GLOBAL CONSTELLATION OF STRATOSPHERIC SCIENTIFIC PLATFORMS

Transcription

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

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

3 CONCEPT OVERVIEW

4 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 4 KTN - November 9, 1999

5 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 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 5 KTN - November 9, 1999

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

7 RATIONALE 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 7 KTN - November 9, 1999

8 KEYS TO THE CONCEPT Affordable, Long-duration Stratospheric Balloon and Payload Systems Lightweight, Low Power Balloon Trajectory Control Technology Global Communications Infrastructure Global 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 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 Global 11 KTN - November 9, 1999

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

13 40 30 km CLIMATE CHANGE: DYNAMICAL PROCESSES IN TROPICS in situ TDL Water, Ozone & CO 2 Absorption Measurement Cell Source Beam Detector Stratosphere Subsidence Air Flow Large-scale Ascent Tropopause Detector System Ozone & Water Vapor LIDAR Laser System Cal Target Scanning Mirror µwave Microwave Temperature Profiler LO Mixer Detector 0-90 Troposphere Global Equator

14 40 OZONE STUDIES: GLOBAL DISTRIBUTION OF OZONE 30 km Stratosphere Meteorology Science Pods Every 2-3 km, T, P Dropsondes H 2 O, O 3, CH 4, N 2 O and T, P Tropopause Cross Tropopause Exchange 0-90 Troposphere Global Equator

15 OZONE STUDIES: POLAR OZONE LOSS 40 km FTIR Interferometer FXST Optics Fore Optics Sun Tracker Camera IF Spectral Analysis Data Handling Streerable Reflector Plate Harmonic Mixer Gunn Oscillator Submillimeter Emission Limb Radiation 640 GHz Limb Scanner (SLS) GHz Mid-latitude Air 35 km FTIR / SLS Limb Scan Geometry 665 km FTIR SLS Limb 30 T, P Multipass Absorption Cell Measures: HCl, CH 4, N2O, O3 Source Beam Detector Air Flow Stratosphere Vortex Edge Scattered Light Partical Detector Measures: Aerosols Polar Stratospheric Clouds (PSCs) 70 Source Beam Detector Mixing Region Global 80 Air Flow 4445 km Polar Vortex Troposphere Pole 80 70

16 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 1000 km <50 m/s km Global 16 KTN - November 9, 1999

17 CONSTELLATION MANAGEMENT

18 GLOBAL CONSTELLATION WITHOUT TRAJECTORY CONTROL ASSUMPTIONS km Simulation Start: UK Met Office Assimilation 4 hrs per frame 4 month duration 1000 STATISTICS 800 σ NNSD [km] Start Date: T00:00:00 35 km constant altitude flights 100 balloons, UKMO Environment Time from start [days]

19 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 19 KTN - November 9, 1999

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

21 Environment Information Used MAINTENANCE STRATEGIES 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 21 KTN - November 9, 1999

22 GLOBAL CONSTELLATION WITH SIMPLE, INTELLIGENT CONTROL ASSUMPTIONS km Simulation Start: UK Met Office Assimilation 4 hrs per frame 4 month duration 5 m/s control when separation is < 2000 km Same initial conditions 1000 STATISTICS 800 Free-floating σ NNSD [km] Paired NS and Zonal Control Start Date: T00:00:00 35 km altitude flights 100 balloons, UKMO Environment Time from start [days]

23 TRAJECTORY CONTROL

24 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 24 KTN - November 9, 1999

25 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 Model Flight Test Global 25 KTN - November 9, 1999

26 BALLOON

27 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 27 KTN - November 9, 1999

28 BALLOON VEHICLE DESIGN Baseline Balloon Design Euler Elastica Pumpkin Design 68,765 m 3, 59/35 m Eq/Pole Dia., Equivalent to 51 m dia. Sphere Advanced Composite Film, 15 µm thick, 15 g/m 2 Areal Density 140 gores each 1.34 m Max Width Polybenzoxazole (PBO) Load Tendons At Gore Seams Balloon Mass of 236 kg Global 28 KTN - November 9, 1999

29 Sphere SOLAR ARRAY / BALLOON INTEGRATION Pumpkin Seam/Load Tape as Solar Array Gore Center As Solar Array Envelope Film Envelope Film Seam/Load Tape / Solar Cells (~ 3 cm wide) Example Power 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)

30 GONDOLA

31 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 31 KTN - November 9, 1999

32 INTERNATIONAL OVERFLIGHT CONSIDERATIONS

33 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 33 KTN - November 9, 1999

34 PHASE II PLAN

35 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 35 KTN - November 9, 1999

36 SUMMARY

37 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 s 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 37 KTN - November 9, 1999

38 APPENDIX

39 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 39 KTN - November 9, 1999

40 STRATOSAT FLIGHT SYSTEM DESCRIPTION Flight System Design Features Sample Payload for Climate Change Studies in Tropics 68,800 m 3 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 40 KTN - November 9, 1999

41 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 Lift force is horizontal force is transmitted by tether to balloon balloon drifts relative to local air mass balloon drag wing lift Wing is in much denser air than balloon 25km : 35km (5x); 20km : 35km (10x) equivalent wing area increased relative to balloon Global 41 KTN - November 9, m/s Fairbanks, July, 65 N 20 Alice Springs, January, 24 S Altitude, km 10 Source: Randel, W.J., Global Atmospheric Circulation Statistics, mb, NCAR/TN-366+STR, Feb Mean Zonal Wind, m/s

42 HOW THE TCS WORKS, CONTINUED F h TOP VIEW OF TCS TCS TCS STALL mode LIFT mode α θ α θ F h V rel Stall Point 1.5 CL 1.0 V rel F h θ Fh Alpha LIFT vs ANGLE OF ATTACK Lift/Drag Polar: Contours of Feasible Aerodynamic Forces LIFT / DRAG FORCE POLAR Global 42 KTN - November 9, 1999

43 V drift HOW THE TCS WORKS, V cross CONTINUED } Expanded Vector Diagram V true φ V rel V b V rel L D V TCS Fh Tether TCS β Top View Balloon F drift ~ F h V drift = ( 2 * F drift ) 1/2 ρ A b C D β = φ - tan -1 (D/L) V cross =V drift * Cos β Global 43 KTN - November 9, 1999

44 ANGLES EXAGGERATED & FORCES NOT TO SCALE F B θ B ~ 0.25 BALLOON F BV ~ 16,000 N F BH ~ 70 N GONDOLA AT 35 km ASSUMPTIONS BALLOON DRIFT ~ 2 m/s Ê0.6 million m 3 BALLOON GONDOLA ~ 1500 kg TCS ~ 100 kg θ G ~ 0.4 l 1 l 2 l 1 = 2 l 2 ULDB TCS FORCE TCS AT 20 km θ T ~ 4 F T θ T ~ 4 F T W G ~ 15,000 N SYMBOLS T -> TETHER G -> GONDOLA B -> BALLOON H -> HORIZONTAL V -> VERTICAL W -> WEIGHT F -> FORCE L -> LIFT DIAGRAM L ~ 70 N L V ~ 5 N LIFT OF ~ 70 N REQUIRES TCP WING AREA OF ~ 16 m 2 ASSUMING C L of 1.0 W TCS ~ 1000 N Global L + W = - F T 44 KTN - November 9, 1999