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NASA Will Roll Back Its SLS Rocket for Repairs

NASA Will Roll Back Its SLS Rocket for Repairs

NASA engineers hope to have their massive moon-bound Space Launch System ready for liftoff in a couple of months, but so far they’ve encountered some bumps in the road. On March 17, NASA rolled the world’s most powerful rocket out onto the launchpad at Kennedy Space Center in Florida to ready it for the Artemis program’s inaugural lunar mission later this year. Since then, technicians have completed a raft of checks on the huge rocket’s systems, but after three tries they haven’t been able to make it through the final test, a practice countdown called the “wet dress rehearsal test.”

The key problems have been a faulty helium check valve and a liquid hydrogen leak, which led to several pushbacks of the test countdown. Finally, NASA officials decided over the weekend to disconnect the rocket and, starting next Tuesday, carefully roll the SLS and Orion crew capsule back to the Vehicle Assembly Building, a facility with the equipment needed for them to perform rocket surgery. They hope to have a quick turnaround, returning to the pad soon afterward to complete the countdown test, but the first Artemis mission around the moon—originally planned for early June—might be delayed.

“The mega moon rocket is still doing very well. The one check valve is literally the only real issue we’ve seen so far. We’re very proud of the rocket,” said Tom Whitmeyer, a deputy associate administrator at NASA headquarters in Washington, at a press conference this afternoon. “But we have a little bit more work in front of us.”

The precautions aren’t surprising; NASA doesn’t want to take a chance on its most expensive rocket or debut Artemis launch failing. “It comes down to what we consider to be the acceptable level of risk,” said Mike Sarafin, the Artemis mission manager, at an earlier press conference on April 15.

The test itself began on April 1, after the rocket had been ferried from the assembly building to Launch Complex 39B via an enormous crawler. Jeff Spaulding, the senior NASA test director, and his team began their process by hooking up the rocket’s electrical power and pressurization systems and filling the pair of white boosters on the side with propellants. Then they started loading the big orange fuel tank with more than 700,000 gallons of liquid hydrogen and liquid oxygen, supercooled to a frigid -423 and -297 degrees Fahrenheit, respectively. (That’s the “wet” in “wet dress rehearsal test.”) Their goal was to simulate the entire countdown process to just under T-10 seconds—the closest thing to a real launch without firing up the core stage’s RS-25 engines.

Throughout the test, Spaulding and his colleagues monitored instruments, pressures, temperatures, and valves to check that all the systems were working within acceptable parameters. (“If it turns out they’re a little outside of the limits, that’s what we want to know now—if there’s something we need to fix or adjust,” he had said in the days leading up to the rehearsal.)

The test revealed the need for several adjustments. The process was delayed the first time on April 2 by lightning bolts, which hit the towers around the rocket. Then the following day, NASA officials encountered problems with launch tower fans and their backups, according to Charlie Blackwell-Thompson, the Artemis launch director. These fans provide pressure in the mobile launcher, the tall structure next to the rocket, to keep out hazardous gasses. That led to a delay while the fan malfunction was resolved.

4 Years On, a New Experiment Sees No Sign of ‘Cosmic Dawn’

4 Years On, a New Experiment Sees No Sign of ‘Cosmic Dawn’

When hydrogen atoms first formed, they absorbed and then emitted ambient 21-centimeter radiation at equal rates, which made the clouds of hydrogen that filled the primordial universe effectively invisible.

Then came cosmic dawn. Ultraviolet radiation from the first stars excited atomic transitions that enabled hydrogen atoms to absorb more 21-centimeter waves than they emitted. Viewed from Earth, this excess absorption would appear as a drop in brightness at a specific radio wavelength marking the moment the stars turned on.

In time, the first stars collapsed into black holes. The hot gases swirling around these black holes generated x-rays that heated hydrogen clouds throughout the universe, increasing the rate of 21-centimeter emissions. We would observe this as an uptick in brightness at a slightly shorter radio wavelength than that of the older light. The net result would be a dip in brightness over a narrow radio wavelength range, like the one detected by EDGES.

But the observed dip, which occurred around a wavelength of 4 meters, was not what theoretical cosmologists had expected: The timing and shape of the trough were off, indicating that the first stars turned on surprisingly early, and that x-rays flooded the universe soon afterward. Stranger still, the dip was very pronounced, suggesting that hydrogen in the early universe was colder than theoretical models predicted, possibly because of exotic interactions with the dark matter that fills the cosmos.

Or perhaps the EDGES dip had a more mundane origin.

Hydrogen’s 21-centimeter emissions from the cosmic dawn era reach Earth with wavelengths of several meters, in the range used for FM radio and television broadcasts; that’s why EDGES operated in such a remote location. What’s more, the signal is overwhelmed by radio emissions thousands of times brighter from our own galaxy, and it’s distorted by its passage through the upper layers of the Earth’s atmosphere.

No less important are subtle effects from the antenna itself. A radio antenna’s environment can slightly change the area of the night sky to which it is sensitive. In such a precise experiment, even faint reflections off surfaces tens of meters away can matter. The effect of such reflections would be enhanced at certain radio wavelengths, resulting in a small variation in the antenna’s observing area—and thus potentially in the measured brightness—at different wavelengths.

The EDGES team did see this kind of ripple in their data, and the prime culprits, perhaps fittingly, were the edges of a 30-meter-wide metal screen placed on the ground surrounding the antenna to block radio emissions from the ground itself. The team corrected for possible reflections off of these edges in their analysis, but as some astronomers noted at the time, if the correction was even slightly off, the result could be a dip in background brightness over a narrow wavelength range indistinguishable from a real cosmic dawn signal.

The SARAS team took a different approach to antenna design in pursuit of more uniform sensitivity across all wavelengths. “The entire design philosophy is to preserve that spectral smoothness,” said Saurabh Singh, the lead author on the SARAS paper. The antenna—an aluminum cone propped on a Styrofoam raft—was floated in the middle of a placid lake to ensure there would be no reflections for more than 100 meters in any horizontal direction, which Parsons called “a really cool and innovative approach.” Moreover, the slow speed of light in water reduced the effect of reflections from the lake bottom, and the uniform density of the water made the environment much easier to model.

Earth’s Oceanography Helps Demystify Jupiter’s Flowing Cyclones

Earth’s Oceanography Helps Demystify Jupiter’s Flowing Cyclones

Lia Siegelman had just been studying the swirling waters of the Southern Ocean, which surrounds Antarctica, when she happened to come across a poster image of cyclones around Jupiter’s north pole, taken by NASA’s Juno spacecraft. “I looked at it, and I was just struck: ‘Whoa, this looks just like turbulence in the ocean,’” she says.

So Siegelman, a researcher at UC San Diego’s Scripps Institution of Oceanography, turned her eye to the latest detailed images of the outer planet. She and her team proved for the first time that a kind of convection seen on Earth explains the physical forces and energy sources that create cyclones on Jupiter. (Since air and water are both “fluids,” from a physics perspective, the same principles apply to the gas giant’s atmosphere and our oceans.) They published their findings today in the journal Nature Physics.

Jupiter, the 4-octillion-pound elephant in our solar system, makes gigantic cyclones, big storms that rotate around areas of low pressure. Some are thousands of miles wide—as large as the continental United States—with gusts of wind up to 250 miles per hour. Eight of the largest have been spotted at the planet’s north pole and five at the southern one. Scientists have speculated for years about their origins, but by mapping out these storms and measuring their wind speeds and temperatures, Siegelman and her colleagues showed how they actually form. Little spinning vortices pop up here and there among the turbulent clouds—not so different from the ocean eddies Siegelman’s familiar with—and then they start merging with each other. The cyclones grow by continually gobbling up smaller clouds and gaining energy from them, so that they keep on spinning, she says.

It’s a clever way to study extreme weather on a planet that’s more than 500 million miles away. “The authors are clearly drawing from meteorology and oceanography disciplines. These folks are taking this rich literature and applying it in sophisticated ways to a planet we can barely touch,” says Morgan O’Neill, a Stanford atmospheric scientist who models the physics of hurricanes and tornadoes on Earth and has applied her work to Saturn.

In particular, O’Neill says, the team of scientists demonstrate how, like thunderstorms on Earth, Jupiter’s cyclones build up through a process with a gross-sounding name: “moist convection.” Warm, less-dense air, deep down in the planet’s atmosphere, gradually rises, while cooler and denser air, near the frigid vacuum of space, drifts down. This creates turbulence, which can be seen in Jupiter’s swirling, moisture-packed clouds of ammonia.

Juno cyclones
Photograph: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM
Second Time’s the Charm: NASA Perseverance Drills a Mars Rock

Second Time’s the Charm: NASA Perseverance Drills a Mars Rock

As the Perseverance rover drilled into a rock on Wednesday to collect a sample from Jezero Crater on Mars, Justin Simon, a planetary scientist at NASA’s Johnson Space Center in Houston, felt both nervous and excited. He has the honor of serving as the “sample shepherd,” leading the effort from millions of miles away, but the pressure’s on. “These samples not only will allow us to understand the geology of the crater but also minerals likely related to the history of water there,” he said yesterday.

But first, the rover had to actually capture a chunk of rock in a test-tube-sized container. An initial attempt in early August had come up empty. That first rock, nicknamed “Roubion,” simply crumbled to dust as the drill bored into it, and none of those bits made it into the container.

Simon can now breathe a sigh of relief. Perseverance’s second try, with a different rock, appears to have successfully extracted a Martian core slightly thicker than a pencil.

“We got that image of just a spectacular-looking core, a fantastic-looking cylinder, broken off cleanly. It looks geologically very interesting, something scientists of the future will enjoy working on,” says Ken Farley, a Caltech geochemist and project scientist of the Perseverance mission, which is led by NASA’s Jet Propulsion Laboratory in Pasadena, California.

But the analysis of the new sample is going to take awhile, because NASA scientists haven’t been able to get clear photographs due to low lighting conditions, which makes the images tough to interpret. To add more drama for the scientists, when Perseverance did a “percuss-to-ingest” procedure—shaking the sample to make sure the tube wasn’t overfilled, which would make the system jam when it’s stored—one image appeared to show an empty sample tube. (They’re pretty sure they got the sample, but they’re going to try taking more images in better light over the next couple of days.)

Perseverance’s first drill attempt, which essentially pulverized the sample, wasn’t a complete failure, as it yielded evidence suggesting the rock had been weathered, worn down by a river flowing into the lake crater billions of years ago. “It always had been possible that this lake was a transient event, like maybe a comet, rich in water, hit Mars and made lakes, and then it boiled away or froze within tens of years. But that would not produce the weathering we see,” said Farley in an interview earlier this week.

Since that rock was too powdery, the scientists then piloted the rover to a new area, looking for a different kind of rock to sample, using the Ingenuity copter to scout ahead. Perseverance trundled slightly to the west, where on a ridgeline the researchers found a larger, boulder-like rock, which they nicknamed “Rochette” and which seemed less likely to disintegrate when the rover deployed its tools on it. “It looks like a rock that, if you could throw it, would clank down on the ground. A good, healthy rock,” Farley said.

Before each sampling attempt, Perseverance performs reconnaissance by snapping a bunch of photos of a candidate rock. Last weekend, it also performed an abrasion test to see if Rochette was durable enough to sample. The rover is equipped with a rotary percussive drill (with extra drill bits) that both spins and hammers into the rock. This tool helps clear away dust and chip through the weathered outer layer. The abrasion was spectacularly successful, according to Farley, so the scientists decided to go ahead with grabbing a sample. Perseverance extended its 7-foot-long robotic arm, fired up the drill, and carefully extracted a core sample. Then it rotated the arm’s “hand” so that the sample tube could be inspected.

Why Perseverance’s First Mars Drilling Attempt Came Up Empty

Why Perseverance’s First Mars Drilling Attempt Came Up Empty

Last week, NASA’s Perseverance rover shot for a new milestone in the search for extraterrestrial life: Drilling into Mars to extract a plug of rock, which will eventually get fired back to Earth for scientists to study. Data sent to NASA scientists early on August 6 indicated a victory—the robot had indeed drilled into the Red Planet, and a photo even showed a dust pile around the borehole.

“What followed later in the morning was a rollercoaster of emotions,” wrote Louise Jandura, chief engineer for sampling and caching at NASA’s Jet Propulsion Laboratory, in a blog post yesterday describing the attempt. While data indicated that Perseverance had transferred a sample tube into its belly for storage, that tube was in fact empty. “It took a few minutes for this reality to sink in but the team quickly transitioned to investigation mode,” Jandura wrote. “It is what we do. It is the basis of science and engineering.”

By now, the team has a few indications of what went wrong in what Katie Stack Morgan, deputy project scientist of the Mars 2020 mission, calls “the case of the missing core.”

“We’ve successfully demonstrated the sample caching process, yet we have a tube with no core in it,” she says. “How could it be possible that we have carried out all of these steps perfectly and successfully, yet there is no rock—and no anything—in the tube?”

One theory, of course, was that the rover had simply dropped the core sample. But there were no broken pieces on the surface. Also, Stack Morgan says, the tube was “very clean, not even dusty, suggesting that there was perhaps nothing that had ever gotten into the tube.”

NASA scientists now think that the core was actually pulverized in the drilling process, then scattered around the borehole. “That would explain why we don’t see any pieces in the hole and why we don’t see any pieces on the ground, because they have basically become part of the cutting,” says Stack Morgan. “So we started to think about why that happened, because that is not a behavior that the engineers saw in the very extensive test set of rocks that they cored prior to launch.”

Perseverance is drilling in Jezero Crater, which used to cradle a lake, and therefore may have been home to ancient microbial life. (It’s been relying on the Mars helicopter, Ingenuity, to scout ahead for spots to dig.) By digging into the rock instead of just sampling dust at the surface, the rover will provide vital clues about the geological history of the planet. The Curiosity rover, which landed on Mars in 2012, also drilled, but it was designed to grind the rock instead of extracting cores. This time, NASA engineers want samples that let them observe the rock as it was laid down so they can analyze it for hallmarks of life—some microbes, for instance, leave behind characteristic minerals.

For Perseverance, the drilling process actually begins inside the rover, in a section called the adaptive caching assembly. Here, a robotic arm takes a tube out of storage and inserts it into the “bit carousel,” a storage container for all of Perseverance’s coring bits. The carousel then rotates, presenting the tube—which is about the same shape and size as a laboratory test tube—to the 7-foot-long arm that’ll actually do the drilling. “We pick up that coring bit, and that has the tube inside,” said Jessica Samuels, surface mission manager for Perseverance, in an interview before the first drilling attempt. “And now at that time we’re ready to actually acquire the sample.”