Sept. 23, 2022
Artist's impression of a fiery asteroid heading for Earth. Image courtesy NASA Goddard Space Flight Reto Stöckli.
It’s HAMMER time
On Sept. 26, NASA's DART (Double Asteroid Redirection Test) spacecraft will smash into the small moon of asteroid Didymos. Telescopes on Earth will measure the resulting change in the moonlet’s orbit, while the European Space Agency’s (ESA’s) Hera mission will study the damaged target up close in 2026.
Why is NASA doing this? Well, over its 4.5-billion-year lifetime, Earth has been battered and pummeled by cosmic collisions. Some 50,000 years ago, a small asteroid slammed into northern Arizona, USA, leaving a 1,200m-wide impact crater and turning the area into a wasteland.
Suppose a near-Earth asteroid is detected tomorrow that is going to impact Earth in 2070. That gives us enough warning time: a tiny change of velocity now will be enough to change its course, so that by the time it crosses Earth’s orbit in 50 years our planet will no longer be in its way.
Even then, a DART-like impact won’t be enough to veer a much larger asteroid off course.
That’s why technicians at Lawrence Livermore National Laboratory have designed a much more powerful "kinetic impactor," called HAMMER (Hypervelocity Asteroid Mitigation Mission for Emergency Response).
Measuring 9 meters in length and weighing almost 9 tons, with enough warning time HAMMER could successfully deflect a 500 m-diameter object like Bennu — the asteroid studied by OSIRIS-REx, which has a minute chance of impacting Earth on Sept. 25, 2135.
The image features an abstracted form of flerovium. The two main colors represent the creation of the element from calcium and plutonium. The background features abstracted particle trails and sections from the ground plan of the accelerator at the Joint Institute for Nuclear Research. Image courtesy of Royal Society of Chemistry/Murray Robertson.
Heavy metal
An international research team including Lawrence Livermore scientists has succeeded in gaining new insights into the chemical properties of the superheavy element flerovium — element 114 — at the accelerator facilities of the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt.
The measurements show that flerovium is the most volatile metal in the periodic table. Flerovium is thus the heaviest element in the periodic table that has been chemically studied.
In the periodic table, flerovium is placed below the heavy metal lead. However, early predictions had suggested that relativistic effects of the high charge in the nucleus of the superheavy element on its valence electrons would lead to noble gas-like behavior, while more recent ones had rather suggested a weakly metallic behavior.
The new results show that, as expected, flerovium is inert but capable of forming stronger chemical bonds than noble gases, if conditions are suitable. Flerovium is consequently the most volatile metal in the periodic table.
The NIF Target Bay: NIF’s 192 laser beams converge at the center of this giant sphere to make the tiny hydrogen fuel pellet implode.
How do you know if a nuclear weapon will work?
In 1995, after the Soviet Union had dissolved and fear of a nuclear exchange had receded, world powers indefinitely renewed the Non-Proliferation Treaty (NPT), a 1970 agreement to prevent new states from obtaining nuclear weapons and to induce those that already had them to disarm.
A year later the U.S. signed the Comprehensive Nuclear-Test-Ban Treaty (CTBT), intended to prohibit “any nuclear weapon test explosion or any other nuclear explosion” anywhere in the world. These treaties did not stop U.S. efforts to ensure the readiness of its nuclear arsenal, however. Under the Stockpile Stewardship and Management Program, created in the wake of the CTBT, scientists research and test nuclear material, some of it at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory.
The NIF possesses 192 laser beam lines, each more than 100 meters long. The lasers are aimed in pulses of 20 billionths of a second and 500 trillion watts—roughly 1,000 times U.S. power usage at any given instant — at minute samples of plutonium and other substances. Compressed by pressures of more than 100 billion times Earth's atmosphere, the target implodes, generating a fusion reaction with temperatures more than seven times hotter than the center of the sun.
These and other experiments provide information on materials science and fusion energy. Most important, however, the data they yield, along with information from nuclear tests conducted before the ban, are fed into sophisticated simulations that conduct virtual thermonuclear explosions in a supercomputer.
Exotic magnesium (Mg) structures observed at extreme pressures (over three times the Earth’s center pressure) at the National Ignition Facility support decade-old theories that quantum-mechanical forces would localize valence electron density (gold) into spaces between Mg atoms (grey) to form "electrides.” Image by Adam Connell/LLNL.
Oh behave
Investigating how solid matter behaves at enormous pressures, such as those found in the deep interiors of giant planets, is a great experimental challenge. To help address that challenge, Lawrence Livermore National Laboratory (LLNL) researchers and collaborators took a deep dive in understanding these extreme pressures.
"Our results represent a significant experimental advance; we were able to investigate the structural behavior of magnesium (Mg) at extreme pressures — over three times higher than at the Earth's core — which were previously only accessible theoretically," said LLNL scientist Martin Gorman, who leads the project. "Our observations confirm theoretical predictions for Mg and demonstrate how TPa pressures — 10 million times atmospheric pressure — force materials to adopt fundamentally-new chemical and structural behaviors."
Gorman said that modern computational methods have suggested that core electrons bound to neighboring atoms begin to interact at extreme pressures, causing the conventional rules of chemical bonding and crystal-structure formation to break down.
Hermeus' quarter-scale "Quarterhorse" is the kind of privately funded hypersonic test aircraft DIU is seeking for its HyCAT initiative. Photo courtesy of Hermeus.
Hypersonic means going even faster
Blazing speed at blazing temperatures isn’t the only thing that makes hypersonics research hard. Too little test infrastructure, from wind tunnels to actual flight test aircraft, is constraining research. The Defense Innovation Unit is betting private sector ideas and private sector capital can make things happen faster.
The Defense Innovation Unit (DIU) is the Pentagon’s in-house commercial technology adoption accelerator. Staffed by a mix of active military and technology sector experts, it seeks to get commercial solutions in the door, scaled, and applied to DoD problems.
The portfolio of cyber, autonomy and space technologies DIU has managed to transition to the military is evidence of some success. Built on the promise of profits-to-come by non-traditional private firms, these solutions emerge and develop outside defense circles with alternative problem-solving and pace the government cannot match. That’s what DIU is hoping to tap to move military hypersonics deployment forward.
“We know that private money is being used to build [commercial] hypersonic transports for passengers and cargo,” says Barry Kirkendall, DIU’s technical director for space and an LLNL scientist. “Five or 10 years ago, that wasn’t the case, but it is now. We want to leverage that private investment, those companies for the Department of Defense.”
