Minecraft wiki entry for Minecart_booster, associated text: The C-Booster, also known as the collision booster, is a relatively small booster that produces max speed and momentum instantly, allowing fast uphill travel and instant speed. To make one, dig two trenches in the ground, both one block deep, two blocks wide, and 1 block in length. These trenches/lines must be parallel. Place minecart tracks inside them, then link them together in the area in the center by placing a line of track. Cover the trenches with any block, and place two minecarts per line of track. You should now have four closely compacted minecarts. If another minecart directly approaches it and bumps into a minecart inside the C-Booster, it will instantly accelerate in the opposite direction at max speed and max momentum.