"Not only did NASA JPL save time and money by producing these antenna arrays with FDM, they validated the technology and material for the exterior of a spacecraft, paving the way for future flight projects.”
Due to COSMIC-1’s success, U.S. agencies and Taiwan have been working on a follow-up project called FORMOSAT-7/COSMIC-2 that will launch six satellites into orbit in late 2016 and another six in 2018. NASA’s Jet Propulsion Laboratory (JPL) has developed satellite technology to capture a revolutionary amount of radio occultation data from GPS and GLONASS that will benefit weather prediction models and research for years to come.
COSMIC-2 design and development began in 2011 at JPL. Critical components of the COSMIC-2 design are the actively steered, multi-beam, high gain phased antenna arrays capable of receiving the radio occultation soundings from space. The amount of science the COSMIC-2 can deliver is dependent on the custom antenna arrays. Traditionally, only large projects could afford custom antennas. COSMIC-2 was a medium size project that required 30 antennas so minimizing manufacturing costs and assembly time was essential.
A standard antenna array support design is traditionally machined out of astroquartz, an advanced composite material certified for outer space. The team knew building custom antenna arrays out of astroquartz would be time consuming and expensive because of overall manufacturing process costs (vacuum forming over a custom mold) and lack of adjustability (copper sheets are permanently glued between layers of astroquartz). The custom antenna design also contained complex geometries that would be difficult to machine and require multiple manufacturing, assembly and secondary operations, causing launch delays. JPL decided to turn to additive manufacturing technology to prototype and produce the antenna arrays.
The manufacturing chosen to build accurate, lightweight parts while maintaining the strength and load requirements for launch conditions was Fused Deposition Modeling (FDM). FDM could produce this complete structure as a single, ready-for-assembly piece. This would enable quick production of several prototypes for functional testing and the flight models for final spacecraft integration all at a low cost. FDM can also build in ULTEM 9085, a high strength engineering-grade thermoplastic, which has excellent radio frequency and structural properties, high temperature and chemical resistance and could be qualified for spaceflight.
Instead of purchasing an FDM printer to produce the parts internally, JPL turned to Stratasys Direct Manufacturing for its large FDM capacity and project engineers who have experience with the aerospace industry and its requirements.
The antenna array support structures were optimized and patented for the FDM process. All shapes were designed with an “overhead angle” of 45 degrees at most to avoid using break-away ULTEM support material during the build. “Designing the antennas with self-supporting angles helped with two things,” said Trevor Stolhanske, aerospace and defense project engineer at Stratasys Direct Manufacturing, “it reduced machine run time so that parts printed faster, and reduced the risk of breaking any parts during manual support removal.” JPL was also able to combine multiple components into one part, which minimized technician assembly and dimensions verification time and costs.
Although FDM ULTEM 9085 has been tested for in-flight components, it had never been used on the exterior of an aircraft, let alone in space. Therefore, in addition to standard functional testing (i.e. antenna beam pattern, efficiency, and impedance match), FDM ULTEM 9085 and the parts had to go through further testing in order to meet NASA class B/B1 flight hardware requirements. Some of these tests included:
- Susceptibility to UV radiation
- Susceptibility to atomic oxygen
- Outgassing (CVCM index was measured to be 0 percent)
- Thermal properties tests – in particular, compatibility with aluminum panels. (Aluminum has a slightly different coefficient of thermal expansion than non-glass-filled ULTEM)
- Vibration / Acoustic loads standard to the launch rocket
- Compatibility with S13G white paint and associated primer
Stratasys Direct produced 30 antenna array structures for form, fit and function testing. Throughout each design revision, Stratasys Direct's project engineering team worked closely with JPL to process their STL files to ensure the parts met exact tolerances and to minimize secondary operations. Stratasys Direct's finishing department deburred the parts where needed, stamped each with an identification number and included a material test coupon. They also reamed holes for fasteners that attach to the aluminum honeycomb panel and the small channels throughout the cones to the precise conducting wire diameter.
“Not only did NASA JPL save time and money by producing these antenna arrays with FDM, they validated the technology and material for the exterior of a spacecraft, paving the way for future flight projects” said Joel Smith, strategic account manager for aerospace and defense at Stratasys Direct. “This is a great example of an innovative organization pushing 3D printing to the next level and changing the way things are designed.”
As of 2014, the COSMIC-2 radio occultation antennas and FDM ULTEM 9085 are at NASA Technology Readiness Level 6 (TRL-6). Stratasys Direct Manufacturing was able to successfully enter the JPL Approved Supplier List and delivered 30 complete antennas for final testing and integration. The launch of the initial six satellites is scheduled for 2016. Another constellation will launch in 2018. The FORMOSAT-7/COSMIC-2 mission will operate exterior, functional 3D printed parts in space for the first time in history.
* Turbiner, D. “Phased Array Antenna For GNSS Signals”, CIT-6243, USPTO US 20130342397 A1 https://www.google.com/patents/US20130342397?dq=Turbiner&hl=en&sa=X&ei=3pc9VJDKAYWHyATy1IDgBQ&ved=0CB0Q6AEwAA
NASA Mars Rover
NASA’s 2004 mission to Mars deployed two golf cart sized rovers equipped with cameras and scientific instruments for viewing and analyzing the surface. Mission scientists need a fail-safe way to plan the movements of the rovers, ensure successful operation, and maximize knowledge gained. NASA scientists chose professional computer graphics technology from NVIDIA Corporation to meet this need.
NASA is using NVIDIA Quadro® graphics solutions to reconstruct Martian terrain from transmitted rover data in photorealistic virtual reality, allowing scientists to explore Mars in 3D as if they were actually moving freely on the planet’s surface. This NVIDIA-powered environment serves as a precise visualization and planning system for NASA scientists, allowing them to rehearse a variety of Mars rover scenarios, mapping out moves and experiments by "flying" through highly realistic 3D reconstructions of the Martian surface, prior to directing the vehicle to undertake actual tasks.
Dealing with Martian Data
Over the next three months, NASA will receive terabytes of data from two Mars rovers. The first rover, named Spirit, successfully landed in the Gusev Crater on January 4, 2004, three weeks ahead of the touch-down date for the second rover. The Gusev Crater was selected because it appears to have been eroded long ago by flowing water.
Spirit sends data to Earth generated from two pairs of hazard-identification cameras mounted below the deck at the front and rear of the rover and from two other camera pairs that sit high on the mast rising from the deck. These cameras include a high-resolution panoramic camera and a pair of lower resolution cameras for navigation.
The cameras provide the views needed to navigate the rovers and collect scientific data about geological and weather conditions. Rover panoramic cameras send digitally massive high-resolution 360-degree panoramas of the surface as 1024x1024x16-bit images. A rover transmission may include hundreds of images.
3D Maps for Roving
NVIDIA Quadro graphics help scientists determine rover activities without having to sift through massive amounts of photographic data. NASA scientists use NVIDIA graphics to visualize high-resolution photographic imagery more than three times as detailed as images sent from the Sojourner rover in 1997. Because the new rovers travel six to ten times farther than Sojourner, taking approximately 6,000 to 10,000 more measurements per foot, the data visualized with NVIDIA graphics is transformed into a particularly detailed, visually enhanced, 3D representation of the planet’s terrain.
Laurence Edwards, Ph.D., Mars team lead for 3D visualization and surface reconstruction at NASA Ames Research Center explains, "NVIDIA technology allows NASA to visualize the Martian terrain in photorealistic virtual reality, greatly enhancing scientists’ understanding of the environment and streamlining analysis. With this capability, scientists step into a visually engaging model of the planet’s surface and interactively study multiple perspectives—front, back, side views—of every object the rovers investigate to fully explore all options for rover routes and experiments."
"With NVIDIA Quadro graphics driving Viz, the virtual reality software we use for Mars missions, we can also model the lighting and surface conditions expected to be present on Mars when an experiment will be conducted," said Edwards. "If a rock will cast a shadow, obscuring a feature of interest, scientists on the ground will know about this effect in advance and be able to plan around it. These NVIDIA-enabled capabilities allow NASA scientists to conceptualize a variety of scenarios and map out rover moves and activities prior to directing the rover to undertake actual tasks."
Advanced Visualization in PC Workstations
Most scientists spend their time looking at terrain models using typical NASA science operations workstations armed with NVIDIA Quadro FX 2000 graphics. According to Edwards, "This NVIDIA-powered solution handles a good-sized portion of the overall terrain model and makes data access extremely cost-effective. For the highest resolution, 3D terrain models with wide 360-degree views of the surface, we use NVIDIA Quadro FX 3000s. We also plan to cluster a number of PC workstations armed with NVIDIA Quadro FX 3000Gs. Such a system will surpass the power of expensive supercomputers and bring high-end visualization to a larger number of scientists."
According to Jeff Brown, general manager of workstation product management at NVIDIA, NASA migrated Viz from supercomputer to PC-based workstations powered by NVIDIA Quadro graphics for reasons such as:
A previous-generation NVIDIA Quadro graphics board in a PC workstation displayed images 33% faster than the expensive, proprietary incumbent system.
- Superior Shadowing:
Allows Viz to optimally handle real-time, interactive shadow simulation to predict sun/shade situations for experiments affected by light levels.
The ability to link multiple NVIDIA Quadro FX 3000G solutions allows Viz to run at or better than supercomputer performance levels at about one-tenth the cost.
- Greater Application Accessibility:
The full range of NVIDIA professional graphics solutions, from the entry-level NVIDIA Quadro FX 500 to the high-end NVIDIA Quadro FX 3000G, available in industry-standard PC workstations, makes NASA’s Viz virtual reality software accessible from virtually any desktop.
The NASA Ames 3D Visualization and Surface Reconstruction team constantly evaluates graphics technology. They are committed to keeping Viz on the leading edge and to ensuring that the scientific and communication requirements of upcoming missions are met. "We continually investigate advanced concepts for rover operator interfaces and science operations interfaces," says Edwards. "Our group is charged with bringing the latest technologies to the user interface portion of missions, and NVIDIA gives us several opportunities for future enhancements. We plan to demonstrate a large, wrap-around user interface using a cluster of NVIDIA Quadro FX 3000G graphics solutions to immerse scientists in a computer-generated display of the planet’s surface. We can see a point in the future where researchers would sit in such a display and program rover movements and experiments using simple touch-screen or voice commands."
By converting the data collected from cameras and scientific instruments on the rovers into knowledge through visualization, NVIDIA graphics technology helps NASA share the knowledge gained from Mars rover missions with the world. Scientists worldwide can access and study the largest and most topographically accurate 3D models ever constructed during remote space exploration. With the routine posting of NVIDIA-generated images on the Web, the public can also virtually participate in NASA’s search for life on Mars.
For more information about NVIDIA Quadro solutions, please visit: http://www.nvidia.co.uk/quadro
For more information about NASA’s Mars rover project, please visit: http://marsrovers.jpl.nasa.gov/home/index.html