The top picture, the M17A1 white
star, contained a parachute-mounted candle case on
its upper end, with a 5.5 second time-delay fuze
and 15 grain smokeless powder propelling charge in
the tube above the stabilizing fins. The signal
could rise above 600 feet before igniting,
producing a 20,000 candlepower signal for 20 to 30
seconds. This was also useful for battlefield
illumination.
The bottom picture, the M18A1
5-star signal, essentially produced 5 star signals,
but in free fall. The parachute kept the fall rate
to about 7 fps, so the flare would extinguish
several hundred feet above ground. The 5-star
signal lasted for 4 to 10 seconds, extinguishing
finally at about ground level.