What will happen if a nuclear bomb is detonated in space?
The greatest result from an exoatmospheric nuclear explosion at low altitude would be an Electromagnetic pulse or EMP. This would have the effect on a country under it of sending it back to a pre-electrical society.
Visually, there would be a very bright, momentary flash, followed a few seconds later by the mains electrical lines going dead. All radios, computers, and other electrical and electronic equipment would be permanently disabled, i.e., dead.
In addition, most of the newer vehicles could also be dead since their computers would be fried. Any satellites within line of sight could be damaged or destroyed. So communications and GPS would be interrupted or lost. The result would be non survivable for most societies on earth since they depend on electricity for power and communications.
Try to imagine, if you will, a society in which there is no electricity. No lights, no refrigerator, no iPod, iPad, Android, GPS, microwave, computers, fans, A/C, heaters, radios, or TVs. Some vehicles may still run, but the gas pumps won’t work, so when they run out of gas, they stop, too. Probably most Photovoltaics won’t work either since they are all equipped with Islanding electronics which stop power whenever the mains don’t have power.
If the explosion takes place at a higher altitude, you would only see the momentary flash and possibly a click in an AM radio.
We don’t have to speculate because, in typical early Atomic Age fashion, the US military tried it just to see what would happen. Thus, we have test shot Starfish Prime.
Starfish Prime detonation as seen through clouds from Honolulu (900 miles away from launch site, 11 pm).
Starfish Prime was part of Operation Fishbowl, a series of high-altitude nuclear tests in 1962. The US had previously done several tests involving nuclear weapons detonated about 50 miles above the Earth, but these tests had been performed hastily. They had demonstrated a lot of curious effects—for instance, people at a corresponding spot on the opposite side of the equator would instantly see huge, vivid auroras—but they hadn’t done a good job of capturing the effects with instruments and they hadn’t experimented with different altitudes. Some of the shots had also used very small nuclear weapons. And perhaps most importantly, they had noticed that the electromagnetic pulses that interfered with radios were different in these high-altitude detonations, but they needed more data to understand them.
So the military decided to perform a series of more carefully-designed, better-instrumented experiments with larger weapons at different altitudes. Well, relatively more carefully designed. They basically strapped some warheads to modified ICBMs and programmed them to fly into space and explode. Because the Pacific islands they had previously used for testing were all full of natives who, for some strange reason, didn’t really want any more nuclear testing done on their islands, they chose Johnston Island, a remote island 900 miles from Hawaii.
The original Fishbowl plan was to perform three tests:
- Bluegill, about 25 miles up
- Starfish, about 250 miles up
- Urraca, at a much higher altitude than Starfish (probably around 3–400 miles, but it’s still classified)
The planners anticipated that some of the test attempts would fail, so they decided that the first shot would have the codename, the second would have the codename followed by “Prime”, the third would use “Double Prime”, and so on.
The military did their building and planning and, only six months behind schedule, they had a Thor rocket and a nuclear warhead on the launch pad for test shot Bluegill. They ignited the rocket just after midnight, started watching it ascend, and…it vanished. The rocket was still flying, but it had disappeared from their radar tracking screens. Although its trajectory had been correct, there was no way to know if it was off course and going to fly into some of the many ships and aircraft full of instruments to monitor the test, so the range safety officer sent it a self-destruct command.
Undaunted, the military moved on to Starfish. They rolled out another rocket two weeks later, strapped a W-49 warhead to it, and ignited it. The rocket flew perfectly for 59 seconds, then the engine stopped, the rocket began to break apart, and the range safety officer sent it a self-destruct command. The rocket exploded about six miles aboveground, spreading charred pieces of rocket—some of them radioactive—across Johnston Island and the surrounding ocean.
Still not getting the hint, the military moved on to Starfish Prime. Three weeks after the first Starfish, they brought out another rocket and W-49 and, in the middle of the night, lit the fuse. This time the rocket performed perfectly, arcing 375 miles above the Earth, then descending to 250 miles before detonating its 1.4 megaton warhead.
The immediate effect was a massive electromagnetic pulse. It instantly overloaded all the instruments they had set up to measure it. Not only that, it knocked out electrical systems 900 miles away in Hawaii—300 streetlights went dark, several burglar alarms tripped, and a microwave communications link was damaged. It seemed that long power lines acted as antennas, picking up the EMP and feeding it into everything attached to the power grid. Any sensitive electronics were likely to be damaged.
The detonation also quickly created intense auroras, illuminating thousands of miles of ocean from the test site to the Samoan Islands. But the most serious effect was that it created a dangerous radiation belt around the Earth which persisted for months after the test. Satellites passing through the belt were seriously damaged; two Navy navigation satellites, three research satellites from the US, UK, and USSR, and the first communications satellite to transmit live TV across an ocean were all lost to it.
The military took one look at test shot Urraca, which was planned to detonate at an altitude with many more satellites, and said “nope”. But they kept trying with Bluegill, and Bluegill Prime succeeded in exploding on the launch pad, destroying the facility and once again spreading radioactive debris across the island.
While the military spent three months cleaning up the mess, they re-planned Fishbowl, downsizing Bluegill’s warhead and adding three relatively small-yield, relatively low-altitude tests to achieve a more manageable electromagnetic pulse. Bluegill Double Prime once again managed to shower Johnston Island with debris, but Bluegill Triple Prime worked properly, except that it permanently damaged the eyesight of two servicemembers. The new tests—Checkmate, Kingfish, and Tightrope—went off without a hitch.
The Soviets ran their own series of high-altitude tests, this time over Kazakhstan; one of their tests produced a similarly gigantic EMP, which fried about a thousand miles of telephone and power lines and caused a fire that burned down a power plant. Around this time, the US and Soviet Union finally realized that aboveground nuclear tests were a deeply stupid thing to do and agreed to ban them.
So, the answer to your question is: A nuclear bomb detonated in space doesn’t create a shock wave; instead, it creates a ton of radiation and some high-speed, particle-scale radioactive debris. There is no mushroom cloud—the blast is spherical and continues to visibly glow for many minutes.
If the detonation is near a planet with a magnetic field and atmosphere, it interacts with them to create auroras, radiation belts that cook satellites for months, and a huge electromagnetic pulse that would probably fry a nation’s electrical grid and everything attached to it. If there are people on that planet, they might feel the heat of the blast on their faces; if those people aren’t wearing protective goggles, they might slowly regain some of their eyesight over the next six months. However, very little radiation reaches the ground.