National Aeronautics and Space Administration

www.nasa.gov

NASA Engineering and Safety Center Technical Bulletin No. 15-02

Sine Burst (SB) Testing is used for strength testing of aerospace hardware as an alternate to static pull and 

centrifuge tests. The main advantage is that testing can be implemented while hardware is on the shaker for 

other tests. It also imposes a lower number of cycles on the hardware compared with a sine dwell or sweep, 

and is particularly suitable for relatively stiff components or electronics boxes, instruments, or spacecraft. 

Identified risks can be mitigated by best practices.

Best Practices for Use of Sine Burst Testing 

Background of SB Testing 

In the late 1980’s, the SB method was used as a means to impart 

a static load into a component, instrument, or relatively small/stiff 

spacecraft. The shaker controller is used to apply an enveloped 

sinusoidal base drive acceleration to the item at a fixed frequency 

with 5-10 cycles at peak level as shown in the Figure. The test 

frequency is such that the item response would be pre-resonant 

or as close as possible to the rigid body mode, usually being 

no more than 1/3 of the first mode frequency of the test article. 

Because the test article is being accelerated as a rigid body, a 

uniform inertial body load is generated in the test article. 

Limitations and Risk

of SB Testing 

To achieve the target stresses in some areas 

of the hardware, an over-test may need to be 

imparted in other areas. Therefore, pre-test 

analysis is required to verify the stress targets 

can be achieved within acceptable levels of 

over-test. Also, if the required load case is 

unidirectional (say compression), there will 

be a reversal load (tension) imparted on the 

article or vice-versa. This is a single axis test 

so different orientations of the test article

may be required to achieve strength qualification. There is 

a need to monitor the test article for any unexpected dynamic 

amplification, especially if the applied frequency does not meet 

the 1/3 of natural frequency guideline.

SB Testing Risks can include:

� Impacting the shaker stops by exceeding the shaker maximum 

displacement or stroke.

� Shaker stiction: The controller computes a linear transfer 

function of acceleration to update the drive for the next level. If 

the shaker has any stiction (non-linear behavior) at the targeted 

test levels, the updated drive may be higher than required and 

impart an unintended over-test. 

� An unintended operator action or controller setting, which 

drives the amplifier to an over-test. 

� Drive signal adjustments: If the test procedure is such that 

intermediate levels require engineering adjustments to the drive 

signal, the risk is a wrong calculation of this adjustment and 

would lead to an unintended over-test. 

� Lack of independent test over-protection system.

� Incorrect software version in the drive controller.

Best Practices for SB Testing 

Consider these best practices during the planning and 

execution phases:

1) Given the impulsive nature of SB testing, do not count on 

the shaker displacement soft shut down (SSD) switch and set a 

proper SB frequency high enough not to exceed the displacement 

that triggers the SSD.

2) Drive adjustments made by engineering personnel should be 

independently checked and the test sequence should be restarted 

from the lower levels.

3) Avoid using SB testing at high levels 

of assembly or on a complete flight unit. 

The preference is to use the method with 

engineering test units, which usually 

comprise the structure under test with 

mass simulators.

4) Develop metrics for routinely assessing 

the mechanical “health” of the shaker and 

slip table systems. 

5) Evaluate the drive signal magnitude and 

the coherence function estimate between 

the drive and control accelerometer prior 

to test continuation. Coherence in the frequency band close to the 

SB frequency should not be lower than 0.9.

6) Perform a checkout with a mass mockup and compare 

recorded drive signal voltages at each level during the actual 

test. Ensure adequate test planning between the analysts, the 

test engineers, and operators.

7) Review and understand the time history acceleration and or 

force data collected after each test run, including the controller 

drive voltage and amplifier output time histories. 

8) Reconsider testing via SB any hardware that is inherently nonlinear, unless the non-linear nature is understood and accounted 

for in the pre-test analysis.

9) If any of the risk mitigations fail or a new flaw is discovered, 

the final defense resides in the use of an independent over-test 

protection system along with hardware positive margin of safety 

for the abort setting.

References

1) NASA Report on High Energy Solar Spectroscopic Imager 

(HESSI) Test Mishap, (Washington, D.C.: NASA Headquarters, 

Code S, May 2000)

2) LADEE Spacecraft, Type C Mishap, IRIS Case Number: S–2012–

124–00008

Acceleration [g]

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Acceleration [g]

Time [sec]

15 Hz, 12 g Sine Burst 

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Time [sec] 

15 Hz, 12 g Sine Burst