Wan Hu's Rocket Chair — The First Attempt at Human Rocket Flight

Construct a heavy wooden chair from thick hardwood planks — oak, elm, or camphor wood were available in Ming dynasty China. The chair must be far stronger than ordinary furniture because it must withstand the combined thrust of 47 rockets firing simultaneously. The seat is approximately 50 cm wide and 50 cm deep, with a solid back rising 80 cm above the seat. The legs are thick and braced with cross-members.

The underside of the seat and the back of the chair are fitted with iron brackets and loops where the rocket tubes will be mounted. The brackets must distribute the thrust load across the wood grain — a single point of attachment would tear the wood apart under 47 simultaneous ignitions. Wan Hu's design reportedly placed rockets both beneath the seat (for vertical thrust) and behind the backrest (for forward thrust).

Build 47 individual rocket tubes following the fire arrow propellant tube method: roll mulberry bark paper tightly around a wooden dowel, building up 8-10 layers for additional strength (thicker than fire arrow tubes, since these must produce sustained thrust). Each tube is approximately 30-40 cm long and 3-4 cm in diameter. Seal one end with a clay plug and coat the exterior with tung oil lacquer.

The quantity — 47 — is specific in the legend and appears to be an engineering estimate rather than an arbitrary number. Assuming each tube produces thrust equivalent to a fire arrow (roughly 2-3 newtons for 3-4 seconds), 47 tubes firing together would generate approximately 100-140 newtons — enough to lift perhaps 15 kg briefly. Wan Hu and the chair together weighed far more than this. The mathematics were fatally wrong before the first fuse was lit.

Prepare approximately 750 grams of rocket propellant total (15-16 grams per tube × 47 tubes). Use the fire arrow ratio: 70% saltpeter, 16% charcoal, 14% sulfur. This is a dangerously large quantity of black powder to prepare at once — work outdoors, in small batches, and keep finished powder far from the mixing area.

Pack each tube with propellant using the same method as fire arrows: tamp firmly with a wooden dowel, leaving the rear nozzle end open. The consistency of packing across all 47 tubes is critical — unevenly packed tubes will ignite and burn at different rates, creating asymmetric thrust that would spin the chair rather than lift it. In practice, achieving this level of consistency with hand-packed black powder was nearly impossible with Ming dynasty technology.

Distribute the 47 rockets across the underside of the seat and behind the backrest. Bind each tube to its iron bracket using wet rawhide strips that shrink tight as they dry. The nozzle ends of all rockets must point downward (for those beneath the seat) or rearward (for those behind the back), directing thrust in a consistent direction.

Arrange the tubes in a symmetrical pattern to balance the thrust — any asymmetry will create torque that rotates the chair. Space the tubes far enough apart that a misfire in one tube does not immediately ignite adjacent tubes before their own fuses reach them. In reality, with 47 tubes packed closely on a wooden structure, a single premature ignition would have chain-fired every other tube in a fraction of a second.

According to the legend, Wan Hu held two large kites — one in each hand — intending to use them as wings for gliding control after the rocket thrust ended. The kites were traditional Chinese designs: bamboo frames covered with silk fabric, each approximately 2 meters in span.

The concept shows remarkable intuition about the problem of flight control, but the execution was fatally flawed. Kites generate lift only in moving air — they work when pulled against the wind by a string. Holding a kite while seated on a vertically ascending chair in calm air produces no useful aerodynamic force. Additionally, human arms cannot generate enough control authority to stabilize an object experiencing 100+ newtons of asymmetric rocket thrust.

Each of the 47 rockets requires its own fuse, and all must be lit within seconds of each other. Prepare 47 saltpeter-soaked hemp cord fuses, each approximately 30 cm long. Insert one end of each fuse into its respective rocket tube, ensuring contact with the propellant.

The plan called for 47 servants to light the fuses simultaneously on Wan Hu's command. Coordinating 47 people to perform the same action at exactly the same moment — in an era before synchronized timekeeping — introduced yet another fatal variable. Any rocket that ignited even two seconds before the others would begin producing thrust asymmetrically, potentially tipping the chair sideways before the remaining rockets could fire.

Wan Hu seated himself in the chair, gripping a kite in each hand. The 47 servants stood ready, each holding a lit torch beside their assigned fuse. On his command, all 47 servants touched their torches to the fuses simultaneously.

What happened next was the inevitable consequence of 750 grams of uncontained black powder igniting in rapid sequence on a wooden frame: a massive explosion. The individual rocket tubes, packed closely together on a combustible wooden structure, did not fire sequentially as planned — the heat and sparks from the first ignitions detonated adjacent tubes instantly, creating a single catastrophic fireball rather than sustained thrust.

When the smoke cleared, both Wan Hu and the chair were gone. The legend states he was never found. Modern analysis suggests the combined explosion was equivalent to approximately 1 kg of TNT — more than sufficient to destroy the wooden chair and fatally injure anyone seated on it. The dream was five centuries ahead of the available engineering. Wan Hu could not have known what he lacked: lightweight materials, precision nozzle design, fuel chemistry, and the fundamental equations of orbital mechanics that would not be written for another 200 years.

Wan Hu's experiment was doomed by at least five independent failure modes, any one of which would have been fatal:

1. Insufficient thrust: 47 small black powder rockets produce approximately 100-140 newtons total — enough to lift 14 kg. Wan Hu and his chair weighed at least 100 kg. The thrust-to-weight ratio was roughly 0.14:1. Orbital rockets require ratios above 1.2:1.

2. No thrust vectoring: Without gimballed nozzles or fins, any imbalance in the 47 thrust vectors would create uncontrolled rotation. Even a 5% variation in burn rate between tubes would flip the chair.

3. Simultaneous ignition impossible: 47 hand-lit fuses cannot be synchronized to the precision needed. The first rockets to fire would tilt the chair before the last ones ignited.

4. Structural failure: A wooden chair with iron brackets cannot withstand the vibration and thermal stress of 47 simultaneous rocket ignitions. The wood would split or burn through within the first second.

5. Chain detonation: 47 rocket tubes packed closely on a combustible structure guaranteed a chain explosion rather than controlled sequential burn. The closely packed tubes created a single large charge, not 47 independent rockets.

In 1970, the International Astronomical Union named a crater on the far side of the Moon 'Wan-Hoo' — honoring the ambition, if not the engineering. Every rocket that has reached space since has solved each of these five problems that Wan Hu could not.