ESA/ACT Science Coffee presentation of Nov 3, 2023 by Jonathan Sauder (NASA/JPL/CalTech) Abstract: In the past decade CubeSats have evolved from small university educational opportunities to industry and governments using them make new discoveries and monetize space. While originally most missions were restricted to Low Earth Orbit (LEO), CubeSats have begun to increase their reach across the solar system with the advent of Mars Cube One (MarCO) in 2018. However, with the small, constrained CubeSat form factor there is often a need to expand the CubeSat through deployable mechanical systems once the satellite is in space. In reviewing many CubeSat missions, it has been found that over 90% have deployable structures actuated by a mechanical system. These include antennas, solar panels, and instrument booms. There is a key challenge in CubeSat mechanism design, as one can not just shrink larger spacecraft mechanisms down to the CubeSat form factor. Rather, these mechanisms must be designed in a way to reduce complexity, which means good mechanical design principles are paramount. From experience designing the deployment mechanisms for the MarCO and RainCube missions, working on deployable antenna technology, and reviewing deployables used on hundreds of other CubeSats, several key principles have been identified for developing miniaturized mechanical systems for mechanisms. These principles will be discussed in the presentation, and examples will be provided. Small satellite missions can be made more robust by incorporating good design principles into future miniaturized mechanical systems, which in turn with result in greater reliability of small satellites. This is especially important given that many small satellites have mission critical deployables, and the ever-increasing number of interplanetary small satellite missions and opportunities.

1. MINIATURIZING MECHANICAL SYSTEMS FOR CUBESATS:
DESIGN PRINCIPLES AND LESSONS LEARNED
JONATHAN SAUDER, JET PROPULSION LABORATORY, CALIFORNIA INSTITUTE OF TECHNOLOGY
SPECIAL THANKS TO: NACER CHAHAT, MANAN ARYA, SERGIO PELLIGRINO,ALEX WEN

2. BACKGROUND
 Developing a number of deployment
mechanisms for a number of
SmallSats/CubeSats including antennas for
RainCube and MarCO
 Review of the first decade of CubeSats
revealed that 90% had deployment
mechanisms.
 Participating in the team which updated
NASA Standard 5017 for mechanisms.
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© 2023 CALIFORNIA INSTITUTE OF TECHNOLOGY. GOVERNMENT SPONSORSHIP ACKNOWLEDGED. 2

3. MECHANICAL LESSONS LEARNED FROM SEVERAL PROJECTS/TASKS
Parabolic Antennas
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Reflectarray Antennas CalTech DOLCE Solar Array
© 2023 CALIFORNIA INSTITUTE OF TECHNOLOGY. GOVERNMENT SPONSORSHIP ACKNOWLEDGED.

4. SIMPLE ARCHITECTURES + LARGE MARGINS
 Design with significant margins.
 It is not unreasonable to expect up to 200 G’s (especially for low mass parts)
 For actuation force 3X minimum in early stages of design 2X in later design stages.
 Not reliant on momentum, adequate margin to maintain motion.
 What is the simplest approach that can do the job?
 Many Smallsats use a bent tape measure and burn wire.
 Be wary of complex failure avoidance approaches.
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© 2023 CALIFORNIA INSTITUTE OF TECHNOLOGY. GOVERNMENT SPONSORSHIP ACKNOWLEDGED.
PRE-DECISIONAL INFORMATION -- FOR PLANNING AND DISCUSSION PURPOSES ONLY
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M-cubed/COVE

5. APPROACHESTO INCREASE MARGINS
Find “Free” Margin
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© 2023 CALIFORNIA INSTITUTE OF TECHNOLOGY. GOVERNMENT SPONSORSHIP ACKNOWLEDGED. 6
Self Help
Kickoff Springs
Motor, Lead Screw and Leverage
RainCube
What costs very little to increase
performance for your spacecraft?
Using geometry to create or
increase forces.
Extra force to get motion started, but
don’t rely on momentum they create.
Overcenter Mechanism and Kickoff Springs
DOLCE
Thermal Design Margin
Europa Magnetometer

6. ROTARY MOTION, MOMENT ARM AND STRUCTURAL DEPTH
Use rotary motion over sliding
Rotary motion significantly reduces the effect of friction,
which a vary widely at temperatures and in vacuum.
Fully use depth and moment arm
Depth has a linear effect on accuracy and a squared
impact on structural stress/stiffness.
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© 2023 CALIFORNIA INSTITUTE OF TECHNOLOGY. GOVERNMENT SPONSORSHIP ACKNOWLEDGED. 7

7. IFYOU MUST SLIDE LINEARLY, ENSURE L/D>2
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© 2023 CALIFORNIA INSTITUTE OF TECHNOLOGY. GOVERNMENT SPONSORSHIP ACKNOWLEDGED. 8
Inadequate L/D jammed antenna on deployment.

8. PROTOTYPE EARLY AND OFTEN
Empathize
Define
Ideate
Prototype
Test
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© 2023 CALIFORNIA INSTITUTE OF TECHNOLOGY. GOVERNMENT SPONSORSHIP ACKNOWLEDGED. 10
“They that build the most prototypes win”
-Justin Koch
Design Thinking Method

9. SOME FURTHER NOTES ON DESIGN THINKING
Empathize
Define
Ideate
Prototype
Test
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© 2023 CALIFORNIA INSTITUTE OF TECHNOLOGY. GOVERNMENT SPONSORSHIP ACKNOWLEDGED. 11
Don’t jump to answers, ensure you are asking
the right question first.You need to spend half
the time understanding the problem, to
ensure you are solving the right problem.
Build experience quickly by trying and failing
early and often.
Don’t prototype everything all at once.
Know why the prototypes fail.
Make the cost of failure low. High failure
cost will result in sunk cost fallacy.
Solve functions dependently, don’t have one
design aspect performing too many jobs.

10. PROTOTYPE EARLY AND OFTEN
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Fail Early, Fail Cheaply, Fail Often = Rapid Progress
Don’t prototype everything at once and understand why the system fails.

11. SOME FURTHER NOTES ON DESIGN THINKING
Empathize
Define
Ideate
Prototype
Test
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© 2023 CALIFORNIA INSTITUTE OF TECHNOLOGY. GOVERNMENT SPONSORSHIP ACKNOWLEDGED. 13
Don’t jump to answers, ensure you are asking
the right question first.You need to spend half
the time understanding the problem, to
ensure you are solving the right problem.
Build experience quickly by trying and failing
early and often.
Don’t prototype everything all at once.
Know why the prototypes fail.
Make the cost of failure low. High failure
cost will result in sunk cost fallacy.
Solve functions dependently, don’t have one
design aspect performing too many jobs.

12. AVOID GOING STRAIGHT TO CAD… SKETCH FIRST
 Hand sketches
 Higher Fidelity Options
 Hybrid Hand Sketches
 (w/ CAD constraints )
 PowerPoint CAD
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© 2022, Jonathan Sauder
Image: NASA/JPL/Caltech

13. Hot impacts electronics, cold impacts mechanism grease
TEST ASYOU FLY, AS EARLY AS PRACTICAL
Thermal vacuum has broad impacts Testing with S/C like interface early is critical
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Current draw was recorded in only 2 out of 7
occurrences due to non-flight software.
✓
X
✓

14. TEST ASYOU FLY EXAMPLE
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DynamicsTest Electrical
EMI/EMCTests
ThermalVacuum
Test
FunctionalTest

15. CONCLUSIONS
 When you are building miniaturized mechanisms on a tight budget, following good design practices is imperative.
 Several key “rules of thumb” are:
 Design for simple architectures with large margins
 To increase margin, use kickoff springs, self help, and find inexpensive margin in the design.
 Use rotary motion and moment arms to your advantage, with structural depth.
 If you must slide linearly, ensure an L/D > 2
 Prototype early and often, to fail quickly cheaply, to rapidly learn and develop.
 Test as you fly as early as possible.
 Involve external reviewers early, as they can see things which may not be obvious.
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© 2023 CALIFORNIA INSTITUTE OF TECHNOLOGY. GOVERNMENT SPONSORSHIP ACKNOWLEDGED. 17

16. Questions?
 The research was carried out at the Jet Propulsion Laboratory, California Institute ofTechnology, under a contract with
the National Aeronautics and Space Administration (80NM0018D0004).The cost information contained in this
document is of a budgetary and planning nature and is intended for informational purposes only. It does not constitute a
commitment on the part of JPL and/or Caltech.
 Special thanks to:
 RainCube/KaPDA:Brian Hirsch, Brian Merrill (SMMS), Jeff Harrell, Pedro Moreira,Taryn Bailey, Hugo Rodriguez, Leah Ginsberg
(intern), David Hunter (intern),Ted Steiner (intern)
 OMERA/MarCO: Nacer Chahat, Manan Arya,Vinh Bach, Phil Walkeymeyer, EllenThiel, Sean Dunphy, Mengjan Shi, Greg Agnes,Tom
Cwik, Brian Merrill (Spectrum Marine and Model Services), MichelWilliam, andTyler Luchik who assisted in building the antenna, and
Dr. Jefferson Harrell who performed the RF tests.
 DOLCE:AlexanderWen,Alan Truong, Charles Sommer,Terry Gdoutos, Sergio Pellegrino
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17. BONUS CONTENT

18. SOME FURTHER NOTES ON DESIGN THINKING
Empathize
Define
Ideate
Prototype
Test
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© 2023 CALIFORNIA INSTITUTE OF TECHNOLOGY. GOVERNMENT SPONSORSHIP ACKNOWLEDGED. 20
Don’t jump to answers, ensure you are asking
the right question first.You need to spend half
the time understanding the problem, to
ensure you are solving the right problem.
Build experience quickly by trying and failing
early and often.
Don’t prototype everything all at once.
Know why the prototypes fail.
Make the cost of failure low. High failure
cost will result in sunk cost fallacy.
Solve functions dependently, don’t have one
design aspect performing too many jobs.

19. CONCEPT FOR AVENUS ROVER
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20. DON’T PROTOTYPE EVERYTHING ALL AT ONCE
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GOVERNMENT SPONSORSHIP ACKNOWLEDGED.
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Generator
SiC or GaN Transceiver
SiC and GaN
Instruments
Wind Turbine
Distributed
Mechanical
Sensors Array
NaCl
Batteries
Reversing
Gearbox
Front
Wheels
Rear Wheels
Steering
Generator
Cond.
Battery
Cond.
M
U
X
Gear Ratio (down)
Differential
Gear Ratio
(up)
Clutch
Power Controls
Clock
Voltage
Regulator
Mechanical Electrical
Short-Term
Course
Correction
Long-Term
Guidance
Motor
Wind Vane
Stored Spring Energy

21. PROTOTYPED ROVER
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© 2023 CALIFORNIA INSTITUTE OF TECHNOLOGY. GOVERNMENT SPONSORSHIP ACKNOWLEDGED. 23

22. WHY START ROUGH?
 Lets say I want to measure the diameter of a quarter, I could use:
 A yardstick: Cost: $1s Time: 5s
 A calipers: Cost: $10s Time: 15s
 A micrometer: Cost: $100s Time: 30s
 A laser microscope:Cost: $10,000s Time: Min.
 Which do you choose?
 Depends where you are
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© 2022, Jonathan Sauder

23. SOME FURTHER NOTES ON DESIGN THINKING
Empathize
Define
Ideate
Prototype
Test
4/18/2023
© 2023 CALIFORNIA INSTITUTE OF TECHNOLOGY. GOVERNMENT SPONSORSHIP ACKNOWLEDGED. 25
Don’t jump to answers, ensure you are asking
the right question first.You need to spend half
the time understanding the problem, to
ensure you are solving the right problem.
Build experience quickly by trying and failing
early and often.
Don’t prototype everything all at once.
Know why the prototypes fail.
Make the cost of failure low. High failure
cost will result in sunk cost fallacy.
Solve functions dependently, don’t have one
design aspect performing too many jobs.

24. AVOID COUPLING IN SOLUTIONS
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© 2022, Jonathan Sauder
Functions
Design Parameters
R Lever L Lever
Speed X X
Direction X X
Functions
Design Parameters
Pedal Wheel
Speed X
Direction X
Images from Consumer Reports
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25. EXAMPLE: COUPLED FORM IS OK
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© 2022, Jonathan Sauder
Functions
Design Parameters
Hot
Knob
Cold
Knob
Flow X X
Temperature X X
Functions
Design
Parameters
Height Angle
Flow X
Temperature X
Images from Amazon.com
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26. SEPARATE STIFFNESS AND STRENGTH (12)
 Stiffness in reliant on material and geometry.
 Strength is reliant on material and geometry.
 This is a coupling issue!
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© 2022, Jonathan Sauder
Functions
Design Parameters
Steel Triangle
Stiff Structure X X
Strong Structure X X
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27. SEPARATING STIFFNESS AND STRENGTH
 Know your actual requirements
 A stiff structure does not always need to be strong (optics, eg. MOIRE)
 A strong structure does not need to be stiff (Fort Moultrie, Palmetto Logs)
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© 2022, Jonathan Sauder
South Carolina State Museum
DARPA
29

28. SEPARATE STIFFNESS AND STRENGTH (12)
 Just because something is stiff, doesn’t mean it is strong enough, and just because it is strong, doesn’t mean it is
stiff enough.
 In fact, stiffness can kill your design! (CTE)
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© 2022, Jonathan Sauder 30

29. INTERFACE THATWAS TOO STIFF
 Press fit with different stainless steels.
 440 series (martensitic) vs. 300 series (austenitic)
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© 2022, Jonathan Sauder
303: 17.3*10-6 mm/mm°C
440C: 10.1*10-6 mm/mm°C
31

30. STIFF INTERFACE: JPL EXAMPLE
 Stainless Steel
 E = 210 GPA
 EA 9360 Epoxy
 E = 3.36 GPA
 And we athermalized the design!
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© 2022, Jonathan Sauder 32

31. ATHERMALZING A DESIGN
 Use a material with vastly different CTE to result in a near zero change between the other materails.
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© 2022, Jonathan Sauder
303: 17.3*10-6 mm/mm°C
440C: 10.1*10-6 mm/mm°C Epoxy: 60*10-6 mm/mm°C
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32. EXACTLY CONSTRAIN DESIGNS
 Exact Constraint can avoid the coupling between stiffness and strength.
 Underconstraint Issues
 Location is not defined
 Has degrees of freedom which can lead to rattling.
 Overconstraint Issues
 Tolerances need to line up perfectly or they will introduce stress to the design.
 CTE will wreak havoc on your design
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© 2022, Jonathan Sauder 34

33. CONSTRAINTS AND DEGREES OF FREEDOM
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 A plane is really 3 contact points.
 A line is really 2 contact points.
 So when thinking about
constraints, think about points of
contact.
 The definition of the constraint
line created by a constraint.
 Each constraint creates a line
perpendicular to its contact point
with the object.

34. WHATTYPE OF CONSTRAINT DO THE KINEMATIC
MOUNTS PROVIDE?
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© 2016, Jonathan Sauder
3 Kinematic Mounting Features (6
points of contact) In Hinge Joint
Nesting force from torsion spring
Hinge Pin
X
Hinge Pin

35. LOOKING AT THE 2D CASE
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36. LOOKING AT THE 2D CASE
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© 2016, Jonathan Sauder
1
2
3
1-2
2-3
1-3

37. LOOKING AT THE 2D CASE
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© 2016, Jonathan Sauder
1
2
3
1-2
2-3
1-3
CCW
CCW
CW

38. LOOKING AT THE 2D CASE
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© 2016, Jonathan Sauder
1
2
3
1-2
2-3
1-3
CCW
CCW
CW

39. LOOKING AT THE 2D CASE
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© 2016, Jonathan Sauder
1
2
3
1-2
2-3
1-3
CCW
CCW
CW

40. LOOKING AT THE 2D CASE
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© 2016, Jonathan Sauder
1
2
3
1-2
2-3
1-3
CCW
CCW
CW

41. WHATTYPE OF CONSTRAINT DO THE
KINEMATIC MOUNTS PROVIDE?
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© 2016, Jonathan Sauder
X
Hinge Pin
3 Kinematic Mounting Features (6
points of contact) In Hinge Joint
Nesting force from torsion spring
Hinge Pin
✓ ✓
X
X

42. THE ECCENTRIC HINGE
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© 2016, Jonathan Sauder