Aeroship: A Hybrid Flight Platform for Planetary Flight,

Near-Space Flight and Personal Flight

Tianshu Liu, W. W. Liou, & M. Schulte

Department of Mechanical and Aerospace Engineering

Western Michigan University, Kalamazoo, MI 49008

Motivations

• Originally, the concept of aeroship (hybrid flight

vehicle) is proposed for designing a low-speed flight

vehicle with very short-takeoff/landing (STOL)

capability on Mars.

• Then it is found that aeroship is particularly suitable

to personal flight and high-altitude (near-space) flight

in the Earth atmosphere.

Conventional Flight Platforms

Aerostatic Force vs. Aerodynamic Force

The non-dimensional parameter: a ratio between the

aerodynamic force and total weight

W/)LW(W/W shipA

1A 0A

Grey or Fuzzy

Domain

10 A

Opportunities in a “Fuzzy” Parametric Domain

Optimum Equilibrium between

Aerostatic Force & Aerodynamic Force

for Challenging Flight

10 A

• Short takeoff/landing on a small open area (30-50 m)

Requirements for Personal Flight Vehicle:

• Good maneuver and easy control (level turn in 5 m)

• Reasonable cruising speed (50 km/h)

• Always soft landing in emergency situations

Generic Aeroship Configurations

Personal Aeroship

Airship module +

Wing/propulsion module

Generic Aeroship Configurations

High-Altitude Unmanned Aeroship

Generic Aeroship Configurations

Flapping-Wing Aeroship

Aeroship Force Equilibrium

Level Flight Climb

Gliding Level Turn

Relevant Physical Quantities and Parameters

)2/SU(CVgCL wing

2

LshipL wingship

The total lift of aeroship:

The total drag of aeroship:

)2/SU(C)2/SU(CD wing

2

Dship

2

D wingship

wingship DSDwing

2

D CRC)2/SU/(DC

The total drag coefficient:

wingshipS S/SR

The characteristic area and force ratios:

)]C/C(R1/[1wingship LLFA

A relation between the characteristic parameters:

)2/SU/(gVR wing

2

shipF

Aeroship Flight Performance

Thrust and Power for Steady Flight

2

wing

2

wing

0,DSDwing

2

RS

W

U

SK2)CRC)(2/SU(DT

wingship

The thrust required for level flight:

2/1

wing0,D

)T(S

W

C

K2U

minR

The velocity at the min thrust required for level flight:

3

Lwing

2

D

3

DL

RRCS

CW2

C/C

UWUTP

The power required for level flight:

The velocity at the min power required for level flight: 2/1

LF

2

L

2

F0,Dwing)C/C(

shipship

maxD2/3

L CRCR4K/C3

1

S

W2U

Aeroship Flight Performance

Maximum Lift-to-Drag Ratio

KC/241.1)D/L( 0,D2max

Optimum condition:

K/C761.0)CR( 0,DopLF ship

The velocity at max L/D: 2/1

wing0,D

)D/L(S

W

C

K2891.0U

max

Aeroship Flight Performance

Comparison with Aircraft on L/D

0,wingship DDSaircraftmax,

aeroship,2max

C/CR1

482.2

)D/L(

)D/L(

The max L/D:

0,wingship DDS

aircraftL

aeroshipLC/CR1257.1

)C(

)C(

The lift coefficient at the max L/D:

0,wingship DDSaircraftmax,)D/L(

aeroshipmax,)D/L(

C/CR1

891.0

U

U

The velocity at max L/D:

Aeroship Flight Performance

Climb

wing

2

21

wing

0,D

2

wing S

W

U

cosK2

S

WC

2

U

S

TUsinUC/R

The climb rate:

wing

2

21

wing

0,D

2

wing

pr

S

W

U

cosK2

S

WC

2

U

US

Psin

The climb angle:

2

wingwingpr S

W

)S/P(

K4U

max

The velocity at the max climb angle:

Aeroship Flight Performance

Gliding

The sink velocity:

The stall velocity:

wing

2

D

3

L

VS

W

C/C

2U

wing

W

W

C

C

U

U

wingD

D

aircraft,V

aeroship,V

Stall

wingmaxLFL

stallS

W

])C(RC[

2U

wingship

2/1

maxLLFaircraft,stall

aeroship,stall

)C/(CR1

1

U

U

wingship

Aeroship Flight Performance

Level Turn

2

0,D

wing

min

)W/T/(KC41)W/T(g

)S/W(K4R

The min level turn radius:

)W/T(

)S/W(K4U

wing

Rmin

The velocity at the min level turn:

Free Falling Velocity

2shipDship

VCS

W2U

Lake of Michigan

Conceptual Design of Personal Aeroship

Aeroship Component Mass

Wing 24 kg

Engine 40 kg

Propeller 3 kg

Instrument & wires 4 kg

Tails 9 kg

Fuselage 60 kg

Airship hull 30 kg

Pilot 80 kg

Total mass 250 kg

Mass Estimate

Intrinsic design parameters

Total weight (Newtons) 2450

Airship lift (Newtons) 1479.8

Wing area (m2) 12

Wing aspect ratio 5.3

Wing span efficiency 0.8

Airship characteristic area (m2) 14.25

Airship vertically projected area (m2) 40

Airship volume (m3) 144

Wing parasite drag coefficient 0.02

Airship drag coefficient 0.04

Wing lift coefficient 0.6

Maximum wing lift coefficient 1.4

Airship drag coefficient in free fall 1.2

Atmosphere density (kg/m3) 1.225

Helium gas density (kg/m3) 0.1785

Design Parameters

Climb Performance Compared with Aircraft

Max R/C

Climb Angle at Max R/C

Level Turn Performance Compared with Aircraft

Min Level Turn Radius

Speed at Min Level Turn

Takeoff Ground Roll Compared with Aircraft

Intrinsic Performance Parameters Aeroship Aircraft

U at the min thrust (m/s) 11.79 25.41

max L/D 17.43 12.90

U at the max L/D (m/s) 16.70 25.41

CL at the max L/D 1.19 0.51

U at the min power required (m/s) 14.64 19.31

CL at the min power required 1.55 0.894

CD at the min power required 0.164 0.08

The min power required (watts) 3807.08 4233.45

U at the max R/C (m/s) 14.64 19.31

glide angle (deg) 8.95 4.48

Uv, sink velocity, in gliding (m/s) 2.33 1.85

U stall (m/s) 8.52 15.43

Uv, sink velocity, in free fall (m/s) 5.74 -

Personal Aeroship Performance Parameters

High Altitude or Near-Space Aeroship

• Short takeoff/landing

• High lift-to-drag ratio

• Good maneuverability

• Low engine power required (solar powered)

Altitude:

> 30 km (100,000 ft)

Conceptual Design of High-Altitude Aeroship

Airship Component Mass

Airship hull 48 kg

H2 gas 5.5 kg

Wing/propulsion 36 kg

Payload 30.5 kg

Total mass 120 kg

Intrinsic Design Parameters

Total weight (Newtons) 1176

Airship lift (Newtons) 705.6

Wing area (m2) 30

Wing aspect ratio 7.5

Wing span efficiency 0.8

Airship characteristic area (m2) 136.2

Airship vertically projected area (m2) 514.5

Airship volume (m3) 4247

Wing parasite drag coefficient 0.02

Airship drag coefficient 0.04

Wing lift coefficient 0.6

Maximum wing lift coefficient 1.4

Airship drag coefficient in free fall 1.2

Atmosphere density (kg/m3) 0.0183

Gas density (kg/m3) 0.00128

Altitude for cruise (m) 30000

Mass Estimate Design Parameters

Parametric Variations with Altitude (without releasing the light gas)

Normalized Pressure Difference

Across the Hull Skin Airship Volume Lift

Parametric Variations with Altitude (with suitable initial gas mass and releasing the gas later)

Normalized Effective Gas Volume

Airship Lift

Climb Trajectory of High-Altitude Aeroship

Altitude with Horizontal Distance

Altitude with Time

High-Altitude Aeroship Performance Parameters

at Altitude of 30 km

Intrinsic Performance Parameters

U at the min thrust (m/s) 29.61

max L/D 12

U at the max L/D (m/s) 41.72

CL at the max L/D 2.45

U at the min power required (m/s) 36.48

CL at the min power required 3.21

CD at the min power required 0.44

The min power required (watts) 5880.14

U at the max R/C (m/s) 36.48

glide angle (deg) 20.2

Uv, sink velocity, in gliding (m/s) 19.63

U stall (m/s) 15.93

Uv, sink velocity, in free fall (m/s) 9.11

Model Aeroship and Flight Testing Design Parameters

Total Weight, W, (N) 19

Gas Envelope

Volume (m3) 1.08

Gross Buoyancy Lift (N) 13.3 (70% W)

Weight of Envelope (kg) 0.48

Front-Projected Area (m2) 0.98

Vertical-Projected Area (m2) 1.5

Max. Length (m) 2.3

Max. Diameter (m) 1.1

Horizontal Fin Area (m2) 0.25

Vertical Fin Area (m2) 0.126

Wing Parameters

Wing Section NACA4312

Span (m) 1.52

Chord (m) 0.203

Wing Area (m2) 0.309

Vertical Tail Parameters

Cross-Section flat plate

Area (m2) 0.053

Rudder Area (m2) 0.053

Vertical Tail Volume 0.102

Horizontal Tail Parameters

Cross-Section flat plate

Area (m2) 0.155

Elevator Area (m2) 0.155

Horizontal Tail volume 2.09

Videogrammetry in Flight Testing

Two-camera videogrammtric

system

Intensity-inversed image

Takeoff Performance

Rate of Climb Speed in Takeoff

Landing Performance

Rate of Climb Speed in Landing

Short Climb Performance

Rate of Climb Speed in Climb

Glide Performance

Rate of Climb Speed in Glide

Level Turn Performance

Left Turn Right Turn

Parameter Estimated Measured in Flight

Takeoff Ground Roll 5 m 3 m

Takeoff Speed 4.6 m/s 4.2 m/s

Approach Angle in Landing 15 deg 16.7 deg

Touch-Down Speed in Landing 4.6 m/s 3.3 m/s

Max. R/C 3.1 m/s 2.5 m/s

Angle at Max. R/C 30 deg 32.3 deg

Velocity at Max. R/C 6.1 m/s 4.5 m/s

Descent Rate in Glide 2.3 m/s 1.4 m/s

Glide Angle 15.4 deg 19.4 deg

Stall Speed 4.2 m/s 4.2 m/s

Min. Level Turn Radius 5.5 m 3.6 m (left), 5.3 m

(right)

Comparison between Predicted and Measured

Performance Parameters

The 24-foot Airship Model in Flight

Conclusions

• Short takeoff/landing (STOL)

• High lift-to-drag ratio

• Good climb and turn performance

• Low engine power required

• Emergency safety

Aeroship is an optimized integration of airship module

and wing/propulsion module