Aerospace, Military and Defence
One-stop-shop laboratory replicates deep space environment
The hardware used aboard spacecraft is exposed to severe shock, vibration, thermal variations and electromagnetic environments that start with launch and continue throughout the operational lifetime. To ensure the reliability and survivability of flight hardware, environmental tests designed to subject these parts to the expected stresses encountered in space, are performed in a laboratory using simulated conditions, to expose the hardware to these environments, validate the design, and screen for manufacturing defects.
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he equipment required to simulate the rigours of launch and operational use in deep space requires significant investment. Furthermore, few companies have the resources to perform the broad range of electrical, mechanical and environmental testing, as well as to analyse the resultant test data. Companies may either have to rely on external test services, adding to costs, extending development and delivery schedules, or instead attempt to negotiate away certain critical test needs.
To ensure testing integrity, many end users, certification organizations and government agencies, require impartial third-party laboratories to perform these tests. Smiths Interconnect, a global supplier of cutting-edge connectivity solutions, has invested to create the capability and capacity to perform a comprehensive range of environmental tests at its Dundee facility (see Figure 1), and now offers this important capability to its customers who are not prepared to negotiate on fundamental reliability and insist on demonstratable compliance.
Types of environmental tests Malfunctioning of critical flight hardware as a result of the operating environment, the failure of adjacent components and unplanned operating conditions, can lead to system degradation and in severe cases, catastrophic mission failure. For unmanned missions, this is unfortunate and expensive, however with the expected increase in manned space exploration, this could result in human tragedy.
Once launched, it is usually impractical to repair or replace flight hardware. Systems are therefore designed to incorporate layers of redundancy to mitigate such failure. Of course, this increases costs, reduces overload payload capacity and is not always possible. Where it is not possible to integrate redundancy, any
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then released to propel the expended stage safely, thus allowing the mission to continue.
Figure 1. Dundee site Qualification and Test Laboratory (General purpose test area shown). Source: Smiths Interconnect
single-point failure area is subject to additional scrutiny and testing to identify potential limitations and design flaws, to determine the operational envelope of the product and the point at which it will fail, and to highlight any errors or processing limitations. Some tests are designed to take the products to, and beyond their limits, but this approach cannot be used for every part and is reserved for a sample of the manufactured lot, with the remainder of the batch i.e. those intended to be used on the mission, exposed to the same or similar tests, albeit at reduced stress levels, but still stringent enough to screen for failures and to minimise or eliminate risk.
Launch vibro-acoustics
During a rocket’s ascent, high-level acoustic noise and vibrations are developed from the launch vehicle engines. In fact, acoustic levels during launch of the space shuttle approached almost 200 decibels, which could produce pressure waves that could flatten structures in the immediate vicinity of the launch pad. When the launch vehicle reaches a certain point, maximum flight dynamic pressure (max-q), high acoustic levels are developed by aerodynamic loads on the payload fairing
Components in Electronics
that can generate dynamic pressure loads in excess of 4 psi. These can excite vibrations of the launch vehicle that could damage flight hardware. For this reason, products and systems are routinely subjected to vibration testing that simulates launch in Dundee Test and Qualification laboratory. Typically, this means the flight hardware is attached to a “shaker”; a machine designed to apply high level of vibrations over wide spectrum to the hardware in all three axes (Figure 2) with the levels of vibration appropriate to the characteristics of the intended launch vehicle and the position of the product within the system.
Shock and deployment loads At various phases during the launch, stages of the rocket e.g., the first stage booster, and ultimately the payload itself, will be “ejected” to continue onwards or return to earth through gravitational pull. Ejection is accomplished using pyrotechnic (explosive) devices to shear the attachment bolts holding one stage top the other with springs,
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Once the payload is on-orbit, other pyrotechnic charges are used to deploy antennas, solar panels and other appendages. Each time a pyrotechnic device is used, severe short duration impulses or shocks are produced, which can damage sensitive instruments, optics and electronics. To ensure these instruments and components will withstand these events, pyrotechnic shocks are simulated in Smiths Interconnect’s lab in Dundee using a variety of “shakers” and shock impulse tables programmed to simulate precise shock response spectra (SRS; see Figure 3). Practically, this involves fixing the unit under test to a table and impacting the table with a massive hammer-like object. The shock waves produced, travel through the table and are transmitted to the product under test, with slow-motion imagery occasionally used to observe the remarkable effects as the energy is absorbed and dissipated.
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Figure 2. Electrodynamic shaker system. Source: Smiths Interconnect
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