Stratospheric Balloon Research Articles

Dynamics and control of a high-altitude balloon with slung load

Abstract The high-altitude balloon proposed in this paper is a long-life balloon carrying a payload through a cable that flies at 20km altitude in near space. A dynamic model of the system, including the thermodynamics of the buoyancy body coupled with a hanging model of the pod, is developed using the Newton–Euler method. The buoyancy body consists of a helium balloon and a ballonet. A differential pressure difference-based altitude adjustment is achieved by tracking the pressure difference at the target altitude. A dynamic simulation of the buoyancy body with a slung pod in autonomous vertical takeoff and altitude regulation processes is presented. The internal thermodynamic variations and pressure differential of the buoyancy body are given. The air mass exchange and blower flow control of the ballonet are validated. The altitude holding error is analysed. The maximum pull force that the cable can withstand is calculated, and the maximum attitude angles of the pod during the ascending and descending processes are depicted. Simulation results provide basic knowledge for the structural design and payload installation of pods.

Single-Use Aircraft Launch System with Small Helium Balloon for 1 kPa Flight Testing

A single-use aircraft launch system using a small helium balloon concept was proposed to elevate the likelihood of successful high-altitude flight tests above 30 km. The system, capable of carrying a payload of 0.5 kg, has been developed and reported. Completing the flight within a range of 92 km, which represents the maximum communication distance between the airborne flight system and the ground station for operational phase control, is imperative. Therefore, a straightforward method for simulating flight trajectories was outlined to determine launch windows and suitable locations to ensure flight completion within uninhabited areas. Simulation studies revealed that the shortest landing distance was obtained during summer at the selected launch site. Additionally, a parameter study was conducted to assess the influence of varying ascent velocities on the targeted flight test altitude, which depends on the payload weight and helium gas volume. Consequently, the parameter study results established the constraints for flight model design. A demonstration flight was conducted in 2023 to validate the feasibility of the system for high-altitude flight experiments. This flight successfully released the flight model at 31 km and recovered flight data before landing on the sea surface. The proposed system concept offers an expedited approach to aircraft design for operating in thin air. It enables component function tests and scaled model flights as an alternative to employing large high-altitude balloons for high-altitude experiments.

Station-Keeping Control of Stratospheric Balloons Based on Simultaneous Optimistic Optimization in Dynamic Wind

Stratospheric balloons serve as cost-effective platforms for wireless communication. However, these platforms encounter challenges stemming from their underactuation in the horizontal plane. Consequently, controllers must continually identify favorable wind conditions to optimize station-keeping performance while managing energy consumption. This study presents a receding horizon controller based on wind and balloon models. Two neural networks, PredRNN and ResNet, are utilized for short-term wind field forecast. Additionally, an online receding horizon controller, based on simultaneous optimistic optimization (SOO), is developed for action sequence planning and adapted to accommodate various constraints, which is especially suitable due to its gradient-free nature, high efficiency, and effectiveness in black-box function optimization. A reward function is formulated to balance power consumption and station-keeping performance. Simulations conducted across diverse positions and dates demonstrate the superior performance of the proposed method compared with traditional greedy and A* algorithms.

The Solar FUV-UV Spectra Measurement Experiment in the Near Space by High Altitude Balloon

An experiment measuring the solar far-ultraviolet-ultraviolet (FUV-UV) irradiance with spectral resolution better than 0.1 nm in the wavelength range from 170 to 400 nm was carried out by the “HongHu-6” high-altitude balloon that flew to the bottom region of the near-space in September 2022. This experiment was based on the fact that solar FUV-UV penetrates through a complex cross-section window of the upper atmosphere, from outer to near space. The solar FUV-UV deposits energy in the upper atmosphere, which provides a key to answer scientific questions on the most important energy contributor to overall heating sources of the near space and how the near-space environment responds to solar activities. In the wavelength range between 150 and 210 nm, irradiance maps from active regions of the solar corona, the comparative small cross-section of molecular oxygen allows certain wavelengths of the band to arrive at altitudes between 20 and 30 km above the ground, indicating solar flares could directly impact the bottom region of the near space. Solar UV irradiance in the wavelength range 210 – 400 nm is absorbed by the upper atmosphere as a function of wavelength, and energy is deposited vertically in the lower regions of the near space. This experiment historically provides measurement data to fill a gap in the wavelength shorter than 280 nm in the lower regions of the near space. The solar FUV-UV spectrometer (SUVS) is a compact instrument based on improved Roland circle optics to adapt to the “HongHu-6” balloon payload platform. In this paper, we introduce the scientific goals of the solar FUV-UV spectrum measurement experiment, provide information on the SUVS instrument preflight calibration, and present the first results from the flight data.

SOFIA/upGREAT far-infrared spectroscopy of bright rimmed pillars in IC 1848

Using the upGREAT instrument on SOFIA, we imaged the 158 mu m fine structure line emission in bright-rimmed pillars located at the southern edge of the IC 1848 region, and carried out pointed observations of the 63 and 145 mu m fine structure lines toward selected positions. The observations are used to characterize the morphology, velocity field, and the physical conditions in the G1--G3 filaments. The velocity-resolved spectra show evidence of a velocity shift at the head of the brightest G1 filament, possibly caused by radiation pressure from the impinging UV photons or the rocket effect of the evaporating gas. Archival Herschel PACS and SPIRE observations imply H$_2$ column densities in the range $10^ $ cm$^ $, corresponding to maximum visual extinction $A_V 10$ mag, and average H$_2$ volume density of $ $ in the filaments. The ii emission traces $ 17<!PCT!>$ of the total H$_2$ column density, as derived from dust SED fits. Photon-dominated region models are unable to explain the observed line intensities of the two fine structure lines in IC 1848, with the observed 145 mu m line being too strong compared to the model predictions. The lines in IC 1848 are overall weak and the signal-to-noise ratio is limited. However, our observations suggest that the 63/145 mu m intensity ratio is a sensitive probe of the physical conditions in photon-dominated regions such as IC 1848. These lines are thus excellent targets for future high-altitude balloon instruments, less affected by telluric absorption.

Effect of Thermal Environment on Heat Transfer Mechanism of Solar-Powered Balloon

Solar energy units, as an ideal alternative, can be supplied to the balloons by mounting them over the envelope of the balloon. To avoid superheating and superpressure, the solar-powered balloon’s thermal efficiency should be controlled. In the current research, the thermal model of a solar-powered zero-pressure balloon has been built up and simulated in FORTRAN via iterative techniques and validated with published experimental data. The simulation of stratospheric solar-powered balloon flight has been carried out in real seasonal atmospheric conditions. The temperature variation of solar panels, interior helium, and balloon envelope material has been observed and compared with the unpowered balloon in winter and summer atmospheric conditions. The output power performance of the photovoltaic panel placed over the balloon with and without thermal effect has been reported. Furthermore, the characteristic length, angle, and area of the solar panel effects on photovoltaic panel temperature and output power are discussed in detail. The maximum temperature of the helium and envelope of the solar-powered balloon is obtained as 350.03 K and 351.19 K, respectively, and is notable in the summer solstice compared with the unpowered balloon. This research would help design the energy unit of the stratospheric balloon for long endurance.

Seasonal and geographic viability of high altitude balloon navigation

Control of the geographic location of high-altitude balloons has been desired for decades due to the cost and simplicity of the systems. These balloon systems rely on variations in wind direction with altitude so that when a balloon changes height, it also changes the direction of its horizontal motion. An altitude control system can thus also control the horizontal position by transitioning to a wind layer with favorable winds. The system’s ability to navigate successfully thus relies on the existence of certain wind conditions. In this paper, we explore how the ability of a balloon to station-keep varies based on the geographic location and season. We used spatially and temporally variant ERA5 wind data with a tree-search-based algorithm to traverse potential trajectories, and we selected the altitude transitions that maximize time within 50 km of a target. The simulation’s outputs show large variations in success across both latitude and season. Midlatitudes are particularly challenging for station-keeping, while lower latitudes are more favorable. Summer is typically more favorable than winter. This demonstrates that for all balloon systems, the ability to station-keep is highly variant and not universally possible.

The space not beyond: T. S. Eliot’s Old Possum’s Book of Practical Cats (1939) and their musical adaptations as elemental melodrama of an upper-atmospheric limit

ABSTRACT This essay examines T.S. Eliot’s Old Possum’s Book of Practical Cats (1939) and its subsequent musical adaptation, Cats (1981) by Andrew Lloyd Webber, through the lens of elemental melodrama. It begins with Eliot’s envisioned but omitted conclusion, where a poet ascends with Jellicle cats, and explores its revival in the musical’s song ‘Journey to the Heaviside Layer’. This ascent melodramatises the climactic journey to a heaven, an imaginary space beyond Earth’s tangible experiences. The essay contrasts the musical’s alignment of the Heaviside Layer with a ‘heaven’ oriented toward the desires and aspirations of anthropomorphised cats with Joseph Kittinger’s 1960 high-altitude balloon ascent and Maurice Blanchot’s reflections on Yuri Gagarin’s space mission. Both Kittinger’s and Blanchot’s writings reveal the Heaviside Layer as both a real and metaphorical space of death and existential void, contrasting with the musical’s portrayal of it purely in terms of celestial ascent. Drawing on Peter Brooks’s theory of melodrama as a post-sacred mode, the essay highlights how tableau, gesture, heightened emotion and, especially, song in Cats convey a collective yearning for transcendence. Ultimately, it argues that the Heaviside Layer in Cats serves as a zone of elemental melodramatic transcendence. It is in this context that earthly limitations, particularly those relating to embodied differences of race and sex, exist in tension with feline (and, by implication, human) aspirations for an unreachable ‘beyond’.

Flying microbes-survival in the extreme conditions of the stratosphere during a stratospheric balloon flight experiment.

Earth's stratosphere is a hostile environment that has challenged microbial survival. We set out to test the effect of stratosphere exposure on survival of single species (Bacillus subtilis) and complex microbial communities from soils and sediment. B. subtilis survival was strongly impacted by sun exposure, i.e., ultraviolet (UV) radiation, with only 1% survival at full sun exposure. Complex microbial communities had high survival rates, and the soil or sediment matrix may have provided protection against radiation and desiccation, supporting the survival of environmental microorganisms.

Modeling and characterization of gas coupled ultrasonic transducers at low pressures and temperatures and implications for sonic anemometry on Mars.

A sonic anemometer targeted at wind speed measurements on the surface of Mars is described. This environment requires transducer operation in 4-10 mbar CO2 at temperatures between 143 and 293 K (-130 °C and 20 °C, respectively). Over these ranges, transducer pressure and temperature sensitivity could be a source of measurement error. To investigate this, four candidate transducers were tested using transmission mode ultrasonic testing and impedance measurements: two narrowband piezoelectric transducers, a broadband capacitive transducer, and a micromachined capacitive ultrasound transducer. A system model was used for comparison and interpretation, and implications for a sonic anemometer were examined. Variation of transducer characteristics, including diffraction effects, across 2-10 mbar in CO2 and 190-293 K (-83 °C-20 °C) result in ±2.3% error in wind speed measurement and ±1.1% error in speed of sound measurement for the worst case but only ±0.14% error in wind and ±0.07% error in speed of sound for the best transducer operated off resonance. The acoustic conditions on Mars are similar to those in Earth's stratosphere at 30-42 km of altitude. Hence, testing was also conducted in dry air over the same range of pressures and temperatures with relevance to a secondary application of the instrument as a stratospheric anemometer for high altitude balloon missions on Earth.

Stratospheric balloon dynamics predictions for robust ascent phase payload thermal analysis

Stratospheric balloons are platforms with great relevance in space missions to reach scientific observations. The payload thermal analyses of such missions are usually focused on the float phase. However, during the ascent phase, the coolest temperatures of the entire mission may be reached, mainly due to the convective cooling in the tropopause. This can be explained by the combination of relative wind speed and the harsh thermal environment. The aim of this work is to evaluate the impact of the thermal environment on the relative wind speed to determine the worst-case thermal analysis. Therefore, in order to perform a robust payload thermal during the ascent phase, the uncertainty in the thermal environment and the relative velocity must be evaluated. The former are reduced by defining the thermal environment based on real-data. The latter are reduced by evaluating the parameters involved in the ascent rate. For this purpose, a dynamic model has been developed to characterise the ascent rate and the horizontal relative velocity of the balloon-borne system. This tool has been validated with flight data from the REXUS/BEXUS programme, with the BEXUS missions launched from Esrange, Kiruna, Sweden from 2014 to 2018. The thermal analysis performed shows a temperature difference greater than 10 °C depending on the thermal worst-case selection. The work here presented reduces the uncertainties of the stratospheric payloads ascent phase thermal analysis.

Connecting quantum cities: simulation of a satellite-based quantum network

We present and analyze an architecture for a European-scale quantum network using satellite links to connect Quantum Cities, which are metropolitan quantum networks with minimal hardware requirements for the end users. Using NetSquid, a quantum network simulation tool based on discrete events, we assess and benchmark the performance of such a network linking distant locations in Europe in terms of quantum key distribution rates, considering realistic parameters for currently available or near-term technology. Our results highlight the key parameters and the limits of current satellite quantum communication links and can be used to assist the design of future missions. We also discuss the possibility of using high-altitude balloons as an alternative to satellites.

Measurement of background radiations and spectra of X-ray sources using low-cost stratospheric balloon missions

In small balloon missions, some in situ radiation is added to the targeted strong persistent astronomical sources (such as, the Sun, Crab, Cygnus X-1, etc.) or transient sources, such as solar flares, gamma-ray bursts, etc., during their detection, i.e., the background radiation. For measurement and modeling of background radiation, we use the data of the low-cost, small, stratospheric, high-altitude balloon-borne missions conducted by Indian Centre for Space Physics. In this paper, we show several models to estimate the background counts where the strong X-ray sources are detected at the altitude range of ∼35–42 km even in the absence of onboard pointing system and severe atmospheric absorption. For all data analysis purposes, the photons detected in the detector are in the energy range of 10–80 keV. Moreover, we found that the observed data is within ±1σ of the calculated background model. Finally, using these background models, we estimate the spectra and luminosity of the Crab nebula and the black hole candidate Cygnus X-1, which agree with the previously published results.

Forward modeling of quake’s infrasound recorded in the stratosphere on board balloon platforms

Acoustic waves generated by seismic waves contain information on the internal structure of planets, and can be sensed by pressure sensors onboard high-altitude balloons. To identify the various contributions (infrasound signal, noise, balloon response, etc.) in such pressure records, a full waveform modeling is implemented and completed by infrasound ray tracing and additional data analysis. Here, we analyze the Stratéole-2 pressure data associated with two earthquakes (Garcia et al. Geophys. Res. Lett. 49(15):e98844, 2022) and compared these to full waveform simulations by SPECFEM2D-DG-LNS software. Even if our simulations do not precisely reproduce the waveform observed in the frequency range [0.05, 0.3] Hz, we show that the waveform presents more sensitivity to quake and internal structure parameters than to atmospheric structure, and that seismic surface wave dispersion is observed in balloon pressure records. The long-duration pressure oscillations observed after the main infrasonic signal cannot be fully reproduced by our one-dimensional input model even when source time function complexity and aftershocks are considered. These features are ascribed mainly to the complex vertical ground movements below the balloon and partly to late secondary infrasound arrivals excited by the interactions of seismic waves with the topography. These results enhance the advantages and limitations of quake-related infrasound observations on board terrestrial and planetary balloon platforms.Graphical

SunbYte: an autonomous pointing framework for low-cost robotic solar telescopes on high altitude balloons

The design and usability of a fully autonomous robotic control system (SunbYte - Sheffield University Balloon “lYfted” TElescope) for solar tracking and observational applications onboard high-altitude balloons are addressed here. The design is based on a six-step development plan balancing scientific objectives and practical engineering requirements. The high-altitude solar observational system includes low-cost components such as a Cassegrain-type telescope, stepper motors, harmonic drives, USB cameras and microprocessors. OpenCV installed from ROS (Robotic Operating System), python and C facilitated the collection, compression, and processing of housekeeping and scientific data. This processed data was then transmitted to the ground station through the launch vehicle’s telecommunication link. The SunbYte system allows the brightest spot in the sky, the sun, to be identified, and a telescope pointed towards it with high enough accuracy that a scientific camera can capture images. This paper gathers and presents the results from primarily two missions with the High-Altitude Student Platform (HASP, NASA Balloon Program office and LaSpace). Additionally, a discussion will be made comparing these with an earlier iteration flown with the German-Swedish “REXUS/BEXUS” programme coordinated by the European Space Agency. By capturing and analysing a series of tracking images with the location of the Sun at the calibrated centre, the system demonstrated the tracking capabilities on an unstable balloon during ascent. Housekeeping sensor data was collected to further analyse the thermal and mechanical performance. The low temperature increased friction in the drive train and reduced the responsiveness of the harmonic drive actuation system. This caused some issues which require further work in future missions, for example, with SunbYte 4 and its work when flying with the HEMERA ZPB (Zero Pressure Balloon) program.

Detection of Moving Objects in Earth Observation Satellite Images: Verification

In multi-spectral images made by Earth observation satellites that use push-broom scanning, such as those operated by Planet Labs Corp., moving objects can be identified by the appearance of the object at different locations in each spectral band. The apparent velocity can be measured if the relative acquisition time between images in different spectral bands is known to millisecond accuracy. The images in the Planet Labs archive are mosaics of individual exposures acquired at different times. Thus, there is not a unique acquisition time for each spectral band. In an earlier paper, we proposed a method to determine the relative acquisition times from the information in the images themselves. High-altitude balloons provide excellent targets to test our proposed method because of their high apparent velocity due to the orbital velocity of the satellite and geometric parallax in images aligned to the level of the ground. We use images of the Chinese balloon that crossed the US in February 2024 as well as images of an identical balloon over Colombia to test our method. Our proposed method appears to be successful and allows the measurement of the apparent velocity of moving objects from the information available in the archive.

Globin: A spectropolarimetric inversion code for the coupled inference of atomic line parameters

Context. The reliability of physical parameters describing the solar atmosphere inferred from observed spectral line profiles depends on the accuracy of the involved atomic parameters. For many transitions, atomic data, such as the oscillator strength (log(gf)) and the central wavelength of the line, are poorly constrained or even unknown. Aims. We present and test a new inversion method that infers atomic line parameters and the height stratification of the atmospheric parameters from spatially resolved spectropolarimetric observations of the Sun. This method is implemented in the new inversion code globin. Methods. The new method employs a global minimization algorithm enabling the coupling of inversion parameters common to all pixels, such as the atomic parameters of the observed spectral lines. At the same time, it permits the optimum atmospheric parameters to be retrieved individually for each spatial pixel. The uniqueness of this method lies in its ability to retrieve reliable atomic parameters even for heavily blended spectral lines. We tested the method by applying it to a set of 18 blended spectral lines between 4015 Å and 4017 Å, synthesized from a 3D magnetohydrodynamic simulation containing a sunspot and the quiet Sun region around it. The results were then compared with a previously used inversion method where atomic parameters were determined for every pixel independently (pixel-by-pixel method). For the same spectral region, we also inferred the atomic parameters from the synthesized spatially averaged disc-centre spectrum of the quiet-sun. Results. The new method was able to retrieve the log(gf) values of all lines to an accuracy of 0.004 dex, while the pixel-by-pixel method retrieved the same parameter to an accuracy of only 0.025 dex. The largest differences between the two methods are evident for the heavily blended lines, with the former method performing better than the latter. In addition, the new method is also able to infer reliable atmospheric parameters in all the inverted pixels by successfully disentangling the degeneracies between the atomic and atmospheric parameters. Conclusions. The new method is well suited for the reliable determination of both atomic and atmospheric parameters and works well on all spectral lines, including those that are weak and/or severely blended. This is of high relevance, especially for the analysis of observations of spectral regions with a very high density of spectral lines. An example includes the future near-ultraviolet spectropolarimetric observations of the SUNRISE III stratospheric balloon mission.

Sovereignty and Jurisdiction Conflicts from High-altitude Balloons under International Law

Sovereignty and Jurisdiction Conflicts from High-altitude Balloons under International Law

IPCB: Intelligent Pseudolite Constellation Based on High-Altitude Balloons

IPCBs (Intelligent Pseudolite Constellations based on high-altitude balloons) are a novel type of air-based pseudolite application with many advantages. Compared with ground-based pseudolites and traditional air-based pseudolites, IPCBs have a wider coverage and a lower energy requirement. Compared with LEO satellite constellations, IPCBs have a stronger signal, a lower cost, and a shorter deployment period. These merits give promising potential to IPCBs. In IPCB applications, one of the key factors is geometry configuration, which is deeply influenced by the balloon’s unique features. The basic idea of this paper is to pursue a strategy to improve IPCB geometry performance by using diverse winds at different altitudes and balloons’ capability of altering flight altitude intelligently. Starting with a brief introduction to IPCBs, this paper defines an indicator to assess IPCB geometry performance, an approach to adjust IPCB geometry configuration and an IPCB geometry configuration planning algorithm. Next, a series of simulations are implemented with an IPCB composed of six pseudolites in winds with/without a quasi-zero wind layer. Some IPCB geometry configurations are analyzed, and their geometry performances are compared. Simulation results show the effectiveness of the proposed algorithm and the influence of the quasi-zero wind layer on IPCB performance.

Study of Secondary Cosmic Rays and Astronomical X-Ray Sources using Small Stratospheric Balloons

The X-ray sources of the universe are extraterrestrial in nature which emit X-ray photons. The closest strong X-ray source is the Sun, which is followed by various compact sources such as neutron stars, black holes, the Crab pulsar, etc. In this paper, we analyze the data received from several low-cost lightweight meteorological balloon-borne missions launched by the Indian Centre for Space Physics. Our main interest is to study the variation of the vertical intensity of secondary cosmic rays, the detection of strong X-ray sources, and their spectra in the energy band of ∼10–80 keV during the complete flights. Due to the lack of an onboard pointing system, low exposure time, achieving a maximum altitude of only ∼42 km, and freely rotating the payload about its axis, we modeled the background radiation flux for the X-ray detector using physical assumptions. We also present the source detection method, observation of the pulsation of the Crab (∼33 Hz), and spectra of some sources such as the quiet Sun and the Crab pulsar.