Even on the Moon, man needed a set of wheels. Now, decades later, as some intrepid developers buy lunar real estate, Science Editor Dick Ahlstrom looks at the type of vehicle needed to get you around your ploton the moon
There is nothing for it: you are being press-ganged into a trip to the in-laws. Getting there is a bit of a problem however, given the dusty, uneven terrain, temperatures ranging from minus 300 degrees C up to plus 100 degrees C and, of course, the lack of air. That is what you get, though, for buying a plot of land on the moon, the latest craze for those with more money than sense.
People are more than willing to put down money on a piece of lunar real estate without considering how they might get there, then build a home and finally go out for a spin to visit the neighbours.
Whatever about the first two challenges, at least there is some track record for motoring on the moon. Three "moon buggies", officially known as Lunar Rover Vehicles, were carried to the moon on board Apollo flights, 15, 16 and 17. They allowed the astronauts to cover initially hundreds of metres but eventually about 100 kilometres as mission controllers became confident the space jockeys wouldn't either crash or get lost.
Sporty was not a term worth using with these vehicles, however. They offered just one horsepower of fun, with a quarter horsepower motor mounted on each wheel. They were also all electric so they were going to be tame in the extreme, with a maximum speed of about eight mph (13 kph).
Suspension was truly independent, given that the wheels were meant to bounce up and over rocks of six to 12-inches without difficulty. Spin-outs were always a possibility but not due to improper use of the clutch. The dusty surface of the moon meant the astronauts were motoring over a surface similar to a talcum powder covered roadway.
Not that they had to worry about a clutch. A single joystick or tee-bar controller handled all movement and this was used to push the moon buggy up to its anything but astounding top speed. Seatbelts were, of course, obligatory.
Even so the moon buggy was an engineering marvel. It was designed to fold up into a tight space to allow it to be carried as cargo to the moon. It collapsed into a sandwich just 1.5 metres on a side and about half a metre thick. Once deployed it provided all the legroom needed for comfort, stretching to three metres long, 1.5 metres wide and a 35cm ground clearance. Deployed it was about the size of a Lincoln Continental town car, akin to a larger Mercedes saloon. When folded up it was smaller than a VW Beetle.
What kind of contact did it have? Well, not rubber anyway. Pressurised tyres are a no-no where there is no surrounding air pressure to keep them from exploding. Instead the buggy ran on "tyres" made of woven piano wire.
It weighed 462 lb on earth but in the much weaker gravity of the moon - just a sixth that of earth's - it weighed a mere 70 lb or so. Despite this, it had a payload capacity of more than double that weight.
In keeping with the latest GPS toys found in today's 4x4s, the buggy sported elaborate navigational systems. It used wheel revolutions to measure distance - nothing new there - but had an on board gyro to detect direction and position from a starting point, handy in the bleak grey featureless surface of the moon.
Have the engineers advanced at all on that early design? Not really, but they haven't had to consider a twin bucket seat buggy big enough for humans for some time. Efforts to reach the moon have been moribund for years, but there are active NASA and ESA efforts to reach Mars within the next decade or so.
So far, however, any rovers sent up have been downsized to be suitable for little more than an oversized rat or underweight kitty. The successful 1997 "Pathfinder" landing on the Red Planet involved the deployment of a small electric powered runabout, the Sojourner rover. It was very slow and didn't cover much more ground than the inside of a small office, but it showed that electric still works.
This hasn't stopped the NASA designers from moving on to the next engineering hurdle: how to get about on Mars in something big enough to carry people. Mars has a major advantage in that it has a thin atmosphere, so winged vehicles are being considered. The carbon dioxide-rich atmosphere wouldn't support internal combustion engines but there is enough "gas" to support vehicles akin to dragonflies known as "bugbots" or "Entomopters".
These generate lift by rhythmically pumping wings up and down like an insect. Theoretically it could hover, land on a dime and cruise over distances.
Unfortunately it would be no use on the moon, which has no atmosphere at all. The wings could pump all they liked but the bugbot would go nowhere.
So what is a moon dweller on the way to the in-laws going to do for a bit of performance? Two options include some form of rocket propulsion or perhaps electricity generated by a fuel cell.
Spacecraft and satellites fine-tune their position in orbit using small compressed gas units using gases such as hydrazine. A large hydrazine propulsion unit might give a new type of moon buggy a lift but braking would become an issue given the low gravitational resistance.
Similar problems would exist for a "Batmobile" type rocket car option. Liquid oxygen and hydrogen could be used to drive a moon buggy, but you are really talking brake horsepower with this type of engine, more than you might want on the moon. Then there is the dust in your wake issue with exhaust gases churning up clouds of dust behind.
The fuel cell might provide the answer, a power unit being explored by some terrestrial car manufacturers looking for a pollution-free electric car that can go for longer than a battery-driven vehicle.
Fuel cells combine hydrogen and oxygen gases to produce electricity and a waste product: water. They can produce power for as long as gas supplies last and so have potentially a much greater distance range than any battery-powered option.
The greater energy supply might also mean you could break out and put a one horsepower or five horsepower motor on each wheel, giving you something approaching "performance" from your electric car.
This would also give you the torque to pull around a much heavier car, one complete with plenty of winged farings, alloy wheels and go-faster stripes.
Then you would be talking impressive lunar motoring as you drove off in your Ford "Moonbeam" or GM "Crater" to go visit the relations. But don't hold your breath waiting for these new models, even if you have put your money down on a few acres of lunar landscape.