92 Ë 4 Superconducting magnetic levitation
organized the National Maglev Initiative (NMI) [43, 44] to determine whether it should
actively encourage investment in Maglev. The NMI program in the USA was started
in 1990. The Government Maglev System Assessment Team operated from 1991 to
1993 as part of the NMI. The NMI’s principal tasks were to assess the technical and
economic viability of Maglev in the USA and to recommend the most appropriate
federal role for its development. It awarded four System Concept Definition (SCD)
contracts to teams led by Bechtel Corp., Foster-Miller, Inc., Grumman Aerospace Corp.
[45, 46], and Magneplane International, Inc., [47–49]. Based on comparison of the
High Speed Surface Transport of TGV in France and Transrapid-07 in Germany, all
four US Maglev concepts in the NMI program were LTS Maglev. The Grumman version
was EMS Maglev, but the other three schemes were EDS Maglev. The levitation gap of
Grumman’s EMS Maglev was 40 mm, 4 times as high as in Transrapid-07. The levitation
gaps of other three EDS Maglev schemes were greater than 40 mm.
Unlike discrete coil guideways of EDS Maglev in Japan, Magneplane’s was a
version of the conductive sheet guideway. This conducting sheet for levitation offered
potential advantages in construction cost and ride quality over discrete coil guide-
ways, but it had lower electromagnetic lift-to-drag ratios. Sheet guideways could have
a larger levitation gap capability. Superconducting magnet systems of comparable
weight to PM systems could provide at least three times the levitation gap [47].
The Foster-Miller [43] concept was an EDS similar to the Japanese high-speed
superconducting Maglev, but it had some additional features to improve potential per-
formance. The Foster-Miller concept was a vehicle tilting design that would allow it to
operate through curves faster than the Japanese system for the same level of passenger
comfort. The Bechtel [43] concept was a superconducting EDS system that used a novel
configuration of vehicle-mounted, flux-canceling magnets. The vehicle contained six
sets of eight superconducting magnets per side and straddled a concrete box-beam
guideway. Interaction between the vehicle magnets and a laminated aluminum ladder
on each guideway sidewall generated lift.
Numerous studies and development projects [43] have been completed in the
USA, but no commercial Maglev systems have been deployed. Powell and Danby [50],
the LTS Maglev inventors in the USA, presented a Maglev train for the 21st century.
Operating high-speed vehicles from one guideway to another and without having to
slow down the trains was to be achieved by an ultra-high-speed electronic switch.
The on-board superconducting quadrupole magnets would allow them to smoothly
transition, back and forth, between narrow-beam and planar guideways. In this way,
the vehicle would ride on the single guideway after leaving the station. Thus, the
Maglev system could reduce greatly the construction costs.
Studies and some experimental works for the EDS Maglev system using 10 levita-
tion superconducting magnets were started in Canada [51–53] in the early 1970s. A flat-
topped guideway was proposed to minimize ice and snow accumulation, and a new
technique was proposed for obtaining lateral guidance using interaction of 50 propul-
sion magnets with the edges of the levitation strips and with null flux loops overlaying