36 Estes D-12 Class engines strapped to a Christmas Tree. We used Google to look up the data sheet for an Estes D12 model rocket engine. We took the average thrust of one engine (10 Newtons) and multiplied it by 36 (number of engines we had) to calculate the total thrust available. We then subtracted from that the force due to gravity acting on the tree to figure out how much force was available to lift the tree. The estimated acceleration of the tree was then calculated using Newtons second Law (F=ma). To estimate the height, the calculated acceleration was applied to the kinematic equation with the engine burn time of 1.5 seconds as taken from the online data. Without including the air resistance of the tree, or the large spike in thrust (up to 30 Newtons in the first .25 seconds). We conservatively predicted a height of around 95 feet. (Looks like we exceed that.) The most important calculations were those done to assure that the tree flew straight and did spin wildly out of control under power. In order to assure this, the center of mass must be towards the front and more importantly in front of the center of pressure caused by the drag of the tree. We were able to achieve both of these things by attaching a large wooden star at the end of an old pool cue to the front of the tree.
