Surprise delay forces engineers to design and build a part in 24-hours.
Next month, the first US asteroid sample return mission, OSIRIS-REx, lands in the Utah desert. In preparation for this first of its kind mission, NASA has been conducting critical rehearsals to secure, transport and analyze the samples upon return. However, an unexpected part delay put one of these rehearsals at risk.
The story of OSIRIS-Rex so far.
Engineering teams at NASA’s Johnson Space Center are a crucial part of the rehearsal process. They have been rapidly designing, simulating, prototyping and manufacturing all the tools needed to successfully handle the asteroid samples upon return. Just before a June rehearsal, the team got word that a manufacturer would not have a critical component made in time. With just 24 hours to create the part themselves, the team sprang into action. Their simulations and advanced testing were key to creating a rehearsal-ready version of the part.
The OSIRIS-REx Mission and Ensuring Sample Safety
The Origins, Spectral Interpretation, Resource Identification, Security – Regolith Explorer (OSIRIS-REx) spacecraft is on a long voyage home to bring back asteroid samples. Launched in 2016, it reached its target asteroid, Bennu, in 2018. After captured a large number of samples in 2020, it soon after began its journey to Earth.
“When it came to OSIRIS-REx and the complexity and sophistication of the sampling mechanism, the TAGSAM, it was something that hadn’t been seen before at this scale,” Salvador Martinez, lead technology development engineer at Johnson Space Center, told engineering.com.
As of July 26, NASA reported in a blog that the spacecraft was 24 million miles (38.6 million kilometers) away, and traveling at about 22,000 miles per hour toward Earth. The craft will cover those millions of miles over the next few weeks, finally landing its samples in the Utah desert on September 24, 2023. Upon landing, the exploration part of the mission is complete, but the science is just beginning.
The safe retrieval, transportation, processing, division and analysis of the sample is a complex engineering challenge in and of itself. The material choices for retrieval tools are heavily restricted and interaction with the sample is limited to avoid any contamination of the extraterrestrial rocks and dust. These samples provide a look back to billions of years ago, just as the Sun and planets were forming. Ensuring a pristine environment for these samples is crucial to getting an accurate window into the past.
“It is one more step in being able to piece together how our system formed and evolved,” said Eileen Stansbery, chief scientist at Johnson Space Center, at a NASA media event.
Ensuring Sample Safety Requires Engineering and Rehearsals
Conducting a new type of scientific study at this scale required engineers to create new tools and processes. NASA dedicated an internal engineering team to the OSIRIS-REx mission to take on this challenge.
Led by Martinez, the team oversees creation of the containment structures and tools needed to process all the samples upon their return to Earth. From rigs to change the orientation of the sample containers, to devices that can evenly divide the rocks into sample trays, there were many designs to create in a short time.
“There is a need for disassembling this TAGSAM [in a glove box] in a way that keeps the sample pristine,” Martinez said. “I think it’d be challenging to do this disassembly even on the table, much less wearing gloves and wearing a cleanroom suit. This is something that has never been tried before, so there’s a lot of trial and error, and a lot of rehearsing.”
The 24-Hour Challenge
As the date of one of the major rehearsals approached, the engineering team was working hard to get all the glove boxes and tools ready. In the midst of final preparations, they received news from a manufacturer.
“One of the components that we had sent out to be machined was not going to arrive in time,” Martinez said. “This happens to you sometimes. You send things out and you know with schedules and delays and shortages, there’s so many compounding factors throughout this entire process.”
They learned of the delay on a Monday. Rehearsal was Thursday morning, and the part had to go through several sterilizations, assembly and transportation steps before it could be used. In short, the engineering team was on a tight schedule.
“We were still working on getting all the other equipment in and we knew then we had a really short timeframe to even think of a solution for a stand-in,” Martinez said. “We just started going to the drawing board.”
The part in question was a critical baffle used to disperse the sample into dedicated containers upon its removal from the TAGSAM. The rehearsal used this part heavily to test out the hardware and how it’s used to disassemble the container and disperse the rocks.
“That was one of the components we closely analyzed and rehearsed over and over again,” Martinez said. “No matter how you pour the sample off of this TAGSAM, it actually funnels directly into these trays underneath. It’s got very complex edges and contouring.”
This was one of the most difficult to manufacture components of their design. The team had done several analyses and simulations in advance to ensure it was strong enough, while also light enough to manipulate with gloves inside of a box.
Recreating the Baffle
To originally design the part, the engineers had started with hand calculations, went to strength of material calculations and free body diagrams, and then brought in linear static analysis to look at deformations and stresses. The group primarily used PTC Creo simulation software for their FEA linear static analysis.
Martinez says that they simulated the use of different material options and eliminated most as options for the design. Although their final product’s material selection was limited to a few options, they also analyzed their design’s strength when created from other prototyping materials. This ensured the prototypes accurately reflected the properties of their final design.
This knowledge came in handy when working to deliver a stand-in baffle in 24 hours. While the rehearsal piece didn’t have to exactly match the final product design, they wanted to get as close as possible. Luckily, working quick and prototyping fast is something the engineering team is used to.
“The way that we had tried to develop the hardware was we iterated, and we provided solutions. As soon as we get it into the end users’ hands, we can analyze the operations and try and identify if there are any changes needed and we need to iterate again,” Martinez said.
After considering their past design work and testing, balanced with the speed at which they had to deliver their creation, they settled on their primary manufacturing technique.
“We looked at what was available to be waterjet cut because that was going to be quick,” Martinez said. “[It was] too big to waterjet it out of one piece. We had to waterjet it in two halves and make a bracket that connects both halves, two sides, and then we have to rivet them together. On top of that, how do we attach it to what’s going to be the circular boundary on the outside?”
The group started experimenting with bending sheet metal and adding rivets to get close to the performance of the final design without adding too much material, just like they had simulated during the design process.
“We reached the point which was about as good of an approximation as we could provide [in] a little over 24 hours from us beginning to go into the whiteboard and saying, ‘How do we do this?’” Martinez said.
The stand-in baffle was delivered on time to be sterilized and assembled in the glove boxes for the rehearsal. It featured prominently in NASA’s photographs and the video taken of the test run.
“I was pleasantly surprised after seeing it cleaned,” Martinez said. “It does not look like it was made in a day.”
Operators were able to lift and maneuver the part and test the pouring of varying sized teflon balls into the baffle which dispersed into sample containers. The balls simulated the rock and dust that will be dumped into the baffle during the actual return.
Although this was just a rehearsal, the positive results reinforced the group’s approach to processing and portioning out the very precious samples of asteroid Bennu. As the asteroid samples continue to fly closer to Earth, the engineering team is continuing their work, ensuring the tools are perfected for landing day.