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Ariane 5 Rocket Explodes 37 Seconds After Launch Due to Integer Overflow

ESA
Ariane 5 Rocket Explodes 37 Seconds After Launch Due to Integer Overflow
Ariane 5 rocket lifting off from the Kourou launch pad, the vehicle that exploded 37 seconds into its first flight.Image: ESA/CNES/Arianespace — Public domain via NASA/Wikimedia Commons · Public domain

What happened

The maiden flight of the Ariane 5 rocket ended in self-destruction 37 seconds after launch. A 64-bit floating-point value representing horizontal velocity was converted to a 16-bit integer, overflowing and crashing the inertial reference system. The backup system had the same bug and failed identically.[1]

Ariane 5 Flight 501 exploding 37 seconds after launch in 1996 — a 64-bit float to 16-bit integer overflow caused the $500 million failure.Image: Bad.Technology archive
Ariane 5 rocket exploding shortly after launch over the jungle
Image: Bad.Technology archive

What went wrong

Software from the Ariane 4 was reused in Ariane 5 without verifying that the same assumptions held. The horizontal velocity in Ariane 5's higher-energy trajectory exceeded the range the conversion could handle — a scenario that was never tested because Ariane 4 never reached those velocities.[1]

Lesson learned

Software reuse across systems with different operational envelopes is high-risk. Exception handling must be required in safety-critical code — the system crashed because an unhandled exception propagated to the flight computer. Assumptions embedded in code must be documented and re-validated.

Est. value burned ~$500M rocket + Cluster satellite payload
rocketoverflowadasoftware-reuseembeddedFrance

Sources

  1. [1]
    ESA Wikipedia
    Ariane 5 Rocket Explodes 37 Seconds After Launch Due to Integer Overflow Wayback Machine snapshot

External links can go dark — pages move, paywalls appear, domains expire. Every source above includes a Wayback Machine snapshot link as a fallback. All citations are best-effort research; if a source contradicts our summary, the primary source takes precedence.

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