FALL 2009

PROJECT AIRNAUTILUS

Statement of Need

Assure that the U.S. maintains its tactical advantage for future coastal insertion missions

(ref: DARPA BAA-09-06)

Motivation

Objective System

AirNautilus

Final Design Layout

Operating Environment

Carry up to eight personnel with equipment~113 kg per person = ~900 kg total

Carry an additional 900 kg of cargo

Cruise altitude ~5,200 meters

Tactical approach altitude ~5-10 meters

Requirements

Sea state five conditions 21-25 knot winds Wave height 2.5-3.7 meters Average period 5.5-7 seconds Average wave length 32-48 meters

Submersing one atmosphere (~10 meters) to avoid detection

Land on water

Communications

Communication

Penetration ability of wave with various frequencies into sea water

Antenna design to operate as a submarine as well as an aircraft

Communication

Attenuation of wave into water• Electrical conductivity • Fresh water = 0.01 S/m• Sea water = 4 S/m

• Skin depth =

Sea water• Thick electrical conductor, RF don’t travel well• Non-magnetic material

Balance between:• Penetration and antenna length

Communication

Types of submarine antennaHI-Q-4/2-30 Mast

• Short HF 2-30 MHZ• ¼ wave length antenna• Fully encapsulated for

environmental protection• h=50”, d=5.94”, m=18 lbs

• Lower mast (drive motor 24 VDC)• upper mast (Re-entrant Coaxial Cap-hat)• loading coil (movable continuously tuned

in 2-30MHz range),• antenna controller

Communication

Types of submarine antennaBuoyant cable• VLF/LF/MF/HF

(10 KHz - 35 MHz)• l=610-730m, d=0.01651m,

specific gravity=1.19kg/m• Just for receiving when

at max depth (1 way comm.)• Slow transmission rate

~ few characters per minute

Communication

Air Craft Antenna• VHF communication is light-of-sight• One antenna at the top-one at the bottom

VHF Civil Aviation Band (108 to 136.975 MHz)• BW = 18.975 MHz• ≈ 2.2 m

Fiberglass Rigid Antenna • Good Voltage Standing Wave Ratio (SWR)• ¼ wave antennas• Coax cable

• Must be 50 Ω coax (for aircraft)• inner wire and an outer braid or shield• outer braid is also ‘earths’, which suppresses

outside interference

• BNC connector (light, weather proof)• Radio

Electrical

Transition

Start electric motorSeal all water entry pointsShut down turbo-fan engines Perform nitrogen purge of turbo-fan enginesFlood turbofans with fuelFlood the wings with surrounding sea waterIncrease motor RPM to 75% of total powerCheck battery charge status

Reduce motor to idle (10%) Switch main power source to electric motorVerify electrical system operationVerify sife support systems are operationalPresurize cockpitSlowly Submerge

Transition

Electrical Schematic

Underwater Travel: Electrical

Powering the aircraft

According to our research we found that the aircraft needed 50kW while submerged, safety factor included

Total amount of power required for underwater operation both ways assuming we take 10 hours is 500kW

A Reliance Baldor 1000HP electric motor will power the propellers

The motor will draw power from an array of batteries

Number of batteries on board: 44k

Underwater Travel: Propeller

Prop was optimized to find basic prop needs: 5 knot Speed 300 kW per prop 1000 RPM 0.5 Gearbox Reduction Ratio 28 cm Diameter 0.61 m Pitch 56% Slip Four blades for smaller diameter

Resurfacing

Resurfacing

Longitudinal Stability The longer after-body as compare to fore-body will maintain

longitudinal stability by adding adequate canard moment arms

Lateral Stability Two water skis on the tips of each wing are providing;

Lateral stability to submersible aircraft Weather-vane to face wind when at rest, or during taxiing at low speed

Stability

Miscellaneous

Propulsion

Water Landing: Impact Force

Aircraft weight: 266,893.297 N (60,000

lbs)

Descent Rate: -3.5 meters per second

normal to water

Vertical Speed Stop Time: 1 second

Pressure: 3.418 kN/m2

Force: 95.25 kN

Submersion

Static Diving Ballast tanks

For our aircraft specifications Fb = 207 kN 21000 kg of water 20.57 m3

Single hull design 22m3 of free space for

our components

Corrosion

Titanium Alloy Ti-6Al-4V (Grade 5) 90.0% Ti, 6.0% Al, 4.0% V, 0.25% Fe, 0.20% O Often used in airframes, blades, fasteners Great corrosion resistance Density: 4.43 g/cm3

Thickness: 3 mm

Ti-6Al-4V blisk manufactured for the JSF

Conclusions

Future Work