The Launch Verification Process

E. J. Tomei

An impartial and comprehensive system review verifies the flightworthiness of a launch vehicle and instills confidence in ultimate mission success.

The process used to independently determine launch system flight readiness is a capability unique to The Aerospace Corporation that has been employed for more than 40 years. It is based on a comprehensive technical assessment that is thorough in its attention to detail with total system coverage.

The Aerospace approach to launch-readiness verification is unparalleled in its breadth and depth. This comprehensive, end-to-end process extends from concept and requirements definition through flight operations: It entails the detailed scrutiny of hundreds, if not thousands, of components, procedures, and test reports; it draws upon independently derived system and subsystem models to objectively validate contractor data; it provides timely review through firsthand involvement in all aspects of the launch campaign; and it concludes with a thorough postflight assessment using independent analytical tools and independently acquired telemetry data to generate useful feedback and monitor performance trends.

Following is a brief description of some of the critical activities needed to complete the process for a given mission.

System Design and Qualification

Aerospace begins by verifying that overall top-level performance requirements are properly supported by lower-level systems and subsystems. Independent analyses validate dynamic loads and clearances, structural margins, thermal protection, and control stability.

At this point, design engineers review system, subsystem, and component qualification requirements to ensure that they provide adequate margins. Qualification testing is witnessed and documented, and the test results are evaluated to confirm that they meet system requirements. Such thorough qualification reviews apply to engines, solid motors, ordnance, controls, avionics, guidance, structures, and major subassemblies.

This functional flow diagram outlines the primary elements of the Aerospace independent launch-readiness verification process. This comprehensive process extends from concept and requirements definition through flight operations and includes a postflight assessment using independent tools.

Milestone reviews must also be conducted, including a system requirements review, software design review, preliminary design review, and critical design review. Aerospace evaluates any changes with respect to the qualification baseline and may recommend requalification if the changes are severe or have been improperly implemented.

Manufacturing and Quality

The manufacturing process must also be reviewed to ensure that it can produce the final design. Quality-control processes are checked for compliance with standards and requirements.

After reviewing the results of initial production, Aerospace provides technical support to resolve problems with manufacturing techniques. This support can entail in-plant review of hardware and processes.

Hardware Verification

Even before hardware can be screened for defects, acceptance test plans and procedures must be reviewed to ensure that the test environments and pass/fail criteria can be trusted to screen out faulty components. Aerospace responsibilities in this area include witnessing selected acceptance testing of critical items and reviewing anomaly reports and corrective actions. Aerospace personnel also monitor failure investigations, and, in certain critical cases, augment them with independent investigations, which can include metallurgical analyses, material compatibility checks, electronic component testing, and contamination assessments.

One particularly important task is the hardware "pedigree" review, which focuses on individual components and subsystems to establish that they were built and tested according to specification. This pedigree review includes a check of quality-assurance documentation to verify that the manufacturer followed the appropriate procedures, implemented engineering changes properly, justified any deviations adequately, and used valid criteria in selecting new processes or materials. The pedigree also includes an assessment of acceptance testing.

Software Validation

Every space launch requires mission-specific software that contains the instructions needed to get the payload from the launchpad to its intended orbit. Aerospace conducts an independent validation and verification of critical system software, especially pertaining to guidance, navigation, and control.

Comparison of early launch reliability performance of government and commercial launch programs suggests that the independent design certification resulting from the launch verification process results in a tenfold reduction in risk. Probability of failure comparison: 33 percent versus 3.1 percent.

Validation of the launch system software typically requires the development of independent models and tools. Verification of flight software involves independent simulations in two phases using preliminary, then final, data from the dynamics analysis and mission design activities. These simulations ensure that programmers have implemented the correct trajectory and navigation algorithms in the autopilot software and have properly laid out the sequence of events to be followed during launch.

Mission Planning, Verification, and Analysis

A well-built launch system can still fail in its mission if it's not properly integrated with its payload. Mission design analysis provides assurance that the launch system is capable of delivering the specific payload to its planned orbit with sufficient margin to guarantee mission success. Aerospace performs an independent analysis to verify adequate mission planning for all flight conditions. This involves examining system-level and integration requirements, confirming all mission-specific payload integration requirements to ensure that baseline reliability is preserved and new requirements have been met, and ensuring that all prior flight and test anomalies have been adequately resolved.

The mission analysis establishes that the flight trajectory and parameters are optimized for the specific payload, satisfy flight and safety constraints, and provide adequate margins for the radio-frequency link, power, propellant, and consumables. Dynamic loads must be analyzed to verify booster capability and compliance with the interface control document. Guidance, navigation, and control performance must also be analyzed for acceptable injection accuracy and control stability. Emphasis is placed on new hardware and software or new applications of established designs.

Other analyses—covering details such as aerodynamics, thermodynamics, vibro-acoustics, electromagnetic compatibility, radio-frequency interference, separation clearance, and contamination—verify operation within vehicle capabilities and interface control document specifications.

Assembly, Test, and Preflight Readiness

At the launch site, numerous tasks must be accomplished to prepare for launch. Aerospace assesses these processes to establish that they adequately support mission readiness and satisfy design requirements and operational constraints. Critical tasks and tests are witnessed and evaluated for compliance with requirements and procedures. Particular attention is placed on anomaly identification and resolution. Aerospace personnel support all major launch site tests and readiness reviews and provide technical corroboration for the test team.

Launch-Readiness Verification

Assuming all procedures have been properly documented and all test results fall within acceptable levels, Aerospace can now give its launch-readiness verification to the Air Force's Space and Missile Systems Center (SMC). This document includes an overview of the launch verification activities, a listing of independent analyses and verifications, results of the pedigree review, a synopsis of lessons learned from similar missions, an explanation of anomaly review and resolution efforts, and an appraisal of launch-site processing adequacy.

The assessment culminates in a flightworthiness determination and certification by SMC at a meeting known as the Flight Readiness Review. The objective is to ensure that the primary contractors, Aerospace, the spacecraft program office, and the launch programs agree that the launch vehicle and payload are ready to begin final launch operations.

Countdown and Launch

Aerospace personnel are "on-station" during countdown and launch, supporting launch decisions with the knowledge and experience gained during the launch verification process. Day-of-launch support also entails an independent review of launch placards, countdown anomalies, deviations and workarounds, and launch constraint violations. Any anomaly or deviation observed until liftoff may result in a reassessment of the vehicle's launch readiness. If the launch is scrubbed, a new flight readiness assessment may be required before the countdown can resume.

Contribution of engineering errors to launch failures is relatively low on government programs. During the last decade, the rate of failures attributable to engineering errors on government programs was less than 3 percent, compared with nearly 15 percent for commercial programs.

Aerospace personnel also provide countdown and launch support via the Spacelift Telemetry Acquisition and Reporting System (STARS) room. From this facility, launch system technicians have access to a historical flight database via special computer and software tools, allowing independent evaluation of trends and mission-to-mission performance.

Postflight Analysis and Lessons Learned

Aerospace's responsibility does not end when the launch vehicle finally leaves the pad. In fact, some of the most rigorous analysis happens after liftoff. For example, launch-system flight data are analyzed to independently assess vehicle performance, identify and assess flight anomalies, and update the data archives. Postflight analyses and reconstructions are used to perform trend analyses, capture lessons learned, and provide feedback for the next readiness assessment.

Postflight analysis of mission performance, for example, compares actual flight trajectory and performance characteristics to predicted values. Guidance measurements are processed to produce a trajectory profile and determine stage energy levels. Pressures, temperatures, atmospheric conditions, vehicle position, vehicle velocity, vehicle acceleration, aerodynamic drag, dynamic pressure, and timing of discrete events are used to evaluate vehicle performance during flight. Solid and liquid engine thrust, specific impulse, flow rates, pressures, temperatures, stage energy performance, system performance margins, mixture ratio, and propellant margin parameters are analyzed and compared to predictions.

Similarly, postflight analyses determine whether all components performed as expected. Measurements and data are compared with predictions and historical values, and deviations are logged, analyzed, and resolved.

Additional postflight analyses include review of radar, film, and video images collected during ignition, liftoff, and flight to determine flight behavior (particularly during staging events) to identify any anomalous conditions or sources of debris.

Conclusion

Aerospace's end-to-end system review is a routine but critical part of every SMC launch. The impartial and independent launch verification provides assurance that all known technical issues have been resolved and that residual launch risks have been identified and assessed. When Aerospace signs off on its launch-readiness verification, SMC can proceed with strong confidence in ultimate mission success.