急於星火

急 = 刍 + 心 : Joan of Arc just arrived at the space station and although she has to go to the bathroom very urgently, she first has to clear the way of a big fluffy heart using a lawn mower.

于 = 亅 + 二 : Mnemonic symbol: prepositions (in, at, on, to, ...) are what glue the sentence together. Honey is as sticky as glue, so I'll represent 于 by a honey jar.

Yu the Great (于) was assigned to repair the electronics of the space station's kitchen (Ø2), but instead he was snacking honey from a honey jar (于). Unfortunately his capacitor (二) got stuck in the honey and now he has to use a crowbar (亅) to lever it out.

星 = 日 + 生 : The sun (日) and a satellite (星) had a love affair and now have a baby: Xi Shi (xi) is quietly sleeping in her little cradle (生) in front of the engine ((e)ng1).

火 = 人 + 丶 : Helga Horse (hu) and Neanderthal Man (人) are starting a fire (火) in the observatory's living room (o3) with two large petals (丶).