At Last, Flying Cars? 194
ColdWetDog writes, "OK, we've all whined about the fact that we are now firmly entrenched in the 21st Century and no flying cars. So it is gratifying to see that our good friends at DARPA are finally going to do something about it." The project is called Transformer TX. "The Government's envisioned concept consists of a robust ground vehicle that is capable of configuring into a VTOL air vehicle with a maximum payload capability of approximately 1,000 lbs. ... Technologies of interest may include: hybrid electric drive, advanced batteries, adaptive wing structures, ducted fan propulsion systems, advanced lightweight heavy fuel engines, lightweight materials, advanced sensors, and flight controls for stable transition from vertical to horizontal flight. ... Like all DARPA projects Transformer TX is unlikely to succeed at all. Even if US Marine rifle companies one day do ride to war in handy four-man sky jeeps rather than cumbersome choppers or Humvees, that doesn't necessarily mean flying cars for all any more than Harriers or Ospreys did."
Flying Cars Energy Hogs By Nature (Score:5, Interesting)
Unless someone develops a low energy input, low mass anti-gravity mechanism, flying cars are never going to be commonplace, merely niche vehicles.
The why should be obvious: it takes a lot of energy to get one in the air. Even standard small prop aircraft gets middling mileage [cessna150152.com], and earns points only by its ability to fly in a straight line. However, it needs a lot of room for take off and landing.
Hence, a practical flying car needs to be VTOL, which is by its nature very energy inefficient.
Re:energy density (Score:3, Interesting)
If they were single-person they may be able to pull it off. Most commuters are individuals anyhow. I've seen an interesting vertical capsule design in which the capsule becomes kind of a semi-horizontal "flying wing" upon flight. This reduces the weight of the wings because the body itself becomes most of the wing. It's more like a flying (rounded) TARDIS than a flying car :-) (I'll see if I can find the link.)
No problem, just cost and fuel economy. (Score:4, Interesting)
There's no fundamental problem in building a modest-size VTOL craft. Many have been built. The fuel consumption and cost will be high, but for the military, that's OK.
The big problem back in the 1950s was stability. Now that unstable aircraft are routinely computer-stabilized, that's far less of a problem. It's going to need a jet engine. Piston engines don't have the power to weight ratio needed. That's what runs up the cost. A basic problem with jet engines is that they don't get much cheaper below small bizjet size. That's why general aviation is still piston-powered, despite Williams, etc.
It's not going to be a pure-thrust VTOL, like the Harrier. That takes so much engine power that it's only feasible for fighters, which are mostly engine anyway. Ducted fans, maybe. Successful ducted-fan aircraft [wikipedia.org] have been built, and with modern stabilization, there are several robotic ducted-fan craft. With better stablization, the fans can be pulled in closer to the body, making for a much more compact craft.
There's a new Israeli ducted-fan craft, the AirMule [aviationweek.com], which is currently in early flight test and can hover tethered.
A big problem with single-engine VTOL aircraft is that they fall like a rock if they lose engine power. Aircraft can glide and helicopters can autorotate, but VTOLs can do neither. Ejection seats are indicated.
Re:I haven't... (Score:3, Interesting)
But waiting in traffic is a waste of time.
Traffic will not vanish just because people can fly in three dimensions. Without auto-drive, there will still be a clear need for channeled traffic to avoid collisions between people just flying off in any direction. It won't be a free for all unless you really do want cars dropping out of the sky on a daily basis.
With auto-drive, many traffic jams can be made to vanish. Most congestion is the result of pressure waves from human drivers starting, stopping, refusing to let other people over, gawking at unnecessary accidents, etc. Universal, intelligent driving could eliminate stop-and-go traffic entirely and reduce slow-downs immensely.
I'm hoping it will be practical to park such vehicles in the sun and be coated with solar panels so as to mostly charge themselves between commuting. The top of buildings would make great parking spots (if reinforced). I realize, though, that flying takes a lot of energy.
Flying takes a LOT more energy than driving, and we don't even have practical solar family cars yet. Most prototype flying cars we've seen only carry 1-2 people (no cargo) and get mileage on par with a mediocre 4-person sedan. Even 2D, land-based solar cars are a fantasy unless we get major advances in solar cell efficiency.
Cars are resource inefficient (Score:3, Interesting)
Cars are expensive to build (in matter of resources). Cars are not very energy efficient only a fraction of the energy is used for motion the rest converted into heat. Furthermore a cars weight is approx 1.5 t to 2 t (1500-2000kg) and these 1500 kg are used to move around 80-150 kg. On top of that, the average speed of a car in a city is 15-25 km/h (depends on the study) which also achievable with a bike. Furthermore cars tend to stay unused most of their time. For example people drive to their job in the morning 1-2 hours and the same time back, which accumulates to 4 hours. And the other 20 hours a day they are parked somewhere. Most people have a garage at home for the car and at work there is also a parking lot and you need a lot of roads for them. This results in an average use of land area in a city of 50% for cars. The rest is for parks, houses, railroads, planes etc.
As we are going to run out of resources (oil, lithium, copper, and many more) it might be sensible to develop a more resource efficient people mover and if possible a way to reduce the need of using public transportation systems. For example: Many bankers and traders use their car to get to the city then they use an elevator to get to their office. While the boss is on level 12 the other are on level 10 and normally they do not see each other in person for days. Instead they use this awkward piece of equipment called phone to communicate. So why have all these people to use any transportation device to get from the suburbs to the city center when they easily could just stay there and work in distributed offices just together with their coworkers. And definitely outside the city center. And they could still talk to the boss on phone. Ok nobody would need bank towers anymore. But think of it. No bank towers no fear from terrorists in planes.
But instead of being reasonable we build flying cars for the troops. So they can fight abroad for ... what was it again? Never mind.
Re:Flying Cars Energy Hogs By Nature (Score:2, Interesting)
The rotor gets spun up to high revs with heavy counterweights at either end whilst on the ground, then the power is disconnected and transferred to the rear propellor. Increasing the collective sharply on the main rotor causes a jump takeoff and the rotor acts as a wing at cruising speed. Neat!
When the technology matures, this could be a very common mode of transit as they're apparently very easy to fly, but getting costs down to 'flying car' level would be tricky as they look like being half a million a piece.