BACKGROUND TO STUDY CASE

Transcription

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2 BACKGROUND TO STUDY CASE German Aerospace Center (DLR) is using Andøya Rocket Range for a sounding rocket campaign. On 27th October 2005 a 300 kg payload (SHEFEX) was launched Due do a technical problems it was not possible to recover the payload using a vessel positioned 22 nautical miles from the planned impact center. When the vessel arrived the calculated impact center, the payload had sunk. The impact zone is expected to be at N and E. Water depth at this position is estimated to be about 2700 m.

3 Rocket Payload Location

4 Proposed Methodology for the Literature Review Literature Review Project Case Study Case Study Weather Windows Weather Windows Concept/Theory Calculations AUV AUV Definition of AUV Functional, Type etc ROV ROV Definition of ROV Functional, Type etc Find a method for localizations and retrieving the payload and give a brief estimate of necessary weather windows for the payload retrieval operation. Retrieval Procedure Retrieval Procedure Options Options Retrieval Procedure Retrieval Procedure Summary and Summary and Conclusion Conclusion

5 WEATHER WINDOWS Marine Operations may always be affected and delayed by severe or even moderate weather conditions. Defined the operability of wave height for the operation (governed by design code such as DNV, NORSOK) Assumed and will be used for our operations

6 WEATHER WINDOWS Defined the probability of failure (Assumption : Seastate have the same probability of exceedance have the same duration of statistics) Payload was falling on October - winter season (the blue curve) Requirement : Hs=2m at least 24 hours H s =2m The CDF of Hs taken from Statfjord Design Basis

7 WEATHER WINDOWS Continued: P(Hs) = P(2.0) = 0.5 Means: 50% of the time we will have wave conditions with Hs below 2.0m Average duration of period with Hs below these thresholds (eq. 2.6 in Kompendium) = 26.5 hours τ c Introducing eq.2.11 and eq.2.4 (in Kompendium), and by setting duration of calm period 48 hours, we obtained : P(t) = P(48) = 0.63 Means: 63% of the time duration of calm period less than 48 hours. Overall Conclusion : Doing the operation in the month of October was not the best solution (in fact, worse) To improve the probability, there s no other way than making a proper planning before performed the operation such that we can finish it as earliest as possible.

8 AUTONOMOUS UNDERWATER VEHICLE (AUV) An unmanned torpedo vehicle (robotic) that has capability to explore the subsea without physical connection to the surface Can carry its own energy, battery and equipment (AUV payload) for certain mission

9 AUTONOMOUS UNDERWATER VEHICLE (AUV) Key issues to determine the characteristics AUV that we required Sensors or other hardware must the AUV carry as payload? Mission : Localize the rocket payload Basic equipment : AUV sonar sensor At what water depth will the AUV operate? Rocket payload was fallen in 2700 w.d. This will determine the thickness and construction of the compartments/hull At what speed will the AUV operate? Normally 3-5 knots Depend on the energy provided by the battery and the duration of the mission. For how long will the AUV operate? Depend on the speed, energy provided by the battery and the mission goals.

10 AUTONOMOUS UNDERWATER VEHICLE (AUV) Brief of Specs : Diameter : 27 in / 0.69 m Length : 21.4 ft / 6.5 m Max. depth : ft / 3500 m Weight in air : 3800 lb / 1720 kg Hull : Aluminum 7175-T74 Battery : 24.3 kwh lithium ion ISE Hydroplanes : 5 independent Thruster : brushless dc, oil compensated Cruise speed : 3.9 kts / 2.0 m/s Range at cruise : 80 nm / 149 km Maximum speed : 4.9 kts / 2.5 m/s Minimum speed : 1.9 kts / 1.0 m/s Payload Sensor : Seabird SBE19CTD Simrad EM /200kHz (Multibeam sonar) Marine sonic 600kHz (Sea Scan Sonar)

11 REMOTELY OPERATED VEHICLES (ROV)

12 REMOTELY OPERATED VEHICLES (ROV) An remotely vehicle (robotic) Required an operator on the vessel surface to operate the vehicle. Basically ROV consist of: - Cable links to provide the electric power and control commands (called thether, sometimes also with the TMS) - Deployment unit - The operator/pilot and control station on the surface ROV have operational phase: - Pre-launch preparation - Launching - Water entry - Transit to work site - Work site preparation - Transit form the work site - Hook-up, lifting, securing on the deck

13 REMOTELY OPERATED VEHICLES (ROV) Brief of ROV with TMS Operational Phase

14 REMOTELY OPERATED VEHICLES (ROV) Brief of specs (ROPOS) Type : Electro-Hydraulic Work-Class ROV Depth Capability : 5000 meters Dimensions : 1.75m x 2.6m x 1.45m Motor : 40 HP Thrusters : 2 fore-aft, 2 vertical, 2 lateral Camera Kraft Raptor lift at full extension) : 7 functions w/ force feedback (300lbs ISE Magnum extension) : 7 functions (600lbs lift at full Depth : Parascientific Altimeter : Kongsberg Simrad KHz Sonar : Simrad MS KHz digital sonar Weight : 5800 lbs With an operating depth of 5000 meters, this system configuration requires a 96,000 Lbs (43,636 Kgs) Winch and a 12,000 Lbs (5454 Kgs) cage.

15 Retrieval Concept Using Elevator Surface Ship Surface Ship Autonomous Elevator system Floats Elevator Steel weight Media ROV Cabled ROV system

16 Elevators are designed to descend to the ocean floor and return to the surface without a cable attached (autonomously). Before released from surface ship, it armed with a steel weight that makes the system sinks to the bottom. Navigator estimates where on the surface the elevator should be released so that it lands on the bottom nearby the site to be sampled. When sampling is complete, an acoustic signal is sent sub sea by the navigator that triggers a burn-wire release, the weight is dropped and the elevator returns to the surface. The elevator is recovered by the surface ship or by small boat. Steel weight stack and weight dropper

17 Framework of Elevator The top and the bottom sections of the elevator is permanently welded subassemblies. Four upright frames are added to complete the basic structure. The upper framework supports a number of floatation spheres. The top is smaller than the bottom to reduce drag and collapse. The spheres and the acoustic transponder are attached to the frame with stainless steel hose clamps. The Transponder communicates with a ship Transducer and an LBL (long baseline) navigation network to allow tracking by navigators. The transponder also has the ability to burn a wire and release the elevator s ballast weight. The lower framework section is made wide for some stability and increased drag. It normally consists of the sample baskets and bins, sampling devices, device triggers, manual pull pins, a burn-wire weight dropper and an expendable steel descent weight. Additional hose clamps and custom mounting hardware are screwed onto the lower frame to secure sampling devices. Lower framework with bin lids open

18 Deployment & Recovery procedure Deployments begin with the elevator secured to the deck by tie-downs. People on watch recheck to ensure that it has been properly tested and armed. The lift line of the crane will bear the load of the elevator as it is deployed. The crane takes the load, tie-downs are removed, tags are controlled, and the elevator is lifted, swung overboard and lowered until it is awash. The deck chief signals for the stainless pin to be yanked from the cat s cradle, the lift line slips from around the frame and the elevator leaves the surface on a steady descent toward the bottom. Elevators are rarely recovered after dark. The can be equipped with relocation devices such as a radio frequency (RF) beacon and strobe. For most recoveries a small boat is made ready with a tow line and launched prior to the released command being sent. The small boat crew will be responsible for towing the surface elevator back to the crane so they should be experienced and thoroughly briefed about the recovery operations.

19 SUMMARY AND CONCLUSION Weather will become our limitation Localized the position of the rocket payload in the seafloor using AUV with sonar system. Retrieved the rocket payload using a ROV with elevator.