Hydrogen balloon

Just ten days after the Montgolfier brothers achieved the first manned hot-air balloon flight, Jacques Charles demonstrated an alternative approach that would prove superior. On December 1, 1783, Charles and Marie-Noël Robert launched from the Tuileries Garden in Paris before 400,000 spectators—half the city's population. Their balloon used hydrogen gas rather than heated air, representing a fundamentally different solution to the same engineering problem.

Charles had recognized immediately that hydrogen—'inflammable air' isolated by Henry Cavendish in 1766—offered advantages over hot air. Hydrogen is approximately fourteen times lighter than air, compared to the modest density reduction achieved by heating air. A hydrogen balloon could lift more weight, fly higher, and stay aloft indefinitely without requiring a constant fire. The adjacent possible had made both approaches feasible; Charles chose the more elegant path.

The engineering challenges were different from the Montgolfiers' approach. Hydrogen is a tiny molecule that escapes through any porous material; ordinary fabric was useless. Charles commissioned the Robert brothers, instrument makers, to develop a gas-tight envelope. Their solution used silk coated with dissolved rubber—a rubberized fabric that could contain the fugitive gas. The envelope weighed only 25 pounds despite holding 943 cubic feet of hydrogen.

Producing enough hydrogen was itself a manufacturing challenge. Charles supervised the generation of gas by reacting sulfuric acid with iron filings—a slow, expensive process that consumed nearly a quarter ton of acid and half a ton of iron. The inflation took several days. The cost was enormous: the demonstration reportedly consumed 10,000 livres (approximately £400, a substantial sum in 1783).

The flight exceeded all expectations. Charles and Robert ascended to 1,800 feet, crossed Paris, and landed 27 miles away near Nesles after two hours aloft. Charles then ascended alone—the first solo balloon flight—reaching an estimated 9,000 feet before a rapid descent caused by gas cooling and contraction. He reported the extraordinary experience of watching a second sunset as he rose above the earth's shadow.

The convergent development of hot-air and hydrogen balloons in 1783 demonstrated the adjacent possible at work. Both emerged from the same cultural moment: Enlightenment France's celebration of experimental science, royal patronage for spectacular demonstrations, and the accumulated chemical and materials knowledge that made lighter-than-air flight achievable. The Montgolfiers and Charles competed publicly, their rival approaches spurring rapid development.

Hydrogen balloons proved more practical for sustained flight. They didn't require carrying fuel or maintaining fires; they could stay aloft as long as their gas-tight envelopes held. The technology enabled the first aerial crossing of the English Channel (Jean-Pierre Blanchard and John Jeffries, 1785) and dominated lighter-than-air flight through the nineteenth century. Hot-air balloons persisted mainly for shorter recreational flights where simplicity outweighed performance.

The hydrogen balloon's descendants included the dirigible and the zeppelin—powered, steerable aircraft that seemed poised to dominate aviation until the Hindenburg disaster of 1937 ended the hydrogen airship era. The technology's eventual decline came not from any inherent flaw but from the rise of heavier-than-air flight: the airplane offered capabilities that no balloon could match.