Comparing Rocketry, Tether Elevators, and KESTS

Comparing Rocketry, Tether Elevators, and KESTS
J E D Cline 20040913

There are various layers of detail and scope by which something can be described. Fields of possible relevance to the reader are significant, too; some people will be interested in one kind of thing, whereas other people interested in a quite different factor. So here is an effort to provide a basic description of the basic principles of rocketry, anchored tether space elevators, and KESTS to GEO spacerails; in basic physics and psychology aspects.


Rocketry utilizes the physical principle that every action has an equal and opposite reaction; useful operating in a field of gravity. The force on the propellant mass being expelled out of the rocket engine is equal in amplitude and opposite in direction to the force on the rocket itself. That action, or force is equal to the product of the mass and its acceleration, the mass of the expelled propellant being small and its acceleration very high, whereas the opposite-direction acceleration on the rocket of much vaster mass, is small. If the force of gravity on the mass of the rocket is less that the upward force generated by the downward thrust against the expelled propellant, the rocket moves up away from the earth. The energy that accelerates the propellant, and thus the rocket, comes from the combustion reaction between the propellant fuel and oxidizer carried by the rocket. Nearly all the energy consumed is used to lift the fuel itself and its support structure, only a tiny fraction of the energy gets given to the lifted payload. But this is the best way we now have for getting up into space, and most importantly, it works. And the psychological factors of the sight and rumble of a spectacular rocket launch inspires excitement in people, psychologically evocative. Rocketry business provides much power and wealth and high profile presence to a lot of people, inspiring its continuance even though useful mostly for emplacement of lower orbital satellites, LEO Space Station service, small GEO com and survelliance satellites, and future rare high profile manned space exploration adventures following unmanned ones. Worthy goals; but surely by far not the best ones.


A vertical elevator tensile structure supported by the outward centrifugal force on mass of the tether beyond the balance point GEO, upon which elevator vehicles climb up and down. Made of a tether material that has a suffiecently high strength to mass ratio and is sufficiently durable, a tether anchored to the earth surface equator and extending vertical so high that its counterweight mass beyond GEO exerts sufficient outward centrifugal force due to the Earth's rotation, to offset the gravitational force on the mass of the tether material below GEO, appears atractive for building a Space Elevator. Power to run the motors of the climbers that bring payload up and down the tether would be sent by high powered laser beams aimed at the vehicle as it rises up from ground to space and back; avoidance of toasting the tether material with the laser is a requirement, as well as precisely tracking position of the rectenna on the climbers on the tether. Pairs of such tethers side by side would allow two-way traffic. Tether material with a tensile strength to mass ratio sufficient for a constant crossection makes for much easier construction and reproduction techniques. The tether Space Elevator concept is getting much attention since 2002, with the prospect of carbon nanotube matrix material hopefully becoming available soon.


KESTS to GEO (acronym for "Kinetic Energy Supported Transportation Structure to Geostationary Earth Orbit") would be of a complexity level about par with one's CD player, though of such huge perimeter that it would totally encircle the planet, eccentrically connecting between ground level at the equator, around and up to GEO on the other side of the planet, in a huge loop. It would use the centrifugal force from high velocity mass circulating within the structure to press outward just enough to balance the force of gravity on the structure with its loads. Electromagnetically coupling some of the momentum of the upward-bound portions of that high velocity circulating mass stream, inductively drags vehicles with their payloads up between ground and GEO; and gently returns them back to the ground. Electrical power is input at the ground terminal accelerators to restore energy consumed by the transporation system.

It would utilize the physical principles of electromagnetism and centrifugal force within the gravitational field of a planet. Electromagnetism utilizes the principles that opposite polarities of magnetic fields cause a pull toward each other, whereas polarities that are the same shove away from each other, and that current flow creates a magnetic field, and a changing magnetic field creates a current flow. Centrifugal force occurs when a moving object has a lateral force applied toward a central point, in this case the lateral force is a combination of gravitational pull on mass and lateral thrust against a curved track. Much like a combination rotary and linear electrical motor stretched very thinly all the way around the Earth into an eccentric loop between ground and GEo above the opposite side of the planet. Electrical power, initially from conventional electrical power sources, is applied to electromagnetically thrust the motor's armature segment mass stream, thrusting against the mass of the earth, accelerating the motor's armature mass stream, transferring kinetic energy to the high velocity armature mass streams. The mass streams experience lateral thrust both from the earth's gravity as they travel around the earth, and by lateral thrust in the same direction as they are deflected by the curved track of the motor's stationary structure. The armature's thrust against the curved track reaction force, is set to exactly balance the force of gravity on the mass of the stationary structure with its loads, supporting its weight thusly by energy instead of primarily by strength of its materials. This enables the existence of such an immensely high structure.

The high velocity armature mass streams share some of their upward-moving momentum, via electromagnetic coupling, to lift spacecraft up along other sets of maglev tracks on the structure. Thus the spacecraft need lift no fuel mass for the journey between ground and GEO, making it inherently highly efficient transportation, as compared to rocketry between the two locations.

So overall, electrical energy is input to the motor system at the ground, the energy is stored in the structure and supports the structures weight and lifts spacecraft along the structure between ground and GEO. GEO is selected as the destination site because it is motionless relative to the earth surface, thus the transportation structure can maintain a solid link between ground and facilities in GEO without use of intermediary free-flying spacecraft with their propulsion and connections factors. The psychological factors include the lack of high profile persons in the field, just one impoverished older man fairly invisible to the public, stifled by the establishment; few dare to side with him.

Both tether space elevators and KESTS to GEO would severly compete with conventional satellites and rocketry, for exclusive right to use the space below GEO, since collision of an orbiting object with a stationary structure would be catastrophic for both. With easy and efficent electric transportation to GEO, most if not all of the functions now served by objects below GEO, would be relocated up to GEO. Space Station would be a special case; in GEO manned habitation would need more passive shielding, particularly until the charged particles are soaked up out of the radiation belt there by large quantities of mass placed there. Probably we would just build an initial 1976-designed Stanford Torus there in GEO instead, particularly utilizing KESTS transporation capacity.


The long term sources of energy for rocketry come from remaining fossil fuel sources, although electrolysis of water electrically from nuclear reactor electrical power could expensively generate some fuel in the future. Use of rocketry to lift people to space seems limited to a chosen few, now and in the future, because of this.

Anchored tether Space Elevators would utilize energy from ground conventional resources at first. When used to build solar power sources, some could be used to generate laser power to follow the vehicles, like from ground lasers, but instead from lasers located in GEO.

The long term sources of energy to sustain and power the KESTS to GEO come from the solar powerplants it enables built in GEO, so it will provide its own transportation energy, as well as provide clean electrical power for civilization on the planet below. Since it will not be limited by energy from ground sources, and can be scaled to whatever capacity desired, and that it can have continuous rail traffic, it seems reasonable it can handle the commute traffic of a modern metro rail system: a million people a day. To space.... This might come in handy if we have to make a temporary exodus to cities built in GEO if the ecosystem has catastrophic collapse and drastic measures are needed to boot it back up again to working program, before comming back. The temporary exodus seems much more humane to me than the alternative. Even without such an incentive, a large civilization presence in GEO cities makes sense, and allows healing of the ecosystem of a few decades hence.

Of course, we have got to get our act together as Humanity for this, or any other scenario, to work long term. This seems a much more challenging part of the task, compared the technological challenges involved, since we clearly enjoy having a conflict fracas, far more than taking on mutually beneficial construction projects together. Can wisdom be taught in school, along with the 3 R's? How? When? Soon enough?


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