The image in the Canon is of a solid wooden door: a ball of string thrown at the door won't leave a dent at all.

圣典里的比喻形象是一扇硬木门：朝那扇门扔过去一个线团，根本不会留下一点凹痕。

youdao

They literally shoot up like a canon ball, get you out of the atmosphere into space and falling back to land within a couple of minutes of your launch.

CNN: Next challenge for space industry