Spacecraft failures II
Mars Climate Orbiter, Challenger and Columbia disasters, Proton-M
In the first part of this article, we leaned into some of the failures of space vehicles. In this part, we will look at four more failures and briefly talk about how they can be detected and, consequently, even avoided.
Mars Climate Orbiter
Do you happen to make mistakes when converting units from two different systems? That’s what the engineers working on the Mars Climate Orbiter, a robotic space probe launched in 1998 by NASA to study the Martian climate, did. It was due to enter orbit in September 1999.
During the flight to Mars, a trajectory correction manoeuvre put the spacecraft in a position that deviated from what was intended, but no one considered this to be a big problem, the trajectory still allegedly allowed the orbiter to enter Martian orbit at a survivable altitude.
After the failure, it turned out that the calculations taking into account the erroneous manoeuvre were underestimated and the actual orbit altitude was lower. During the insertion, contact with the orbiter was lost as it passed behind the planet, but contact was never re-established.
As it turned out, one of the key programs calculating thruster firing pulses was giving results in US customary units, while another system was expecting a date in SI units. This resulted in an erroneous prediction of the spacecraft’s position and, ultimately, its destruction in the atmosphere due to entering the atmosphere too quickly and too low, where aerodynamic drag was already playing a large role.
Challenger and Columbia disasters
These two disasters are among the saddest, as fourteen people lost their lives in those accidents.
The Challenger disaster took place in February 1986. As you may know, the entire Space Transportation System consisted of an orbiter, a liquid fuel and oxydizer tank and two solid rocket boosters. Everything in the space industry has its own operating conditions; this means that the engineers are sure that the device works properly under these conditions. One of the conditions, important for this case, was the ambient temperature. The morning of the flight was cold; so cold that the temperature was outside the operating window of the side boosters, which were manufactured by Thiakol. Engineers from the manufacturing company did not want to launch, but NASA was pushing (for political reasons) so they said they were 'ready’ to launch. Unfortunately, their fears came true as one of the boosters disintegrated in flight, later destroying the orbiter and killing the entire crew.
After an investigation by a committee, in which the famous physicist Richard Feynman played a major role, it came to light that one of the O-rings connecting the different segments of the solid rocket booster (SRB) had failed due to the low temperature, unable to expand and seal the segments as effectively in the cold as under standard conditions. Because of this failure, some of the hot exhaust gases were leaking through the side of the SRB; the hole expanded and enlarged as the vehicle continued to fly. Suddenly, the strut attaching the booster to the external fuel tank and the booster rotated and crashed into the fuel tank, causing an explosion.
In later flights of the space shuttle, the rubber O-ring system was redesigned, providing a more effective seal between segments. In addition, procedures were changed to ensure that the accident would not happen again, with the committee suggesting improved communication between management and engineers. Furthermore, a new advisory panel and safety office were created.
In 2003, the Columbia disaster occurred. During liftoff, a piece of insulation foam detached from the external fuel tank and damaged the Space Shuttle’s left wing leading edge thermal protection system.
Initial assessment of the damage while still in orbit determined that the damage was not significant and should not be of major concern. The foam impact was compared to impacts on previous missions where nothing serious had happened and simulations tended to overestimate the damage. Unfortunately, as it turned out, the damage was severe and those raising concerns were correct. After the mission, during re-entry into the Earth’s atmosphere, hot gases began to penetrate the heat shield and subsequently melted the internal aluminium structure of the wing. This caused debris to be shed from orbiter and later disintegrate over the continental United States.
These two fatal accidents were among the many reasons why the Space Shuttle programme was terminated in 2011 – there was no way for the crew to escape if something happened. Subsequent vehicles that NASA uses to transport crew and further into orbit (SpaceX’s Dragon, Boeing’s Starliner and NASA’s Orion) all have crew escape systems that can separate the spacecraft from the rocket. However, SpaceX’s upcoming Starship does not have any escape system, other than the second stage itself, which is not planned to be refuelled to full capacity, so it can launch from the top of the first stage in flight if necessary.
Proton-M launch failure
Proton is a Russian rocket that regularly launches satellites and payloads into orbit. The launch that took place in 2013 was one of them, as Proton carried three navigation satellites. As soon as the rocket lifted off from the Baikonur cosmodrome, it could be seen swinging off course and wobbling right and left. A few seconds later, it turned almost upside down and flew towards the ground. The forces exerted on the rocket by the drag force shattered the structure and the vehicle disintegrated while still in the air. More than seven hundred tonnes crashed to the ground, toxic hypergolic fuel spilled everywhere, even some windows in nearby buildings were shattered. To this day, satellite images show the crater where it crashed.
This is a failure that could easily have been prevented by proper inspection of the assembled rocket. After investigation, it turned out that all three internal measurement units (IMUs) for the yaw axis were installed incorrectly – they were installed upside down. And that’s not even the best part – it wasn’t just a mistake – their shape was designed to prevent incorrect installation – they were hammered in, potentially with a simple hammer; what’s more, there was an arrow on them indicating the correct direction of flight. Unsurprisingly, according to the quality inspector, everything was fine.
And, of course, everything was signed off as ready to fly. Could this have been prevented? Easily – with a proper inspection and test of the readings on the tarmac – the IMUs must have shown that the rocket was pointing downwards – which was certainly not the case while waiting on the launch pad for launch. Why did no one react? Was it a simple oversight? Probably yes, someone didn’t notice, but the software didn’t react either.
How to detect any issues?
In the past, detecting any damage or malfunctioning parts or software was very difficult. But today, as the size of electronic systems continues to shrink and the computing power of the onboard computer increases, trying to detect any problems with the spacecraft is much easier.
One such system is Scanway’s proprietary technology called SHS– Spacecraft Health Scanner. This is a system designed to detect any damage to the observed part/system.
It works on the basis of artificial intelligence and machine learning. The system is constantly fed with data from multiple sensors while the satellite is operating. When an anomaly occurs, it is able to automatically detect it and inform the customer.
One of SHS configurations is the VIBE – Vision Inspection Boom Experiment, a deployable boom that extends from the spacecraft. It allows engineers to mount a camera on the boom that can observe various parts of the spacecraft, such as solar arrays or engine bells. The system continuously analyses the components under observation, so that when damage occurs, it immediately sends out a warning signal.
One of the advantages of the SHS is its small size, ease of integration into the spacecraft and customisability. If you want to know more about SHS system – please feel free to contact us via e-mail [email protected].