When the Endeavor space shuttle was launched on March 2, 1995, astronaut Wendy B. Lawrence was performing the STS-67/ASTRO-2 mission aboard it.
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When the Endeavor space shuttle was launched on March 2, 1995, astronaut Wendy B. Lawrence was performing the STS-67/ASTRO-2 mission aboard it.
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What does it take to launch into space?
Besides money, hard work, and a lot of moving parts, the answer is science! This summer, NPR science podcast Short Wave will launch Space Camp, a series about all the weird and wonderful things in the universe. Let’s start with how to get to outer space.
Rockets and Isaac Newton
This is basically self-explanatory, but for a person to reach outer space, they would need to be in some kind of spacecraft attached to a rocket.
The rocket spews exhaust fumes as it leaves the launch pad. The exhaust gases are heading towards the launch pad. This is where Isaac Newton’s third law of motion comes into play. This law states that “every action produces an equal and opposite reaction.” So when the exhaust pushes downward, it creates an upward force that sends the rocket skyward.
Here, former MIT professor Walter Lewin completes a joint demonstration of Newton’s third law of motion as part of his valedictory lecture.
Newton’s Third Law – Best Demonstration Ever! ——Professor Walter Lewin
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A good example on a smaller scale is a common physics demonstration in which someone is sitting on something on wheels with a fire extinguisher. Like in this video, when the fire extinguisher ignites, people walk in the opposite direction.
The exhaust from rockets launched into space does the same thing.
The rocket has to go very fast because it needs to overcome the curvature of space-time itself. The structure of our universe, called spacetime, can be thought of as a bendable sheet. The Earth’s mass causes the flat structure of space-time to bend inward into a funnel shape. Moving up the funnel—and thus escaping Earth’s gravity—is more difficult than moving down.
This diagram explains gravity, also known as “gravity.” It is one of the four fundamental forces in the universe that bends space-time within the Earth’s mass.
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This diagram explains gravity, also known as “gravity.” It is one of the four fundamental forces in the universe that bends space-time within the Earth’s mass.
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Gravity and why floats fall
When these rockets lift off, astronauts feel intense gravity.
Gravity occurs when your body experiences acceleration. When you’re just sitting on the Earth or walking around the Earth, you probably don’t notice them – even though the Earth’s gravity is always present, which is 1 G.
You’re more likely to notice them when you do something like take a quick lift in the elevator. Then, you feel heavier.
But the heaviness of riding a fast elevator is nothing compared to what astronauts experience during launch. Retired Navy captain and former NASA astronaut Wendy Lawrence recalled the feeling of intense gravity in a recent interview with NPR.
“I remember the first time I flew I thought, ‘Oh my gosh, there’s someone sitting on my chest,'” she said. “I was trying to see if I could get my arms out in front of my face…and then, ‘Wow, I can’t get my arms up there against the tremendous force and acceleration of this amazing space vehicle.'”
Astronaut Wendy B. Lawrence, flight engineer and mission specialist for STS-67, writes notes in the margins of a checklist while monitoring an experiment on the middeck of the space shuttle Endeavor .
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Astronaut Wendy B. Lawrence, flight engineer and mission specialist for STS-67, writes notes in the margins of a checklist while monitoring an experiment on the middeck of the space shuttle Endeavor .
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Soon, that experience will change. Once the rocket separates from the spacecraft, the force pushing the astronaut into his seat is gone. They began to float beneath the harness.
They experienced what is commonly referred to as weightlessness.
But gravity doesn’t disappear. Even aboard the International Space Station, astronauts experience microgravity.
You can have a taste of this here on Earth. Some amusement park rides will suddenly rise, causing passengers to feel heavy, and then drop again. During the fall, the rider will feel weightless, even though they are actually falling. In physics, this is called free fall. Technically, all astronauts in the International Space Station fall very slowly, which is why they feel weightless.
Captain Lawrence said it was an amazing experience. “You just relax,” she recalled. “You are suspended in mid-air. You want to stop yourself in front of the window, float in front of the window and watch the world go by.”
To enter orbit is to fall and miss Earth
It turns out that orbital flights, like those of astronauts aboard the International Space Station, are going down. Specifically, it’s toward Earth.
Newton conducted a series of thought experiments to explain this idea.
scene one: Imagine you are standing on flat ground. Now imagine that you fire a cannonball horizontally from a position on the ground. In this case, the cannonball moves horizontally for a while and then starts falling along a curved path. This is projectile motion.
Scenario 2: You fire the same cannonball horizontally from the top of a very high mountain. In this case, the ball hits the ground farther because it falls farther and stays in the air longer. If you shoot the cannonball at a higher speed, it will move even further. The winding road is getting longer and longer.
Scene 3: By firing at a high enough velocity, you can drop the projectile in a curved path that follows the curvature of the Earth. Because of the matching curvature, the projectile always deflects away from the Earth. This is what it means to have an object in orbit. The shell fell but never reached the ground.
Shortwave Space Camp Preview Next Week: Pluto
Now, if we leave Earth’s orbit and reach the end of the solar system, we’ll pass by the once-beloved planet Pluto. Next week we ask: Why are there only 8 planets in our solar system? Pluto was downgraded to a dwarf planet many years ago. What does that mean? We also explain why Pluto’s geology would surprise scientists.
Are there other space stories you’d like us to cover? Send us an email: shortwave@npr.org.
Listen to shortwave Spotify, Apple Podcasts and Google Podcasts.
Listen to every episode of Short Wave without a sponsorship, and support our work at NPR by signing up for Short Wave+ plus.npr.org/shortwave.
This episode was produced by Berly McCoy, edited by Rebecca Ramirez, and fact-checked by Regina Barber, Emily Kwong, and Rebecca. Gilly Moon is an audio engineer.
