• Post category:Space Exploration
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In this article – we will cover briefly on what happened, causes, and learning.

Space Shuttle Challenger
Space Shuttle Challenger

Timeline:

T-6.6 seconds three main engines were ignited

T-0s the solid rocket boosters were ignited,
Immediately a puff of smoke is recorded at the field joint next to the attachment strut on the right-hand SRB

T+2 seconds, a piece of solid fuel from inside the booster moved inside the joint and provided a temporary seal against the blow-by, allowing the launch to proceed normally for around forty seconds.

Gray smoke escaping from the right-side Solid Rocket Booster (SRB)
Gray smoke escaping from the right-side Solid Rocket Booster (SRB)

T+36 seconds and an altitude of just over 10,000 feet (3,000 m), Challenger experienced the strongest wind shear ever felt during a Space Shuttle launch. The pitch and yaw commanded by the shuttle’s computers to counter this wind caused the solid fuel plug to become dislodged from the field joint on the right SRB.

T+58 seconds, Max-Q is achieved and simultaneously plume of hot gases is seen on the right SRB.

At around T+72, the right SRB pulled away from the aft strut attaching it to the external tank.

At T+73.124, the aft dome of the liquid hydrogen tank failed, producing a propulsive force that pushed the hydrogen tank into the liquid oxygen tank in the forward part of the external tank. At the same time, the right SRB rotated about the forward attach strut, and struck the intertank structure.
The breakup of the vehicle began at T+73.162 second.

The presence of O-rings
The presence of O-rings

The Details:

The Space shuttle carried 2 solid rocket boosters (SRBs). They each are made up of 4 segments and are bolted together to make one big long rocket motor. The segments have an O-ring – a type of gasket to keep hot exhaust gasses from leaking out.

In the extremely cold weather at the time of launch, one of the gaskets, shrunk. This allowed hot gas to begin leaking out of the joint. The SRBs are held on either side of the big fuel tank by metal struts. The hot gasses melted through one of the struts and suddenly the solid rocket booster was only attached at the front. It swiveled around (too quickly to see on the videotape) and the pointy front end punched a hole in the tank. This caused the big fuel tank, which was full of liquid oxygen and liquid hydrogen fuel, to come apart at the seams under the high-speed wind.

Space-Shuttle-Challenger Disaster cross section
Simplified cross section of the joints between rocket segments SRB outside to left. Legend: A – steel wall 0.5 inches (12.7 mm) thick B – base O-ring gasket, C – backup O-ring gasket, D – Strengthening-Cover band, E – insulation, F – insulation, G – carpeting, H – sealing paste, I – fixed propellant

The solid rocket boosters, now free-flying and not under anyone’s control, continued onward in random directions. A few moments later, the Range Safety Officer on the ground radioed a self-destruct command to the boosters, so that they wouldn’t become dangerous to the crowds of people watching. They exploded harmlessly and the pieces dropped into the ocean.

The horrifying thing is that they found out later that at least some of the astronauts were alive and conscious after the explosion. Some of the emergency air supplies were turned on. That couldn’t have happened by accident. So they were alive and knew that the shuttle had exploded, but couldn’t do anything at all, but wait to crash into the ocean at hundreds of miles per hour and die.

Engineers, Managers and Decisions!

Prove that this particular device will fail to work.
Prove that this particular device will not fail to work.

Well, from a managerial perspective, both these statements sound similar – to know whether to use the device or not in a larger system. But from an engineering perspective, the statements are not only completely different on how it can be proven but has completely different ramifications too.
A device may fail to work in 1 out of 100 chances, and a sound engineer will know that. But, the problem is when asked from a management team to prove that it will fail, the scenario becomes utterly miserable to be executed
Well, this was the scenario with Space Shuttle Challenger Disaster. The engineering team had warned the management of the impact of cold weather on the O-ring and had recommended not to launch. But . . .

Learnings and after-math

In those days, they didn’t have parachutes or any way to bail out. They only wore partial spacesuits. After the accident, NASA redesigned their spacesuits to allow them to bail out, and added parachutes and an extendable pole to allow them to get away from the vehicle. This might have helped if they had had it at the time, although that isn’t a certain thing. Many people say they wouldn’t have been able to get away from the spinning, jagged wreckage in time to deploy their parachutes. Challenger’s explosion changed the space shuttle program in several ways. Plans to fly civilians in space (such as teachers or journalists) were shelved for the next 22 years, until Barbara Morgan, who was McAuliffe’s backup, flew aboard Endeavour in 2007. Satellite launches were shifted from the shuttle to reusable rockets. Additionally, astronauts were pulled off duties such as repairing satellites, and the Manned Maneuvering Unit was not flown again, to better preserve astronaut safety.

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