To reset the pin back to LOW to ready the next launch send:
We also controlled the rocket launch by creating an aREST Dashboard. Instructions on how to do this are here: https://arest.io/esp8266-arest-pro.
An iPhone app using Thunkable.com also worked but it's just a simple button that tells Pin 5 to go HIGH. More to follow on that.
Simple Thunkable App used to Launch Rocket from an iPhone.