Since it is not natural for human being to fly, flying in an airplane can produce special sensations to your body. One of those sensations is zero gravity flight where it is possible to simulate gravity-free environment.
The possibility of zero gravity simulation was proposed for the first time in a science paper written by German aerospace engineer Fritz Haber and German physicist Heinz Haber in 1950. Zero gravity flight can be achieved by performing series of calculated aircraft maneuvers. Due to it being much cheaper and a safer way to simulate zero gravity than sending people to space, zero gravity flights are used for several different reasons such as:
- Simulating space environment conditions for astronauts training
- Performing space-related science researchers
- Making movies which are related to space travel
How it is possible to generate zero gravity in flight.
Basically, zero gravity can be generated by performing series of climb and descent maneuvers in such way that aircraft trajectory is actually parabolic. During these parabolic flights, it is necessary to neutralize all forces which act on a human or object in the airplane.
There are four main forces that act on an airplane during flight:
- Aerodynamic lift force (Cl)
- Drag force (Cd)
- Thrust (Tn)
- Gravity (G)
In order to define basic forces acting on an airplane, it is necessary to make some assumptions.
The first assumption is that aircraft is in horizontal (h= const) and stationary flight (v= const) with no turns. The second assumption is that angle of attack is small (α≈0). The third assumption is that aircraft pitch angle is 0. The final assumption is that aircraft mass change during the small amount of time is close to zero.
Forces acting on aircraft during stationary horizontal flight without turns
If an aircraft performs maneuvers in such a way that there is an acceleration in any form, by first Newton law this system is considered as an inertial system because there are inertial forces as a consequence of acceleration. The gravity influence can be removed by generating such flight path that centrifugal force (which is an inertial force) directly opposes gravity. If those two forces are equal the sum of all forces acting on a body equals to zero which leads to zero gravity sensation.
Zero gravity flight maneuver
The zero-gravity maneuver is performed by sudden aircraft acceleration in horizontal flight, then rotating the nose to approximately 45º pitch angle, then reducing thrust and slowly rotating nose down from 45º up to approximately 30º down and returning to horizontal flight. During aircraft acceleration and rotation up, g-forces are from 1.8g to 2.2g and during rotation from 45º up to 30º down the gravity equals to z down the gravity equals to zero. The time frame where zero gravity occurs is about 25 seconds.
Zero gravity maneuver
Zero gravity flights often last for about hour and a half which is enough to perform about 15 zero gravity maneuvers which leads to some 6-7 minutes of zero gravity experience. Beside zero gravity flights, it is possible to simulate different values of weight reduction. It is possible to simulate 1/6 of weight (Moon gravity) and 1/3 of weight (Mars Gravity). The different values of weight reduction are obtained by changing flight maneuver parameters such as climb and descent angles and acceleration value.
The effects of zero gravity on human body
The zero gravity has a lot of negative effects on a human body. During the research process, scientists have concluded that zero gravity weakens bones and muscles, it leads to cardiovascular issues since gravity helps fluids in body to flow and it can lead to eye and ear problems. Also, the scientists have noted that people can experience disruption in the proprioceptive system, which tells where arms, legs and other parts of the body are oriented relative to each other. It is also possible to have stomach issues which can lead to vomiting. Since weightless sensation in zero gravity flights lasts for a short amount of time, these symptoms are rare but it is advised to perform a medical examination before attaining the zero-gravity flight.
The safety of zero gravity flight
Zero gravity flights were initially performed by NASA, Russian Space Program and European Space Agency in the early 60s.
Today private companies operate flights and offer a zero-gravity experience. In North America a specially configured 727 that has been certified by the FAA. The aircraft is operated by experienced pilots who are trained for zero gravity flights. The actual stress placed on the airframe is well within aircraft limits and all maneuvers are conducted at a safe altitude.