Stratospheric Balloons: Science and Commerce at the Edge of Space

By Manfred “Dutch” von Ehrenfried

Stratospheric balloons are powerful tools used to study the Earth and its atmosphere, as well as the greater cosmos beyond. This book describes the science and technology behind modern stratospheric ballooning, along with the surprising ways it has impacted our daily lives.
The book takes you through every step of the process, starting with an in-depth introduction to basic balloon types and their uses before delving into balloon construction and mission planning. Along the way, you will learn about the novel technologies that have radically changed these balloons and their ability to launch, control and navigate them over specific ground targets. Next follows an exploration of their incredible applications, including research in atmospheric science, cosmology and astronomy, earth studies, meteorology, and aerobiology, and also commercial capabilities such as Internet networks and high-altitude tourism.
The community of scientists,engineers, and entrepreneurs involved in stratospheric ballooning is only ever growing. This book shows you how these national and international efforts have truly soared in recent years, and it will be an enjoyable read for anybody interested in learning more about how science and commerce are conducted in the stratosphere, at the edge of space.

• Language: English
• Publisher: Springer
• Release date: Mar 4, 2021
• ISBN: 9783030681302

Book preview

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021

M. von EhrenfriedStratospheric BalloonsSpringer Praxis Bookshttps://doi.org/10.1007/978-3-030-68130-2_1

1. Introduction

Manfred Dutch von Ehrenfried¹  

(1)

Cedar Park, TX, USA

A Brief History

Balloons have been around for over two hundred years. Some accounts go back three hundred years. Louis XVI and Marie Antoinette loved to watch them. So did Benjamin Franklin and his son, who witnessed some of the first flights. Certainly one of the first scientists ever to go aloft was Jacques Charles, French inventor, scientist, mathematician, and balloonist. Today, we know him best by Charles’ Law that describes how a gas expands as the temperature increases; conversely, a decrease in temperature will lead to a decrease in volume. This fundamental law of physics is known to every balloon scientist. But two thousand years earlier, Archimedes of Syracuse discovered an even more basic law when thinking about floating bodies and buoyancy. Balloons are, indeed, floating bodies buoyed up by the weight of the air they displace.

Balloons have been used for just about anything you can think of, be it for good or for ill. It only took eleven years after the first untethered balloon flight for the French to realize the military applications of the technology. The first use was on June 2, 1794 for reconnaissance during an enemy bombardment. Fast forward less than a hundred years and Thaddeus Lowe was telegraphing a message to President Lincoln to demonstrate the balloon’s application during the Civil War. He soon became Chief Aeronaut of the newly formed Union Army Balloon Corps. Of course, there was a little bit of unrecognized technology transfer going on even then. Count Ferdinand von Zeppelin, then aged 24, was visiting the U.S. and observing Lowe’s flights. He took his new found knowledge back to Prussia and certainly capitalized on what he learned about balloons.

Fast forward only to the end of the 19th century, and there were two French meteorologist sending up sounding balloons with instruments. Two Prussians, Professor Reinhard Süring and Dr. Arthur J. S. Berson ascended in balloons to take temperature and pressure readings. At 10.8 km (35,432 ft) they dozed off from lack of oxygen, but luckily they awoke in time to land safely. Professor Richard Assmann and Leon De Bort published a paper in 1902 that vertically separated the atmosphere into the troposphere and stratosphere. A quarter of a century later, the Manual of Meteorology said this was the most surprising discovery in the whole history of meteorology.

While this book is not a history of human balloon flight, there was certainly some balloon science going on at altitude during the 1920’s and 30’s but the frailties of man clearly showed it was not the place to be for very long. Many people died in balloon accidents caused by everything from fire, hypoxia, and altitude sickness to crashes. It was clear that more science could be obtained with uncrewed flights.

If ever there was a first family of the stratosphere then it would be the Piccards. This includes Auguste Piccard, his twin brother Jean, Jean’s wife Jeannette, and their son Don who, with Ed Yost, was the first to cross over the English Channel in a hot air balloon, plus Bertrand, grandson of Auguste, who, with Brian Jones, was the first to fly around the world in a balloon.

Advance just another generation or so to WWII and the Cold War and we saw the Japanese bombing the U.S. using balloons, and the U.S. using balloons to spy on Russia and to explode nuclear weapons in the atmosphere.

Now we are using balloons for science as well as commerce, even for providing internet services to remote areas and to those impacted by natural disasters such as hurricanes.

Today

This book is all about balloons rising through the troposphere and deep into the stratosphere, even into the mesosphere. For the general observer the troposphere reaches beyond the tops of the thunder clouds, which can go as high as about 20 km (65,600 ft). Most of the clouds you see are in the troposphere. But there can also be clouds in the stratosphere, which extends from the top of the troposphere up to what is generally defined as the top of the second layer at 50 km (164,000 ft), although this boundary varies with latitude. One can rarely see the clouds in the mesosphere; for example, noctilucent clouds or night shining clouds, which are tenuous cloud-like phenomena that occur in the upper atmosphere. They are the highest clouds and are located in the mesosphere at altitudes of around 50 to 85 km (164,000 to 279,000 ft). This is an area above the maximum altitude for aircraft and balloons, but below the minimum altitude of orbital vehicles. The mesosphere is the least understood portion of the atmosphere. It is of scientific interest but is beyond the current capabilities of balloons, although a couple of balloons have reached the lower levels for short periods. Sounding rockets have only brief access to the mesosphere and provide much less data.

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Fig. 1.1

The atmosphere. A look at our atmosphere from the U.S. Space Shuttle with cumulonimbus clouds, the troposphere (orange), stratosphere (white-blue), and mesosphere (dark blue) areas indicated. Photo courtesy of NASA.

Balloon flights in the lower troposphere have to contend with various winds and the decrease of temperature and pressure with altitude. In the upper troposphere there have been major problems due to the extremely low temperatures and their effects on the envelope of the balloon. The temperature averages −51°C (−60°F) near the tropopause, the boundary with the stratosphere. The film of the envelope can become very brittle. Balloons have failed and their missions lost. NASA and their balloon manufacturers made major efforts to investigate this problem and to develop and test alternate films to solve it; successfully. Then in the stratosphere the temperature begins to increase, attaining an average of −15°C (5.0°F) near the mesosphere.

The stratosphere is stratified (layered) in temperature, with warmer layers higher and cooler layers nearer the Earth. This increase of temperature with altitude is a result of the absorption of the Sun’s ultraviolet radiation by the ozone layer. This is in contrast to the troposphere below, in which the temperature decreases with altitude. Temperatures also vary within the stratosphere as the seasons change, reaching particularly low temperatures in the polar winter night. The winds in the stratosphere can reach nearly 209 km/h (130 mph) in the southern polar vortex. Balloon scientists seem to love to fly astrophysics balloons there, watching them circumnavigate Antarctica and then recovering their payloads nearby.

Over just the past generation the sophistication and complexity of payloads has steadily increased, in some instances potentially yielding scientific returns that can rival or exceed what can be accomplished in a much more expensive orbital mission. In fact many instruments and components flown, tested and developed on balloons are later adapted for spacecraft.

Scientific balloons have been perfected with the unique capability for ultra-long duration flight above 99.5% of the atmosphere, widely referred to as the edge of space. They are unique in being able to maintain sustained flight altitudes in the upper stratosphere, enjoy a relatively short development time from the inception of a scientific research project and flight, and expand the frontiers of Earth and space sciences at low cost. Scientific balloons carry considerable payloads and can enter the stratosphere and remain there for extended periods of time, all the while obtaining data to provide a better understanding of the world, or in some cases the universe. The demand for balloon flights outstrips NASA’s ability to launch them. At any given time there is often a backlog of missions waiting for flight which both delays the delivery of science to the community and increases its associated cost.

Launch Sites

Scientists are very particular about where they want to launch their precious balloon payloads. They have spent years designing them for a specific purpose and have spent a lot of time, energy and money on them. Some want to go as high as possible, some want to carry as much weight (payload) as possible, some want to stay aloft as long as possible, and some want to go to a specific geographical area or look in a particular direction. All of these different requirements dictate a launch site, or a select number of sites. Hence, considering the number of nations involved in ballooning there are many sites around the world.

NASA operates several sites for those missions designed for test and technology evaluation that offer safety and satisfactory air traffic control. Some of those also satisfy scientific requirements. NASA has agreements with the National Science Foundation (NSF) to use their site at Williams Field in McMurdo, Antarctica as well as agreements with Australia, Sweden, New Zealand, Brazil, and others. International scientists also use these as well as their own launch sites. This book discusses all the different organizations, both foreign and domestic, involved with stratospheric balloons. There are tens of thousands of people all over the world involved in scientific ballooning, not counting those involved in sport ballooning and world competition.

Some commercial companies have developed their own launch site capabilities and have made arrangements with their sponsor countries. For example, Loon launches many flights from Puerto Rico, Kenya and other countries where they support the government by providing internet services. World View Enterprises launches balloons from their Tucson, AZ facility. Those wanting more northern latitudes use sites in Norway, Sweden and Canada. There are also launches from sites in France, Spain, India, Hawaii, China and Japan.

Small balloons such as weather balloons are launched from hundreds of locations all over the world. It is interesting that high school and college students often use small balloons for experiments that are launched locally, in coordination with air traffic control.

The Future

There are balloons planned for the near future whose wide-field-sky imaging capability meets or exceeds that of the Hubble Space Telescope, expanding on that heritage of discovery at a fraction of the operational cost. The operational cost of Hubble is $98 million per annum and it is over subscribed. So scientists are employing the latest in balloon design and instrumentation to achieve their objectives. Because many flights were canceled in 2020 owing to the Covid-19 pandemic there is a backlog for the 2021 manifest. Antarctic flights must fly in the austral summer, hence there is a relatively short window in December and January for observation and recovery of their experiments.

Commerce

While science teams are developing the latest designs and preparing for the next season of ballooning, there is another group who are new users of balloons: the commercial balloonists. Balloons have progressed into many aspects of the world of commerce. Once balloon meteorologists and engineers had conquered the winds they were no longer at their mercy. The hot air balloonist would drift anywhere and everywhere, even into power lines, houses and lakes, but modern balloonists have learned to exploit the winds to their advantage. Even Columbus knew he had to use the wind for both speed and navigation on the ocean. These new balloonists have used the latest state of the art in meteorology to pick and choose the best altitudes to navigate to their desired targets and even to persist in the vicinity of their targets. In effect balloons are now providing a needed and marketable set of services, rather than just drifting with the wind and acquiring scientific data along the way. Nevertheless, the flight controllers cannot always tame the winds and many a payload has been lost at sea.

Delivering internet services to unserved and underserved regions of the world, the Loon Project is somewhat representative of balloon commerce up thru 2020. This service also includes providing emergency services on a demand basis when a disaster strikes. They have learned to launch constellations of balloons, using an autolauncher that puts one balloon up after another. Up until 2021, they have been launching more balloons than NASA or anybody else.

Other international companies are also competing for this type of service. One, the High Altitude Platform Station (HAPS) Alliance, has the target of ensuring member companies can collectively advocate for HAPS business development with the relevant authorities in various countries to create a cooperative HAPS ecosystem, develop common product specifications and promote standardization of HAPS network interoperability. All of these activities are key to the Alliance’s aim of creating new value by providing telecommunications network connectivity worldwide through the utilization of high altitude vehicles including balloons and aerostats. Other balloon commerce is structured to provide basic services across the spectrum to the point of designing, manufacturing, launching and recovering customer payloads, be these scientific, commercial, safety or military. There are such companies all around the world.

One company, World View Enterprises built a huge balloon complex in Tucson, AZ and started off by providing internet services and supporting some scientific missions, then expanded to providing a broad range of services for both science and commercial flights. In 2019-2020, they continue to develop their Stratollite balloon and Stratocraft gondola, making several test flights called GRYPHON. Two of the original owners of World View Enterprises started another company, Space Perspectives to provide flights for tourists to the edge of space. They have plans to launch tourists from the Kennedy Space Center’s Space Shuttle landing area and recover them in the Atlantic Ocean for return to Florida on a ship. They are also considering other locations including landing in the Gulf of Mexico and off Hawaii in the Pacific Ocean.

The vision of the commercialization of stratospheric balloons has reached the point where a company can advertise their products by photographing them from 30 km (100,000 ft) with the curvature of the Earth in the background and stream the images to the internet, and then to their customers and prospects. But this is nothing new. Even the Montgolfier brothers teamed with wallpaper manufacturer Jean-Baptise Reveillon to construct their balloon with beautiful, embellished art to advertise their wall paper designs.

But the well-funded companies have some competition. There are high school children who, for a modest price, will launch just about any small, lightweight object into the stratosphere, including a picture of a wedding couple or a bobble head doll of Captain Kirk, and provide an image of it with the curvature of the Earth in the background. In addition to basic laws of physics they have learned the rules of supply and demand – the tools of finance and entrepreneurship. The balloon world has evolved from Noble Prize winning science to the essence of human nature.

Educating the Next Generations

One of the primary objectives of this book is to provide reading and reference material that interests the next generation of balloon users, scientists, engineers and technologists. Balloons have historically played a major role in education. Over the years, experiments flown on scientific balloons have helped to develop future scientists. It is possible for undergraduate and graduate students to design and conduct a balloon based scientific study within 2 to 5 years required to get a degree. Professors are developing many of the latest scientific balloon payloads with team members from the graduate and undergraduate student body.

Hopefully this book will prompt students to pursue studies for careers in balloon related science and technology, giving them a foundation of knowledge germane to the current and future worlds of ballooning, because the future of this world is highly promising. Many balloon corporations and government agencies (such as NASA) have programs to teach students, of all ages, about science, technology, engineering and mathematics (STEM) and their applications to ballooning. This applies to international organizations as well. There are literally thousands of students involved in ballooning, launching their experiments and learning about the roles of balloons in acquiring scientific data. After graduation, students that are going after advanced degrees often work with established science teams and gain practical field experience. Many go on to obtain their masters and doctoral degrees.

Scientific ballooning is an excellent environment in which to train graduate students and young postdoctoral scientists. Many leading astrophysicists gained early experience in the balloon program including Nobel laureates Victor Hess, John Mather and George Smoot. So too did former astronaut and NASA Chief Scientist John Grunsfeld. Precursors for the detectors developed for the Cosmic Background Explorer (COBE) satellite were tested first on balloon flights, and probably half of the COBE science team were former balloon scientists. This is probably true for many other satellite experiments as well. Many other balloon scientists have received national and international acclaim. This book describes many balloon missions, giving the names and affiliations of the participants as well as pictures of some of the teams, the payloads, instruments, balloon types and missions. There are also appendices, references, and internet video links to interesting historical and educational resources.

Someday, the experiences gained using stratospheric balloons will provide us with the technology to fly in the atmospheres of Venus and Mars. I hope that a student who reads this book will be inspired to become one of the engineers or scientists on such a mission.

Image Link

Fig. 1.1

https://​www.​esrl.​noaa.​gov/​gmd/​news/​CumulonimbusInTw​ilight%20​w-labels.​jpeg

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021

M. von EhrenfriedStratospheric BalloonsSpringer Praxis Bookshttps://doi.org/10.1007/978-3-030-68130-2_2

2. Stratospheric Balloon Descriptions

Manfred Dutch von Ehrenfried¹  

(1)

Cedar Park, TX, USA

2.1 Types

NASA ’s Balloon Program Office uses multiple types of balloons to lift science payloads into the atmosphere. The same is true for both U.S. and international commercial organizations. In general, a balloon used to launch a payload to an altitude of 18 km (60,000 ft) or more is designed for stratospheric flight. A few are even capable of briefly reaching into the lower part of the mesosphere, which is generally considered to be 50-80 km (164,000-262,000 ft), although such an altitude is not currently sustainable. NASA officials have said the zero-pressure balloon called the Big 60 set a new sustainable record by reaching 48.5 km (159,000 ft) during an 8 hour flight on August 17, 2018, traveling well into the stratosphere and ascending 8 km (5 mi) higher than the next-largest balloon prototype.

Stratospheric science balloons are not weather balloons, although some weather balloons can climb out of the troposphere (where the weather is) to penetrate the stratosphere. A weather balloon, also known as a sounding balloon, is a type of high altitude balloon that carries instruments aloft to send back information on atmospheric pressure, temperature, humidity and wind speed by using a small, expendable measuring device called a radiosonde. To obtain wind data, they can be tracked by radar, radio direction finding, or navigation systems such as the satellite-based Global Positioning System (GPS). Balloons that must remain at a constant altitude for long periods of time are known as transosondes. Weather balloons that do not carry an instrument package are used to determine upper-level winds and the heights of cloud layers. For such balloons, a theodolite or tracking station is used to track the balloon’s azimuth and elevation, which are then converted to estimated wind speed and direction and/or cloud height, as applicable.

Weather balloons, as compared to scientific stratospheric balloons, are usually made of a highly flexible latex material, though chloroprene (a synthetic rubber) may also be used. They are generally filled with hydrogen, but occasionally the more expensive helium. When released, the balloon is about 1.5 m (~5 feet) in diameter and gradually expands as it rises owing to the decrease in air pressure. When the balloon achieves a diameter of 6 to 8 m (20 to 25 feet) in diameter it bursts. A small, orange colored parachute slows the descent of the radiosonde, minimizing the danger to lives and property.

Weather balloons typically fly to ~35 km (~115,000 feet) but they can achieve ~40 km (~131,000 ft) or more. The altitude is limited by diminishing pressures causing the balloon to expand to such a degree that it disintegrates. Above that altitude, sounding rockets are used. For even higher altitudes, it is necessary to launch satellites. In 2002 one weather balloon set an altitude record of 52.7 km (173,000 ft). See Chapter 9 for details of the National Weather Service.

While weather balloons are about the size of a man, a scientific stratospheric balloon can be the size of a football stadium. They are of a fantastic size, but provide fantastic science and real-world applications. In the U.S., they are the responsibility of the NASABalloon Program Office (BPO) at the Wallops Flight Facility (WFF) of Goddard Space Flight Center, which supports numerous space and Earth science research missions. There are different balloons to meet various scientific requirements. The two types of balloons currently used by NASA , as well as other organizations, are zero-pressure and super-pressure . Either type of balloon can be used for any flight, but zero-pressure balloons typically are used for short flights and super-pressure for Long Duration Balloons (LDB) or Ultra Long Duration Balloons (ULDB).

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Fig. 2.1

Balloon types. Graphic courtesy of NASA /WFF /BPO

2.2 Zero-Pressure Balloons (ZPB)

Zero-pressure balloons are so called because the atmospheric pressure inside the balloon is the same as the atmospheric pressure outside the balloon, giving zero-pressure at the point where the duct opens to the atmosphere.

With a zero-pressure balloon, additional layers of material are added outside the shell layer to handle the higher gas pressure toward the top of the balloon. These caps are added in a graduated manner to handle the increased loads; that is, the caps are of different lengths down the gore with the maximum number of caps at the apex of the balloon.

The zero-pressure balloon carries the scientific instrument to a density altitude which is determined by the total mass of the system (suspended mass plus the balloon mass) divided by the fully inflated balloon volume. The balloon is only partially filled at the time of launch and expands to reach its full volume as the balloon approaches its float altitude. NASA currently uses helium as the lifting gas.

The zero-pressure balloon has openings to the atmosphere, called vent ducts, to release the excess gas known as free-lift, which provides the lifting force during ascent. The balloon will continue to float at its equilibrium-density altitude until there is a change in the radiation environment, such as occurs at sunrise or sunset and upwelling Earth thermal flux. At sunset, the gas cools, the volume decreases, and the balloon falls about ~9-15 km (~30,000-50,000 ft) to a lower equilibrium altitude determined by the atmospheric temperature lapse rates and the radiation environment. Altitude can be maintained by the reduction in total system mass through release of ballast, which nominally amounts to about 8% per day. Thus flights are limited by the total mass available as ballast. The duration of a flight is typically 5-6 days in the mid-latitudes but much longer flights are possible at the poles in the summer time when the Sun doesn’t set and cause the balloon to cool.

ZPB characteristics are:

The balloon is inflated though sides.

When the balloon reaches float altitude, excess helium vents out from ducts.

The balloon uses load tapes to carry suspended load.

The balloon shell/envelope is made of 0.8 mil (0.0008 in) single layer co-extruded Linear Low-Density PolyEthylene (LLDPE) film.

Requires diurnal ballast (6-8% of system mass) to stay floating overnight.

The flight missions are conducted from various U.S. and foreign sites throughout the world. Over the past several years, the NASA Balloon Program has delivered successful performance across the spectrum of balloon sizes, an accomplishment that is unprecedented in ballooning given the large, heavy balloons that comprise most of the program today. The program presently has five standard conventional zero-pressure balloon designs ranging in volume from 30,000 m³ (1.06 million ft³) to 1.13 million m³ (40 million ft³). The largest of these standard balloons will lift in excess of 3,600 kg (8,000 lb) to an altitude of higher than 37 km (121,000 ft). New balloon designs using spin-off ULDB technologies are under development to fly higher and heavier payloads. (See the LDB and ULDB sections below.)

For the Antarctic Impulsive Transient Antenna (ANITA) the balloon is a typical zero-pressure balloon but the untypical payload has shaken the theoretical and experimental physics worlds with its observations of peculiar particles coming from the ice below. See Section 8.​1.​2 for details.

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Fig. 2.2

The ANITA prior to launch. Photo courtesy of NASA

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Fig. 2.3

The ANITA II ascent with insert. Photo courtesy of NASA

The following are the ANITA I’s specifications (balloon sizes can vary):

Volume: 830,000 m³ (29.47 million ft³).

Gore Length: 180.6 m (592.4 feet).

159 gores.

Film Thickness: 0.8 mil (0.0008 in) (20 μm).

Inflated height: 102 m (335 ft).

Diameter: 129 m (424 ft).

Vent Duct Diameter 3.8 m (12.6 ft).

Note that balloon envelope thickness is generally expressed in units of 1 millionth of a meter, or micron, using the ‘μ’ symbol of the Greek alphabet. Sometimes the American standard is used; mil, which is one thousandth of an inch.

2.2.1 Ultra High Altitude Balloon (UHAB)

Since the start of scientific ballooning, researchers have sought to lift increasingly heavier, more sophisticated, payloads to higher altitudes. In the 1960’s and 1970’s advances in film extrusion and balloon fabrication techniques enabled the creation of increasingly larger balloons, culminating with a 1.5 million m³ (53 million ft³) behemoth successfully launched in 1975. The ability to create significantly larger balloons was constrained primarily by limitations in materials, including films.

BU60-1

The Japanese Institute of Space and Astronautical Science (ISAS) launched a balloon in 2002 designated BU60-1 to test the flight performance of an envelope manufactured with a newly developed ultra-thin film only 3.4 μm thick made of polyethylene. It had a volume of 30,000 m³ (1.06 million ft³). The empty weight of this balloon was only 60% of conventional high altitude balloons of the same volume. It reached an altitude of 53 km (173,900 ft) which broke the previous record set in 1972. As 1 μm equals roughly 0.00004 in, the film was 3.4 times that, or 0.000133858 in thick. See Section 3.​1.​5 for a discussion on Ultra-Thin Films.

Big 60

The UHAB development started in March 2002, when NASA requested Raven Industries to undertake a study on a series of ultra-high altitude zero-pressure balloon platforms. After analyzing several load-altitude targets, NASA chose a 1.7 million m³ (60 million ft³) design with an ultimate payload capacity of 750 kg (1,653 lb). The balloon was designed using traditional zero-pressure techniques, but the shell and cap material was chosen to be Stratofilm-430, which was based upon the Stratofilm-420 developed for the ULDB program. It comprised a three-layer co-extruded film using the same resins as Stratofilm-420. The overall film thickness was 10.2 μm (0.40157 mil) for the shell and 13.2 μm (0.51965 mil) for each of the two cap layers. Relative to traditional zero-pressure balloon film, the Stratofilm-430 had higher strength and ductility at normal surface temperatures, enabling the shell to better withstand dynamic launch loads.

Production of the balloon, unofficially christened the Big 60, required some minor rearrangement of production space at the Raven factory to accommodate the almost 230 m (756 ft) gore length. That’s twice the length of a football field including the end zones. They did it using two tables half the length. Due to its similarity to standard zero-pressure designs, the fabrication of the balloon was relatively straightforward and uneventful. Because of the delicate film, special considerations were made for the process of expelling excess air and loading the balloon. The film limits are always based on current material strength capability. Balloon films with increased strength-to-weight ratios greatly increase payload capabilities for missions requiring flight above 50 km (164,000 ft).

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Fig. 2.4

The Big 60 with its reflection in Lynn Lake. Photo courtesy of NASA /WFF /CSBF

The payload was the Low Energy Electron (LLE) experiment. The observations from LEE provided one of the few highly precise measurements of the electron spectrum over an extended period of time. The first test flight number 508N was conducted on August 25, 2002 at Lynn Lake Airport, Manitoba, Canada. After a successful launch, the balloon climbed to a peak altitude of 49.4 km (162,000 ft) and was terminated normally after approximately 23 hours of flight time. As the largest balloon ever successfully flown, it beat the world record set in 1975.

The next launch using the Big 60 was flight 685NT from Fort Sumner, NM on August 17, 2018. This flew for a total of 8 hours and reached an altitude of 48.5 km (159,000 ft). One of the additional experiments was an advanced spherical steerable antenna system developed by FreeFall Aerospace of Tucson, AZ, in partnership with the University of Arizona. It was located in the left side of the gondola in a specially added frame, while in a similar structure in the right side was a parabolic antenna also built by FreeFall Aerospace. The other experiment was the CHERP (CHErenkov Radiator Payload) supplied by Gannon University in Erie, PA. This was a cosmic ray instrument to detect high-energy particles of astrophysical origin in the energy range from 1.5 to 20 giga-electron-volt using two Cherenkov radiation detectors.

A second test, flight number 687NT was also launched using the same dynamic method on August 25, 2018. After a slow ascent lasting over 4 hours, the Big 60 reached a float altitude above 47 km (155,000 ft). During the ascent the balloon moved initially to the northeast, but later on acquired a more or less stable flight path to the west with a slight deviation north that would be unaltered during the remainder of the flight. During the flight the balloon experienced some drops of altitude that could be have been related to the presence of a very cold storm front in the area. It flew for 9 hours 40 minutes.

The Big 60 is NASA ’s largest zero-pressure balloon to date. If the polyethylene material were to be spread out on the ground it would cover about 20 acres. The larger size enables the balloon to float about 8 km (26,250 ft) higher than other zero-pressure balloons; equivalent to about 20 Empire State Buildings closer to the edge of space than NASA ’s next largest balloon.

In addition to its larger size, the Big 60 is also half as thick as the other balloons that NASA flies. At 10.2 μm (0.40157 mil) the plastic film covering the balloon is a little less than the thickness of kitchen plastic wrap. These films go through three stages of testing before they are flight ready, including quality control tests at the Balloon Research and Development Lab of the Wallops Flight Facility. In the stratosphere where the balloon floats, the temperature is typically –76°F, but the films are rated to withstand –130°F in the lab.

The Big 60 uses the CSBF designed gondola, which has support instrumentation such as tracking, video and telemetry, together with tertiary experiments flying to round out the 748 kg (1,650 lb) suspended payload. The test flights evaluated the Big 60’s overall design and ability to conduct science missions. Future tests will go a step further and allow researchers to test new instruments.

In addition to providing unprecedented altitudes for scientific observations, the UHAB also opened new avenues for long duration ballooning at mid-latitudes. With altitude excursions of only 10-12 km (6-7 mi), these balloons are able to execute long duration flights without the need for large quantities of ballast. If augmented by a small super-pressure anchor balloon, altitude excursions can be minimized. While not as capable as the ULDB for carrying heavy payloads, the UHAB would add another capability for scientists with relatively light payloads who desire to maximize mission time and altitude.

The UHAB platform further offers the opportunity to extend the duration of mid-latitude flights through the implementation of Radiation-Controlled Ballooning.

This concept was designed to take stratospheric measurement of cyclical radiation levels at different altitudes between 20-40 km (65,600-131,000 ft) in response to the daily cycles of solar radiation. These are referred to as RACOON balloons.

2.3 Super-Pressure Balloons (SPB)

The very first prototype of a super-pressure balloon was the one constructed in August 1783 by the Roberts brothers for Professor Jacques Charles (of Charles’ Law fame). It was a sealed hydrogen filled balloon constructed using a rubber coated fabric. It was unmanned and burst during the ascent. Then in December, Jacques and Nicolas-Louis Robert lifted off in a hydrogen balloon from the area that is now the location of the Eiffel Tower, and flew for over two hours. About 400,000 spectators were estimated to have watched, including Benjamin Franklin and his son.

Fast forward now about two hundred years to the modern era. There are opposing requirements among the users of both scientific and commercial balloons. Some want altitude, some want larger payloads, others want duration, some want to look at the Earth and its atmosphere, and others desire to look out toward the heavens. NASA not only faces the challenge of meeting the scientists’ requirements and providing the system capabilities but also has the responsibility to control costs while developing the necessary technologies and capabilities. At the same time, there were studies on various polyethylene films, advances in balloon systems technologies, and ground support systems and facilities in various locations.

In 1991, the Balloon Working Group was established to counsel NASA on the performance and plans of the NASA Balloon Program with particular emphasis on the operation and support of what was then known as the National Scientific Balloon Facility (NSBF).¹ The group is a forum for the exchange of information on balloon systems, operational support, and those scientific developments that affect the Balloon Program. There are 12 members, one of whom is the NASA Balloon Project Scientist who serves as Chairman. The others were appointed from the principal scientific disciplines that were served by ballooning and from the technical and management support areas of importance to the NASA Balloon Program. Members are appointed by the Director, Goddard Space Flight Center. The NASA Headquarters Balloon Program Scientist is an ex-officio member.

2.3.1 Program Goals

The goals for the development of the NASA Super-Pressure Balloon (SPB) are related to supporting a specific science mass lifted to a set stable altitude for an extended duration. The program level requirements for the SPB are as follows:

It shall be capable of lifting 1,000 kg (2,200 lb) of science instruments.

It shall be capable of sustained flight altitude of 33.53+ km (110,000+ ft).

It shall be capable of sustained flight with an allowable altitude variation of plus infinity (no limit on height) and minus 1,524 m (5,000 ft) during normal operations. (Rare, extreme low temperature events shall allow an occasional dip to lower altitudes.)

It shall be capable of sustained flight duration of up to 100 days.

Its function and performance shall be independent of science mission type.

2.3.2 The Balloon

In view of the program goals, it was determined that the SPB would be designed to be flown at any latitude on the globe regardless of day/night cycles, including mid-latitude flights. It will fly at a constant density altitude with a known mass of payload hanging from the balloon. It always maintains a positive internal pressure in relation to the environment in which it is floating. The SPB is a sealed structure filled with a measured and specific amount of helium lifting gas. The balloon rises after launch and the helium expands as the ambient pressure falls with increasing altitude. When the balloon reaches the desired float altitude the extra helium isn’t vented but fills out the shape and