Space Elevators and Orbital Siphons

The orbital siphon is in many ways simply an extended version of Pearson's 150,000 km radius orbital tower or space elevator, and within which the sum of the centrifugal or inertial forces acting radially outwards exceed the sum of the gravitational forces acting inwards, with the result that the extended tower exerts a lift force at the surface of the Earth, which can be used to lift up mass at the base of the tower while mass is released at the top.

However, orbital siphons behave radically differently from space elevators such as Pearson's or Clarke's. In the first place, space elevators are stationary orbiting systems, and require little or no lateral constraint. An orbital siphon, by contrast, is in continuous radial ascent, and coriolis forces acting to bend it must be counteracted with either a cantilever truss or transverse thrusters if the siphon effect is to be maintained.

Secondly, space elevators require payloads to perform work (currently estimated as about 50 MJ/kg) to raise themselves up to synchronous orbit. By contrast, orbital siphons themselves perform the work required to raise mass to synchronous and beyond. Space elevators are aptly named, because they are comparable to elevators in tall buildings, which perform work raising elevator cabins. The equivalent analogy for an orbital siphon would perhaps be that of an express train.

Apart from the need for lateral or transverse constraint, to maintain the rising train on a radial ascent path, orbital siphons that consist of a train of linked payloads will find the ties between them reaching a maximum tension at synchronous orbit altitude. Orbital siphons cannot be tapered to equalise tension along their length. However, a system of bracing belts might overcome this problem.

In addition, the need to brake otherwise radially ascending orbital towers introduces new forces into the rising train, and the addition of new payloads at the base, and the release of payloads at the top, tend to generate tension waves that propagate up and down the tower. Also, the tower will have its own harmonic oscillation. The resulting complex motions can entirely destroy the tower.

The Uses of Orbital Siphons

Assuming that the many problems associated with orbital siphons can be resolved, a cantilever truss siphon offers, in principle, a mass launch system that requires no mechanical work to be done to raise mass to escape. Furthermore, since a continuous mass flow is in process, it would appear that an orbital siphon could raise far larger amounts of mass than either conventional rockets or space elevators. A siphon might raise thousands, perhaps even millions, of tonnes of payloads to escape in an environmentally friendly manner (no rocket exhausts, no motors).

In fact, the principal problem for an orbital siphon might be one of simply maintaining a steady flow of payloads into the rising train at its base.

Given a low cost, high capacity mass launch system, it may become possible to use an orbital siphon for a variety of tasks.

1. The launch of very large space stations in the form a tied string of components which are subsequently assembled in space.

2. The launch of supplies of water, food, fuel, and other consumables for such stations.

3. Space tourism aboard space cruisers.

4. The launch of mining equipment for use on other planets or asteroids.

5. The launch of components of space elevators or orbital siphons for use on other planets and asteroids.

6. The launch of space factories manufacturing products with the assistance of zero gravity and or high solar temperatures. Metals might be smelted, ceramics fired, by putting them into near-sun perigee orbits.

7. The disposal of toxic wastes either by escape from the solar system, or by firing them directly into the sun.

8. The launch of military satellites. Should the solar system become a trading system, with cargoes of goods and people travelling in large numbers, the rise of space piracy, asset theft, spaceship highjacking, and even space wars, might necessitate a military presence in deep space.

Seen in this light, an orbital siphon would be principally a one-way system, delivering mass into space, most of which would stay there, with only a few humans periodically returning to Earth, along with a variety of products and products mined and manufactured in space. A trading system would arise between asteroid mines, space factories, and Earth consumers. Orbital siphons would become the equivalent of the Portuguese caravels that opened up terrestrial global trade, only this time colonizing a solar system empty of life.