So, whereabouts are you? And what will the train look like? What sort of track will it run on? How fast will it travel? How big will it be? Here, in a flight of fancy, I try to envisage the main surface transport on either the Moon or Mars as it may be at some time in the future.

We have already seen on TV various manned and automatic roving vehicles on both Moon and Mars, While they might be suitable for low-speed, short-distance operations, they are far from being mass carriers. In the film "2001: A Space Odyssey" we saw another type of vehicle - propelled by rockets and also maintained in altitude by more rockets. In the initial stages of exploration, such vehicles may be acceptable, but they demand a large amount of rocket fuels or working fluids and are therefore more than somewhat expensive to operate.

This writer believes the type of system for the low-gravity, airless (or nearly so) planets will be similar to an Alweg monorail (and surely you've seen films and pictures of two such systems - at Haneda airport in Japan, and at the Disney Futureworld where it passes through the hotel. A central rectangular beam made of a concrete-like material; the beam would sit on edge, either directly on the ground or supported on columns of any necessary height. This would entail minimum earthworks. Where the beam is deliberately above ground level, either to allow cross-traffic, or to cross valleys and craters, the bottom and part of the sides of the beam would be partially encased in a metal sheath to act as a tension member. Vehicles would straddle the beam, a pair of diamagnetic guide pads vertically separated, close to, but not touching, each side of the beam at each end of the car. Pads, slightly pivoted, rather than wheels, to avoid the need for moving parts and the difficulty of keeping them lubricated in a vacuum. The surfaces of the pads would be teflon or similar plastics with a very low friction coefficient. The weight of the car would be taken by a pair of wheels at each end of the car; those wheels would be powered by electric motors fed from either on-board storage batteries or fuel cells (for emergencies) or by power picked up by induction loops from conductors imbedded in the track beam.

Away from turnouts, the speed of the vehicle would be automatically limited by sensors in each car sensing transponders in the track (or at trackside). The beam axis, normally vertical, would be inclined to one side or the other at curves to allow higher speeds than otherwise.

What sort of speeds? Through turnouts and at recognised stopping places, the speed could easily be kept down to, say, 20 km/hour. But elsewhere, speeds up to 300 or even 500 km/hr should be practicable. Personnel vehicles would, of course, be pressurised, heated and lit; but cargo trailers need not be lit as a matter of course.

Let us have a look at one of the personnel vehicles. It can seat 20 people (with no provision for standees) in upholstered seats, each with an airline-style folding table. There would be a display screen up front for entertainment and information such as the time, speed, distance from last station, distance to next station, and passing scenic attractions.

There would be a driver and a cabin crew of 1 or 2 who would serve refreshments (again, airline-style) from a small galley en route. Two-way communication with the train control room would be achieved through antennae built into the track as well as direct satellite links once those are established in orbit.

Route di- or con-vergences could be by way of traversers at each junction point, one part maintaining the straight-through route, one part with the alternate route. There would be no other crossings.

Signalling would not be by the traditional trackside signals, but on the driver's console, which would also indicate any warnings to the driver. The on-board computer would manage all train systems including the sensors monitoring the driver's health and attention.

As a matter of safety, the steward or stewardess would have to be a trained paramedic, and a moderately comprehensive medical kit would be part of each car's equipment. Additionally, there would, of course, be leak patches for both the cabin walls and for exposure suits. And a sufficiently large stock of air, water and food should be carried on every trip to maintain the entire complement, crew and passengers, for up to a week.

Now to take a closer look at the passenger vehicles. Structurally, they are a monocoque shell with deep. thick skirts each side. The skirts straddle the main beams, with pairs of guide pads on either side of the beam space at each end. Those pads serve to guide the vehicle and to maintain stability on curves (which have a pronounced tilt to avoid excessive apparent lateral forces when negotiating those curves at speeds lower than the design speed for each curve. The "normal" design speed would be fairly high - as much as 300 km/hr.

The vertical support and tractive forces would be provided by closely-spaced pairs of wheels near the extreme ends of the main body, under the control cabins (there would be a cabin at each end of every vehicle, both personnel and freight). Why two wheels rather than one? For safety, if nothing else.

Provision is made for vehicles to run in multiple, under the control of just one driver, with automatic couplings to include not only the mechanical connection, but also the various control circuits and air supplies. Every vehicle, however, is capable of independent operation. The skirts would contain much of the mechanical equipment except life support and passenger comfort items: fuel cells for emergency power, motors for the main support/traction wheels, and the equipment for the wheel at each corner - auxiliary steerable wheels which have their own wheel motors. Those wheels come into play only at turnouts and in places where the vehicles are required to be manoeuvred on the flat - as at marshalling and assembly locations.

At turnouts and in the maintenance areas, the maximum speeds would be automatically limited to walking pace as there would be no main beam to be straddled. At the exits and entrances to those areas, the main beam would be tapered down to zero width and height, and there would be provision for manual steering where required. The normal directional control, however, at turnouts would be fully automatic under the surveillance of the driver. Power for the vehicles (other than the emergency or standby batteries or fuel cells) would be picked up from induction loops built into the beam surface. It would be alternating current, thus imposing a maximum speed limit on the vehicles.

A further development would be for the track power to be in the form of a linear motor, the stator being part of the beam, and the armature being part of the vehicle itself. This would obviate the need for any current pickup such as we of the 21st century are accustomed to see with our electric trains and their pantograph power collection arrangements.

The main body of the vehicles would be approximately three metres wide with a single row of seats on each side. There would be twenty passenger seats, each being reclining and swivelling, each with a built-in tray (as in today's best airliners).

At one side of the passenger compartment at one end would be a luggage locker and a small toilet compartment; at the other end would be a small but adequate galley able to heat and serve a variety of meals and drinks. The driver's compartments would be slightly raised to allow the driver to directly view the train and the surrounding terrain and track. Those compartments would be at the extreme ends of the body. For the convenience and pleasure of passengers, there would be ample viewports beside each seat, each being able to be independently controlled to filter the outside light.

A "shirt-sleeve" environment would be maintained in every vehicle, with the atmosphere kept up to 20ºC, 60% relative humidity, 30% oxygen content, and a pressure of 500 millibars. Let us take a short trip on one of these trains - say, from the Meteorological Observatory in the Sinus Medii (Central Bay) - in the exact centre of the Moon as seen from Earth - to visit the landing place of Apollo 14 in the Fra Mauro Uplands. That is a journey of some 650 or 700 km, passing to the south of the 9,840-metre Mösting and to the north of Lalande (9,610-metre) peaks.

At Sinus Medii, we wait for the incoming train in the partially-buried dome, saying our farewells to the observatory staff. Soon, an announcement is heard, "Keep clear of the platform edge, please. The train for Fra Mauro is approaching."

It appears through the airlock and coasts to a stop. The small airlock door of the cabin opens, some people get off, and we get on. Our cases go into the luggage compartment, and we take our seats. Very soon, the stewardess announces, "Welcome to the train to Fra Mauro and points south-west. Please take your seats for departure. If you are unfamiliar with the normal features of the train, please read the card in your seat pocket."

A buzzer sounds, and we start moving slowly towards the airlock; the door opens, we enter, and the door closes automatically while the air is pumped out. We notice no change in the passenger compartment, however. Very soon, the outer door opens and we gather speed, accelerating to the cruising speed of 250 km/hr.

Our journey time will be just over three hours, during which time we are free to view the scenery, watch any of a selection of films, or to socialise. We will also enjoy a meal en route.

The scenery starts to become more rugged as we leave Central Bay, and we have pointed out to us the two main peaks we pass. After Lalande, the terrain becomes flatter and more featureless until we approach the Uplands, We are nearing the Apollo 14 landing site - where the early explorers Alan Sheppard and Gary Mitchell, in 1971, wheeled their "Mooncart" almost to the lip of Cone Crater.

As this is a special sightseeing trip, we are told that we may take a walk around outside - which means donning vacuum suits and exiting, one-by-one, through the airlock to the small platform whence we take a short walk under the guardian eye of one of the more seasoned personnel. We view the landing site and the remaining part of the Lunar Module; we inspect the Mooncart and marvel at the endurance of those two pioneers; we take some "touristy" photos, and then it is time to get back aboard for the return trip to the Observatory at Sinus Medii.

The stewardess apologised to us for unintentionally misleading us - we were not to carry on to "points south-west", but would be returning directly. The track continues on to the south of Euclides, across the Sea of Moisture and the Marsh of Disease before coming to Tycho (where can be seen, in pristine condition, still, the famous TMA-1 Monolith, and on to Clavius Base. Perhaps another time, and we would make a longer trip. Maybe even to some of the other scenic attractions such as Hyginus Rill where the track is carried on columns high above the floor of the Rill; maybe, even, to one of the Far Side places - such as the radio-astronomy observatory in the vicinity of Crater Daedalus, as far from Central Bay as it is possible to get, and the quietest place (for the radio-astronomers), being screened by the whole bulk of the Moon from the noisy Earth.

-- © Garvan Laing, June 2001