It’s Rocket Science – and it’s Dangerous!

Rockets have always fascinated us and to this day a rocket launch is still a global news event worth watching. The sheer noise, power and sight after you hear that “…3-2-1, Lift off!” leave us in awe. A masterpiece of engineering, the recent historic manned SpaceX Falcon 9 launch was no exception. Or was it?

The beginnings

From the outside, a rocket does not look especially advanced – a mere ‘stick’ with a big flame shooting out at one end. The principal concept is simple, too, but the inner workings of a modern liquid-fuel rocket are highly complex.

The first rockets are believed to have existed in China, around 1200. The invention of gunpowder was crucial to the development of these primitive rockets, which were fireworks initially and then weapons. Multistage so-called ‘fire arrows’ were documented during the early Ming Dynasty (Figure 1). The designs were based on bamboo sticks – still a little way off a Falcon 9.

Figure 1: The oldest known depiction of multistage rocket arrows, from 14th-century China. The top arrow reads ‘fire arrow’, the middle ‘dragon-shaped arrow frame’, and the bottom’complete fire arrow’. Source

With the rise of gunpowder, this crude rocket technology spread throughout the Middle East and Europe.

The next rocketry milestone came in the 1780s, when the Indian military developed Mysorean rockets with iron castings and successfully deployed them against the British East India Company.

Gunpowder-rocket artillery was widespread during the 19th century, but the designs still used solid fuel and were relatively low in power: basically, gunpowder combusting inside a tube.

The birth of the modern liquid-fuel rocket

Big leaps came in the early 20th century, when rocket pioneers with more peaceful intentions chased the dream of interplanetary travel. In 1914 American scientist Robert Goddard patented groundbreaking inventions, most notably the concept of a combustion chamber and the use of the De Laval nozzle to achieve supersonic exhaust speeds: the fuel was pushed into the combustion chamber from a pressurized tank.

To increase the power and range of a liquid-fueled rocket, the tank needed to be bigger and the fuel had to be fed into the combustion chamber at high rate and high pressure. Turbomachinery became involved and the 1930s and 1940s saw huge spending on rocket development in Europe in an arms race amid the looming conflict of World War II.

Nazi Germany made the biggest breakthrough, with the introduction of the turbopump by Wernher von Braun (who later designed the Saturn rocket engines for NASA). The V-2 became the world’s first long-range ballistic rocket. It could reach over 100 miles in altitude and a staggering speed of more than 3,500mph. It was the first human-made object to reach space in 1944. The modern liquid-fuel rocket was born.

German V-2 rocket engine
Figure 2: A German V-2 rocket engine featuring all the essentials of a modern liquid-fuel rocket, including a De Laval nozzle and turbopump feed. Source
Success, but at a cost

While the achievements in space travel in the 20th century are regarded as among the greatest engineering successes in human history, they came at a grave cost – the story of rocket science is also one of unimaginably high failure rates. And it is far from over.

The first three test launches of the V-2 rocket failed with devastating consequences. Turbopump failure and entire vehicle explosions were common – more common, in fact, than successful launches. It is estimated that the V-2 program had a failure rate as high as 80 percent. The chaos of war, perhaps…

Since World War II, minimizing failure rates has been the challenge. Vehicle losses in the civilian space age are unaffordable. Yet, failure rates remain high. The Space Shuttle program consisted of a fleet of five vehicles, two of which were lost during their 135 missions, resulting in 14 deaths. That is a 40 percent (!!) failure rate for the fleet and nearly 1.5 percent for all flights – orders of magnitude higher than predicted by NASA.

The last Space Shuttle flight was only in 2011. In 2019 there were 102 orbital launches worldwide, of which five failed. Yes, a near 5 percent global launch failure rate is the current measure. Trend stagnant!

Orbital Launch by Year
Source
The Digital Rocket Lab

So, what can we do to reduce these shocking numbers? Predictive engineering and testing are the two main pillars of any product development. By increasing deployment of the advances in predictive engineering, failure rates can be lowered and designs matured. Modern simulation methods and their automation can ensure every scenario is evaluated – from overall system behavior to detailed component behavior.

We work with our clients to explore these scenarios using state-of-the-art technology. The video below shows how we evaluate and optimize a turbopump design by running entire optimization loops that are fully inter-disciplinary, from flow path optimization to rotor dynamics and vibration analysis in one loop with our AxSTREAM.SPACE software bundle.

 

High Performance Computing gives insight into complex physics that were thought impossible. Supersonic rocket plumes are powerful, and you want to know what they are doing in all stages of flight. The video below shows a CFD simulation in the software STAR-CCM+ of a booster stage separation. Adaptive Mesh Refinement is deployed to achieve high resolution in the areas of moving shockwaves. As the shockwave moves, the mesh refinement moves, too, automatically.

 

Predictive engineering and modern computational methodologies (think AI) are becoming the test lab of the future, where big data drives design improvements. Ever-newer technologies are emerging fast, enabling insights that turn unknowns into knowledge.

Some people call it the Industry 4.0 and, just as the breakthroughs of Goddard and Von Braun made the rockets of today possible, the breakthroughs of the Industry 4.0 can make the near 0 percent failure rocket industry possible.

Impossible?

As Von Braun put it: “I have learned to use the word ‘impossible’ with the greatest of caution”.

How are you chasing 0 percent failure rates in your liquid rocket engine design? AxSTREAM.SPACE  and STAR-CCM+ can help you get there! Reach out to us at info@softinway.com to see how AxSTREAM  and STAR-CCM+ can be a critical part of your Digital Rocket Lab today!