Hedgehog
The hedgehog design has operated continuously without major revision for approximately 15 million years. Birth rates, survival rates, and population dynamics remain stable across most of its European range. Individual hedgehogs demonstrate predictable behaviour patterns, consistent dietary preferences, and reliable seasonal rhythms. The system fails primarily due to external factors: habitat destruction, pesticide accumulation, and road traffic. Internal system failures are extraordinarily rare, with the hedgehog's biological machinery achieving near-perfect operational consistency.
Rocket
Despite seven decades of development, rockets maintain a non-trivial failure rate. The Space Shuttle programme lost 2 of 135 missions, a 1.5% catastrophic failure rate that would be unacceptable in commercial aviation. Modern vehicles have improved significantly, with SpaceX achieving 98.6% mission success, yet each launch remains a calculated risk. Components number in the millions, propellant chemistry borders on instability, and environmental tolerances are measured in fractions of degrees. The rocket is reliable enough for expendable cargo but remains too unpredictable for routine human transport.