Shape Memory Alloy Mechanisms for CubeSats
mechanical and fluid systems
Shape Memory Alloy Mechanisms for CubeSats (LEW-TOPS-135)
Lightweight and efficient mechanism for retention, release, and deployment of solar arrays and antennas
Overview
Innovators at NASA's Glenn Research Center have developed lightweight and reliable mechanisms based on shape memory alloys (SMAs) for small satellites, such as CubeSats. SMAs have a unique ability to effect a reversible phase transformation, so that they can withstand being severely deformed and recovered repeatedly. Glenn's innovation, flown in a successful space mission, uses SMA components in actuators and hinging elements to improve retention, release, and deployment of crucial structures, such as solar arrays. Compared to standard devices, the SMA-based mechanisms are much smaller and lighter, do not produce debris, and require minimal power to operate, meeting the rigorous power budget for CubeSats. These SMA-based components are a key breakthrough for CubeSats and other small satellites, where their small size and weight, reusability, and reliability are mission critical. In addition, these mechanisms can be scaled up, so their benefits can be realized in larger spacecraft as well.
The Technology
Most spacecraft feature release, retention, and deployment devices as key components, because these devices achieve on-demand configurability of solar panels, probes, antennas, scientific instruments, fairings, etc. Until now, designing and using such devices in small spacecraft has been a challenge, because their mass, volume, and power requirements are significant and can impose design constraints. CubeSats, in particular, often need to deploy several structures (such as solar arrays) simultaneously, which prior-art deployment devices have not been able to manage effectively. Glenn's innovation embeds SMAs within the components so the structures can be retained during launch, then released and deployed in orbit. The release and retention device is controlled by an SMA activated pin puller to disengage the release plate from the hooks holding the solar arrays. Once released, the SMA hinge is passively enabled to the deployed state. When ready on orbit, the mechanism is commanded to release and electrical power is sent to the SMA actuator, releasing the component to its deployed state. The component is deployed to its final position through the use of hinges, which are activated passively with SMA spring strips. The retention and release device and hinge are substantially smaller and lighter than deployment mechanisms have ever been and can deploy simultaneously with great reliability. Having already been successfully deployed on a NASA mission, Glenn's innovation is a game-changing technology for CubeSats and other small satellites.
Benefits
- Lightweight/compact: The SMA retention and release device weighs between 150 and 200 grams (for 3U CubeSats), and is fully scalable to smaller or bigger satellites
- Low-power: Deploys in as little as 10 seconds, using only 18 watts
- Efficient: SMA components are resettable, so they can be ground-tested several times, unlike current state of the art
- Clean and safe: Does not require additional lubrication, and (unlike pyrotechnics and burn wires) does not create debris
- Versatile: Tunable to operate in a wider range of deployment temperatures (-140 to 500°C) than previous devices, enabling missions in extreme temperature environments
Applications
- Aerospace
- Antennas
- Commercial space
- Communications
- Navigation systems
- Satellites
- Unmanned vehicles
Technology Details
mechanical and fluid systems
LEW-TOPS-135
LEW-19461-1
Similar Results
Shape Memory Alloy Rock Splitters (SMARS)
Glenn's revolutionary SMARS device is fabricated from nickel-titanium-halfnium (NiTiHf), nickel-titanium-zirconium compositions, or a combination. These compositions contain a secondary, nanometer-sized precipitate phase, which is produced through processes of compositional control and ageing heat treatments. Glenn's novel materials and processes have yielded a SMA composition that produces much higher stresses than other SMAs on the commercial market.
The SMARS device is composed of 1) SMA material as the actuating member; 2) a casing heater placed around the SMA member; 3) a DC or AC power source to provide current through the heater; 4) pointed tips for acute penetration into rock formations; and 5) a hand-press to reset the SMA element after each use. In the rock-splitting process, a hole equal to the diameter of the SMA element is drilled in the portion of the rock where the fracture is desired. Next, the pre-compressed SMA is inserted into the hole, and AC or DC current is applied to energize the devices heaters. Once the heater achieves the critical transformation temperature, the SMA will begin to expand within seconds. Since its expansion is constrained by the rock walls, the SMA will eventually exert up to 1500 MPa of stress, splitting the rock apart. When the current is removed and the heater cools, the SMA material returns to its pre-compressed state. At this point, the material can be recovered, so the process is repeatable after reshaping. The SMA actuating members were also designed to achieve displacement greater than the materials strain output. Glenns SMARS device provides high-powered rock fracturing that is controllable, reliable, and comparatively simple without the use of explosives, hydraulics, or chemicals.
How to Train Shape Memory Alloys
Glenn researchers have optimized how shape memory alloys (SMAs) are trained by reconceptualizing the entire stabilization process. Whereas prior techniques stabilize SMAs during thermal cycling, under conditions of fixed stress (known as the isobaric response), what Glenn's innovators have done instead is to use mechanical cycling under conditions of fixed temperature (the isothermal response) to achieve stabilization rapidly and efficiently. This novel method uses the isobaric response to establish the stabilization point under conditions identical to those that will be used during service. Once the stabilization point is known, a set of isothermal mechanical cycling experiments is then performed using different levels of applied stress. Each of these mechanical cycling experiments is left to run until the strain response has stabilized. When the stress levels required to achieve stabilization under isothermal conditions are known, they can be used to train the material in a fraction of the time that would be required to train the material using only thermal cycling. As the strain state has been achieved isothermally, the material can be switched back under isobaric conditions, and will remain stabilized during service. In short, Glenn's method of training can be completed in a matter of minutes rather than in days or even weeks, and so SMAs become much more practical to use in a wide range of applications.
Precipitation Strengthened
Ni-Ti-Pd Shape Memory Alloys
Shape memory alloys (SMAs) are metals that can return to their original shape following thermal input and are largely used as actuators for various applications across industries including space, aeronautics, automotive, and biomedical. These alloys can require long processing times to stabilize through repeated training cycles and suffer from loss of strength and stability during use. Precipitation strengthening (using heat treatments to grow small nanoscale regions of distinct metal phases within the base alloy) is one way to mitigate these issues.
The NASA inventors have combined a modification of typical NiTi compositions by introducing Palladium (Pd) and small amounts of other metals and specific heat treatments to produce a novel SMA with improved properties. Specifically, the alloy is inherently stable, reducing both the need for extended processing times to stabilize the metal and the possibility of failure during high numbers of actuation cycles. Further, the SMA is specifically designed to have significantly lower hysteresis (the temperature difference between the heating and cooling) than current state of the art SMAs, i.e., at or below 10°C compared to 20°C or above. These properties combine for a SMA with enhanced properties usable across various industries and applications for reliable actuation.
The related patent is now available to license. Please note that NASA does not manufacturer products itself for commercial sale.
Shape Memory Alloy (SMA)-Enabled Actuators
Actuators typically have large footprints and mass to meet the power output needed for operation, leading to design hurdles for aircraft and space applications. Innovators at NASA Glenn developed two novel actuators with different configurations of tubes of SMA to provide rotary output. The SMA tubes are deformed in their martensitic condition and when exposed to a thermal stimulus, the tubes will revert to their original state while providing rotary motion.
One variation of the innovation nests the SMA tubes within a rotary actuator imparting several technical benefits. Nested SMA tubes can decrease the length of the actuator while achieving the same twist angle. For the same actuator length, a nested configuration of SMA tubes can multiply the twist angle and improve the power output. A second variation utilizes SMA components as transmission elements in a ring drive gear to enable continuous rotation in one direction. Previous similar SMA actuators rotate in one direction while heating and the other while cooling, which can limit the output of the rotary actuator. The innovation developed by NASA allows for continuous rotation in ANY direction, thereby allowing the rotational output capability to be independent from the amount of cyclic angular twist provided by the SMA tubes.
Innovative Shape Memory Metal Matrix Composites
Shape memory alloys (SMAs) are metals that can return to their original shape following thermal input. They are commonly used as functional materials in sensors, actuators, clamping fixtures and release mechanisms across industries. SMAs can suffer from dimensional/thermal instability, creep, and/or low hardness, resulting in alloys with little to no work output in the long term. To combat these deficiencies, NASA has developed a process of incorporating nanoparticles of refractory materials (i.e., carbide, oxide, and nitride materials with high temperature resistance) into the alloys.
Using various processing methods, the nanoparticles can be effectively mixed and dispersed into the metal alloys as shown in the figure below. In these processes the SMA and refractory material powder is mixed and the refractory nanoparticles incorporated through extrusions, melting, or directly used in additive manufacturing to create parts for applications across the aerospace, automotive, marine, or biomedical sectors. The nanoparticle dispersion is a controllable method to strengthen the SMAs, increasing the hardness of the alloys, reducing the impact of creep, and improving the overall dimensional and thermal stability of the alloys.
The related patent is now available to license. Please note that NASA does not manufacture products itself for commercial sale.