Ultra-lightweight, 200-grams CubeSat Deployer for LEO to ... · minimize stress during launch and maneuvers. •To reach this goal, we analyzed iteratively many possible configurations

Main Author

Mr. Jules Nader, Engineering Division – Ecuadorian Civilian Space Agency (EXA), Ecuador.

Co-Authors

Prof. Ronnie Nader (M2), Cosmonaut, Space Operations Division, Chief EngineerEcuadorian Civilian Space Agency (EXA), Ecuador.

Ultra-lightweight, 200-grams CubeSat Deployer

for LEO to Lunar Missions.

2nd IAA Latin American Symposium on Small Satellites:

Advanced Technologies and Distributed Systems

• Background

• Design Criteria

• Design Process

• Innovative Technologies

• Conclusions

2nd IAA Latin American Symposium on Small Satellites: Advanced Technologies and Distributed Systems IAA-LA2-09-04 2

Ultra-lightweight CubeSat Deployer

EXA-CSDEcuadorian Space Agency – CubeSat Deployer

BACKGROUND:

• In 2018, during the 69th IAC in Bremen, within the context and with the support of the IAF GRULAC, EXA

published the initiative of a Latin American Lunar Program using Astrobotic’s services to deliver payloads to

lunar orbit and ground. EXA immediately started working on the project and identified a major challenge which

is reducing the mission’s total mass budget. This became a major system driver in the development of a

deployer that can accomplish the same functions that a normal deployer can accomplish, by using less mass

and in a harsh environment.

• As announced during the 70th IAC in Washington D.C., EXA is Spacebit’s main contractor to develop and

operate the first robotic walker on the surface of the moon, as a payload of Astrobotic’s Peregrine lander.

Since the deployer is already under development, it is included as part of the project and is an important

component to reduce the mission’s total mass budget.

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2nd IAA Latin American Symposium on Small Satellites: Advanced Technologies and Distributed Systems IAA-LA2-09-04

BACKGROUND: PARTS

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Rail Pillar

Main Hull

Lid


A. A maximum weight of 200 grams for a 1U deployer.

B. Heavy load-bearing capacity.

C. Wide temperature range tolerance (-100C to +120C).

D. Radiation indifferent.

E. Scalable design.

F. A minimum clearance of 10mm.

G. Adaptability to various launch platforms.

H. Standard CubeSat compatibility.

I. Inclusion and full functionality of normal deployer systems.

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DESIGN CRITERIA:


DESIGN PROCESS: 200 GRAMS MAXIMUM WEIGHT FOR 1U

• We used a circular cavity skeletal framework.

• The material used is Titanium grade 2 at a

thickness of 1mm.

• Bulkhead area vs mass optimization processes

were applied.

• Designed for compatibility with standard

manufacturing methods and processes.

• EXA-developed ECT-1719F Composite Material was

used for crucial parts and components.

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INNOVATIVE TECHNOLOGIES: ECT-1719F

• The part denominated as rail pillar is made of EXA-

developed ECT-1719F developed during the NEE-01 PEGASUS

project, and is now put to use to enable an ultra-lightweight

deployer.

• We concluded that this piece needed to have a specific

shape and could not have any gaps within the structure,

which could affect CubeSat deployment operations.

• Normal lightweight metallic materials like aluminum or

titanium made the skeletal deployer too heavy. Space-grade

non-metals like PTFE still increased the weight significantly.

• Ultimately, the solution is to incorporate this material.

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INNOVATIVE TECHNOLOGIES: ECT-1719F

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Material Individual Mass Aggregated Mass

ECT-1719F 5.79g 23.19g

Titanium Grade 2 81.33g 325.32g

Aluminum 6061 48.69g 194.76g

Magnesium 30.66g 122.64g

Beryllium 33.25g 133g

PTFE 38.93g 155.72g


ECT-1719F Material Properties

Property Value

Young’s Modulus 9 GPa

Tensile Strength 73 MPa

Operating Temp. -180 to 500C

Density 0.3 g/cc

Friction Coeff. 0.15

DESIGN PROCESS: HEAVY LOAD-BEARING CAPACITY

• Due to the deployer’s reduced mass and hollowed bulkheads, preliminary

analysis ensued to ensure tolerance to heavy load environments.

• In order to achieve this, the design must dilute force vectors optimally to

minimize stress during launch and maneuvers.

• To reach this goal, we analyzed iteratively many possible configurations

using SolidWorks 2017 Simulation until satisfactory results were met for

preliminary design stages.

• All results generally showed that metal fatigue would not be the main

problem, but rather displacement through vibration would be the main issue.

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The iterative design process to optimize stress tolerance is:

• First, a SolidWorks 2017 static simulation with 12Gs of acceleration on 3

different axes to illustrate weak points or regions in the system.

• Second, a SolidWorks 2017 frequency analysis to determine the system’s

resonant frequencies closest to the highest point in the PSD chart

provided by Astrobotic.

• Third, a SolidWorks 2017 random vibration analysis using all resonant

frequencies up to the aforementioned critical frequency to obtain worst-

case scenario displacement and stress plots.

• Finally, an analysis to determine if a new configuration or a modification

is needed to meet preliminary requirements.

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• The maximum displacement for the acceleration forces

analysis indicated a maximum deformation of 1.659e-04mm,

preliminarily demonstrating that these forces alone are not

an issue.

• The maximum displacement for the random vibration forces

analysis indicated a maximum deformation of 2.293mm and a

main deformation of 1.1mm, indicating a potentially

problematic issue.

• However, the maximum stress on the system was 0.857GPa

while titanium grade 2 Young’s Modulus is 102.7GPa,

preliminarily demonstrating that no permanent deformation

will occur.

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Displacement Plot for Random Vibration



• In order to mitigate the displacement issue, a 1.35mm extra

clearance will be incorporated into the skeletal deployer in

order to prevent damage to the CubeSat payload inside,

elevating the total lateral physical clearance to 11.35mm.

• These results are worst case scenario and used exaggerated

data for a safe margin of error. Real tests are necessary in

order to validate these results and work with actual values.

• Vibration loads are amplified due to the fact that the skeletal

deployer is mounted on an extended plate on Astrobotic’s

Peregrine lander.

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von Mises stress plot for Random Vibration


Problems• Wide temperature ranges on lunar ground,

ranging from -100°C to +120°C.

• Rapid temperature shifts and changes at lunar dawn and dusk or during landing maneuvers.

• Both effects combined cause any material with different elements in its molecular structure to expand and contract at different rates causing weakening, fatigue, and cracks.

• Electric systems and release mechanisms may fail due to overheating or extreme cold failures.

Solutions• A metal with a low thermal expansion coefficient

and a strong molecular structure must be used to prevent mechanism failure.

• A metal with a very high purity must be used in order to prevent cracking and weakening.

• There can be no structural welding processes binding the structure to prevent cracking. The structure must be manufactured from a single metallic piece.

• SEAM/NEMEA radiation shielding and thermal control systems must be used to prevent overheating and extreme cold failures.

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DESIGN PROCESS: TEMPERATURE TOLERANCE

The metal selected is Titanium grade 2


DESIGN PROCESS: RADIATION TOLERANCE

• The skeletal deployer must be able to withstand radiation

types and intensities that are not present in LEO.

• Also, the skeletal deployer must withstand crossing the van

Allen belts during cruise operations.

• To achieve this, the skeletal deployer is covered in

SEAM/NEMEA-C shielding, designed to withstand these

radiation sources. It is also designed as part of a thermal

regulation system necessary to prevent overheating and

extreme cold failures.

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DESIGN PROCESS: SCALABILITY

• The 1U skeletal deployer is conceived as the base design,

from which elements and bulkheads can be multiplied in

length and width to conform to larger CubeSat requirements.

• Although any skeletal larger than 1U is highly theoretical, and

while these variants haven’t been developed, we have simple

CAD models that can be manufactured and developed in the

future.

• If successful, the skeletal deployer’s maiden voyage will

serve as a flight heritage precedent from which further

variants can be developed based on real data from beyond

LEO and real tests.

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DESIGN PROCESS: INDUSTRY REQUIREMENTS

It is absolutely necessary that the skeletal deployer conform to

CubeSat industry standards in order to be fully compatible with

any normal payload

• Dimensions: the skeletal deployer follows all fitting

requirements for a 1U CubeSat.

• Electrical: This aspect of the skeletal deployer is not yet

developed, but will be incorporated according to CubeSat

power and electrical interface standards.

• Thermal: Through the use of SEAM/NEMEA shielding the

skeletal deployer is expected to maintain an internal

temperature range between -10 to 10C, protecting the

payload.

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Pros:

• More mass available to the CubeSat developer for actual payload use.

• Lower launch cost to LEO and beyond.

• Designed to withstand extreme environments and heavy loads.

• A large clearance of 10mm on all sides and 15mm at the top.

• Built-in radiation shielding designed to survive outside Earth’s magnetosphere.

• Adaptable to deploy CubeSat format rovers on the moon.

Cons:

• Currently there is no flight heritage for this technology.

• Low mass also means an increased susceptibility to vibration amplitudes.

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CONCLUSIONS


Thank you for your attention.

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EXA-CSD


Ultra-lightweight, 200-grams CubeSat Deployer for LEO to ... · minimize stress during launch and maneuvers. •To reach this goal, we analyzed iteratively many possible configurations

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