Section 1: Knowledge Check
1. Stability Book:
a. What is the purpose of a stability book on a vessel, and what key information does it include?
A stability book includes the vessel's hydrostatic parameters and righting moments relative to
the 6 degrees of freedom of a floating structure. Most importantly in my opinion the righting
moment relative to the heel angle across the longitudinal span of the structure (GZ curve, where
capzinging is likely to occur). All data in the book should be included in all load conditions
(Lightship to fully loaded and with extreme configurations relative to tankage and cargo all
situations should be verified). Furthermore, particular parameters such as metacentric height at
varying loads is given which is useful to determine the natural rolling period of the structure to
avoid unstable behavior.
b. How would you verify that a vessel remains compliant under varying load conditions?
I would personally use commercially available hydrostatic software such as Maxsurf or
RhinoHyd in addition to a panel method solver (only valid for small velocity motions ie Froude
number less than 0.3 which is no problem for these offshore structures) and wave interaction
such as Ansys Aqwa or OrcaFlex (no personal experience in OrcaFlex). Most importantly I
would keep an updated weights book in the as built condition during outfit to ensure that all
weights in the vessel match. The weightbook would interpolate between hydrostatic data at
different load lines to simplify engineering.
2. Class vs Flag State:
a. Differentiate between the responsibilities of the classification society and the flag state.
Classes such as DNV, Llodyds, BV are responsible for ensuring that technical characteristics
are met, with the structure, stability, machinery, safety (fire fighting, lifesaving etc..). Class
societies also protect the environment and stipulate technological requirements for craft. There
are various subsections one can select to be classified by for instance Battery Power or Ice
class. Usually classification societies use the symbol ✠ (Maltese cross) to denote approval.
b. Explain a scenario where both must be involved during a marine incident.
In the hypothetical scenario similar to the MS Estonia ferry incident where the bow loading door
failed due to technical requirements and created slush onboard capsizing the ship and creating
multiple casualties. I assume the ships class society was investigated fro the approval of the
loading doors design and damage stability in the flooded deck. Furthermore SOLAS had
adopted new regulations after the incident with the requirement of ships to carry EPIRB
(Emergency personnel indicating radio beacons).
3. SOLAS Compliance:
a. What are the most critical SOLAS chapters relevant to the design of an underwater structure?
I opened the 2024 consolidated edition of solas and could not find regulation that applies
exclusively to underwater structures, hence I would assume that Escape routes as it is
particularly challenging underwater.
1
b. How would SOLAS affect the crewed or uncrewed nature of your system?
Since solas stands for the UN ́s safety of life at seam uncrewed structures do not require
compliance nonetheless when deployment is in effect (towing lifting, anchoring etc..) the
support vessel must meet criteria to ensure the safety of the installation crew.
4. VHF & AIS:
a. Explain the use and range of VHF and how it complements AIS.
VHF or very high frequency radio is the most widely used marine radio frequency (ship to ship
communications etc..), AIS uses the same frequency and antennas (Class B at least Class A is
via satelite) to transmit vessel details (Vessel name, Speed, Course over ground, and GPS
coordinates lat lon, most importantly however it can even transmit the ships, current draft, flag
state, MMSI number last port of call and next port of call). AIS buoys can serve as aids to
navigation notifying mariners of potential hazards (like an underwater obstruction) ro even
fisherman for their position of their nets. I am a certified Short Range radio operator and have
International Operator of pleasure craft (ICC), both issued by the UK ́s RYA, I have over 7000
nm of offshore navigation experience and more than 100 sea days. where I have had extensive
use of radio AIS and radar equipment for communication between both pleasure and
commercial craft furthermore I have complete the installation on NMEA 2000 networks on
sailboats myself and I am a huge proponent of it as AIS is more precise than radar in providing
CPA and TCPA (Closet point of approach and time to it). However, AIS is not a substitute to
radar particularly in areas of the world where the technology is not yet used; radar must be used
as a primary means of collision avoidance.
b. How would you integrate AIS into an autonomous structure like an underwater data pod?
GPS, or VHF waves travel underwater, hence GPS, and VHF antennas with a wired
connection would have to be placed on the surface with a buoy for instance to transmit the
position of the data pod accurately. An alternate solution could be to program a known position
with a nearby existing antenna but this would require falsifying the GPS input of the AIS
transponder and it would only have the range of the nearby antenna and it would not reflect
unexpected movements of the pod.
5. Radar Systems:
a. Compare the performance of X-band and S-band radar in different weather and sea
conditions.
X-Band radar will detect nearby objects with high precision whereas S-bands longer range but
lower precision might be useful for detecting incoming weather systems or birds (In the case of
fishing boats). One of the downsides of X/band is that it can get lots of noise from significant
wave peaks in bad weather.
b. Which would you recommend for monitoring marine trac near your system, and why?
X-band because it is more precise at detecting objects once they are in proximity. Additionally,
S-band radars require a lot more power, sometimes greater than 30kW and have huge spans of
more than 3m, usually the emitter beam is not covered by a dome and are heavy which
complicates installation and maintenance.
2
6. Corrosion / Osmosis / Fouling:
a. Describe the main differences among corrosion, osmosis, and fouling.
b. What design strategies or materials
● Corrosion has to do with the oxidation to metals. There are various types of corrosion
mainly due to exposure to the environment, contact with dissimilar metals (electron
traveling between them), or crevice corrosion which occurs with trapped moisture in a
metal part.
○ To prevent and control you can use alternatives materials like aluminium,
composites or plastics, use protective marine coatings and frequently repaint,
use stainless steel when strength is required. When using fasteners it is
important to isolate two metals with grease or sikaflex. Sacrificial anodes zincs
have to be placed to make sure that components are not eaten.
● Osmosis is a phenomenon that attacks fibreglass structures in moist or underwater
environments with water soluble compounds causing blisters, delamination and
structural failure.
○ It can be avoided by using high quality resins like epoxy with thick barrier coats,
gelcoats or avoiding prolonged exposure. Frequent checks when the vessel is on
a dry dock.
● Fouling is an organic growth of marine life on underwater surfaces, barnacles, algae
etc..
○ Avoided by using anti-fouling bottom paint either very slippery to prevent grip
from organic compounds or with toxic compounds that kill them (or both). There
are also new coatings like Finsulate that mimics seal fur (but requires vessel
motion). My favourite one is Intersleek (Not toxic silicon based so it is very soft
and fragile but effective). And I would be keen to try Clean Ocean Coatings very
hard and excellent when paired to an underwater robot toing preventive fouling
maintenance. Last but not least, ultrasonic vibration transmitters fixed to a metal
hull (Has to be metal cannot use a soft antifouling)
3
Section 2: Design Challenge
Design a sealed underwater data module (like Microsoft’s Natick) deployed on the coast at:
● Depth: 30 meters
● External Temp Range: 4°C–18°C
● Salinity: 35 PSU (open ocean)
● Dimensions Limit: Max 3m (diameter) x 10m (length)
● Deployment Duration: 3 years without retrieval
● Power: Subsea cable (5 kW max)
● Data: Fiber optic uplink
● Location Traffic: Moderate shipping activity nearby
● Marine Growth: Moderate biofouling region
1. Design Overview (max 500 words)
○ Shape, structure, and materials
I have opted for a tubular structure using NPS 16 with schedule 10 wall thickness standard in
the offshore industry with a 406.4mm OD and 6.35mm a back of the napkin calculation yields a
safety factor of 2x to withstand the pressure at 30. The tubes are held together with 12mm steel
plates with slots to fit into every tube. In each end and at the centerline with 6 plates total. The
legs which also fit into a 40ft container have to be installed when the crane is in use. (The
system has not been designed).
○ Internal systems: power, cooling, redundancy, access
The interior of the 21 tubes provide 23m3 of internal volume. I am hoping that passive cooling
will be sufficient with the tubular structure. Having so much exposed surface area near the
electronics nonetheless a glycol water mixture and fans running through a heat exchanger could
be advantageous.
There are 21 tubes hence there is redundancy rather than just one. The tubes are
interconnected to allow for cable trays to travel. Power comes from two cables and data from
another two uplinks. Thru hull cable inlets are fitted with a cofferdam to ensure watertightness of
the structure.
Electronic equipment is placed in trays that slide in and out of the compartment and the end of
each tube is sealed with a flat plate 20mm thick (Since the opening area is so small no need to
create a domed structure or bulkheads inside the pipes).
Overall the design focuses on logistical ease fitting into a container. Manufacturability using
standard pipes available off the shelf and no large custom parts needed. Lastly, the multiple
tube arrangement makes it excellent for heat transfer.
4
2. Stability & Deployment Strategy
○ How will you maintain stable positioning under varying currents?
This is the major downside to my design I should have opted for a 3 legged version one
anchored and two with yaw free rotation around a single anchor point, nonetheless I picked 4
hence
○ How is the unit ballasted or tethered?
All legs are ballasted with sand (cost effective and widely available). Enough sand would be
calculated to keep the system in place by its own weight nonetheless a 3 sets of redundant
SHHP (super high holding power) anchors within a delta type anchor could be deployed from
the surface ship to avoid divers.
○ Deployment:
The structure is designed to fit in a 40ft container with the legs folded hence shipping worldwide
is easy. It can be loaded onto the deck of a ship with at least 12m*12m open space and
deployed from a ship crane.
3. Risk Analysis Table
○ Corrosion, pressure fatigue, marine life interference, etc.
○ Mitigation techniques
Risk Description Risk
Factor
Mitigation techniques
Corrosion Steel degradation due to
saltwater exposure
8 Use sacrificial anodes, and inspect
with ROV 2 periodically.
Deployment Challenges or failures during
installation (e.g., sinking,
anchoring issues).
7 Conduct seabed tests and
simulations prior to physical launch.
Practice leg unfolding on land prior
to real on-ship scenario.
Implosion Collapse of the structure due to
external water pressure
exceeding design limits.
6 Conduct FEA analysis of detailed
parts. Use approved materials.
Fouling Marine growth (barnacles, algae)
on the structure, increasing drag
and corrosion risk.
5 Apply anti fouling ruth potential
cleaning by ROV. (3 years should
not be a problem for intersleek even
static vessels)
Power Failure Loss of power disrupting data
center operations (e.g., cable
failure, equipment malfunction).
9 2x power and data cables, Lithium
battery bank with 60kWhrs to
supply power for at least 12 hrs.
Collision Structural failure of vessel or
failure due to contact with traffic
of marine life
7 AIS Buoy and radar reflector,
notification to local authorities to
avoid surface fishing. Use class
approved reinforced cable to avoid
5
4. Comms & Navigation Safety
○ Use of AIS, radar reflectors, lights, or other safety signals
As previously mentioned in the AIS question of section 1. a buoy floating over head with VHF
and GPS antennas or a ground based transponder with a hard coded GPS coordinates.
○ Maintenance of compliance with maritime safety regulations
Regular surveys by class societies and use of approved materials and components, crew for
installation and removal with appropriate training such as STCW-95.
