The Lunar Stairway
The principle of “Gravitational Slingshot” is well known and has been and is regularly used for interplanetary trips, However, by using RotatingTethers.com to both throw and catch mass packages (any containable mass will do) between 2 ships this slingshot provided inertial acceleration can be transferred via several ships to boost cargo from LEO-PORT towards the moon – and/or to boost cargo from Lunar Low Orbit towards Earth.
Lunar Low Orbit speed is only about 1Km/sec, compared to Earth's 7.5Km/sec, and Lunars lack of atmosphere means that Lunar mass can be picked up DIRECTLY from a Low Lunar Orbit (50Km) by a 50Km RotatingTether …. and that packages can be gently placed down, the same way. Using one of our moons four “frozen orbits” even with no hardware on the lunar surface, a scoop can pick up dusty “regolith” or selectively, rocks...there may be several seconds of contact or nearly contact time to choose which spot to pick up from. This needs a human operator onboard the (500 tonne) tether anchor ship – or at least within a few thousand Km of the pickup point
A 50Km Tether describes a 300Km circumference. At 1Km per second (counter orbital speed) the delta-v per revolution is 6Km/second per revolution, which takes 300 seconds – tip acceleration is 20m/sec-sec or 2G – low enough even for human passengers to endure for several hours. Cargo could handle 6G – a 100Km circumference 18Km radius tether in an 18Km very close orbit – this would allow a load (such as machinery) to be placed down, and (1 tether revolution later) an equal load could be picked up, 100Km downrange of the drop-off point, without having to re-boost the tether anchor ship – most probably requiring a fuel burn – a sort of “elevator and counter-weight” arrangement.
lunar material contains Aluminium Oxide which can be processed into liquid fuels (Cryogenic Oxygen and molten Aluminium) but even “worthless dust+ contains a LOT of energy by its position – a lot less energy is needed to raise material from Lunar to L1 (the point of equal attraction from moon and from Earth) than is given up in the much bigger and stronger gravity field of descent to Earth.
the (50Km) tether tip can reach the surface from the very low (50Km) lunar orbit with zero or minimal propellant use. This acts a bit like a water siphon – once it is started, it can self maintain, AND provide Inertial Energy, AND provide mass. It would need about 6 extra ships (of 3,000 tonnes each), but they can be built smaller to start off, (perhaps only 500 tonnes and a crew of 12 only....and gain mass to larger size all from the moon and “pumping orbit” almost “for free”
Beyond Earths moon
The initial Haven1 design is Hamlet sized (above 100 persons), and can grow to Village sized (above 1000 persons) and possibly up to Town Size (above 10,000 people) before fundamentally changing design shape. (perhaps towards spherical) At City size (above 100,000 people) it is more likely to be spherical or a very large tube or disk. Such constructions need a usable (but low) gravity such as Deimos – ditto for mining operations. We do not want to pollute Solar Orbits the way we have polluted Earth Orbits. Manufacture of such big components must be done in containment, and a very light gravity containment is best, hence the choice of Deimos. There are several Large asteroids of similar mass that can also be used, but getting to LEO-PORT comes first, then gaining materials and mass from our own moon to make the trip to Deimos. There are ATEN and TROJAN asteroids which are being discovered (4 of about 100metres diameter, 1 Million tonnes discovered so far), but they may be too fragile and not heavy enough to use without first encapsulating them. So processed, however, they can anchor a very big Rotating Tether to propel our 3,000 tonne ship to Mars orbit without having to raise propellants from Earth first. we may otherwise need 10,000 tonnes for the one way trip.