Optimal speed to avoid collision


William Oakes

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If this has been asked before, please forgive my question.
I have seen many computer models that calculate flooding and sinking, and break-up.
Has anyone ever done a computer simulation/model to calculate the top speed Titanic could travel at, and still have time once the berg was sited, to make the hard to starboard turn and completely miss the iceberg?
We have Carpathia comining in at 15-18 knots, depending upon which account/testimony that you believe.
But an Olympic class ship like Titanic is much larger and faster.
So how fast can Titanic travel and still navigate around the iceberg?
I would be interested in knowing this.
 
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There were probably tank tests done to see which hull form would work out best but I'm not aware of any first hand evidence to back it up. The know how to do that had been around for at least half a century although I don't know how often it was used for commercial designs.

The Olympic class was designed to provide a reliable weekly service with three ships, and in order for that to work, they had to be at least 21 knot ships, which in fact they were.

If memory serves, at one point in her career, aided by currents and a following sea, the Olympic briefly achieved something in the range of 26 knots. Mark Chirnside found that information so if he's hanging around, I'll be interested in his insights on this question.
 
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Thomas Krom

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Good day to you gentlemen,



The Olympic had a maximum speed in 1911 of 23.01 knots, while the average serving speed as Mr. Standart mentioned was 21 knots. If you believe that the Titanic had a three bladed centre propeller, which I personally do, the maximum speed of the Titanic was extended by 0.38 knots, making her maximum speed 23.39 knots.


The speed of the Titanic at the time of the collision is believed to have been between an estimated 22.3 to 22 and a half knots, with the triple expansion reciprocating engines producing revolutions of 77 RPM.
 
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William Oakes

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Optimal speed to avoid collision! Stop at night time as the Californian did so!

Stopped isn't a speed.With all due respect, that is not an answer to the question that I asked.
The question is, what maximum moving speed could she travel at, and still navigate around the icebergs?
 

Incony

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the unknown, i understand,is the exact distance of the iceberg from the Titanic at the time it went hard a starboard at 22 knots.. which is about 38ft a second... and that is because two thirds of the berg is under water - so its submersed size/ diameter could be much bigger than what sits above the water.. if one calculate the time from the call "iceberg right ahead.." to the point of impact, one gets an idea of the distance, and given the Titanic's turning circle of 3860 feet one can plot how far way from the berg the titanic would have to be to avoid something easily as wide and probably wider than itself... i have read this -and it says the berg was about 500 yards away, when sighted.. and as a guide and i cannot certify its accuracy, i just share this.. The Turning Characteristics of the SS Titanic by Samuel Halpern - ppt video online download - so.. 1500 feet wasnt enough to avoid the iceberg, not even its above water part, since ice fell onto the deck.. it took about 37 seconds or perhaps one or two seconds more, to cover that distance, and reach the hidden part of the berg.. Another 25 seconds or 300 yards might have saved it from contact.. as an estimate then i suggest 800 yards at @22 knots.. ie about half a mile would be needed - it is the hidden size of the berg that isnt known, i.e its shape under water.. The speed doesnt alter the turning circle so even the engines full astern or stopped doesnt.. i.e the turning circle was near the same at 11 knots..
 
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William Oakes

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the unknown, i understand,is the exact distance of the iceberg from the Titanic at the time it went hard a starboard at 22 knots.. which is about 38ft a second... and that is because two thirds of the berg is under water - so its submersed size/ diameter could be much bigger than what sits above the water.. if one calculate the time from the call "iceberg right ahead.." to the point of impact, one gets an idea of the distance, and given the Titanic's turning circle of 3860 feet one can plot how far way from the berg the titanic would have to be to avoid something easily as wide and probably wider than itself... i have read this -and it says the berg was about 500 yards away, when sighted.. and as a guide and i cannot certify its accuracy, i just share this.. The Turning Characteristics of the SS Titanic by Samuel Halpern - ppt video online download - so.. 1500 feet wasnt enough to avoid the iceberg, not even its above water part, since ice fell onto the deck.. it took about 37 seconds or perhaps one or two seconds more, to cover that distance, and reach the hidden part of the berg.. Another 25 seconds or 300 yards might have saved it from contact.. as an estimate then i suggest 800 yards at @22 knots.. ie about half a mile would be needed - it is the hidden size of the berg that isnt known, i.e its shape under water..
Thank You!
Great Info!!!!
 
Mar 22, 2003
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The question is, what maximum moving speed could she travel at, and still navigate around the icebergs?
As stated above, speed doesn't alter the turning circle very much with all three engines working. The key parameter is distance to the object when the order to turn is first given. You may be interested in one of my more recent look at this issue here: http://www.titanicology.com/Titanica/NarrowShave.pdf.

In this relatively new article we look closely at the timing of the order to turn Titanic away from the object sighted ahead after the lookouts sounded their 3-bell warning. We show that to completely avoid striking the iceberg without further action, the hard-astarboard helm order would have had to come about the same time as those 3 bells, offering the 1st officer on the bridge almost no time to assess the unfolding situation. With only seconds to assess a difficult situation, it became clear to the 1st officer that the ship was just too close to avoid striking the object that loomed ahead. He had little choice but to take action that would minimize the potential damage to the ship, an action that was in keeping with guidelines that appear in modern day textbooks.
 
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Arun Vajpey

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In this relatively new article we look closely at the timing of the order to turn Titanic away from the object sighted ahead after the lookouts sounded their 3-bell warning. We show that to completely avoid striking the iceberg without further action, the hard-astarboard helm order would have had to come about the same time as those 3 bells, offering the 1st officer on the bridge almost no time to assess the unfolding situation. With only seconds to assess a difficult situation, it became clear to the 1st officer that the ship was just too close to avoid striking the object that loomed ahead. He had little choice but to take action that would minimize the potential damage to the ship, an action that was in keeping with guidelines that appear in modern day textbooks.
Thanks for that Sam. With reference to the highlighted part above, can I ask how much time do you think elapsed between Fleet seeing something in the horizon (call it a 'haze' or whatever you like; but given the conditions, it could not have been anything but the iceberg) and deciding that it was a solid object in the ships path and so ringing the 3 bells? Reading Fleet's testimony, I get the feeling that there was a time lag, perhaps as much as 30 seconds, before he saw what he later described as a haze in the horizon and actually rang the bells.

Putting the question another way, could Fleet have rang those bells earlier? If so, that would also have alerted Murdoch that much earlier and everything else that followed would be similarly affected.
 

William Oakes

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As stated above, speed doesn't alter the turning circle very much with all three engines working. The key parameter is distance to the object when the order to turn is first given. You may be interested in one of my more recent look at this issue here: http://www.titanicology.com/Titanica/NarrowShave.pdf.

In this relatively new article we look closely at the timing of the order to turn Titanic away from the object sighted ahead after the lookouts sounded their 3-bell warning. We show that to completely avoid striking the iceberg without further action, the hard-astarboard helm order would have had to come about the same time as those 3 bells, offering the 1st officer on the bridge almost no time to assess the unfolding situation. With only seconds to assess a difficult situation, it became clear to the 1st officer that the ship was just too close to avoid striking the object that loomed ahead. He had little choice but to take action that would minimize the potential damage to the ship, an action that was in keeping with guidelines that appear in modern day textbooks.
Thank You so much.
Honestly, this is what I suspected.
At 450 -500 yards, and with the turning points that you describe, there simply wasn't enough time to successfully avoid the iceberg.
And that is a sad conclusion.
Thank You for your well thought out insights.
 

Jim Currie

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Thank You so much.
Honestly, this is what I suspected.
At 450 -500 yards, and with the turning points that you describe, there simply wasn't enough time to successfully avoid the iceberg.
And that is a sad conclusion.
Thank You for your well thought out insights.
As a point of interest: the berg was first seen high out of the water as a dark shape on a dark night from a point 90+ feet above the water. Since it was not much more than 70 feet high, it had to have been very close indeed to have been described in such a way. The timing between helm order and impact part of the evidence of the Quartermaster on the wheel at the time seems to corroborate this
 
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I would think the optimal speed for avoiding collision would be zero. As in stopping for the night like the Californian did. Cheers.
 
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Arun Vajpey

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I am not saying for one moment that there was any similarity between the situations of Endurance and Titanic but didn't Ernest Shakleton comment something about reducng a ship's speed to about 4 knots when there was ice around?
 
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I am not saying for one moment that there was any similarity between the situations of Endurance and Titanic but didn't Ernest Shakleton comment something about reducng a ship's speed to about 4 knots when there was ice around?
That sounds about right. I know on one of their better days they made around 120 miles. That was after being warned by whalers that there was heavy ice ahead on their way to Antarctica. 120 miles/24 hours = 5 mph which is close to 4 knots. So it sounds like he practiced what he preached cause the Endurance was capable of around 10 or so knots. But he could have been following Frank Worsley's advice who in my opinion was the unsung hero of that expedition. Or at least he deserved a lot more credit in saving everybody's life with his navigating skills. Tough guys on that voyage. Cheers.
 
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Arun Vajpey

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As I said (and as the man himself admitted) the situations were not comparable. Still, Sir Ernest Shackleton was a man who kew about travelling through ice and IMO what he felt was the optimal speed under those circumstances is relevant irrespective of the maximum speed the ship was capable of doing.

Following is an excerpt from Shackleton's testimony at the British Inquiry int the Titanic disaster. I have copied and pasted what I conidered to be his general views that could apply to the Titanic disaster but the entire testimony makes very interesting reading.

25044. And supposing you were passing through a zone where you had ice reported to you, would you take precautions as to the look-out? Supposing you only had men in the crow's-nest, would you take any other precautions?
- I would take the ordinary precaution of slowing down, whether I was in a ship equipped for ice or any other, compatible with keeping steerage way for the size of the ship.


25045. You would slow down?
- I would slow down, yes.

And supposing you were going 21 to 22 knots, I suppose that would be the better reason for slowing down?
- You have no right to go at that speed in an ice zone.

25073. Just one question, Sir Ernest: Do you frequently find a haze in close proximity to an iceberg?
- Generally when the temperatures are different - the temperature of the water and the temperature of the air.

25084. The pace you speak of, four knots, was when you were in among the ice, turning and twisting, as you have described it?
- Yes, when we were in the ice region. I would not like to compare in any way the North Atlantic, with its comparatively few bergs, with the south, but if I were going 20 knots, I would want to get down to the steerage way just the same as when I am going six knots I want to get down to four knots.

25085. But you do not compare the state of things which you found, as you were approaching the south Pole, where you had to turn and twist among the icebergs and masses of ice, with what prevails in the North Atlantic?
- No, I do not compare it. The point I look at is, when you get a very fast speed, you must slow down, even as we in narrow waters had to slow down in our little ship.

25086. Slow down to four knots?
- We did.

25087. What do you suggest a liner should slow down to?
- I am not qualified to give an opinion, but I should suggest a liner should slow down sufficiently to give her steering way, which is, of course, More than the full speed of my own smaller ship.

25088. What do you estimate would give a vessel like the "Titanic" steering way?
- I am not qualified to say. I do not know enough of the turning movement of ships over 10,000 tons; I should say 10 knots.

25089. (The Commissioner.) That would be half-speed, practically?
- Yes, My Lord.


25090. (Sir Robert Finlay - To the witness.) Is your suggestion that all liners in the Atlantic should slow down to 10 knots as soon as they know that they may come across an iceberg?
- As soon as they know they are in an absolute ice locality, which they can tell now because of the wireless.
 
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Incony

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At only 10 knots, and assuming the turning circle remains the same, stop or hard astern changes the time from sight of the iceberg to maybe @ two minutes.. (10 knots is nearly 17 feet a second) i.e 500 yards covered in 93 seconds without slowing down = it just means it takes longer to hit the berg, it does not mean one can turn faster.. one cannot suppose that the berg would be seen sooner at 10 knots.. ? so the distance from sighting to the Titanic doesnt change... just the time taken to cover the distance does.. ok.. one could work out how far the Titanic would go, before hard astern at 10 knots would affect the speed... but i bet it needs more than 500 yards.. and two minutes - and the Titanic would still hit the berg. The force of the impact changes, but not its possible effects, because the contact time increases at a slower speed.. so its possible the damage could be even more severe. As an engineer, i know that dealing with loads weighing 250 tons that are moving at only 1 foot a second... if it hits something like your hand - its still going to flatten it. - at 17 feet a second it just happens faster..:)

so... the kinetic energy of contact, ( a partial inelastic collision ) is lost by contact both in the berg and the Titanic hull, it a bit like looking at cars colliding in slow motion or an explosion in slow motion... as opposed normal time.. so going slower means there is more opportunity for contact.. and the longer the contact the greater the opportunity for energy to be transmitted? so it might have meant more holes or bigger holes.. or both.. because the berg would not break up as much.. neither would the Titanic or the Berg be pushed apart faster..?
 
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Arun Vajpey

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At only 10 knots, the distance from sighting to the Titanic doesnt change... just the time taken to cover the distance does.
True. Also true that that the lower speed the Titanic's turning characteristics would be different; I would like an experienced seamn like Jim to tell us how different.

But the fact remains that Fleet would have seen the iceberg at the same distance as he did and rung then bells at the same moment that he actually did. It follows that Murdoch would then scan the Ocean ahead as he did and when he spotted the iceberg himself, he would have instinctively worked out that he had a timeframe X seconds before the ship's bow reached the iceberg. Likewise, in the real life scenario, Murdoch would have worked out a time factor Y seconds before the two objects met.

Since 10 knots would have been less than half of the Titanic's actual speed at the time, X seconds would be about twice as much as Y even allowing for human estimation errors. If Murdoh had given the same order at the same time, the Titanic would have been twice the distance away from the berg as it really was that night if it was travelling at only 10 knots. Even allowing for the slower turning reponses at 10 knots, the ship would have started its turn while much further away from the iceberg. Considering that even at 21.5 knots Murdoch almost pulled it off, IMO there is a very good chance that he might have actually done so at 10 knots.

The only difference could be is that if the Titanic had been travelling at only 10 knots and the crew responses from the moment of first sightng had remained exactly the same till the hard-a-port helm order, Murdoch then might not have stopped the engines. In the real event that did not make any difference anyway.
 

Jim Currie

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At only 10 knots, and assuming the turning circle remains the same, stop or hard astern changes the time from sight of the iceberg to maybe @ two minutes.. (10 knots is nearly 17 feet a second) i.e 500 yards covered in 93 seconds without slowing down = it just means it takes longer to hit the berg, it does not mean one can turn faster.. one cannot suppose that the berg would be seen sooner at 10 knots.. ? so the distance from sighting to the Titanic doesnt change... just the time taken to cover the distance does.. ok.. one could work out how far the Titanic would go, before hard astern at 10 knots would affect the speed... but i bet it needs more than 500 yards.. and two minutes - and the Titanic would still hit the berg. The force of the impact changes, but not its possible effects, because the contact time increases at a slower speed.. so its possible the damage could be even more severe. As an engineer, i know that dealing with loads weighing 250 tons that are moving at only 1 foot a second... if it hits something like your hand - its still going to flatten it. - at 17 feet a second it just happens faster..:)

so... the kinetic energy of contact, ( a partial inelastic collision ) is lost by contact both in the berg and the Titanic hull, it a bit like looking at cars colliding in slow motion or an explosion in slow motion... as opposed normal time.. so going slower means there is more opportunity for contact.. and the longer the contact the greater the opportunity for energy to be transmitted? so it might have meant more holes or bigger holes.. or both.. because the berg would not break up as much.. neither would the Titanic or the Berg be pushed apart faster..?
First of all, we must understand how a ship behaves when a hard-over emergency turn is ordered.
In real life, using a steam steering gear of Titanic vintage, there would have been a small lag between helm movement and the change of direction. i.e. unlike a car steering system, the bow would not start to move left the moment QM Hichens started to apply left rudder i.e. there would be a momentary delay.
When the bow did start to move left, it would start to do so almost imperceptibly, but quickly gain swing speed. However, the moment a heading direction changes, the ship begins to slow down - fairly quickly if it is a hard-over turn, and that is without touching the engines.
I believe the answer to Williams' question might be found in the evidence of Captain Rostron if you ignore his waffle about Carpathia's speed.
Just before Carpathia arrived beside Boxhall that morning, Carpathia was making about 14.5 knots. she had to swerve suddenly to avoid an ice berg . That berg was North East of where Titanic sank because North East is the direction taken by Boxhall when rowing away from the sinking ship. If I remember correctly, there was only one iceberg close to Boxhall at that time and it was SE - between him and the approaching(or stopped) Carpathia.
So there's a simple answer for you , William - 14.5 knots and with lots of lookouts.;)