Matthew K. Heun

A Method for Balloon Trajectory Control

Abstract A balloon trajectory control system is discussed that is under development for use on NASAs Ultra Long Duration Balloon Project. The trajectory control system exploits the natural wind field variation with altitude to generate passive lateral control forces on a balloon using a tether-deployed aerodynamic surface below the balloon. A lifting device, such as a wing on end, is suspended on a tether well beneath the balloon to take advantage of this variation in wind velocity with altitude. The wing generates a horizontal lift force that can be directed over a wide range of angles. This force, transmitted to the balloon by a tether, alters the balloons path providing a bias velocity of a few meters per second to the balloon drift rate. The trajectory control system enables the balloon to avoid hazards, reach targets, steer around avoidance countries and select convenient landing zones. No longer will balloons be totally at the mercy of the winds. Tests in April 1999 of a dynamically-scaled model of the trajectory control system were carried out by Global Aerospace Corporation in ground level winds up to 15 m/s. The size of the scale model was designed to simulate the behavior of the full scale trajectory control system operating at 20 km altitude. The model confirmed many aspects of trajectory control system performance and the results will be incorporated into future development.

Aerodynamic and Mission Performance of a Winged Balloon Guidance System

A winged balloon guidance system exploits the natural wind-field variation with the altitude available in planetary atmospheres to generate passive lateral control forces on a balloon using a tether-deployed aerodynamic surface below the balloon. Several balloon guidance system topics are discussed, including development status, physics and aerodynamics, systems performance, concept of operations, and the near-space applications of this technology for scientific, communications, and defense applications.

Global stratospheric balloon constellations

A revolutionary concept is discussed for a global constellation and network of hundreds of stratospheric superpressure balloons that can address major scientific questions relating to Earth science. Global Aerospace Corporation is proposing this role for a new generation of stratospheric platform based on advanced balloon technology, called the StratoSat. StratoSat constellations can address issues of high interest to the Earth science community including global change, especially tropical circulation and radiation balance; global and polar ozone; hurricane forecasting and tracking; global circulation; and global ocean productivity. StratoSat constellations operating at a 35-km altitude and for 5 to 10 years in duration could augment and complement satellite measurements and possibly replace satellites for making some environmental measurements. The keys to this new concept are (a) affordable, long-duration balloon systems, (b) balloon trajectory control capability, and (c) a global communications infrastructure. Technology for these very long-duration and guided stratospheric balloons is summarized, constellation geometry management is discussed, international overflight issues are explored, and the StratoSat system design is described.

NAVAJO: Advanced Software Tool for Balloon Performance Simulation

Global Aerospace Corporation has developed an advanced balloon performance and analysis tool, called Navajo. Navajo advances the state of the art for balloon performance models and can assist NASA and commercial balloon designers, campaign and mission planners, and flight operations staff by providing higher-accuracy vertical and horizontal trajectory predictions than previously possible. Navajo advances the state of the art by employing a highly sophisticated radiative model that accounts for the actual design and shape of the balloon during ascent and float; by treating radiative fluxes in the atmosphere in a realistic manner; and by providing a graphical user interface. Navajo decouples environment and balloon trajectory models to allow a given balloon design to be flown within any number of environment models with different levels of fidelity. Navajo provides integrated vertical and horizontal trajectory modeling and an extensible application architecture to allow different balloon designs and new environments.

ADVANCED BALLOON PERFORMANCE SIMULATION AND ANALYSIS TOOL

Global Aerospace Corporation is developing an advanced balloon performance and analysis tool, called Navajo. Navajo will advance the state of the art for balloon performance models and assist NASA and commercial balloon designers, campaign and mission planners, and flight operations staff by providing high- accuracy vertical and horizontal trajectory predictions. Nothing like Navajo currently exists. The key innovation of this concept is integrated modeling of Earth and planetary balloons and Lighter Than Air (LTA) systems in a single user-friendly desktop computer application. Additional innovations are (a) decoupling of environment and balloon trajectory models to allow a given balloon design to be flown in any number of environments with different levels of fidelity, (b) integrated vertical and horizontal trajectory modeling, (c) integrated safety analysis of Earth balloon flights for in-flight and pre-flight safety calculations, (d) improved fidelity of thermal models, and (e) an extensible application architecture to allow different balloon designs and new environments. Navajo will provide the opportunity to have modeling capabilities lead the development of new Earth and planetary balloons

Mars Exploration with Directed Aerial Robot Explorers

Global Aerospace Corporation (GAC) is developing a revolutionary system architecture for exploration of planetary atmospheres and surfaces from atmospheric altitudes. The work is supported by the NASA Institute for Advanced Concepts (NIAC). The innovative system architecture relies upon the use of Directed Aerial Robot Explorers (DAREs), which essentially are long‐duration‐flight autonomous balloons with trajectory control capabilities that can deploy swarms of miniature probes over multiple target areas. Balloon guidance capabilities will offer unprecedented opportunities in high‐resolution, targeted observations of both atmospheric and surface phenomena. Multifunctional microprobes will be deployed from the balloons when over the target areas, and perform a multitude of functions, such as atmospheric profiling or surface exploration, relaying data back to the balloons or an orbiter. This architecture will enable low‐cost, low‐energy, long‐term global exploration of planetary atmospheres and surfaces. A conceptual analysis of DARE capabilities and science applications for Mars is presented. Initial results of simulations indicate that a relatively small trajectory control wing can significantly change planetary balloon flight paths, especially during summer seasons in Polar Regions. This opens new possibilities for high‐resolution observations of crustal magnetic anomalies, polar layered terrain, polar clouds, dust storms at the edges of the Polar caps and of seasonal variability of volatiles in the atmosphere.

A lightweight modular solar array for Ultra-Long Duration Balloon (ULDB) missions

Global Aerospace Corporation is developing a lightweight, modular solar array (StratArrayTM S/A) for NASAs Ultra Long Duration Balloon (ULDB) missions. The NASA objectives include developing a low-cost, integrated power system capable of supporting operations above 100,000 feet for durations as long as 100 days. The ULDB solar array must provide up to 2 kW for missions from polar to equatorial latitudes. Global Aerospace Corporation has developed an innovative design that is lightweight and meets the requirements with low mass and cost. The specific innovations of this effort were the use of: the Earths gravity field to reduce the mass of the deployment mechanism modular solar array construction tilt cables to orient the panels toward the sun without array rotation retraction cables to restow the array to protect it against impact forces during balloon termination and payload landing. An integral part of the design is the ability to track the sun without the need for gimbals or slip rings. The use of a modular approach allows selection of the appropriate number of array modules for each mission. The approach also allows the potential for substitution of less expensive array modules (this increases total subsystem mass) if programmatic needs require lower array costs. The ability to restow the array modules allows refurbishment to achieve reduced life cycle costs.

Biological Analogs and Emergent Intelligence for Control of Stratospheric Balloon Constellations

Global Aerospace Corporation is developing a revolutionary concept for a global constellation and network of hundreds of stratospheric superpressure balloons. Global Aerospace Corporation and Princeton University are studying methods of controlling the geometry of these stratospheric balloon constellations using concepts related to and inspiration derived from biological group behavior such as schooling, flocking, and herding. The method of artificial potentials determines control settings for trajectory control systems in the steady flow regions. Weak Stability Boundary theory is used to (a) determine the interfaces between smooth flow and areas where chaotic conditions exist and (b) calculate control settings in regions of chaotic flow.

Trajectory simulation for single balloons and networks

Abstract An understanding of the characteristics of trajectories of constant-altitude stratospheric platforms is important for scientific balloon flights because science observation sequences, safety planning, overflight negotiations, launch site selection, and recovery operations are affected by trajectory. Supported by NASA, Global Aerospace Corporation (GAC) has developed a Trajectory Simulation and Prediction System (TSPS) for NASAs Ultra Long Duration Balloon (ULDB) Project. We identified desirable launch dates based on historical trajectory dispersion. None of the launch sites that were studied exhibits significantly less dispersion than the other launch sites. However, latitude dispersion grows with flight duration, and trajectory dispersion growth is significant from 30- to 100-day flights. We also discuss work supported by the NASA Institute for Advanced Concepts (NIAC) where trajectory simulation techniques are applied to constellations of hundreds of balloons. We evaluate the prospects of managing the geometry of such constellations by using trajectory control systems.