374 Ë 10 HTS Maglev launch technology
Tab. 10.1:Total levitation forces of four HTS Maglev devices on No. 3 PMG [17].
Levitation gap (mm) FCH 20 mm (N) FCH 30 mm (N) FCH 40 mm (N) ZFC (N)
20 73 213 3.8 506
15 230 422 534 743
10 506 743 866 1097
5 939 1191 1322 1540To increase mechanical impact strength and decrease size and weight, both the
launch vehicle and the low-temperature device should be formed as a whole. The low-
temperature adiabatic device is a part of the entire launch vehicle. To increase dyna-
mic strength, no liquid nitrogen cooling is used. There is no liquid nitrogen vessel,
only a tube in the vehicle for external precooling with liquid nitrogen. The shape of
the tube is determined by the application requirements. The liquid nitrogen flows into
the adiabatic device through a tube before the experiment. The liquid nitrogen flow is
stopped when the temperature of the YBCO bulk reaches 77 K.
The launch vehicle includes four HTS Maglev devices. Each HTS Maglev device is
composed of 16 YBCO bulks of diameter 30 mm, insulation materials, and a cooling
tube. In order to increase the mechanical impact and the dynamic strength, some
special designs are used.
Levitation forces and guidance forces are measured by a self-developed HTS
Maglev measurement system SCML-02 [19]. (see Section 5.3). The total levitation forces
of four HTS Maglev devices on the No. 3 PMG (similar to the launch PMG) are listed in
Tab. 10.1. The levitation gap is the distance between top surface of PMG and bottom
surface of YBCO bulk. In the HTS Maglev launch test vehicle, the net levitation gap
includes an insulation thickness of about 3–5 mm. The total levitation forces at the
levitation gap of 15 mm are 422 N at the field cooling height (FCH) of 30 mm and 743 N
at the zero field cooling height (ZFC). The total levitation forces at the levitation gap
of 10 mm are 743 N at FCH of 30 mm and 1097 N at ZFC.
The total guidance forces, at FCH of 35 mm, are 66 N at a levitation gap of 15 mm
and 86 N at a levitation gap of 10 mm. The above total levitation forces and guidance
forces of the HTS Maglev launch test vehicle satisfy the design specification for a
levitation force of 500–600 N and the guidance force of 60 N, which indicates the
design validity of the HTS Maglev launch system. Research results of quasi-static HTS
on PMG in the past several years provide strong technical support for the development
of the HTS Maglev launch system.
The launch vehicle of liquid nitrogen-free or solid-state nitrogen is a good method.
The method merit is to eliminate fluctuation of liquid nitrogen when the launch
vehicle moves. This fluctuation will seriously affect the stability of launch vehicle. The
solid-state nitrogen can be acquired by pumping air to reduce the pressure within the
cryostat of launch body.