Text 1. Space-Age Welding: The Past, Present and Future of Aerospace Join Processes

By B.E. Paton  

April 10, 2003

On Oct. 16, 1969, astronauts performed the world's first welding and cutting experiment in a depressurized compartment. In flight aboard the

Soyuz 6 spaceship, they tested three welding processes with a semiautomatic Vulkan unit (see Figure    below): consumable electrode arc in vacuum, low-pressure plasma, and electron beam welding. They studied how to weld aluminum and titanium alloys and stainless steel. They verified the possibility of thermal-cutting these materials and investigated the behavior of molten metal and features of its solidification.

This experiment convinced experts that they could use automatic welding to produce permanent, tight joints in space. They expanded this work with a

Two _{cosmonauts conduct} series of investigations conducted under short-time ^{preflight training of a crew with} Vulkan hardware in October microgravity conditions in flying laboratories and

1969                                       space simulation test chambers. In 1973 NASA

experts conducted a flight experiment with electron

beam cutting, brazing, and welding in the Skylab orbital station.

Space welding technologies have advanced since then. In-space repair and construction of space facilities and their equipment and instrumentation were defined in the 1980s. Another major area identified was producing advanced material s in space with new or improved properties using different heat sources.  

Over the years scientists and specialists had to address construction of various experimental space vehicles, namely, orbital and interplanetary stations, radio telescopes, antennas, reflecting shields, and helio power generation systems - in outer space.

In addition to the original problems of assembly and erection in outer space, as well as their view of how long these vehicles would be used and increases in the vehicles' weight and dimensions, specialists focused more attention on preventive maintenance and repairs.

 

Initial Welding Experiments

The first welding experiments conducted in space demonstrated that arc welding processes, which were widely accepted on earth and at first were promising, had unfavorable characteristics in space, such as unstable, weakly constricted arc discharge; unstable globular transfer; and increased weld porosity.

During experimental retrofitting in simulation facilities-chiefly in space simulation chambers placed in flying laboratories-the difficulties related to these characteristics were successfully resolved. Specialized welding equipment and techniques also were developed for this purpose, and the required welding consumables often were selected from those used in the aerospace industry.

However, it was clear to space system developers that almost all maintenance and repair of long-term flying vehicles - for which neither the scope of work needed nor the components to be repaired and restored are known in advance-had to be performed manually with only partial mechanization. This increased specialists' interest in studying the possibility of manual welding in space, which led them to consider which of the existing welding processes to use. 

Welding processes such as electron beam, consumable and nonconsumable electrode arc in vacuum, flash-butt, hollow cathode, and helio welding were tested in vacuum chamber s and in flying laboratories at different stages of experimental studies in the 1970s and 1980s.

Technology and material versatility and minimal power consumption ultimately were deciding factors that led them to choose the electron beam process.   This process     allowed technicians to perform operations that could be required to produce a permanent joint in open space: heating, brazing, welding, cutting, and coating deposition.

But selecting this process didn't solve all the problems. As investigations progressed, the number of problems, technical and

_{Cosmonauts test an electron beam hand tool at the}           psychological, increased. An

Salyut 7 orbital station. opinion existed that this process, which involves high-accelerating voltage, the possibility of X-ray radiation from the weld pool, and manipulation of a sharply focused electron beam, couldn't be done manually.

A series of experiments in a ground-based, manned space simulation chamber enabled the engineers to solve the key technological and hardware issues and develop a flight sample of an onboard electron beam hand tool. In 1984 and 1986 this tool was successfully tried out on the outer surface of the Salyut 7 orbital complex (see Figure above). 

Based on new engineering systems that corrected technical parameters and suggestions from the test engineers and crews during experiments in the Salyut station, engineers developed a new electron beam hand tool in the 1990s. The tool passed lengthy testing at NASA's Marshall Space Flight Center and Johnson Space Center. During testing in a flying laboratory and at zero buoyancy, as well as in a manned space simulation test chamber in Russia, the developers were able to solve almost all the technical and procedural problems with the tool.

 

Further Aerospace Welding Exploration

Almost 40 years' experience of technology developments and their application leads to the conclusion that in this new century, major, complicated space work will have to be addressed. Welding technologies will be of tremendous importance.

Such technologies are partially in place, but further space exploration will require developing new welding, cutting, brazing, and coating processes. New exotic materials will be introduced in the new century, and their processing and joining will require completely new technologies. 

A number of space operations can be performed remotely, using robots and manipulators. 

Welding in space might become widely accepted only if completely new methods of nondestructive testing and diagnosing welded structures can be developed. This can be supported by data banks that allow automatic selection of the process and computer simulation.

Laser applications in space, including such hybrid processes as laser-plasma and laser-arc welding, offer promise, especially diode lasers. Friction welding and resistance seam-roller welding also are of interest.

Advanced space systems will continue to be developed both on the ground and in orbit. New welding and related processes and technologies will have an important role in those developments. 

 

B.E. Paton is director of the E.O. Paton Electric Welding Institute, Kiev, Ukraine.The E.O. Paton Electric Welding Institute is a multidisciplinary research institute that realizes fundamental and applied research works and develops technologies, materials, equipment and control systems, rational welded structures and weldments, and methods and equipment for diagnostics and nondestructive quality control. Paton also is president of the National Academy of Sciences of Ukraine.

 

Speaking

 

True or false?

 

1. The world's first welding and cutting experiment was carried out in the outer space.

2. Thermal-cutting of aluminium, titanium alloys and stainless steel is impossible in space.

3. Only automatic welding is of importance for aerospace.

4. A flight sample of an onboard electron beam hand tool was produced as a result of series of experiments.

5. Space welding is used for maintenance and repair purposes.

 

Translate the following sentences into English:

 

1. На борту космического корабля исследователи изучали поведение расплавленного металла и особенности его кристаллизации в условиях кратковременной микрогравитации.

2. Технологии космической сварки шагнули далеко вперед.

3. Одна из задач, решаемых с помощью сварки в открытом космосе, - профилактическое обслуживание и ремонт оборудования космического корабля.

4. Разнообразие используемых материалов и невысокая энергоемкость оборудования являются решающими факторами, обусловливающими возможность использования сварки в открытом космическом пространстве.

5. Дальнейшее освоение космического пространства потребует усовершенствования практически всех видов сварочных технологий, а также резания, пайки и нанесения покрытий.

6. Специфика используемого на космических кораблях оборудования обусловливает необходимость использования прежде всего ручной сварки при частичной автоматизации процесса.

7. Электроннолучевой ручной сварочный аппарат прошел успешные испытания на орбитальном комплексе в условиях открытого космоса. 8. Использование новейших материалов в следующем столетии потребует разработки совершенно новых технологий получения неразъемных соединений.

 

The title of the text under review is “Thepast, present and future of aerospace join processes”. Look through the text again and say which event relates to:

 

a) the past

b) the present

c) the future

 

The key words from the table below will help you

 

The past	The present	The future
1969, 1973, 1980s, 1990s, verifying the possibility of thermalcutting and welding in space	testing in a flying laboratory, the electron beam process, manned space simulation chamber, solving almost all the technical and procedural problems	completely new methods of nondestructive testing and diagnosing welded structures, advanced space systems development, new exotic materials

 

Vocabulary

down-hand welding	сварка в нижнем положении
celestial body	небесное тело
bend load	нагрузка на изгиб
welding sequence	последовательность сварки; порядок наложения швов
tensile load	растягивающая нагрузка
pressure load	сжимающая нагрузка, усилие сжатия
root pass	корневой шов, проход, сварка корневого шва
tolerance	допуск
manual welding	ручная сварка
post-polishing	последующее полирование
tack weld	прихваточный сварной шов, прихватка
X-ray testing (qualification)	рентгеновская дефектоскопия
high duty		жесткий режим
clamping fixture		прижимное устройство
ASME		American Society of Mechanical Engineers Американское общество инженеровмехаников
DIN		нем. Deutsche Industrie-Normen Немецкие промышленные стандарты
ID		inside dimensions внутренние размеры
U-shape (bend)		двойной изгиб; U-образное колено, двойное колено
grinding		шлифовка
weld seam		сварной шов
filler wire		присадочная проволока
saw blade		1) пильное полотно; пильная лента 2) ленточная пила; дисковая пила 3) режущий диск
bevelling		1) отточка косая 2) угол фаски 3) фацетирование
performance capabilities		1) возможности 2) рабочие характеристики
work piece

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