1. GLOBAL CONSTELLATION OF
STRATOSPHERIC SCIENTIFIC
PLATFORMS
Presentation to the NASA Institute of
Advanced Concepts (NIAC)
by
Kerry T. Nock
Global Aerospace Corporation
November 9, 1999
Global
Aerospace Corporation

2. Global Stratospheric Constellation
Global
Aerospace Corporation TOPICS
• CONCEPT OVERVIEW
• EARTH SCIENCE OVERVIEW
• CONSTELLATION MANAGEMENT
• TRAJECTORY CONTROL
• BALLOON
• GONDOLA
• INTERNATIONAL CONSIDERATIONS
• PHASE 2 PLAN
• SUMMARY
Global Aerospace Corporation 2 KTN - November 9, 1999

3. CONCEPT OVERVIEW

4. Global Stratospheric Constellation
Global
Aerospace Corporation BENEFITS OF
STRATOSPHERIC CONSTELLATIONS
TO NASA
• Provide low-cost, continuous, simultaneous,
global Earth observations options
• Provides in situ and remote sensing from very
low Earth “orbit”
Global Aerospace Corporation 4 KTN - November 9, 1999

5. Global Stratospheric Constellation
Global
Aerospace Corporation
CONCEPT DESCRIPTION
• Tens to Hundreds of Small, Long-life Stratospheric
Balloons or StratoSats
• Uniform Global Constellation Maintained by Trajectory
Control Systems (TCS)
• Flight Altitudes of 30-35 km Achievable With Advanced,
Lightweight, Superpressure Balloon Technology
• Gondola and TCS Mass of 235 kg at 35 km Altitude
• Goal of ~50% Science Instrument Payload of Gondola
Global Aerospace Corporation 5 KTN - November 9, 1999

6. Global Stratospheric Constellation
Global
Aerospace Corporation CONCEPT SCHEMATIC
Global Constellation StratoSat Flight System
~40-50 m dia.
Super-pressure
Gondola
Dropsonde
10-15 km
Balloon
StratoSail™
Trajectory Control
System (TCS)
30-35 km
Flight Altitude
Rel. Wind
0.3-10 m/s
Possible
Science
Sensors
~50-100 kg
Rel. Wind
5-50 m/s
Global Aerospace Corporation 6 KTN - November 9, 1999

7. Global Stratospheric Constellation
Global
Aerospace CorporationRATIONALE FOR STRATOSATS
• High Cost of Space Operations (Spacecraft and
Launchers) Relative to Balloon Platforms
• Advanced Balloons Are Capable and Desirable High
Altitude Science Platforms
• In Situ Measurement Costs Are Reducing With the
Advance of Technology (Electronics Miniaturization,
Sensor Advances)
• There is an Emerging and Widely Accessible Global
Communications Infrastructure
• Balloons Fly Close to the Earth and Are Slow, Both
Positive Characteristics for Making Remote Sensing
Measurements
• A Constellation of Balloon Platforms May Be More Cost
Effective Than Satellites for Some Measurements
Global Aerospace Corporation 7 KTN - November 9, 1999

8. Global Stratospheric Constellation
Global
Aerospace Corporation KEYS TO THE CONCEPT
Affordable, Long-duration Stratospheric
Balloon and Payload Systems
Lightweight, Low Power Balloon Trajectory
Control Technology
Global Communications Infrastructure
Global Aerospace Corporation 8 KTN - November 9, 1999

9. EARTH SCIENCE OVERVIEW

10. ESE STRATEGIC PLAN GOALS
Expand scientific knowledge
of the Earth system . . . from
the vantage points of space,
aircraft, and in situ platforms
• Understand the causes and consequences of land-cover/land-use
change
• Predict seasonal-to-interannual climate variations
• Identify natural hazards, processes, and mitigation strategies
• Detect long-term climate change, causes, and impacts
• Understand the causes of variation in atmospheric ozone
concentration and distribution

11. Global Stratospheric Constellation
Global
Aerospace Corporation PROMISING EARTH
– Climate Change Studies SCIENCE THEMES
• Water Vapor and Global Circulation in the Tropics*
• Radiative Studies in the Tropics:
• Global Radiation Balance*
– Ozone Studies
• Mid-latitude Ozone Loss
• Arctic Ozone Loss*
• Global Distribution of Ozone*
– Weather Forecasting
• Hurricane Forecasting and Tracking
• Forecasting Weather from Ocean Basins & Remote Areas
– Global Circulation and Age of Air
– Global Ocean Productivity
– Hazard Detection and Monitoring
– Communications for Low Cost, Remote Surface Science
* Discussed further in later charts
Global Aerospace Corporation 11 KTN - November 9, 1999

12. CLIMATE CHANGE: GLOBAL
RADIATION BALANCE
40
30
km
20
10
0
Stratosphere
Cloud LIDAR
Detector
System
Laser
System
Tropopause
Troposphere
Rotatable
Detector
&
Filter
Data
Acquisition
Pyronometer
© Global Aerospace Corporation
-90 -60 -30 Equator 30 60 90

13. CLIMATE CHANGE: DYNAMICAL
PROCESSES IN TROPICS
40
30
km
20
10
0
in situ TDL Water, Ozone & CO2
Absorption Measurement Cell
Source Beam
Detector
Stratosphere
Air
Flow
Large-scale
Ascent
Tropopause
Subsidence
Troposphere
Microwave
Temperature
Profiler
Scanning
Mirror
Ozone &
Water
Vapor
LIDAR
Laser
System
Cal Target LO
Mixer Detector
mwave
Detector
System
© Global Aerospace Corporation
-90 -60 -30 Equator 30 60 90

14. OZONE STUDIES: GLOBAL
DISTRIBUTION OF OZONE
40
30
km
20
10
0
Stratosphere
Meteorology N2O and T, P
Science Pods
Every 2-3 km, T, P
Tropopause
Cross
Tropopause
Exchange
Troposphere
Dropsondes
H2O, O3, CH4,
© Global Aerospace Corporation
-90 -60 -30 Equator 30 60 90

15. OZONE STUDIES: POLAR OZONE LOSS
318.5 GHz
Streerable
Reflector
Plate
Limb FTIR Mid-latitude Air
Multipass Absorption Cell
Scattered Light Partical Detector
FTIR
Sun
Tracker
Camera
Fore
Optics
T, P
70 80 Pole 80 70
40
30
20
10
Stratosphere
Troposphere
Mixing
Region
km
Polar Vortex
4445 km
Measures: Aerosols
Air
Flow
Source
Beam
Detector
Measures: HCl, CH4, N2O, O3
Air
Flow
Source
Beam
Detector
Vortex
Edge
Interferometer
FXST
Optics
Polar Stratospheric
Clouds (PSCs)
FTIR / SLS Limb Scan Geometry Submillimeter
Emission
Limb
Scanner
Harmonic (SLS)
Mixer
Gunn
Oscillator
Data
Handling
Limb
Radiation
640 GHz
IF Spectral
Analysis
SLS
© Global Aerospace Corporation
665 km
35 km

16. Global Stratospheric Constellation
Global
Aerospace Corporation SURFACE REMOTE SENSING
7200 m/s
• At 30 km a StratoSat Platform Is >30 times Closer
to the Earth’s Surface Than Sun-synchronous LEO
Satellites
• The Ground Speed of a 30 km StratoSat Is a Factor
of >140 times Slower Than LEO Satellites (angular
rates over nadir are >2 times less)
• A Constellation of Stratospheric Balloons Can
Observe the Entire Earth at the Same Time
30-45 km
1000 km
<50 m/s
Global Aerospace Corporation 16 KTN - November 9, 1999

17. CONSTELLATION MANAGEMENT

18. GLOBAL CONSTELLATION WITHOUT
TRAJECTORY CONTROL
ASSUMPTIONS
• 100 StratoSats @ 35 km
• Simulation Start: 1992-11-10
• UK Met Office Assimilation
• 4 hrs per frame
• 4 month duration
STATISTICS
1000
800
600
400
200
0
Start Date: 1992-11-10T00:00:00
35 km constant altitude flights
100 balloons, UKMO Environment
0 20 40 60 80 100 120
[km]
s
NNSD
Time from start [days]

19. Global Stratospheric Constellation
Global
Aerospace Corporation CONSTELLATION
GEOMETRY MAINTENANCE
• Balloons Drift in the Typical and Pervasive Zonal
Stratospheric Flow Pattern
• Trajectory Control System Applies a Small, Continuous
Force to Nudge the Balloon in Desired Direction
• Balloons Are in Constant Communications With a Central
Operations Facility
• Stratospheric Wind Assimilations and Forecasts Are
Combined With Balloon Models to Predict Balloon
Trajectories
• Balloon TCS Are Periodically Commanded to Adjust
Trajectory Control Steering to Maintain Overall
Constellation Geometry
Global Aerospace Corporation 19 KTN - November 9, 1999

20. ILLUSTRATION OF CONTROL
EFFECTIVENESS
5 m/s Toward Equator 5 m/s Toward Poles

21. Global Stratospheric Constellation
Global
Aerospace Corporation MAINTENANCE STRATEGIES
• Environment Information Used
– Successive Correction Data (Interpolated Measurements)
– Assimilations (Atmospheric Model Tuned by Actual Measurements)
– Forecasts (Can Be Used for “Look-ahead” Decision-making)
• Level of TCS Model Fidelity
1. Omni-directional Delta-v of Fixed Amount Applied at StratoSat
2. Delta-v Proportional to True Relative Wind at TCS
3. Actual TCS Aerodynamic Model and Sophisticated TCS Control
Algorithms
• Network Control Algorithms
– Randomization: Move StratoSats North or South Randomly
– “Molecular” Control: Each Balloon Responds Only To Its Neighbor
– Macro Control: Entire Network Is Managed, Balloons Are Moved
Between Zones
• Cyclone Scale Coordinates for Control Algorithms
Global Aerospace Corporation 21 KTN - November 9, 1999

22. GLOBAL CONSTELLATION WITH
SIMPLE, INTELLIGENT CONTROL
ASSUMPTIONS
• 100 StratoSats @ 35 km
• Simulation Start: 1992-11-10
• UK Met Office Assimilation
• 4 hrs per frame
• 4 month duration
• 5 m/s control when separation
is < 2000 km
• Same initial conditions
1000
800
600
400
200
0
STATISTICS
Start Date: 1992-11-10T00:00:00
35 km altitude flights
100 balloons, UKMO Environment
Free-floating
Paired NS and
Zonal Control
0 20 40 60 80 100 120
[km]
s
NNSD
Time from start [days]

23. TRAJECTORY CONTROL

24. Global Stratospheric Constellation
Global
Aerospace Corporation FEATURES OF
STRATOSAIL™ TCS
· Passively Exploits Natural Wind Conditions
· Operates Day and Night
· Offers a Wide Range of Control Directions Regardless of
Wind Conditions
· Can Be Made of Lightweight Materials, Mass <100 kg
· Does Not Require Consumables
· Requires Very Little Electrical Power
· Relative Wind at Gondola Sweeps Away Contaminants
Global Aerospace Corporation 24 KTN - November 9, 1999

25. Global Stratospheric Constellation
Global
Aerospace Corporation ADVANCED TRAJECTORY
CONTROL SYSTEM
Advanced Design Features
– Lift force can be greater than weight
– Will stay down in dense air
– Less roll response in gusts
– Employs high lift cambered airfoil
– Greater operational flexibility
ULDB Dynamically-scaled
ULDB Dynamically-scaled
Model Flight Test
Model Flight Test
Global Aerospace Corporation 25 KTN - November 9, 1999

26. BALLOON

27. Global Stratospheric Constellation
Global
Aerospace Corporation BALLOON DESIGN OPTIONS
Spherical Envelope
• Spherical Structural Design
• High Envelope Stress
• High Strength, Lightweight Laminate Made of Gas Barrier Films
and Imbedded High Strength Scrims
• Multi-gore, Load / Seam Tapes
Pumpkin Envelope
• Euler Elastica Design
• Medium Envelope Stress
• Lightweight, Medium Strength Films
• Lobbed Gores With Very High Strength PBO Load-bearing
Tendons Along Seams
Global Aerospace Corporation 27 KTN - November 9, 1999

28. Global Stratospheric Constellation
Global
Aerospace Corporation BALLOON VEHICLE
DESIGN
Baseline Balloon Design
• Euler Elastica Pumpkin Design
• 68,765 m3, 59/35 m Eq/Pole Dia.,
Equivalent to 51 m dia. Sphere
• Advanced Composite Film, 15 mm
thick, 15 g/m2 Areal Density
• 140 gores each 1.34 m Max Width
• Polybenzoxazole (PBO) Load
Tendons At Gore Seams
• Balloon Mass of 236 kg
Global Aerospace Corporation 28 KTN - November 9, 1999

29. SOLAR ARRAY / BALLOON
INTEGRATION
Sphere Pumpkin
Seam/Load
Tape as
Solar Array
Gore Center
As
Solar Array
Envelope Film
Seam/Load Tape / Solar Cells
(~ 3 cm wide)
Envelope Film
Thin Film Amorphous Si
Solar Array Cells
(~30 cm wide)
Example Power
• 48 m dia Spherical Design
• 100 Gores/Seams
• 3 cm Wide Solar Array
• 10 % Efficiency
• 4.7 kW

30. GONDOLA

31. Global Stratospheric Constellation
Global
Aerospace Corporation STRATOSAT GONDOLA
StratoSat Gondola
• Example Climate Change
Science Payload
• 2x1x0.5 m warm electronic
box (WEB) with louvers for
daytime cooling
• Electronics attached to
single vertical plate
• LIDAR telescopes
externally attached to WEB
• TCS wing assembly (TWA)
stowed below gondola at
launch before winch-down
• Science pods on tether
Stowed Gondola
Global Aerospace Corporation 31 KTN - November 9, 1999

32. INTERNATIONAL OVERFLIGHT
CONSIDERATIONS

33. Global Stratospheric Constellation
Global
Aerospace Corporation INTERNATIONAL OVERFLIGHT
• Current Scientific Balloon Program
– Overflight Often Allowed Especially If No Imaging and If Scientists
of Concerned Countries Are Involved
– Not All Countries Allow Overflight and This List Changes
Depending on World Political Conditions
• Treaty on Open Skies - Signed By 25 Nations in 1992
– Establishes a Regime of Unarmed Military Observation Flights Over
the Entire Territory of Its Signatory Nations
– First Step of Confidence Building Security Measures (CBSM)
• Future Political Climate
– Global Networks Can Build on World Meteorological Cooperation
– World Pollution Is a Global Problem Which Will Demand Global
Monitoring Capability
– First Steps Need to Be Important Global Science That Does Not
Require Surface Imaging
Global Aerospace Corporation 33 KTN - November 9, 1999

34. PHASE II PLAN

35. Global Stratospheric Constellation
Global
Aerospace Corporation PHASE II PLAN
• Constellation Management
– Control of Distributed Systems in Chaotic Environments Research
– Develop Advanced Constellation Geometry Control Algorithms
– Integrate Balloon Model, Environment and Advanced TCS Models
and Control Algorithms in Constellation Simulations and Analysis
• Advanced Trajectory Control
– Develop Control Models and Design Concepts
• Advanced Balloon Design
– Materials Research
– Structural and Thermal Design
– Envelope Design and Fabrication Technology
• Science Applications Development
– Proof-of-Concept Flight Definition - A Logical Next Step
– Broaden Search for New Earth Science Concepts
Global Aerospace Corporation 35 KTN - November 9, 1999

36. SUMMARY

37. Global Stratospheric Constellation
Global
Aerospace Corporation SUMMARY
• The StratoSat Is a New Class of in Situ Platform Providing:
– Low-cost, Continuous, Simultaneous, Global Observations Options
– In Situ and Remote Sensing From Very Low Earth “Orbit”
• Global Stratospheric Constellations Will Expand Scientific
Knowledge of the Earth System
• Broader Involvement of the Earth Science Community Is
Encouraged and Sought in the Definition of Constellation
Mission and Instrument Concepts
• A Proof-of Concept Science Mission Is One Essential First
Step on the Path Toward Global Stratospheric
Constellations
Global Aerospace Corporation 37 KTN - November 9, 1999

38. APPENDIX

39. Global Stratospheric Constellation
Global
Aerospace Corporation STEPS TO GLOBAL STRATO-SPHERIC
CONSTELLATIONS
Constellation Types / Locale
– Regional
• South Polar
• Tropics
• North Polar
– Southern Hemisphere
– Global
• Sparse Networks for Wide
representative Coverage
• Dense Networks for Global
Surface Accessibility
Measurements Types
– In Situ & Remote Sensing of
Atmospheric Trace Gases
– Atmospheric Circulation
– Remote Sensing of Clouds
– Atmospheric State (T, P, U, Winds)
– Radiation Flux
– Low Resolution Visible & IR
Surface and Ocean Monitoring
– High Resolution Surface Imaging
and Monitoring
A First Step Is a Proof-of-concept Science Experiment
Using Soon to Be Available ULDB Technology
Global Aerospace Corporation 39 KTN - November 9, 1999

40. Global Stratospheric Constellation
Global
Aerospace Corporation STRATOSAT FLIGHT
SYSTEM DESCRIPTION
Flight System Design Features
• Sample Payload for Climate Change
Studies in Tropics
• 68,800 m3 Pumpkin balloon
• 5 kW capable integrated solar array
• Telecom capable of 6 Mb/s
• Advanced TCS
• Tethered science pods
Mass Summary
Subsystem Mass, kg
Balloon 236
Helium 87
Power 19
Telecomm 5
Mechanical 30
Guidance & Control 1
Robotic Controller 1
Trajectory Control 81
Science 56
Science Reserve 44
Total 560
Global Aerospace Corporation 40 KTN - November 9, 1999

41. Global Stratospheric Constellation
Global
Aerospace Corporation HOW THE TCS WORKS
• Winds vary with altitude
– Balloon at 30 km
– Wing at 20 km
– Relative wind velocity
~15 m/s
• Wing generates lift force
Altitude,
km
– “Lift” force is horizontal
– force is transmitted by tether to balloon
– balloon drifts relative to local air mass
– balloon drag » wing lift
40
30
20
10
0
15 m/s
Alice Springs,
January, 24¡ S
Fairbanks,
July, 65¡ N
Source: Randel, W.J.,
Global Atmospheric Circulation
Statistics, 1000-1 mb,
NCAR/TN-366+STR, Feb. 1992
-40 -30 -20 -10 0 10 20
• Wing is in much denser air than balloon
Mean Zonal Wind, m/s
– 25km : 35km (5x); 20km : 35km (10x)
– equivalent wing area increased relative to balloon
Global Aerospace Corporation 41 KTN - November 9, 1999

42. Global Stratospheric Constellation
Global
Aerospace Corporation HOW THE TCS WORKS,
CONTINUED
TCS
LIFT mode
TOP VIEW OF TCS
TCS
STALL mode
a a Fh q
q
Stall Point
Fh
Lift/Drag Polar: Contours of
Feasible Aerodynamic Forces
Fh
Vrel
LIFT / DRAG FORCE POLAR
Vrel
1.5
1.0
0.5
0
Fh
q
0 10 20 30 40 50 60 70 80 90
Alpha
CL
LIFT vs ANGLE OF ATTACK
Global Aerospace Corporation 42 KTN - November 9, 1999

43. Global Stratospheric Constellation
Global
Aerospace Corporation HOW THE TCS WORKS,
CONTINUED
Vcross
Vdrift
Vrel
Vtrue
V b
VTCS
} Expanded Vector Diagram
Vrel
L
D
Fh
f
Balloon
TCS
Tether
Fdrift ~ Fh
Vdrift =
2 * Fdrift
r * Ab * CD ( )1/2
b = f - tan-1(D/L)
Vcross=Vdrift * Cos b
b
Top View
Global Aerospace Corporation 43 KTN - November 9, 1999

44. Global Stratospheric Constellation
Global
Aerospace Corporation
ANGLES EXAGGERATED &
FORCES NOT TO SCALE
FB
qB ~ 0.25¡
FBV ~ 16,000 N
FBH ~ 70 N
GONDOLA
AT 35 km
qG ~ 0.4¡
FT
l 1
l 2
WG ~ 15,000 N
qT ~ 4¡
FT
L ~ 70 N
LV ~ 5 N
WTCS ~ 1000 N
Global Aerospace Corporation L + W = - FT
44 KTN - November 9, 1999
SYMBOLS
T -> TETHER
G -> GONDOLA
B -> BALLOON
H -> HORIZONTAL
V -> VERTICAL
W -> WEIGHT
F -> FORCE
L -> LIFT
qT ~ 4¡
TCS
AT 20 km
BALLOON
ASSUMPTIONS
¥ BALLOON DRIFT ~ 2 m/s
¥Ê0.6 million m3 BALLOON
¥ GONDOLA ~ 1500 kg
¥ TCS ~ 100 kg
l 1 = 2 l 2
LIFT OF ~ 70 N
REQUIRES TCP WING
AREA OF ~ 16 m2
ASSUMING CL of 1.0
ULDB TCS
FORCE
DIAGRAM