Yesterday, Northrup Grumman’s Cygnus spacecraft was launched from NASA’s Wallops Flight Facility, carrying supplies and scientific experiments to the International Space Station. Among the technologies aboard the spacecraft is Seeker, a new robotic free flier inspector. Seeker was produced through a collaboration between NASA and The Technology House (TTH), which leveraged Carbon’s 3D printing platform for the production of four high-performance thrusters for the Seeker’s cold-gas propulsion system.
Carbon’s 3D printing platform enabled the partners to reduce time to certification for the thrusters as well as production costs. More than that, the project saw Carbon’s technology and Cyanate Ester 221 material be validated by NASA as a production solution for new space-bound robotics such as Seeker.
As an external free flying robotic inspector, Seeker is a totally new type of robot consisting of a 3U CubeSat about the size of a loaf of bread. The robotic assembly launched yesterday aboard the Cygnus spacecraft is a demonstration project for autonomous robotic inspection that has been in development for the past year or so.
With such a tight timeframe, NASA had to find a way to rapidly manufacture highly optimized propulsion components to fulfil a series of rapid integrated system design cycles. An iterative design cycle approach enabled by Carbon’s platform allowed the space agency to develop, test and tweak the Seeker project with minimal delays.
A compact configuration
Seeker contains a cold-gas propulsion system made up of twelve 0.1N thrusters and a Guidance Navigation and Control system. The thrusters enable the robot to move around in orbit, while a wide field camera is used to navigate and a narrow field camera enables detailed inspection.
In such a small robot, the design and assembly was critical, especially in integrating the Guidance Navigation and Control system instrumentation with the rocket thrusters. For instance, one face of the vehicle (measuring just 10 x 10 x 10 cm) contains an Inertial Measurement Unite, a laser rangefinder, four sun sensors, two cameras, a communication antenna and four small rocket thrusters.
The main challenge in fitting all these components into such a small area was in developing an effective cold gas thruster system—with cold gas jets, gas tubing and fittings, integrated bracketing, and design accommodation for nearby sensors—that would be compact enough.
The solution? Carbon’s 3D printing technology.
Carbon to the rescue
Carbon’s platform proved to be suitable for producing small parts with the complex holes and passages needed for the cold-gas propulsion system. The technology also made it possible to iterate various design versions and test them. In total, NASA printed over 10 design iterations which led to the development of the final integrated component. The printed part also required no post-machining.
A critical part of the project’s success was the material used: Cyanate Ester (CE 221).
Before the Seeker project, no 3D printed pressurized plastic parts had ever been certified by NASA for ground and flight use around operators. Typically, new processes and materials used for such parts are subject to lengthy certification processes by NASA and are evaluated against stringent design and construction standards.
Considering this, there was some understandable doubt when a non-metallic material, CE 221, was first suggested. However, the potential benefits of the material led the NASA team to establish a development and qualification test schedule for understanding the capabilities of parts 3D printed from CE 221. As part of this process, the team reportedly pressurized over 100 parts to failure, improving structural design and sealing interfaces along the way.
In the development process, TTH realized there was still some variability in the 3D printed manifolds. These variations were subsequently addressed by TTH and NASA, and the parts were adapted to integrate design elements for improved accuracy and printability. Post-processing and cure times were also tuned by TTH to ensure the highest degree of repeatability. By making these modifications to the part and process, TTH was able to exert more control over Carbon’s AM process to achieve critical tolerances of the part’s small throat dimensions (0.026 inches).
“Other plastics used in additive manufacturing wouldn’t be able to hold up to everything you’re going to get through this whole process,” said Greg Cebular, Vice President of Sales at The Technology House. “It has to hold up to being pressurized, to the cold of space, to the heat from the sun…really it was the high-temperature Carbon CE 221 material that drove this. It was the whole reason that NASA was able to produce this on an additive technology.”
In the end, Carbon’s technology and CE 221 material were able to meet the stringent safety and performance requirements for the Seeker project. Impressively, the iterative platform enabled NASA to achieve the fastest timeline for one of its spacecraft while remaining cost-efficient.