TPF-C Technology Plan - Exoplanet Exploration Program - NASA

Chapter 4
Figure 4-11. Schematic of the Secondary Mirror Tower Structure Testbed.
4.2.2 Secondary Mirror Tower Partial Structure Testbed
Objective
The objective of this testbed is to characterize, with participation of industry, the instabilities and
nonlinear dynamics of mechanisms on a full scale hinge/latch assembly with flight-like
interfaces to a truncated SM tower, and in an environment representative of the TPF-C operating
conditions. The main concern is the existence of dynamic instabilities above 1 Hz that would
jeopardize the 300 pm SM position stability requirement. This includes sudden and repeated
energy releases (a.k.a. “snap, crackle and pop”), as well as harmonic distortions of sinusoidal
waveforms propagating through the nonlinear mechanisms. The primary objective is to validate
bounding analysis models for microdynamic behavior due to stored strain energy release at the
hinge/latch assembly. This testbed will also be used to validate analytical models of the SM
tower sub-assembly, especially with regard to the nonlinear representation and impact of the
hinge/latch, and to characterize scalability of the response to various thermo-dynamic inputs. It is
envisioned that the mechanisms, materials, and architecture of this testbed will be traceable to
the actual TPF-C flight design.
Approach
A schematic of the test facility is shown in Figure 4-11. The testbed will be housed within a
thermally controlled vacuum chamber, and vibration isolation will be provided to minimize jitter
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