Orbital Mechanics – Rational Thinking 101

How Do We Get to Mars?

This is the kind of question, “How do we get to Mars?” that normally would take a lot of discussion and involve a whole lot of mathematics.

I’m going to try to explain it simply and to the best of my limited ability.

Mars is in orbit around the sun. Earth is in orbit around the sun. Earth, being closer to the sun, orbits faster. Mars orbits more slowly. So you have to wait until the two planets are lined up to launch, which happens about every 2 years or so. But it’s not a straight shot out to Mars. Everything works following the rules of orbital mechanics.

Essentially, we launch a spacecraft from Earth into a highly elliptical orbit around Earth. This orbit is so elliptical, that it extends all the way out to the orbit of Mars. You time it so just as this spacecraft reaches it’s farthest point from Earth before beginning it’s return journey, Mars comes along in it’s orbit. The spacecraft meets up with Mars.

Transferring of orbit. A Martian bound spacecraft launches from Earth in an Elliptical orbit, catching up to Mars at the moment when Mars goes by in it’s own orbit around the sun.

The image above from the Jet Propulsion Laboratory website of NASA illustrates how this transfer of an elliptical orbit from Earth catches up to Mars. This process takes about 9 months for a spacecraft like this to reach Mars, and can be accomplished only about once every 2 years.

Why is the Moon not being pulled into the Earth from gravitational forces? Is the Moons mass stopping gravity from pulling it any further?

The Moon is being pulled toward the Earth, but it’s forward momentum causes it to miss Earth each time it goes around by a wide margin. This is called an orbit.

However, let it be known that because the oceans slosh around on Earth as it rotates about it’s axis (these are called ocean tides), the speed of Earth’s rotation is gradually slowing down. Billions of years ago a day on Earth was only about 8 hours, and now it continues to slow down. We compensate this twice a year by adding leap-seconds as needed.

This slowing of the earth’s rotation causes the moon to drift further away from us every year by about 1.5 inches, so eventually the Moon will escape Earth altogether and drift away.

It will never crash into Earth.

Build a Vehicle that could park in your garage but fly into orbit?

This would be so cool. Everyone would want one, even if they couldn’t afford it. But is the concept possible?

Well, the short answer is no. It’s not possible.

To understand that “no” requires a little bit of understanding in orbitology.

You see height is not the only problem when you want to stay up in space. If you want to stay up there for sometime you’ll need to be in orbit. To get in orbit you’ve got to go really, really fast – like around 17,000 mph fast.

That’s because an orbit simply put is when an object is going so fast in one direction that as it falls it misses the planet. You’ve got to be going a lot faster than a speeding bullet.

So if you had a vehicle in your garage that could not only fly like a plane, but could continue to fly above the atmosphere and get going 17,000 mph, then you\d be bad ass.

But you can’t and you won’t, because to do all that takes a lot of fuel. That’s why we have these big ol’ rockets boosting satellites and astronauts into space. Those big ol’ rockets are filled with fuel. Once the fuel is expended then the big ol’ rocket isn’t needed anymore and it’s detached to fall back to Earth.

So sadly, the idea of having a small shuttle that you park in your garage and fly into space is just not going to happen. Ever. Sorry!

Why does the moon revolve around the earth?

It just moves forward. The moon isn’t stationary. It has inertia and no atmosphere in space to slow it down. It just goes. As it moves forward, the gravity of Earth tugs on it and it falls, but because it’s moving forward it misses Earth as it falls and goes around, again and again. That’s called an orbit.

Simply said.