Tuesday, February 15, 2011

Think About This: The Escape Velocity of Phobos

While I was doing a little background reading on the Mars post, I saw that a moon of Mars named Phobos has an escape velocity of approximately 25mph. It immediately dawned on me that that is achievable solely on human propulsion. Then I thought of the hilarity that would ensue.

In case you don't know, escape velocity is the minimum speed needed to escape a gravitational pull without further propulsion. The escape velocity of Earth is 11 km/s or ~7 miles/s. Can you imagine traveling 7 miles in one second? The sheer force of traveling that speed through air would probably crush any living thing and destroy any vehicle. 25 miles per hour though, that's a different story altogether.

25 mph is attainable by pedaling hard on a bike. On the surface of Phobos with next to no atmosphere (assuming you have an awesome space suit) you could get up there with less effort. If you hit a crater at that speed, you would launch right into space. At any lower speed though, and you may enter orbit around the moon.

Imagine floating around an object with a circumference of 70 miles. At 24 mph you would pass by the same spot you launched from every 3 hours or so. Now picture your friend is sitting there in a beach chair stargazing. Every three hours you come around yelling, "wwwwwwwweeeeeeeeeeeeeEEEEEEEEEEEEEEEEEEEeeeeeeeeeeeeeeeeee..." as you pass overhead.

Hopefully he is a good friend and gets a long stick to catch you when you come around again. But then again if you are ruining his stargazing you might be on your own.

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