FORTRAN: The Programming Language That Never Retired

Elle
7 days ago
7 min read

Imagine if your smartphone still ran on the same software from the 1960s. Sounds impossible, right? Well, in the world of space exploration, NASA has been using a programming language called FORTRAN (short for "Formula Translation") since the early days of the space program, and they're still using it today. This isn't because NASA is stuck in the past; it's because FORTRAN has proven to be one of the most reliable and powerful tools for solving the complex mathematical problems that come with launching humans and robots into space.

What Exactly Is FORTRAN?

FORTRAN was born in the 1950s at IBM, making it one of the oldest programming languages still in use today. Think of it as the Latin of computer programming—ancient but foundational. Just as Latin gave birth to many modern languages like Spanish, French, and Italian, FORTRAN influenced countless programming languages that came after it.

What made FORTRAN special wasn't just its age, but its superpower: crunching numbers. While other programming languages were designed for general-purpose tasks, FORTRAN was built specifically for mathematical calculations. This made it perfect for scientists and engineers who needed to solve complex equations involving physics, chemistry, and engineering.

FORTRAN Takes Flight: The Apollo Era

When NASA began planning the Apollo missions in the 1960s, they faced an unprecedented challenge: how do you calculate the precise trajectory needed to send humans to the Moon and bring them safely home? The mathematics involved was staggering. Engineers needed to account for Earth's rotation, the Moon's gravity, the spacecraft's changing mass as it burned fuel, and countless other variables.

While the actual Apollo spacecraft used a different type of computer with its own special programming language (the Apollo Guidance Computer), the massive ground-based calculations that made the missions possible were largely performed using FORTRAN. NASA's engineers used FORTRAN programs running on room-sized IBM computers to simulate every aspect of the mission before astronauts ever left Earth.

These simulations were like incredibly detailed video games, except instead of entertainment, they were a matter of life and death. Engineers could test thousands of scenarios: What happens if an engine fails during launch? How much fuel do we need to correct course halfway to the Moon? What's the safest way to land on the lunar surface? All of these questions were answered using FORTRAN programs that could perform millions of calculations in hours. This was work that would have taken teams of mathematicians years to complete by hand.

The Shuttle Era: FORTRAN Matures

When NASA developed the Space Shuttle program in the 1970s and 1980s, FORTRAN evolved alongside it. By this time, the language had grown more sophisticated (FORTRAN 77 was the standard), and NASA's computers had become more powerful. The Shuttle program required even more complex calculations than Apollo because the shuttle was designed to be reusable and to perform many different types of missions.

FORTRAN programs calculated everything from the precise angle needed for atmospheric reentry (too steep and the shuttle would burn up; too shallow and it would bounce off the atmosphere back into space) to the optimal way to deploy satellites from the cargo bay. The language's ability to handle arrays of data—essentially tables of numbers—made it perfect for tracking the thousands of variables involved in each mission.

One of FORTRAN's biggest advantages became clear during this era: reliability. When you're dealing with human lives and billion-dollar spacecraft, you can't afford software bugs. FORTRAN's straightforward design and decades of testing made it incredibly stable. Engineers knew that a FORTRAN program that worked correctly today would work correctly tomorrow, next year, and even next decade.

The Modern Era: Why NASA Still Loves FORTRAN

You might wonder: if FORTRAN is so old, why doesn't NASA switch to something newer and fancier? The answer reveals one of the most important principles in aerospace engineering: "If it's not broken, don't fix it."

Modern NASA missions still rely heavily on FORTRAN for several critical reasons:

Legacy Code: NASA has accumulated millions of lines of FORTRAN code over the decades. These programs represent thousands of person-years of work by brilliant engineers and scientists. Rewriting all this code in a newer language would cost enormous amounts of time and money, and would introduce the risk of new bugs.

Mathematical Superiority: Despite its age, FORTRAN remains one of the best languages for mathematical computations. Its design allows it to perform complex calculations very efficiently, which is crucial when you're modeling the physics of spacecraft moving through the vacuum of space.

Proven Reliability: FORTRAN has been battle-tested in the most demanding environment possible: actual space missions. When the Voyager probes launched in 1977 to explore the outer solar system, they were supported by FORTRAN programs on Earth. Remarkably, those same Voyager spacecraft are still operating today—more than 45 years later—and NASA still uses FORTRAN-based systems to communicate with them.

FORTRAN in Today's Space Missions

Modern NASA missions showcase FORTRAN's continued importance in surprising ways:

Climate Modeling: NASA uses FORTRAN to run some of the world's most sophisticated climate models. These programs analyze vast amounts of data from Earth-observing satellites to help scientists understand climate change and predict future weather patterns.

Mars Exploration: When NASA plans missions to Mars, FORTRAN programs calculate the complex orbital mechanics needed to send spacecraft across the solar system. The same mathematical principles that got humans to the Moon in 1969 are still used to land rovers on Mars today.

Space Station Operations: The International Space Station relies on ground-based FORTRAN programs to calculate orbital mechanics, plan spacewalks, and coordinate the arrival and departure of cargo ships and crew capsules.

Deep Space Missions: NASA's FUN3D software, written in FORTRAN, helps design spacecraft that can efficiently travel through the thin atmospheres of other planets or the vacuum of interplanetary space.

The Human Side of FORTRAN

Here's where things get really interesting from a career perspective: NASA actively recruits programmers who know FORTRAN. In 2015, when one of the engineers responsible for the Voyager missions retired, NASA had to find someone who could understand and maintain 40-year-old FORTRAN code. This isn't just a historical curiosity—it's a real job requirement.

This creates a fascinating situation in the programming world. While most computer science students learn languages like Python, Java, or JavaScript, knowing FORTRAN can make you incredibly valuable to organizations like NASA, NOAA (National Oceanic and Atmospheric Administration), and other scientific institutions.

FORTRAN vs. Modern Languages

To understand why FORTRAN persists, it helps to compare it to languages you might be more familiar with:

Python is great for general programming and is easy to learn, but it's slower than FORTRAN for intensive mathematical calculations.

JavaScript powers websites and mobile apps, but it wasn't designed for the kind of numerical computing NASA needs.

C++ is powerful and fast, but it's more complex than FORTRAN for mathematical work.

FORTRAN sits in a sweet spot: it's fast, reliable, and specifically designed for the mathematical problems that dominate space exploration.

Challenges and Evolution

NASA doesn't just blindly stick with old FORTRAN code—they actively work to modernize it. The space agency regularly runs competitions challenging programmers to make existing FORTRAN code run faster and more efficiently. These contests attract top talent from universities and tech companies who enjoy the challenge of optimizing decades-old code for modern supercomputers.

The language itself continues to evolve. FORTRAN 2018 is the most recent standard, incorporating modern programming concepts while maintaining the mathematical focus that made the language famous. This ensures that new FORTRAN programs can take advantage of contemporary computer architectures while remaining compatible with older code.

Looking to the Future

As NASA plans missions to return humans to the Moon and eventually send them to Mars, FORTRAN will likely play a continuing role. The fundamental physics of spaceflight haven't changed since the Apollo era—spacecraft still need to overcome Earth's gravity, navigate through space, and land safely on other worlds.

However, NASA is also embracing newer technologies. Modern missions often combine FORTRAN programs for core calculations with newer languages for user interfaces, data visualization, and communication systems. This hybrid approach lets NASA leverage the reliability of FORTRAN while taking advantage of innovations in other areas of computing.

The Bigger Picture

NASA's continued use of FORTRAN teaches us several important lessons about technology and engineering:

Reliability Matters: In critical applications, proven technology often beats cutting-edge technology. When human lives are at stake, engineers prefer boring, reliable solutions over exciting, unproven ones.

Mathematics is Universal: The equations that describe planetary motion, orbital mechanics, and atmospheric dynamics are the same whether you write them in FORTRAN, Python, or any other language. FORTRAN just happens to be particularly good at solving them.

Legacy Has Value: Sometimes the old ways are old because they work. NASA's investment in FORTRAN code represents decades of accumulated knowledge and testing that would be extremely expensive to replace.

Specialization Pays: In a world where everyone learns the same popular programming languages, knowing a specialized but important language like FORTRAN can make you uniquely valuable.

The Language That Refuses to Die

FORTRAN's story at NASA is ultimately a story about the power of doing one thing really well. While flashier programming languages come and go, FORTRAN has survived because it excels at the mathematical computations that make space exploration possible.

The next time you see a NASA mission launch or read about a rover exploring Mars, remember that behind those incredible achievements are thousands of lines of FORTRAN code, quietly performing the calculations that make the impossible possible. In the fast-moving world of technology, sometimes the most remarkable thing is simply endurance.

As long as humans continue to explore space, there will likely be a place for FORTRAN in NASA's toolkit. It's a reminder that in engineering, the best solution isn't always the newest solution; sometimes it's the one that has proven itself time and time again, from the Moon to Mars and beyond.