# TRL3 - Proof of Concept TRL 3 Showing that you can use X for Y. A ‘toy’ system is at TRL3 - a system whose entire purpose is to show that X can be used for Y . *What does a classic progression to TRL3 look like?* * We notice that kerosine tends to explode (TRL1) * Posit that kerosine could be used to launch rockets (TR2) * The proof of concept could be using kerosine to lift something into the air (TR3) If the attempt to create a proof of concept doesn’t work, you might need to go back to [[TRL2 - Possible application formulated]] and form a new application hypotheses. Or even [[TRL1 - Basic Principles Observed and Reported]] with the knowledge that you now need to know something crucial that you didn’t know before. This is why [[TRLs are not monotonic]] <!-- #evergreen --> [Web URL for this note](http://notes.benjaminreinhardt.com/TRL3+-+Proof+of+Concept) [Comment on this note](http://via.hypothes.is/http://notes.benjaminreinhardt.com/TRL3+-+Proof+of+Concept)