Aspects of the disclosure relate to manufacturing a balloon envelope for use in a stratospheric balloon system. For instance, a stream of polyethylene mixture us extruded through an extruder in order to orient molecules of polymer chains of polyethylene and to provide an oriented film. The oriented film is passed through an electron beam and thereby crosslinking the polymer chains to provide a cross-linked film. The cross-linked film is heat sealed to form the balloon envelope

Aspects of the disclosure relate to systems and techniques for inspecting seals for high altitude balloons. In one example, a system may include a reflective surface, a translucent material on the reflective surface, and a movable light source configured to move along the reflective surface and provide light to the reflective surface. The light is provided such that it is reflected from the reflective surface and through the translucent material in order to backlight a balloon envelope seal for inspection. A method for inspecting a balloon envelope seal may include placing balloon envelope material on a table, forming a seal between portions of the material, moving a light over the seal, shining light onto a reflective portion of the table below the seal to backlight the seal, and inspecting the seal using the backlighting of the seal.

The first electrode section (7a) and the second electrode section (7b) are formed such that the outer portion connected to the upper portion of the heating section (6) is thinner than the inner portion connected to the lower portion of the heating section (6). The heating section (6) and the first electrode section (7a) are interconnected by an R-shaped first connecting portion (21). The inner circumferential sloping surface of the heating section (6) and the second electrode section (7b) are interconnected by an R-shaped second connecting portion (22). The first and second connecting portions (21)(22) are formed such that R becomes larger from the upper end to the lower end, where the upper portion is thin and the lower portion is thick. The thickness of an intermediate portion (6b) is smaller than the thicknesses of the first and second connecting portions (21)(22).

Aspects of the disclosure relate to techniques for manufacturing a balloon envelope. In one example, a first sheet of material for a first gore of the balloon envelope is provided. Lap seal material is arranged at least partially on the first sheet of material. A first heat seal is created between the lap seal material and the first sheet of material. A second sheet of material for a second gore of the balloon envelope is arranged over the first heat seal. A second heat seal is created between the lap seal material and the second sheet of material such that the lap seal material is configured to provide additional structural support to the balloon envelope.

A method and apparatus for sealing a plastic enclosure is provided. The apparatus includes a handle including elements pivotally coupled together at a first end. The apparatus also includes a heating element positioned along an inner surface of an element and connected to a power source where a longitudinal axis of the heating element is oriented parallel with a longitudinal axis of the element. Plastic material including first and second plastic layers is positioned at an interface between the second elements. Upon pivoting the first elements from an open position to a closed position the heating element increases a temperature at the interface to melt the plastic material and form a seal between the first and second plastic layers.

A sealing device generally includes a rotatable support cylinder having an outer, circumferential surface and a heating element disposed about such surface and secured thereto such that the heating element rotates therewith. The heating element is coiled about the outer surface of the cylinder in the form of an overlapping helical pattern. Juxtaposed film plies may be sealed together by bringing the sealing device into rotational contact with the juxtaposed film plies and heating the heating element to a temperature sufficient to cause the film plies to seal together.

An assembly for manufacturing a balloon envelope includes a table component and a sealing component. The table component may include a first platform, a second platform, a third platform, and a lateral opening between the first and second platforms. The first and second platforms can receive a first sheet of material that forms a first gore of the balloon envelope and a second sheet of material that forms a second gore of the balloon envelope. At least a portion of the first platform may move relative to the third platform so as to allow for the tendon and the portion of the second sheet attached to the tendon to move toward the third platform. The sealing component may be configured to bond the first sheet to the second sheet in order to join the first and the second gores of the balloon envelope.

Aspects of the disclosure relate to techniques for manufacturing a balloon envelope. In one example, a first sheet of material for a first gore of the balloon envelope is provided. Lap seal material is arranged at least partially on the first sheet of material. A first heat seal is created between the lap seal material and the first sheet of material. A second sheet of material for a second gore of the balloon envelope is arranged over the first heat seal. A second heat seal is created between the lap seal material and the second sheet of material such that the lap seal material is configured to provide additional structural support to the balloon envelope.

A sealing device generally includes a rotatable support cylinder having an outer, circumferential surface and a heating element disposed about such surface and secured thereto such that the heating element rotates therewith. The heating element is coiled about the outer surface of the cylinder in the form of an overlapping helical pattern. Juxtaposed film plies may be sealed together by bringing the sealing device into rotational contact with the juxtaposed film plies and heating the heating element to a temperature sufficient to cause the film plies to seal together.

Aspects of the disclosure relate to systems and techniques for inspecting seals for high altitude balloons. In one example, a system may include a reflective surface, a translucent material on the reflective surface, and a movable light source configured to move along the reflective surface and provide light to the reflective surface. The light is provided such that it is reflected from the reflective surface and through the translucent material in order to backlight a balloon envelope seal for inspection. A method for inspecting a balloon envelope seal may include placing balloon envelope material on a table, forming a seal between portions of the material, moving a light over the seal, shining light onto a reflective portion of the table below the seal to backlight the seal, and inspecting the seal using the backlighting of the seal.