Gas Balloon

Overview

A gas balloon flies on the buoyancy of a light gas held in a closed envelope, not on heated air. Helium or hydrogen sealed inside the Envelope weighs far less than the air it displaces, and that difference lifts the craft. Unlike a hot-air balloon there is no burner, so flight is silent and can last for days. The trade is that the pilot cannot simply add heat to climb. Altitude is managed by venting gas to go down and dropping ballast to go up, and both are finite resources that have to be spent carefully across a long flight.

The load path is the defining feature. The envelope fabric is gas-tight but not strong enough to carry the basket, so the lift is collected by a Suspension Net cast over the whole envelope, gathered into a Load Ring, and passed down to the Basket. The fabric holds gas, the net holds weight.

Envelope

The Envelope is built from tapered Envelope Gore panels seamed pole to pole into a sphere, each panel in polyurethane-coated nylon. A Gas-Barrier Coating gas barrier slows the inevitable diffusion of helium or hydrogen, which sets the practical flight duration. At the base an open Appendix tube serves two jobs: it is the fill point on the ground, and in flight it stays open so gas can expand out as the balloon climbs into thinner air rather than bursting the envelope. Vertical Load Tape webbing along every seam channels envelope loads into the net, and a reinforced Valve Port Ring ring at the crown mounts the gas valve. For landing the envelope carries a sealed Rip Panel that is torn open to deflate fast.

Net and suspension

The Suspension Net is a knotted mesh of Net Cord draped over the envelope, reinforced where it gathers at the crown by Crown Tab tabs. The mesh narrows down to a set of Suspension Line ropes that meet at the Load Ring. Because the net wraps the whole upper surface, it spreads the lifting force evenly into the fabric instead of concentrating it at a few hard points, which is what lets a thin coated envelope carry a loaded basket.

Basket

Crew ride in the Basket, traditionally a Wicker Body woven from willow or rattan on a marine-plywood Basket Floor. Wicker is still used because it flexes on landing and absorbs impact better than a rigid box. A padded Rim Rail gives the crew something to brace against on touchdown, and the basket hangs from the load ring on four Suspension Cable corners. Wooden Landing Skid runners protect the base, and a Ballast Rail around the rim carries the ballast bags within easy reach.

Valve and lift control

Descent and deflation run through the Valve System. The Crown Valve at the top is held shut by a Coil Spring and a Valve Spring, and the pilot vents gas by pulling the Valve Line that runs down the centre of the envelope, then lets it reseat. A separate, deliberately coloured Rip Line is pulled only on landing to open the rip panel. Mixing the two lines up is dangerous, so they are kept visually distinct. Climbing works the opposite way: the pilot lightens the craft from the Ballast System.

Ballast and flight management

The Ballast System is how a gas balloon trims without fuel. Sand Ballast Bag units hang on Ballast Clip releases, and emptying one makes the balloon lighter so it rises. A long Trail Rope dragged near the ground gives automatic fine trim: when the balloon sinks, more rope rests on the ground and lightens the load, so it self-levels. A Drag Anchor grapnel is dropped to stop drift once the crew commit to landing. Managing this finite ballast against the slow, steady gas loss is the entire skill of the sport, which is why distance and endurance gas races reward careful pilots over many hours or days.

Instruments and use

The Instruments pack carries a barometric Altimeter, a sensitive Variometer that warns of climb or sink before it is large, a GPS Tracker tracker for the retrieve crew, and an aviation Aviation Radio. The electronics run on a Bare PCB with an Microcontroller, a Pressure Sensor, and a Power Supply. Gas balloons today fly mainly in distance racing such as long endurance cups, in scientific and atmospheric sampling roles, and in sport flying where the silence and long duration are the appeal. Hydrogen gives more lift and is cheaper but is flammable, so helium is used wherever cost and supply allow.