This post is part of Geek Takeover Week 2019. Top photo courtesy European Southern Observatory, the others from public domain on Wikipedia.
I fly a lot which gives me more than enough time to contemplate irrational scenarios of doom in the sky. Nervous fliers might not want to think about a space rock hitting your plane at 10,000 meters up, but just how likely is that scenario?
Plane crashes in general are very rare events that most people end up surviving if they’re in one. A lot has to go wrong for a plane to go down (on average 7 compounding factors) but a meteor strike could be a single, catastrophic disaster. Meteors pummel through our atmosphere anywhere from 11-72 kilometers per second (15,000-257,000km/hour) but what are the chances of being struck? Fortunately it turns out the chances of being struck are astronomically small and the chances of surviving an impact aren’t as hopeless as you may think.
Moving Targets
Let’s first start out with the basics – the average jumbo jet moves at 890kph (555mph). The fuselage of a 747-400 is 70 meters by 6m, the front wings 64m wide, and the tail wings 11m. All of these numbers mean the surface area of the wings is 543 square meters, the fuselage roughly 420m. A total of 963 square meters of area but since a meteor would only be coming from above, let’s cut down the total vulnerable surface area by half: 480m^2.
Meteor Size
Most meteors that are visible from the ground range in size from a grain of sand to a pebble. (They’re so bright because of the speed at which they enter the atmosphere, not their mass.) Most meteors smaller than a marble never reach the lower atmosphere where planes fly.
In 1996, David J. Helfand, chair of the department of astronomy at Columbia University and his colleague Charles Hailey determined the size of a meteor needed to significantly damage an airplane would need to be baseball-size or larger. Several thousand meteors this size or large hit the ground each year, mostly in the oceans and other unpopulated areas. At the time, a meteor impact was considered (but later ruled out) as the cause of the TWA flight 800 crash.
Cars Are Still More Dangerous
David Morrison of the NASA Ames Research Center, gives the best estimate of the possibilities of a plane being struck by a meteor entering Earth’s atmosphere:
“A typical car has an area on the order of 10 square meters, and there are roughly 100 million cars in the U.S., for a total cross-sectional area of about 1,000 square kilometers. The typical airliner has a cross-sectional area of several hundred square meters, but the number of planes is much smaller than the number of cars, perhaps a few thousand. The total cross-sectional area of airliners is therefore no more than 10 square kilometers, or a factor of at least 100 less than that of cars. Three cars are known to have been struck by meteorites in the U.S. during the past century, so it would appear that the odds are against any airplanes having been hit, but it is not impossible that one might have been.”
Morrison adds that it’s much more likely for a plane to be struck on the ground (since that’s where they are the majority of time). Any impact to a plane in flight Morrison notes, wouldn’t necessary result in an complete disaster. Assuming the meteor were relatively on the smaller size and did not hit the fuel tanks, a successful emergency landing isn’t impossible.
For you nervous fliers, it might help ease your nerves to know even a supersonic rock from space is something your aircraft and pilots could potentially handle. But the overwhelming odds are you should be more worried about having a middle seat or lost luggage than any space debris.
