# What Is the Mach Effect Gravity Assist or Mega Drive?

Leonard Kelley holds a bachelor's in physics with a minor in mathematics. He loves the academic world and strives to constantly explore it.

With all the focus on space exploration, any means of getting into space is being considered. Solar sails, nuclear propulsion, ion drives, and conventional chemical propulsion may all be methods you have heard before. But what about the Mach Effect Gravity Assist Drive, or MEGA Drive? You may hear it mentioned more and more, because it offers a fascinating method of fuelless (in a conational sense) propulsion. That is huge, but how does such a method work?

## The Set-Up

The basic concept is changing the mass of an internal object and using the gravity changes in order to generate thrust. By making “tiny, ultra-quick variations in an object’s mass” it can cause a positional change that, when correlated to another object, can induce a thrust overall. Traditionally, thrust is achieved via a chemical reaction. When a rocket fires, gas exists the craft and through the Conservation of Momentum the gas exiting pushes against the craft and thus generates the force needed to move upward. But in order to move that mass we are using mass, and so the larger our rocket the more fuel we need to lift it and that fuel means we need more fuel, and…you see the line of progression. Efficiency is a big issue here, hence why space ports as a refueling station are so appealing. But that still can’t avoid the huge costs associated with space travel. Alternatives to conventional chemical propulsion, like an ion drive, are more cost effective but are limited in their applications, requiring smaller craft to be truly efficient (Scoles 60-1).

The original work comes from Heidi Fearn and James F. Woodward (California State University). They looked at piezoelectric disks, which change in width depending on the voltage running through it. On one side of the disk is a reaction mass while the other side has the fluctuating mass. When a voltage is applied and the disk width increases, the fluctuating mass experiences a force that decreases its mass, causing a dip in inertia and thus makes it easier to push. Then when the voltage is released, the width of the disk decreases, the fluctuating mass returns to normal and so the reaction mass moves along with the center of gravity of the system as the whole system moves forward. This process can be repeated as needed, each time generating a net thrust courtesy of inertia (Scoles 61-2, Singh).

It is because of this inertia feature that the drive is named after Mach, a pioneer in that field. In the 1880s, he tried to develop a theory for inertia, because it’s inherently an odd phenomena. An object continues to move in the direction a net force was acting on, but what about forces that are not local? They still impact you, and so Mach developed his Principle in which inertia is the “result of all the gravity influences of all the matter in the Universe.” Mass impacts inertia, and so via this observation the MEGA drive was developed to exploit this feature as thrust. By changing our object’s relationship with all the matter in the Universe, I am creating an energy differential that becomes thrust! It’s wild and seemingly violates the Conservation of Momentum, and yet many are on board with this interpretation, especially considering the results. Woodward feels no violation is happening because the reaction mass would be the entire Universe, meaning its inertia would change. Yeah, it is a crazy though (Scoles 62, Singh).

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But while the drive is testing this MEGA effect, it wasn’t the only result the team was trying to investigate. They wanted to see if such a drive was also Lorentz invariant, or that for a given small section of space-time the special theory of relativity should hold. That is indeed crucial because that discusses gravity, and so if this small scale test could work then larger scales would be applicable too. If not, then possible new theories could emerge to explain the behavior seen (Singh).

## The Initial Results

Woodward and Fearn have sent their design to 4 different labs which have tested the drive and confirm that there is something happening here. NASA has even contributed 2 grants to further study the drive. Results show that the mass is changing in conjunction with the piezoelectric activity, and so the thrust generated, while small, is present. Very, very promising (Scoles 60, 63; Singh).

## Works Cited

Scoles, Sarah. “The Good Kind of Crazy.” Scientific American Aug. 2019. Print. 60-3.

Singh, Amrik B. et al. “Mach Effect.” Ee.ic.ac.uk. Imperial College Electrical and Electronic Engineering Second Year Group Project. Web. 05 Mar. 2020.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.