Space Flight, Gravity, and Forces - 8B

What is Microgravity?

Microgravity University, also known as the Reduced Gravity Student Flight Opportunities Program (RGSFOP) is a program run by NASA which enables undergraduate university students to perform microgravity experiments aboard NASA's DC-9 aircraft at Johnson Space Center in Houston, Texas.

The Vomit Comet is an aeroplane

that briefly achieves zero G, allowing

people and prospective astronauts to

experience weightlessness.

When you think about how astronauts train for weightless environments you often think that space agencies like NASA or the Russian space agency have anti-gravity machines. The reality is that there is no special chamber they have on site that they turn on. Instead they have a series of different methods they use to help astronauts get a feel for weightlessness. One is a type of mine shaft elevator. Another way is to have astronauts train underwater. The most famous is the “vomit comet.”

In general, 65 seconds of flight will achieve 25 seconds of weightlessness.

Weightlessness produces nausea and sickness (vomit) in two out of three people and thus the aeroplane earns its nickname.

Human Effects of Weightlessness

Weightlessness is the condition that exists for an object or person when they experience little or no acceleration except the acceleration that defines their inertial trajectory.

The definition and use of 'Weightlessness' is difficult. So to break it down weight means the force exerted by gravity, weightless means the absence of such forces and weightlessness formally means the condition of zero gravitational force.

As an example, an accelerated free fall trajectory results in the weightlessness of objects in a falling elevator. The same type of accelerated free fall trajectory causes weightlessness of objects in orbit about the Earth.

People often equate zero gravity with being weightless, and this is not technically correct. An environment that is truly "zero gravity" does not have any gravitational force, and gravity is present in some form or another throughout the universe. What astronauts experience in space is a weightless environment, where Earth's gravitational force is gone.

Another negative consequence of weightlessness is the effect zero-gravity has on the cardiovascular system. On Earth, the heart must operate against gravitational pressure to sustain blood flow. Under zero-gravity conditions, that force is absent, causing the heart to lessen its pace according to the decreased demands.

Those who could truly travel to the center of the Earth (and survive) would experience natural weightlessness. This is because at this point, gravity would be directed away from them in directions, leading to a net gravitational force of zero.

What are g-Forces?

G-Force (g from gravitational) associated with an object is its acceleration relative to free-fall. G-force refers to either the force of gravity on a particular celestial body of a force of acceleration anywhere.

Weight is a measure of the gravitational force on an object. Weight usually refers to Earth's gravitational force on an object but weight can also be a measure of the gravitational force exerted on objects by the moon or other planets.

The moon has less mass than Earth does. Therefore, the moon's gravitational force is less than Earth's. The astronauts bounced around on the moon because they were being pulled down with as much force as they would have been on Earth.

Earth's gravitational force is very large so you must apply forces to overcome Earth's gravitational force any time you lift objects or parts of your body. Earth's gravitational force pulls everything toward the center of the Earth.

Venus and Earth have about the same mass. But because Venus is closer to the sun, the gravitational force between Venus and the sun is greater than the gravitational force between Earth and the sun.

Projectile Motion

A projectile is an object upon which the only force acting is gravity.

Projectile motion has two component- Horizontal motion and vertical motion.

Projectile motion is the curved path that an object follows when thrown, launched or otherwise projected near the Surface of Earth.

Simulated Gravity

Artificial gravity can be achieved by installing mass into a spacecraft so the spacecraft generates its own gravitational field, thus pulling everything inside towards the field.

• You can simulate gravity by using centripetal force.

Artificial gravity is the varying of apparent gravity through artificial means.

This artificial gravity can be produced by the use of centrifugal force.

http://www.brightstorm.com/science/physics/circular-motion-and-rotational-mechanics/simulated-gravity/

Centrifugal force is a lack-of-centripetal force.

To create "artificial gravity" ,you can spin your spacecraft or space station.

An orbit is a regular, repeating path that an object in space takes around another one.

What is an Orbit?

• Terminal Velocity is the constant speed that a freely falling object eventually reaches when the resistance of the medium through which it is falling prevents further acceleration.

• A free-falling achieves its terminal velocity when the downward force of gravity (Fg) equals the upward force of drag (Fd). This causes the net force on the object to be zero, resulting in an acceleration of zero.

• As the object acceleration (usually downwards due to gravity), the drag force acting on the object increases, causing the acceleration to decrease.

• The downward force of gravity (Fg) equals the

upward force of drag (Fd). The net force on the body

is then zero, and the result is that the velocity of the

object remains constant.

Thank you! :D

Terminal Velocity

This is an example of someone shooting an arrow that creates projectile motion because when you shoot it, the gravity pulls the arrow down to the Earth.

with an object is its acceleration relative to free-fall

NASA's Vomit Comet