Planetary Defense (Part 2)

Asteroids have reshaped Earth before—and scientists know another impact is inevitable. When traditional deflection methods won’t work, what’s the last resort? At LLNL, experts are exploring nuclear deflection.

• 0:02Speaker 00

  You were driving home from work on a quiet evening when the sky erupted in a flash of light.

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  You gripped the wheel, your heart pounding. The intense, searing brightness forced you to shield your eyes and pull over, instinctively ducking your head and covering your ears. Then, it hit.

• 0:26Speaker 00

  A deafening explosion shook your car, shattering windows and nearby buildings as the air seemed to vibrate with an immense, unrelenting force. Everything went still. You tried to process what just happened. Was it a plane crash, a bomb? The truth is even more extraordinary. A massive object from space had just entered Earth's atmosphere. This is not as far-fetched as it sounds. In 2013, in Chelyabinsk, Russia, a house-sized asteroid raced through the atmosphere at over 40,000 miles per hour, exploding with the force of 30 Hiroshima bombs.

• 1:10Speaker 00

  It injured over 1,500 people and caused damage across miles of the city. And that was a small one. Now, imagine an asteroid the size of a city, heading toward us as its path intersects with Earth's orbit. Scientists have limited options. And one of those options, the most extreme, is nuclear deflection. This is the second episode in our Planetary Defense series. Today, we dive into the boldest strategy humanity has for planetary defense. What are the risks of using nuclear energy to stop an asteroid? And what does it take to protect our planet from a force of nature that's been around for billions of years?

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  Let's explore the science and stories behind the ultimate planetary defense challenge: Stopping an asteroid with nuclear energy.

• 2:07Speaker 00

  Welcome to the Big Ideas Lab, your weekly exploration inside Lawrence Livermore National Laboratory. Hear untold stories, meet boundary pushing pioneers, and get unparalleled access inside the gates. From national security challenges to computing revolutions, discover the innovations that are shaping tomorrow, today.

• 2:37Speaker 00

  Asteroids might seem like distant curiosities, tiny specks floating in space. But their orbits often bring them uncomfortably close to Earth. And "close" in space terms means within roughly 28 million miles of Earth's orbit. And while many asteroids pass harmlessly, a select few pose a real danger. Cody Raskin is a design physicist at Lawrence Livermore National Laboratory.

• 3:04Speaker 01

  Planetary Defense is tasked with coming up with scientific applications with the goal of deflecting asteroids that might hit the Earth at some time in the future. There are a lot of Earth-crossing asteroids. Not all of them have been found or detected. And the properties of these asteroids are very unknown at this point. So we work on ways to constrain the properties of those asteroids and different ways that you could try to deflect them in case one of them was going to hit the Earth.

• 3:34Speaker 00

  Asteroids come in different sizes, shapes, and compositions. Some are small enough to burn up harmlessly in the atmosphere, while others, which can be the size of a city, have the potential to cause devastation.

• 3:48Speaker 01

  The most common size is about somewhere between the size of a car and the size of an office room. Something the size of a car doesn't pose very much of a threat because it would burn up in the atmosphere. Something larger than that can actually survive the entry into the atmosphere and hit the ground. And the larger it is, obviously, the greater the impact on the ground, the greater the destruction. These are very much larger ones, hundreds of meters across. They can cause destruction of an entire city.

• 4:18Speaker 00

  The strategy for deflecting an asteroid depends on its size, speed, and distance from Earth. For smaller threats, kinetic impact, or essentially crashing a spacecraft into the asteroid, may be enough to nudge a space rock off course. Tune into our previous episode to learn all about that process. But for larger or more imminent threats, scientists need something even more powerful. That's where nuclear deflection comes in.

• 4:47Speaker 02

  I work on the planetary defense team, and my job is specifically to explore the nuclear mitigation option.

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  That's Mary Berkey, a staff scientist at Lawrence Livermore National Laboratory. Nuclear mitigation relies on nuclear devices to alter an asteroid's trajectory or composition. This approach is typically used in extreme scenarios where time is limited, or the asteroid's size and makeup render other methods ineffective. The immense energy of a nuclear detonation can either redirect the asteroid away from Earth, or break it into smaller, less hazardous pieces. The two techniques for nuclear mitigation are standoff detonation and surface detonation. Standoff detonation involves detonating a nuclear device at a distance from the asteroid.

• 5:36Speaker 01

  You could actually detonate a nuclear device near the asteroid and deposit enough of its energy into the material of the asteroid, such that it would blow off.

• 5:49Speaker 00

  The resulting burst of heat and radiation vaporizes part of the asteroid's surface, creating a "rocket effect" as the expelled material pushes the asteroid onto a new path. This method minimizes the risk of creating large, dangerous fragments. The second approach, surface detonation, places the device directly on or near the asteroid's surface. This delivers a more powerful energy transfer, and would typically be used to intentionally disrupt the asteroid, breaking it into many well-dispersed fragments.

• 6:21Speaker 02

  If you want to give it a gentle push, you can move your device far away and detonate it there. If it's small enough and there's a chance that you could actually like blow it to bits, you can bring your device really close and detonate it there and blow it into all tons of tiny, fast-moving particles that will go out in every direction and all of them will miss Earth if you do it a couple of months in advance.

• 6:42Speaker 00

  Timing is critical in any scenario involving an asteroid on a collision course with Earth. The defense strategy must be carried out within the window between detecting the threat and its projected impact.

• 6:54Speaker 02

  It takes about three years to build a spacecraft to do a flyby mission in deep space.

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  Building a spacecraft for a deep-space mission requires years of meticulous planning, engineering, and testing. As soon as a potential asteroid threat is identified, those three years become a critical part of the response window. The complexity lies not just in constructing the spacecraft itself, but also in integrating specialized instruments, ensuring reliable propulsion systems, and running rigorous tests to simulate the extreme conditions of deep space. So, how does nuclear deflection actually work?

• 7:49Speaker 00

  Something's not right. Too much time is gone by. In Hollywood, heroes detonate bombs directly onto the asteroid.

• 7:58Speaker 03

  Zero barrier is about to be breached. One minute. Hey, come on, press that button.

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  It's ready, Bryce!

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  Pass it!

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  We have detonation. Verbi detonation. But in reality, scientists back on Earth in a lab are the real heroes. They aim for a controlled, precise explosion at a distance, delivering just enough energy to alter the asteroid's trajectory. Here's Mike Owen. He's a computational physicist at Lawrence Livermore National Laboratory.

• 8:34Speaker 04

  Asteroids are not simple things. They're mostly built up of smaller rocks that happen to loosely get together due to gravity pulling them together. But they are really loose. They can come apart if you just spin them too fast. And that happens to a lot of them in the solar system. They will get spun up by just interactions with basically heating from the sun. And they'll spin up and then they'll start to throw off pieces of themselves. And that's why sometimes asteroids have smaller asteroids as moons.

• 8:56Speaker 00

  Nuclear deflection is about precision. And understanding how the asteroid will respond to the blast requires detailed modeling of everything. The asteroid's shape, composition, and even the direction and force of the explosion.

• 9:11Speaker 04

  You don't have to hit them very hard to break them up. They're very fragile, actually. You hit them hard enough so that you know you break it up really robustly, so it just flies to bits and all the pieces fly everywhere and most of it would never hit Earth because you dispersed it. It's that middle ground you gotta worry about where you just barely break it up. That's what you don't want.

• 9:25Speaker 00

  Here's where modeling comes in. Using complex equations and simulations to predict how an asteroid will respond to different levels of force.

• 9:34Speaker 04

  We try to describe it all with mathematics. So we try to write the equations to describe things we're interested in, like the way a ship might move through the solar system following gravity, or the way gases or fluids or solids will react if you do something to them or hit them or they collide and come together. Since we have all these equations that we use to try to understand these things, those equations are often very, very complex and sometimes we can't solve them on paper to get the entire answer.

• 9:59Speaker 00

  Solving these equations often requires computational models to simulate what happens over time. Then testing the accuracy of those models and turning them into actionable science.

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  It's not science if we can't measure it. So we have to be able to make a prediction that we can then go and do an experiment and somehow say, "Did this happen according to the model I think is true or did it not happen?"

• 10:22Speaker 00

  One of the biggest challenges lies in accounting for the unpredictable nature of rubble pile asteroids. These loosely bound collections of debris can absorb or dissipate energy in unexpected ways, making it harder to predict their response to a nuclear detonation.

• 10:39Speaker 02

  It's just a whole bunch of rocks floating together in space. And that's a rubble pile asteroid.

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  Rubble pile asteroids highlight the diversity of threats that planetary defense must address.

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  Beyond the technical challenges, deploying a nuclear device in space raises significant global concerns rooted in global politics and the fragile balance of international agreements.

• 11:01Speaker 02

  The nuclear option is tricky because we live in a bit of a tense world right now. And a few decades ago, we all signed a treaty that said we were not going to do nuclear tests in space. A lot of countries signed on to that. The current state of world peace rests on everyone keeping to that agreement.

• 11:21Speaker 00

  Mary is referring to the Outer Space Treaty of 1967 and the Comprehensive Nuclear Test Ban Treaty from the mid 1990s, key agreements that formed the backbone of international space and nuclear diplomacy. These treaties were created to prevent the militarization of space and prohibit nuclear explosions, including tests in Earth's atmosphere, underwater, or in outer space. These agreements maintain peace and global security, yet also pose a significant challenge for planetary defense. Using nuclear deflection to save Earth from an asteroid likely requires nations to navigate complex legal and political hurdles, potentially breaking the agreements

• 12:05Speaker 00

  that have preserved stability for decades. The concept of nuclear deflection is both a testament to human ingenuity and a humbling reminder of our planet's vulnerabilities. When an asteroid is heading towards Earth's atmosphere, every second matters.

• 12:24Speaker 01

  I think a good analogy is an asteroid that's going to hit the Earth. It has a bus ticket and an appointment. And if the bus is five minutes late, it doesn't make its appointment. And so we're just trying to delay the bus a little bit.

• 12:36Speaker 00

  The challenge is about technology, strategy, and a global commitment to planetary defense. For all the progress made, we're still building foundations.

• 12:46Speaker 02

  Everyone's heard of the dinosaurs. Everyone's heard of what happened to them. And everyone assumes, yes, because we have advanced technology, that won't happen to us. We have all of these satellites. But it's a work in progress.

• 13:00Speaker 00

  The future of planetary defense depends on improving our ability to detect potential threats, refining our modeling techniques to predict outcomes with greater precision, and fostering the kind of international cooperation that transcends borders. The universe is vast and unpredictable. Humanity's capacity for innovation gives us a fighting chance. Whether through kinetic impact or nuclear deflection, the mission is clear. Safeguard our planet and secure the survival of life on Earth.

• 13:48Speaker 00

  Thank you for tuning in to Big Ideas Lab. If you loved what you heard, please let us know by leaving a rating and review. And if you haven't already, don't forget to hit the follow or subscribe button in your podcast app to keep up with our latest episode. Thanks for listening.