Chapter 4 - Review of Gravity Control Within Newtonian and General Relativistic Physics
Notes by David A Roffman on Chapter 4 of
FRONTIERS IN PROPULSION SCIENCE
Chapter by Eric W. Davis, Institute for Advanced Studies at Austin, Austin Texas
This chapter deals with antigravity, formally known as gravity control. It is well known that gravity is the weakest of the four fundamental forces. Unlike the electromagnetic force, which we can control, unclassified literature indicates that we cannot yet control gravity. Gravity control is acceptable under the quantum gravity, cosmological vacuum energy, and quantum field theories. Possibilities for manipulation include high intensity magnetic and electric fields.
NEGATATING GRAVITY THE HARD WAY
A known way to cancel gravity is an impractical one. All we have to do is find another planet the size of Earth, and drag it near Earth. Another approach is to pull a dwarf star or neutron matter close Earth. Both approaches rely on a canceling effect by equal gravity from each object. A more realistic method is to create an ultra dense disk (as suggested by Robert Forward), and use that to negate gravity over an area. However, we do not yet have technology to do this.
APPROACHES FOR ORBITAL STABILITY
The Six-Mass Compensator (from Forward) is a practical way to cancel tidal forces (minor forces that are almost ignorable) in orbit. This uses six 100kg tungsten or lead, 20 cm spheres evenly spaced to work. The gravitational attraction of the spheres will negate the small tidal forces almost completely. Due to its weakness though, it is ruled out as useful for propulsion. Tidal forces are due to unequal gravitational forces being applied from one side of a body to the other (or throughout the body). The Tidal force is equal to 2*G*M*m*dr/r3, where dr is the distance across the object (it could be R, the radius of the object) and r is the center to center distance of the two masses.
NEWTONIAN LEVITATION ENERGY ESTIMATE
The energy required for levitation of 1kg is 62.5 MJ (2.05 times the energy required for low Earth orbit (LEO) of the same mass). To circumvent annoyances like this, the negative mass approach is mentioned. Negative mass repels other negative mass, baryonic matter (normal matter), and mostly anything else. By creating a system where near equal amounts of matter and negative matter are used, propulsion is possible. Normal matter attracts negative mass (note: negative mass is not antimatter), so both will stay apart, while moving forward.
With a tether between the two, the forces will act appropriately. Now, momentum is conserved, as negative mass places a minus sign in the momentum equation, thus equaling zero. It is important to know that the electromagnetic and gravitational forces with negative matter are reversed. Kinetic energy is conserved, even if the craft started at a standstill. One side of the conservation of energy equation equals zero due to the minus sign of negative mass.
In terms of how to create and where to find negative matter, this is unknown. Forward has proposed that some negative matter can be found in the voids of space, as it is repelled by regular matter. Whenever negative matter would be created (if possible), an equal amount of regular matter is too. Antimatter is created in a similar way. The major objection to negative matter is causality, which is linked to the second law of thermodynamics. However, it is allowed in other scientific concepts. Murray GellMann’s Totalitarian Principle states that in physics, “anything which is not prohibited is compulsory.”
An idea by Forward to create an antigravity field is to use a dipole electric field generator. The concept creates mass flow by moving mass around the inside of a torus (donut shaped thing) via electric flow. The magnetic field will fluctuate due to time lag. This field will generate an electric field. This accelerator would be “antigravity,” causing objects on top of the device to levitate. However, the amount of density of the matter needed to be accelerated is the equivalent to that of a dwarf star. Also, the torus would be about as wide as a football field, with kilometer dimensions. The acceleration in this device would be about 10-10 M/S2. However, to counteract the Earth, it would have to be 1011 M/S2 in the pipes. Such a device would too massive to build.
Forward has another torus design (inside-out whirling dense matter torus) which would act like a series of catapults for space travel. Some problems with gravitomagnetic antigravity are the lack of technology to achieve enormous mass densities, extreme speeds and accelerations, and large device dimensions. Some countermeasures, as suggested by Forward, are cooling a gas of neutrons from a nuclear reactor to extremely low temperatures using magnetic forces or magneto-gravitational traps to form tetraneutrons (four neutrons glued together). Another work by Forward was an unsuccessful attempt to transform time-varying electromagnetic fields into time-varying gravitational fields. In Maxwell's Equations a time varying electric field generates a magnetic field and a time-varying magnetic field generates an electric field. However there is no such relationship for gravity.
A strong gravitational field is not required for anti-gravity. The one who discovered this (Felber) also noticed that an antigravity field repels objects in a backwards direction with strength equal to one-half the antigravity field in the forward direction. Because negative energy and negative pressure are acceptable under General Relativity, it is possible to use negative energy as a source of propulsion. It could be used as a bubble around the craft for propulsion. The negative energy density required to overcome Earth’s gravity is on the scale of a dwarf star to neutron star density.
There is a natural source of antigravity. This source causes the universe to continually expand, rather than contract. This sounds like dark energy, but the book labels it Cosmological antigravity. It can act as pressure according to one model. Negative pressure takes energy to expand, not to compress. Essentially, the cosmological vacuum has unlimited energy, and thus can produce unlimited expansion.
Dark energy presents another opportunity to be exploited. This is what composes 74% of the universe. It is responsible for the inflationary effects. It was first discovered while observing the red shifts in supernovae. The properties mentioned here, should make it obvious for its inclusion in the book. Dark energy is almost certainly Einstein’s cosmological constant. The inflation of the universe can also be used as propulsion. I find this somewhat amusing. Technically we are moving away from distant objects due to inflation, but I wouldn't call the propulsion. This force is Λ*r, where Λ is the cosmological constant and r is the separation of the objects.
An energy source is only as useful as its accessible quantity. Dark energy available in a volume the size of our solar system amounts to the mass equivalent of a small asteroid. However, there was an idea put forth by White and Davis to generate dark energy in a laboratory for the purpose of designing warp drives. It was based on D-Brane quantum gravity theory – to be covered in Chapter 15.
The next section of the chapter is Miscellaneous Gravity Control Concepts. Dr. Puthoff worked on his own system of space time coordinates (cylindrical), relying on the Levi-Civita Effect. Puthoff’s thing would be able to slice the speed of light in half by using enormous amounts of power.
Another idea relates to pulsed power. It is not too far off in the future. This uses a laser to generate acceleration. A more interesting innovation would be gravitational wave (GWs) rockets. Beams of GWs are allowed under the General Theory of Relativity. The system works by ejecting GWs into space-time, thus generating propulsion. This has been shown to work when a star undergoes asymmetric octupole collapse, achieving a velocity boost of 100-300 Km/s.
Baker proposed a method to produce GWs in the lab by using a system of small masses (less than the length of a GW) and then oscillating those with a rapid change in acceleration, a jerk (third time derivative of motion). The “rapid jerks” would be even picoseconds or less, relying on powerful electric, magnetic, and other forces. This device would produce GWs with a frequency of 1012 Hz and above.
Another opportunity to make GWs is to produce gravitons in the laboratory via unique electromagnetic field. It is conceivable that a photon could decay to yield a graviton. However, this may be wrong as the photon and graviton are exchange particles for different forces. We have technology today to detect gravitons if we want to according to the book (I have doubts, as we have never detected gravitons which should be emitted from matter-it interacts gravitationally). However, to produce gravitons in the lab would require high intensity lasers that would fire 1019 to 1034 W/m2 power. The current device we have that can achieve the desired goal is the Z-Machine at Sandia National Laboratory.
There is a caveat though in that it can only generate .1% of the required energy (109J) to produce gravitons. The follow up, though is the X-1 Machine, which would be 10 times stronger than the Z-Machine. This shouldn’t be disappointing, because in practice, these types of machines exceed their potential (power output is far greater). Therefore, it is conceivable that the next generation of machines (after the X-1) would be able to make gravitons.
Graviton production can be furthered by second-harmonic photons. The theoretical propulsion system would look like a system of long linear arrays that are about 500m long that are composed of multiple implosion hohlraum segments. All the linear arrays form cylindrically concentric super-arrays. The system works by chain reaction. Each laser fires at the linear arrays, causing the hohlraums to implode, thereby creating a tsunami of collimated high frequency gravitons. The gravitons are excreted out the back end of the rocket.
Another method of procuring gravitons is to use a particle accelerator. There are already portable electron accelerators, so it is possible to use the photon-graviton transformation. However, the power of the beam may not be enough for propulsion.
Yet another way to make GWs are Gertsenshtein waves. These are formed by very high light and magnetic field intensities. They were initially thought to be only produced through astronomical processes, but the prerequisites for magnetic intensities are now available with high intensity 90’s lasers. There are several variations of this idea.
In terms of performance, the GW rocket would have an exhaust velocity equivalent to the speed of light, as the particles propagate outwards at that speed. This is the same speed as a photon rocket. There is one problem though. GW rockets require far more jet power than conventional rockets to deliver the same thrust.
A Casimir device in a weak gravitational field will slightly counteract gravity. This truth helps to prove that negative Casimir energy in a gravitational field will act like negative mass. The force exerted by the Zero Point Fluctuations is too difficult, if not impossible, to measure with current technology. Despite this, E. Calloni has devised a possible way to use the Casimir effect. He would like to use multiple rigid Casimir cavities with a dielectric material separating two thin metal disks inside. The dielectric material is preferably silicon dioxide. There is more to this, but the technical difficulties will currently be placing this idea on the backburner. It turns out that atomic transitions can be caused by zero-point-fluctutations, as these perturb the Hamiltonian.
A proposal by F. Pinto is for the use of Van der Waals forces. These forces are only important at the molecular levels in atoms with covalent bonds, but he has an idea how to boost the strength of these normally weak forces (with polarization, lasers, etc). There are enormous technical difficulties here too.
The next item is a quantum field theory for space propulsion, but it is not necessarily a propulsion concept. Heim devised a weird model for the universe, with two more fundamental forces. He proposes multiple new dimensions, and other ideas. In terms of the propulsion, it is predicted that Heim-Lorentz (see section 3.3 of this link) forces would produce much force, and that gravitophoton interaction can reduce inertial mass by as much as 104.
For the final method, F. E. Alzofon of Boeing Aerospace ’s old is mentioned. He wished to use Al-27 and Cr with Mg (or Fe) to decrease weight via a static magnetic field and pulsed microwave radiation.
To conclude, it seems that dark energy and matter have no immediate propulsion possibilities. However, with major breakthroughs (preferably more compact technology), it is possible to finally use many of the concepts mentioned here (if they would work in the first place). Some things, like tabletop lasers are almost within our reach. Only time will tell if we will ever conquer (negate) gravity.