How to Build a Flying Saucer

Inspired by a recent episode of “Physics of the Impossible” (Discovery - Science Channel) with Dr. Michio Kaku, I decided to explore the possibility of building a flying saucer. While modern UFO sightings consist of myriad objects ranging from triangles to orbs, I will focus on the classic flying saucer-shaped object portrayed in countless science-fiction films. Please understand that this is merely an attempt to create a theoretical framework for the construction of a flying saucer. I will assume that the aliens will have sufficient technology to engineer a craft capable of exploiting certain physical principles explained later.

Disclaimer - I will not count on any fringe science in my exploration. That is to say, such matters as anti-gravity and multiple dimensions will be ignored. These topics are wildly fascinating to consider; however, I will limit my discussion to matters that can be explained within our current understanding of physics. Another disclaimer – some of what you read here is original, however some has been inspired by the aforementioned documentary.

Based on common features found in sightings and in the movies, the flying saucer should be able to perform four maneuvers in relative silence and with no visible exhaust.

1) Take off vertically and hover

2) Accelerate/travel from over distances

3) Maintain lift (stay airborne at constant altitude)

4) Zigzag or abruptly change direction

Take off vertically and hover
Ion propulsion. It sounds like Star Trek, but it could actually work. It starts with an extremely large voltage source used to create a large current in a loop of wire attached to your flying saucer. At a sufficiently large voltage, stray current will ionize air molecules by knocking out an electron, leaving the molecule positively charged. A positively charged plate above the wire loop and a negatively charged plate below the loop force these molecules to move in a downward direction. According to Newton’s third law (for every action there is an equal and opposite reaction), the downward force on the ions is accompanied by an upward reaction force on the saucer. The result is upward acceleration. Want to descend? Simple. Just switch the polarity on the charged plates.

One catch, though - you must have air present for this to work. So we are limited to a planet with an atmosphere. Follow this link to a neat example of ion propulsion on a small scale:
http://www.youtube.com/watch?v=ulP1UB5PIN0&feature=PlayList&p=A18DD7F53E4F1D02&playnext_from=PL&playnext=1&index=3

Accelerate over distances
Since we want our UFO to be silent and free of exhaust, a traditional jet engine will not do the trick. Furthermore, we can potentially design our flying saucer to take advantage of Earth’s existing magnetic field. Loading up our craft with traditional (dipole) magnets won’t do the trick, however. The north pole on such a magnet would be attracted to the geographic north pole (magnetic south) and the south pole on the magnet would be attracted to the geographic south pole (magnetic north). This tug-of-war would result in zero net force. Perhaps a current hot topic in theoretical physics – magnetic monopoles – could help us out….

Unlike charges such as protons and electrons, a single magnetic pole has never been observed. Take a bar magnet, break it in half, and you end up with two bar magnets. While a magnetic monopole has never been observed, some theorists speculate they may exist in nature. If these monopoles could be harvested, they could be used to accelerate our flying saucer. Switch on the north monopoles, and the flying saucer accelerates along the magnetic field line towards the north pole. Switch on the south monopoles, and accelerate towards the Antarctic. Essentially, these invisible magnetic field lines could serve as a super-highway for our flying saucer.

Maintain lift to stay airborne
This is one where the sci-fi folks had it right. That’s because the technology needed to stay airborne is really nothing new. If you have ever thrown a Frisbee, then you can visualize the forces at work to keep our flying saucer in the air. The forward motion of a Frisbee forces air to move across its curved surface, generating a low pressure region above its surface, while maintaining a higher pressure underneath in accordance with Bernoulli’s principle. The net result is an upward force which allows the Frisbee to stay airborne while it is moving forward. Designing our flying saucer with a curved rim should generate the necessary lift.

Frisbees spin to maintain stability. Conservation of angular momentum tells us that the faster the Frisbee spins, the less prone it will be to wobbling and tumbling. So we can put a motor on the flying saucer that generates rotation in order to maintain stability during flight.

Zigzag/Change Direction
The monopoles used in our flying saucer allow it to travel along magnetic field lines. However, this only permits motion in the north or south direction. In order to fly east and west we need to employ some other means of acceleration. Dr. Michio Kaku suggests a rudder to accomplish this maneuver – much like a boat or airplane uses. I propose an alternative method which again takes advantage of Earth’s magnetic field.

The principle that we can exploit here is that a magnetic field exerts a force on a moving charge such as a proton or electron. Since electric current is comprised of electrons, a magnetic field exerts a force on anything that carries a current. In fact, the force is always perpendicular to both the magnetic field and direction of motion of the charge. See a demonstration of this phenomenon here (skip to the 1:00 mark): http://www.youtube.com/watch?v=_X8jKqZVwoI

If we could somehow incorporate a static charge over the surface of our flying saucer, then as the saucer moved vertically, the charge would be viewed as a moving charge (current) with respect to Earth. Assuming a positively charged craft moving upwards and a magnetic field pointing north, the force the craft would feel is directed to the west.

So the key is that our saucer has to move up or down in order to move east or west. Using this at the same time as the magnetic monopoles would allow the craft to travel in any ordinal direction such as northwest. Increasing the charge or upward/downward velocity would magnify this effect. Also, moving up and down varies the direction of the force, thus producing the zigzag effect.

So what?
So we’ve designed a flying saucer – at least in a theoretical sense. Could this be built today? Probably not considering we are needing to use magnetic monopoles. If alien flying saucers actually exist, it is probable that they use some form of technology that we are totally unfamiliar with. Still, it is an interesting exercise to explore the possibilities and limitations for a flying saucer using physical principles that we currently understand.