AC 450.115-1B

C Advisory U.S. Department of Transportation Federal Aviation Circular Administration Subject: High Fidelity Flight Safety Analysis Date: 08/02/2024 AC No: 450.115-1B Initiated By: AST-1 This Advisory Circular (AC) provides guidance and a comprehensive method for performing a high fidelity flight safety analysis in accordance with title 14 of the Code of Federal Regulations (14 CFR) § 450.115. A flight safety analysis is required for launch and reentry in accordance with § 450.113(a). AC 450.113-1, Level of Fidelity, provides guidance on when a high fidelity flight safety analysis is needed and how to determine the level of fidelity that is required. In situations when a high fidelity flight safety analysis is needed, this AC 450.115-1 provides guidance for performing that analysis in compliance with § 450.115(b). A high fidelity flight safety analysis may be required by § 450.115(b) for a particular phase or for all phases of flight. An operator’s flight safety analysis method must account for all reasonably foreseeable events and failures of safety-critical systems during nominal and non-nominal launch or reentry that could jeopardize public safety, in accordance with § 450.115(a). In accordance with § 450.115(b)(1), the analysis must demonstrate that any risk to the public satisfies the safety criteria of § 450.101, including the use of mitigations, and account for all known sources of uncertainty, using a means of compliance accepted by the Federal Aviation Administration (FAA). The analysis must identify the dominant source of each type of public risk with a criterion in §§ 450.101(a) or 450.101(b) in terms of phase of flight, source of hazard (such as toxic exposure, inert, or explosive debris), and failure mode, in accordance with § 450.115(b)(2).

The FAA considers this AC an accepted means of compliance for complying with the regulatory requirements of § 450.115(b). It presents one, but not the only, acceptable means of compliance with the associated regulatory requirements. This AC assists with performing a high fidelity flight safety analysis. The contents of this document do not have the force and effect of law and are not meant to bind the public in any way. The document is intended only to provide clarity to the public regarding existing requirements under the law or agency policies.

If you have suggestions for improving this AC, you may use the Advisory Circular Feedback form at the end of this AC.

Daniel Murray Executive Director, Commercial Space Transportation

Contents Paragraph Page

1 Purpose2

2 Applicability3

3 Applicable Regulations and Related Documents4

4 Definition of Terms7

5 Acronyms9

6 Overview10

6.1 High-fidelity Flight Safety Analysis Method10

7 Mission Definition and Hazard Identification12

7.1 Mission Description12

7.2 Identifying Hazards and Hazard Producing Events17

7.3 Hazard Management to Minimize Public Risk18

8 Hazardous Debris Characterization19

8.1 Developing Hazardous Debris Lists for Range Safety Analyses19

8.2 Effect of Type of Vehicle Breakup on Hazardous Debris List23

8.3 Effect of Vehicle Structural Characteristics and Materials on Breakup Hazardous

Debris List26

8.4 Effect of Energetics in the Vehicle on Breakup on Hazardous Debris List27

8.5 Steps for Developing Hazardous Debris Fragment Lists30

8.6 Hazardous Debris Containing Toxic Material34

9 Aerodynamic and Harmful Debris Characteristics35

9.1 Ballistic Coefficients35

9.2 Drag Coefficient Estimates for Continuum Flow35

9.3 Drag in Transitional and Free Molecular Flow Regimes36

9.4 Lift Uncertainty36

9.5 Required Information in the Hazardous Debris Model37

9.6 Consideration for Grouping Hazardous Debris to a Hazardous Debris Group38

9.7 Description of the Hazardous Debris Group38

9.8 Fragmentation Guidelines Based on Historical Data43

10 Propagation of Hazardous debris to Impact44

Contents Paragraph Page

10.1 Atmospheric Data for Propagation44

10.2 Failure and Planned Event State Vectors47

10.3 Statistical Trajectory Set50

10.4 Ballistic Trajectory Generation51

10.5 Residual Thrust53

10.6 Directed Lift54

10.7 Progressive Breakup and Breakup Fragment Shedding55

10.8 Hazardous Debris Demise55

11 Impact Probability Distribution56

11.1 Impact Probability56

11.2 Gaussian Distribution57

11.3 Skewed Distribution57

11.4 Histogram Distribution58

11.5 3-dimensional Impact Probability58

12 Consequence Modeling59

12.1 Types of Consequences59

12.2 Inert Hazardous Debris62

12.3 Unsheltered People63

12.4 Casualty Areas66

12.5 Probability of Casualty Area68

12.6 Potential for Roof Penetration68

12.7 People in Waterborne Vessels (Ships)73

12.8 People in Aircraft75

12.9 Explosive Hazardous Debris77

12.10 Yield Models78

12.11 Liquid Propellant Yield79

12.12 Solid Propellant Yield80

12.13 Sympathetic Yields83

12.14 Impacting Propellants for Unsheltered People84

12.15 Blast Wave Overpressure84

iii

Contents Paragraph Page

12.16 People in Structures87

12.17 Floor Fire90

12.18 Blast Wave Overpressure91

12.19 People in Waterborne Vessels (Ships)94

12.20 Toxic Emitters96

12.21 Secondary Hazardous Debris Fragments96

12.22 Intact Impact Vehicle97

12.23 Intact Propellant Tank Secondary Hazardous Debris97

12.24 Inert Fragment Splatter98

13 Risk Computation98

13.1 How Risk is Expressed98

13.2 Risks to Population Centers and Protected Objects99

13.3 Probability of Hazardous Debris Generating Event100

13.4 Probability of Impact100

13.5 Individual Risk102

13.6 Conditional Casualty Expectation103

13.7 Aggregate Risk103

13.8 Analysis104

14 Flight Hazard Area Definition106

14.1 Sources of Hazards106

14.2 Flight Hazard Areas106

14.3 Examples of Specific Flight Hazard Areas107

14.4 Contour Grids and their Durations107

14.5 Development of Notices to Mariners108

14.6 Development of Notices to Airmen108

14.7 Development of Land Hazard Areas109

15 Satisfying Applicant Submission Requirements110

15.1 Nominal and Failure Trajectories110

15.2 Failure and Planned Event State Vectors110

15.3 Breakup and Jettisoned Hazardous Debris111

iv

Contents Paragraph Page

15.4 Probability of Failure112

15.5 Requirements for Flight Hazard Areas112

15.6 Hazardous Debris Propagation and Impact Distributions112

15.7 People and Assets113

15.8 Consequence and Risk113

Figures Number Page

Figure 1 – Comparison of Various Skew-Normal Curves58

Figure 2 – Probability of Casualty Curves for Non-Mission Essential, Vertical Impact to Head, Figure 3 – Probability of Casualty Curves for Non-Mission Essential, Sphere Impacting Chest, Figure 4 – Probability of Casualty Curves for Non-Mission Essential, Sphere Impacting Figure 5 – Probability of Casualty Curves for Non-Mission Essential Sphere Impacting Leg, Figure 7 – Effective Casualty Areas of Hazardous Debris Hitting a Light Metal Roof (Class A)71 Figure 10 – Effective Casualty Areas of Hazardous Debris Hitting a Concrete Reinforced with

Blunt Injury64

Blunt Injury64

Abdomen, Blunt Injury65

Blunt Injury65

Figure 6 – Illustration of a Wood Built-Up Roof68

Figure 8 – Effective Casualty Areas of Hazardous Debris Hitting a Wood Roof (Class B)71

Figure 9 – Effective Casualty Areas of Hazardous Debris Hitting a Composite Roof (Class C). 72

Steel Roof (Class D)73

Figure 11 – Sample Aircraft Vulnerable Projected Areas77

Figure 12 – Peak Overpressure vs. Scaled Distance from Blast Waves78

Figure 13 – Impulse vs. Scaled Distance from Blast Waves79

Figure 14 – Yield Curves for Liquid Propellants on Hard Surfaces80

Figure 15 – HD 1.1 Propellant Yield Model81

Figure 16 – Yield Curves for Motor Segment Side-On Impacts on Sand82

Figure 17 – Yield Curves for Cube Chunks Impacting on Sand82

Figure 18 – Yield Curves for 120ᵒ CAS Side-On Impacts on Sand83

v

Contents Paragraph Page

Figure 19 – Probability of Serious Injury to a Lung85

Figure 25 – Reinforced Concrete Roof Effective Casualty Area Ratio as a Function of Roof Area Figure 29 – Calculation of the Risk to a Population Center Due to the Impact of an Explosive

Figure 20 – Probability of Serious GI Tract Injury86

Figure 21 – Probability of Serious Larynx Injury86

Figure 22 – Probability of Serious Eardrum Rupture87

Figure 23 – Wood Roof Effective Casualty Area Ratio as a Function of Roof Area and Yield .. 88

Figure 24 – Steel Roof Effective Casualty Area Ratio as a Function of Roof Area and Yield89

and Yield89

Figure 26 – Normalized Casualty Areas vs. Heat Load91

Figure 27 – Probability of Casualty for a Small Wood Structure, ~2500 ft292

Figure 28 – Large Annealed Windows (~5’H x 6’W x 0.232”T), GAR = 14.5 percent93

Fragment102

Tables Number Page

Table 1 – Example Values for Lift Uncertainty37

Table 2 – AIS Severity Levels61

Table 3 – Coefficients of Restitution67

Table 4 – Representative Building Classes70

Table 5 – Threshold Values for Significant Hull Damage74

Table 6 – Threshold Values for Ship Cabin and Deck Penetration75

Table 7 – Generic Window Types93

Table 8 – Water Impact Distances That Lead to Casualty95

Table 9 – Ship Explosive Effective Casualty Areas for People Below Deck95

vi

Principal Changes Revision B updates AC 450.115-1A, High Fidelity Flight Safety Analysis, dated May 21, 2021. This AC change includes the following principal changes.

1. This AC change includes removal of the content in Paragraph 9.2, Drag Coefficient Estimate for Continuum Flow. The FAA expects to provide replacement information for this paragraph in the next revision to this AC.

1 PURPOSE.

This Advisory Circular (AC) provides guidance and a comprehensive method for performing a high fidelity flight safety analysis in accordance with title 14 of the Code of Federal Regulations (14 CFR) § 450.115. AST drafted AC 450-113-1, Level of Fidelity, to help an operator determine the level of fidelity of the analysis required by § 450.115(b). In situations when a high fidelity flight safety analysis is needed, this AC provides guidance for performing that analysis in compliance with § 450.115(b). A high fidelity flight safety analysis may be required by § 450.115(b) for a particular phase or for all phases of flight.

1.1 Cancellation.

This AC cancels AC 450.115-1A High Fidelity Flight Safety Analysis, dated May 20, 2021.

1.2 Analysis Scope.

An operator’s flight safety analysis method must account for all reasonably foreseeable1 events and failures of safety-critical systems during nominal and non-nominal launch or reentry that could jeopardize public safety, in accordance with § 450.115(a). In accordance with § 450.115(b)(1), the analysis must demonstrate that any risk to the public satisfies the safety criteria of § 450.101, including the use of mitigations, and account for all known sources of uncertainty, using a means of compliance accepted by the FAA Administrator. In accordance with § 450.115(b)(2), the analysis must identify the dominant source of each type of public risk with a criterion in §§ 450.101(a) or

450.101(b) in terms of phase of flight, source of hazard (such as toxic exposure, inert, or explosive debris), and failure mode. In accordance with § 450.101(g), for any analysis used to demonstrate compliance with § 450.115(b), an operator must use accurate data and scientific principles, and the analysis must be statistically valid. Also, in accordance with § 450.101(g), the method must produce results consistent with or more conservative than the results available from previous mishaps, tests, or other valid benchmarks, such as higher-fidelity methods.

1.3 Description of Methods.

To satisfy the requirements of § 450.115(c), an applicant must submit a description of the flight safety analysis methodology, including identification of:

• The scientific principles and statistical methods used;

• All assumptions and their justifications;

• The rationale for the level of fidelity;

• The evidence for validation and verification required by § 450.101(g);

1 In the context of launch and reentry vehicle analysis, reasonably foreseeable events and failures are those identifiable through a system safety process, including all relevant failures that have occurred for prior vehicles.

• The extent to which the benchmark conditions are comparable to the foreseeable conditions of the intended operations; and

• The extent to which risk mitigations were accounted for in the analyses.

1.4 Level of Imperatives.

This AC presents one, but not the only, acceptable means of compliance with the associated regulatory requirements. The FAA will consider other means of compliance that an applicant may elect to present. Other means of regulatory compliance may be acceptable, but must be approved by the FAA Administrator in accordance with § 450.35(a)(1). In addition, an operator may tailor the provisions of this AC to meet its unique needs, provided the changes are accepted as a means of compliance by FAA.

Throughout this document, the word “must” characterizes statements that directly follow from regulatory text and therefore reflect regulatory mandates. The word “should” describes a requirement if electing to use this means of compliance; variation from these requirements is possible, but must be justified and accepted by the FAA as an alternative means of compliance. The word “may” describes variations or alternatives allowed within the accepted means of compliance set forth in this AC. In general, these alternative approaches can be used only under certain situations that do not compromise safety.

2 APPLICABILITY.

2.1 The guidance in this AC is for launch and reentry vehicle applicants and operators required to comply with 14 CFR part 450. The guidance in this AC is for those seeking a launch or reentry vehicle operator license, a licensed operator seeking to renew or modify an existing vehicle operator license, and FAA commercial space transportation evaluators.

2.2 The material in this AC is advisory in nature and does not constitute a regulation. This guidance is not legally binding in its own right, and will not be relied upon by the FAA as a separate basis for affirmative enforcement action or other administrative penalty.

Conformity with this guidance document (as distinct from existing statutes and regulations) is voluntary only, and nonconformity will not affect rights and obligations under existing statutes and regulations. This AC describes acceptable means, but not the only means, for demonstrating compliance with the applicable regulations.

2.3 The material in this AC does not change or create any additional regulatory requirements, nor does it authorize changes to, or deviations from, existing regulatory requirements.

3 APPLICABLE REGULATIONS AND RELATED DOCUMENTS.

3.1 Related Statute.

• 51 U.S.C. Subtitle V, Chapter 509.

3.2 Related Regulations.

The following regulations from titles 14 and 49 of the CFR must be accounted for when showing compliance with 14 CFR § 450.115. The full text of these regulations can be downloaded from the U.S. Government Printing Office e-CFR. A paper copy can be ordered from the Government Printing Office, Superintendent of Documents, Attn: New Orders, PO Box 371954, Pittsburgh, PA, 15250-7954.

• Section 401.7, Definitions.

• Section 450.35, Means of Compliance.

• Section 450.101, Safety Criteria.

• Section 450.103, System Safety Program.

• Section 450.108, Flight Abort.

• Section 450.113, Flight Safety Analysis Requirements—Scope.

• Section 450.117, Trajectory Analysis for Normal Flight.

• Section 450.119, Trajectory Analysis for Malfunction Flight.

• Section 450.121, Debris analysis.

• Section 450.123, Population Exposure Analysis.

• Section 450.131, Probability of Failure Analysis.

• Section 450.133, Flight Hazard Area Analysis.

• Section 450.135, Debris Risk Analysis.

• Section 450.137 Far-field Overpressure Blast Effects Analysis.

• Section 450.139 Toxic Hazards for Flight.

• Section 450.161, Control of Hazard Areas.

• Section 450.213, Pre-flight Reporting.

3.3 Related FAA Advisory Circulars.

FAA Advisory Circulars (will be available through the FAA website, http://www.faa.gov).

• AC 450.101-1B, High Consequence Event Protection, dated May 3, 2024.

• AC 450.108-1, Using Flight Abort Rule as a Hazard Control Strategy, dated July 27, 2021.

• AC 450.110-1, Physical Containment Flight Safety Analysis, dated September 27, 2022.

• AC 450.117-1, Normal Trajectory Analysis, dated August 19, 2021.

• AC 450.119-1, High-Fidelity Malfunction Trajectory Analysis, when published.

• AC 450.123-1, Population Exposure Analysis dated October 12, 2022.

• AC 450.137-1, Distant Focusing Overpressure (DFO) Risk Analysis when published.

• AC 450.139-1, Toxic Hazards Analysis and Thresholds dated July 8, 2024.

3.4 Technical Reports Related to High Fidelity Flight Safety Analysis.

1. Allahdadi, Firooz A., Isabelle Rongier, Tommaso Sgobba, Paul D. Wilde (Eds.), Safety Design for Space Operations, Sponsored by The International Association for the Advancement of Space Safety, published by Elsevier, Watham, MA, 2013.

2. Anderson, John D., Modern Compressible Flow: With Historical Perspective, McGraw-Hill Education, dated 2003.

3. Baker, W.E., et al., Workbook for estimating effects of accidental explosions in propellant ground handling and transport systems, NASA Contractor Report 3023, August 1978, https://ntrs.nasa.gov/citations/19790002055.

4. Baker, W.E., et al., Workbook for predicting pressure wave and fragment effects of exploding propellant tanks and gas storage vessels, NASA Contractor Report 134906, September 1977, https://ntrs.nasa.gov/citations/19760012208.

5. Bonson, S.P. Aerodynamic Characteristics for Debris from Space Shuttle External Tank, dated May 23, 2012. https://arc.aiaa.org/doi/10.2514/3.57727.

6. Collins, Jon D., Randolph Nyman, and Isaac Lotatti, Estimation of Space Shuttle Orbiter Reentry Debris Casualty Area, AIAA Atmospheric Flight Mechanics Conference and Exhibit, August 2005, AIAA Paper 2005-6321.

https://doi.org/10.2514/6.2005-6321.

7. Columbia Accident Investigation Board Report Vol. 1, NASA, Washington, D.C.

August, 2003.

8. Department of Defense World Geodetic System 1984, NIMA TR8350.2, Third Edition, Amendment 1, National Imagery and Mapping Agency, January 2000.

9. Eck, M. and M. Mukunda, On the nature of the fragment environment created by the range destruction or random failure of solid rocket motor casings. Fairchild Space, Report FSC-ESD-217-88-426, July 1988, https://ntrs.nasa.gov/citations/19920005979.

10. Hoerner, Sighard F., Fluid Dynamic Drag, Published by the Author, Midland Park, New Jersey, 1965.

11. Global Reference Atmospheric Model (GRAM) Suite:

https://software.nasa.gov/software/MFS-33888-1.

12. Iqbal, Naeem, Mark Salley, and Sunil Weerakkody, Fire Dynamics Tools (FDTs) Quantitative Fire Hazard Analysis Methods for the USNRC Fire Protection Inspection Program, NUREG-1805, Washington, DC, November 2004.

13. Julier, Simon J., and Jeffery K. Uhlmann, A General Method for Approximating Nonlinear Transformations of Probability Distributions, Technical report, RRG, Dept. of Eng. Science, University of Oxford, Nov 1996.

14. Kingery, C. N. and Bulmash, G., Airblast Parameters from TNT Spherical Air Burst and Hemispherical Surface Burst, ARBRL-TR-02555, Ballistic Research Laboratory, Aberdeen Proving Ground, MD, 1984.

15. Koppenwallner, G., The Drag of Simple Shaped Bodies in the Rarefied Hypersonic Flow Regime, AIAA 20th Thermophysics Conference Williamsburg, VA, 1985.

16. Kuo, Kenneth K. Fundamentals of Solid-Propellant Combustion, American Institute of Aeronautics and Astronautics, dated October, 1984.

17. Lambert, Jack D., Computational Methods in Ordinary Differential Equations, John Wiley & Sons, Chichester, 1977.

18. Larson, Erik W.F, and George M. Lloyd, Application of Kernel Density Estimation to Impact Probability Density Determination for Risk Analysis, 48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, Orlando Florida, January 2010.

19. Manning, Ted A. and Scott L. Lawrence, Fragment Acceleration Modeling for Pressurized Tank Burst, Journal of Spacecraft and Rockets, Vol. 54, No. 3, May-June 2017. https://arc.aiaa.org/doi/full/10.2514/1.A33765.

20. Pike J. A., Injury Scaling, Automotive Safety, Anatomy, Injury, Testing and Regulation, Published by Society of Automotive Engineers, Inc., SAE, 1990.

21. Richardson, Erin, et al, Richardson, Erin, et al, Monte Carlo Approach to Modeling the Breakup of the Space Launch System EM-1 Core Stage with an Integrated Blast and Fragment Catalogue, dated December 8, 2014.

https://ntrs.nasa.gov/citations/20150002599.

22. Risk Committee, Range Safety Group, Range Commanders Council, Common Risk Criteria for National Test Ranges, RCC 321-20 and RCC 321-20 Supplement, White Sands, NM 2020. https://www.wsmr.army.mil/RCCsite/Documents/321- 20_Common_Risk_Criteria_Test_Ranges/321- 20_Common_Risk_Criteria_Test_Ranges.pdf.

23. Snyder, M.W., Analysis of Video Imagery of the Reentry and Breakup of the STS-31 External Tank, dated August 6, 2002. https://ieeexplore.ieee.org/document/576656.

24. Wilde, Paul D., and Chris Draper, Aircraft Protection Standards and Implementation Guidelines for Range Safety, 48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, Orlando Florida, January 2010.