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£&£81 > Name 4 of the 7 propulsion Modes > Flashcards

Name 4 of the 7 propulsion Modes Flashcards

1
Q

Name the main 5 of the 7 Propulsion modes?

A 
Turbo reduction
Turbo Electric
Battery 
Diesel electric
AIP

Diesel reduction and Diesel direct not used

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2
Q

What are the Advantages and disadvantages of Nuclear and Diesel

A
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3
Q

Define Sound

A

A periodic variation of pressure, particle displacement, or particle velocity in an elastic medium

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4
Q

Describe/ draw the 3 layer ocean model

A
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5
Q

Define a choke point

A

Choke points are a geographical feature above or below the surface that restrict the freedom of movement of a submarine

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6
Q

Give example of a choke point

A

Strait of Malacca
Straits of Gibraltar
English Channel

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7
Q

What are the three main requirements of a successful underwater detection system?

A

Good penetration/ sensitivity
High resolution
High data rate

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8
Q

Name the following components on turbo reduction system

A
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9
Q

What are three factors that effect speed of sound in water and what figures are attributed to them?

A

Temperature - 1oC increase = 3m/s increase

Pressure - 100m depth increase = 2m/s increase

Salinity 1pp thousand = 1.1m/s increase

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10
Q

Which of these factors has the greatest effect on speed of sound on water?

A

Temperature

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11
Q

Define the doppler phenomenon

A

Doppler is the apparent change in frequency due to relative motion between a source and a stationary receiver.

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12
Q

A submarine is detected at 405hz and drops 4hz before fading out. Assuming AV of 1500 work out the speed of the submarine?

A

1500 x (405-401)
———————— = 14.8kts
403

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13
Q

What does DIFAR stand for?

A

Directional Frequency Analysis & Recording (passive)

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14
Q

What are the variable depths and operating life associate with DIFAR?

A

90, 200, 400, 1000ft

0.5, 1, 2, 4 or 8 hrs

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15
Q

What does DICASS stand for?

A

Directional Command Activated Sonobouy System (active)

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16
Q

What is DICASS operating life and what are the associated depths

A

60 minutes / 50 ping seconds
D1: 50,150,300ft
D2: 90,400,1500ft

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17
Q

What 6 information can be gained from CPA? (Closest point of approach)

A 
f0
Depth
Speed
Range
Track
Bearing
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18
Q

What is HALT?

A

High Away Low Towards

In relation to SNELLS LAW - Sound is lazy and will bend away from areas of high velocity towards areas of low velocity

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19
Q

Draw the basic topography of the north Atlantic ocean

A
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20
Q

What are the NATO designators for Submarines and what is DSRV?

A

Deep sea rescue vehicle

SS on his own because he’s a nazi
BAG for nuclear
NCP for others
National Car Parks

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21
Q

What are the 2 types of seamounts?

A

guyots

pinnacle

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22
Q

Define ambient noise and what are the two types?

A

Ambient noise is defined as any noise within the ocean that is not target related.

  1. Man made
  2. Natural
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23
Q

State the man-made and natural sources of ambient noise

A
  1. Drilling (oil and gas)
  2. Shipping (merchant traffic/fishing)
  3. Active transmission (military/civilian)
  4. Seismic Surveys
  5. Biological
  6. Ice
  7. Seismic (volcanic activity /tectonic plates)
  8. Weather
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24
Q

What are 3 main types of bottom composition?

A

sand, rock, mud and silt

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25
Q

What are the 4 dimensions from a lofar gram?

A

colour
frequency
time
intensity

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26
Q

What are the 4 bottom types in order of reflectivity

A

Sand, Rock, mud/silt and ooze

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27
Q

To double in sound is an increase of how many dB?

A

3dB

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28
Q

To increase 5X in sound is how many dB?

A

7db

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29
Q

To increase 100 times in sound is how many dB?

A

20db

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30
Q

What is the difference between Active and passive?

A

Active is 2 way

Passive is 1 way

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31
Q

Spherical spreading decreases by how much when doubled?

A

6db

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32
Q

Cylindrical spreading decreases by how much each double?

A

3db

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33
Q

What is the Sonic Layer Depth? (SLD)

A

The MAXIMUM acoustic velocity (AV) over the first 1000ft of water

Normally SLD is the depth at the bottom of the mixed layer

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34
Q

Define the critical angle?

A

The steepest angle at which there is a 100% reflection from the bottom or surface

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35
Q

At what temperature is water most dense?

A

4oC

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36
Q

What percentage of the convergence zone is the annulus?

A

10%

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37
Q

Describe basic Ocean topography? And what are the two other names for seamounts/ridges

A

Guyots/pinnacles

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38
Q

Describe the snorting system

A
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39
Q

What are the 2 forms of propagation loss?

A

Spreading and Attenuation

40
Q

What are the two types of spreading and how do they differ?

A

Spherical Spreading dissipates in all directions. Decrease of 6dB when the distance is doubled

Cylindrical spreading is concentrated so sound decreases by 3dB when the distance is doubled

41
Q

What are the 4 types of attenuation?

A

Absorption
Scattering
Duct leakage
Deep scattering layer

42
Q

What are the convergence zone ranges in the North Atlantic and Mediterranean?

A

North Atlantic = 28 - 32nms

Mediterranean = 14 to 18nms

43
Q

What is the average velocity of sound in water?

A

1500m/s average

44
Q

What are the 4 reasons a submarine would surface?

A
  1. Snort/charge batteries
  2. Emergencies
  3. Attack solutions
  4. Communications
45
Q

What is wavelength?

A

One cycle of compression and rarefaction

46
Q

What is frequency?

A

The number of complete cycle waves passing a fixed point in one second.

47
Q

How is water depth measured and what are the figures associated?

A

Fathom = 6ft/2m

48
Q

Define reflection

A

sound energy up to 99% of which is reflected from the sea bed or surface

49
Q

Describe what’s happening and why?

A
50
Q

Describe what’s happening and why?

A
51
Q

Describe what’s happening and why?

A
52
Q

Describe what’s happening and why?

A
53
Q

What are the 5 sound propagation paths .

A 
Surface ducting 
Bottom Bounce
Convergence zone
Sound channels
Direct Path
54
Q

What temperature reduction is needed for iso conditions to occur when the depth increases

A

Decrease of 0.6oC

55
Q

Define ambient noise

A

Any background noise which is non target related

56
Q

What are the 5 sources of noise from a submarine?

A

Broad band - when received energy is spread over a wide spectrum and individual frequencies are not distinguishable

Broadband effect - caused by multiple paths of BB energy reflecting off the sea bed

Lloyds mirror - multiple paths of BB energy reflect off the surface allowing depth to be calculated

Narrow band - when revived energy is concentrate in one discrete spectrum

Transients - noise that occurs over a short or long term over irregular intervals

57
Q

What are the different types of propellor?

A 
Fixed pitch (tankers/cargo)
Controllable/Variable pitch 
Azipod (cruise liners/fast ferries)
Skewed (submarines)
Propulsor drive (military surface)
58
Q

What is the general blade and shaft fit of military vessels

A

Multi-shaft (up to 4) and usually 4-7 blades. 2 shaft / 5 blade most common

59
Q

What is the general blade and shaft fit of merchant vessels?

A

Single shaft, large vessels 4-7 blades, small & medium 3-4 blades

60
Q

What is the predominant frequency spectrum for blade and shaft?

A

0-70hZ

61
Q

Define blade rate

A

The number of times a blade passes a given point in 1 second (given in Hz)

62
Q

Define shaft rate

A

The number of times the shaft passes a given point in 1 second (given in hZ)

63
Q

What is a fundamental frequency?

A

It is the base or origin frequency measured in cycles per second and expressed in Hz

64
Q

What is a harmonic frequency?

A

It is an echo of the fundamental frequency (can be numerous echoes)

65
Q

What is the definition of CPA? (closest point of approach)

A

The point at which the vessel passes from high to low (F0) and the track of the vessel is at 90 degrees to the buoy.

66
Q

What is the frequency range of 4 stroke engines ?

A

Predominately 150Hz and above

67
Q

What is the frequency range of blade and shaft?

A

Predominately 0-70Hz

68
Q

What is the frequency range of 2 stroke engines?

A

Predominately 70-150Hz

69
Q

Define an ocean front

A

The boundary between to water masses of different thermal and velocity characteristics.

70
Q

What are ocean fronts divided into and how do they differ?

A

Semi-permanent - remain more or less static for long periods.

Temporary - temporary changes in ocean structure brought about by significant meteorological changes or tidal activity

71
Q

What are the effects of ocean fronts on sound propagation?

A

Propagation is poor, varies by as much as 25db

Causes significant errors in sonar bearings

72
Q

What are the size of ocean waves determined by?

A

Wind strength
Wind duration
Fetch (size of area)

73
Q

What are the sonobuoy sizes?

A

A, G, F

74
Q

What are the components of a sonobuoy?

A 
Housing
Flip plate and parachute
Aerial and flotation bag
Surface unit
Cable drunk/compliant cable
Strum net and damper 
Hydrophone
75
Q

What are the two types of beam forming?

A

Cardioid (Bum)

Limacon (turtle head)

76
Q

What pilot frequency does a DIFAR transmit?

A

7.5khz

77
Q

What is the channel separation of a DIFAR and what channels are/aren’t available?

A

375khz separation

1-99 except 57,58 and 93)

78
Q

What are the characteristics of a bathy buoy?

A

Measure temp vs depth
12 mins life
2624ft depth
5ft/sec sink rate

79
Q

DIFAR can be programmed to what modes of operation?

A 
Omni-directional
Pseudo-Omni or POM (default)
Null 
Automatic noise cancel
Look
80
Q

What are the 3 types of Gram Displays?

A

Full band
Main band
Vernier

81
Q

How can a DIFAR be affected?

A

1) Bouy wash over
2) The speed at which a contact passes the buoy
3) Poor signal to noise ratio
4) Biasing

82
Q

What are the two mediums on which DIFAR is displayed?

A

BCP (bearing coherent processing)

Gram

83
Q

What are noise sources associated with Fishing vessels?

A 
Exhaust flutter
Trawl Noise
In/out
Shaft rub
Blade Flutter
Diesel roar
84
Q

What are noises associated with Merchant vessels?

A 
In/out
Shaft rub
Flutter
Slap
Cav 
Constant RPM
85
Q

What is absorption?

A

Loss by molecular action

86
Q

What is aliasing?

A

A term used to describe the mirror imaging of a frequency. To combat aliasing the sampling rate needs to be double the bandwidth.

87
Q

What are factors affecting detection by a sonobuoy?

A 
DCT - Data Collection Time
Resolution
IT - Integration Time
Frequency
History
Normalisation
88
Q

What is the relationship between Data Collection Time (DCT) and resolution?

A

Res = 1 / DCT or DCR = 1 / Res

89
Q

What is the Passive Sonar Equation?

A

Signal Excess = Source Level - Prop Loss - Ambient Noise - Recognition Differential - Directivity Index

SE = SL - PL - AN - RD - DI

90
Q

What is the median detection range (MDR)?

A

The range at which there is a 50% probability of detection on a single sonobuoy.

91
Q

What are the characteristic of mimic and wader?

A

Mimic = Low Freq 50, 60, 120Hz

Wader = High Freq 180, 300, 500Hz

92
Q

Define Signal Excess

A

The amount of signal in dBs available for detection

93
Q

Diesels engine diagram

A
94
Q

Primary coolant loop

A
95
Q

What are the three types of AIP?

A

Mesma, fuel cell, Stirling

£&£81 (11 decks)

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