The MASSIVE difference between orbit and sub-orbit
Everyday Astronaut・21 minutes read
Being in space doesn't eliminate gravity, as weightlessness is experienced due to falling at the same rate as objects in low Earth orbit, providing valuable scientific research opportunities and the overview effect. Reaching space versus reaching orbit is determined by orbital velocity and the Karman line, with gravity still exerting a significant force even at 100 kilometers altitude.
Insights
- Weightlessness in space is not due to the absence of gravity but rather the spacecraft's acceleration, allowing astronauts to experience zero gravity.
- The distinction between reaching space and achieving orbit is based on the concept of orbital velocity and the Karman line, which marks the boundary between Earth's atmosphere and space at 100 kilometers altitude.
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Recent questions
What causes astronauts to experience weightlessness in space?
Acceleration of the spacecraft, not absence of gravity.
What is the Karman line and its significance?
Boundary between Earth's atmosphere and space, set at 100 kilometers.
How do objects achieve orbit around Earth?
Objects need to reach high speeds to raise their perigee.
What is the difference between apoapsis and periapsis in orbital mechanics?
High and low points in orbits around any body.
How do rockets reach orbital velocity?
Continual acceleration for about eight minutes.
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Summary
00:00
"Spaceflight: Weightlessness, Orbits, and Microgravity Explained"
- Being in space and experiencing weightlessness is a dream for many, but the sensation is short-lived as the spacecraft falls back to Earth.
- The difference between reaching space and reaching orbit lies in the concept of orbital velocity and the Karman line.
- Astronauts experience weightlessness due to the spacecraft's acceleration, not the absence of gravity.
- Zero G flights extend weightlessness through parabolic flights, where the plane follows a ballistic trajectory.
- Gravity decreases with distance from Earth, but even at 100 kilometers altitude, it still exerts a significant force.
- The term microgravity can be misleading as it refers to the sensation of weightlessness despite the presence of gravity.
- The Karman line, set at 100 kilometers, marks the boundary between Earth's atmosphere and space due to technical considerations.
- Orbiting at 400 kilometers altitude involves traveling at 28,000 kilometers per hour and completing a full orbit every 90 minutes.
- Changing velocity in orbit affects the shape of the orbit, with speeding up raising the orbit's apogee and slowing down lowering it.
- Raising altitude in a circular orbit requires speeding up to transition to an elliptical orbit, where the spacecraft's speed varies at different points in the orbit.
12:43
"Changing Orbits, Apogee, Perigee, and Weightlessness"
- To change orbits, speed up to match perigee with apogee for a higher altitude, or slow down to match perigee with apogee for a lower altitude.
- Different terms like apoapsis and periapsis are used for high and low points in orbits around any body, while apogee and perigee are specific to Earth's orbit.
- Opening a hatch at apogee on a suborbital ride requires depressurization and wearing spacesuits before tossing objects out.
- Objects tossed out at apogee will mostly fall back to Earth due to low speeds, creating an orbit-like trajectory around Earth's center.
- To achieve orbit, objects need to reach high speeds to raise their perigee above Earth's surface, requiring significant acceleration.
- Rockets need to continually accelerate for about eight minutes to reach orbital velocity, pitching over to gain horizontal velocity and raise perigee.
- Orbital decay occurs when objects in low Earth orbit slow down due to atmospheric drag, eventually leading to deorbiting.
- Being in space doesn't eliminate gravity, as objects in low Earth orbit experience nearly the same gravity as on Earth, resulting in weightlessness due to falling at the same rate.
- Suborbital rides offer scientific value by providing four minutes of weightlessness for experiments, allowing for significant research opportunities and the experience of the overview effect.
