Air cars are canon in THS.
There is not much mention of them in the original book, however. A few passing references in the text, and they appear as a brief entry in Appendix B, page 193.
In science fiction, air cars/hover cars/etc are often simply depicted as modern cars without wheels.
An excellent example of this trope is seen in “The Fifth Element”, which at least has the merit of being tongue‑in‑cheek.
A big mass of “bonnet/hood” ahead of the windscreen is not a good design feature for a flying vehicle, particularly one intended to operate close to the ground at times.
The depiction of an air car by Dave Gibbons from the 1981 Judge Dredd annual (above) is one of the few I have seen that gives the vehicle a more practical “bubble”, similar to that used on many helicopters.
Why should an air car be car-like? In “Dune Prophecy” the main entrance of an air car is depicted at the rear of the vehicle. As many modern aircraft and ground vehicles demonstrate, this is a much more practical location, particularly if you need to fly with the door open for any reason.
On the Skids
Another common feature of air cars in science fiction is an absence of any form of landing gear. One would think there would be some means for ensuring the finish on the underside was not scratched when powered down. Some provision for clumsy or hard landings might also be prudent.
In “The Number of the Beast” and “The Puppet Masters”, Heinlein has “duos”, vehicles that are both ground car and aeroplane. Unlike most air cars in science fiction, these have retractable wings and wheels.
In one section, a character notes: “First it was a bridge out and I didn’t have room enough to make the car hop it, quite aside from the small matter of traffic regulations for a duo on the ground.” In another book, it is noted that duos are required to stay grounded within city limits.
The air cars of Ampridatvir in Jack Vance’s “Dying Earth” story also have wheels, but these air cars are the more familiar anti-gravity type flyer. There is an interesting write‑up on these vehicles in “The Excellent Prismatic Spray Magazine”, Vol.2, p.42.
In THS 3rd ed. we are told an air car: “Requires Piloting (Vertol) in flight, Driving (Auto-mobile) on the ground.”
It is possibly that an air car moves close to the ground by hovering on its jets, but this seems unlikely. It would be very inefficient, not to mention the noise, the dust and debris this will stir up and the effects on nearby pedestrians, vehicles and buildings.
Although not specifically mentioned, a THS air car would probably have some form of wheels. If these wheels are used for anything more than just taxing into a garage/hanger, they will need to be at least as substantial as those of a ground car. Suspension may need to be even better to handle the stresses of landing.
The requirement to function as both a ground and air vehicle imposes several major design compromises on a THS air car.
Flying vehicles generally try to minimize unnecessary mass. In addition to wheels and suspension, other systems for ground operation such as brakes and motors will be needed. Motoring includes a risk of knocks, bumps and collisions, so a ground vehicle is typically more robust than a dedicated flier. That generally means more mass, or possibly exotic and probably expensive advanced technology materials.
THS claims to be “hard science”, so there is no anti-gravity, magic or handwavium to get the THS air car airborne. There are no apparent wings like Heinlein’s duos. The THS air car only has its jets to lift it.
We are told a THS air car masses 1,400 lbs, laden. Therefore the jets must produce at least an equal force of thrust to lift the vehicle. An air car lifting from or landing on a public street is going to be very unpleasant for just about everyone in the area.
Sky Jam?
Air cars are often portrayed as being as common as modern automobiles. It seems to be hoped that being able to expand into three dimension may ease traffic congestion.
On an Earth where working‑from‑home and telepresence is common place, a significant proportion of the population will not need to commute, and likely to have only an occasional requirement for a personal vehicle.
In many modern cities, the flight path of single‑engine helicopters is often restricted to well defined “air lanes”. Air lanes tend to follow rivers or pass over thinly populated (or possibly poorer!) neighbourhoods. Should there be a problem, the helicopter is likely to come down where it may do minimal damage.
Imagine a city where hundreds, more likely thousands of air cars are airborne at any given moment. With so many vehicles involved, there is a high likelihood of a crash somewhere in a city being a daily event. Anyone living below is going to be rightly nervous!
So many flying vehicles will make modern air traffic control look like a kindergarten puzzle.
And that is just if the air cars are controlled by sensible AI systems. What, if due to machismo/egotism common today, humans insist in piloting their own vehicles?
In THS Deep Beyond 3rd ed. p.148 we are told the Titan-based UH-92 helicopters are derived from a UH-88 helicopter used on Earth.
Alternatives to air cars evidently still exist. Many of these alternatives are likely to be cheaper, simpler, more reliable, faster or stronger.
These are just some of the reasons I find it difficult imagining air cars as part of a credible THS world.
If air cars are a component of your games, it may be more realistic to treat them as in a similar manner to modern helicopters: rare, expensive and generally restricted to the military, police, emergency services or filthy rich.
If a dual mode vehicle is really needed, you may perhaps draw on Heinlein’s duos for some inspiration.
In future blogs I will be exploring other possible forms of transports, some of which may be alternatives to air cars.