Why We Can’t “Just Blow It Up”

Why We Can’t “Just Blow It Up”

Adam Kall, Director of Science

4 minute read

In Netflix's "Space Force" a repeated comedic element is the militaristic advice to solve a problem through explosives, to the chagrin of the nearby scientists. This column details how truly terrible this suggestion would be particularly as it pertains to space. When considering the use of explosions to deal with space debris, having more energy in a smaller object is a combination worse together than the sum of its parts. Prior to an explosion, there would be a single trackable object with a determined path, so it could be calculated whether that path collided with something else, and how to move out of the way or prepare for it. If the space debris is hit with an explosion, the end result is now thousands of small pieces flying off in every direction. Because of their small size they can’t be tracked, and pieces that are still trackable could be sent into orbits which were previously clear or low risk. Except in the case where the explosion applies all its force in the opposite direction of motion, the pieces now also have more velocity and thus more kinetic energy. The equation for kinetic energy is taking the mass of an object and multiplying by the square of the velocity, so any increase in speed is not just bad, but exponentially bad.

When setting off an explosion in space, or anywhere, it does not reduce the reacting material and objects surrounding it to nothing. An explosion can be made of chemical components that, upon reacting, convert a percentage to heat or energy. The rest of the components are still physical material, along with the target, albeit in smaller and faster pieces. Typical explosions have a conversion rate of <5% while a nuclear bomb has a conversion rate of around 10%. The only explosion that would be a 100% conversion would be an antimatter bomb, but those don’t exist yet. So in all presently possible explosions, there is still mass leftover that becomes high velocity projectiles. None of the material that is the target of an explosion is immediately converted to energy, just simply made smaller and massively accelerated.

There are additional factors to consider about the impact of an explosion occurring outside an atmosphere. On Earth, an explosion creates pressure and pushes against the air around it. That air in turn pushes the air around it, and this continues out in a bubble pushing more and more air until the energy is expended. If the air is up against an object like a building, the pressure also pushes against the object and can cause a lot of damage. However, a building is often heavier than air, so it takes more energy to push and less energy makes it to the other side. If the explosion occurs in space there is no air to push, but the energy still exists and still travels outwards. Humanity, thankfully, does not have much experience with explosions in space so we’re not sure of the full extent of what would happen. One thing that is clear is that the energy would still expand outwards until it reached something, like other orbiting satellites that were never at risk from the original space debris.

So, an explosion doesn’t fix the problem and instead makes it worse. Consider if a larger bomb was used, such as a nuclear weapon. A series of high-altitude nuclear bomb tests were conducted by the United States and USSR between 1958 and 1962. The effects of the initial U.S. tests above atolls in the Pacific caused simultaneous electric failures in New Zealand and Hawaii, 1,300 kilometers apart. During the Cuban missile crisis in 1962, both sides performed several high-altitude tests, the largest of which was a Soviet 300kt warhead that caused 570km of telephone line to fuse and arc, shut down over 1,000km of underground electric lines, and started a fire in the Karaganda power plant. This fire started without other physical effects, pressure wave or otherwise, but by the invisible electromagnetic energy from the blast overcharging every wire. All of these tests also created artificial radiation belts in Low Earth Orbit that killed several early satellites. This all made the space programs of both countries question the future of manned missions if tests continued, which is why less than a year later, and while tensions were still very high, the Partial Test Ban Treaty was signed, preventing further high-altitude testing.

Explosions in space are never a good idea in general, and the idea of vaporizing space debris by using a bigger bomb is going to be even worse (and would violate several international treaties). The solution in space is never going to be “just blow it up,” but instead to use a small and directed force moving the object in a controlled fashion. This is where the concept of space debris removal becomes pertinent. This kind of force can be applied by a specifically designed spacecraft for debris removal, rather than the use of explosives. KMI is actively developing that spacecraft, in the pursuit of keeping space clear for all.