Engineers are known for pushing the boundaries of scientific invention and exploration, and leading humanity down the road towards great achievements. However, every now and then, they prove they're only human like the rest of us, making serious blunders. Of course, engineering mistakes are nothing like an everyday work issue – from nuclear reaction explosions to the sinking of great vessels to explosions of space-exploring rockets; when they fail, they fail on a massive scale. And while we can certainly learn and grow from our mistakes, some of the oversights, mistakes and blunders on this list have had lasting, and devastating, effects.

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1. Chernobyl

Few people haven’t heard about the worst nuclear disaster in human history (second only to the Fukushima reactor failure in magnitude, of which more later). On April 26 of 1986, a structurally flawed reactor at Chernobyl Nuclear Power Plant exploded.

The accident that lead to the destruction of the unit 4 reactor took place during a maintenance shutdown, which served the perfect opportunity to conduct a test to determine if, during a loss of power, the turbine would still provide energy to the system to run the cooling water pumps until the emergency power supply was online.

Unfortunately, the test, which was aimed to improve the non-nuclear operational capability of the plant, was carried out without enough safety precautions. Operational errors set in motion the potentially catastrophic conditions for disaster that were already in place due to the lack of proper communication and coordination between the personnel performing the test, and the staff in charge of the reactor’s safety.

These circumstances resulted in the negligent violation of minimum operational standards during the test, and conditions became increasingly unstable in the reactor. This ultimately caused the destruction of several fuel assemblies. This in turn lead to an increase in the pressure in the reactor, and the detachment of the 1000-ton support plate holding it.

The catastrophic result was the massive release of radiation into the atmosphere, spreading over a significant area of the western Soviet Union and Eastern Europe. The subsequent evacuation involved the displacement and relocation of 350,400 people from the most polluted areas in Belarus, Ukraine and Russia. To this day, Pripyat remains inhabitable and people continue to suffer the devastating after-effects, including over 30,000 premature cancer deaths.

After the tragedy, there were several lessons to be learned. These lessons have been applied to the safety in Western nuclear plants ever since. Nowadays, reactors designed during the Soviet era show a considerable improvement in safety, not only because of the investments allocated to the improvements of their designs, but the safety culture that has arisen from this and other experiences.

2. Bhopal

In 1984, there was a toxic gas release at a Union Carbide pesticide plant in Bhopal, India. Reports show that the combination of a number of sub-standard conditions, consistent violation of safety regulations, management negligence, and overall disregard for safety was what ultimately caused what is considered the worst industrial accident in history.

The chain of events started when, somehow, water got into a methyl isocyanate (MIC) tank, triggering an exothermic reaction, which was gravely worsened by a variety of factors, including iron from corroding steel pipes. The pressure in the tank doubled in just half an hour, but was considered a malfunction in the reading instrument by two different staff members. Thirty minutes passed and the employees started feeling the effects of MIC gas exposure, and efforts were made to find the leak.

Although the leak was located, the decision made was to address the matter after the tea break. By the time the tea break ended, the condition of the tank was critical and the emergency relief valve burst open, releasing toxic MIC gas directly into the atmosphere. In addition, two of the three safety devices in place to mitigate the atmospheric release of the deadly gas were either of inappropriate size, malfunctioning, or otherwise not operational.

There were 2,259 immediate deaths and 11,000 deaths following the disaster. 25 years have passed since the event, but the land around Bhopal still remains harmful to animals and humans alike to this day.

3. Titanic

At over 800 feet in length, and a weight of 46,000 tons, the Titanic was the largest ship ever built in 1912. Although its design succeeded to impress the masses aesthetically, the many factors that contributed to its rapid sinking after it collided with an enormous iceberg while it was cruising at maximum speed (22 knots) became a matter of analysis and investigation for lots of engineering researchers.

The ship's material failures and design flaws have led researchers to believe that safety was probably not the primary focus during its construction. For example, one row of safety boats was removed from the original design to allow for more space and a better view for passengers with first-class berths. More than half of the 2200 people that were aboard the Titanic suffered the consequences of those changes made in the structure.

It only took 180 minutes after the collision for the ship to make its descent to the bottom of the Atlantic Ocean. Five of the watertight compartments were completely flooded, a critical failure probably caused by the reduction of the height of the bulkheads for better accommodation of the first-class public rooms. Researchers also attribute other causes to this failure, such as the high content of sulphur in the steel and the low temperature water, causing the hull's steel and the rivets to drastically compromise the compartments' ability to contain the flooding, thus accelerating the sinking. All these considerations are now applied to the construction of large ships as cautionary measures, and many safety regulations have been established since to avoid similar disasters to ever happen again.

4. Challenger Space Shuttle

73 seconds after its launch, on 28 January 1986, the Challenger space shuttle broke apart in a fiery explosion, killing its seven crew members.

The president of the United States at that time, Ronald Reagan, established the Rogers Commission for the investigation of the accident. Although the direct cause of the accident was suspected just a few days later, it was fully determined in a matter of weeks. Central Florida had just been swept by a severe cold wave, which caused the resiliency of two rubber O-rings to be significantly reduced. These O-rings sealed the joint between the two segments of the right-hand rocket booster. This resiliency reduction was proven by a member of the Rogers Commission by submerging an O-ring in a glass of ice water during a commission hearing.

The Rogers Commission delivered a report to the President which publicly denounced the whole organization of NASA, as well as the Marshall Space Flight Centre in Huntsville, Alabama, and Morton Thiokol, Inc., in Ogden, Utah, especially, for substandard engineering and deficient management. The Marshall Space Flight Centre was in charge of the shuttle boosters, engines, and tank, while Morton Thiokol, although only a contractor, was responsible for the booster motors, although they were assembled at the Kennedy Space Centre at Cape Canaveral, Florida. The Rogers Commission was also able to gather troubling testimonies from many engineers who had consistently expressed their concern about the reliability of the seals for no less than two years and who had advised their superiors about the possibility of a failure just the night before the launch.

As a response to the disaster and consequent questioning of its quality and safety control measures, NASA decided to add several checkpoints in the space shuttle administration, including a new NASA safety office and a shuttle safety advisory panel, in order to prevent such an unsound decision as launching that day from being made again.

5. Cleveland East Ohio Gas explosion

This disaster occurred in the afternoon of October 20th of the year 1944. 130 people lost their lives due to the explosion and resulting fires. Approximately a one square mile area on Cleveland, Ohio’s east side was also destroyed. This happened when the surface tank number 4, which contained liquefied natural gas (LNG) in the East Ohio Gas Company’s tank farm, started releasing a vapour from a defective weld bead on the side of the poorly structured tank.

The gas poured and combined with air and gas from the sewage system, which resulted in an ignition and an ensuing explosion. Thirty minutes later, a second above ground tank exploded, levelling the rest of the tank farm. Manhole covers exploded towards the sky with fireballs underground that consumed many houses and businesses in their way. The fireball was seen by Cleveland residents from at least seven miles away, while the smoke was visible from an even greater distance. It was calculated that the explosion was equal to a 2.43 kT explosion of TNT and its temperature over 3000 degrees Fahrenheit.

The incident also left a lasting change on the natural gas industry. Until the disaster, the use of surface natural gas tanks was the standard, and their presence in supply facilities for homes, office buildings and factories were a familiar view in cities across all America. After the disaster, utility companies and communities started to question the safety of their natural gas storage systems, and underground natural gas storage eventually became the new standard.

6. The Collapse of the Tacoma Narrows Bridge

The Tacoma Narrows bridge was a milestone in many ways, although not all positive. It was the first bridge design that used plate girders to support the roadbed, as well as the first cable suspension bridge, and the third largest suspension bridge at the time. Unfortunately, it was also the first bridge to suffer the consequences of not accounting for aeroelastic flutter in its design. Although this engineering flop was not as tragic casualty-wise as the rest in this list (fortunately, no one died), it really was an immense engineering failure otherwise.

Its total cost of construction was the tremendous amount of US$6.4 million back in 1940, which, considering inflation, would be approximately $115 million today, an incredible cost for an investment that only lasted four months. Not long after construction was finished, it became very noticeable how the bridge would dangerously buckle and sway when it was windy. This led engineers to feel increasingly concerned about the safety of the bridge in the presence of stronger winds, and it was just then that they started to conduct experiments to study the bridge’s structural behaviour when it was exposed to high wind loads (although there was little to nothing they would have been able to do at that point).

The day that the bridge eventually collapsed, November 7th, 1940, the winds rose up to 19 meters per second (43.5 miles per hour), and the bridge’s structural integrity was critically compromised as a result of built-up torsional vibration amplitude, which caused the two opposite ends of the bridge to twist in opposite directions while the centre remained motionless. Once the vibrations reached this fatal frequency, many people were able to witness how cracks formed seconds before the bridge crashed down into the river, where it still remains as an artificial reef.

7. The Fukushima Daiichi nuclear disaster

The worst nuclear accident since Chernobyl and the only other nuclear event to be given Level 7 classification on the International Nuclear Event Scale, the Fukushima Daiichi nuclear disaster was, on the surface, caused by the Tohoku earthquake and resulting tsunami of 2011. The earthquake caused the nuclear plant's fission reactions to shut down, but because of design problems the electricity supply failed, meaning the reactors' cores failed to receive any coolant. Then the tsunami hit, a 14-metre-high wall of water sweeping over the plant's seawall and flooding four of the reactors, destroying the emergency generators.

The result of all of this was three nuclear meltdowns, three hydrogen explosions, and the release of masses radioactive contamination. Eventually, the evacuation radius spread to twenty kilometres, and over 150,000 residents were moved from an area of increasingly high radiation. Moreover, large quantities of contaminated water were released into the ocean, before finally a wall was created to prevent this from happening.

Although no increase in miscarriages, stillbirths, or illnesses in babies born after the accident have been found, it remains a devastating nuclear disaster that destroyed huge swathes of the environment and populated areas, with predictions that the cleanup effort will take between thirty and forty years. Over a year after the disaster, despite it seemingly having had occurred due to the tsunami, it was found that the plant operator was guilty of inadequately fulfilling safety requirements and failing to take the necessary precautions against such an event. Later in 2012, the operator - Tokyo Electric Power Company - finally admitted to have failed to take the necessary measures to prevent such a disaster. Seeing as such preventative safety measures are also the job of an engineer, this is certainly something that belongs on our list.