Week 3 - Re-Entry

Week 3: Reentry to Earth

By Miranda Lott

Multiple Select

You're in Space. What can you see? Check all that apply.

• Earth's curved horizon

• City lights glowing at night

• Volcanoes, storms, and auroras

• The Milky Way Galaxy with NO atmosphere blocking the view

What is Orbit?
Why do you stay in space?

Open Ended

What is Newton's First Law of Motion?

An object in motion stays in motion unless acted upon by an outside force.

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Newton's First Law (Inertia)

• ​Before launch, you are at rest 🚀 → It takes a force (the rocket engines) to launch you into space.

• Once you reach space, there’s almost nothing to slow you down.

• Without air resistance or friction, your spacecraft would keep moving forever unless something stops it.

Why don't you fall back to Earth?

Open Ended

What is Newton's Second Law?

🌎 Newton’s Second Law (Force & Acceleration)

“Force = mass × acceleration (F = ma)”

• Earth’s gravity constantly pulls on the spacecraft, trying to pull it down.

• However, the rocket has so much forward speed (inertia) that instead of falling down, it keeps falling around the Earth!

• Think of throwing a baseball: If you throw it far enough, instead of landing, it will keep circling the Earth—that’s an orbit!

How do astronauts get to orbit?

Open Ended

What is Newton's Third Law?

Multiple Choice

What is Newton's 3rd Law?

• F=ma

• Inertai

• For every action, there is an equal and opposite reaction.

• What goes up, must come down.

For every action, there is an equal and opposite reaction.

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​Newton's Third Law (Action & Reaction)

​How do astronauts get to orbit? The rocket engines push burning fuel downward ⬇️ In response, the rocket moves upward ⬆️ In space, firing thrusters pushes gas in one direction → the spacecraft moves the opposite way.

Why don't astronauts "fall" back to Earth?

​Earth’s gravity constantly pulls on the spacecraft.

• But the rocket is moving so fast (17,500 mph / 28,000 km/h) that it keeps missing Earth!

• Imagine throwing a baseball: If you throw it hard enough, instead of falling down, it will keep going around Earth—this is an orbit!

• The ISS and spacecraft stay in orbit because of a balance between gravity and speed (inertia).

💡 Astronauts float because they are in “free fall.”


They are falling toward Earth, but since they’re moving sideways so fast, they never actually hit the ground!

🏠 Living on the International Space Station (ISS)

• The ISS orbits 250 miles (400 km) above Earth and completes an orbit every 90 minutes.

• Astronauts see 16 sunrises & sunsets every day! ☀️🌙

• No gravity means no up or down—everything floats!

• Food is packaged so it doesn’t fly away.

• Exercise 2 hours a day to prevent muscle and bone loss.

• Sleeping? You zip yourself into a sleeping bag strapped to the wall!

Why is Returning to Earth so Dangerous?

• When a spacecraft returns, it must slow down from 17,500 mph to safely land.

• Slowing down creates friction with the atmosphere → friction causes extreme heat (3,000°F / 1,650°C)!

• A heat shield protects the spacecraft from burning up.

🌎 Falling Through the Layers of the Atmosphere

Multiple Choice

What is the outermost layer of the atmosphere?

• Exosphere

• Thermosphere

• Mesosphere

• Stratosphere

• The spacecraft starts slowing down slightly.

• There’s almost no air to help slow the capsule.

Exosphere

Multiple Choice

After leaving the Exosphere, which layer of the atmosphere will the spacecraft enter, on its' way back to Earth?

• Mesosphere

• Stratosphere

• Troposphere

• Thermosphere

• Extreme heat! The spacecraft glows as it compresses air in front of it.

• This is where the auroras and the ISS are located.

​

Thermosphere

Multiple Choice

Which layer comes after the Thermosphere? (When heading FROM space Toward Earth)

• Mesosphere

• Stratosphere

• Troposhpere

• Exosphere

• The spacecraft rapidly slows down.

• Meteor protection! This layer burns up most meteors before they hit Earth.

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Mesosphere

Multiple Choice

Which layer comes after the Mesosphere?

• Troposphere

• Stratosphere

• Thermosphere

• Lottosphere

• The capsule continues slowing.

• Parachutes begin deploying here.

• This layer holds the ozone layer that protects Earth from UV rays.

​

Stratosphere

Multiple Choice

The atmospheric layer closest to Earth!

• Mesosphere

• Exosphere

• Colesosphere

• Troposphere

• Parachutes fully open, slowing the capsule.

• The spacecraft lands in water or on land.

​

Troposphere

Multiple Choice

What force keeps a spacecraft from flying off into deep space?

• Air resistance

• Gravity

• Magnetic Fields

• Solar Wind

Multiple Choice

What is the minimum speed needed to stay in orbit around Earth?

• 1,000 mph

• 5,000 mph

• 17,500 mph

• 50,000 mph

Multiple Choice

Why do astronauts feel weightless in space?

• There is no gravity in space

• The spaceship moves so fast that gravity has no effect

• They are in free fall, constantly falling around Earth

• Their spacesuits make them float

Explanation:

Why is "There is no gravity in space" incorrect?

Gravity exists everywhere in space, including where astronauts orbit the Earth. The force of gravity from Earth extends far beyond the atmosphere—it weakens with distance, but never completely disappears.

In fact, the International Space Station (ISS) orbits Earth at about 250 miles (400 km) above the surface, where Earth's gravity is still about 90% as strong as it is on the ground. So gravity is definitely still present in space.


Why is "They are in free fall" the correct answer?

Astronauts feel weightless because they are in free fall—meaning they are constantly falling toward Earth but moving forward so fast (about 17,500 mph / 28,000 km/h) that they never actually hit the ground.

Think of it like this:
🚀 If you jumped off a high cliff, you would fall straight down.
🌍 But a spacecraft moves so fast horizontally that as it falls, Earth curves away beneath it—so it keeps falling without ever hitting the surface.

This creates the feeling of weightlessness because everything inside the spacecraft (including the astronauts) is falling at the same rate.

Multiple Choice

What happens if a spacecraft moves too slow in orbit?

• It stays in orbit forever

• It escapes Earth's gravity

• It falls back to Earth

• It speeds up on its own

Multiple Choice

According to Newton’s Third Law, how does a rocket move in space?

• By pushing exhaust gas backward, making the rocket go forward

• By pushing against air

• Using Earth's magnetic fields

• By spinning really fast

Multiple Choice

Which layer of the atmosphere does a spacecraft enter first when returning to Earth?

• Lottosphere

• Stratosphere

• Mesosphere

• Thermosphere

Multiple Choice

What is the purpose of the heat shield on a reentering spacecraft?

• To speed up the spacecraft

• To slow down the spacecraft

• To protect against high temperatures and friction

• To increase gravity