The Stern: Did it implode or explode?

[Arun Vajpey]

There has been a lot of talk here and elsewhere about how the Titanic's stern section imploded under the pressure of the sea as it sank. But how much evidence is really there that it did so? To my untrained eye, the way the bits and pieces from the stern of the ship are scattered about suggests that there might have also been an explosive effect, perhaps as it hit the bottom.

This is the way I am looking at it. After the Titanic split into two and the bow sank beneath the surface of the Atlantic, the stern section remained afloat for a short time; I for one believe that this was for perhaps 40 to 50 seconds and not more. During that time, the sea would have been flooding the exposed deck spaces and would have continued to do so as the stern rose and then sank beneath the surface. As the rapid flooding continued, the air trapped in the as yet unflooded spaces at the very rear of the stern would have been compressed, even allowing for some of it being displaced and bubbled out through the open portholes etc. But the net effect would have been that the pressure differential between the sea outside and the inside of the flooding stern section would have been less than expected, thus delaying the implosive force. If that pressure differential remained not big enough to cause the expected implosion till the stern reached the ocean floor, could the eventual destructive effect have been an explosion due to the effect of the remaining compressed air?

 

[Kyle Naber]

I think most of the destruction to the stern was a result of water blasting through the stern, entering through the broken, exposed end. The pressure difference probably accelerated the fraying of of the debris as it crushed every weak segment and snapped pieces off.

 

[Arun Vajpey]

I am not an expert on shipwrecks but surely there must be other wrecks which lie as deep or deeper than the Titanic that show no signs of implosion? What about the German warship Rio Grande that lies at almost 19,000 feet depth? If a ship does not break-up before sinking like the Titanic did, that might men slower flooding and so more air trapped within as it sank. Under those circumstances, would not the effect of pressure of the ocean with increasing depth be far greater? So, if the Titanic really imploded between 500 and 2000 feet, why have not other deeper wrecks shown the same signs?

 

[Kyle Naber]

that might men slower flooding and so more air trapped within as it sank.

This is actually the complete opposite. If a ship sinks gradually, the air has time to escape. In Titanic’s case, the breakup accelerated the sinking by a considerable amount, meaning all the spaces in the stern that contained air (all of it) had to be emptied out within 40-50 seconds before water reached it (which was impossible). This caused the air to blast out through windows, doors, and decking, contributing to the giant rumbling noise as the stern slipped under.

Maybe the breakup and the escaping air weakened the stern section to a point where implosion became a much easier process, as the bow seems to have no signs of such damage, aside from what’s known as a “down blast effect.”

 

[Arun Vajpey]

Thanks, but what you are describing (the highlighted bit) sounds more like an explosion than an implosion. That was the point of my original question.

 

[Kyle Naber]

Ah. Yes, air would have been exploding out of the surface just before it went down. Probably when the stern descended 500 feet, the sea pressure crushed the rest of the air out and that’s when the fragments blew away from the stern (this includes the double bottom, shell plating, and a large section of tower debris).

 

[Arun Vajpey]

Probably when the stern descended 500 feet, the sea pressure crushed the rest of the air out

This is the part that I am questioning ie the physics of it.

There have been plenty of ships that have sunk relatively intact and at depths greater than 500 feet that show no signs of implosion. If a ship has not broken-up in the manner which the Titanic did, there would have been more air trapped inside (compared with the Titanic's broken off stern section) and since air is far more compressible than water, the pressure gradient between the outside and inside of the ship would have increased dramatically as the ship sank, thus creating a theoretical scenario for an implosion. Yet, most intact ships that have sank have not imploded because the trapped air was steadily displaced by flooding water, thus keeping the pressure gradient within the implosion point.

In case of the Titanic's stern, while admitting that it sank faster than intact ships, it was also flooding far more rapidly though the exposed deck spaces. The pressure gradient between the outside and inside therefore would have been a lot less than with an intact ship. At some stage, (probably 2000 to 3000 feet?) the sinking stern would have flooded completely and so the pressure gradient would have dropped to almost zero. So why would the stern implode under those conditions?

I can understand the stern section exploding if the rapid inrush for water during the sinking blasted the remaining oar through the open spaces further astern OR the compression effect as it hit the bottom forcing the uncompressible water out. But an implosion seems highly unlikely to me.

 

[mitfrc]

You know how when you almost cut through a piece of wood and then try to break it the rest of the way and the intact bottom fibres peel off instead of shattering? I actually think that's what started to happen to Titanic's stern. The strong double bottom held to the last as the ship progressively lost strength decks and then with the weight fully concentrated (a simple engineering problem), the double bottom failed. Four booms. But as the weight of the bow progressively concentrated on each deck, the lower ones bent more and more, shearing and buckling plate. Each time that happened, fatal damage worked it's way further aft. That's why the stern didn't float. The nature of the failure propagation worked the stern open. The stern didn't implode or explode in that model; catastrophically weakened it just collapsed more easily than the bow on impact with the bottom.

 

[Chung Rex]

In this case, even if the watertight doors at the aft were closed, the stern was doomed. What's more complicated, the water tank could have damaged and other heavy structures were detached, causing the stern to sink in somewhat pelicular and unpredictable way. In any cases, the crew and passengers still at the lower sections could have little time to react and were therefore never recovered.

Could it be said that the stern's fate is sealed because the double bottom is too strong?

 

[mitfrc]

In this case, even if the watertight doors at the aft were closed, the stern was doomed. What's more complicated, the water tank could have damaged and other heavy structures were detached, causing the stern to sink in somewhat pelicular and unpredictable way. In any cases, the crew and passengers still at the lower sections could have little time to react and were therefore never recovered.

Oh yes, there's an odd's-even chance it simply would have capsized (actually, better than odds-even based on precedent) if it hadn't sunk immediately. One might argue sinking was less likely than capsizing, however, which is why it is worth talking about.

Could it be said that the stern's fate is sealed because the double bottom is too strong?

No, the double bottom was as strong as it needed to be in the design. Not making any such suggestion. Rather, I was suggesting that the failure was inherent in how the ship sank -- that to get a different result, you need the ship to sink differently. For example, it's quite possible that if the ship had (just throwing out an easy one) violently blown in two that the stern might have capsized and then floated upside down for an hour before sinking. Specific developments have specific consequences -- in this case, the stern didn't float because it separated from the bow due to the specific way its structural strength was exceeded by slow progressive flooding from the bow to the stern, leading to a stress concentration point that caused crack initiation in the "virtual girder" of the hull.

To a lot of people this will all be very obvious... But a lot of obvious things do not seem so to many people, which is why so many competing theories march around.

 

[Arun Vajpey]

Thanks people but with respect, are we not a bit off topic here? Your reasoning about why the stern did not float is interesting but my original question was about several previous conjectures by members that as the stern sank, it imploded due to the pressure of water outside. My thinking is that the pressure gradient was not sufficient for that to happen because the stern was also flooding very rapidly as it sank.

 

[mitfrc]

I think it is germaine because I think that's why the stern didn't implode... I don't think that it had enough air in it to implode (a lot, i.e., the damage was from another cause than implosion).

 

[Mark Baber]

Thanks people but with respect, are we not a bit off topic here?

Please leave issues like this to the moderators to address, if they see fit. Thanks.