IR Labs applied decades of experience in IR astronomy to meet NASA’s requirements. Our engineering team worked closely with the NASA GSFC project team to design solutions for the unique specifications for the NFR. Following are some highlights of overcoming several design challenges.
Material Sourcing and Manufacturing Techniques For High Strength, Low Weight
We met size and weight requirements by using high strength, lightweight materials and advanced machining and production processes to reduce mass and number of components. All micro-vessel structural components are titanium for high strength and corrosion resistance. A286 steel alloy hardware and laser welding techniques were employed to fasten the assembly together. The Winston cones were produced using an additive electroforming process, where nickel is deposited over a mandrel form and then the mandrel is removed for final machining.
Unique Winston Cone Assembly Method
Each Winston cone observed the outside environment through a window port and had to maintain alignment with its associated detector element. We designed a method to hold the cone assembly in specific alignment to the housing, to the window port, and to concentrate light on the detector array. The lightweight, compact, and structurally rigid subassembly was engineered to withstand extreme pressure differentials while maintaining ease of assembly and testing.
Final Window Port Design Helps Meet Size and Weight Limits, Reduces Cost
The seven Winston cones and detectors observe the outside environment through a window port that must provide an unobstructed 5-degree field of view and transmit radiation over the 0.2-300 µm spectral range. Design of the window port is a key factor affecting overall size and weight of the instrument.
IR Labs worked with NASA GSFC to design iterations of window port concepts. One prototype used a single diamond window that could transmit the entire spectral range. Compared to previous designs, this concept reduced mass by almost 15% and provided substantial cost savings. The window was fabricated by chemical vapor deposition (CVD), was corrosion resistant, and met all operating temperature and pressure requirements.
Evaluation of the diamond window prototype led to concerns over the large difference in coefficient of thermal expansion between the diamond material and titanium micro-vessel. The concern was that differences in expansion over the wide temperature range would stress the window and risk fracture and loss of vacuum seal. Attempts to mitigate this risk using a molybdenum window seat were found to add too much mass and cost.
This led to a final design iteration that made it feasible to return to separate windows for each cone. Eliminating a folding mirror within the micro-vessel reduced the optical path length from window to cone, which reduced size, mass, and cost.
Micro-vessel Design for Benchwork and Mission
The micro-vessel needed to be accessible for researchers to assemble and disassemble during laboratory testing. The vacuum valve was designed for lab access using rubber O-rings and an actuator to evacuate the inside during bench work, then replaced with a permanent mechanical connection for missions. For access to the detector array and PCB, the exit port was designed with multiple rubber O-rings for lab work and will be replaced with metal-coated O-rings for missions.
Our work on the micro-vessel and optics for NASA’s NFR demonstrates IR Labs’ ability to solve unique challenges presented by scientific exploration and work in collaboration with our client. Many challenges were solved including selection of lightweight but durable materials and developing innovative Winston cone assembly methods. For NASA and other clients in the scientific community, IR Labs is known for its ability to solve design challenges with our engineering talent and manufacturing capabilities.