Crashed spacecraft? Accounting errors? Blown gas pipelines? Check. Check. And Check.

Times may have changed, softwares may have become more complex requiring more effort from the developers, but the auto-correction tools have improved too. But what happens when some coding errors beat all corrective measures and the developers themselves, and end up being used as unintended? We have got some examples of such unintentional software errors which caused the most outrageous consequences and disasters.
NASA Mars Climate Orbit Spacecraft
The last place where you would expect a software mistake is NASA. OK! You would expect NASA to make some mistakes since it’s actually “rocket science”. But what we are reporting isn’t an error, it was a blunder.
In 1998, NASA launched a $125 million spacecraft towards Mars. It didn’t make it to Mars’ orbit and ended up being lost in space. The engineers couldn’t find the reason for quite some time. Finally, the issue was discovered and a sub-contractor on the engineering team forgot to convert English units to metric units (like inches to cm). The embarrassing mistake led the aircraft too close to Mars’ surface and while it did stabilize, the communications were crippled by the extreme forces and nobody knows what happened to it.
Ariane 5 Flight 501
Europe’s latest unmanned satellite rocket, Ariane 5, reused the software from its predecessor, the Ariane 4. The new rocket was using faster engines, but the rocket exploited a bug in the software which wasn’t seen in the previous model. The old software was based on 16-bit code from the A4 while the new data on the A5 rocket was using 64-bits, resulting in failures on both primary and backup computers. 36 seconds into the launch, the rocket engineers pushed the self-destruct button themselves.
The rocket cost $8 billion to build and was carrying a $500 million satellite. So much lost, all because they were saving money by using some old software code.
EDS Child Support System
The EDS system upgrade was one of the most expensive mistakes in UK. It introduced a complex IT system for UK’s Child Support Agency (CSA). During the same time, UK’s Department for Work and Pensions (DWP) was restructuring its own agency’s software. The two softwares developed for these agencies were made completely incompatible leading to irreversible errors.
The system caused huge losses before the fault and the incompatibility was discovered. It overpaid 1.9 million people and underpaid 700,000 people. $7 billion went to uncollected child support payments, 239,000 cases from before and 36,000 new cases got stuck in the system. Tax payments worth over $1 billion have been wasted because of the fault.
Soviet Gas Pipeline Explosion
The Soviet Union was building a complex gas pipeline network which required advanced automated control software and they planned to steal it from the US. The CIA was tipped off and they decided to work with a Canadian firm which developed the control software for the pipeline. They intentionally messed up the software so that the Russians would steal a fake program. In 1982, the flaws in the software led to a pipeline explosion causing the largest non-nuclear explosion on the planet.
Heathrow Terminal 5
Before the Heathrow Airport in London launched its Terminal 5, a new baggage handling system was built to carry large amounts of luggage. It was tested using 12,000 bags and worked without a problem. When the terminal opened, the luggage system failed. It couldn’t cope with people removing their luggage from the system, leading to mass confusion. It got shut down automatically.
The consequence? Some 42,000 bags were misplaced and 500 flights got cancelled.
Mariner 1 Spacecraft
Back in 1962, a spacecraft was launched to fly close to Venus. The spacecraft barely made it out of the launch town before the engineers discovered it was headed in the wrong direction and could crash back to earth. They self-destructed the spacecraft 5 minutes after its launch.
Later on, it was found that the software code missed a hyphen (-). Such an error cost the NASA/JPL $18 million in that day and age.
The Morris Worm
A student from Cornell University, Robert Morris, developed a program as part of a harmless experiment. The program wound being spread and crashed thousands of computers in 1988. The cause was a coding error.
This was the first widespread worm attack using the internet. Morris was fined $10,000 and convicted for criminal hacking. Costs for cleaning up the mess went as high as $100 million.
Patriot Missile Error
In February 1991, a US Patriot missile defence system failed to detect an attack on its Army Barracks in Saudi Arabia. It was later discovered by the government that the fault was present in the tracking software which got worse the longer it was functional. The day of the incident, the system was looking in the wrong place after only 200 hours of operation. 28 US soldiers were killed that day in the missile attack. The code was fixed and sent to the base the very next day.
Pentium FDIV bug
A math professor discovered a flaw in Intel’s Pentium processor and publicized it in 1994. Intel acknowledged the fault and was ready to replace chips upon request. The company calculated that the flaw would be very rare and most users won’t even notice it.
Their calculations were also wrong and the whole thing ended up costing Intel some $475 million.
Knight’s Software Error
Knight’s was one of the biggest American market makers for stocks but it struggled to stay relevant after a software bug caused a $440 million dollar loss in just 30 minutes. One of their algorithms went haywire and started making erratic trades, sending spasms on nearly 150 stocks. The firm lost 75 percent of its shares within the next two days.
Therac-25
Therac-23 was a radiation therapy machine produced by Atomic Energy of Canada in 1982. The machine was involved in six accidents between 1985 and 1987. During these accidents, patients were given massive overdoses of radiation. Programming errors caused patients to receive doses hundreds of times greater than what’s considered normal. Patients received “electric-like” shocks and were injured. Out of the eight injured, three eventually died as a result of the overdose.
So there you have it, 11 software mistakes that ended up causing a lot of pain and loss to people.