Keegan Barber/NASA
This was the moment Dante Lauretta had been waiting for nearly 20 years. A small robotic capsule was returning to Earth with a load of rocks scooped from an asteroid, and Lauretta was eager to get a sample.
Scientists led by Lauretta carefully designed a multibillion-dollar mission to bring back carbon-rich asteroid debris thought to contain organic molecules, the building blocks necessary for life to establish. The NASA mission, known by the acronym OSIRIS-REx, was launched from Earth in 2016 and will collect samples from a roughly 1,600-foot-wide (500-meter) asteroid named Bennu before returning to Earth in 2020. The course was set.
On September 24, the OSIRIS-REx spacecraft will eject a canister containing an asteroid sample for entry into Earth’s atmosphere, and the mothership will safely bring it back to deep space for a follow-up mission to explore another asteroid. We set course for the future. The end of the 2020s.
Lauretta, the Osiris-Rex principal investigator at the University of Arizona, was a passenger in a U.S. military helicopter circling the capsule’s landing zone in the Utah desert. The heat shield protected the capsule from temperatures that rose to more than 5,000 degrees Fahrenheit during atmospheric reentry.
Next, a small drogue parachute was to open to stabilize the 32-inch (81-centimeter) wide sample return vessel. After about five minutes, a larger main chute opens, slowing the capsule to a gentle landing while protecting the precious asteroid material sealed inside.
At least, that was the plan. While Osiris-Rex successfully brought the asteroid sample back to Earth, there was a moment of great drama.
out of order
For those watching NASA’s live video of the OSIRIS-REx mission’s return to Earth, there was a hint that something was wrong. Video images from a NASA tracking plane showed the capsule tumbling toward the ground at high speed, well past the point where the drogue’s parachute was supposed to be visible.
In a nearby helicopter, Lauretta awaited a verbal update on the capsule’s status.
“I “I heard that we crossed 100,000 feet and there were no drogues. The drogue chute was supposed to come out at 100,000 feet,” he recalled in a presentation to the National Academies Committee on Space Studies last month. I’m like, “Hmm, this isn’t good.” ”
The last time NASA tried to bring an extraterrestrial sample back to Earth, the parachute didn’t open. The robotic Genesis mission ended in an uncontrolled impact in Utah, rupturing the capsule and bringing back particles collected from the solar wind. Scientists were able to recover some of the specimens, but it wasn’t easy.
Lauretta called a crash like the one experienced by NASA’s Genesis mission a “worst-case scenario” for Osiris-Rex. In that case, scientists will need to quickly collect as many asteroid samples as possible from the Utah desert. Anything recovered must be carefully inspected for contamination by Earth’s soil or life forms.
You can watch a replay of OSIRIS-REx’s landing below.
“We’re falling. We’re in a subsonic regime and it’s not stable,” Lauretta said. “We don’t have drogue chutes deployed here. That’s a problem! So I’m on live TV and I’m like, “I’m trying to mentally prepare myself to get out of this helicopter and deal with a crashed capsule in the desert.” It was something.”
Later, Lauretta heard confirmation from the Air Force that the Osiris-Rex return capsule had deployed its main parachute.
“I was like, ‘What? How is that possible?'” he said. “So the main chute deployed. The drogue chute, which we were able to recover, advanced a second ahead of the main chute. So it came out. It had to come out. It was in front of the main parachute inside the canister. There seems to be a problem with the circuit.”
NASA on Tuesday provided a more detailed explanation of the problems that prevented Drogue Chute from deploying as planned.
The capsule sends an automatic signal to deploy the drogue chute at an altitude of 100,000 feet and starts a timer for approximately 5 minutes before cutting the drogue’s holding cord at the second signal and unfurling the large parachute. It was planned that the aircraft would be able to complete the landing sequence. Instead, a signal activated the system at 100,000 feet, detaching the drogue still inside the capsule, NASA said.
At 9,000 feet, the other signal actually sent the command to release the drogue chute. However, since the holding cord had already been severed, the drogue was quickly released from the capsule and the main parachute opened as expected.
“The first signal was to fire the mortar and release the drogue,” Lauretta said. “The second signal was supposed to cut the cable to free the main pipe…It appears that the first signal cut (the cable) and then the second signal fired a mortar, so it retreated. But… “It went well. We did a lot.” “There was plenty of room in the main chute. We landed safely. It was a beautiful pinpoint landing in the Utah desert.”
An investigation by engineers from NASA and Lockheed Martin, which built the OSIRIS-REx spacecraft and sample return vehicle, found that the mission’s construction plan was not specific enough in directing engineers to assemble the return capsule. did.
“In the design plans for the system, the word ‘main’ was used inconsistently between the device transmitting the electrical signals and the device receiving the signals,” NASA said in a statement. “On the signal side, ‘main’ meant the main parachute. By contrast, on the receiver side, ‘main’ referred to the fireworks ignited to release the cover of the parachute canister and deploy the drogue.” It was used as a thing.
“Engineers connected the two mains, which caused the parachute to deploy out of order,” NASA said in a statement.
Lauretta said scientists are continuing to analyze asteroid material delivered by OSIRIS-REx.
In preliminary analysis of some of the dust, scientists found about 5 percent carbon by mass, and the material was found to be rich in water in the form of hydrated clay minerals. It is very plausible that asteroids like Bennu billions of years ago provided much of the water that is now in Earth’s oceans, lakes, and rivers.
A team tasked with retrieving samples from the capsule at NASA’s Johnson Space Center in Houston encountered problems opening some of the clasps sealing the asteroid material inside the main collection chamber. While the research team was working on a new plan to collect all the asteroid specimens stored inside, they were unable to find large pieces, including one about 1.2 inches (3 centimeters) long, taken directly from Bennu using tweezers. I took out some.
“Organic chemistry looks great,” Lauretta said.