NASA’s ICESat-2 to carry never before used 3D printed part

The 3D printed part, a black bracket holding the instrument’s fiber-optic cables, is visible in the back of the ATLAS instrument. Credit: NASA

Inside the Goddard Space Flight Center in Greenbelt, Maryland, NASA’s engineers have designed a 3D printed part for its Ice, Cloud, and land Elevation Satellite-2 (ICESat-2). Slated for launch in 2018, the satellite instrument will include a 3D printed bracket made of polyetherketoneketone (PEKK), a material that has never been used in additive manufacturing or spaceflight. The bracket will support the instrument’s fiber-optic cables.

“This is a first for this material,” said Craig Auletti, lead production engineer on ICESat-2’s only instrument, the Advanced Topographic Laser Altimeter System (ATLAS).

In fact, the PEKK bracket is said to be only the second 3D printed part to be flown in a spaceflight instruments, according to Oren Sheinman, the ATLAS mechanical systems engineer NASA Goddard.

The developers chose PEKK because it’s electrostatically dissipative and strong. The material also produces minimal outgassing, a chemical process similar to what happens when plastics and other materials release gas. In a vacuum or under heated conditions, these outgassed contaminants can condense on and harm optical devices and thermal radiators, significantly degrading instrument performance.

Additive manufacturing is fast and a low-cost alternative to traditional manufacturing methods.

“Had we manufactured this part classically, it would have taken six to eight weeks. We got it in two days,” Sheinman said, adding that costs to the project were up to four times less than with a traditionally machined part.

NASA engineers were able to quickly and efficiently print the bracket. The process included a computer-operated device, which prints a solid object, layer by layer, using a high-power optic laser that melts and fuses powdered materials in precise locations using a 3D CAD model.

The ATLAS instrument inside a Goddard cleanroom where the instrument was assembled. Credit: NASA/D. McCallum

The ATLAS instrument inside a Goddard cleanroom where the instrument was assembled. Credit: NASA/D. McCallumThe 3D printed bracket is not the only unique aspect of the mission. ICESat-2 is designed to measure changes in ice-sheet elevations in Greenland and the Antarctic, sea-ice thicknesses, and global vegetation. However, it will execute its mission using a never-before-flown technique. It will be NASA’s first space-borne, photon-counting laser altimeter, a new precise method for measuring surface elevations.

ICESat-2 is able to measure changes in the elevation of an ice sheet, something previous missions have struggle with, by splitting the green-light laser into six beams, arranged in three pairs, firing continuously at a rapid 10,000 pulses per second toward Earth.

This technique is called photon counting, and not yet been used for altimetry in a spaceflight instrument. It more precisely records the time-of-flight of individual photons as they travel from the instrument, reflect off Earth’s surface, and then are detected as they return to the instrument’s detectors.

“It’s almost completely built,” ATLAS Instrument Scientist Tony Martino said, adding that the spacecraft will fly on the last Delta II launch vehicle. “All functional parts are there and our first comprehensive testing starts in February. We’re on track.”
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