Development of a super-pressure balloon with a diamond-shaped net

The essential reason of the lobed-pumpkin shaped super-pressure balloon to withstand against the high pressure is that the local curvature of the balloon film is kept small. Recently, it has been found that the small local curvature can also be obtained if the balloon is covered by a diamond-shaped net with a vertically elongated shape. The development of the super-pressure balloon using this method was started from a 3-m balloon with a polyethylene film covered by a net using Kevlar ropes. The ground inflation test showed the expected high burst pressure. Then, a 6-m and a 12-m balloon using a polyethylene film and a net using the Vectran were developed and stable deployment was checked through the ground inflation tests. The flight test of a 3000 m³ balloon was performed in 2013 and shown to resist a pressure of at least 400 Pa. In the future, after testing a new design to relax a possible stress concentration around the polar area, test flights of scaled balloons will be performed gradually enlarging their size. The goal is to launch a 300,000 m³ super-pressure balloon.     

Scientific ballooning in India – Recent developments

Established in 1971, the National Balloon Facility operated by TIFR in Hyderabad, India, is a unique facility in the country, which provides a complete solution in scientific ballooning. It is also one of its kind in the world since it combines both, the in-house balloon production and a complete flight support for scientific ballooning. With a large team working through out the year to design, fabricate and launch scientific balloons, the Hyderabad Facility is a unique centre of expertise where the balloon design, research and development, the production and launch facilities are located under one roof. Our balloons are manufactured from 100% indigenous components. The mission specific balloon design, high reliability control and support instrumentation, in-house competence in tracking, telemetry, telecommand, data processing, system design and mechanics is its hallmark. In the past few years, we have executed a major programme of upgradation of different components of balloon production, telemetry and telecommand hardware and various support facilities. This paper focuses on our increased capability of balloon production of large sizes up to 780,000 m³ using Antrix film, development of high strength balloon load tapes with the breaking strength of 182 kg, and the recent introduction of S-band telemetry and a commandable timer cut-off unit in the flight hardware. A summary of the various flights conducted in recent years will be presented along with the plans for new facilities.     

Scientific ballooning in Japan

Activities in scientific ballooning in Japan during 1998–1999 are reported. The total number of scientific balloons flown in Japan in 1998 and 1999 was sixteen, eight flights in each year. The scientific objectives were observations of high energy cosmic electrons, air samplings at various altitudes, monitoring of atmospheric ozone density, Galactic infrared observations, and test flights of new type balloons. Balloon expeditions were conducted in Antarctica by the National Institute of Polar Research, in Russia, in Canada and in India in collaboration with foreign countries' institutes to investigate cosmic rays, Galactic infrared radiation, and Earth's atmosphere. There were three flights in Antarctica, four flights in Russia, three flights in Canada and two flights in India. Four test balloons were flown for balloon technology, which included pumpkin-type super-pressure balloon and a balloon made with ultra-thin polyethylene film of 3.4 μm thickness.     

Enhancing the ATIC charge resolution

The Advanced Thin Ionization Calorimeter (ATIC) experiment is designed to investigate the charge composition and energy spectra of primary cosmic rays over the energy range from about 10¹¹ to 10¹⁴ eV during Long Duration Balloon (LDB) flights from McMurdo, Antarctica. Currently, analysis from the ATIC-1 test flight and ATIC-2 science flight is underway and preparation for a second science flight is in progress. Charge identification of the incident cosmic ray is accomplished, primarily, by a pixilated Silicon Matrix detector located at the very top of the instrument. While it has been shown that the Silicon Matrix detector provides good charge identification even in the presence of electromagnetic shower backscatter from the calorimeter, the detector only measures the charge once. In this paper, we examine use of the top scintillator hodoscope detector to provide a second measure of the cosmic ray charge and, thus, improve the ATIC charge identification.     

Cleft formation in pumpkin balloons

NASA’s development of a large payload, high altitude, long duration balloon, the Ultra Long Duration Balloon, centers on a pumpkin shape super-pressure design. Under certain circumstances, it has been observed that a pumpkin balloon may be unable to pressurize into the desired cyclically symmetric equilibrium configuration, settling into a distorted, undesired state instead. Success of the pumpkin balloon for NASA requires a thorough understanding of the phenomenon of multiple stable equilibria and developing of means for the quantitative assessment of design measures that prevent the occurrence of undesired equilibrium. In this paper, we will use the concept of stability to classify cyclically symmetric equilibrium states at full inflation and pressurization. Our mathematical model for a strained equilibrium balloon, when applied to a shape that mimics the Phase IV-A balloon of Flight 517, predicts instability at float. Launched in Spring 2003, this pumpkin balloon failed to deploy properly. Observations on pumpkin shape type super-pressure balloons that date back to the 1980s suggest that within a narrowly defined design class of pumpkin shape super-pressure balloons where individual designs are fully described by the number of gores n_g and by a single measure of the bulging gore shape, the designs tend to become more vulnerable with the growing number of gores and with the diminishing size of the bulge radius r_B Weight efficiency considerations favor a small bulge radius, while robust deployment into the desired cyclically symmetrical configuration becomes more likely with an increased bulge radius. In an effort to quantify this dependency, we will explore the stability of a family of balloon shapes parametrized by (n_g, r_B) which includes a design that is very similar, but not identical, to the balloon of Flight 517. In addition, we carry out a number of simulations that demonstrate other aspects related to multiple equilibria of pumpkin balloons.     

Power supplies for long duration balloon flights

Long duration balloon flights require more electrical power than can be carried in primary batteries. This paper provides design information for selecting rechargeable batteries and charging systems. Solar panels for recharging batteries are discussed, with particular emphasis on cells mounting suitable for balloon flights and panel orientation for maximum power collection. Since efficient utilization of power is so important, modern DC to DC power conversion techniques are presented.On short flights of 1 day or less, system designers have not been greatly concerned with battery weight. But, with the advent of long duration balloon flights using superpressure balloons, anchor balloon systems, and RACOON balloon techniques, power supplies and their weight become of prime importance. The criteria for evaluating power systems for long duration balloon flights is performance per unit weight. Instrumented balloon systems have flown 44 days. For these very long duration flights, batteries recharged from solar cells are the only solution. For intermediate flight duration, say less than 10 days, the system designer should seriously consider using primary cells.     

Stratospheric flights with large polyethylene baloons from equatorial latitudes

Starting with average 50% success for stratospheric balloon flights during 1959–1969 and attaining 100% success during 1972–1973, the success record dropped to 50% during 1974–1979. Through a critical analysis of 59 flights made from Hyderabad and 21 flights made from other equatorial bases, revised design criteria were proposed for balloons to be flown from equatorial latitudes, which were accepted by M/s Winzen International, Inc. (WII), U.S.A. and have again raised the success record to 93% for 15 flights made since April 1980. A revised analysis for 71 flights made from 1965 to 1984 has been presented. Stratospheric circulation over Hyderabad indicating predominance of easterlies with mesospheric westerlies descending occasionally into stratosphere has been discussed.     

Systems for long duration flights

This paper describes the systems for long duration flights developed in Japan for scientific observations. Much efforts have been expended to evolve systems for long duration flights in Japan, by controlling the balloon trajectories with a knowledge of wind pattern at high altitudes over Japan. These systems called “Cycling Balloon”, “Boomerang Balloon” and “New Boomerang Balloon” have been successfully used for the observations by keeping the balloons close to the balloon station.“Relay Balloon” is another system to extend the telemetry range by using an additional balloon as a relay station to link the telemetry from the main balloon.Some detailes of the exhaust valve, ascent meter and automatic level control devices used for the balloon control are also described in the paper.     

Feasibility study of a sea-anchored stratospheric balloon for long-duration flights

Sea-anchored balloons are stratospheric super-pressure balloons that are anchored to the sea. The sea-anchored balloon is a simple system that has the capability for long-duration flights, fixed-point observations, flexible launch windows, easy telemetry links to ground stations, and quick recoveries. Such balloons are not required to fly through the jet stream while tethered to the ground or sea, because the tether is deployed from a reel on the balloon after reaching a floating altitude. In this study, the feasibility of the sea-anchored balloon is investigated, with particular emphasis on the tether strength, balloon altitude, and system mass, based on the present technological level of the tether’s specific strength. Although the wind distribution with altitude is a dominant factor for feasibility, a sea-anchored balloon with an altitude of about 25 km would be feasible if the velocity of the jet stream is sufficiently low. The sea-anchored balloon can be simply flight-tested, since additional ground facilities and special flight operations are not necessary.     

Second generation prototype design and testing for a high altitude Venus balloon

This paper describes the development of a second generation prototype balloon intended for flight in the upper atmosphere of Venus. The design of this new prototype incorporates lessons learned from the construction and testing of the first generation prototype, including finite element analyses of the balloon stresses and deformations, measured leak performance after handling and packaging, permeability and optical property measurements on material samples, and sulfuric acid testing. An improved design for the second generation prototype was formulated based on these results, although the spherical shape and 5.5 m diameter size were retained. The resulting balloon has a volume of 87 m³ and is capable of carrying a 45 kg payload at a 55 km altitude at Venus. The design and fabrication of the new prototype is described, along with test data for inflation and leakage performance.     

Development of the High Altitude Student Platform

The High Altitude Student Platform (HASP) was originally conceived to provide student groups with access to the near-space environment for flight durations and experiment capabilities intermediate between what is possible with small sounding balloons and low Earth orbit rocket launches. HASP is designed to carry up to twelve student payloads to an altitude of about 36 km with flight durations of 15–20 h using a small zero-pressure polyethylene film balloon. This provides a flight capability that can be used to flight-test compact satellites, prototypes and other small payloads designed and built by students. HASP includes a standard mechanical, power and communication interface for the student payload to simplify integration and allows the payloads to be fully exercised. Over the last two years a partnership between the NASA Balloon Program Office (BPO), Columbia Scientific Balloon Facility (CSBF), Louisiana State University (LSU), the Louisiana Board of Regents (BoR), and the Louisiana Space Consortium (LaSPACE) has led to the development, construction and, finally, the first flight of HASP with a complement of eight student payloads on September 4, 2006. Here we discuss the primary as-built HASP systems and features, the student payload interface, HASP performance during the first flight and plans for continuing HASP flights. The HASP project maintains a website at http://laspace.lsu.edu/hasp/ where flight application, interface documentation and status information can be obtained.     

Telemetry,telecommand and safety sub-systems for scientific ballooning from Hyderabad

Highly sophisticated balloon-borne scientific payloads have stringent requirement on the telemetry and command system. The development and fabrication of the on-board TT&C package for telemetry, tracking, command, safety and ranging for these experiments is done in-house at the National Balloon Facility (NBF) at Hyderabad. In the last few years, we have made major improvements both in the ground station and the on-board sub-systems, thereby improving the data quality, data handling speed and the general flight control along with aviation safety. The new system has telemetry data rate up to 1 Mbps. A reduction in weight, power and cost of the reengineered on-board integrated package has also lead to the ease of operation during field tests prior to launch and at remote recovery sites. In this paper, we describe the details of the new control package, its flight performance and our plans for portable S-band telemetry and telecommand system to cater to the balloon flights from Antarctic station and long duration balloon flights.     

A new balloon base in Japan

Since 1971, numerous balloons have been launched from the Japanese balloon base, the Sanriku Balloon Center (SBC). Through these years, balloon technologies have been developed continuously and many scientific achievements have resulted. Recently, however, because of the limited area of the launching pad of the SBC, we have been faced with the difficulty of safely launching large balloons. To solve this issue, we decided to move the balloon base from the SBC to the Taiki Aerospace Research Field (TARF) in northern Japan. The TARF had an existing huge hanger and a paved launch pad capable of being utilised for balloon operations. To evolve the TARF into a new balloon base, new balloon facilities have been constructed at the TARF and equipment was transferred from the SBC to the TARF during July 2007 and March 2008. The SBC was closed in September 2007, and the new base became operational in May 2008. The new base at the TARF is designed to launch larger balloons with greater safety and to perform balloon operations more effectively than ever before. In the summer of 2008, we carried out the first series of the balloon campaign at the TARF, and succeeded in two engineering flights of stratospheric balloons. By the success of these flights, we have verified that the whole system of the new balloon base is well established.     

The energy spectra of protons and helium measured with the ATIC experiment

The Advanced Thin Ionization Calorimeter (ATIC) balloon experiment is designed to investigate the composition and energy spectra of cosmic rays at the highest energies currently accessible by direct measurements, i.e., the region up to 100 TeV. The instrument consists of a silicon matrix for charge measurement, a graphite target (0.75 nuclear interaction length) to induce hadronic interactions, three layers of scintillator strip hodoscopes for triggering and trajectory reconstruction, and a Bismuth Germanate (BGO) crystal calorimeter (18 radiation lengths) to measure particle energies. ATIC has had two successful Long Duration Balloon (LDB) flights from McMurdo, Antarctica: one from 12/28/00 to 01/13/01 and the other from 12/29/02 to 01/18/03. We present the energy spectra of protons and helium extracted from the first flight, over the energy range from 100 GeV to 100 TeV, and compare them with the results from other experiments at both the lower and higher energies. ATIC-1 results do not indicate significant differences in spectral shape between protons and helium over the investigated energy range.     

Balloon observations of temporal and spatial fluctuations in stratospheric conductivity

The first campaign of the Polar Patrol Balloon (PPB) experiment (1st-PPB) was carried out at Syowa Station in Antarctica during 1990–1991 and 1992–1993. Based on the results of the 1st-PPB experiment, the next campaign (2nd-PPB) was carried out in the austral summer of 2002–2003. This paper will present stratospheric conductivity results from the 2nd-PPB experiment. In that experiment, three balloons were launched for the purpose of upper atmosphere physics observation (three balloons). Payloads of these three flights were identical with each other, and were launched as close together in time as allowed by weather conditions to constitute a cluster of balloons during their flights. Such a “Balloon Cluster” is suitable to observe temporal evolution and spatial distribution of phenomena in the ionospheric regions and boundaries that the balloons traversed during their circumpolar trajectory. More than 20 days of simultaneous fair weather 3-axis electric field and stratospheric conductivity data were obtained at geomagnetic latitudes ranging from sub-auroral to the polar cap. Balloon separation varied from ∼60 to >1000 km. This paper will present stratospheric conductivity observations with emphasis on the temporal and spatial variations that were observed.     

High altitude flights in equatorial regions

A thorough analysis of balloon flights made from Hyderabad, India (Latitude 17°28′N, Longitude 78°35′E), and other equatorial sites has been made. It has been shown that limited success is expected for flights made from equatorial latitudes with balloons made out of natural colour polyethylene film, since the best known balloon film in the world today viz. Winzen Stratofilm is tested for low temperature brittleness only at ?80°C., whereas the tropopause temperatures over equatorial latitudes vary between ?80°C and ?90°C. The success becomes even more critical when flights are made with heavy payloads and larger balloons particularly at night when in the absence of solar radiation the balloon film becomes more susceptible to low temperature brittle failure. It is recommended that in case of capped balloons longer caps should be used to fully cover the inflated protion of the balloon at the higher level equatorial tropopause. It is also advised that the conditions such as wind shears in the tropopause should be critically studied before launching and a day with the tropopause temperature nearer to ?80°C should be chosen. Special care also should be taken while handling the balloon on ground and during launching phase. Properties of Winzen Stratofilm have been critically studied and fresh mandates have been recommended on the basis of limiting values of film stresses which caused balloon failures in the equatorial tropopause. It is also emphasized that the data on such flights is still meagre especially for flights with heavy payloads and larger balloons. It has been also shown that it is safest to use balloons made out of grey coloured film which retains its flexibility with the absorption of solar radiation, the success obtained with such balloons so far being 100%. The drawback, however, is that these balloons cannot be used for night flights. Stratospheric wind regimes over Hyderabad are also discussed with a view to determine the period over which long duration flights can be made. The data available, however, is meagre and it is recommended that more frequent special wind ascents be made to collect adequate statistical data from which reliable conclusions could be drawn through critical analysis.     

Properties of tandem balloons connected by extendable suspension wires

The tandem balloon system has been known as a candidate system for long duration flight balloons. In this paper, the properties of the system are analytically studied in a new way by introducing an extendable suspension wire in the Sky Anchor configuration, which consists of a zero-pressure main balloon suspending a payload and a super-pressure balloon suspended below the payload. It was found that extension of the suspension wire between the payload and the super-pressure balloon can extend the capability of the tandem system; the altitude of the zero-pressure balloon can be changed without any consumables except some energy, and the day–night oscillation of the balloon altitude can be suppressed. This property is useful as the vehicle for long duration flights. It is also pointed out that the method to control the altitude of a balloon using an additional suspended super-pressure balloon can also be applied for super-pressure balloons.     

Medium energy gamma ray astronomy with transpacific balloon flights

Transpacific balloon flights with the University of California, Riverside (UCR) double scatter telescope are discussed. With flight durations from 5 days up to perhaps 15 days the long observation times necessary for medium energy (1–30 MeV) gamma ray astronomy can be obtained. These flights would be made under the auspices of the Joint U.S.-Japan Balloon Flight Program at NASA. We propose that flights can provide at least 30 hours of observation time per flight for many discrete source candidates and 120 hours for detecting low intensity cosmic gamma ray bursts.