Tutorial questions Flashcards
Why might a side impact torpedo be less affective against a modern surface target
a. More heavily armoured
b. Better water tight integrity
c. Better damage control systems
How does a heavyweight torpedo employ its warhead to better effect against a surface target
Gas bubble effect
Describe the key stages of a heavyweight torpedo detonation under a surface target
a. Warhead beneath the keel
b. Explodes beneath the keel causing shockwave causing crushing effect to hull
c. Rapidly expanding gas lifts ship out of the water causes maximum loading on the centre of the hull causing stress fractures
d. Gas bubble contracts causing compression on ships hull as platform sags into the void
E. Shrunk has bubble expands in a jet causing high-pressure water and gas jet to vent through the ship
Why might a larger payload be required to engage an SSBN over an SSN?
a. SSBN is bigger
b. More pressure holds
c. Bigger standoff distance between pressure hold and casing distance can be up to 4.5m
Bigger the space less effective the explosion will be
How does a heavy weight torpedo employ its warhead to engage a submarine target?
Submarine Gas Bubble effect
How does a lightweight torpedo employ its warhead to engage a submarine target?
Shapecharge
What are the general requirements that a torpedo must fulfil to be successful?
a. At least 150% speed of target
b. Stealth
c. Depth
d. Safety
E. Endurance
Name and describe the perfect torpedo hull form for minimal drag. Why is this not practical for military applications?
a. Carmichael Hull Form
i. Diameter increases gradually from the nose to create a laminar flow of water in the boundary layer
ii. Found that a diameter to length ratio of 5/7 is best
iii. All control surfaces must be kept aft and the body must have a very high quality surface finish
b. The internal layout will be complex and does not easily support a modular design
c. Significant amount of wasted space which could have been taken up by fuel or warhead
d. Transducer placement is not ideal and a complex beamformer will be required to overcome the shape of the torpedo nose
e. Embarkation, stowage and handling will also be more difficult due to the complex body shape
How much more power is required to increase a torpedoes speed from 20kt to 50kt?
15.6
What affects the choice of energy source for a torpedo and what choices are there?
a. Energy required for desired speed and endurance
b. Operating characteristics such as depth of operation, self and radiated noise and initiation method (impulse/swimout)
c. Safety of fuel
d. Cost
e. Electric Power (primary or secondary)
f. Thermal Systems (open cycle or closed cycle)
What is the difference between a primary and secondary battery?
a. Primary is a one time use the electro-chemical reaction is not reversible
b. Secondary is rechargeable but has shorter endurance
What propulsion system is fitted in spearfish and what fuels does it employ?
a. Propulsor , Sundstrand gas turbine , Open cycle gas turbine
b. Using OTTO fuel/ HAP (hydroxyl Ammonium Perchlorate)
What are the advantages and disadvantages of an open loop thermal propulsion system?
a. Depth sensitive due to sea back-pressure
b. Produces gaseous wake and is therefore noisier
c. Less complex engineering
d. Significant past experience of both the engine type and fuels used
What is the purpose of a bipropellant?
Makes the fuel combustion process more efficient and energetic leading to an increase in torpedo endurance and top speed combined with a reduction to only 10% gaseous products
Describe SCEPS and its attributes
a. Stored Chemical Energy Propulsion System (SCEPS)
b. Closed loop steam turbine
i. No exhaust therefore quieter and depth independent
ii. High speed and long endurance generally providing better performance than current open cycle systems
iii. Highest energy density of all propulsion modes available to date; typically 3.42 kWh/kg
iv. Complex engineering in terms of fuel control system and overall engine construction requiring state of the art menufacturing process
v. Choice of fules : Lithium and Sodium hex-fluoride
c. Sulphur Hexafluoride is sprayed over a solid Lithium block to generate heat which is used to boil water through a heat exchanger to generate steam. This steam drives a turbine which in turn drives the propulsor through a gearbox. The used steam is then condensed back to water and remains in the loop.
What is the main risk with HTP which causes us to believe it has been the source of at least 2 major submarine accidents?
a. HMS SIDON 16 JUN 1955, KURSK 12 AUG 00
b. Volatile
c. In contact with a catalyst it decomposes into a high temperature mixture of steam and oxygen, with no remaining liquid water. Exothermic reaction
How can the rotational energy generated be transferred to the seawater and what is the most efficient way of doing so?
Using a propeller or propulsor ( propulsor is most efficient way to do so)
Describe the process by which the Shkval torpedo achieves supercavitation
a. Smaller starter motors ignire and accelerate the torpedo to cavitation speed (approx. 70m/s)
b. Nose of the torpedo features a canted disk with an elliptical shape termed the cavitator
c. Once natural cavitation occurs on the cavitator disk, some exhaust gases from motors fed back through the torpedo body and are forced out of ventilation ducts in the cavitator disk to force the natural cavitation bubbles which have forced to increase in size. Eventually, this cavitation bubble is increased in size to the extent that a gas cavity is created which surrounds the entire body of the torpedo and it is at this point supercavitation is achieved
d. Main engine ignites to accelerate the torpedo to great speeds achievable due to the massive reduction in drag
e. The cavitator disk is tilted forward at the top, which generates the lift needed to support the fore body of the device. About 2/3 back from the nose are four spring-out skids angled toward the stern which support the aft end of the torpedo by allowing it to bounce off the inner cavity surface.
What is the current main disadvantage with supercavitating weapons?
a. Travel only along a straight trajectory
B. Can’t alter course
What components make up a target’s FCS?
a. Bearing
b. Range
c. Course
d. Speed
e. Depth
f. Time
Why is underwater targeting usually more difficult than above water?
a. No dedicated fire control sensors
b. There is a lack of range information taken directly from sensors as Submarines are unlikely to transmit active sonar
What methods can be used to determine the range of a contact from a submarine?
a. Active sonar
b. Passive Sonar
i. Triangulation
ii. Vertical Direct Passive ranging VDPR
iii. Horizontal direct passive ranging HDPR
c. TMA Processing
d. Visual
What is meant by the tactical offset?
Air-launched engagement the ultimate aim is to release the torpedo such that it enter the water a set distance ahead of the target track
Describe all the errors inherent in airborne engagement
a. System Prediction Error
i. Accumulation of all the targeting errors
ii. FCS of the contact may not be entirely accurate
1) True target track different to assessed target track
b. Delivery error
i. Pilot error + ballistic error
Weapon Entry Error = System prediction error + Delivery Error
What is a TUA and why is it needed?
a. Target Uncertainty Area
b. To account for the errors and inaccuracies the FCS is centred in a TUA in order to guide the torpedo into an often elliptically shaped area in order for the torpedo to start homing to the most likely target
How long will the engagement take and will it be successful?
16 min
What is the difference between guidance and homing?
a. Guidance get the torpedo from the firing platform to the target area or TUA
b. Homing allows the torpedo to use its own sensors to locate the target and process it. Often done with a combination of active and passive sonar with the weapon balancing stealth and success.
What are the benefits and drawbacks of closed loop guidance over open loop guidance?
a. Closed loop receives feedback and is therefore guides
b. Open loop receives no feedback therefore unguided
c. Closed loop provide
i. High Single Shot Kill probability
ii. Complex/ expensive
iii. Susceptible to soft kill
iv. Less accurate TMA required
v. Less sensitive to target alterations
d. Open loop
i. Low SSKP
ii. Simple Cheap
iii. Increased resistance to soft kill
iv. Very accurate TMA required
Very sensitive to target alterations
Describe the different options available for guidance link and their advantages or disadvantages
a. Sonar Link
i. Speed of sound in water not suitable for medium for guidance control
ii. Open to jamming, corruption, mutual interference, oceanographic effect
iii. Counter-detection
b. Wire Guidance
i. Wire has limited bandwidth
ii. Low data rate
iii. Susceptible to breakages
iv. Wire can cause data transfer problems
c. Optical Fibre link
i. Very high data transfer rate
ii. High bandwidth capability
Issues with tensile strength
What initialisation data is required by guided weapons?
a. Weapon data
i. Floor depth, ceiling depth, flight profile speed
b. Target data
i. FCS and its accuracy, target type, altered to weapon presence or not
c. Torpedo spare data
i. Used during practice firings
d. Submarine Data
i.Position, roll, pitch, speed, depth
Describe the attributes of passive and active homing and the tactical considerations in their use
a. Passive allows to remain stealthy for as long as possible
i. Less Chance of success if target it quiet
b. Active too early alter the target of weapon and firing platforms presence
i. Result in rapid anti-torpedo manoeuvres
c. Active transmissions are less effective against anechoically coated modern submarines which scatter and reduce the transmission
d. Active Homing
i. Advantages
1) Effective against a quiet target
2) Accurate range information
3) Speed indication from doppler
4) Target depth for ASW attack
5) Self-noise resilient
ii. Disadvantages
1) Target alerted to weapon presence
2) Two-way propagation loss?
3) Reverberations due to high source levels
4) Susceptible to active countermeasures
e. Passive Homing
i. Advantages
1) Target unalerted to weapon presence
2) One-way propagation loss
3) No reverberations
ii. Disadvantages
1) Requires a noisy target for acquisition
2) No range information
3) No speed indication
4) Susceptible to passive countermeasures
5) Self-noise susceptible
What are the generic requirements of a torpedo discharge system?
a. Discharge the weapons safely and effectively into the water for the given platform
b. Provide a safe, secure stowage , meeting magazine safety requirements
c. Provide a means of monitoring the weapon status during stowage
d. Apply power to the weapon in the initial instance before the weapon’s battery is activated
e. Be able to communicate with the weapon to send pre-set initialisation data
f. A means of dispensing guidance wire and routing signals from control computers
Reloadable
What advantages does MTLS(Magazine Torpedo launch system) have over STWS (Ship torpedo weapon system)?
a. MTLS can be used in any seastate without risk to the crew as they do not have to manually reload the system outside
Crew were vulnerable to attack as they were exposed reloading it outside
What are the components of FIAM (Flight in air material)?
a. Suspension bands
b. Umbilical
c. Arming wire
d. Parachute pack
Nose cap
What additional requirements does an underwater discharge system have inclusive to the generic requirements listed previously?
a. Quiet as possible
b. Bubble free
Able to be used at any depth
What systems are used for Submarine Discharge?
a. Swim out
b. Compressed gas discharge
Water discharge
Explain with a basic diagram the key components and operation of a water Ram Discharge
a. Firing air from the air reservoir pushes the air ram cylinder back which is connected through the pressure hull to the water ram cylinder
b. On movement, the Water Ram cylinder pushes the water in the cylinder through the enclosed water transfer tank to enter the torpedo tube through the open Flap Valve
c. To Allow the water Ram cylinder to move it has a free flood follow up Water space on the opposing face such that the cylinder does not pull a vacuum
d. The water entering the tube is directed onto the rear end of the torpedo by the tube sleeve. This has the effect of pushing the torpedo out of the tube like a water operated piston
Once the torpedo has successfully left the tube, the Flap Valve will shut.
What are the key differences and advantages with the discharge system employed on the Astute class SSN?
a. Air Turbine Pump
b. Uses air to drive a turbine with drives an impellor through a gearbox
c. Air completely contained within the pressure hull
d. System can operate at any depth
ATP is quieter than WRD
To double the speed of a torpedo you need how much more power
8x more power due to v^3
Explain the Gas bubble effect in 5 stages
1.) Torpedo explodes under keel
2.) Shockwave causes lift of the ships hull causing stress fractures
3.) As shockwave dissipates, ship is lifted again by expanding gas. causes compression on the hull and tension on the super structure
4.) Gas bubble pulsates due to rapidly changing interval pressures and shrinks. Platform sags into void created. Hull is now in tension and superstructure in compression
5.) Bubble expands once at smallest size causing water jet + gas jet to vent through the ships hull
