How the "Challenger" tragedy could have been avoided

The "Challenger" space shuttle disaster was attributed to an O‑ring failure on the SRB (solid-rocket booster). In fact, the O‑ring performed just as an O‑ring would be expected to perform under the circumstances. How, then, can an O‑ring, that performed normally, have caused the shuttle disaster?

The real problem was not the O‑ring but the extremely cold conditions at the launch site. Because of the freezing temperature the O‑ring was slowed in its expansion to its ideal cross-section. The O‑ring thus had insufficient time to seal the gap between the SRB tang and clevis and it was through this gap that the burning gases escaped, leading to the destruction of the shuttle.

So, the problem was not the O‑ring, itself, but rather that the O‑ring was frozen almost solid. If the O‑ring had been defrosted the flight would have been normal. Why didn't the technicians defrost it? Apparently, nobody thought of defrosting the O‑rings and, to this day, defrosting the O‑rings has never entered anyone's mind.

The disaster could have been prevented quite easily. All 12 O‑rings (there are two in each field joint and three field joints on each solid rocket booster) could have been defrosted within an hour. The equipment capable of doing the job was already on the launch site and had recently been used on "Challenger" for pressure-testing of the field joints.

When an SRB is assembled, the O‑rings are pressure-tested to be sure they have sealed. High-pressure air (nitrogen?) is injected into the annular space between the primary and secondary O‑rings. When the pressure is 100 psi (car tyre pressure 30 psi approx) the air supply is sealed off. If the pressure gauge connected between the O‑rings then shows the pressure to be dropping it indicates a seal is leaking. During the 38 days "Challenger" stood on the pad preparatory to launch, its field joints were periodically tested for leaks.
The test connections could have been used to defrost the frozen O‑rings.
All that needed to be done was replace the compressed air with warm air!
The only extra thing needed was for a small vent to be drilled in the annular gap diametrically opposite the air input. This vent is necessary to enable exhaust air to escape after having flowed freely around the annular space, defrosting the O‑rings as it passed by. The O‑rings could have been heated to whatever the launch directors wanted. The vent would also act as a drain-hole for water that sometimes seeped into the joint and would only need to be plugged when pressure testing.
pressure test
defrost O-rings
Graeme Lindridge © 2009