Novel Radiation Shielding Material for Dramatically Extending the Orbit Life of Cubesats

materials and coatings
Novel Radiation Shielding Material for Dramatically Extending the Orbit Life of Cubesats (LAR-TOPS-250)
Z grade material for lightweight radiation shielding
Overview
The NASA Langley Research Center has developed an innovative radiation shield made by layering metal materials in the Z-shielding method. It is a new, low cost and easy to implement method to protect CubeSat electronic circuits from ionizing radiation found in Low Earth Orbits. It is estimated that this approach can extend the life of CubeSat electronics by an order of magnitude.

The Technology
A high density metal, such as tantalum or tungsten is coated onto thin aluminum sheet in precise ratios and thicknesses. The combined sheet is then easily formed into standardized enclosures compatible with CubeSat design and performance specifications.
Typical sheet of Z-Shield material prior to vault assembly Assembled into a cubesat, Shields-1. Image credit: NASA
Benefits
  • Extends the effective life of typical CubeSat missions from 3 months to years
  • An 18x reduction of total ionizing dose and removal of internal charging effects
  • Increases return on investment made in CubeSat missions. They currently fail prior to orbital decay due to radiation damage
  • The vaults and material are compatible with CubeSat dimensions and the CubeSat dispensers

Applications
  • Cubesats and Smallsats where longer functional orbit life is desired
  • Medical Imagers where lighter weight shielding is desired
Technology Details

materials and coatings
LAR-TOPS-250
LAR-19109-1 LAR-19109-1-CON LAR-19109-2-CON LAR-18586-1-CON LAR-18586-2-CON
10,600,522 11,043,311 11,621,094 10,919,650
Thomsen, Laurence.et. al. NASA's State of the Art Small Spacecraft Technology, 2021. Section 6.4 Radiation Effects and Mitigation Strategies (https://www.nasa.gov/smallsat-institute/sst-soa/structures-materials-and-mechanisms#6.4)
Similar Results
Eruopa
Atomic Number (Z)-Grade Radiation Shields from Fiber Metal Laminates
This technology is a flexible, lighter weight radiation shield made from hybrid carbon/metal fabric and based on the Z-grading method of layering metal materials of differing atomic numbers to provide radiation protection for protons, electrons, and x-rays. To create this material, a high density metal is plasma spray-coated to carbon fiber. Another metal with less density is then plasma spray-coated, followed by another, and so on, until the material with the appropriate shielding properties is formed. Resins can be added to the material to provide structural adhesion, reducing the need for mechanical bonding. This material is amenable to molding and could be used to build custom radiation shielding to protect cabling and electronics in situations where traditional metal shielding is difficult to place.
Computer-implemented energy depletion radiation shielding
The difference between Layered Energy Depletion Radiation Shielding (LEDRS) and Stacked Energy Depletion Radiation Shielding (SEDRS) is how the piece of matter, or shield, is analyzed as radiation passes through the matter. SEDRS involves using a defined and ordered stack of layers of shielding with different material properties such that the thickness and chemical properties of each material maximizes the absorption of energy from the radiation particles that are most damaging to the target. The SEDRS shielding method aims to provide the maximum level of energy absorption while still keeping shielding mass and volume low. The process of LEDRS involves using layers of shielding material such that the thickness of each material is designed to absorb the maximum amount of energy from the radiation particles that are most damaging to the target after subsequent layers of shielding. The more energy is absorbed by the shielding material, the less energy will be deposited in the target minimizing the required mass to achieve a resulting lower dose for a given geometrical feature. The LEDRS shielding method aims to provide the maximum level of energy absorption. The process for designing LEDRS views potential radiation shields as a cascade of effects from each shielding layer to the next and is helpful for investigating the particular effects of each layer. SEDRS and LEDRS can improve any technology that relies on the controlled manipulation of a radiation field by interaction with a material element.
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High Atomic Number Coatings for Fabrics
High atomic number materials, such as tantalum, do not bond well to oxygen- and hydroxyl-rich surfaces, such as glass fibers. These metals often form surface oxides when layered on glass fabric, resulting in flaking of the high atomic number material off the fabric during cutting, folding, and/or handling. To improve coating durability, this invention applies a lower atomic number metal as a tie down layer first before applying the high atomic number metal layer. The tie down layer reduces oxide formation between the substrate and the high atomic number material, promoting adhesion. Titanium has shown strong adhesion with different metals and is effective at reducing oxide formation when diffusion bonded to itself or other materials. It has been shown to be effective at improving durability when thermally sprayed onto a glass fiber fabric as a tie down layer for a subsequent tantalum layer (also applied via RF plasma spray). The titanium layer is only approximately 1 mil thick but results in strong adhesion of the tantalum layer by inter-metallic or diffusion bonding. A thermal spray process may be used, as well. This innovation enables the delivery of high atomic metal coating on glass fiber fabrics and other polymeric substrates that are lower cost, lighter weight, and durable to form a flexible cloth material with Z-graded radiation shielding. Coated samples have been produced and the technology is currently at a technology readiness level (TRL) of 4 (prototype).
On the right side of the instrument is a large mirror. It's called the 'Earth Shield.' When it's in space it blocks the heat from Earth that would otherwise heat up the instrument. On the left is the instrument's radiator. The black dot in the center of the frame is the cold calibration point. The Thermal Infrared Sensor (TIRS) will fly on the next Landsat satellite, the Landsat Data Continuity Mission (LDCM). TIRS was built on an accelerated schedule at NASA's Goddard Space Flight Center, Greenbelt, Md. and will now be integrated into the LDCM spacecraft at Orbital Science Corp. in Gilbert, Ariz. The Landsat Program is a series of Earth observing satellite missions jointly managed by NASA and the U.S. Geological Survey. Landsat satellites have been consistently gathering data about our planet since 1972. They continue to improve and expand this unparalleled record of Earth's changing landscapes for the benefit of all.
Silicon Oxide Coated Aluminized Polyimide Film Radiator Coating
The SiOx Coated Aluminized Polyimide Film Radiator Coating uses all the exposed surfaces on the six sides of a CubeSat as radiators. All the internal components are thermally coupled to the radiators. Waste heat from the internal components is transferred by conduction to the radiators through its aluminum structure or frame. SiOx thin film coated aluminized polyimide film is used as the radiator coating. Its total thickness is approximately 0.05 mm, which is predominately the polyimide film thickness. Polyimide film is known commercially as Kapton. The coating is bonded to the CubeSat exterior by using an acrylic transfer adhesive. SiOx Coated Aluminized Polyimide Film Radiator Coatings absorptance and emittance can be tailored to meet the component thermal requirements by altering the SiOx thickness. Since the SiOx is a thin film, altering its thickness has no significant effect on the total thickness of the radiator coating. An indium tin oxide (ITO) thin film can be added to make the coating conductive, if needed, without affecting the absorptance or emittance. This coating, with or without ITO, can be used for various CubeSat applications. By tailoring the absorptance and emittance of this coating, external MLI blankets and active heater control are eliminated. The thermal connection between heat generating components and the battery eliminates the need for a battery heater.
Space cube installed on Space Station.
Novel Antenna Concept for CubeSat Platforms
The side walls and railing rods of a CubeSat are replaced by RF radiators that double as supporting structures. The RF radiators are hollow railing rods with inner dimensions that function as a waveguide to carry RF energy at a desired frequency. Radiating slots are cut on two of the four sides of hollow tubes tube that are open to outside environment. Different operating frequency antennas may be placed at each of the Cubesats four corners. Thus the railing rods provide RF antenna functionality in addition to structurally supporting the CubeSat structure. While this technology was designed for Cubesats, it may be utilized in any technology that utilizes a structural frame. The advantages of this system are increased reliability due to the elimination of deployment mechanisms and decreased payloads. Higher frequency antennas with increased gain and directivity may be embedded into the rails. These higher frequencies are especially useful for remote sensing.
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