1. 3D Printed Model of the WFIRST Observatory using
Additive Manufacturing Techniques
Jeff Stewart, 543
Giulio Rosanova, 543
William Alberding1, Rosemary Davidson2, Christen McWithey3, Jonathan Ruffa4
1St. Mary's College of Maryland, 2,3University of Maryland, College Park, 4University of Maryland, Baltimore County
Engineering
Summer 2015
Organization
WFIRST Artist’s rendering WFIRST Cycle 5 CAD Model
http://coolcosmos.ipac.caltech.edu/infrared_mission
Equipment & Materials
• MakerBot® ReplicatorTM 2X Experimental 3D Printers
• Acrylonitrile Butadiene Styrene (ABS) Plastic Filament
• High Impact Polystyrene (HIPS) Dissolvable Plastic Filament
• D-Limonene Solvent
• Super Glue
• Adhesive Velcro Strips
• Stainless Steel Screws, Nuts, and Washers (2-56 thread)
Introduction
The WFIRST Mission (Wide-Field Infrared Survey Telescope) was considered top priority in the
2010 New Worlds, New Horizon Decadal Survey, and has a proposed launch date in the next decade.
It contains two instruments, a wide-field infrared imaging instrument and a coronagraph. The main
science goals are to detect evidence of dark energy, and to gather statistics on exoplanets.
WFIRST is currently a Pre-Phase A observatory project, preparing for conceptual design reviews.
In order to effectively visualize the current design concept of WFIRST, an interactive model of the
entire observatory was created for the benefit of all personnel involved in the project. Given the
amount of time and resources available, a MakerBot Replicator 2X 3D printer was identified as the
most efficient tool for production. There are five main components of the observatory that were
produced as removable sections: the spacecraft, the instrument carrier, the telescope (including the
Outer Barrel Assembly (OBA)), and the main instruments (Wide Field Instrument (WFI),
Coronagraph (CGI)). A stand was also designed to safely secure the model while on display. It was
necessary that the model be accurately downscaled, yet robust enough to withstand frequent handling
loads. To achieve the required size, the observatory was scaled down to 4% of actual size. Many
properties of the design were structurally weak and/or inadequate when scaled down. Therefore,
several parts were adjusted or redesigned to be thicker, stiffer, and more realistic for additive
manufacturing production techniques. Additionally, designated interior features of the observatory
were required to be accessible and visible. New parts were engineered to accommodate the need for
user interaction and the 3 deployable systems were designed as moving components. These are the
Solar Arrays, High Gain Antenna, and OBA Door. Due to the small size of the model, extremely
fragile pieces were redesigned [by the interns], and manufactured out of metal to prevent structural
failure. The observatory can be displayed in two configurations: stowed, the initial position during
launch; and deployed, when the Observatory is operational in space. Different types of adhesives
were used to assemble the model that demonstrates both configurations. The completed model
provides viewers with a more in-depth, hands-on understanding of the design of the WFIRST
observatory.
MakerBot® ReplicatorTM 2X Experimental 3D Printer
http://www.imakr.com/bundles/view/makerbot-replicator-2x-and-digitizer-bundle
New Designs
References & Acknowledgments
We would like thank Jeff Stewart and Giulio Rosanova for their insight and encouragement, and for
always guiding us towards the right direction. We are also grateful for the other MakerBot users in
Building 5 for sharing their 3D printing experience, and for Kevin Grady and Cathy Peddie, the
WFIRST project managers, for their continuous support.
3D Printing
Problem Solution
Warping
• Printed pieces tended to peel off
the build plate mid-print.
• ABS plastic was dissolved in a small amount of acetone.
• The ABS-acetone coating was brushed onto the build
plate prior to printing, causing the newly extruded plastic
to tightly adhere.
Heating
• The 3D printer shut off because
sensors were reading extreme
temperatures.
• The thermocouple, which heats the extruders, was
determined to contain a failing thermostat.
• Specific connections on the main electronics board were
tightened, which temporarily reestablished the
functionality of the failing thermostat.
Deployable Model Components
Requirements Solution
Solar Arrays
• When stowed, the solar arrays
fold to a 120° angle. In the
deployed configuration, they
open flat to 180°. The hinges
between the vertical panels
needed to retain the original
geometry while maintaining
proper durability.
• The small hinges were
redesigned to
constrain the
deployment angle to
180°. They were
machined out of
aluminum and then
bonded to the plastic
panels.
High-Gain Antenna
• When stowed, the high-gain
antenna system remains folded
up inside the base of the
spacecraft. To deploy, it must
extend out and tilt towards Earth.
The hinges for the model need to
be precisely dimensioned, stiff to
maintain angles, and sufficiently
robust.
• The original complex
and delicate design
was mimicked, but
was altered to boost
durability. The parts
were machined out of
aluminum. The bolts
at the hinges can be
tightened to achieve
specific angles.
OBA Door
• A movable connection was
needed between the OBA and the
OBA door. A 270° angle rotation
was necessary to open and close
the pathway of the observatory
view.
• A hinge component
was designed with 2
parallel axes of
rotation to allow
proper movement to
seal the OBA
effectively.
Model Stand
Stand
• A stand was necessary to
securely display the model when
not in use.
• A base was designed
to support the model
and lock it in an
upright position once
it is twisted into place.
Components Printing Time (Hours)
Spacecraft System (Spacecraft, Propulsion, HGAS, Solar Array) 66.75
Instrument Carrier System (IC, WFI, CGI) 47.15
Telescope System (Primary and Secondary Telescopes, Structure) 17
OBA (Main Outer Barrel, Scarf, Door) 51
Bipods (supporting IC, Telescope, and OBA) 4
Model Stand 9
TOTAL 194.90 Modified Designs
Model Components
Component Original CAD Printed Model
Spacecraft
• Removable Modules
• Deployable Solar Arrays
• Propulsion Tanks
• Deployable High-Gain
Antenna
Instruments
• Instrument Carrier (IC)
Structure
• Removable Coronagraph
• Removable Wide-Field
Instrument
• Bipods to attach to Spacecraft
Telescope
• Primary and Secondary
Mirrors
• Telescope Baffles
• Load-bearing Structures
• Bipods to attach to IC
Outer Barrel Assembly
• Main Outer Barrel
• Light-shielding Scarf
• Functioning Door
• Bipods to attach to Spacecraft
(not pictured)
Modifications Computer Model
Bipods
• The complicated, delicate joints were too small at 4%
scale.
• Bipods were redesigned to have more robust pieces as
well as stronger joints.
• The joints were then manufactured out of aluminum.
Coronagraph
• The CGI was altered between cycle 5 and cycle 6. The
cycle 6 design was chosen because it fit the parameters
of the instrument carrier.
• The full-scale design was shelled out to a thickness of 2
inches which would cause structural problems when
downscaled to 4%. The CGI design was remodeled by
removing the shell feature to solidify the component.
Element Wheel
• The element wheel is very small when scaled down to
4%. Numerous redesign iterations and printer setting
adjustments were necessary before it printed accurately.