MATHEMATICAL MODEL OF HOT-AIR BALLOON STEADY-STATE VERTICAL FLIGHT PERFORMANCE

Vertical flight performance of Lighter-than-Air free hot-air balloons is derived and discussed. Novel mathematical model using lumped-parameters has been used to model balloon flight dynamics and steady-state performance in particular. Thermal model was not treated as the super-heat is under the control of aeronauts/pilots. Buoyancy or gross lift, net or effective lift, specific lift, and excess specific lift were derived for a general single envelope balloon and can be applied to hot-air, gas and hybrid balloons. Rate-of-climb, absolute ceiling, rate-of-descent, and the maximum rate-of-descent or the uncontrolled terminal descent have all been modeled and sample computations performed for AX8 or AX9 FAI-class hot-air balloons. Lifting index or the specific net/effective lift have been computed treating ambient and hot air as ideal gases at various pressure altitudes and representative envelope temperatures. Drag coefficient in upward and downward vertical flights have been chosen based on best available data. Experimental scale and full-scale flight tests are suggested for more accurate estimates of external aerodynamics in vertical balloon flights. CFD computations of coupled inner- and external-flows are also recommended in future efforts. Knowledge of free balloon’s vertical performance is essential in flight planning and operational safety of flight.

A STRATOSPHERIC BALLOON FLIGHT PLATFORM AND ITS EMPLOYMENT IN GRAVITATIONAL WAVE COUNTERPART OBSERVATION EXPERIMENTS

The Cubesats Applied for MEasuring and LOcalising Transients (CAMELOT) initiative proposes to deploy a fleet of 3U nanosatellites in order to localise GRBs with all-sky coverage. The operation is based on measuring the time delay of the event trigger between satellites that are otherwise uniformly distributed around the Earth in low-Earth orbit (between 500 - 600 km of altitude). In this design, caesium-iodide crystals interact with soft gamma radiation by emitting optical photons. Utilization of this effect, each member of the fleet is equipped with four of such scintillators and the emitted photons are detected by multi-pixel photon counters (MPPCs). Precise timing is crucial for this concept, the timestamping of the events and the synchronisation is provided by GPS. In order to demonstrate the feasibility of the CAMELOT concept, a single-unit CubeSat, named "GRBAlpha" is currently being developed. GRBAlpha is equipped with a single block of scintillator but the other subsystems are all the same as it will be on the CAMELOT units. We describe this single-unit platform system, focusing on the model versions suitable for high-altitude stratospheric balloon flights. This model has a standardized layout (including pin-out configuration, signalling and bus communication) and compatible with significant proportion of CubeSat system vendors. This system of ours is also capable of hosting multiple payloads at the same time, optimizing the utilization of balloon experiments.

Balloon flight test of a CeBr3 detector with silicon photomultiplier readout

Recent advances in silicon photomultiplier (SiPM) technology and new scintillator materials allow for the creation of compact high-performance gamma-ray detectors which can be deployed on small low-cost satellites. A small number of such satellites can provide full sky coverage and complement, or in some cases replace the existing gamma-ray missions in detection of transient gamma-ray events. The aim of this study is to test gamma-ray detection using a novel commercially available CeBr3 scintillator combined with SiPM readout in a near-space environment and inform further technology development for a future space mission. A prototype gamma-ray detector was built using a CeBr3 scintillator and an array of 16 J-Series SiPMs by ON Semiconductor. SiPM readout was performed using SIPHRA, a radiation-tolerant low-power integrated circuit developed by IDEAS. The detector was flown as a piggyback payload on the Advanced Scintillator Compton Telescope balloon flight from Columbia Scientific Balloon Facility. The payload included the detector, a Raspberry Pi on-board computer, a custom power supply board, temperature and pressure sensors, a Global Navigation Satellite System receiver and a satellite modem. The balloon delivered the detector to 37 km altitude where its detection capabilities and readout were tested in the radiation-intense near-space environment. The detector demonstrated continuous operation during the 8-hour flight and after the landing. It performed spectral measurements in an energy range of 100 keV to 8 MeV and observed the 511 keV gamma-ray line arising from positron annihilation in the atmosphere with full width half maximum of 6.8%. During ascent and descent, the detector count rate peaked at an altitude of 16 km corresponding to the point of maximum radiation intensity in the atmosphere. Despite several engineering issues discovered after the flight test, the results of this study confirm the feasibility of using CeBr3 scintillator, SiPMs, and SIPHRA in future space missions.

UV-Induced Nanoparticles-Formation, Properties and Their Potential Role in Origin of Life

Inorganic nanoparticles might have played a vital role in the transition from inorganic chemistry to self-sustaining living systems. Such transition may have been triggered or controlled by processes requiring not only versatile catalysts but also suitable reaction surfaces. Here, experimental results showing that multicolor quantum dots might have been able to participate as catalysts in several specific and nonspecific reactions, relevant to the prebiotic chemistry are demonstrated. A very fast and easy UV-induced formation of ZnCd quantum dots (QDs) with a quantum yield of up to 47% was shown to occur 5 min after UV exposure of the solution containing Zn(II) and Cd(II) in the presence of a thiol capping agent. In addition to QDs formation, xanthine activity was observed in the solution. The role of solar radiation to induce ZnCd QDs formation was replicated during a stratospheric balloon flight.

Multihour Stratospheric Flights with the Heliotrope Solar Hot-Air Balloon

Standard meteorological balloons can deliver small scientific payloads to the stratosphere for a few tens of minutes, but achieving multihour level flight in this region is more difficult. We have developed a solar-powered hot-air balloon named the heliotrope that can maintain a nearly constant altitude in the upper troposphere–lower stratosphere as long as the sun is above the horizon. It can accommodate scientific payloads ranging from hundreds of grams to several kilograms. The balloon can achieve float altitudes exceeding 24 km and fly for days in the Arctic summer, although sunset provides a convenient flight termination mechanism at lower latitudes. Two people can build an envelope in about 3.5 h, and the materials cost about $30. The low cost and simplicity of the heliotrope enables a class of missions that is generally out of reach of institutions lacking specialized balloon expertise. Here, we discuss the design history, construction techniques, trajectory characteristics, and flight prediction of the heliotrope balloon. We conclude with a discussion of the physics of solar hot-air balloon flight.