Tutorial questions

Question 1

Why might a side impact torpedo be less affective against a modern surface target

Answer 1

a. More heavily armoured
b. Better water tight integrity
c. Better damage control systems

Question 2

How does a heavyweight torpedo employ its warhead to better effect against a surface target

Answer 2

Gas bubble effect

Question 3

Describe the key stages of a heavyweight torpedo detonation under a surface target

Answer 3

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

Question 4

Why might a larger payload be required to engage an SSBN over an SSN?

Answer 4

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

Question 5

How does a heavy weight torpedo employ its warhead to engage a submarine target?

Answer 5

Submarine Gas Bubble effect

Question 6

How does a lightweight torpedo employ its warhead to engage a submarine target?

Answer 6

Shapecharge

Question 7

What are the general requirements that a torpedo must fulfil to be successful?

Answer 7

a. At least 150% speed of target
b. Stealth
c. Depth
d. Safety
E. Endurance

Question 8

Name and describe the perfect torpedo hull form for minimal drag. Why is this not practical for military applications?

Answer 8

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

Question 9

How much more power is required to increase a torpedoes speed from 20kt to 50kt?

Answer 9

15.6

Question 10

What affects the choice of energy source for a torpedo and what choices are there?

Answer 10

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)

Question 11

What is the difference between a primary and secondary battery?

Answer 11

a. Primary is a one time use the electro-chemical reaction is not reversible
b. Secondary is rechargeable but has shorter endurance

Question 12

What propulsion system is fitted in spearfish and what fuels does it employ?

Answer 12

a. Propulsor , Sundstrand gas turbine , Open cycle gas turbine
b. Using OTTO fuel/ HAP (hydroxyl Ammonium Perchlorate)

Question 13

What are the advantages and disadvantages of an open loop thermal propulsion system?

Answer 13

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

Question 14

What is the purpose of a bipropellant?

Answer 14

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

Question 15

Describe SCEPS and its attributes

Answer 15

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.

Question 16

What is the main risk with HTP which causes us to believe it has been the source of at least 2 major submarine accidents?

Answer 16

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

Question 17

How can the rotational energy generated be transferred to the seawater and what is the most efficient way of doing so?

Answer 17

Using a propeller or propulsor ( propulsor is most efficient way to do so)

Question 18

Describe the process by which the Shkval torpedo achieves supercavitation

Answer 18

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.

Question 19

What is the current main disadvantage with supercavitating weapons?

Answer 19

a. Travel only along a straight trajectory
B. Can’t alter course

Question 20

What components make up a target’s FCS?

Answer 20

a. Bearing
b. Range
c. Course
d. Speed
e. Depth
f. Time

Question 21

Why is underwater targeting usually more difficult than above water?

Answer 21

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

Question 22

What methods can be used to determine the range of a contact from a submarine?

Answer 22

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

Question 23

What is meant by the tactical offset?

Answer 23

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

Question 24

Describe all the errors inherent in airborne engagement

Answer 24

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

Question 25

What is a TUA and why is it needed?

Answer 25

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

Question 26

How long will the engagement take and will it be successful?

Answer 26

16 min

Question 27

What is the difference between guidance and homing?

Answer 27

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.

Question 28

What are the benefits and drawbacks of closed loop guidance over open loop guidance?

Answer 28

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

Question 29

Describe the different options available for guidance link and their advantages or disadvantages

Answer 29

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

Question 30

What initialisation data is required by guided weapons?

Answer 30

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

Question 31

Describe the attributes of passive and active homing and the tactical considerations in their use

Answer 31

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

Question 32

What are the generic requirements of a torpedo discharge system?

Answer 32

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

Question 33

What advantages does MTLS(Magazine Torpedo launch system) have over STWS (Ship torpedo weapon system)?

Answer 33

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

Question 34

What are the components of FIAM (Flight in air material)?

Answer 34

a. Suspension bands b. Umbilical c. Arming wire d. Parachute pack Nose cap

Question 35

What additional requirements does an underwater discharge system have inclusive to the generic requirements listed previously?

Answer 35

a. Quiet as possible b. Bubble free Able to be used at any depth

Question 36

What systems are used for Submarine Discharge?

Answer 36

a. Swim out b. Compressed gas discharge Water discharge

Question 37

Explain with a basic diagram the key components and operation of a water Ram Discharge

Answer 37

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.

Question 38

What are the key differences and advantages with the discharge system employed on the Astute class SSN?

Answer 38

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

Question 39

To double the speed of a torpedo you need how much more power

Answer 39

8x more power due to v^3

Question 40

Explain the Gas bubble effect in 5 stages

Answer 40

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