A while ago, a Vega rocket from Europe, which was carrying a satellite made in Spain, was about to let go of its top section when cable went terribly wrong. What led to the rocket’s failure? Why does the type of cable used matter so much? And what lessons does this error provide for engineers working on similar projects?
How Poor Cable Choice Led to a Rocket’s Failure
At the stroke of midnight, a Vega rocket was all set for takeoff from a spaceport in South America. Its mission was to launch SEOSat-Ingenio, Spain’s first-ever satellite capable of capturing high-resolution images of Earth. This satellite was expected to operate for 7 years, helping in tasks like monitoring disasters.
But things didn’t go as planned. The satellite’s mission ended in just over 7 minutes. During the final stage of the launch, the rocket’s control computer was instructing the thruster to move in one direction, but the rocket was spinning the other way. Soon after, the rocket fell back into Earth’s atmosphere, and the satellite was destroyed. The debris ended up scattered across the Atlantic Ocean.
Rocket failures due to seemingly minor issues have happened before. For instance, a Russian rocket failed because its internal orientation sensors were installed upside down, causing the rocket to think it was flipped. The Vega rocket’s failure was also due to a simple mistake that might surprise many: a pair of cables connecting the thruster controls and the main controller were installed in reverse! So, any command to move the thruster resulted in the opposite movement.
This raises some questions. If a cable has a specific direction, why didn’t the system designers use a cable that also had a specific direction? Cable connectors are quite inexpensive, and choosing a cable that can only be installed one way seems like the logical choice. And how did the system checks fail to notice that the thruster was moving in the opposite direction of the intended motion? It’s a mystery.
Why does the choice of cable matter so much?
Not long ago, a Vega rocket from Europe was set to launch a Spanish satellite into space. But things went wrong during the separation of the upper-stage. The question is, what caused the rocket to fail, why is the choice of cable so crucial, and what lessons can engineers learn from this incident?
Here’s the story of how a rocket failed due to a poor choice of cable:
Just after midnight, a Vega rocket was ready for launch from a spaceport in South America. It was carrying SEOSat-Ingenio, Spain’s first satellite for capturing high-resolution images of Earth. The satellite was expected to work for 7 years, helping with tasks like monitoring disasters.
But the mission ended in just over 7 minutes. During the final stage of the launch, the rocket’s control computer was instructing the thruster to move in one direction, but the rocket was spinning the other way. The rocket soon fell back into Earth’s atmosphere, and the satellite was destroyed. Its debris ended up in the Atlantic Ocean.
Rocket failures due to minor issues have happened before. For example, a Russian rocket failed because its orientation sensors were installed upside down, causing the rocket to think it was flipped. The Vega rocket’s failure was also due to a simple mistake: a pair of cables connecting the thruster controls and the main controller were installed in reverse! So, any command to move the thruster resulted in the opposite movement.
This brings up some questions. If a cable has a specific direction, why didn’t the system designers use a cable that also had a specific direction? Cable connectors are quite cheap, and it seems logical to choose a cable that can only be installed one way. And how did the system checks fail to notice that the thruster was moving in the opposite direction of the intended motion?
Why is the choice of cable so crucial?
Choosing the right cable for a job is very important, as the Vega rocket incident shows. But there are many factors to consider when choosing cables for a design, including voltage, current, electromagnetic interference (EMI), temperature, and mechanical stress.
The first step in choosing a cable is to understand the environment it will be in. Will it be corrosive? Will it experience wide temperature swings? Will it be under mechanical stress? Based on these factors, you can decide on the type of cable. For example, cables in extreme temperature environments may need thick insulation. In contrast, environments with vibrations may need multi-stranded cables to prevent breakage.
The second step is to understand the signal type and its requirements. For example, if the cable is being used to transmit USB data, it may need a twisted pair to improve noise performance. If the cable is exposed to stray electromagnetic radiation (EMI), it may need to be shielded. Cables expected to carry large amounts of data should be kept short, and cables with a specific direction should use a cable and connector that can only be installed one way.
The third step is to understand the electrical requirements of the signals and choose a cable to match. However, a good rule of thumb in engineering is to double the requirements to account for variations and potential future upgrades. For example, a cable expected to carry 100V should be chosen to carry 200V. When considering electrical characteristics, cables should be devalued when used in environments that can affect their performance, such as ambient temperature and the cable’s ability to dissipate heat.
What lessons can engineers learn from this error?
While the Vega rocket mishap underscores the significance of choosing the right cable, it’s even more concerning that a crucial system like the rocket thruster correction could function in reverse. It’s reasonable to assume that when each stage of the rocket is constructed, software diagnostics could be used to verify how the hardware will perform. Although the rocket itself can’t be tested by igniting fuel, the vector control system can certainly be operated and inspected.
The most significant error an engineer could make from this incident is to merely add a new item to a pre-flight checklist. The real takeaway here is that simple mistakes can occur. Therefore, diagnostic and testing systems should be capable of providing both physical and simulated sensory data to verify the rocket’s correct response. For instance, the upper stage could be easily suspended in a facility, given altitude data, and observed to see which direction it attempts to point the thruster. This kind of test would also show how the entire control system will react; it’s not a simulation, but the actual outcome when given real data.
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