Standard Establishes Test Requirements for the Acquisition of Space Hardware
First published May 2013, Crosslink® magazine
Today’s spacecraft specifications and standards incorporate lessons learned since the 1970s. These best practices for the design, analysis, and testing of spacecraft hardware encompass a broad range of technical disciplines and have evolved under sponsorship of the U.S. government’s procurement agencies. It is common practice to modify, or tailor, these approaches to reflect the situations that are unique to specific programs.
The extent of permissible tailoring is a significant part of contractual discussions during the preacquisition phase of a program, as the program office and potential contractors attempt to find a reasonable balance between cost and risk. Ideally, a process that results in well-defined, mutually acceptable modifications to the basic specifications and standards will permit proper costing and avoid contention on the scope of work from program initiation through initial operational capability. The challenge is to complete such a process before the contract is awarded, after which any changes can create significant additional costs for the customer.
Military Standard 1540 is a prime example of a test standard that, when tailored, has far-reaching effects on a program’s cost and schedule, and thus is closely scrutinized by customers and contractors. Starting with Mil-Std-1540A, the standard has been in use since 1975. The current proposed revision, Mil-Std-1540E, is based on The Aerospace Corporation’s technical report, “Test Requirements for Launch, Upper Stage, and Space Vehicles” (TR-2004 (8583)-1, Rev. A). The standard establishes baseline environmental testing requirements for launch vehicles, upper stages, space vehicles, and their subsystems and units. Thermal, acoustics, random vibration, shock, and low-frequency dynamic environments are considered. This standard is applicable to the procurement of space system hardware as a compliance document and can be tailored to meet individual program needs and buyer risk positions. The overall test program outlined focuses on design verification and the elimination of latent workmanship defects to help ensure a high level of confidence in achieving successful space missions.
A complete test program encompasses development, qualification/protoqualification, acceptance, and pre- and post-launch validation tests. The test methods, environments, and measured parameters are selected to permit the collection of empirical design and performance data for correlation and trending throughout the test program. The test strategy selected, such as qualification or protoqualification for the first build of the space hardware, impacts cost, schedule, and mission risk. These elements are balanced to achieve an optimum mix for a customer’s risk position.
Qualification tests demonstrate satisfaction of design requirements, including margin and product robustness. A full qualification validates the planned acceptance program, the in-process environmental stress screening, and any potential retests that might result from rework after a test failure. As a general rule, qualification hardware is not flown, and the test articles are amortized over the number of vehicles flown. This approach presents the highest degree of confidence that flight vehicles subjected to acceptance testing have adequate margins to survive the rigors of launch and maintain usefulness throughout the on-orbit life.
Protoqualification tests demonstrate satisfaction of design requirements by using reduced amplitude and duration margins on first unit flight hardware. These tests are appropriate for designs that have limited production and in which test units will be used for flight. The test program is supplemented by analyses, development, and other tests to demonstrate margin and viability. Protoqualification test hardware is flown at increased risk. The risk for subsequent acceptance hardware is reduced but is also elevated relative to the full qualification approach.
The baseline test requirements of Mil-Std-1540E are derived to encompass ground operations, launch, and mission profile. They are tailored to a specific program after considering design complexity, margins, vulnerabilities, technology state-of-the-art, in-process controls, mission criticality, lifecycle costs, number of vehicles involved, prior usage, and acceptable risk. The technical rationale for each tailored requirement is established and considered during the tailoring process. If the baseline qualification requirements in the standard are not tailored by the contract, they stand as written. In all acquisitions, the customer program office is the final approving authority in the tailoring process.
For competitive bid acquisitions, a team consisting of the customer and Aerospace personnel conducts the process of tailoring the standard to a program, even before a request for proposal is developed. The results of the tailoring process are included in the request for proposal so that contractors can reflect them in their bids.
For sole-source acquisitions, tailoring of the standard occurs later, usually near contract award. In this case, the team consisting of the customer, Aerospace, and the contractor performs the tailoring. Tailoring the standard for sole-source acquisitions is more detailed than tailoring for competitive bid acquisitions, since it can account for the contractor’s mission history, processes, and heritage hardware. Tailoring takes into account contractor-requested changes to the requirements.
Implementation of Mil-Std-1540 requires teamwork between the customer, contractor, and Aerospace program offices and engineering. The Aerospace team responsible for maintaining this environmental test standard continually works with its industry counterparts to monitor ground test and flight data to assess the effectiveness of environmental testing for improvements in future applications.
– Erwin Perl, director, Environment Test and Assessment Department
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