Are Rockets Safe?

As space agencies like NASA look to return astronauts to the Moon with its Artemis Program, and SpaceX is aiming for Mars with its Starship, more public focus is returning to space exploration, specifically rocket safety.

Rockets used for space exploration can generally be considered relatively safe, with a statistical fatality rate of 3.2 percent. However, it remains a dangerous endeavor compared to civil aviation, with a fatality rate of only 0.03 percent, measured in fatalities per billion kilometers traveled.

In 2019, NASA recommitted itself to returning to the moon by 2024 with its Artemis program (under then President Donald Trump’s directive.) Meanwhile, China is pressing ahead and making progress with its Lunar Exploration Program, also known as the Chang’e Project.

Why Rockets Are So Unsafe

Rocket safety has come a long way since the early days of attempting to get humans into space and landing on the Moon in the 1960s and 70s. Yet, the fundamentals of rocket design and operation and the dangers associated with them haven’t changed much since.

There are numerous variables involved in making a rocket launch and ascent dangerous, but 4 key factors play a more significant role in making these launch vehicles that much more dangerous and prone to failure:

1. Fuel Amount And Type
2. Types of Materials Used
3. Dynamic Forces On The Vehicle
4. Human Error

1) Fuel Amount And Type

More than 80% of a rocket’s mass consists of highly combustible fuel, either in liquid or solid form. (The Saturn 5 rocket used during the Apollo missions consisted of 85% fuel by mass, while the Russian Soyuz rocket consists of 91% fuel.)

The 3 types of liquid propellant typically used in rockets are:

• RP-1 (A highly refined form of kerosene)
• Liquid Hydrogen LH₂)
• Methane (LNG or Liquid Natural Gas)

These rocket fuels are already combusted in gaseous form to produce thrust during launch. If any malfunction occurs that compromises the rocket’s structure, it usually results in the fuel tanks failing, leading to all the rocket fuel spontaneously combusting.

Since such a large portion of the vehicle consist of fuel, it is easy to understand why the damage is total, and the whole rocket is destroyed in case of a serious failure.

2) Types of Materials Used

The materials used in the construction of a rocket have to be strong enough to hold the vehicle together during launch and withstand the dynamic forces on the structure during ascend while also being light enough to help the rocket escape Earth’s gravity.

A rocket’s structure 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.

Often, a compromise has to be made between the weight and strength of materials during the manufacturing process. The smallest miscalculation, combined with any weaknesses or imperfections in the material, can lead to failure with catastrophic results.

(Learn more about the different materials used in the construction of an orbital rocket in the following in-depth article.)

3) Dynamic Forces On The Vehicle

A rocket experiences extreme pressures 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 a rocket is unable to withstand any one of these forces on its structure, it can break up, causing the vehicle to fail and explode.

4) Human Error And Decision Making

Rockets are also at the mercy of human decision-making and error. And on more than one occasion, this led to the destruction of rockets and the loss of life. The Space Shuttle Challenger disaster in 1986 & Columbia in 2003 are two examples of bad decision-making.

In 1986, the space shuttle Challenger exploded, destroying the vehicle and all 7 astronauts. A weakness in the O-rings of the solid rocket boosters was discovered after numerous examinations of recovered boosters from previous launches, but it was ignored.

More accurate and reliable computer systems have taken over 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.

By no means is this 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 the dangers of space travel.

Safety Measures For Rockets: Past & Present

Although it is clear that spaceflight with orbital rockets will always be risky and relatively dangerous, new technological advancements and improved procedures ensure that the safety of current and future spaceflights are constantly improving.

Crew safety was always at the forefront of rocket development as early as the Apollo Program in the 1960s and early 70s. A combination of new developments and learning from failed missions/disasters resulted in further improvements in astronaut safety:

Launch Abort/Escape Systems (LAS / LES)

All Saturn 5 rockets used during the Apollo Missions were equipped with a Launch Escape System (LES), which consisted of solid rocket boosters housed in a tower at the front of the crew capsule.

These boosters would propel the capsule away from the rest of the rocket in case of an explosion or any other kind of emergency that required the crew to be ejected to safety. Once cleared, parachutes were deployed to take the astronauts back to the surface safely.

Even private companies like Blue Origin use a launch escape system on their New Shephard rockets that will take civilian customers to the edge of space and back.

Weather Requirements

One aspect of a planned rocket launch that is completely beyond the control of anyone involved is the weather. As a result, NASA, SpaceX, the ESA, and other space agencies have a strict set of weather criteria that has to be met before any launch can take place.

There are 3 types of weather conditions that are of specific danger to rockets during launch:

• Wind
• Lightning
• Vertical Cloud Buildup Combined With Icy Conditions

Winds above a certain velocity at the launch tower can influence the rocket’s navigation. Strong upper atmospheric winds pose a similar threat but can also damage the launch vehicle’s structure and destroy a rocket flying into it at supersonic speeds.

Lightning poses a serious threat to a rocket’s sensitive electronic equipment and can endanger the crew onboard. In a highly charged environment, rockets are also capable of producing lightning themselves.

Clouds with a high vertical buildup, like cumulonimbus clouds, have an increased likelihood of high winds and lighting occurring. But it can also extend into freezing temperatures, where ice can pose a real threat to vehicle safety.

(As an example, NASA has a specific set of weather criteria that must be met before a SpaceX Falcon 9 rocket can be launched, which can be found here.)

Depressurisation / Asphyxiation Prevention

In 1971, disaster struck when three cosmonauts returned on Soyuz 11 from Salyut 1, the Soviet Union’s first space station. After reentry and a “safe” landing, recovery crews were horrified to find all three cosmonauts unresponsive inside the capsule.

Investigations into the incident discovered that they died as a result of asphyxiation after a valve malfunctioned during separation between the descent and service modules, causing the capsule to depressurize.

Since this incident, all cosmonauts are required to wear a fully pressurized suit (Sokol IVA suit) during the launch and reentry of all crewed space flights.

From 1994 until the end of the Space Shuttle Program, NASA also used fully pressurized suits (known as ACES or “pumpkin suits”) on all its remaining flights. Crew members of SpaceX’s Crew Dragon module also wear fully pressurized spacesuits.

Conclusion

As this article clearly illustrated, spaceflight as we know it will never be considered safe. The very nature of rockets and the dangers associated with a launch means that every liftoff of a rocket is a calculated risk.

All astronauts understand this danger, and everyone involved is very aware of the fact that every rocket launch is a delicate balancing act, where the pros and cons of every possible factor and variable have to be weighed up against each other.

(To learn more about why rockets seem so prone to failure and explode with alarm frequency, read the following article.)

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