The science of flight—Aerostatics, as it was known in the 19th century—became a reality as early as 1783, when the French brothers Montgolfier sent up a balloon using hot air heated by a fire on the ground. The Montgolfiers, only two months later, used a hydrogen-filled balloon to take three passengers: a sheep, duck, and rooster, into the air for King Louis XVI and his court.
By the time of the American Civil War, hot air was still not a practical method of lighter-than-air travel, as no device or fuel source had been employed that allowed a balloon to stay aloft for any length of time. Non-air gasses were therefore the main means of ascension.
Before the war, civilian balloonists, or aeronauts, used primarily “coal gas” from city lines. This was the same gas used to light street lamps in cities, and it was composed of hydrogen, carbon monoxide, and methane.
As war broke out, aeronauts volunteering their services for the US Army quickly found that it was extremely difficult, if not impossible, to fill their balloons in the cities and then tow them over rough terrain to join armies in the field. Before and en route to the First Battle of Bull Run at least four balloons, those of James Allen and John Wise, had already been lost to wind, trees, and telegraph poles. Another method was needed to inflate balloons in the field and to accommodate the stresses of battle!
The renown balloonist, John Wise, drew up plans for a portable apparatus based on the designs of late 18th century French aeronauts—it used a process called “water decomposition” to produce the combustible, but extremely light gas, Hydrogen. This process involved heating “iron turnings” and charcoal until white hot and then running steam into the material. The process, at the time, was sadly inefficient, however, and it was determined by the Franklin Institute of Philadelphia that using this proposed apparatus would require as much as 7,500 pounds of iron and other supplies, costing a total of $7,000 per inflation. The cost and inefficiency of this method made it impractical for military purposes.
Another young aeronaut, Thaddeus Lowe invented and had constructed another sort of portable generator: a wagon housed tanks of sulfuric acid, into which iron filings were deposited. The reaction gave off hydrogen, which moved into a leather hose and through two purifiers, and finally into the envelope of the balloon. This method and design was adopted by the army and proved practical even in the midst of battle. The generators could inflate a balloon in just over two hours (fast for the time) at a cost of only $60-$70—obviously superior to the water decomposition method. Lowe’s outside-the-box thinking brought him to the fore as chief aeronaut of the Union Army. His invention of the portable gas generators allowed him to effectively serve the Army of the Potomac through three major campaigns of the Civil War: the Peninsula, Fredericksburg, and Chancellorsville.