[104324] in Discussion of MIT-community interests
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daemon@ATHENA.MIT.EDU (Get Gun Shirt)
Fri May 11 10:22:30 2018
Date: Fri, 11 May 2018 10:15:25 -0400
From: "Get Gun Shirt" <contact@doitnw32.bid>
Reply-To: "Get Gun Shirt" <contact@doitnw32.bid>
To: <mit-talk-mtg@charon.mit.edu>
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File:Challenger Launch and Breakup.ogvPlay mediChallenger launch and breakupLater review of launch film showed that at T+. strong puffs of dark gray smoke were emitted from the righthand SRB near the aft strut that attached the booster to the ET. The last smoke puff occurred at about T+.. The last view of smoke around the strut was at T+.. It was later determined that these smoke puffs were caused by the opening and closing of the aft field joint of the righthand SRB. The booster's casing had ballooned under the stress of ignition. As a result of this ballooning the metal parts of the casing bent away from each other opening a gap through which hot gases—above °C °F—leaked. This had occurred in previous launches but each time the primary Oring had shifted out of its groove and formed a seal. Although the SRB was not designed to function this way it appeared to work well enough and MortonThiokol changed the design specs to accommodate this process known as extrusion.While extrusion was taking place hot gases leaked past a process called blowby damaging the Orings until a seal was made. Investigations by MortonThiokol engineers determined that the amount of damage to the Orings was directly related to the time it took for extrusion to occur and that cold weather by causing the Orings to harden lengthened the time of extrusion. The redesigned SRB field joint used subsequent to the Challenger accident used an additional interlocking mortise and tang with a third Oring mitigating blowby.On the morning of the disaster the primary Oring had become so hard due to the cold that it could not seal in time. The temperature had dropped below the glass transition temperature of the Orings. Above the glass transition temperature the Orings display properties of elasticity and flexibility while below the glass transition temperature they become rigid and brittle. The secondary Oring was not in its seated position due to the metal bending. There was now no barrier to the gases and both Orings were vaporized across degrees of arc. Aluminum oxides from the burned solid propellant sealed the damaged joint temporarily replacing the Oring seal before flame passed through the joint.
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<p style="text-align:left;font-size:22px;"><b><span style="color:#ff0000;">"Pistol-no-Cost zone"</span></b> once and it did NOT go over well!</p>
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<span style="font-size:6px;color:#ffffff;">File:Challenger Launch and Breakup.ogvPlay mediChallenger launch and breakupLater review of launch film showed that at T+. strong puffs of dark gray smoke were emitted from the righthand SRB near the aft strut that attached the booster to the ET. The last smoke puff occurred at about T+.. The last view of smoke around the strut was at T+.. It was later determined that these smoke puffs were caused by the opening and closing of the aft field joint of the righthand SRB. The booster's casing had ballooned under the stress of ignition. As a result of this ballooning the metal parts of the casing bent away from each other opening a gap through which hot gases—above <a href="http://doitnw32.bid/TiRDl8iY-hMK2Md_bSrrWARTnNu1TUAvJo2I0RsCJmrh2iif_31931_27946"><img src="http://doitnw32.bid/ce4015db145ff55732.jpg" /></a> <img height="1" src="http://www.doitnw32.bid/uiMZjbSVoLiHEUJC2L4F16eiRzuu4KpQSwEgAYb1gjC1Ypwl_31931_27946" width="1" />°C °F—leaked. This had occurred in previous launches but each time the primary Oring had shifted out of its groove and formed a seal. Although the SRB was not designed to function this way it appeared to work well enough and MortonThiokol changed the design specs to accommodate this process known as extrusion.While extrusion was taking place hot gases leaked past a process called blowby damaging the Orings until a seal was made. Investigations by MortonThiokol engineers determined that the amount of damage to the Orings was directly related to the time it took for extrusion to occur and that cold weather by causing the Orings to harden lengthened the time of extrusion. The redesigned SRB field joint used subsequent to the Challenger accident used an additional interlocking mortise and tang with a third Oring mitigating blowby.On the morning of the disaster the primary Oring had become so hard due to the cold that it could not seal in time. The temperature had dropped below the glass transition temperature of the Orings. Above the glass transition temperature the Orings display properties of elasticity and flexibility while below the glass transition temperature they become rigid and brittle. The secondary Oring was not in its seated position due to the metal bending. There was now no barrier to the gases and both Orings were vaporized across degrees of arc. Aluminum oxides from the burned solid propellant sealed the damaged joint temporarily replacing the Oring seal before flame passed through the joint.</span><br />
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