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Researchers Run Simulation Tests on Their 3D Printed CubeSat Before LEO Mission

A pair of researchers from Shantou University in China explored designing and manufacturing a CubeSat with 3D printing, which we have seen in the past. CubeSats, which are basically miniaturized satellites, offer plenty of advantages in space exploration, such as low cost, a short research cycle, and more lightweight construction, but conventional methods of manufacturing often negate these. Using 3D printing to make CubeSats can help achieve accurate details as well.

[Image: ESA]

The researchers, Zhiyong Chen and Nickolay Zosimovych, recently published a paper on their work titled “Mission Capability Assessment of 3D Printing Cubesats.”

“With the successful development of integrated technologies, many spacecraft subsystems have been continuously miniaturized, and CubeSats have gradually become the main executors of space science exploration missions,” they wrote.

The main task driving research paper is an LEO, or Low Earth Orbit, CubeSat mission, which would need to accelerate to a maximum of 5 g during launch.

“…the internal operating temperature range of the CubeSat is from 0 to 40 °C, external temperature from -80 to 100 °C,” the researchers explained.

During the design process, the duo took into account environmental factors, the received impact load during the launch process, and the surrounding environment once the CubeSat reached orbit. Once they determined the specific design parameters, ANSYS software was used to simulate, analyze, and verify the design’s feasibility.

PLA was used to make the mini satellite, which is obviously shaped like a cube. Each cube cell, called a unit, weighs approximately 1 kg, and has sides measuring 10 cm in length.

“The framework structure for a single CubeSat provides enough internal workspace for the hardware required to run the CubeSat. Although there are various CubeSat structure designs, several consistent design guidelines can be found by comparing these CubeSats,” the researchers wrote about the structure of their CubeSat.

These guidelines include:

a cube with a side length of 100 mm
8.5 x 113.5 mm square columns placed at four parallel corners
usually made of aluminum for low cost, lightweight, easy machining

The CubeSat needs to be big enough to contain its power subsystem (secondary batteries and solar panels), in addition to the vitally important thermal subsystem, communication system for providing signal connections to ground stations back on Earth, ADCS, and CDH subsystems. It also consists of onboard antennae, radios, data circuit boards, a three-axis stability system, and autonomous navigation software.

“The adoption of this technology changes the concept of primary and secondary structure in the traditional design process, because the whole structure can be produced at the same time, which not only reduces the number of parts, reduces the need for screws and adhesion, but also improves the stability of the overall structure,” the pair wrote about using 3D printing to construct their CubeSat.

The mission overview for this 3D printed CubeSat explains that the device needs to complete performance tests on its camera payload for reliability evaluation, and test the effectiveness of any structures 3D printed “in an orbital environment.”

The Von mises stress diagram of the CubeSat structure.

In order to ensure that it’s ready to operate in LEO, the CubeSat’s structures was analyzed using ANSYS’ finite element analysis (FEA) software, and the researchers also performed a random vibration analysis, so that they can be certain it will hold up under the launch’s impact load.

“The CubeSat structure is validated by the numerical experiment. During launch process, CubeSat will be fixed inside the P-Pod, and the corresponding structural constraints should be added to the numerical model. In addition, the maximum acceleration impact during the launch process should also be considered. Static Structural module of ANSYS is used for calculation and analysis, the results show that the maximum stress of CubeSat Structure is 8.06 MPa, lower than the PLA yield strength of 40 Mpa,” the researchers explained.

Running in LEO, the 3D printed CubeSat will go through a 100°C temperature change, and the structure needs to be able to resist this, so the researchers also conducted a thermal shock test, which showed an acceptable thermal strain.

The thermal strain diagram of the CubeSat structure.

The team also conducted random vibration simulation experiments, so they could conform the structure of the 3D printed CubeSat to emission conditions. They simulated typical launch vibration characteristics, using NASA GEV qualification and acceptance as reference.

“The specific contents of the experiment include “Harmonic Response” and “Random Vibration”. Two identical harmonic response were performed before and after the random vibration test to assess the degree of structural degradation that may result from the launch load,” the researchers explained.

“This experiment helps us to evaluate the natural frequency of the structure, and the peak value indicates that the tested point (bottom panel) has reached the resonant frequency.”

Pre/Post Random Vibration test comparison between the curves of Harmonic Response.

As seen in the above figure, both the trend and peak points of the two curves are close to each other, which shows that there was no structural degradation after the vibration test, and that the structure itself conforms to launch stiffness specifications.

“As the primary performer of today’s space exploration missions, the CubeSat design considers orbit, payload, thermal balance, subsystem layout, and mission requirements. In this research, a CubeSat design for performing LEO tasks was proposed, including power budget, mass distribution, and ground testing, and the CubeSat structure for manufacturing was combined with 3D printing technology,” the researchers concluded.

“The results show that the CubeSat can withstand the launch loads without structural damage and can meet the launch stiffness specification.”

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AFRL and University Partners Used 3D Printed Composite Materials to Make Structural Parts

The Air Force Research Laboratory (AFRL), located at Wright-Patterson Air Force Base (WPAFB) near my hometown of Dayton, Ohio, has long been interested in using 3D printing and composite materials for the purposes of aerospace applications. Last year, AFRL’s Composites Branch at the Materials and Manufacturing Directorate partnered up with researchers from the University of Arkansas, the University of Miami in Florida, Louisiana Tech University, and the University of Texas at El Paso (UTEP) to work on advancing 3D printable composite materials.

The Composites Branch works on the research and development of organic and ceramic matrix composite technologies for legacy, developmental, and future Air Force system components. Together with its university partners, the AFRL branch demonstrated 3D printed composite materials, made from a combination of carbon fiber and epoxy, which had been successfully fabricated and used to make structural parts on both air and space craft. The results of this 3D printed composite material effort will soon be published in a special issue of the Journal of Experimental Mechanics that’s dedicated to the mechanics of 3D printed materials.

Dr. Jeffery Baur, leader of the Composite Performance Research Team, said, “The potential to quickly print high-strength composite parts and fixtures for the warfighter could be a tremendous asset both in the field and for accelerating weapon system development.”

Composite materials are made up of two, or sometimes more, constituent materials that have very different chemical or physical properties. When combined, these components produce a new material that has characteristics which are different from the originals. The individual components that make up the composite will remain distinctly separated within the final material structure.

When compared to the more low-quality polymers that are typically used in 3D printers, the composite materials demonstrated by AFRL and its partners are the same type that are already being used to make Air Force system components. These materials are very strong, while also lightweight, and have higher thermal and environmental durability than most.

Most traditional epoxy and carbon fiber composites are made by layering carbon fiber sheets, coated with epoxy resin, on top of each other. Then, the whole thing is cooked for hours in a costly pressure cooker to finish. The major downside to this method is that it’s more difficult to create parts that have complex shapes when sheets are being used.

This is where additive manufacturing comes in. Composite materials that are 3D printed are able to create parts with those complex shapes, and additionally don’t require the use of long heating cycles or expensive pressure cookers. On a materials level, there aren’t a whole lot of downsides to using composites for the purposes of producing, assembling, or repairing parts for the Air Force, whether at the depot or out in the field.

Military branches in other countries are also seeing the benefit of 3D printable composite materials. For example, engineers in India are manufacturing complex core structures using the composite 3D printing process; when combined with top and bottom face sheets, these structures will create lightweight sandwich structures that have properties tailored specifically to, as AFRL put it, “the physical forces that need to be carried.”

Conventionally fabricated sandwich structures use the same core geometries over the entire area of an aircraft skin, but a 3D printed version would be able to stand up under heavier forces when necessary, while also remaining lightweight in other parts of the skin.

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[Source: Dayton Daily News]

Update On Made In Space’s 3D Printed Asteroid Spacecraft Research

California 3D printing and space technology firm Made In Space is responsible for such out of this world innovations as the first commercial 3D printer on the International Space Station, the multi-armed 3D printing space robot Archinaut, and the manufacture of the first extended 3D printed objects in a space-like environment. The company works closely with NASA, and two years ago received funding from the agency for its ambitious plan to turn asteroids into autonomous spaceships, which could help NASA finalize its long-term goal of constructing human colonies in space.

Right now, NASA can only bring back small pieces of space rock. But Project RAMA (Reconstituting Asteroids into Mechanical Automata) hopes to establish the concept feasibility of using analog computers and mechanisms – along with 3D printing – to convert asteroids into huge mechanical spacecraft, which could carry large amounts of raw asteroid material. This could be the impetus for the off-Earth mining that will be necessary if humanity wants to survive and thrive among the stars.

Artist’s illustration of an asteroid that has been turned into a giant mechanical spacecraft, which could fly itself to a mining outpost. [Image: Made In Space]

Asteroids are pretty cool – many of them contain valuable resources, such as water and platinum-group metals, and roughly 100 tons of asteroid and comet material hit the Earth’s atmosphere each day. As part of the plan to turn these massive rock formations into functioning spacecraft, Made In Space plans to send an advanced, robotic seed craft out to space, in order to to meet with several near-Earth asteroids.

This craft would then harvest space rock material and turn it into feedstock, which can be 3D printed to build energy storage, navigation, propulsion, and other important systems on-site. Once the converted asteroid is ready, it can be programmed to autonomously fly to a mining station; according to Made In Space representatives, this approach is far more efficient than having to launch new capture probes out to space rocks.

While we don’t currently have the ability or the technology to 3D print something like a digital guidance computer with materials found on an asteroid, Made In Space realized that one doesn’t have to rely on digital electronics if a huge amount of raw material, with no constraints on mass or volume, is available instead.

“At the end of the day, the thing that we want the asteroid to be is technology that has existed for a long time,” said Made In Space Co-Founder and CTO Jason Dunn. “The question is, ‘Can we convert an asteroid into that technology at some point in the future?’ We think the answer is yes.”

Two years ago, NASA’s Innovative Advanced Concepts (NIAC) program, which encourages development of space-exploration technologies, awarded Made In Space a $100,000 Phase 1 grant for nine months of initial feasibility studies. During this phase, the company focused on how the seed craft would have to work, defining its requirements, and building a technological roadmap. If the company chooses, it can also apply for a two-year, $500,000 Phase 2 award for continuing concept development. In the meantime, Made In Space is counting on NASA to push forward in-situ resource utilization (ISRU) – the art of living off the land, which is necessary for astronauts who could someday live on planetary outposts.

Required capabilities of the RAMA craft, arranged in approximate order of mass requirements, showing the source of the materials used to provide each capability as assumed for the rest of this study.

These asteroid ships will probably not look much like traditional spaceships, with their electronic circuitry and rocket engines, but instead would use analog computers and a catapult type of propulsion system that will launch asteroid material in a controlled way. By using mass drivers to shoot chunks of itself in one direction, an asteroid could potentially accelerate itself in the opposite direction. While this method is only about 10% as efficient as a chemical rocket engine, the propellant is free.

3D printing could be used to make some of the asteroid spacecraft parts, like flywheel gyros for guidance and stabilization, tanks for storing volatile materials, and solar concentrators to generate mechanical power through the release of pressure to open the tanks.

While Project RAMA is still moving forward, Dunn acknowledges that its completion is still way in the future…and that eventually, it could even have applications on Earth.

Dunn explained, “The anticipation is that the RAMA architecture is a long time line, and when it becomes capable is about the same time that people really need the resources.

“You could build infrastructure in remote locations somewhat autonomously, and convert resources into useful devices and mechanical machines. This actually could solve some pretty big problems on Earth, from housing to construction of things that make people’s lives better.”

Diagram of an asteroid that has been converted into a mechanical spacecraft by a robotic “Seed Craft.” [Image: Zoe Brinkley]

The other goal of Project RAMA is to be able to make asteroids into self-assembled spacecraft.

“One of the big questions is, how do you take today’s most intricate machines and make them replicate themselves? That seems really hard: how do you replicate electronics and processing units and so on,” Dunn said. “And that’s when we had this concept that there are types of machines that could potentially be easy to self-replicate, and those would be very basic, analog type devices. The problem is if you have a small mechanical machine, it’s not very useful. But what if the machine itself was the size of an asteroid? What could you do with a mechanical machine that large?”

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