alarm

signal

alert

attention

caution

danger

sci-fi

science

emergency

military

anxiety

anxious

apprehension

prison

jail

base

dismay

game

popup

unease

war

warning

worry

siren

intruder

aircraft

boat

catapult

security

mayday

energy

fiction

futuristic

nuclear

pilot

plane

scifi

shield

ship

shuttle

space

spaceship

ufo