• Apollo 11 astronaut Buzz Aldrin walks on the surface of the moon. Image credit: NASA

Escaping Earth

One of the most amazing endeavors humans have ever undertaken is the exploration of space.  Millions of us dream of marveling at our blue and green marble of a planet from the depths of space. There are even those who will pay millions to do so.

More than 50 years ago, twelve astronauts walked on the Moon’s surface, about 386,000 kilometers from Earth. Since 2000, scientists have lived in a satellite popularly known as the International Space Station, performing various experiments.

Now the moon almost seems boring, and all eyes have instead turned to Mars, our nearest planet.  The distance from Earth to Mars varies depending on our orbits around the sun, but the minimum distance is about 54.6 million kilometers. With our current technology, it takes about six to eight months to send a spaceship to Mars. We can get to the moon in three days.

This week NASA landed a spaceship named InSight on the surface of Mars. Insight carried a robot that will dig around five meters into Mars’s surface. Scientist hope to learn about the evolutionary processes of rocky planets in our solar system.

Insight is not the first spaceship to successfully land on Mars. There were multiple Mars missions beginning in 1970s. The first successful mission was in 1976 with a spaceship named Viking 1. 

But missions to Mars are not always successful.  About half the attempts to land on Mars have failed. This InSight landing was NASA’s eighth successful landing on the red planet, and there are various future missions to Mars planned. Some missions plan to send people to Mars and there are even projects to explore establishing a permanent human settlement. 

The first step to travel to our moon or any other planet is the ability to escape from Earth’s gravitational pull. If we throw a stone or even fire a gun towards the sky, it falls back. That’s gravity. 

To travel beyond Earth, we first need to overcome that force. The minimum speed required to overcome it is called escape velocity. Here on Earth, our escape velocity is 11.2 kilometers per second. That’s 25,000 miles per hour. 33 times the speed of sound. Fast.

The escape velocity of the Mars is less than half of the escape velocity of Earth, about 5 km per second. Seems almost like a snail’s pace compared to Earth, right?

It doesn’t matter what your object is—it’s got to hit that speed if you want to go into space.

Achieving escape velocity is one of the biggest challenges facing space travel. It requires an enormous amount of fuel to produce the force to overcome the Earth’s gravitational pull. All that fuel adds significant weight to the spacecraft.  When an object becomes heavier, it takes more thrust to lift it. To create more thrust, you need more fuel.

The current solution to this problem is building a multi-stage rocket. When a rocket’s fuel is used up, the rocket gets rid of it so that it becomes lighter.  At each stage, the mass of the rocket is reduced until eventually it can reach the speed and attitude necessary to achieve escape velocity. 

Confused? You shouldn’t be. After all, this is only rocket science. And contrary to popular belief, rocket science is, in its principles, actually very simple. Don’t you believe me? Let me explain with an example. 

Have you noticed what happens if you blow up a balloon and let the air out of a balloon? The air goes out the nozzle of a balloon one way and the balloon moves in the opposite direction.  This is Newton’s Third Law of Motion. You should have learned about it in high school. Remember “For every action there is an equal and opposite reaction"? You’ve got the basics of rocket science. 

All rockets work in the same way. Exhaust gases come out of an engine nozzle at high speed and push the rocket forward. The burning process accelerates the mass of fuel so that it comes out of the rocket nozzle at high speed.

The basic principle of rocket engine is the same as that balloon. Now just scale it up: imagine yourself strapped to a pile of burning fuel traveling 37,000 feet per second. No problem, right?

Now I shouldn't discredit NASA engineers. Rocket science can get very complicated, very quickly. Here's just one example:

Do you remember the rocket used in Apollo moon missions in 1960s? NASA’s famous Saturn V rockets. The Saturn V rocket contained six million parts!  This is an extreme example, but every rocket used in space contains thousands of components and they all need to work perfectly in order to have a successful space mission.

Or just imagine that InSight entered Mars’s atmosphere travelling 12,300 miles per hour. It had six minutes and eighty miles to slow that speed down to zero. It did so successfully. Now that’s rocket science!

Note: You can follow the progress of NASA’s InSight mission on Twitter. It’s constantly sending us photos, video, and data. Check it out!


(Dr. Yadav Pandit is an experimental nuclear physicist currently working at Allen Community College as a physical science instructor. He writes a column of general interest in science for the Register.)

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