Slashdot Mirror
The Future of Flight
Roland Piquepaille writes "With "High Times," the Economist delivers a very long and extremely well-documented article about the future of aviation during the next fifty years. It tells us about pilotless planes, with 32 countries currently developing more than 250 models of unmanned aerial vehicles (UAV), primarily for combat purposes. The article also looks at future civilian pilotless planes and at the future of personal aviation. But what captivated my attention in this article was the last part about future commercial supersonic and hypersonic (at least five times the speed of sound) planes. In particular, the Economist describes the HyperSoar. "The HyperSoar is a concept for a craft flying at ten times the speed of sound and able to reach any point on the globe within two hours." This overview contains more details and references about the HyperSoar which would fly from Los Angeles to New York in 35 minutes."
hmm, I thought High Times was a publication of a different sort...
But even with that fact HyperSoar which would fly from Los Angeles to New York in 35 minutes. How long would you have to wait at the airport to get on the plane?
Get Movie Posters
commercial airlines have an accident rate of 0.06 crashes per million hours of flying whereas the Northrop Grumman Global Hawk UAV used by the US military has 1600 crashes per million hours of flying. This shows that the UAVs have a long way to go before we can trust our lives to this tecnology.
Remarkably bad math. Escape velocity is closer to Mach 25.
Oh, and flying upside down doesn't have a magical affect on whether or not you escape or not.
Eclipse Aviation of Albuquerque, New Mexico have produced a Air taxi capable of carring 5 people upto 1500 Km, but for this to be widely adopted 'free flight' must first exist. This allows piolts to plot there own jouneys, cutting distances and utlising more airspace. 'free flight' relies on each aircraft having it's own computer that allows aircraft to avoid each other. For more information see this weeks (13/12/03) New Scientist p28-33.
There are more than just aerodynamic obstacles. How much fuel do your designs consume? What sort of load are they capable of carrying? I bet I can make ten different planes that fly from here to the moon in an hour, with no useful load and at a cost of four trillion per launch. Not to say that your designs aren't practical -- I'd just like to point out that designing airplanes is one third engineering and two thirds economics.
irb(main):001:0>
As an aerospace engineer, I'm always surprised about how many things we are supposed to achieve in the next so-many-years.
People, believe me: It is _not_ going to happen. Period.
Why not?
Well first of all, aerospace as an industry is extremely conservative. Despite it's high-tech image, the facts (and my experience) show differently. Look at the shape of aircrafts for example: Essentially unchanged since the 1930s. The fuselage-wing-tail concept is still the most popular, and all the research on blended wings, canards, double-fuselage, and other stuff people have made up, have not changed a thing (try to find the book by E. Torenbeek, you'll be amazed about how rich a phantasy some people have). That is because it simply is by far the most efficient concept: it's easy to stabilize, and you can put lots of people in it. Blended wings, for example, turn out to be too thin for people to fit in for, say, an aircraft for 100 people. Also, safety is easlier to achieve, and there's lots of room for cargo/luggage and fuel. Boeing's SST and Sonic Cruiser, and even the Concorde, did not fail without a reason. The A380, the "next generation aircraft", still has the same basic design as a DC-3 had 60 years ago. Another example is materials: Aluminum is still the primary construction material. It is _very_ slowly being replaced with composites and laminates (carbon, glass fibre/epoxy, GLARE). Aircraft manufactures can't sell an aircraft until it is absolutely proven that the new aircraft is safe and maintainable and has cheap Direct Operating Costs. So they all play safe and go with trusted concepts/materials. The A380 took about US$15_billion_ to develop. You don't go gable with such amounts. You play safe.
Then there's an economic reason. Profits for airliners are extremely low: 3-5% is not unusual. In fact, very few airlines have made a net profit over the past two decades. In the USA, airlines go bankrupt every 10 years, in Europe they would not survive without government support. Investing in airlines is high risk. This automatically means that investments in aircraft manufacturers is also quite risky. So actual research development of new technologies in the aerospace industry are very low, and usually government-sponsored, related to military applications, or conducted in universities or research institures. The "time to market" of any new technology in the aerospace industry has been estimated to be about 35 years.
This is already too long a story, I could go on for pages. But realy, this kind of views on the future just makes me laugh my pants off.
Before someone posts about how rockets are fuel-inefficient compared to other engines, I'd like to point out that it mostly depends on the cruise speed of the aircraft.
If the plane completes the flight in ten times less time than a conventional subsonic plane, then its engines are burning fuel for ten times less time as well.
Modern high-bypass turbofan engines have a specific fuel consumption (SFC) rate around 0.5 lb of fuel per lb of thrust per hour. Current liquid fuel rockets' SFC is around 10, and solid / hybrid rockets' SFC is around 5. But the concept of "pound of thrust" evolves with speed: for example, a reciprocating engine with a propeller will give you much more (approximately four times as much) pounds of thrust than the number of HP the engine develops, _at low speeds_. At 375 mph, you get one pound of thrust per HP. And beyond, you get much less. That's why high subsonic planes use turbofans and the slower planes still use propellers.
At supersonic speeds the fuel consumption per distance covered of a turbofan engine can grow as high as 3+, but that of a rocket engine does not grow with speed, so there's a given speed beyond which rockets are more efficient than turbofans.
Maybe we deserve this world ?
"HyperSoar's trajectory follows a skipping pattern. Passengers would feel 1.5 times the force of gravity at the bottom of each skip, and weightlessness out in space. The experience would be comparable to being on a swing, although HyperSoar's motion would be 100 times slower."
Anyone else thinking about investing their life savings into sick bag companies?
Airplanes are stable or unstable due to their roles.
Fighters are inherently unstable, to allow the radical combat sequences dictated by dogfighting. It's true some of the current fighters are unflyable without constant computer assisted tuning.
Large passenger jets ARE inherently stable. The use of computers to control the flight surfaces are dictated by demands for maximum fuel economy, which means constant re-adjustment of CG's, trim, and other parameters.
Nothing in their design prevents them from being flown on purely hydraulic controls in an emergency.
Actually, the energy cost for travel by flight is really no higher than for other transport methods. Consider a quick calculation:
A 747-400 has a range of about 8400 miles, and a fuel capacity of about 57,000 gallons. Multiply that by 410 seats, you get around 60 mpg per passenger. And Boeing's new 7E7 "Dreaminer" is touting much higher efficiency than any of their previous jets. Airbus is doing well too, with the new A380 and Rolls Royce Trent 900 engines. Fuel capacity of 82,000 gallons, range of 8000 miles, 555 seats. Thats around 55 mpg per passenger.
So those numbers are way better than the CAFE (Corporate Average Fuel Economy) standards in the US, currently 20.6 mpg I believe, not including the SUV's buzzing around the suburbs that aren't subject to those rules.
Hydrogen fuel cells would be great, but they're nowhere near production status for commercial transport flight.
I can't say I'm sorry at all that we don't have flying cars.
Seriously, the average goober has enough trouble dealing with two dimensions. Three is far too much for them to handle while they lean over the seats to yell at their kids while talking on the cell-phone with one hand while holding the map in the other.
I'm paranoid enough worrying about them while I'm driving. I don't want to worry about one of them dropping out of the sky onto my house.
And, even if you make the completely insane jump of reason that would let you believe that the average driver would be safe, there's always maintenance to deal with. The average aircraft spends as much, or more time in routine maintenance than in the air. Well-publicised errors notwithstanding, aircraft are some of the most meticulously maintained machines on earth. This, compared with my fellow car drivers, who are often seen driving with missing headlights, cruising at 75mph on temporary spares, belching blue smoke because they can't be bothered to remember to change the oil frequently, etc.
I can see some limited applications for flying cars, mostly in emergency services (ie: ambulances). However, for the general public? No thank you, it gives me the shudders just to think of it.