B-3 “Wraith” Strike BomberA Next Generation Long Range Supersonic Bomber

Kevin Boldt, Mike Dobben, Amar Dzubur, Alex Landis, Connor McGuire

Business Case Overview

Mission Goals● Increase the effective max takeoff weight by 36% from the B-1’s value of 477,000 lbs to our max

takeoff weight of 650,000 lbs allowing us to carry a larger payload● Aircraft will ideally be able to cruise at low supersonic speeds (around Mach 1.2)● Cruise at 50,000 ft● Have an effective mission radius of at least 3,000 miles

○ Example mission would be from Ramstein AFB in Germany to a conflict region in the Middle East, Baghdad for reference. This would require a 2100 mile radius + loiter time.

● Stealth is a priority

Mission Plan

Take Off

Ascent

Cruise (50,000 ft) Cruise (50,000 ft)

Payload Drop (15-20,000 ft)

Descent

Landing

Reference Engine Selection

Kuznetsov NK-321Cruise Thrust: 31,000 lbf (137 kN)Maximum Thrust with AB: 55,000 lbf (245 kN)Pressure Ratio: 28.4Bypass Ratio: 1.4TSFC: .72 kg/hour in Subsonic flight, 1.70 kg/hour in Supersonic flightThrust to Weight Ratio: 7.35 kgf/kgTurbine Inlet Temperature: 1630 K (1357 C)Mass Flow Rate: 805 lbm/s

Length: 181 in. (460 cm)

Diameter: 55 in. (140 cm)

Dry weight: 4,400 lbf (1995 kg)

Compressor: Axial, 2 stage fan, 9 stage high pressure compressor

Combustors: Annular

Turbine: 1 stage high pressure turbine, 2 stage low pressure turbine

Maximum power output: 31,000 lb (138 kN) (with afterburner)

Overall pressure ratio: 26.8:1

Specific fuel consumption: 2.46 lb/lbf-hr (max thrust)

Thrust-to-weight ratio: 7.04:1 (afterburner)

GE F101 Engine Specifications

Engine Characteristics

Physical DimensionsLength - 304.8 in / 7.74 mDiameter - 73.0 in / 1.85 mWeight - 12096.8 lbf / 53.8 kNMass Flow Rate - 1298.4 lbm/s

PerformanceTotal Max Uninstalled Thrust (4 Engines) - 322580 lbf / 1434 kNThrust/Weight (at TO) - 0.496

Engines Cont.● The fully scaled engines produce a total amount of uninstalled thrust equivalent to 322,580.65lbf

with afterburners for takeoff. ● With this amount of thrust, we were able to increase our fully loaded takeoff weight from 477,000lb

to 650,000lb. ● This represents an increase of 36 percent, well beyond our initial goal of a 20 percent increase. ● The other brilliant characteristic that our engines facilitate is that based upon the mission

requirements, this plane can perform as an excellent Long Range aircraft, while also exhibiting certain STOL characteristics during takeoff.

● Historically required values for the thrust to weight ratio for various missions are as follows:

Engines Cont.● If we utilize full afterburners for takeoff and landing, we are able to achieve a thrust-to-weight ratio of

.496, putting us squarely in the middle of the range for STOL aircraft.● Furthermore if we then decide to not utilize our afterburners during cruise conditions, we are able to

achieve a thrust-to-weight ratio of .307, also putting us in the middle of the range for a long range aircraft.

● What happens to be of note is that although our scaled engine has increased in length and diameter by 27%, the thrust output of the engine increased by 61% in cruise thrust and 59% in maximum afterburner thrust.

Wing Design● Initial research showed that to achieve the high amounts of lift we require with a supercritical airfoil

(for efficient supersonic flight) a large Aspect Ratio (AR) wing would be needed.● At takeoff conditions:

■ Dynamic Pressure at sea level = q = 7546 kg/m^3■ Takeoff Velocity - 111 m/s | 248 mph■ Weight = 2545 kN

● Our wing design will require that at these conditions a CLmax value that can lift the weight of the aircraft + payload off the ground

XFLR Model of Wing & Body

GeometryWing Span- 48mWing Area- 1013 m^2Root Chord- 50mMAC- 26.1Tip Twist- -1.2°AR base- 2AR tip- 14Taper Ratio- 25Root-Tip Sweep- 59°

AerodynamicsCLmax (Takeoff)- 1.0CLmax (Cruise)- 0.82Cd (Cruise)-0.113

Body PortionWing Characteristics

● Symmetric airfoil produces lift at angle of attack for takeoff

● low aspect ratio

Root Portion

Wing Characteristics● small but important portion● low aspect ratio● introduces camber● blends wing into body

airfoils

Main Airfoil Portion

Wing Characteristics● thin airfoil with camber● large aspect ratio● sweep of 50 degrees sees

an incoming mach of 0.7 at cruise of 1.2

Wing Tip Portion

Wing Characteristics● supercritical airfoil with

small camber● large aspect ratio● Twist allows wingtips to

stall first

Active Lift Devices for Takeoff● To increase the takeoff CLmax of the plane trailing edge (TE) single slotted

flaps were added to help get the aircraft off the ground.● For takeoff the B-3 will use a 10° flap deflection and can increase the Clmax

to a value of 1.2

Take Off

Fuselage● Utilizing a blended wing body to get the most aerodynamic shape to reduce

the amount of flow separation.● Given the size of the aircraft more lift is required so using a blended fuselage

allows for the body to contribute to the lift.● With a blended body there is less wasted space and an opportunity for more

payload

Stability & Control● In order to prevent instability while dropping

payload, the bombs will be loaded such that the center of gravity is located at the aerodynamic center of the wings.

● This point will also be the center of gravity after bombs have been dropped.

● This was done to avoid a pitching moment as there is no horizonal stabilizer to balance out the lift from the main wing.

Stealth Considerations

Low Engine Profile- embedded inlets and shielded nozzles reduce detection

Special Paint-Low emissivity paint reduces infrared cross section at engine nozzle

Stealth Considerations

Material SelectionInternal Frame - Titanium & Aluminum

-Need lightweight and strong materials

Wing Skin - Composite materials- For light weight and directional

structural integrity

Engine - Titanium, Ni-base, Steel-Normal engine materials, Titanium for

cold section, Ni-base for hot section.

Cost Estimation per AircraftAirframe Engineering 400,750,000

Development Support 50,000,000

Manufacturing Labor 200,000,000

Manufacturing Materials 400,000,000

Tooling 2,000,000

Quality Control 10,000,000

Engine 280,000,000

Profit 57,250,000

Total Cost/Aircraft 1,400,000,000

B-1b Lancer 1 billion

B-2 Spirit 1.1 billion

Resources Used1) Microsoft Excel 2) XFLR3) Autodesk Inventor

References1) Corke, Thomas C. Design Of Aircraft. Upper Saddle River: Pearson Education, 2003. Print.

2) Nicolai, Leland M., and Grant E. Carichner. Fundamentals of Aircraft and Airship Design. Vol. 1. Reston: American

Institute of Aeronautics and Astronautics, 2010. 2 vols. Print

3) Yechout, Thomas R., Steven L. Morris, David E. Bossert, Wayne F. Hallgren, and James K. Hall. Introduction to

Aircraft Flight Mechanics: Performance, Static Stability, Dynamic Stability, Classical Feedback Control, and State-

Space Foundations. 2ndnd ed. Reston: American Institute of Aeronautics and Astronautics, 2014. Print.

Questions?