Future Projects

"Earth is the cradle of humanity, but one cannot live in a cradle forever."
- Translated from Konstantin E. Tsiolkovsky, Father of Russian Astronautics, 1896

"The meek shall inherit the Earth. The rest of us are going into space."
-- Unknown

"All civilizations become either spacefaring or extinct."
-- Carl Sagan

"Single-planet species do not last."
-- John Young

While the following projects below are not part of the initial effort, they give some flavor of possible future directions after the initial LEO and GEO tethers are in operation. The LEO and GEO tethers will drastically reduce the cost to get anywhere in space. A famous saying by Robert Henlin is that, "If you reach LEO you are halfway to anywhere in the solar system." In our case the saying should be that, "A good toss from GEO and you can get to anyplace in the solar system."

Tourism provides the demand that will justify a Space Tether, which in turn will drastically reduce the cost to LEO. But what happens after this? Reduced cost to LEO makes many things affordable that were not reasonable at high costs. For example, mining the asteroids or sending people to Mars might soon follow. Tourism to the Moon, or even colonizing the Moon, is not too hard once you have cheap LEO transportation.

Lunar Flyby (LF) Hotel

A small hotel that was tossed from GEO on a trajectory that went out past the moon and back (Lunar Safe Return Orbit) would be a natural first follow-on project. The LF (Lunar Flyby) hotel would take customers on an 8 day trip that goes around the moon and then back to get caught again by a GEO hotel. The LF hotel is not limited by the size of the SSTT, as any amount of people and cargo can be collected at the GEO hotel. Since it can only go twice a month we would want it to be much larger than the SSTT. Maybe big enough for 20 to 50 customers or more.

The LF hotel can only be tossed every 14 days because the Moon only crosses through the plane of the orbit that the GEO hotels are in twice every 28 days. So the LF hotel would travel for 8 days and then spend about 6 days in port. The waste from LF hotel would be transfered to the GEO hotel where it would be recycled. Food grown at the GEO hotel would supply the LF hotel.

Lunar Tether

A tether in orbit around the Moon can land payload on the Moon or pick up payload from the Moon. As long as it picks up as many pounds of lunar regolith as it drops of payload, the tether transport will not require any additional energy to operate. The regolith can provide radiation shielding for the orbital hotels. Tethers also make it easy to build a hotel on the moon.

If the tether is in a polar orbit it can service landing/pickup sites all over the moon, including the poles.

The Lunar Flyby Hotel could take people to the Lunar Tether. So a Lunar Tether would follow the Lunar Flyby project.

Lunar RVs

The moon is about 2160 miles in diameter and only rotates once every 28 days. So if you wanted to drive along the Moon's equator and keep the Sun directly overhead you would only have to average about 10 miles per hour. Having sunlight all the time lets you avoid the problem of storing energy for people and plants. Moving along the moon could also make an interesting scenic trip for tourists.

The first step would be to build a dirt road (say 2 meters wide) around the moon staying near the equator. To reduce engineering, this road would detour around major craters and look for gentle grades. After this was done we could have a convoy of Lunar RVs that always had sunlight for solar power and growing plants. So these RVs can make a sort of mobile moon base.

Hermann Oberth [Oberth 1957] designed a Moon Car that balanced with a gyro and could jump. The body of the vehicle was held up by one leg that acted like a big gas shock absorber for a smooth ride. We now know the jumping is not really needed. Today we could do the balancing with a computer as is done in the Segway instead of a gyro. Oberth had two tank racks instead of wheels because he was not sure how soft the Lunar dust would be. Today we know that two big soft tires side by side should work fine. As gravity on the Moon is only 1/6th that of Earth, and there is no wind, the vehicle could be 10 meters square with solar panels even wider than that.

If the Lunar RV rotates forward by a certain amount, say 20%, then 2 front tires come onto the ground for a total of 4 tires on the ground. To get back on 2 tires the vehicle just accelerates hard to "pop a wheelie". In the 4 tire mode a bulldozer blade can be used to clear a road when necessary. Could design it so it could operate on either the back 2 wheels, the front 2 wheels, or either side pair. On the back or front it is like a segway. On a side pair it is like a motorcycle. This way a failure of a tire or motor does not require repair right away. Could also have tow rope so that another vehicle could tow a broken one. We would want bumpers so that if the vehicle ever did fall over it did not hurt anything. The Segway style leaning into the hills would mean that as the RV went up or down a hill that people, or glasses of water, inside did not tip over.

The solar panels could be spaced such so that some sunlight went between them and to the plants growing under them. On the Moon there is no atmosphere to reduce the intensity of the Sun and the Moon Car will move so that the Sun is always directly overhead, so unfiltered sunlight would be too strong for the plants.

With a single big spring and leaning into hills, the RV could provide a very comfortable ride for tourists even over a dirt road at the required 10 MPH. The ride should be smooth enough to move around inside, eat, and sleep while the RV keeps moving all the time.

The moon is only tiled about 1.5 degrees relative to the sun. So the artic circle is about 26 miles from the pole. So you could make a "Path Of Eternal Light" along mountain ridges around the pole such that you would only need to average under 1 MPH to stay in the sunlight. Going along the ridges also makes for nice views for lunar tourists. There can of course be an infinite number of different paths of eternal light.

This makes issues of light for solar, heat control, and light for algea much easier than on a base that is dark for 14 days every month. Oxygen recycling and energy become almost easy problems for a vehicle on the "Path Of Eternal Light".

A similar idea for autonomous robot explorers has been called Sun-Synchronous Navigation.

Lunar Base

There are mountain tops near the Lunar poles that always or nearly always in sunlight. A tower of solar panels that rotated ones every 28 days could always be in sunlight. This would be a nice place to locate a Moon base.

Also at the poles are be craters that are always dark. These craters have radiated heat, and become very cold. Because of this there seems to be ice available there. It should be relatively easy to collect this and warm it to get water.

Movie/TV Industry

Movies or TV shows could be made in space or on the moon. Because of the novilty they could get more viewers. This could be travel shows, reality TV shows, sports shows, the next James Bond movie, etc. The possibilities are endless. There have already been talks where someone making a TV show would pay part of the cost of sending someone up on a Soyuz.

Mining Asteroids

As mentioned in the discussion of investment opportunities, asteroids are an attractive source of precious metals.

With SSTT, getting to our GEO hotel is very inexpensive. If we wanted a mining vehicle vehicle bigger than one load of the SSTT we could assemble it at the GEO hotel. Then the mining vehicle could be tossed toward an asteroid. When material is coming back from the asteroid it could use aerobreaking to slow down. This is would make mining the asteroids so much cheaper than it is today that it should be profitable.

In this picture of Eros you can see house sized boulders. If a tether were attached to these and they were pushed out a bit the spin of Eros could be used to give them a good velocity. You could then release at the right time and send them toward Earth.

Mining Asteroids on Moon

Many asteroids have impacted on the moon. These impacts brought precious metals to the surface of the moon. The metals could be mined and brought to Earth.

Mars-Earth Rapid Interplanetary Tether Transport - MERITT

MERITT - Mars-Earth Rapid Interplanetary Tether Transport system [Forward 1999]. Robert Forward and Gerald Nordley did an analysis of a tether transport between Earth and Mars. From their abstract; "Routine travel to and from Mars demands an efficient, rapid, low cost means of two-way transportation. To answer this need we have invented a system of two rotating tethers in highly elliptical orbits about each planet. Tethers with tip velocities of 2.5 km/s can send payloads to Mars in as little as 90 days. Tether systems using commercially available tether materials at reasonable safety factors can be as little as 15 times the mass of the payload being handled."

In a detailed example, the initial Earth tether orbit has an eight hour period, an apogee of 33,588 km, and the tether and control system have a mass 15 times the payload. After toss, the Earth tether orbit apogee is only 24,170 km, and the period is 5.37 hours. This sample takes 150 days to get to Mars. A tether in orbit around Mars, with an apoapsis of 21,707 km catches the payload, soaks up 4 km/s of payload velocity, drops it for entry at Mars with a 2.4 km/s velocity. The Mars tether finishes with an apoapsis of 115,036 km. Aerobrake could reduce the load on the Mars tether.

Pioneers to Asteroids

Some people may decide to live and raise families on asteroids. This would be the ultimate in freedom from oppression. As John Lewis puts it in [O'Neill, 2000, page 137], "Keep your laws off my asteroid". Asteroids have some real advantages, on top of being so far away from everyone else that nobody will bother you. Shielding from radiation is easy, as there is plenty of mass available. You can mine the asteroid for many of the things you need, like oxygen, metal, water, carbon, etc. You can make a small asteroid keep one side facing the Sun so you always have solar power. Winching out some mass from a rotating asteroid on a long tether absorbes a large amount of angular momentum per Kg.

Phobos Deimos Tether Ladder

Paul Penzo in [Penzo 1986] discusses the use of Mars Satellites for transfer between Low Martian Orbit (LMO) and escape. Phobos and Deimos are small, less than 20 km in diameter, but that is huge by tether standards. They are low, and in equatorial orbits.

A 375 km tether in LMO, can toss a payload to a 1160 km tether hanging from Phobos. An elevator lifts the payload to Phobos, then another elevator lifts the payload up a 940 km tether above Phobos. This allows a toss to a 2960 km tether hanging below Deimos. Here a pair of elevators lifts the payload to 6100 km above Deimos, where the payload will have escape velocity.

This process saves 1.6 km/s that would be supplied by propellant. It can work in both directions. Penzo's analysis was done with Kevlar; Spectra 2000 would use less mass. The elevator is a slight problem, one that rotating tethers avoid by turning to release the payload. Since the down and up lengths are different, an elevator or winch of some kind is required for this system.

Penzo also has numbers for a Lunar Station to assist transport between the surface of the Moon and trans-Earth orbit.

Penzo has two pages on the use of EDT to maneuver in Jupiter's magnetic field. The magnetic field at Jupiter is much stronger than around the Earth.

This is a fun vision of some of the capabilities of tethers.

Space Solar Power

As they say in [Glaser1998, page 184], "The primary economic problem now preventing an SPS system from being built is the lack of cheap access to space.". Land for a microwave power receiver would be like 30 times smaller than land for a ground based solar power system. A solar power station in GEO can collect solar power nearly 100% of the time, so unlike a ground based solar power system you don't have an energy storage problem. On the ground you average only like 25% of direct sunlight (with nighttime, angle of the sun, and clouds). Even full sunlight on the ground is less than full sunlight in space, since the atmosphere blocks some. A ground based solar power system would need to have a energy storage system which also looses some power. In space you don't need to buy the land to put your solar collectors on. Beaming power by microwaves seems possible. If the energy density on the microwave beam is the same as sunlight, it would take something like 30 times less land for the same net power. The microwave conversion is around 90% efficient, where solar is more like 20%. With nighttime, clouds, and storage losses, you need a lot more land if it is covered with solar collectors than with microwave receivers. The microwave receiver is a bunch of wires which would let most of the sunlight through. So the land underneath could be used for agriculture in the microwave case, and probably not for anything else in the solar case.

With affordable launch prices, space solar power would make economic sense. In [Glaser, 1998, page 541] they estimate that space solar power becomes competitive at $320/Kg.

In fact, some of the space solar power enthusiasts have recognized that tethers might be the way to get low costs to GEO. For example in [Glaser1998, page 551] they say, "A large tether system could be used to place payloads on a geosynchronous transfer orbit. A second tether system could be used to 'catch' the payloads at apogee and complete the transfer. The low Earth orbit tether system could be a rotating tether or an oscillating tether. The high-altitude system would very likely be a rotating tether.".

Fusion power gets about $1 billion a year in federal funding. Space based solar power seems easier to achieve than fusion and would solve our future energy needs just as well. However, it does not get anything near the funding fusion research gets.

O'Neil Style Colony

The O'Neill plans in 1975 [O'Neill, 2000] were based on an expected $100/lb to orbit on the coming space shuttle and an electromagnetic catapult on the Moon. Prototype electromagnetic catapults were built and the ideas for these were verified. However, when the shuttle turned out to be like 50 times more expensive than advertised, the O'Neill plans suddenly became too costly.

With affordable launch prices, we could see the O'Neill vision realized.

Mining Mercury

Mercury is orbiting the Sun fast enough that 3 times a year you could conveniently ship things between Mercury and the Earth. This transfer orbit needs a high DV, so tethers would make the difference between very expensive and economical. There is no atmosphere so tethers could go down to the surface. There seems to be ice in craters at the poles that are always in shadow. This is the best hypothesis explaining the data from Earth based radar. The Sunlight is 7 times as strong, so a solar sail reboost for a tether would be even more attractive, as well as collecting it on the surface. In these same shadowed craters you could build a base for humans.

Mercury has a thin crust; precious metals or just heavy elements should be more accessible than on the Earth [Gillett1996].

Search for Extra Terrestrial Intelligence - SETI

The 3 largest movable radio teliscopes on earth are 64 meter Parkes Radio Telescope, the 75 meter Lovell Telescope at Jodrell Bank, and the 100 meter Effelsberg near Bonn. The Allen Telescope Array is made of 350 dishes each 6.1 meters in diameter to get around the problems of building a single large dish. The total area is 10,229 sq meters which is the same area as a 114 meter diameter dish. There are advantages and disadvantages to having lots of small dishes so it is not the same as one large dish, but that discussion is beyond our scope here. The 305 meter Arecibo Observatory in Puerto Rico was built in a crater and can not move. Building a large dish and keeping the shape exactly right even when it moves to different positions is hard when you have gravity. But in orbit there is no gravity problem, so you could build very large movable dishes and hold the shape. A small 8 meter diameter radio telescope called Halca was launched in 1997. While gravity does not limit the size, the launch costs currently does. However, with greatly reduced launch costs it would be practical to make a really large dish in space. A bigger dish collects more signal and so can detect signals that a smaller dish can not. The signal collected goes up with the radius of the dish squared. The strength of a signal goes down with the distance squared. So with twice the diameter dish you can hear the same power transmitter from twice the distance. The volume of space you can search goes up with the cube of the distance you can listen at. So if you can listen to things twice a far away you can search 8 times the volume of space. If you can listen to things 10 times as far away then you can search 1,000 times the volume of space. So a bigger dish increases our chances of receiving a signal from extra terrestrials. While this is a high risk venture, the value of the information found could justify the investment.

Mining He3 on Moon

He3 from the sun has been deposited in the surface on the Moon. It could be mined and brought back to Earth. If He3 becomes is used in fusion power, as some people anticipate, it could be valuable fuel. Click for SpaceTethers.com