Nock nov99

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

Global Aerospace

Global Stratospheric Constellation

Corporation

• • • • • • • • •

TOPICS

CONCEPT OVERVIEW EARTH SCIENCE OVERVIEW CONSTELLATION MANAGEMENT TRAJECTORY CONTROL BALLOON GONDOLA INTERNATIONAL CONSIDERATIONS PHASE 2 PLAN SUMMARY

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CONCEPT OVERVIEW

Global Aerospace

Global Stratospheric Constellation

BENEFITS OF STRATOSPHERIC CONSTELLATIONS TO NASA Corporation

• Provide low-cost, continuous, simultaneous, global Earth observations options • Provides in situ and remote sensing from very low Earth “orbit”

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Global Aerospace

Global Stratospheric Constellation

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

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Global Aerospace Corporation

Global Stratospheric Constellation

CONCEPT SCHEMATIC StratoSat Flight System

Global Constellation

~40-50 m dia.

Super-pressure Balloon

Gondola

30-35 km Flight Altitude Rel. Wind 0.3-10 m/s

Dropsonde

10-15 km

StratoSail™ Trajectory Control System (TCS)

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Possible Science Sensors ~50-100 kg

Rel. Wind 5-50 m/s

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Global Stratospheric Constellation Global AerospaceRATIONALE FOR STRATOSATS Corporation

• 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

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Global Aerospace Corporation

Global Stratospheric Constellation

KEYS TO THE CONCEPT

Affordable, Long-duration Stratospheric Balloon and Payload Systems Lightweight, Low Power Balloon Trajectory Control Technology Global Communications Infrastructure

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EARTH SCIENCE OVERVIEW

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

Global Aerospace

Global Stratospheric Constellation

Corporation

– Climate Change Studies

PROMISING EARTH 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

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CLIMATE CHANGE: GLOBAL RADIATION BALANCE Stratosphere

Cloud LIDAR Detector System

Detector & Filter Data Acquisition

30

Pyronometer

Laser System

km

Rotatable

20

o Tr

e s u pa o p

10 Troposphere 0 -90

-60

-30

Š Global Aerospace Corporation

Equator

30

60

90

CLIMATE CHANGE: DYNAMICAL PROCESSES IN TROPICS 40

Detector System

in situ TDL Water, Ozone & CO 2 Absorption Measurement Cell

30

Ozone & Water Vapor LIDAR Laser System

Source Beam

Air Flow

Detector

Microwave Temperature Profiler

km Stratosphere 20 Subsidence

Large-scale Ascent

Cal Target

Scanning Mirror

LO Mixer

e s u pa o op r T

Detector

µwave

10 Troposphere 0 -90

-60

-30

© Global Aerospace Corporation

Equator

30

60

90

40

OZONE STUDIES: GLOBAL DISTRIBUTION OF OZONE

30 Stratosphere km 20

Meteorology Science Pods Every 2-3 km, T, P

e s u pa o op r T Cross Tropopause Exchange

10

Troposphere 0 -90

Dropsondes H2O, O3, CH4, N2O and T, P

-60

-30

Š Global Aerospace Corporation

Equator

30

60

90

OZONE STUDIES: POLAR OZONE LOSS FTIR Fore Optics FXST Optics

Submillimeter Emission Limb Radiation Limb 640 GHz Scanner Harmonic (SLS) Mixer

FTIR / SLS Limb Scan Geometry

Streerable Reflector Plate

Interferometer

Sun Tracker

IF Spectral Analysis

318.5 GHz

35 km

Camera Data Handling

40

665 km

Gunn Oscillator

Mid-latitude Air

FTIR SLS

km 30

Vortex Edge

Multipass Absorption Cell Measures: HCl, CH 4 , N2 O, O3

T, P

Stratosphere

Source Beam

Air Flow

Detector

Limb

Scattered Light Partical Detector Measures: Aerosols

Polar Vortex

Source Beam

Air Flow

Detector

20

4445 km

Polar Stratospheric Clouds (PSCs)

Mixing Region

10

Troposphere

Š Global Aerospace Corporation

70

80

Pole

80

70

Global Aerospace Corporation

Global Stratospheric Constellation

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 1000 km rates over nadir are >2 times less) • A Constellation of Stratospheric Balloons Can Observe the Entire Earth at the Same Time <50 m/s 30-45 km

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CONSTELLATION MANAGEMENT

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

σ

NNSD

[km]

800 600 400

Start Date: 1992-11-10T00:00:00 35 km constant altitude flights 100 balloons, UKMO Environment

200 0 0

20

40 60 80 Time from start [days]

100

120

Global Aerospace Corporation

Global Stratospheric Constellation

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

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ILLUSTRATION OF CONTROL EFFECTIVENESS

5 m/s Toward Equator

5 m/s Toward Poles

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Global Stratospheric Constellation

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

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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

STATISTICS 1000

σ

NNSD

[km]

800

Free-floating

600 400 Paired NS and Zonal Control

200

Start Date: 1992-11-10T00:00:00 35 km altitude flights 100 balloons, UKMO Environment

0 0

20

40 60 80 Time from start [days]

100

120

TRAJECTORY CONTROL

Global Aerospace Corporation

Global Stratospheric Constellation

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

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Global Aerospace Corporation

Global Stratospheric Constellation

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 ULDB Dynamically-scaled Dynamically-scaled Model Model Flight Flight Test Test

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BALLOON

Global Aerospace Corporation

Global Stratospheric Constellation

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

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Global Aerospace Corporation

Global Stratospheric Constellation

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 µm 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

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SOLAR ARRAY / BALLOON INTEGRATION Sphere Pumpkin Seam/Load Tape as Solar Array

Gore Center As Solar Array

Envelope Film

Envelope Film

Example Power • • Seam/Load Tape / Solar Cells • (~ 3 cm wide) • •

48 m dia Spherical Design 100 Gores/Seams 3 cm Wide Solar Array 10 % Efficiency 4.7 kW

Thin Film Amorphous Si Solar Array Cells (~30 cm wide)

GONDOLA

Global Aerospace Corporation

Global Stratospheric Constellation

STRATOSAT GONDOLA

StratoSat Gondola • •

• • •

•

Stowed 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

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INTERNATIONAL OVERFLIGHT CONSIDERATIONS

Global Aerospace Corporation

Global Stratospheric Constellation

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

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PHASE II PLAN

Global Aerospace Corporation

Global Stratospheric Constellation

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

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SUMMARY

Global Aerospace Corporation

Global Stratospheric Constellation

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

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APPENDIX

Global Aerospace Corporation

Global Stratospheric Constellation

STEPS TO GLOBAL STRATOSPHERIC 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

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Global Aerospace Corporation

Global Stratospheric Constellation

STRATOSAT FLIGHT SYSTEM DESCRIPTION Mass Summary

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

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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

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Global Aerospace Corporation

Global Stratospheric Constellation

HOW THE TCS WORKS 15 m/s

• Winds vary with altitude

40

– Balloon at 30 km – Wing at 20 km – Relative wind velocity ~15 m/s

30

Alice Springs, January, 24¡ S

20 Altitude, km 10

• Wing generates lift force – – – –

Fairbanks, July, 65¡ N

“Lift” force is horizontal force is transmitted by tether to balloon balloon drifts relative to local air mass balloon drag ≈ wing lift

Source: Randel, W.J., Global Atmospheric Circulation Statistics, 1000-1 mb, NCAR/TN-366+STR, Feb. 1992

0 -40

-30

-20 -10 0 10 Mean Zonal Wind, m/s

20

• Wing is in much denser air than balloon – 25km : 35km (5x); 20km : 35km (10x) – equivalent wing area increased relative to balloon Global Aerospace Corporation

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Global Stratospheric Constellation

Global Aerospace

HOW THE TCS WORKS, CONTINUED

Corporation

TOP VIEW OF TCS

Fh TCS LIFT mode

TCS STALL mode

θ

α

α

θ

Fh

Vrel Stall Point 1.5

Fh

1.0

Vrel

CL

θ

Fh

0.5

0 0

10

20

30

40

50

60

70

80

Lift/Drag Polar: Contours of Feasible Aerodynamic Forces

90

Alpha

LIFT / DRAG FORCE POLAR

LIFT vs ANGLE OF ATTACK

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Global Stratospheric Constellation

Global Aerospace

HOW THE TCS WORKS, CONTINUED }

Corporation

Vdrift

Vcross

Expanded Vector Diagram

Vrel Vtrue

φ Vrel

D

Vb

L VTCS

Fh

Tether

TCS

β Fdrift ~ Fh Balloon

Top View Global Aerospace Corporation

Vdrift =

(

2 * Fdrift ρ ∗ Ab ∗ CD

1/2

)

β = φ - tan-1(D/L) Vcross=Vdrift * Cos β 43

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Global Stratospheric Constellation

Global Aerospace

ANGLES EXAGGERATED & FORCES NOT TO SCALE

Corporation

θB ~ 0.25¡ FB

BALLOON

FBV ~ 16,000 N F BH ~ 70 N

GONDOLA AT 35 km l 2

ASSUMPTIONS

¥ BALLOON DRIFT ~ 2 m/s ¥Ê0.6 million m3 BALLOON ¥ GONDOLA ~ 1500 kg ¥ TCS ~ 100 kg θ G ~ 0.4¡

θT ~ 4¡

FT

l1 = 2 l2

l1

WG ~ 15,000 N

SYMBOLS

T -> TETHER G -> GONDOLA B -> BALLOON H -> HORIZONTAL V -> VERTICAL W -> WEIGHT F -> FORCE L -> LIFT

θT ~ 4¡

TCS AT 20 km

FT

L ~ 70 N

ULDB TCS FORCE DIAGRAM

LIFT OF ~ 70 N REQUIRES TCP WING AREA OF ~ 16 m2 ASSUMING CL of 1.0

LV ~ 5 N

WTCS ~ 1000 N

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L + W = - FT

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