**Deflecting Asteroids with Nuclear Radiation: Insights from Sandia’s Z Machine**
The concept of utilizing nuclear weapons to redirect asteroids might appear to be purely speculative, but new findings from Sandia National Laboratories indicate that it might serve as a feasible means of safeguarding Earth against potential asteroid collisions. Nevertheless, the method operates differently than most might conceptualize. Rather than depending on the destructive force of a nuclear blast, researchers are examining how the radiation from such an explosion could vaporize sections of an asteroid’s exterior, generating sufficient energy to modify its path. This investigation makes use of one of Earth’s most formidable instruments: Sandia’s Z machine.
### The Z Machine: A Nuclear Simulation Powerhouse
At the core of this exploration is the **Z machine**, an extraordinary technological marvel located at Sandia’s Z Pulsed Power Facility. The Z machine is engineered to store and rapidly release an immense amount of electrical energy—up to 22 megajoules—in an almost instantaneous manner. Upon discharging this energy, it creates exceptionally strong electromagnetic fields, capable of ionizing substances and generating robust bursts of X-rays.
These X-rays serve to replicate the radiation that would emanate from a nuclear device in space. Pertaining to asteroid deflection, the aim is to vaporize a fraction of the asteroid’s exterior, forming a temporary atmosphere of superheated gas that applies pressure on the asteroid. This pressure can subsequently influence the asteroid’s orbital path, potentially diverting it from a collision with Earth.
### How Nuclear Radiation Could Deflect an Asteroid
The premise of employing nuclear weapons to divert an asteroid relies on the reality that, in the vacuum of space, there’s no atmosphere to transmit a blast wave. Consequently, the conventional destructive capabilities of a nuclear explosion—its shockwave—would not function as intended. Instead, the radiation generated by the explosion would vaporize a portion of the asteroid’s surface, creating a jet of superheated gas that could nudge the asteroid in a different direction.
To evaluate this theory, scientists at Sandia utilized the Z machine to model the impact of nuclear radiation on asteroid-like materials. They subjected disks of rock—namely quartz and fused silica—to intense X-ray bursts that replicated the radiation from a nuclear explosion. The objective was to determine the amount of force produced by vaporizing the rock’s surface and how this force might be employed to adjust the course of an asteroid.
### Simulating Space Conditions
One of the significant hurdles of this experiment was recreating the environment of space. In space, an asteroid would be drifting freely, with no external influences except gravity. To replicate this scenario, the researchers suspended the rock disks using thin foils. When the X-ray burst hit, the foil vaporized almost instantly, leaving the rock briefly suspended in mid-air. During this fleeting moment, the researchers were able to measure the force generated by the vaporization of the rock’s surface.
A laser interferometer was employed to monitor the movement of the rock disk, enabling the scientists to calculate the force exerted by the expanding gas. This arrangement yielded insightful data on how much momentum could be conveyed to an asteroid-like object through the vaporization of part of its surface.
### The Three Phases of Vaporization
The scientists categorized the vaporization process into three distinct phases:
1. **Initial Vaporization**: The moment the radiation impacts the rock, superheated liquid starts to flow into the vacuum, forming a gas cloud. This phase lasts for approximately 0.05 microseconds and erodes about 25 micrometers of the rock’s surface.
2. **Momentum Transfer**: As the gas expands, it begins to transfer momentum to the rock. The peak acceleration in this phase exceeded 10^7 meters per second^2 and concludes roughly three microseconds after the radiation burst.
3. **Gas Expansion**: Following the initial momentum transfer, the gas continues to expand but ceases to vaporize more material. Over the subsequent 20 microseconds, the momentum transfer gradually diminishes until the process concludes.
### Scaling Up to Asteroid Size
After gathering data from their experiments, the researchers constructed a simulation to illustrate how this process could function on a much grander scale—specifically, concerning an asteroid-sized object. The simulation considered factors such as the curvature of the asteroid’s surface, which would impact how much radiation struck various sections of the asteroid, and how the ensuing force would affect the asteroid’s orbit.
The outcomes were encouraging. The researchers estimated that a radiation pulse delivering around 1,000 joules per square centimeter could produce pressures exceeding 100 gigapascals (approximately a million times the atmospheric pressure at sea level). This pressure would be sufficient to shock-melt quartz, even in the absence of additional heating from the radiation. Based on these assessments, the researchers approximated that a nuclear radiation burst could redirect asteroids up to 4.
