical species present at the nozzle exit plane of the rocket engine. The altitude-dependent final emissions indices are calculated internally by the commercial space vehicle emissions model using the first-order estimates developed in Section 4.3. The inputs to the first-order estimates are the primary emissions indices and the user-specified altitude profile. These first-order estimates need to be implemented in AEDT using the pseudocode provided in Section 6.3. Elements unique to space vehicles:  Emissions indices for space vehicles are defined relative to the propellant mass consumed, where propellant includes the fuel plus the oxidizer.  The final emissions indices are strongly dependent on altitude. AEDT integration considerations:  Document the different definitions of emissions indices for aircraft and spacecraft.  Implement the first-order estimates for the final emissions indices. 6.1.3 Operational Data Commercial space vehicles operate differently than aircraft. Aircraft typically follow well-defined flight profiles that include standard climb and descent segments and long-duration periods of steady, level flight. AEDT enables users to construct aircraft flight profiles from standard taxi, takeoff, climb, cruise, turn, descent, and landing segments. Conversely, space vehicles nearly continuously climb, accelerate, and pitch over during launch operations (or descend and decelerate during re-entry). As discussed in Section 2.3, launch trajectories are highly dependent on the target orbit and launch

Commercial Space Vehicle Emissions Modeling 61 vehicle performance. Thus, space vehicles do not fly standard segments as defined in AEDT. Instead, AEDT needs to enable users to specify custom space vehicle flight profiles at detailed time intervals, such as every second. Adding this functionality to AEDT will require modifications to the user interface, as discussed in Section 6.2. Elements unique to space vehicles:  Space vehicles follow non-standard, continuously varying flight profiles. AEDT integration considerations:  Enable users to specify custom space vehicle trajectories. 6.1.4 Emissions Inventory and Propellant Burn Report AEDT defines mode categories to group the fuel burn report and emissions inventory by common phases of aircraft operations [120]. These mode categories, as illustrated in Figure 31, include startup, taxi, ground roll, climb, cruise, descent, and landing segments. Some of these ground-based mode categories, such as taxi and ground roll, are not applicable to space vehicles that launch or land vertically. The airborne mode categories in AEDT are reported in altitude bands below 1,000 feet, below the mixing height (3,000 feet), and below and above 10,000 feet. For aircraft, a single mode category above 10,000 feet is sufficient for reporting emissions and fuel burn during cruise. However, space vehicles traverse the entire vertical extent of the atmosphere during launch and landing operations. Thus, additional mode categories at higher altitudes are required to group the propellant burn report and emissions inventory for space vehicles. Figure 31. Existing AEDT mode categories.

Commercial Space Vehicle Emissions Modeling 62 The environmental impacts of space vehicle emissions vary depending on the atmospheric layer where they are emitted. For this reason, FAA guidelines state that environmental documents for commercial space vehicle operations should report emissions inventories by atmospheric layer [121, 122]. Figure 32 shows an illustration of the atmospheric layers below the Kármán line (100 km). These atmospheric layers are the most meaningful way to group propellant burn reports and emissions inventories for environmental analyses of commercial space vehicles. Thus, the atmospheric layers listed in Table 11 should be integrated into AEDT as new mode categories for commercial space vehicles. Table 11. Proposed mode categories for commercial space vehicles. Mode Category Altitude Band Troposphere below Mixing Height Between 0 and 3,000 ft Troposphere above Mixing Height Between 3,000 ft and 10 km Stratosphere Between 10 and 50 km Mesosphere Between 50 and 85 km Above Mesosphere Above 85 km Figure 32. Atmospheric layers below the Kármán line.

Commercial Space Vehicle Emissions Modeling 63 Elements unique to space vehicles:  Space vehicles traverse the entire vertical extent of the atmosphere.  Taxi and ground roll mode categories are not applicable to space vehicles that launch or land vertically. AEDT integration considerations:  Add atmospheric layers as new mode categories for space vehicles. 6.2 User Interface Modifications The existing AEDT user interface will accommodate most of the inputs for the commercial space vehicle emissions model. Relatively minor modifications will be required to enable users to add spaceport layout components, select space vehicles from the fleet database, and specify spacecraft- specific operational data. This section presents conceptual designs of the user interface modifications needed to integrate the commercial space vehicle emissions model with AEDT. The following procedure provides a high-level overview of the process for conducting a space vehicle emissions study in AEDT: 1. Create a new study, 2. Add a spaceport, 3. Add launch pads and landing zones, 4. Specify spacecraft trajectories, 5. Create spacecraft launch, landing, and static operations, 6. Define groups of operations, 7. Run the emissions study, and 8. View and export the emissions inventory and propellant burn report. The steps highlighted in bold require spacecraft-specific modifications to the AEDT user interface, as described in more detail below. Step 2: Add a Spaceport The following changes to the AEDT user interface are recommended to enable users to add a spaceport to a study:  Language specific to an “Airport” should be modified to “Airport/Spaceport.”  The AEDT airports database should be updated to include existing spaceports.  Spaceports without official International Air Transport Association airport codes should be assigned default codes, and guidance should be provided to users for such cases.  The AEDT user manual should be updated with the procedure to add a new spaceport.

Commercial Space Vehicle Emissions Modeling 64 Step 3: Add Launch Pads and Landing Zones The existing runway definitions in AEDT can be used for space vehicles that launch and land horizontally at airports and spaceports. However, the AEDT user interface should be modified to enable users to add launch pads and landing zones for space vehicles that launch and land vertically. Options to add a launch pad and add a landing zone should be included on the airport and spaceport design ribbon. If users select either of these options, a dialog box should appear to enable users to specify the required parameters for the launch pad or landing zone. Figure 33 shows a conceptual design of the airport and spaceport layout design panel with the launch pad dialog box. Figure 33. Conceptual design of the airport/spaceport layout design panel and launch pad dialog. Step 4: Specify Spacecraft Trajectories Since commercial space vehicles do not follow standard trajectory segments, AEDT must enable users to specify custom spacecraft trajectories at detailed time intervals. Thus, the AEDT user interface should allow users to select an existing spacecraft trajectory, create a new trajectory, or load a trajectory from a spreadsheet. Figure 34 shows a conceptual design of the dialog box to create, load, or edit a spacecraft trajectory. The only trajectory parameters required for the emissions model are the time and altitude. The propellant mass flow rate can also be specified to provide a time-varying propellant burn profile. The other trajectory parameters shown in Figure 34 are not required for the emissions model, but they are used for rocket noise modeling. Rocket noise modeling parameters are discussed in the final report for ACRP project 02-66, “Commercial Space Operations Noise and Sonic Boom Modeling and Analysis” [123].

Commercial Space Vehicle Emissions Modeling 65 Figure 34. Conceptual design of the spacecraft trajectory dialog. Step 5: Create Spacecraft Launch, Landing, and Static Operations Finally, a spacecraft button should be added to the operations tab of AEDT, and the types of operations should be expanded to enable users to create launch, landing, and static operations for space vehicles. New space vehicle operations wizards should be designed to enable users to define the required parameters for each type of operation. For example, Figure 35 shows a conceptual design of the static operations wizard. The wizard should automatically load the spacecraft-specific parameters from the commercial space vehicle fleet database based on the user-selected equipment. Additionally, the wizard should enable users to select options that are appropriate for space vehicle operations. For example, since space vehicles conduct fewer operations than aircraft, users should have the option to specify the number of space vehicle operations on an annual basis as opposed to a daily basis.

Commercial Space Vehicle Emissions Modeling 66 Figure 35. Conceptual design of the static operation wizard. 6.3 Emissions Model Pseudocode In addition to the front-end user interface modifications presented in the previous section, back-end software modifications are required to integrate the commercial space vehicle emissions model with AEDT. This section provides pseudocode for implementing the commercial space vehicle emissions algorithms. The input variables are the user-specified operational data and the built-in fleet database. The output variables are the mass of propellant burned and the mass of each pollutant emitted by the space vehicle during each trajectory segment of a single event (such as an individual flight or static fire). These output variables are required to generate the operations detail propellant burn report and emissions inventory for a single event. The propellant burn reports and emissions inventories for multiple events, mode categories, and operations groups can be calculated directly from the operations detail report using the methods already implemented in AEDT.

Commercial Space Vehicle Emissions Modeling 67 The pseudocode is organized into two functions:  CalculateVehicleEmissions calculates the mass of propellant burned and the mass of each pollutant emitted by the space vehicle during each trajectory segment. This function sums the propellant burned and pollutants emitted by all engines on the vehicle.  CalculateEngineEmissions calculates the mass of propellant burned and the mass of each pollutant emitted by a single engine during each trajectory segment. This function computes the final emissions indices using the first-order estimates presented in Section 4.3 and implements the emissions modeling methodology described in Section 3. A description of the input variables is provided in Table 12, and the output variables are summarized in Table 13. The variable dimensions are given in terms of the following definitions:  Np = number of pollutants, where Np = 7 for the commercial space vehicle emissions model because seven pollutants are computed: Al2O3, BC, Clx, CO, CO2, H2O, and NOx.  Nt = number of trajectory segments, which is one less than the number of timesteps because a segment is defined between each pair of points in the trajectory. If the space vehicle includes multiple types of engines, such as main engines and boosters, engine parameters for each type of engine are stored in the fleet database. Table 12. Pseudocode input parameters. Variable Name Size Units Description Operational Data spacecraftName 1 -- Spacecraft name in the fleet database time Nt + 1 s Trajectory segment time altitude Nt + 1 ft Trajectory segment altitude massFlowRate Nt + 1 kg/s Propellant mass flow rate of a single engine Fleet Database numberOfEngines 1 -- Number of engines of the specified type nominalBurnTime 1 s Nominal engine burn time nominalMassFlowRate 1 kg/s Nominal propellant mass flow rate primaryEI Np g/kg Primary emissions indices Table 13. Pseudocode output parameters. Variable Name Size Units Description vehiclePropellantBurn Nt kg Mass of propellant burned by the vehicle during each trajectory segment vehicleEmissions Nt × Np kg Mass of each pollutant emitted by the vehicle during each trajectory segment

Commercial Space Vehicle Emissions Modeling 68 The pseudocode for the commercial space vehicle emissions model is listed in Code Block 1 and Code Block 2. The syntax is similar to Python in terms of function definitions, comments, and indexing. define CalculateVehicleEmissions(operationalData, fleetDatabase) # Import operational and fleet data import spacecraftName, time, altitude from operationalData import spacecraftData from fleetDatabase # Set variables to zero before summation vehiclePropellantBurn = 0 vehicleEmissions = 0 # Iterate through types of engines (e.g., main engines and boosters) for n = numberOfEngineTypes in spacecraftData # Import engine data import numberOfEngines, primaryEI from spacecraftData[n] if massFlowRate is in operationalData # Use time-varying mass flow rate if provided in trajectory data import massFlowRate from operationalData burnTime = max(time[massFlowRate > 0]) else # Assume constant mass flow rate if not provided in trajectory data import nominalMassFlowRate, nominalBurnTime from spacecraftData[n] burnTime = nominalBurnTime for i = 0 to numberOfTimesteps - 1 if time[i] <= burnTime massFlowRate[i] = nominalMassFlowRate else massFlowRate[i] = 0 end if end for end if # Calculate propellant burn and emissions for all engines of the given type call (singleEnginePropellantBurn, singleEngineEmissions) = CalculateEngineEmissions(time, altitude, massFlowRate, burnTime, primaryEI) engineTypePropellantBurn = numberOfEngines * singleEnginePropellantBurn engineTypeEmissions = numberOfEngines * singleEngineEmissions # Calculate propellant burn and emissions for the overall vehicle vehiclePropellantBurn = vehiclePropellantBurn + engineTypePropellantBurn vehicleEmissions = vehicleEmissions + engineTypeEmissions end for return vehiclePropellantBurn, vehicleEmissions Code Block 1. Pseudocode to calculate the emissions from a space vehicle.

Commercial Space Vehicle Emissions Modeling 69 define CalculateEngineEmissions(time, altitude, massFlowRate, burnTime, primaryEI) # Constants feet2km = 0.3048/1000 # Molecular weight MW[CO] = 28.0097 MW[CO2] = 44.0087 MW[H] = 1.008 MW[H2] = 2.016 MW[H2O] = 18.015 # Iterate through trajectory segments for i = 0 to numberOfTimesteps - 2 # Calculate duration duration = time[i+1] - time[i] # Calculate mass of propellant burned if time[i+1] <= burnTime propellantBurn[i] = massFlowRate[i] * duration else if time[i] <= burnTime propellantBurn[i] = massFlowRate[i] * (burnTime - time[i]) else propellantBurn[i] = 0 end if # Calculate mean altitude in kilometers meanAltitude = feet2km * (altitude[i] + altitude[i+1])/2 # Calculate final emissions indices based on primary emissions indices finalEI[H2O] = (primaryEI[H2O] + primaryEI[OH] + MW[H2O]*(primaryEI[H]/MW[H] + primaryEI[H2]/MW[H2])) finalEI[CO] = min(primaryEI[CO], 0.0025*exp(0.067*meanAltitude)*(primaryEI[CO] + primaryEI[CO2])) finalEI[CO2] = primaryEI[CO2] + MW[CO2]/MW[CO]*(primaryEI[CO] - finalEI[CO]) finalEI[Al2O3] = primaryEI[Al2O3] finalEI[Clx] = primaryEI[HCl] + primaryEI[Cl] + primaryEI[Cl2] finalEI[NOx] = primaryEI[NOx] + 33*exp(-0.26*meanAltitude) finalEI[BC] = primaryEI[BC]*max(0.04, min(1, 0.04*exp(0.12*(meanAltitude - 15)))) # Calculate mass of each pollutant emitted for j = 1 to numberOfPollutants emissions[i, j] = finalEI[j] * propellantBurn[i] * duration end for end for return propellantBurn, emissions Code Block 2. Pseudocode to calculate the emissions from a single engine.

Commercial Space Vehicle Emissions Modeling 70 6.4 Spreadsheet Emissions Estimator Tool The algorithms provided in the previous section were implemented in a spreadsheet emissions estimator tool to provide future programmers with an implementation example of the commercial space vehicle emissions model. The tool includes multiple worksheets to demonstrate:  User inputs for vehicle and operational data,  Emissions model calculations, and  Propellant burn report and emissions inventory outputs. The vehicle parameters and trajectory data for Space Shuttle mission STS-124 are provided in the spreadsheet as a full working example of the commercial space vehicle emissions model. Although the Space Shuttle is not a commercial space vehicle, it was selected as the example vehicle because its propellant mass flow rate, burn time, emissions indices, and trajectory are publicly available. Additionally, the Space Shuttle includes both liquid-propellant main engines and solid-propellant boosters to demonstrate the commercial space vehicle emissions model for multiple types of engines with different emissions indices. Fleet Database Figure 36 shows a screenshot of the worksheet that allows users to input vehicle parameters. The required parameters for each type of engine on the vehicle include the number of engines, propellant type, propellant mass flow rate per engine, burn time, and primary emissions indices. The values of these parameters are shown in Figure 36 for the SSME and RSRM. As discussed in Section 6.1.1, these parameters are stored in the fleet database and will not need to be supplied by the user in AEDT.

Commercial Space Vehicle Emissions Modeling 71 Figure 36. User input worksheet for vehicle parameters. Operational Data Figure 37 shows part of the worksheet that allows users to provide operational data. At a minimum, the commercial space vehicle emissions model requires the altitude as a function of time in order to calculate the emissions inventory. The time-varying propellant mass flow rate for each type of engine may also be provided for additional accuracy. The as-flown altitude profile for the STS-124 mission is included in the spreadsheet emissions estimator tool to provide a working example of the commercial space vehicle emissions model. The propellant mass flow rate columns for the main engines and boosters also included in the spreadsheet, but a constant mass flow rate is used for this example instead of the actual time-varying mass flow rate for STS-124. As discussed in Section 6.2, modifications to the AEDT user interface will be required to allow users to specify detailed launch and landing trajectories for space vehicles. Vehicle Main Engines Boosters Parameter Value Units Parameter Value Units Number of Engines 3 Number of Boosters 2 Propellant LOX/Hydrogen Propellant PBAN Mass Flow Rate 465.8 kg/s Mass Flow Rate 4081.3 kg/s Burn Time 516 s Burn Time 123 s Products Mass Fraction Units Products Mass Fraction Units Al2O3 0 g/kg Al2O3 301 g/kg CO 0 g/kg CO 241 g/kg CO2 0 g/kg CO2 34 g/kg H2O 959 g/kg H2O 93 g/kg H 0 g/kg H 0 g/kg H2 35 g/kg H2 21 g/kg OH 0 g/kg OH 0.2 g/kg HCl 0 g/kg HCl 212 g/kg Cl 0 g/kg Cl 3 g/kg Cl2 0 g/kg Cl2 0 g/kg NOx 0 g/kg NOx 0 g/kg BC 0 g/kg BC 25 g/kg Primary Emissions Indices Engine Performance Primary Emissions Indices USER INPUT | Vehicle Parameters Space Shuttle SSME RSRM Engine Performance

Commercial Space Vehicle Emissions Modeling 72 Figure 37. User input worksheet for operational data. Internal Calculations The spreadsheet emissions estimator tool includes several worksheets that implement the internal calculations required for the commercial space vehicle emissions model. These worksheets calculate the following parameters for each type of engine:  Propellant mass burned during each trajectory segment,  Final emissions indices as functions of altitude, and  Mass of each pollutant emitted during each trajectory segment. Additionally, the percentage of each trajectory segment that falls within each mode category is calculated to aggregate the emissions inventory and propellant burn report over entire atmospheric layers and other mode categories. Although screenshots of the intermediate calculation worksheets are not shown here, the calculations are provided in the pseudocode in Section 6.3 and are implemented in the spreadsheet for the benefit of future programmers. User ID STS-124 Spacecraft Space Shuttle Operation Type Launch No. Operations 1 * Required trajectory parameters Time* Altitude* Main Engine Mass Flow Rate Booster Mass Flow Rate (s) (ft) (kg/s) (kg/s) 0 2 465.8 4081.3 1 21 465.8 4081.3 2 55 465.8 4081.3 3 105 465.8 4081.3 4 172 465.8 4081.3 5 258 465.8 4081.3 6 361 465.8 4081.3 7 484 465.8 8 627 46 9 790 10 973 11 USER INPUT | Operational Data Trajectory

Commercial Space Vehicle Emissions Modeling 73 Emissions Inventory and Propellant Burn Report Figure 38 shows a screenshot of the output emissions inventory and propellant burn report grouped by operations mode. The report includes the mass of propellant burned and the mass of each pollutant emitted by the three main engines and the two solid boosters during each operational mode. As discussed in Section 6.1.4, the mode categories include existing AEDT modes that are applicable to space vehicles as well as new mode categories corresponding to the atmospheric layers. Figure 39 shows a screenshot of the output emissions inventory and fuel burn report grouped by operations detail. Since the spacecraft trajectory is specified at one-second intervals, the operations detail report provides the mass of propellant burned and the mass of each pollutant emitted during every one-second trajectory segment. The operations detail results may be useful to researchers who are interested in performing in-depth analyses of commercial space vehicle emissions.

Commercial Space Vehicle Emissions Modeling 74 Figure 38. Emissions inventory and propellant burn report grouped by operations mode. Figure 39. Emissions inventory and propellant burn report grouped by operations detail. Units kg User ID Spacecraft Mode Duration Main Engine Booster Total H2O CO2 CO Al2O3 Clx NOx BC (s) (kg) (kg) (kg) (kg) (kg) (kg) (kg) (kg) (kg) (kg) STS-124 Space Shuttle Full Flight 517.0 721,058 1,004,000 1,725,058 1,198,993 409,062 3,339 302,204 215,860 9,546 4,780 STS-124 Space Shuttle Troposphere Below Mixing Height 16.5 22,997 134,333 157,330 66,975 55,286 94 40,434 28,882 4,814 134 STS-124 Space Shuttle Troposphere Above Mixing Height 39.6 55,307 323,066 378,373 161,073 132,827 311 97,243 69,459 4,514 323 STS-124 Space Shuttle Stratosphere 72.1 100,740 546,601 647,341 281,634 220,949 2,934 164,527 117,519 218 4,323 STS-124 Space Shuttle Mesosphere 69.3 96,800 0 96,800 123,107 0 0 0 0 0 0 STS-124 Space Shuttle Above Mesosphere 319.6 445,213 0 445,213 566,205 0 0 0 0 0 0 STS-124 Space Shuttle Climb Below 1,000 feet 10.1 14,093 82,321 96,414 41,043 33,881 57 24,779 17,699 3,097 82 STS-124 Space Shuttle Climb Below 3,000 feet 16.5 22,997 134,333 157,330 66,975 55,286 94 40,434 28,882 4,814 134 STS-124 Space Shuttle Climb Below 10,000 feet 30.5 42,557 248,587 291,144 123,940 102,293 183 74,825 53,446 7,561 249 STS-124 Space Shuttle Above 10,000 feet 486.5 678,501 755,413 1,433,914 1,075,054 306,768 3,156 227,379 162,414 1,985 4,531 STS-124 Space Shuttle Descend Below 10,000 feet 0.0 0 0 0 0 0 0 0 0 0 0 STS-124 Space Shuttle Descend Below 3,000 feet 0.0 0 0 0 0 0 0 0 0 0 0 STS-124 Space Shuttle Descend Below 1,000 feet 0.0 0 0 0 0 0 0 0 0 0 0 Propellant Burn Emissions Inventory OUTPUT | Emissions Inventory and Propellant Burn Report Operations Mode Units kg User ID Spacecraft Ops. Type No. Ops. Segment Altitude Duration Main Engine Booster Total H2O CO2 CO Al2O3 Clx NOx BC (ft) (s) (kg) (kg) (kg) (kg) (kg) (kg) (kg) (kg) (kg) (kg) STS-124 Space Shuttle Launch 1 Full Flight -- 517 721,058 1,004,000 1,725,058 1,198,993 409,062 3,339 302,204 215,860 9,546 4,780 STS-124 Space Shuttle Launch 1 1 12 1 1,397 8,163 9,560 4,070 3,360 6 2,457 1,755 315 8 STS-124 Space Shuttle Launch 1 2 38 1 1,397 8,163 9,560 4,070 3,360 6 2,457 1,755 315 8 STS-124 Space Shuttle Launch 1 3 80 1 1,397 8,163 9,560 4,070 3,360 6 2,457 1,755 313 8 STS-124 Space Shuttle Launch 1 4 139 1 1,397 8,163 9,560 4,070 3,360 6 2,457 1,755 312 8 STS-124 Space Shuttle Launch 1 5 215 1 1,397 8,163 9,560 4,070 3,360 6 2,457 1,755 310 8 STS-124 Space Shuttle Launch 1 6 310 1 1,397 8,163 9,560 4,070 3,359 6 2,457 1,755 308 8 STS-124 Space Shuttle Launch 1 7 423 1 1,397 8,163 9,560 4,070 3,359 6 2,457 1,755 305 8 STS-124 Space Shuttle Launch 1 8 556 1 1,397 8,163 9,560 4,070 3,359 6 2 457 1 755 302 8 STS-124 Space Shuttle Launch 1 9 709 1 1,397 8,163 9,560 4 070 3 STS-124 Space Shuttle Launch 1 10 882 1 1,397 8,163 Shuttle Launch 1 11 1,132 1 1 3 OUTPUT | Emissions Inventory and Propellant Burn Report Propellant Burn Emissions Inventory Operations Detail

Commercial Space Vehicle Emissions Modeling 75 6.5 Software Verification and Validation The spreadsheet emissions estimator tool described in the previous section is intended to provide an implementation example of the commercial space vehicle emissions model that future programmers can refer to during AEDT integration. However, integrating the commercial space vehicle emissions model with AEDT is a multi-step process that includes being added to the AEDT development roadmap, implementing the emissions model in AEDT, and releasing a new version of AEDT. Prior to releasing a new version, thorough software verification and validation will be required to ensure the commercial space vehicle emissions model is implemented properly in AEDT. A multi-pronged approach involving software beta testers and technical subject matter experts is recommended for software verification and validation. Beta testers will verify the following user experience elements of the AEDT integration plan:  User interface modifications for commercial space vehicles are complete and easy to use,  Space vehicle parameters can be loaded from the fleet database,  Space vehicle operational data can be supplied by the user, and  The emissions inventory and propellant burn report include new mode categories corresponding to the atmospheric layers. Similarly, subject matter experts will verify the following technical elements of the AEDT integration plan:  Emissions indices for space vehicles are defined relative to the propellant mass consumed,  The first-order estimates for the final emissions indices are implemented correctly, and  The emissions inventory and propellant burn report are calculated accurately. Future programmers and subject matter experts should refer to the spreadsheet emissions estimator tool to verify the results of the commercial space vehicle emissions model following AEDT integration. The spreadsheet serves as a simple baseline for comparison and debugging purposes because the inputs, outputs, and formulas are readily visible. The software verification and validation recommendations provided here will ensure the commercial space vehicle emissions model is implemented properly in AEDT. However, as described in Section 5.2, future model validation studies, including advanced computational modeling and field measurements, are needed to confirm that the commercial space vehicle emissions model accurately predicts the real-world emissions produced by commercial space vehicles.

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Federal Aviation Administration (FAA) regulations require the licensing of spaceports and launch vehicles, which includes the assessment of environmental impacts.

The TRB Airport Cooperative Research Program’s ACRP Web-Only Document 51: Commercial Space Vehicle Emissions Modeling presents a user-friendly tool for practitioners to estimate the emissions associated with commercial space vehicle activity.

Supplementary materials to the document include an Emissions Example Information & Users Guide, the RUMBLE application, and a RUMBLE User Guide.

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