Chapter 5 Robust Performance Tailoring with Tuning - SSL - MIT

Table 6.2: TPF SCI model mass breakdown.
Component Mass [kg]
Truss 850.1
Combiner 250.0
RWA (3 Ithaco E) 31.8
Collectors (4) 1547.1
TOTAL 2679.0
two arms, one that extends from the origin in the positive X-direction and one that
extends in the negative X-direction. Note from Figure 6-2(a) that the X-axis is aligned
with the interferometer baseline and the Z-axis with the observation direction. The
Y-axis completes the right-handed coordinate system. The truss is symmetric about
the origin so that the negative truss arm is simply the reflection of the positive arm.
The truss is 38 meters in length and is composed of 38 individual truss bays. Each
bay consists of nine members: three longerons, three battens forming a triangular
frame and three diagonals as shown in Figure 6-5. Each truss member is modeled
with a NASTRAN CBAR element, and the material properties are based on those of
a low-CTE (coefficient of thermal expansion) MJ55 composite (Table 6.3). The truss
design and material are based on a model from the Jet Propulsion Laboratory 2 .The
numbering scheme used for the truss elements is given in Table 6.4.
Table 6.3: Truss properties.
Name Description Value Units Source
ρ material density 1830 kg/m 3 low CTE MJ55
E Young’s Modulus 111.7 GPa low CTE MJ55
ν Poisson’s Ratio 0.3 none low CTE MJ55
r cross-sectional radius .01 m mass and frequency estimates
h batten frame height 1 m sized from mass/freq estimates
w batten frame width 2 m sized from mass/freq estimates
L truss bay length 1 m modeling convenience
2personal communication with Douglas Adams, Member of Technical Staff, Jet Propulsion Laboratory
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