Posted on 06/21/2023 3:07:05 AM PDT by servo1969
Pride in 1912.
Pride in 2023.
Nothing new under the sun. Well, except for carbon fiber, one would suppose.
Strange looking casket, but it holds five.
@MaschinenMusik
What I really don't like about the design:
- I assume the Carbon Fibre pressure hull was fabricated by winding monofilament around a cylindrical core (seen in the video), then it gets wrapped in a vacuum bag, and then put in an autoclave. It's a good technique, but you still can have micro cracks and channels as a result that can be a starting point to fatigue cracking.
- Combination of Carbon Fibre ["CFK"] and Titanium: You have a huge mismatch of the coefficient of thermal expansion of a factor 5 to 6 (CFK 50-60 x 10^-6/K vs 10 x 10^-6/K for Titanium). So when that thing cools down, the Titanium will shrink much more than the Carbon Fibre hull, putting a lot of strain on the glued join. Thermal cycling -> fatigue cracking.
- There is a mismatch in elastic modulus of Carbon Fibre and Titanium which will lead to a mismatch in elastic deformation when exposed to high pressure (only 1 atm in planes, 450 atm at Titanic level) -> again fatigue issues at the joints.
One can mitigate some of that by proper engineering, but combinations of fibre reinforced plastic and metal are tricky especially when cycled through pressure and temperature gradients.
- - -
@kevinthomas5364
Good points on the coefficient of expansion of various materials and accompanying fatigue failure - basic elements of engineering design for components subject to these conditions.
The glue too becomes a big piece of this puzzle as it is part of the seal keeping the pressure out. Typically, dried glue tends to be more on the brittle scale with little plastic deformation upon failure.
It appears that the joint design encapsulated the Titanium over the carbon fiber hull on both sides. This would put tremendous pressure upon decent on the Titanium joint squeezing the carbon it is glued too.
The thermal and pressure stresses would be additive too as both would tend to squeeze the Titanium upon descent and move outward during ascents. This is a perfect storm forcumulative
["Filament wound carbon parts have outstanding characteristics, such as high stiffness and low weight. Not only can they be designed to be temperature stable, they can also be adapted to a wide range of CTEs - Coefficients of Thermal Expansion." Source: CarboSpaceTech (CST) - located on Lake Constance in southern Germany]
Excellent points. This should have been basic engineering.
” I assume the Carbon Fibre pressure hull was fabricated by winding monofilament around a cylindrical core (seen in the video)”
Carbon fiber is laid in overlapping strips from rolls as seen in the video.
Seems to me, that some energy must be expended, in order to remove moisture from the Titan sub atmosphere; plus, energy expended in order to heat the sub - given that the seawater temperature at depth below 4,000 ft is 1 - 4 F deg.
- - -
Cooling System - Gemini Capsule
http://geminiguide.com/Systems/cooling.html#SUIT_And_CABIN_TEMP_Controls
EXCERPT:
The cooling circuit in which the cooling system operates is dependent upon the temperature loads generated by the equipment, spacecraft phase of flight and the temperature within the spacecraft cabin.
Cooling is provided throughout the mission up to pre-retrograde firing. At this time the coolant pump packages are Jettisoned with the adapter equipment section, terminating spacecraft cooling.
Spacecraft 5 and 8 through 12 require both loops to be operated contlnuously. In spacecraft 6 the primary circuit operates continuously providing the required cooling during low temperature loads. The secondary circuit is used, in conjunction with the primly circuit, during phases of high temperature loads; namely - launch, rendezvous, and pre-retrograde.
Under normal heat loads, the number 1 pump in the primary circuit provides the required cooling. Under peak heat loads, the number 1 pump in the secondary circuit is used with the primary circuit number 1 pump to provide maximum cooling. In the event of a number 1 pump malfunction in either circuit, the number 2 pump in that circuit is used.
In the event of both pumps failing in one circuit, both pumps of the remaining circuit can be used to provide the required cooling. (Spacecraft 6 does not have the number 2 pump in either circuit.)
From Ocean Gate’s website:
“Real-Time Health Monitoring
The most significant innovation is the proprietary real-time hull health monitoring (RTM) system. Titan is the only manned submersible to employ an integrated real-time health monitoring system. Utilizing co-located acoustic sensors and strain gauges throughout the pressure boundary, the RTM system makes it possible to analyze the effects of changing pressure on the vessel as the submersible dives deeper, and accurately assess the integrity of the structure. This onboard health analysis monitoring system provides early warning detection for the pilot with enough time to arrest the descent and safely return to surface.”
This is about a silly a risk mitigation strategy as I have ever seen. In industry, subject to peer review and some certifying authority such as ABS or DNV I would never expect it to pass muster. Especially not with a material known to fail suddenly, catastrophically and completely such as a composite.
I am an engineer with more than 40 years of oilfield high pressure containment experience and 30 years of experience in subsea facilities including design and construction of large subsea systems. The environment is unforgiving and destructive. Things often don’t work as theory, calculation and design expect they will. That is often with steel, metal-to-metal seals and elastomer seals. Composites are a material we simply steered clear of because of the vague failure conditions and that there is generally no fatigue life, it just fails when it wears out. Just look at one stress-strain plot for a composite and see what I mean.
In steel construction we have spent decades and huge sums studying fracture mechanics, it is still a black art. One associate of mine suggested that without a wide safety margin in the predicted fracture failure cycle number it was like measuring with a micrometer just how close you could get to a mule before it would kick the living hell out of you.
Sub-safe is a phrase we used and understood in subsea construction. We learned it from the Navy guys we hired to help us learn from their experience. To us it meant that if you saw a risk you had to run it to ground until it was either invalidated or solved. You can accept nothing else. Nothing is fail-safe it is only as good as you can make it and that does not accept half-measures or compromise.
Sometimes it is a good idea to listen to the reservations and experience of 50 year-old white guys.
I would say, “rest in peace a-hole” but that wouldn’t be nice would it?
We would have started with a risk matrix of just everything we could think of that could go wrong. Dissimilar properties in thermal coefficients and modulus of elasticity would be two.
The matrix would begin with a brainstorming meeting where everything is fair game and then expand from there with each week’s technical review meetings until all elements were satisfied or otherwise removed.
This is not, as some suggest, hindsight or Monday morning quarterbacking. It is just one standard component of quality and professional major project and engineering management.
If the process is thorough it is amazing to me how anything is ever accomplished. You can only do trial and error if you can afford it or there are no environmental disasters in the offing or lives to be ended in the process. Their risk mitigation strategy to instrument the hull looking for accumulating failure indications is essentially a trial and error process. These look to me like amateurs with too much money. Being broke might have saved them from themselves.
- OceanGate's, Carbon Fiber Hull Winding, and
"Construction of Cyclops 2 began by winding the carbon fiber [pressure] hull on March 13 2017 . . . Cyclops 2 is a research class submersible designed to take five people to depths of 4000 meters (13,124 feet)"
- DarkAero's, Why We Use Different Types of Carbon Fiber in the DarkAero 1, and
Describing different Carbon Fibre materials and their applications, using for example, the DarkAero 1 aircraft construction.
- News Nation - Ashleigh Banfield's, "Why did they wait so long to tap?".
[Expanding the video description . . .] A Canadian aircraft using sonobuoys in order to search for the missing OceanGate submersible, detected “underwater noise” on Tuesday, June 20, 2023 - from where the submersible was touring the Titanic wreck site. Ashleigh Banfield interviews former USN submarine commander Capt. Don Walsh (ret.), who also participated as a technical advisor for James Cameron's 2012 solo dive in a large pod-shaped submersible, the DEEPSEA CHALLENGER, to the Titanic site.
Capt. Walsh tells Ashleigh Banfield about the communications procedures for submersible explorations, that have been a standard - communicating every 30 minutes. The TITAN crew would have, should have, communicated so, during the submersible's descent. Therefore, the support group aboard the surface ship, must know more than what has been related to the public.
On the other hand, if at one end, the titanium spherical dome cap for that cylinder, deformed a wee bit, that could cause a problem for the titanium ring epoxy bond to the cylinder.
No info yet, on what structural support (egs. ribs) may be, or not, within the respective titanium spherical dome at each end of the cylinder.
One of the comments to the linked [Legal Insurrection] article included the following insight into Mr. Rush’s attitude toward safety:
“There’s no voice communications with topside because Stockton Rush, in his interview with Teledyne, said that he was tired of being interrupted from topside with update requests which is why chose to go with the Data Acoustic Modem that would transmit the position and depth of the submarine continuously so that he could enjoy his submarine ride.”
Capt. Walsh mentioned that some of the communications tended to interrupt 'the pilot,' but are still a necessary standard of operations.
'Safety is relative': What CEO of missing Titanic submarine company told me during my trip blockquote
At 04:36 of 0616, you can see a port side view of the TITAN, with its front spherical dome "hatch" opened. In the interview, David Pogue said that, in operation, only 17 of the 18 front dome "hatch" flange bolts are installed - the topmost (12 o'clock position) bolt is not installed.
I wonder if the bolts are replaced for each dive. If the bolt torque is mild.
1:06 / 14:18 Photo with front dome "hatch" open. [Might be Cyclops 1 - notice the shroud for the front dome "hatch."]
3:14 / 14:18 The TITAN Cyclops 2 can send PING's back to the surface mothership:
The communications that they have . . . They do not have any radio communications because radio waves do not go through the water. They have a rudimentary system which is like a SONAR system. The vessel sends a PING back to the [mothership] vessel every 15 minutes, and within that PING, they can send very short text messages like the old text system that we had before smart phones.
4:10 / 14:18 The people being able to breathe . . .:
What they have on board, they have air for about 4 days. And also, they have a scrubber system similar to what they have on spacecraft. That converts CO2 back into breatheable air. They also have backup scrubbers. They also have, for final emergencies, SCUBA tanks beneath the floorboards.
4:41 / 14:18 Drinking water . . .:
One of the things that has not been mentioned, is how much water they have. The human body can only survive about 3 days without any water. . . They each only took along a canister of water. The dive itself was meant to last about 8 hours. 2.5 hours descent; 3 - 4 hours observation at depth, near the seabed; 2.5 hours ascent. They lost communications around 1 hour 45 minutes.
5:38 / 14:18 According to 1 report . . .:
They have 7 types of redundancy systems on board. They can re-float this vessel, if they get into trouble. And numerable of those systems work, if there is a power failure. If lights go out, and there is no power, they can still resurface this vessel. There are weights that they can drop, to create buoyancy. There are propellors that point up, in order to push the vessel up. There are airbags that can be inflated, in order to lift the vessel to the surface.
Now one idea is, that the vessel has surfaced, and it is bobbing around, waiting to be picked up. Possible, but unlikely; if on the surface, they could use radios in order to communicate. They might only have VHF and shortwave radios on the vessel. [His previous remark about they're not having radio - he apparently meant, no radio communications at depth.]
I used a formula for calculating the temperature at depth, that I found online but probably did not have javascript working correctly for the webpage, and/or I mixed up C with F deg.
Yet I remember a physics problem that showed, that seawater at great pressure, can have a temperature below 0 deg. C - but not appear to be frozen. Just found:
https://aos.princeton.edu/news/supercooled-southern-ocean-waters
“They’re dead, Jim”
Survival chances? Astronomical.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.