In the following article, a really interesting question is explored. The question is: Is there a better, more efficient way to launch airplanes?
If you think about how airplanes take off now, you can see the potential problem. The pilot positions the plane at the end of the runway, the pilot applies the plane’s brakes, the pilot ramps the engines up to maximum thrust (as well as maximum fuel consumption and noise), and then releases the brakes. The plane accelerates to flight speed, takes off, and continues under maximum thrust until it is at a safe altitude.
This launching technique uses a lot of fuel and also creates a lot of noise.
The technique proposed in the article looks remarkably different. An electric airplane flies in circles overhead at the end of a cable. The altitude of the circling airplane is 30,000 feet. The cable supplies power to the electric airplane and also is used to support a lifting system. When a plane needs to take off, it is attached to the cable and a winch system pulls it up to the altitude of the electric airplane. By the time the second plane reaches the altitude of the electric airplane, the second plane is already at its cruising altitude and has the same speed as the electric plane.
So we can examine this idea and see at least three significant advantages. First, the savings in jet fuel are obvious. No fuel is used to reach cruising altitude – a significant savings. Second, there are fewer emissions — there are probably carbon emissions at the power plant that’s supplying the electricity, but they are significantly less than from jet engines. Third, the noise around airports would be greatly diminished during takeoffs.
There are probably also a couple of disadvantages. First, there is a big problem in the event of a power failure, so something would have to be done to ensure that never happens. It is not an insurmountable problem – it is relatively easy to put backup generators in place. Having a 30,000 foot long moving cable in the air at an airport seems like it may present some safety problems. Looking at these two problems, neither appears to be a deal breaker.
It does cause you to think however. Is there a more efficient way to get airplanes off the runway?
- One idea that comes to mind is electric hub motors in the landing gear. Could they assist the takeoff and reduce fuel consumption?
- Could a catapult system like that used on an Aircraft Carrier be mounted on a runway?
The article also contains this tantalizing paragraph:
In 2008, NASA funded several teams to design aircraft with 70 percent lower fuel consumption and a 71-decibel reduction below current FAA noise standards. The teams were led by General Electric, M.I.T., Northrop Grumman and The Boeing Company. The Boeing team designed a hybrid electric aircraft to reduce noise and fuel consumption. The team’s report concluded that hybrid electric engine technology “is a clear winner, because it can potentially improve performance relative to all of the NASA goals.” The major limitation of electric aircraft continues to be the weight and cost of batteries. Current electric aircraft have low payloads and speeds due to limited battery power. The Chinese company, Yuneec, demonstrated its E430 electric aircraft in 2009. The single-seat aircraft flies with lithium batteries for up to three hours with a maximum take-off weight of 1034 lb. The light sport aircraft is promising, but has a maximum speed of just 150 km/h.
We discussed three of these designs in this blog post:
The discussion of hybrid airplane engines leads to this article:
However, the team has found that the SUGAR Volt concept (which adds an electric battery gas turbine hybrid propulsion system) can reduce fuel burn by greater than 70 percent and total energy use by 55 percent when battery energy is included. Moreover, the fuel burn reduction and the ‘greening’ of the electrical power grid can produce large reductions in emissions of life cycle CO2 and nitrous oxide. Hybrid electric propulsion also has the potential to shorten takeoff distance and reduce noise.
The SUGAR team’s report concludes that hybrid electric engine technology “is a clear winner, because it can potentially improve performance relative to all of the NASA goals.”
However, Bradley said, in order for the hybrid electric concept to be competitive, battery technology “needs to improve many, many times over what we have today. Battery technology is being worked around the world, especially in the auto and electronics industries. We need to leverage that work to see if we can get the improvement we need in an aviation compatible package.”
When thinking about that, could the airplane tow a long extension cord behind it during takeoff. The extension cord would supply power while the plane is accelerating on the runway and just shortly after takeoff and then detach automatically.
If nothing else, it makes you think. Here is one pure electric airplane: