A Next Generation Self- Locating Datum Marker Buoy

Transcription

1 A Next Generation Self- Locating Datum Marker Buoy A smaller, more easily deployed and faster reporting SLDMB Gary Williams and Eugene Zeyger Clearwater Instrumentation, Inc. 5/13/2011 Clearwater Instrumentation, Inc. 1

2 Outline Why do we need SLDMBs? Considerations in specifying and SLDMB. SLDMB dynamics on the ocean surface. Making an A-size A SLDMB. GPS data and data collection. 5/13/2011 Clearwater Instrumentation, Inc. 2

3 Why an SLDMB? Finding missing people or assets in the ocean is a daunting task. The first location reported by a distress call or emergency beacon is soon outdated when attempting to predict the location of floating objects. Winds, currents and waves will move and disperse them. Without specific knowledge of in situ ocean surface conditions, predicting dispersion is next to impossible. 5/13/2011 Clearwater Instrumentation, Inc. 3

4 Design Approaches to the SLDMB There are at least two ways to specify an SLDMB: By similarity. Make the SLDMB resemble the objects being tracked. For example, by varying the drag shape below the waterline. Measure the surface current. The SLDMB is designed to accurately follow the part of the water column it inhabits. Drift characteristics are inferred by superimposing special shape considerations upon the current field. 5/13/2011 Clearwater Instrumentation, Inc. 4

5 The Current-Following SLDMB Surface current circulation models assimilating tides, meteorology and current offer our best approximations for dispersion on the ocean surface. An accurate current following SLDMB can provide a calibrating response for circulations and accurate information on site conditions. FVCOM Mass Bay Model 5/13/2011 Clearwater Instrumentation, Inc. 5

6 5/13/2011 Clearwater Instrumentation, Inc. 6

7 Forces Applied to Drifting Objects Above the sea surface winds blow against a floating object. Exposed surface area and shape (drag coefficient) determine the strength of those forces. Any object extending into the ocean surface layer will be dragged by them. These currents arise from tides, wind stress and long term, large scale circulations. Superimposed on those currents are the cycloidal, periodic motions of surface waves. 5/13/2011 Clearwater Instrumentation, Inc. 7

8 Dynamics of a Floating Object Physical attributes Shape, drag area Mass distribution, inertia Fluid density Drag coefficients Expression of forces Above the surface: wind drag forces Below the surface: buoyancy, water drag forces and wave pressure 5/13/2011 Clearwater Instrumentation, Inc. 8

9 Dynamics of a Floating Object If the surface is absolutely still and the object is motionless, the object is in static equilibrium. The center of buoyancy is directly above the center of mass. Static Equilibrium 5/13/2011 Clearwater Instrumentation, Inc. 9

10 Dynamics of a Floating Object The sea surface is never in this ideal state: the wind blows, waves disturb the surface and currents flow. Perturbed away from static equilibrium, the object is vertically accelerated by buoyancy forces. 5/13/2011 Clearwater Instrumentation, Inc. 10

11 Dynamics of a Floating Object The volumetric shape of the object determines the buoyancy force as a function of submergence. For a vertically symmetrical object the buoyancy varies as the volume along the axis 5/13/2011 Clearwater Instrumentation, Inc. 11

12 Buoyancy-Volume Relationship 5/13/2011 Clearwater Instrumentation, Inc. 12

13 Responses to Displacements from Static Equilibrium: Heave (and Heave Frequency) Displaced from static equilibrium the floating object is acted upon a buoyancy force, heave. For a simple volume such as a cylinder, buoyancy changes linearly moving away from equilibrium (either positively or negatively). The restoring force gradually changes and yields a slower return toward equilibrium. The heave frequency is low. For realistic cylindrical drifters, spar buoys, the natural heave frequency is often in the spectrum for wind waves. Consequently, wind waves often excite heave in these drifters leading to rectification of wave energy into buoy translation. 5/13/2011 Clearwater Instrumentation, Inc. 13

14 Responses to Displacements from Static Equilibrium: Heave (and Heave Frequency) For a complex shape such as a sphere floating at its equator at equilibrium, buoyancy changes are maximum near the equator. Small displacements are subject to strong restoring forces; for realistic spherical drifters the heave frequency is high compared to the wind wave spectrum. Spherical drifters generally exhibit damped response to wind waves. 5/13/2011 Clearwater Instrumentation, Inc. 14

15 Some Adverse Consequences of Heave Wave energy rectification. Variability of wetted surface. Water drag force varies as wetted surface varies. Vertical currents shear and wave pressure will act differently as the wetted areas changes. Since the net effect will not sum to zero over a wave cycle, the drifter will be accelerated or retarded relative to current motion. If the drifter closely follows the surface, it will favor minimizing the average force over a wave period. 5/13/2011 Clearwater Instrumentation, Inc. 15

16 Drag Area and Inertia A drifter is propelled along with a current by the drag force it exerts; this force is proportional to the wetted cross-sectional sectional area and its characteristic drag coefficient. It is desired that the drag forces be large compared to drifter inertia. Drift is the extent to which a drifter lags behind the average current. This usually is stated to be one-half the depth of the drifter. 5/13/2011 Clearwater Instrumentation, Inc. 16

17 The CODE Drifter The CODE drifter design has so far been the best design to optimize requirements for minimizing adverse forces and thus reduce slip. A slightly negatively buoyant hull contains electronics and battery. Dihedral drag planes provide a large wetted area; the shape is approximately axially symmetric. Positive buoyancy is imparted by floats connected by flexible lines to the end of the upper spars supporting the drag planes. Hull and drag planes are suspended from these floats. 5/13/2011 Clearwater Instrumentation, Inc. 17

18 The CODE Drifter Distributed buoyancy keeps drifter parallel to the surface by providing large righting torque. Since the float lines are flexible, they stay on the surface when tilt might raise them off the surface. Large effective surface are for large drag force compared to inertia. Shape is close to symmetric. 5/13/2011 Clearwater Instrumentation, Inc. 18

19 CODE Drifters 5/13/2011 Clearwater Instrumentation, Inc. 19

20 Littoral Drifter Variety of CODE Close Up 5/13/2011 Clearwater Instrumentation, Inc. 20

21 Littoral Drifter Variety of CODE Distance 5/13/2011 Clearwater Instrumentation, Inc. 21

22 ClearSat-1 1 in Water 5/13/2011 Clearwater Instrumentation, Inc. 22

23 First USCG SLDMB Specification 7/10 CODE drifter. The CODE drifter has 1 m square drogue planes. To reduce the size of the drifter the drogue planes are.7 m GPS location Argos data transmission 5/13/2011 Clearwater Instrumentation, Inc. 23

24 The Deployment Challenge This is a good drifters but do you want this on the deck in the wind or to throw out of aircraft at 150 kts? The challenge is to accomplish self- reversing oragami: : fold the drifter into a compact shape that self deploys into its original form. 5/13/2011 Clearwater Instrumentation, Inc. 24

25 Clearwater SLDMB Compact form achieved by articulating drogue spars and spring mounting the antenna. Air deployment system to decelerate after drop and ensure vertical entry into the water. 5/13/2011 Clearwater Instrumentation, Inc. 25

26 SLDMB-I Large size takes up space in storage areas of restricted size. Non-standard deployment package. Each deployment venue requires a deployment method and certification for safe handling. Argos 5/13/2011 Clearwater Instrumentation, Inc. 26

27 SLDMB-III Goals Standard package size and deployment. This is achieved by a deployment system that uses an A-size A sonobuoy launch system. Elimination of data latency: receive data a soon as it is available. Iridium SBM messaging can deliver SLDMB location information within minutes. 5/13/2011 Clearwater Instrumentation, Inc. 27

28 SLDMB-III Design Challenges CODE design must fit into a much smaller package that weighs less and have a weight distribution similar to an A-size A sonobuoy Air deploy safely then unfold once in the water Begin operating immediately Iridium GPS location and SBD data transmission Limited volume for electronics and batteries 5/13/2011 Clearwater Instrumentation, Inc. 28

29 Data Requirements 10 minute GPS locations sent by SBD for the first 24 hours (rapid SAR mode) 30 minute GPS locations sent by SBD for the next 24 hours (standard SAR mode) 30 minute GPS locations sent by SBD every 3 hours for the remainder of buoy life (scientific mode) 5/13/2011 Clearwater Instrumentation, Inc. 29

30 Clearwater SLDMB Specifications Launch Air launch from A-Size A Sonobuoy tube Air launch from rotary wing aircraft Launch from any water craft Features Iridium SBD messaging. Latency in minutes Water activated electronic operation. Immediate notification of activation by SBD 20 channel GPS Data Day 1. GPS time and position and SBD every 10 minutes Day 2. GPS time and positions and SBD every 30minutes Day 3 and beyond. GPS time and position every 30 minutes, SBD message every 3 hours. 5/13/2011 Clearwater Instrumentation, Inc. 30

31 A Smaller, Lighter SLDMB SLDMB II is a CODE drifter The SLDMB II fully deployed Deployed weight: 8.5 lbs. (3.9 Kg) 5/13/2011 Clearwater Instrumentation, Inc. 31

32 Clearwater SLDMB Features Size A Sonobuoy compatible. Fits A-Size A sonobuoy launch container. Iridium SBD data transmission for near real time data return and data latency of minutes. Water-sensitive electronics activation. Life: 1 week 5/13/2011 Clearwater Instrumentation, Inc. 32

33 SLDMB is light Hull including electronics and antenna. Weight: 8.3 lbs. 5/13/2011 Clearwater Instrumentation, Inc. 33

34 SLDMB is Rugged All components and battery mechanically secured for shock and vibration protection. 5/13/2011 Clearwater Instrumentation, Inc. 34

35 SLDMB Self-deploys Clearwater technology developed for the first SLDMB has been perfected in Mod II. SLDMB II self- deploys from compact form to CODE configuration. 5/13/2011 Clearwater Instrumentation, Inc. 35

36 SLDMB Packed Configuration Drogue panels and antenna collapse for compact packaging. 5/13/2011 Clearwater Instrumentation, Inc. 36

37 SLDMB Air Deployment System During launch from aircraft Sonobuoy tube SLDMB II is contained within the Deployment System Cylinder. Air speed is diminished and entry angle is managed by deployment parachute on the DSC. SLDMB II is ejected from the DSC by a water- activated CO 2 life preservation inflation system. The ADS fits inside a standard Sonobuoy Launch Container. 5/13/2011 Clearwater Instrumentation, Inc. 37

38 SLDMB Air Deployment System SLDMB deployment system with parachute on top end of DCS tube. Parachute is packed into the top of the DSC and is pulled out after it exits the SLC by extractor flaps attached to the parachute. 5/13/2011 Clearwater Instrumentation, Inc. 38

39 SLDMB Parachute SLDMB parachute is securely fixed to the outside of the DSC. 5/13/2011 Clearwater Instrumentation, Inc. 39

40 SLDMB CO2 Extraction System Safety floatation system actuator for CO 2 pressure release. Actuator is enclosed to prevent accidental activation from mist, rain, splashing. CO 2 gas pressure expels wrapped SLDMB from DSC. 5/13/2011 Clearwater Instrumentation, Inc. 40

41 SLDMB Compatible with SLC 5/13/2011 Clearwater Instrumentation, Inc. 41

42 SLDMB Easy to Handle 5/13/2011 Clearwater Instrumentation, Inc. 42

43 Self-Deployment 5/13/2011 Clearwater Instrumentation, Inc. 43

44 Air Deployment 5/13/2011 Clearwater Instrumentation, Inc. 44

45 Air Deployment - 1 5/13/2011 Clearwater Instrumentation, Inc. 45

46 Air Deployment - 2 5/13/2011 Clearwater Instrumentation, Inc. 46

47 Air Deployment - 3 5/13/2011 Clearwater Instrumentation, Inc. 47

48 Air Deployment - 4 5/13/2011 Clearwater Instrumentation, Inc. 48

49 Air Deployment - 5 5/13/2011 Clearwater Instrumentation, Inc. 49

50 Air Deployment - 6 5/13/2011 Clearwater Instrumentation, Inc. 50

51 Air Deployment - 7 5/13/2011 Clearwater Instrumentation, Inc. 51

52 SLDMB Data Drifter Tracks Data latency Argos Iridium SBD 5/13/2011 Clearwater Instrumentation, Inc. 52

53 Newfoundland 5/13/2011 Clearwater Instrumentation, Inc. 53

54 Day 1 10 min. GPS and SBD 5/13/2011 Clearwater Instrumentation, Inc. 54

55 Day 1 and 2-30 min. GPS SBD 5/13/2011 Clearwater Instrumentation, Inc. 55

56 All Including 30 min GPS 3 hr. SBD 5/13/2011 Clearwater Instrumentation, Inc. 56

57 Argos Data Latency 5/13/2011 Clearwater Instrumentation, Inc. 57

58 Iridium SBD Data Latency 5/13/2011 Clearwater Instrumentation, Inc. 58

59 CODE, SLDMB, SLDMB Next Gen Characteristics CODE Mass, 10 kg Cross-sectional sectional area, 1 m 2 Inertia:drag,, 10:1 Drogue center,.5 m +.3 m SLDMB (7/10ths CODE) Mass, 8 kg Cross-sectional sectional area, 0.7 m 2 Inertia:drag,, 11:1 Drogue center,.35 m +.3 m SLDMB Next Gen (A-Size) Mass, 4 kg Cross-sectional sectional area, 0.4 m 2 Inertia:drag,10:1 Drogue center,.3 m +.15 m 5/13/2011 Clearwater Instrumentation, Inc. 59

60 Conclusions A CODE type drifter has been reduced to fit into an A-A size sonobuoy form factor. The potential exists for an SLDMB congruent in form and mass distribution that is certifiable for numerous aircraft. Storage and handling will be indentical. Good rapid GPS locations are expected with today s technology. Iridium SBD provides nearly real time access to drifter GPS locations. Improvements in GPS satellite data transmitters allow enhanced performance (more data) with a smaller package. 5/13/2011 Clearwater Instrumentation, Inc. 60

61 Acknowledgments C-Core Core for funding support Canadian Coast Guard for testing at sea Canadian Forces testing at sea and air drop testing. 5/13/2011 Clearwater Instrumentation, Inc. 61