10.3 Preliminary research on HTS Maglev launch technology Ë 371mechanical and dynamic analyses of a projectile in a closed-ring vacuum pipe REL
system [7]. The final calculation results indicated the muzzle velocity could achieve
10 km/s. Hull proposed a REL launch system based on LTS magnets [8, 9]. This LTS
REL system used Nb-Ti wires for the support apparatus and Nb 3 Sn to make the pro-
jectile. The large magnetic forces between the Nb 3 Sn projectile and the Nb-Ti support
apparatus could maintain stable suspension and counteract the huge centrifugal force
of the projectile at very high speed.
Launch Point Technologies, Inc., promoted a commercial superconductive REL
system, which had the same basic principles as the LTS REL system proposed by Hull,
called the “Launch Ring” [10]. The biggest problem of the Launch Ring system was
also the huge centrifugal force of projectile under high speed. The Launch Ring system
consisted of a rail ring of large diameter to reduce the centrifugal force. The larger
the ring diameter, the smaller the required radial suspension forces to compensate
for the centrifugal force. For example, a projectile of 200-kg mass needs 40 MN of
radial suspension forces to compensate for the centrifugal force with a 1-km launch
ring diameter, but only 5 MN when the launch ring diameter is 8 km. The final velocity
was designed to be 10 km/s, which included an orbital velocity of 7.8 km/s with a
margin velocity of 2.2 km/s to offset various launch losses. To achieve the final muzzle
velocity, a segmented control linear synchronous motor was introduced, which inclu-
ded multiple motor sleds that could be accelerated simultaneously. According to the
calculation, a 20-MW linear motor with 100 sleds, each sled 250 m long, could launch
50 tons per hour into orbit with the 8-km launch ring diameter. Compared with coil
gun and rail gun systems, the maximal required power for the Launch Ring system is
much smaller. According to the economic analyses by Launch Point Technologies, if
the Launch Ring system can shoot 30,000 times per year, the cost of a 1-kg payload is
41 dollars, which is much lower than the cost of a rocket or space shuttle launch.
10.3 Preliminary research on HTS Maglev launch technology
After the successive development of first man-loading HTS vehicle [11]. (see Chapter 6),
the application of the HTS Maglev system to electromagnetic launch was activated
quickly in the Applied Superconductivity Laboratory (ASCLab), SWJTU. There are
many parameters that needed to be investigated clearly and carefully for the practical
development of a HTS Maglev launch system.
The loading capacity of the HTS Maglev launch system is the most important
parameter, which decides the basic operation performance of a launch system. In the
previous research on HTS Maglev vehicles, it was found that the levitation force re-
laxation increased with the increase in reloading. He investigated the levitation force
relaxation of bulks YBCO under different loads [12]. From the experimental results, it
was clear that the normalized relaxation rate of the levitation forces increased with
the increase in load.