One of the biggest achievements of humanity in the past century has been the discovery of manned space flight. It is quite a risky business, with precise calculations that need to be performed to put an object successfully in orbit around the Earth. A small miscalculation can result in disaster, causing unfortunate death and huge financial losses. Yet, despite all the risks, our fascination with outer space forces us to seek more answers.

So far, a total of 121 people have lost their lives in the mission of pushing the boundaries of human technology beyond the reaches of our planet. Some perished in training accidents while others never made it back. The causes for most of these usually boil down to three categories: technical defects, overconfidence, and blunders by the management. A famous example of this was the Space Shuttle Challenger, a small object like the O-ring which wasn’t properly sealed resulted in a disaster which ended up being the most tragic in NASA’s history.

Humankind’s spaceflight history is filled with accidents and disasters, some fatal while others not so much but the possibility for more of these still remains as we plan on colonizing Mars. Here we take a look at some of the worst accidents to happen during space travel in human history.

15. Parachute Failure Upon Reentry- Soyuz 1

Yuri Gagarin might’ve been the first human in space but it was Soviet cosmonaut Vladimir Komarov who flew the first manned mission of the Soyuz spacecraft called Soyuz 1. Some of the objectives of this flight were quite complex, involving a rendezvous with another Soyuz spacecraft and an exchange of crew members before their return to Earth.

Flight of the Soyuz 1 was marred with difficulties right from the start when one of the solar panels failed to unfold, leaving the spacecraft without adequate power. After completing 18 orbits around Earth, Soyuz 1 started its re-entry procedure after firing its retrorockets. Despite the technical failures, Komarov might’ve landed safely but disaster struck when the parachutes intended to slow the spacecraft failed to deploy, hurling the Soyuz 1 to the ground at a speed of 140 km/h (89 mph). This became the first ever in-flight fatality in the history of spaceflight.

14. Valve Leak Results In Rapid Decompression – Soyuz 11

The International Space Station isn’t the first structure to be put in orbit around the Earth, in fact, the world’s first space station was the Salyut 1 and the Soyuz 11 was tasked with a mission to board it. Previous attempts had been unsuccessful due to a number of reasons so all hopes were on the Soyuz 11. The crew managed to successfully dock and get on board the space station on June 7, 1971.

Despite some minor technical difficulties and a fire breaking out, the crew was able to get most of their required tasks done. The Soyuz 11 departed the space station on 30 June and fired its retrorockets for a reentry procedure. Everything seemed to have gone smoothly as the capsule arrived on Earth, however, the recovery team found all the crew to be dead upon recovering it. The cause of their deaths was determined to be asphyxiation which was the result of rapid decompression due to a ventilation valve leak. The Soyuz 11 crew are the only humans to have died in space.

13. Cold Weather Causes Disaster – Space Shuttle Challenger

If you were old enough to be aware of things around you in 1986, you probably remember the terrible day on which the Challenger disaster happened. It was an event which was witnessed live all over the world and more specifically the United States. What made this mission special was the presence of Christa McAuliffe among the crew, who would’ve become the first teacher in space.

Despite reservations about the launch by different NASA scientists due to extremely cold weather, it was cleared for launch. On January 28, 1986, Space Shuttle Challenger disintegrated 73 seconds into its flight over the Atlantic Ocean, resulting in the deaths of all seven crew members. The cause of the accident has been attributed to an O-ring seal which wasn’t designed to be used under cold conditions.

12. Damaged Insulation Ends In Fatal Reentry – Space Shuttle Columbia

Development of the Space Shuttle had marked an important turning point in the creation of reusable spacecraft technology. Unlike traditional rocket systems like the Saturn V, Space Shuttles could be used to both launch the astronauts and safely return them back to Earth. Unfortunately, this still didn’t guarantee that there wouldn’t be a chance of disaster.

The Space Shuttle Columbia suffered a grim fate when it broke up into the atmosphere of Earth during reentry. This resulted in the deaths of all seven crew members and it was the second disaster to occur in the Space Shuttle Program after Space Shuttle Challenger. A piece of foam insulation that broke off and struck the left wing of the orbiter was determined as the cause of the accident.

11. Destroyed During Flight – X-15 Flight 191

Over the course of the years, NASA has done testing on a number of experimental aircraft designed to achieve high altitudes. One of these was the X-15 which was a hypersonic rocket-powered aircraft that set numerous altitude and speed records. What started out as a routine test flight of the aircraft piloted by Michael J. Adams ended in a disaster aftter the aircraft broke apart mid-air because of technical difficulties resulting in Adams’ death.

The X-15 was launched from underneath an NB-52B mothership at a height of over 45,000 ft. Everything was going fine until an electrical disturbance occurred which messed up the controls of the aircraft. All of the attempts by Adam to bring the X-15 under control proved futile and the aircraft was destroyed 10 minutes and 35 seconds after launch.

10. Trainer Jet Crash From Bad Weather – Gemini 9

The Gemini program was a series of manned spaceflights by NASA and the Gemini 9 was supposed to be the 7^th manned flight in this series. Command pilot Elliot See and pilot Charles Bassett were chosen as the crew for this mission, however, both the pilots were killed after their T-38 trainer jet crashed on its way to St. Louis, Missouri due to the poor visibility and adverse weather conditions at Lambert Field.

This meant that the mission was to be flown by backup pilots Thomas P. Stafford and Eugene Cernan. The Gemini 9A launch was successful but the required objectives could not be completed because of a number of technical errors and difficulties.

9. Damaged Service Module – Apollo 13

Apollo 13 was the third mission intended to land on the moon after two previous successful landings. Things started to go wrong soon after launch as the second-stage center engine shut itself off a whole two minutes before it was actually supposed to. However, this was nothing compared to what happened 56 hours into the mission and almost 330,000 km away from Earth. A loud bang was heard by the astronauts in the Command/Service Module after which the oxygen in the tanks dropped to zero and fuel cells shut down.

This forced the crew to use the Lunar Module as a lifeboat which meant that a lunar landing could no longer be attempted. Despite all of the hardships faced by the crew, they were able to successfully and safely return to Earth six days after launch.

8. Failed Separation During Reentry – Soyuz 5

This specific Soyuz mission was launched with one objective in mind, to perform the first ever docking of two manned spacecraft and attempt a transfer of crew. It was piloted by Commander Boris Volynov who had to dock it with a Soyuz 4 and transfer flight engineers Aleksei Yeliseyev and Yevgeny Khurnov via a spacewalk.

All of these objectives were successfully met as Volynov remained behind on the Soyuz 5 to attempt, perhaps one of the most remarkable reentries in the history of spaceflight. The service module attached to the Soyuz had failed to separate, resulting in a nose dive with the descent module facing the hot airstream. Before the entry hatch could burn, however, the service module broke off and the descent module corrected itself, saving Volynov from what would’ve been certain doom.

7. Struck By Lightning, Twice – Apollo 12

The Apollo 12 mission was unfortunate in the sense that the spacecraft was struck twice by lightning after launch. The first strike occurred shortly after launch, at 36 seconds which made three of the fuel cells to go offline, forcing the craft to automatically switch to reserve battery power. This is not the end of the story though as a second lightning strike hit a short while after at 52 seconds, effectively knocking offline the onboard guidance platform.

Some of the permanent damages caused by these strikes were four temperature sensors on the Lunar Module which were burnt out and failure of some of the measuring devices in the RCS. Luckily the fuel cell power was restored after a few minutes and the astronauts made sure everything was in working order before departing for the Moon.

6. Emergency Launch Abort – Soyuz 18a

Unlike the Space Shuttles, rockets often had abort procedures to save the crew’s life in case something went wrong after launch. The Soyuz 18a mission almost ended in a disaster when the second-stage failed to separate, veering the rocket off course and putting it on an acceleration path towards Earth.

This triggered an emergency reentry sequence which caused such a large amount of acceleration that the crew had to endure 21.3 g of it compared to the 15 g which is usually expected for an abort. The crew eventually survived the landing, however, Lazarev, who was the mission commander sustained internal injuries which prevented him from ever flying again.

5. Exposure To Toxic Gas – Apollo Soyuz Test Project

Spaceflights are a dangerous business, one small problem can jeopardize the entire mission and put the lives of the crew at risk. The Apollo Soyuz Test Project was an experimental mission which was the first ever space collaboration between the United States and the Soviet Union. The objective of this flight was to dock an Apollo Command/Service module with a Soyuz 19 spacecraft.

Everything went as planned up until the point where the Apollo started to descend and had to deploy its parachute. Toxic nitrogen tetroxide gas which was venting from the spacecraft started to enter the cabin due to a switch which was left in the wrong position. The crew was exposed to this toxic gas throughout their descent and developed chemical-induced pneumonia upon landing. They were hospitalized for two weeks in Hawaii and all of them were able to successfully recover.

4. Collision In Space – Mir Space Station

The Mir was a space station launched by Soviets in 1986 which operated until 2001 after which it was replaced by the International Space Station. A number of technical issues had plagued it since launch including the time when a leaked lithium perchlorate canister caused a fire to break out on board the station which burned for almost 90 seconds.

A much serious accident, however, happened on June 25, 1997, when a Progress M-34 cargo freighter ended up colliding with the Spektr module of the space station. This seriously damaged the solar arrays used for power generation and left a hole in the Spektr module, resulting in the depressurization of the Mir. Luckily, there was no loss of life as the crew present on board at the time managed to close off the damaged module from the rest of the station.

3. Almost Drowned In Space – ISS Expedition 36

If somebody told you the story of an astronaut who almost drowned in space, you would have every reason to not believe them, after all, there is no water in space, right? The problem in space, however, is that there is almost zero gravity so everything floats and behaves differently than it would on Earth, including liquids.

During an EVA (extra vehicular activity) mission on the International Space Station, ESA astronaut Luca Parmitano reported the presence of liquid inside his helmet. This was a huge cause for concern and flight controller immediately decided to abort the mission, instructing Parmitano to return back to the airlock. During the time that it took for the airlock to depressurize, enough water had accumulated in Parmitano’s suit that he was having difficulty communicating. Fortunately, his helmet was removed before he could suffer any injuries. The cause of the leak was determined to be a design flaw in the suit’s coolant system.

2. Failed Thruster Causes Uncontrolled Spin – Gemini 8

Everyone knows that Neil Armstrong was the first man to set foot on the Moon, however, something that a lot of people don’t know is that he had flown other missions as well before the Apollo 11. One of these was the Gemini 8 which would’ve ended in a disaster if it wasn’t for Armstrong’s quick thinking.

On March 17, 1966, one of the maneuvering thrusters on the spacecraft malfunctioned and refused to shut down, putting it into an uncontrolled spin. By the time that Neil Armstrong decided to regain control, the capsule was spinning at almost one revolution per second. The main altitude system had to be turned off and the reentry system had to be engaged to bring the spacecraft under control, effectively causing an early end to the flight.

1. Fatal Electrical Fire – Apollo 1

While this particular incident did not happen in space, it still serves as a reminder of all the risks that were involved in putting a man on the Moon. Apollo 1 was the first manned mission of NASA’s Apollo program and it was supposed to test the Apollo Command/Service Module in low Earth orbit. The launch never happened though, as a cabin fire during the launch rehearsal test resulted in the deaths of all three members.

A board was setup to determine the cause of the fire, which was later revealed to be a malfunctioning electrical component. The fire spread quickly because of the highly combustible nylon material and an oxygen rich atmosphere. It was an unfortunate event but one that paved the way for better safety systems for astronauts in the future.