Orbital rocket technology has come a long way since the early years of the Space Race between the United States and the former Soviet Union. Yet, occasionally, they still explode into a spectacular fireball during launch.
Rockets can explode during launch primarily due to a structural failure or technical malfunction, causing the fuel, which makes up more than 85% of the vehicle’s mass, to combust and destroy the rocket. The stresses rockets are subjected to during launch play a significant role in these failures.
Rockets are complex vehicles that consist of thousands of moving parts, each designed by some of the most highly qualified engineers on the planet.
Not only do they need to travel at hypersonic speeds to escape Earth’s gravity, but they also need to withstand the extreme pressures exerted on their structures by Earth’s gravity and atmosphere. On top of this, they also have to survive the unforgiving rigors of space.
As a result, it would almost be easier to debate why a rocket survives a launch and successfully reaches space at all. As discussed in the following section, though, a few factors are involved in the manufacturing and launch of rockets that make them especially susceptible to failure.
Why Rockets Are So Prone To Exploding
There seems to be almost an infinite number of factors involved in the design, manufacturing, and launch of a rocket. However, a few key factors play an especially significant part in the potential failure and subsequent explosion of a launch vehicle:
- Fuel
- Materials Used
- Stressors On The Vehicle
- The Human Factor
Fuel
More than 80% of a rocket’s mass consists of highly combustible fuel, either in liquid or solid form. (The Saturn 5 rocket that carried astronauts to the moon consisted of 85% fuel by mass, while the Russian Soyuz rocket consisted of 91% fuel.)
The rocket fuel is combusted in gaseous form to produce thrust during launch. If any kind of malfunction occurs that compromises the structure of the rocket, it usually results in the fuel tanks failing, leading to all the rocket fuel spontaneously combusting.
Since such a large portion of the vehicle consists of fuel, it is easy to understand why the damage is total, and the whole rocket is destroyed in case of a serious failure.
(Learn more about the different fuel types orbital rockets use, their characteristics, as well as the advantages and drawbacks of each fuel in this article.)
Materials Used
The material used in the construction of a rocket has to be both strong enough to hold the vehicle together and withstand the stressors on the structure while also being light enough to help the rocket escape Earth’s gravity.
The structure of a rocket typically consists of aerospace-grade titanium or aluminum, while various other materials like rubber, polyurethane foam, and carbon are also used in different components, joints, and surfaces.
Sometimes, a compromise has to be made between the weight and strength of a material during the manufacturing process. The smallest miscalculation, combined with weaknesses and imperfections in the material, can lead to failure with catastrophic results.
(Learn more about the different types of materials used to produce an orbital rocket, specifically its structural, propulsion, and payload system, in this article.)
Stressors On The Vehicle
As mentioned during the introduction, a rocket experiences immense pressure from a variety of forces during launch. The main forces at play are the Earth’s gravity, thrust from the rocket engines, and atmospheric conditions like drag and lift.
If any part of a rocket is unable to withstand any one of these forces on its structure (due to material defects or weaknesses, navigational error, environmental factors. etc.), it can break up, resulting in catastrophic failure.
The Human Factor
As with any other manufactured product or component, rockets are also at the mercy of human decision-making and error. And on more than one occasion, as will be illustrated later in this article, this led to the destruction of rockets and the loss of life in the past.
More reliable computer systems have taken over many critical manufacturing processes and decision-making during rocket launch procedures, but for the foreseeable future, it will be impossible to cut out the human factor completely.
This is by no means an exhaustive list of all the factors that may lead to a rocket’s failure but it highlights some of the key factors contributing to rockets exploding unexpectedly during and after launch.
Examples Of Rocket Failures During Launch
The best way to illustrate why and how rockets fail and explode and how some of the factors mentioned in the previous section come into play is by using examples of actual rockets that exploded in recent history:
- Space Shuttle Challenger (1986)
- Ariane 5 (1996)
- Delta II (1997)
- Antares (2014)
- SpaceX Falcon 9 (2016)
Space Shuttle Challenger (1986)
On January 28, 1986, one of the worst and probably most tragic rocket explosions occurred in the history of space exploration. 37 Seconds after launch, the Space Shuttle Challenger exploded and broke apart, destroying the vehicle and all seven astronauts on board.
What makes this tragedy even worse is that it was entirely preventable. A weakness in the O-rings of the solid rocket boosters was discovered after examinations of recovered boosters from previous launches on numerous occasions.
It was determined that the rubber used in these components didn’t perform as it should in cold temperatures, and the alarm was raised long before the fateful launch on January 28.
Engineers from Morton-Thiokol (manufacturer of the solid rocket boosters) recommended that no space shuttle launch should take place if temperatures were below 53 °F (12 °C).
On the morning of the launch, temperatures were below freezing at the launchpad, and engineers from Morton-Thiokol argued that the launch should not take place. Despite their opposition, the decision was made to proceed with the launch anyway.
At approximately 58 seconds into the flight, the engineers’ worst fears were confirmed when a plume of white smoke was detected on the right solid rocket booster where the problematic seal failed to seal the joint, which was supposed to keep the hot gases inside.
This set off a chain reaction, which resulted in the main fuel tank exploding and breaking the shuttle apart. The two solid rocket boosters continued traveling haphazardly forward for a while before mission control initiated the self-destruct sequence.
This very preventable incident was a combination of both defective materials and human negligence. You can read the full story about the Challenger Disaster here.
Ariane 5 (1996)
On June 4, 1996, an Ariane 5 rocket exploded 37 seconds after launch over the coast of French Guiana in an impressive ball of fire after rapidly turning at a 90º angle in the wrong direction. This maneuver activated the self-destruct mechanism, which destroyed the rocket.
The cause of the accident was determined to be a software problem. The system that determines the vehicle’s orientation (known informally as a BH value) was unable to convert the incoming data fast enough, essentially resulting in an overload, causing the malfunction.
Essentially, the explosion was a result of human error since the programmers were basically trying to feed a 64-bit value (which may hold several billion different values) through a 16-bit integer (only capable of handling a maximum of approximately 65K values).
Delta II (1997)
On 17 January 1997, a Delta II rocket failed only 13 seconds after liftoff at Cape Canaveral. Although no one was killed in the explosion, 250 tons of debris fell on and around the launchpad, destroying 20 cars in a parking lot and damaging several buildings.
A crack in one of the solid rocket boosters turned out to be the culprit. After rupturing, it destroyed an adjacent booster, which activated the self-destruct mechanism, destroying the rest of the rocket.
In light of the possible factors responsible for rocket failures mentioned in the previous section, one can deduce that a material defect was ultimately responsible for the incident.
Antares (2014)
Orbital Sciences’ Antares rocket suffered a similar fate when it experienced a catastrophic failure only 15 seconds after launch on October 28, 2014, at NASA’s Wallops Facility in Virginia, United States.
Friction between turbopumps in the rocket’s engine resulted in a fire, which caused the rocket to lose thrust. It plummeted back to the surface, where it exploded on impact, destroying the whole vehicle and payload.
Investigations by NASA and Orbital Science concluded that a material defect during the manufacturing process likely caused the events that resulted in the explosion.
SpaceX Falcon 9 (2016)
Sometimes, a rocket does not even need to be launched to explode. In September 2016, a SpaceX Falcon spontaneously combusted while standing on the launchpad, carrying a $200 million satellite as payload. The explosion destroyed both the rocket and the satellite.
An investigation into the incident revealed that a helium-containing pressure vessel ruptured in the rocket’s upper-stage oxygen tank. It is unclear why this occurred, which may indicate that the process involved a range of different factors, including defective materials.
(Learn more about why rockets need to carry oxygen on board in addition to fuel by reading the full article here.)
These are just a few examples of rocket explosions that got more media exposure and grabbed the public’s attention. For each of these failures, there are hundreds of other less documented explosions that occurred during testing and flights with actual commercial/government payloads.
Conclusion
Rockets are a mix of highly complex machinery, components, and materials that somehow have to work together to launch several hundred metric tons (or more) of launch vehicle and highly combustible fuel fast enough into the atmosphere to escape the Earth’s atmosphere.
It is, therefore, quite surprising that modern rockets have such a high success rate. Unfortunately, most rocket launches only get noticed by the media and public when they fail and end up in a spectacular massive fireball display.
This, inevitably, also led to questions regarding the safety of space flight for human beings. (You can learn more about rocket safety for crewed spaceflights in this article.)
This article illustrated the many factors that can come into play and contribute to a rocket’s failure and consequent explosion. It also highlighted some of the more prominent examples in recent history that illustrated how these factors impact rocket launches in practice.
This article was originally published on headedforspace.com. If it is now published on any other site, it was done without permission from the copyright owner.
