by Richard Penn
The colony is split between a station orbiting the asteroid and buildings on the surface. The colonists have spent more of their lives in a station than on a planet, so many of them are reluctant to move to the surface.
See also Station, Ground Station.
Terpsichore Station
See Station, Ground Station.
Time
See Calendars and Clocks.
Tilt
Rotation in the direction which moves your nose up or down, like nodding the head, sometimes referred to as ‘pitch.’ Commanded by rotating the feet at the ankle. See Directions and Rotations of a Boat.
Transit Colonies
Not so much a technology as a method of exploiting existing asteroids. This is based on the fact that several of the 200,000 known asteroids have natural orbits which pass fairly close to Mars or the Earth and then later pass close to specific asteroids in the belt. It is assumed that colonists could hop onto ones which pass relatively close (within 4 Gm or so) and at relatively low speeds (up to 5 km/s), refuel on the transit asteroid and then hop off when they reach their destination. The transit orbits typically take from six months to a few years. My model assumes colonists will prefer the shorter ones, but will take a longer time if the target is attractive.
The population model assumes that women will choose not to become pregnant if they are on a transit colony, because of the higher risk of radiation exposure, and that children younger than about two will not be embarked on them. This results in some odd demographics in colonies which, like Terpsichore, have been travelling for a number of years. In the case of Terps, it means that there are very few teenagers, but numerous people in their thirties and younger children.
My model of the solar system suggests that such rocks pass close to the Earth every few years, and close to Mars several times a year, providing chances for colonists to head out on any of these. There are many simplifying assumptions in my calculations, and of course I may be plain wrong. I assert only that it makes for good stories, and that it is more credible than most accounts of travel to the Belt. I have a complex simulation of the spread of colonists via the various transit asteroids which become available, using realistic but simplified orbital mechanics. I found I needed to simulate the hiring and training of professionals, as the availability of doctors, engineers and farming experts becomes a limiting factor in the division of colonies into smaller units.
My story says that the colonies passing close to Earth are only used in the early stages (e.g. Gordonmoore), and that later colonists tend to set out from Mars, where the distances are shorter and the delta-V requirements less. Hence the Mars system, specifically Phobos, becomes the ‘centre’ of the Belt.
Tug
An enlarged version of the scooter, with a stronger engine, larger fuel tanks, and manipulators more like those on a backhoe. This is used to move heavier things around, such as barges. It is very quick without a load, so used in emergencies for rescuing other boats. The hold need not have its own rocket motors, the tugs can push it out of the way if collision with an incoming rock is imminent.
The cabin has a driver’s seat (1) with a removable back in case the driver is wearing a spacesuit. Intended for use over several days, it has a toilet(2) but no shower. The fuel section is extensible to allow more tanks to be added and may have a skid (3) for surface landings. There are hatches (4) on both sides of the boat, so two scooters can dock to it on out runs.
In catching an incoming barge, the tug would go out empty at quite a high acceleration (1000 mm/s2 or so), spot the barge and match its velocity, latch on to it and then slow it down to approach the hold. This might take a few days, to allow for the deceleration time while attached to the loaded barge. While the operation could be precisely planned, it is quite an adventure for the young people involved. In the story, one or two scooters accompany the tug, for safety and to help get a grip on the barge.
Tunnel
See Farm Tunnel.
Units
See Distance, Speed, Gravity.
Yaw
The rotation of a boat which turns the nose to the left or right, like shaking the head. Positive yaw moves the nose to starboard. See Directions and Rotations of a Boat.
Year
The time taken for a planet to go around the sun. The two calendars in use in the system use the year of either the Earth or Mars. Asteroid years are anything from three to six Earth years, but they are not used in calendars as they have little effect on the colonists. See Calendars and Clocks.