NASA-STD-7002B Aerospace Shaker Vibration Test
Nasa-std-7002b is part of the NASA standard that provides a standard set of flight hardware test requirements,
The standard applies to all payload hardware that NASA develops internally or under contract to launch on a single-use or reusable launch vehicle, including free vehicles and additional payloads.
NASA-STD-7002B types of vibration testing
Mechanical test
Vibration test
Thermal test
EMI/EMC testing
Functional testing
However, when it is suspected that a component is sensitive to this type of vibration environment, random vibration testing can also be performed at the subsystem and payload/spacecraft unit level.
According to this technical standard, the purpose of random vibration testing is to conform the components to the intended task environment and to provide process screening for all electrical, electronic and electromechanical components.
Random vibration testing may also be required for components whose response is affected by random vibrations of mechanical transmission resulting from the vibrational acoustic environment.
The grade and duration of the random vibration test shall be determined statistically according to the following requirements
A sine scan vibration test can also be performed at the component level when a component is suspected to be sensitive to this type of vibration environment.
According to this technical standard, sine vibration tests are conducted to simulate the low-frequency dynamic emission environment predicted by coupled load analysis (CLA) and should also be representative of the sinusoidal environment present in flight.
Sine vibration testing should also meet the requirements of the launch vehicle provider to demonstrate that the subsystem and payload/spacecraft unit can withstand the effects of the low-frequency launch environment.
Sine sweep vibration (5 to 50 hertz [Hzl) ELV and STS pavloads.Sinusoidal sweep vibration testing shall be performed to qualify hardware for the low-frequencyl (less than 50 Hz) sinusoidal transients or the sustained sinusoidal environments when they arel present in flight. These tests shall be conducted at levels that are 1.25 times the flight-limit levelsl and at a sweep rate of 4 octaves per minute. Other sweep rates may be used to provide simulations of specific flight events. The minimum probability level used to define the flight-limitl level is P97.72/50 for ELV payloads. This is equal to the mean plus 2 sigma for normal distributions. Sine vibration applies to STS payloads only if required to simulate sustained periodic environment from upper stages or apogee motors, etc. For STS payloads, the minimum probability level used to define the flight-limit level is P99.87/50. This is equal to the mean plus 3 sigma for normal distributions.
What should be considered during shaker vibration test
Before starting the test, the test fixture should be investigated for resonance up to 2000 Hz. If feasible, the fixture should not resonate in the test frequency range. The test sample shall be mounted to the fixture via its flight or flight equivalent mounting attachment.
Shaker test equipment: Select the right shaker and test equipment to meet the needs of vibration testing, and the Shaker test equipment should have sufficient load capacity and frequency response range to adapt to the size and quality of aerospace products
The control accelerometer shall be mounted on the test fixture near the connection point. If more than one control accelerometer is used, the test level can be controlled using an average or other control scheme.
Stroke length: The stroke length of the shaker test equipment should be long enough to meet the requirements of the product vibration test. Stroke length refers to the maximum displacement or range of displacement that a shaker can provide and is important for simulating different types of vibration
The standard applies to all payload hardware that NASA develops internally or under contract to launch on a single-use or reusable launch vehicle, including free vehicles and additional payloads.
NASA-STD-7002B types of vibration testing
Mechanical test
Vibration test
Thermal test
EMI/EMC testing
Functional testing
Random vibration
Unlike sinusoidal vibration testing, random vibration testing is considered mandatory at the component level.However, when it is suspected that a component is sensitive to this type of vibration environment, random vibration testing can also be performed at the subsystem and payload/spacecraft unit level.
According to this technical standard, the purpose of random vibration testing is to conform the components to the intended task environment and to provide process screening for all electrical, electronic and electromechanical components.
Random vibration testing may also be required for components whose response is affected by random vibrations of mechanical transmission resulting from the vibrational acoustic environment.
The grade and duration of the random vibration test shall be determined statistically according to the following requirements
Sine vibration
Sine sweep vibration testing is considered mandatory at the subsystem level and payload/spacecraft unit level.A sine scan vibration test can also be performed at the component level when a component is suspected to be sensitive to this type of vibration environment.
According to this technical standard, sine vibration tests are conducted to simulate the low-frequency dynamic emission environment predicted by coupled load analysis (CLA) and should also be representative of the sinusoidal environment present in flight.
Sine vibration testing should also meet the requirements of the launch vehicle provider to demonstrate that the subsystem and payload/spacecraft unit can withstand the effects of the low-frequency launch environment.
Sine sweep vibration (5 to 50 hertz [Hzl) ELV and STS pavloads.Sinusoidal sweep vibration testing shall be performed to qualify hardware for the low-frequencyl (less than 50 Hz) sinusoidal transients or the sustained sinusoidal environments when they arel present in flight. These tests shall be conducted at levels that are 1.25 times the flight-limit levelsl and at a sweep rate of 4 octaves per minute. Other sweep rates may be used to provide simulations of specific flight events. The minimum probability level used to define the flight-limitl level is P97.72/50 for ELV payloads. This is equal to the mean plus 2 sigma for normal distributions. Sine vibration applies to STS payloads only if required to simulate sustained periodic environment from upper stages or apogee motors, etc. For STS payloads, the minimum probability level used to define the flight-limit level is P99.87/50. This is equal to the mean plus 3 sigma for normal distributions.
What should be considered during shaker vibration test
Before starting the test, the test fixture should be investigated for resonance up to 2000 Hz. If feasible, the fixture should not resonate in the test frequency range. The test sample shall be mounted to the fixture via its flight or flight equivalent mounting attachment.
Shaker test equipment: Select the right shaker and test equipment to meet the needs of vibration testing, and the Shaker test equipment should have sufficient load capacity and frequency response range to adapt to the size and quality of aerospace products
The control accelerometer shall be mounted on the test fixture near the connection point. If more than one control accelerometer is used, the test level can be controlled using an average or other control scheme.
Stroke length: The stroke length of the shaker test equipment should be long enough to meet the requirements of the product vibration test. Stroke length refers to the maximum displacement or range of displacement that a shaker can provide and is important for simulating different types of vibration
