April 5, 2019
Like a CT scan done in reverse, the light projections combine to form a 3D object that is suspended in the resin. Photo by Hossein Heidari/UC Berkeley
Lawrence Livermore and UC Berkeley researchers are using light to create 3D images in a single step.
Normal 3D printers work by building up thin layers of melted plastic to create solid objects, but it’s hard to get intricate designs to hold their form. But design engineers at Cal and Lawrence Livermore Lab thought about making 3D objects the same way a CT scan creates 3D images: by hitting a patient with X-rays from many different directions.
Instead they reversed the process to create objects rather than imaging them, except they do it with light instead of X-rays.
The process is called volumetric printing. Rotating images of an object are beamed through a conventional video projector. The light is focused on a slowly rotating cylinder of gooey resin containing plastic molecules with a light sensitive-activator.
One of the Apollo 16 sample boxes is opened in the Lunar Receiving Laboratory. The box contains a large rock and many small sample bags. Image courtesy of NASA/Johnson Space Center
Nearly 50 years ago, some very special materials were transported from outer space to Earth — unopened lunar treasures rocketed back by Apollo moonwalkers between 1971 and 1972.
Nine “special samples” were collected in containers during the Apollo 15, 16 and 17 missions that had indium knife-edge seals to maintain a lunar-like vacuum. Apollo mission planners devised these special sample containment systems to meticulously preserve fragile and transitory sample characteristics (e.g., solar wind volatiles, volatile coatings). Three of these “special” samples have remained sealed in their original Apollo containers until today.
Lawrence Livermore National Laboratory cosmochemists will analyze the Apollo 17 samples to study the geologic history of the site where the rocks were collected, a cold trap where water may have been able to freeze. This marks the first time such a sample will be studied in detail since the end of the Apollo program.
“Since the Apollo missions, science has advanced, so that the importance of volatiles on the moon has become increasingly recognized. Furthermore, the advance in analytical capability over the past 50 years will allow modern investigators to make measurements that were impossible during the Apollo missions,” said cosmochemist Lars Borg, who will head the LLNL team.
An artist's impression of a black hole passing in front of a star in the Andromeda Galaxy. Image courtesy or Kavli Institute/University of Tokyo
Dark matter is said to make up 80 percent of the universe’s matter, but scientists have had a heck of time figuring out what it actually is.
One contender making a comeback is primordial black holes (PBHs). These objects might have been born in the earliest age of the universe, back when the cosmos was nothing but a hot plasmatic soup — mostly radiation. If enough of these black holes were forged, the thinking goes, they could provide the invisible mass that forms the substrate of galaxies, galaxy clusters and the cosmic web.
Astronomers look for PBHs using microlensing, the boost in starlight created when a black hole passes in front of a more distant star and its gravity bends some of the star’s light toward Earth. This lensing effect creates multiple images of the star too tiny to resolve individually, but combined they create a bright blip. Previous microlensing surveys have found a handful of candidate PBHs, but not a single definitive discovery, said Nathan Golovich of Lawrence Livermore National Laboratory. Unfortunately, the astronomers can’t determine with current data whether this single candidate is the flash from a primordial black hole passing in front of a star.
“This is an impressive measurement,” Golovich said. The team has essentially crossed out a large chunk of the contribution PBHs in this mass range might make to dark matter: The remaining fraction is less than a hundredth.
High-speed images of a common laser-based metal 3D printing process, coupled with newly updated computer models, have revealed the mechanisms behind material redistribution, a phenomenon that leads to defects in printed metal parts.
Researchers from GE Research and Lawrence Livermore National Laboratory are working to create open-source software to control 3D printers, giving researchers greater control over the metal-melting process than they could get with commercial software.
In the final phase of the collaboration, the team is building a working system that aims to speed up the printing process once again. Increases in speed typically come from three sources: using more lasers, using more powerful beams to melt thicker metal layers faster or tweaking the process to find more efficient paths for the lasers that already exist.
Unfortunately, the easiest solutions come with new problems of their own. To handle that problem, Livermore's Manyalibo "Ibo" Matthews is using a camera running at up to 10 million frames per second to show what happens when the laser hits the "melt pool" where the metal particles fuse together.
Asteroid Bennu is one of the largest space objects close to Earth. Photo courtesy of NASA Goddard Space Flight Center
Faced with the prospect of a sizable asteroid heading toward Earth and causing doomsday, humanity has come up with various responses.
NASA’s Planetary Defense Coordination Office, which keeps an eye on asteroids and comets that will one day pass close to Earth, suggests changing a space rock’s trajectory by giving it a small nudge well in advance of reaching Earth. NASA and others aim to test this strategy in 2022 with the Double Asteroid Redirection Test, in which a spacecraft will deliberately crash into the smaller member of a binary asteroid system in an attempt to change its orbit around the larger body.
Ultimately, the choice between deflection and destruction largely depends on how quickly an incoming asteroid is spotted.
“A successful deflection becomes more difficult to execute as warning time decreases,” said Megan Bruck Syal, a planetary defense researcher at the Lawrence Livermore National Laboratory. “For the shortest warning times, robust disruption and dispersal of the fragments may be the only viable option to prevent the impact.”