I’ve been thinking about flag designs for colonies on Mars, and something occurred to me.
The “official” Flag of Mars has a critical flaw
The average wind speed on Mars is 10 m/s (20 mph); the fastest speeds recorded by the Viking lander were 30 m/s (60 mph), barely half the speed of hurricane winds on Earth. More importantly: Mars’ atmosphere is just 1% the density of Earth’s. These factors combined mean one couldn't fly a kite there.
A flag flying on Mars
According to what I’ve read, winds of about 5 m/s (11 mph) are needed (on Earth) to get a flag flapping. In Martian terms, that’s wind at 50 m/s (111 mph). (Dynamic pressure of the atmosphere needs to be multiplied by about ten for Mars’ wind to be comparable to Earth’s.) That’s certainly above the average-to-high range for wind on Mars. So no, Pascal Lee’s Martian tricolour couldn’t actually fly on Mars.
Changing the proportions
In flag terms, the wind velocity needed to overcome the drag coefficient increases as the length (fly) increases over the drag (hoist); in other words the longer a flag is, the stronger the wind must be to make it unfurl. Shorten the length/fly and you lower the required velocity. That suggests a flag shape with a much shorter length/fly than typically found on Earth. The actual math for calculating this is a bit above my ability, but it makes sense that if wind pressure on Mars is a tenth of Earth’s, a flag with a tenth the length/fly should flutter on Mars the way its full-length counterpart on Earth would. (Lighter, thinner material would obviously have an easier time too.)
Of course that means you could just have a tiny square for a flag, but that rather reduces its visibility at a distance, and would restrict how complicated the designs could be. So I propose the ideal proportions for flags flown on Mars would look more like nobori than your standard modern flag: 4+:1. Tall but narrow; probably no more than 25 cm (10 in) across, but no less than a metre tall, if I had to guess. (Ideally Martian flags would not need the cross-bar used in nobori, but flags made too large or of materials too heavy wouldn't have a choice.)
Bonus: What that means for the design of Martian flags
I suspect not much would change. Lee’s tricolour design, if rotated 90°, would definitely work. Horizontal stripes and divisions of the field would be as common as on Earth, but vertical divisions and stripes might be more easily obscured when at rest. Use of charges and emblems may similarly depreciate as the narrowed fly would require proportionately smaller designs. Cantons would likely occupy the full width at the top of the hoist, and chevrons might point down from the top. Bends and saltires would still work, and Nordic crosses could be rotated, but the vertical bar of any cross design could be a problem if it isn’t a significant width of the fly.
Do the numbers work out, and if so would the suggested change of proportion be the best solution (not requiring a cross-bar)? Bonus: am I overlooking any ramifications for flag design within these constraints?