Who is to say whether a scientific or technical discovery is accidental or planned? Historians of science often point out that there was some luck involved in Fleming's "accidental" discovery of penicillin. But Fleming and his assistants were already actively searching for anti-bacterial agents, and the discovery of penicillin followed a similar path to his earlier discovery of the anti-bacterial properties of egg-white (lysozyme), so it is misleading to describe the discovery of penicillin as a complete accident.
Some historians of science now suggest that the Chinese invention of rockets was an accident. They argue that Daoist thinkers would have understood explosion as a violent response to the combination of Yin and Yang, and that they would therefore have been unable to think systematically about a reaction involving three ingredients instead of two. In other words, a given mental model or frame constrains investigation. (Unlike the Fleming example.)
Of course we must be cautious about interpreting historical Daoist thought against either a modern understanding of the chemistry of gunpowder, or even against a modern interpretation of Daoist thought. Perhaps the ancient Chinese did not see any contradiction between a three-way chemical reaction and Daoism, and that this apparent contradiction is merely a modern projection. (In other words, the modern historians perceive the past using their own mental models or frames. None of us can escape this.)
However, it is still true that mental models can constrain what we perceive, as well as how we make sense of our perceptions and act upon them, and this has important implications for innovation and organizational intelligence.
Frank H. Winter, Michael J. Neufeld, Kerrie Dougherty, Was the rocket invented or accidentally discovered? Some new observations on its origins (Acta Astronautica, Volume 77, August–September 2012, Pages 131–137) http://dx.doi.org/10.1016/j.actaastro.2012.03.014
Corrinne Burns, Oops, I invented the rocket! The explosive history of serendipity (Guardian, 4 May 2012)