IEEE Electrification Magazine - December 2013 - 69

Table 2. NaSa's technology goals for future subsonic vehicles.

Corners of the
Trade Space

N+1 (2015)
Technology Benefits
Relative to a Single Aisle
Reference Configuration

N+2 (2020)
Technology Benefits Relative to
a Large Twin Aisle Reference
Configuration

N+3 (2025)
Technology Benefits

Noise

−32 dB

−42 dB

−71 dB

LTO nitrogen oxide
emissions

−60%

−75%

Better than −75%

Performance
aircraft fuel burn

−33%

−50%

Better than −70%

Performance
field length

−33%

−50%

Exploit metroplex concepts*

*Concepts that enable optimal use of runways at multiple airports within the metropolitan areas. (Used with permission from Luongo et al.)

lightweight, high-power converters are designed and manufactured for various applications.
the aerospace industry is facing challenges similar to
those of the automotive industry in terms of improving
emissions, fuel economy, and cost. another similarity is the
move toward replacing mechanical and pneumatic systems
with electrical systems, thus transitioning toward more
electric architectures. the advisory council for aeronautics
research in Europe has set several
goals to be achieved by 2020 for air
transportation. these include a 50%
reduction of co2 emissions through a
drastic reduction of fuel consumption;
an 80% reduction of nitrogen oxide
emissions; a 50% reduction of external
noise; and a green design, manufacturing, maintenance, and disposal product
life cycle. Most of these goals could be
achieved through more electrification
of air transportation. the electrical
power being used by both civil and military aircrafts is also growing. passenger
aircrafts, such as the Boeing 787 and
airbus 380, are employing many new
electrical technologies. For example,
the Boeing 787 employs a bleedless
environmental control system. these
loads create a substantial increase in
the total electrical power drawn from
the aircraft engine-driven generators. For example, the
power generation in the Boeing 747 is 480 kVa, whereas the
power generation in the more recent a380 aircraft is 840
kVa, and that of the the Boeing 787 is 1,450 kVa.
the sustainability of the aviation industry requires
aircraft that are significantly quieter and more fuel
efficient than today's fleet. achieving this will require
revolutionary new concepts, in particular, for electric

propulsion. superconducting machines with cryogenic
power electronics offer a viable path to achieve the
power densities needed in electric propulsion airborne
applications. For example, nasa's technology goals for
future-generation aircraft are shown in table 2. to
achieve this goal, nasa is proposing to develop a
blended wing body aircraft with a turboelectric distributed propulsion system. the system consists of at
least two turbine-driven generators mounted at the tip of the
wings. the outputs of the generators are rectified and connected to
a number of power converters.
Each power converter converts the
input dc to variable frequency and
variable voltage ac to power the
electric motors that drive the propulsors as shown in Figure 3. the
propulsion system provides the
required propulsive power for the
aircraft and also assists in aircraft
yaw control through differential
thrust. to achieve maximum efficiency and reduce the weight,
nasa is proposing the use of a
superconducting and cryogenic
electrical system with dc distribution consisting of a superconducting generators and cryogenically
cooled power converters.
a few recent studies have focused on faster and more
efficient rail transportation systems since the traditional
railway propulsion systems have mechanical limitations
and maintenance issues due to the dependence on friction
between the wheels and railways. in particular, the maintenance of the traditional systems is quite expensive and
time consuming, thus leading the researchers to look for

Superconducting
machines with
cryogenic power
electronics offer
a viable path to
achieve the power
densities needed
in electric
propulsion airborne
applications.

IEEE Electrific ation Magazine / d ec em be r 2 0 1 3

Table of Contents for the Digital Edition of IEEE Electrification Magazine - December 2013