NASA Technical Reports Server (NTRS) 20170012522: Habitable Exoplanet Imager Optical-Mechanical Design and Analysis

1.5 MB·English

by  NASA Technical Reports Server (NTRS)

Habitable Exoplanet Imager Optical-
Mechanical Design and Analysis
Printing:
Jonathan Gaskins – University of North Carolina at Charlotte
This poster is 48” wide by 36” high.
Mentor: H. Philip Stahl– ST-10
It’s designed to be printed on a
large
ABSTRACT METHODS RESULTS Customizing the Content:
The placeholders in this
The Habitable Exoplanet Imager (HabEx) is a space • Utilized PATRAN for finite element modeling and
formatted for you.
telescope currently in development whose mission preprocessing
includes finding and spectroscopically characterizing placeholders to add text, or click
• Modeled and meshed JPL Spacecraft BUS
exoplanets. Effective high-contrast imaging requires
• Integrated various design modifications into full an icon to add a table, chart,
tight stability requirements of the mirrors to prevent
finite element model (FEM)
issues such as line of sight and wavefront errors.
SmartArt graphic, picture or
PATRAN and NASTRAN were used to model updates in
multimedia file.
the design of the HabEx telescope and find how those
updates affected stability. Most of the structural
T
modifications increased first mode frequencies and
1% Structural Damping LOS Displacement Values
improved line of sight errors. These studies will be
from text, just click the Bullets
used to help define the baseline HabEx telescope
button on the Home tab.
design.
If you need more placeholders for
titles,
JPL Spacecraft BUS Mesh
make a copy of what you need and
Concept for Baseline HabEx Design
drag it into place. PowerPoint’s
Smart Guides will help you align it
0.05% Structural Damping LOS Displacement Values
with everything else.
First peaks of X,Y, and Z displacements are at 32.3 Hz.
BACKGROUND
The X displacement values for 1% and 0.05% damping
Want to use your own pictures
respectively are 6.4𝜇𝑚 and 15𝜇𝑚. Displacement
values for Y respectively are 9.3𝜇𝑚 and 41𝜇𝑚.
instead of ours? No problem! Just
Science Behind HabEx Technical Requirements Displacement for Z respectively are 1.7𝜇𝑚 and 7.5 𝜇𝑚.
right
• Exoplanets are difficult to directly image due to
FIRST MODE FREQUENCY OF PRIMARY
their home star’s glare which can be billions of
Mount Location vs First Mode Frequency MIRROR ASSEMBLY VS TUBE DIAMTER Change Picture. Maintain the
times brighter than the planet’s reflected light 70 60
)z 65
H 50
( yc 60 )ZH proportion of pictures as you resize
• Blocking the light from the star is possible with a ne ( Q 40
uq 55 ER
e F
coronagraph rF e 50 EDO 30 by dragging a corner.
do M
M 45 T 20
t SR
sr 40 IF
• The coronagraph has tight stability tolerances for iF 10
35
40 50 60 70 80 90 100 110 0
the optical surfaces 0 0.05 0.1 0.15 0.2 0.25 0.3
Mount Location (%)
TUBE DIAMTER (METERS)
• Technical challenges involve creating a telescope
which is stiff enough to prevent deflections of the
Full Finite Element Model, Wireframe (left)
primary mirror in the realm of nanometers
and Shaded (right)
• Utilized NASTRAN to perform dynamic and modal
analyses
• Using a prepared MATLAB script, performed line of
sight and jitter calculations
• Used a prepared Excel Workbook for applying
First mode of optical tower assembly at 28 Hz (left), First
isolation filters to data
mode of primary mirror assembly 33Hz (middle) Second
• Finite element model of the full assembly was
mode of primary mirror assembly at 34Hz (right)
constantly changing throughout the analysis process
CONCLUSIONS
• A more rigid Spacecraft BUS leads to improved
OBJECTIVES RESULTS
optical stability by an order of magnitude for some
first peaks
• Changing from 1% to 0.05% structural damping does
• Integrate JPL Spacecraft BUS • Found that the “rigid” representation of the
not increase displacements and rotations by large
Spacecraft BUS created better LOS and jitter
• Explore differences in “rigid” and flexible Spacecraft orders of magnitude
behaviors
BUS
• Tilt in the primary mirror dynamic surface figure
• Changing from 1% damping to 0.05% damping
• Find jitter and line of sight differences in changing error needs to be removed
changed displacements rotations by a factor of
from 1% to 0.05% linear structural damping
• A new MATLAB code needs to be run for the
around 14 in the worst cases for the first few peaks
• Find how to calculate primary mirror dynamic microthruster disturbance data
• Created a NASTRAN SOL 111 file (modal frequency
surface figure error
• Support structure levels off at a first modal
response) which tracked the primary mirror nodes to
• Find how to make primary mirror assembly stiffer. frequency of ~50Hz for tubes 20cm (8in) in diameter.
find the dynamic surface figure error
Tube diameter of the support structure should be The stiffness of the structure may not improve with
• Explored mounting locations of the primary mirror
explored to see if larger stiffer tubes create higher larger tube diameters due to the members of the
and found an optimal mounting location for the
first mode frequencies of the primary mirror structure approaching their maximum stiffness
current support structure design at 65% mount
assembly. Mount locations should be explored.
AKNOWLEDGMENTS
location.
Mount location is referred to as percentage radial
Thanks to my mentor Phil Stahl for helping me become part of
distance from the edge (edge mounting is 100%) • Created a new FEM to be used in the future for
this optics community and giving me help where needed.
calculating microthruster disturbances
• Find the dynamic response to reaction wheel
Thanks to Jay Garcia in the Advanced Concepts Office for
disturbances versus micro-thruster disturbances teaching me about structural analysis and engineering
everyday.