Nav: Home

Russian physicists make toy asteroids and blast them with a laser

March 13, 2018

A large team of Russian researchers from Rosatom, joined by three MIPT physicists, has modeled the impact of a nuclear explosion on an Earth-threatening asteroid. They manufactured miniature asteroids and blasted them with a laser. The modeling technique developed in this study is a way of experimentally evaluating asteroid destruction criteria such as the explosion energy needed to eliminate a dangerous object on a collision course with Earth. The English translation of the paper reporting the results will appear in the upcoming issue of the Journal of Experimental and Theoretical Physics.

Asteroids are celestial bodies consisting of carbon, silicon, metal, and sometimes ice. Scientists usually classify objects larger than 1 meter as asteroids, although this lower limit is disputed. On the other end of the scale, asteroids get as big as 900 kilometers across. Traveling at 20 kilometers per second, such giants pose a threat of obliterating all life on Earth.

There are two basic options when it comes to protecting the planet from a collision with an asteroid: It either has to be deflected or blown into pieces most of which will miss us or burn up in the atmosphere. The authors of the paper explored the second option by modeling the effects of a powerful shock wave released by a nuclear explosion on the asteroid surface. The research team showed that a brief laser pulse aimed at a miniature replica of an asteroid produces destructive effects similar to those of a nuclear explosion on an actual space rock. The distributions of heat and pressure predicted for the real event generally matched those measured in the scaled-down experiment.

For their laser model to be accurate, the researchers made sure the density and rigidity of the small-scale asteroid -- and even its shape -- mimicked the real thing, and controlled the shock-wave pressures. Thanks to this precise correspondence, the researchers had a way of directly calculating the required energy of a nuclear explosion on the actual asteroid from the energy of a laser pulse destroying its miniature replica. Thus, for example, to eliminate a 200-meter asteroid, the bomb needs to deliver the energy equivalent of 3 megatons of TNT. This was calculated once the team measured that it took a 500-joule laser pulse to destroy a model 8-10 millimeters in diameter. For the sake of comparison, the most powerful explosive ever detonated -- Tsar Bomba, or "king of bombs," built by the Soviet Union in 1961 -- had an energy output of about 58.6 megatons, though accounts vary.

The research team came up with a technology for manufacturing artificial asteroid material. Its composition corresponds to that of the chondrite (stony) meteorites, which account for about 90 percent of asteroid remains reaching the surface of the Earth. The properties of the model asteroid, including its chemical composition, density, porosity, and rigidity, were adjusted during manufacturing. The replicas were made using the data on the chondrite meteorite recovered from the bottom of Lake Chebarkul. It is the largest fragment of the asteroid that entered the Earth's atmosphere in February 2013, exploding over Chelyabinsk Oblast, Russia. The asteroid material was manufactured using a combination of sedimentation, compression, and heating, imitating the natural formation process. Out of cylinder-shaped samples, imitation asteroids of various shapes were made, among them spherical, ellipsoidal, and cubical ones.

To confirm that their laser modeling fits in with reality, the researchers also did compressible flow calculations. They showed that a lab asteroid 14-15 orders of magnitude less massive than its space prototype requires almost twice as much energy per unit mass to be completely disrupted.

The experiments made use of three laser devices: Iskra-5, Luch, and Saturn. The laser beam was first amplified to a predetermined power and then directed at the asteroid replica fixed in a vacuum chamber. Model destruction was monitored from behind as well as from the side, and fragmentation dynamics were registered. The laser affected model asteroids for 0.5-30 nanoseconds.

To estimate asteroid destruction criteria, researchers analyzed the data available from the Chelyabinsk meteorite. It entered the Earth's atmosphere as a 20-meter asteroid and fractured into small fragments that caused no catastrophic damage. It therefore makes sense to say that a 200-meter asteroid has been eliminated if it is fractured into pieces with a diameter 10 times smaller and a mass 1,000 times smaller than the Earth-threatening rock itself. For obvious reasons, this conclusion only holds for a 200-meter asteroid entering the atmosphere at a similar angle and for fragments traveling along trajectories similar to that of the Chelyabinsk meteor.

The researchers were also interested in whether the explosion effect is cumulative -- that is, can one powerful explosion be replaced by a succession of smaller ones? They found that multiple weaker laser pulses provide no significant advantage over a single pulse combining their power in terms of the general destruction criterion. This holds for simultaneous as well as consecutive pulses.

In some of the experiments, the laser was targeted at a cavity made in the miniature asteroids ahead of time. By exploiting the cavity, the researchers spent less energy -- namely, 500 instead of 650 joules per gram. Similarly, the effect of a buried nuclear bomb is expected to be more pronounced.

Calculations accounting for the scaling effects indicate that it takes a 3-megaton bomb to eliminate an Earth-threatening nonmetallic asteroid measuring 200 meters across. The research team now plans to expand the study by experimenting with asteroid replicas of different composition, including those containing iron, nickel, and ice. They also intend to identify more precisely how the shape of the asteroid and the presence of cavities on its surface affect the general destruction criterion.

"By accumulating coefficients and dependencies for asteroids of different types, we enable rapid modeling of the explosion so that the destruction criteria can be calculated promptly. At the moment, there are no asteroid threats, so our team has the time to perfect this technique for use later in preventing a planetary disaster," says study co-author Vladimir Yufa, an associate professor at the departments of Applied Physics and Laser Systems and Structured Materials, MIPT. "We're also looking into the possibility of deflecting an asteroid without destroying it and hope for international engagement."
The paper reporting the results of the study was published in the Russian edition of the Journal of Experimental and Theoretical Physics by a team of researchers from Rosatom -- a Russian atomic power state corporation -- as well as from MIPT and the Space Research Institute of the Russian Academy of Sciences. The two Rosatom institutes involved in the study are the All-Russian Scientific Research Institute of Experimental Physics and the Troitsk Institute for Innovation and Fusion Research.

Moscow Institute of Physics and Technology

Related Nuclear Articles:

US nuclear regulators greatly underestimate potential for nuclear disaster
The US Nuclear Regulatory Commission relied on faulty analysis to justify its refusal to adopt a critical measure for protecting Americans from nuclear-waste fires at dozens of reactor sites around the country, according to an article in the May 26 issue of Science magazine.
Visualizing nuclear radiation
Extraordinary decontamination efforts are underway in areas affected by the 2011 nuclear accidents in Japan.
New path suggested for nuclear fusion
Scientists at Rice University, the University of Illinois at Urbana-Champaign and the University of Chile offer a glimpse into a possible new path toward the production of energy through nuclear fusion.
Physics: Toward a practical nuclear pendulum
Researchers from Ludwig-Maximilians-Universitaet (LMU) Munich have, for the first time, measured the lifetime of an excited state in the nucleus of an unstable element.
Researchers model the way into a nuclear future
The main type of nuclear fuel is the uranium oxide pellet composition.
Nuclear CSI: Noninvasive procedure could identify criminal nuclear activity
Determining if an individual has handled nuclear materials is a challenge national defense agencies currently face.
A new method to help solve the problem of nuclear waste
The article, published recently in Open Chemistry may lead to the development of a process to remove uranium from wastewater at the front-end of the nuclear fuel cycle, or even extracting natural uranium from sea water.
Nuclear puzzle may be clue to fifth force
In a new paper, University of California, Riverside theoretical physicist Flip Tanedo and his collaborators have made new progress towards unraveling a mystery in the beryllium nucleus that may be evidence for a fifth force of nature.
New approach to nuclear structure, freely available
The atomic nucleus is highly complex. Understanding this complexity often requires a tremendous amount of computational power.
Nuclear physics' interdisciplinary progress
The theoretical view of the structure of the atom nucleus is not carved in stone.

Related Nuclear Reading:

Command and Control: Nuclear Weapons, the Damascus Accident, and the Illusion of Safety
by Eric Schlosser (Author)

Nuclear Energy: An Introduction to the Concepts, Systems, and Applications of Nuclear Processes
by Raymond Murray (Author), Keith E. Holbert (Author)

Atomic Accidents: A History of Nuclear Meltdowns and Disasters: From the Ozark Mountains to Fukushima
by James Mahaffey (Author)

Atomic Awakening: A New Look at the History and Future of Nuclear Power
by James Mahaffey (Author)

The Doomsday Machine: Confessions of a Nuclear War Planner
by Daniel Ellsberg (Author)

The Second Nuclear Age: Strategy, Danger, and the New Power Politics
by Paul Bracken (Author)

U.S. Armed Forces Nuclear, Biological And Chemical Survival Manual
by Dick Couch (Author)

Introduction to Nuclear Engineering
by John R. & Baratta Anthony J. Lamarsh (Author)

The Logic of American Nuclear Strategy: Why Strategic Superiority Matters (Bridging the Gap)
by Matthew Kroenig (Author)

Atomic Adventures: Secret Islands, Forgotten N-Rays, and Isotopic Murder: A Journey into the Wild World of Nuclear Science
by Pegasus Books

Best Science Podcasts 2018

We have hand picked the best science podcasts for 2018. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

We're told if the economy is growing, and if we keep producing, that's a good thing. But at what cost? This hour, TED speakers explore circular systems that regenerate and re-use what we already have. Guests include economist Kate Raworth, environmental activist Tristram Stuart, landscape architect Kate Orff, entrepreneur David Katz, and graphic designer Jessi Arrington.
Now Playing: Science for the People

#504 The Art of Logic
How can mathematics help us have better arguments? This week we spend the hour with "The Art of Logic in an Illogical World" author, mathematician Eugenia Cheng, as she makes her case that the logic of mathematics can combine with emotional resonance to allow us to have better debates and arguments. Along the way we learn a lot about rigorous logic using arguments you're probably having every day, while also learning a lot about our own underlying beliefs and assumptions.