What is the ‘zero gravity’ that people experience in the vomit comet or space flight?
I’ve flown in zero-gravity planes many times. Every time, I enjoy the sensation of floating, being able to fly across the room with just a gentle push of the wall like astronauts on the International Space Station and rotating my body in any direction. It’s like the feeling you get on a roller coaster or when you jump off a diving board for a few seconds, but without the air blowing past your face.
It may seem contradictory to experience weightlessness while not in spaceflight. It is possible, and many people choose to share this as a form of recreation or research in an aircraft that is in the atmosphere.
As a researcher in aerospace engineering, I am interested in the control and use of liquids and gasses in spaceflight. For example, liquid rocket propellants are used in spacecraft, and water is used in the life support system of human spacecraft.
Gravity in action: Examples
Standing still, we can feel the Earth pulling us towards its center. The floor pulls your feet up, and gravity pulls you downward. You could push up from the bottom, float off, and never return to the ground again if gravity was gone. You’d appear to float like someone on a “Vomit-Comet” airplane flight or an astronaut aboard the International Space Station.
You may have heard that the orbit of the Earth’s space station is due to the fact the circular flight path balances out the gravity force. Centrifugal force is the force you feel when turning a car or train.
The International Space Station is closer to Earth, and therefore, gravity will be stronger. The force of gravity created by Earth is present at both the space station and the vomit comet. However, astronauts and tourists on the vomit comet appear to be devoid of gravity. Why?
The experience of flying in a vomit-comet flight with Purdue University and science experiments is like no other.
Gravity pulls my airplane to the runway every time. We know that gravity is present, but people seem to feel and look as if there is no gravity when they are flying with vomit comets.
The majority of these research flights consist of researchers with advanced degrees, such as mine.
Weightlessness in an aircraft
A simple everyday experience can help you to understand that gravity appears both to be present and absent. You feel pushed right when you are in a car that turns left. The door may go you back and even go against the right side of the interior. The velocity of the vehicle is also affected by turning the car in the opposite direction.
The speed and direction of the vehicle are both included in the term “velocity.” You feel sideways gravity when you change direction. You think forward gravity when you change the speed. When elevators start and stop, it feels like gravity is increasing or decreasing for a brief moment. Accelerations are the changes in velocity. Both acceleration and velocity are vectors. Force is another vector, as is gravity.
You’ve probably experienced how acceleration is the same feeling as gravity. Imagine you could create an “antigravity” acceleration, that is, an acceleration in the correct direction and at the right amount, in order to cancel gravity. Is this possible?
Yes, this is exactly what happens during a vomit comet flight or in an orbit.
The parabola is the shape of the flight path for vomit comets. The pilots do this by flying up at an angle of 45 degrees. They then level out and dive down at 45 degrees. This creates the necessary acceleration to cancel gravity. This acceleration lasts about 25 seconds, depending on the maximum speed of the plane and the rate at which it can be pulled up before and after the parabola.
By accelerating down just right in an aircraft or spacecraft, we can experience zero gravity. Weightlessness is the correct physical term, but “zero gravity,” which is also a descriptive term, describes the sensation. This is why experts in NASA and the aerospace industry use the word most often.
Flight trajectory of a typical zero gravity flight maneuver. C-9B flight trajectory, NASA reduced gravity research program
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