Buzz
In addition to the well-known terrestrial concerns over accidental radioactive releases (such as Chernobyl, Fukushima, and Three Mile Island), we must also be aware of potential space-related dangers. Throughout the U.S. and Soviet space exploration eras, both nations launched—or attempted to launch—devices carrying various forms of radioactive materials. While most of these missions were successful, some failed, resulting in the potential for radioactive fallout. Here are ten notable space launches involving radioactive materials that didn't go as planned.
10. Cosmos 1402 - Russia
The term RORSAT (Radar Ocean Reconnaissance Satellite) refers to a series of Soviet satellites launched between 1967 and 1988 to monitor NATO and merchant vessels using radar. These satellites, known as Cosmos satellites, were equipped with BES-5 nuclear reactors powered by uranium-235. To operate effectively, they were placed in low Earth orbit. The plan called for the reactors to be ejected into high Earth orbit once the satellites had reached the end of their operational life. However, there were several instances of failure in the program.
One of the notable failures was Cosmos 1402. When the satellite's operational life ended, the reactor failed to eject into high Earth orbit as originally intended. On February 7, 1983, the satellite reentered the Earth's atmosphere, with the reactor being the final component to return. It eventually landed somewhere in the South Atlantic Ocean.
9. Transit-5BN-3 - USA
The U.S. counterpart to the Soviet satellite equipped with a nuclear reactor is the radioisotope thermoelectric generator (RTG). RTGs are a type of nuclear reactor used to generate electricity, converting the heat produced by the radioactive decay of certain elements into usable power. These devices are essentially a form of battery and have been used as power sources in satellites, space probes, and remote facilities, such as Arctic Circle lighthouses built by the former Soviet Union. RTGs are essential when solar power is impractical and longer-lasting energy is needed beyond what fuel cells can provide. Notably, they powered spacecraft such as Voyager 1, Voyager 2, and Galileo, and were also used to power scientific experiments left on the Moon by the Apollo 12 through 17 missions (with the exception of Apollo 13, as we will discuss).
RTGs carry a potential risk of radioactive contamination. If the containment holding the radioactive fuel leaks, the material could contaminate the environment. For spacecraft, the primary concern arises if an accident occurs during the launch phase or if a spacecraft passes close to Earth after launch.
One such incident occurred on April 21, 1964, when the Transit-5BN-3 navigation satellite failed to reach its intended orbit. The spacecraft disintegrated over Madagascar, and the plutonium fuel from its RTG was released into the atmosphere over the Southern Atlantic Ocean. Traces of plutonium were later detected in the atmosphere as a result of this event.
8. 1973 RORSAT Launch - Russia
On April 25, 1973, the Soviet Union attempted to launch one of its RORSAT satellites into orbit. Unfortunately, the mission ended in failure, and the onboard nuclear reactor fell into the Pacific Ocean off the coast of Japan. Details about the event remain limited, but it is known that the USA detected radioactive traces in the region through air sampling.
7. NIMBUS B-1 - USA
The second incident involving a U.S. RTG took place on May 21, 1968, when a Nimbus B-1 weather satellite exploded shortly after launch, necessitating the destruction of the launch vehicle and the aborting of the mission. Launched from Vandenberg Air Force Base, the satellite and its RTG fell into the Pacific Ocean off California. Five months later, the RTG and its plutonium dioxide were recovered from the Santa Barbara Channel. No radioactive material was released during the incident.
6. Cosmos 367 - Russia
Cosmos 367 was a Soviet RORSAT satellite powered by a nuclear reactor, launched from the Baikonur Cosmodrome. On October 3, 1970, just 110 hours after launch, the satellite malfunctioned and was moved to a higher orbit. Beyond this, little is known about the satellite. It currently orbits the Earth at an altitude of 579 miles and travels at a speed of 4.4 miles per second. For an interesting real-time satellite tracking experience, you can see the current position of Cosmos 367 here (note that those with slow internet speeds may encounter delays).
5. Cosmos 1900 - Russia
On December 12, 1987, the Soviet Union launched Cosmos 1900, a RORSAT satellite powered by nuclear energy. By May 1988, communication was lost with the satellite, and the Soviets predicted it would reenter Earth's atmosphere sometime in September or October of that year. Around September 30, 1988, just before reentering and burning up, the Soviets attempted to eject the satellite's reactor core into high Earth orbit. However, the primary booster failed. Fortunately, the backup booster succeeded in moving the reactor core, but only to an altitude 50 miles lower than planned. As of now, the reactor core remains in low Earth orbit, slowly descending with each passing year. Eventually, it will reenter Earth's atmosphere. Currently, Cosmos 1900's reactor core orbits the Earth at an altitude of 454 miles, traveling at a speed of 16,753 mph. It completes a full orbit every 99 minutes. If you're interested in tracking its orbit, go here, but be cautious if you have slow internet speed, as this link leads to a website.
4. SNAP-10A - USA
SNAP-10A was the first and, to date, the only known instance of a U.S. nuclear reactor being launched into space (although many radioisotope thermoelectric generators have been sent up). The reactor was part of the Systems Nuclear Auxiliary Power Program (SNAP), developed under the SNAPSHOT program managed by the U.S. Atomic Energy Commission.
SNAP-10A was launched on April 3, 1965, from Vandenberg AFB aboard an ATLAS Agena D rocket, sending the reactor into a low Earth orbit over the Polar Regions. The onboard nuclear electrical generator was designed to produce 500 watts of power for up to one year. However, after just 43 days, a malfunctioning voltage regulator caused the reactor core to shut down. The reactor remains stuck in a 700-nautical-mile Earth orbit, where it is expected to stay for approximately 4,000 years.
To make matters worse, in November 1979, an event occurred that caused the vehicle to begin losing pieces. As a result, a collision cannot be ruled out, and radioactive debris could have been released.
3. Apollo 13 - USA
The daring rescue of the Apollo 13 astronauts is one of the most famous stories of space exploration. On April 14, 1970 (1970 was indeed a challenging year for space missions), an oxygen tank exploded on the spacecraft en route to the moon, causing severe damage. The astronauts, James A. Lovell, John L. 'Jack' Swigert, and Fred W. Haise, managed to orbit the moon on April 15 and returned safely to Earth on April 17, thanks to their courageous efforts and the support of engineers and scientists back on Earth.
However, the return to Earth was not originally planned to include the Lunar Module, which was supposed to leave behind the SNAP 27 radioisotope thermoelectric generator (RTG) on the moon for ongoing scientific studies. Since the Lunar Module never made it to the moon, the SNAP 27 and its radioactive RTG ended up returning to Earth with the Apollo 13 crew.
The Lunar Module reentered Earth's atmosphere on April 17, 1970. To minimize the risk of radioactive exposure, it was aimed toward the Pacific Ocean near the Tonga Trench, a deep ocean valley five miles below sea level. As designed, the RTG and its 3.9 kilograms of radioactive plutonium dioxide survived reentry and plummeted into the Tonga Trench, where it will remain radioactive for the next 2,000 years. Subsequent water tests have confirmed that the RTG is not leaking any radiation into the ocean.
A surprising outcome of the Apollo 13 mission was the survival of the RTG in its original form. The extreme reentry velocities faced by the RTG demonstrated the robustness and safety of its design.
2. Lunokhod Mission 1A - Russia
Unbeknownst to many Americans, the Soviet Union was secretly working to land unmanned rovers on the moon during the same period that the United States and Neil Armstrong were making history with their moon landing. The Lunokhod program was a series of Soviet robotic lunar rovers intended to land on the moon between 1969 and 1977. Had it not been for a launch accident, the Soviets would have reached the moon months before the Americans. On February 19, 1969, the first Lunokhod rovers were launched. Unfortunately, the rocket exploded within seconds, destroying the rovers. These rovers were equipped with Cosmos-type nuclear reactors for power, and when the rocket exploded, radioactive materials were spread over a vast area of Russia.
On November 10, 1970, the Soviets succeeded when the second Lunokhod rover successfully landed on the moon, becoming the first remote-controlled robotic rover to land on another planetary body. In 2010, the Lunar Reconnaissance Orbiter captured detailed images of the moon’s surface, revealing the tracks left by the Lunokhod rover. It was only then, forty years after its landing, that scientists were able to pinpoint the rover's final resting place on the moon.
1. Cosmos 954 - Russia
One of the more widely known incidents occurred on January 24, 1978, when the Cosmos 954 satellite unexpectedly reentered Earth’s atmosphere. This event stood out because, unlike other reentries, both the reactor and its radioactive materials reentered over land, rather than the ocean. Shortly after the launch of Cosmos 954, US officials noticed that the satellite had not achieved a stable orbit and, in fact, its orbit was deteriorating rapidly. Once it was identified as a Cosmos satellite, and thus carrying a nuclear reactor, the US immediately went into high alert, tracking the satellite and trying to predict when and where it would reenter Earth’s atmosphere and crash. The reactor was too large to burn up entirely upon reentry, and it was certain to hit Earth. When it finally fell, it landed in the sparsely populated Northwest Territories of Canada. The radioactive debris spread across 124,000 square kilometers (47,876 square miles), most of which was recovered by a specialized and secretive US radioactive emergency response team. However, it is possible that the reactor core itself is still buried deep beneath the Arctic permafrost and remains radioactive to this day. Had the satellite made one more orbit, it would have reentered over the densely populated East Coast of the United States.
