Date: Jul 15, 2010 Author: Joan M. Zimmermann Source: MDA (
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by Joan M. Zimmermann/jzimmermann@nttc.edu
Technologies developed for stabilizing space platforms and laser pointing for missile defense have made their way onto both commercial and NASA launch vehicles, credited with saving missions and cost.
CSA Engineering (Mountain View, CA) received several Missile Defense Agency SBIRs aimed at reducing vibration in various types of space platform settings, from diminishing vibration in cryocooling systems to damping individual components in laser weapons-pointing schemes, to steadying the missile imagers in airborne optical systems.
In space, in addition to the motion of the spacecraft itself, the very act of pointing a component introduces movement (jitter) that can continue to resonate for some time. However, there are even more vibrational issues in simply getting to space itself, as launch vehicles impart an enormous amount of stress to the payload in the act of lifting off.
For many years, the standard solution to reducing the severe vibro-acoustic launch environment required engineers to make the payload heavier than need be, and to temporarily lock into place the moving parts that operate on orbit. However, the increased mass typically means higher launch cost, and the complex process of unlocking the moving parts can increase the risk of operational failure.
Mechanical or passive vibration suppression requires no external power input. Active vibration suppression includes solutions such as actuators that provide counter-movement at a variety of frequencies, thus damping the vibration; interior active noise controls that use speakers to oppose vibrations; and the use of magnetically controlled fluids. CSA has incorporated both active and passive vibration solutions into its product lines, called SoftRide and QuietRide, both of which protect payloads during launch and then position critical instruments once the satellite is in orbit.
CSA's technologies have been making it easy to launch all types of vehicles into space, from tactical satellites to lunar spacecraft. For one launch alone, the company estimates that it saved its customer $20 million in redesign and schedule costs. In the face of launch failures and parts rattled loose by powerful launch vibrations, the dollars add up to billions. These savings have become particularly important to NASA missions, where launch costs keep rising as launch vehicles get more difficult to procure, and as more spacecraft get jury-rigged to hitch rides on non-ideal vehicles.
Overall, vibration isolation can help engineers reduce loads on components by three to five times, reduce payload mass, reduce the likelihood of mechanical failures, and increase reliability of missions. It also can help to prevent costly delays by protecting specific components in space that unexpectedly fail vibration tests on the ground. Such was the case with the NASA Wide-field Infrared Survey Explorer (WISE) mission, launched on a Delta II rocket. The Delta II, one of the larger launch vehicles, imparts a tremendous amount of force to the payload it lofts into orbit, resulting in movement that can dislodge circuitry. In the course of preparing for launch, NASA mission engineers found that the vibration of the launch vehicle would adversely affect the delicate sensors on WISE. CSA stepped in and provided a SoftRide whole-spacecraft isolation design that saved NASA months of redesign and requalification. WISE successfully launched in December 2009 and has already revealed excellent first-light image quality.
CSA, now a wholly-owned subsidiary of Moog Inc., continues its success story, in which NASA and other launching agencies are using its technologies in many applications, including LCROSS, a recent lunar mission, and Aeronomy of Ice in the Mesosphere (AIM), a small Explorer mission that was jet-launched on a Pegasus XL rocket. AIM is studying the so-called noctilucent (bright at night) clouds that hover in a thin layer over the poles.
