rick@cs.arizona.edu (Rick Schlichting) (06/07/91)
[Dr. David Kahaner is a numerical analyst visiting Japan for two-years
under the auspices of the Office of Naval Research-Asia (ONR/Asia).
The following is the professional opinion of David Kahaner and in no
way has the blessing of the US Government or any agency of it. All
information is dated and of limited life time. This disclaimer should
be noted on ANY attribution.]
[Copies of previous reports written by Kahaner can be obtained from
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To: Distribution
From: David K. Kahaner, ONR Asia [kahaner@xroads.cc.u-tokyo.ac.jp]
Re: SEMP Ship and Spaceplanes
6 June 1991
ABSTRACT. A brief description of the Superconducting Electromagnetic
Propulsion Ship (SEMP) and National Aerospace Lab's concept for a
Spaceplane. From Japan External Trade Organization, Machinery and Tech
Dept, Tokyo, New Tech Japan, Vol 19#1 (April 1991).
SUPERCONDUCTING ELECTROMAGNETIC PROPULSION SHIP
Construction of the hull of Yamato 1, the superconducting
electromagnetic propulsion (SEMP) ship has been completed at the Kobe
Shipyard & Engine Works of Mitsubishi Heavy Industries, Ltd.
The SEMP ship is a new type of futuristic ship, propelled by
electromagnetic force instead of screw propellers. Superconducting
electromagnets installed inboard (or outboard) develop a strong magnetic
field in the surrounding seawater, and current is fed through seawater to
cross the magnetic field. The interaction between magnetic field and
current generates electromagnetic force to propel the ship.
The SEMP system is theoretically more suitable for high-speed
seacraft than conventional screw propellers. With no rotating parts, the
SEMP thruster could be easy to maintain and free from noise and
vibration. When the electromagnetic field intensity is uniform, the
thrust is always proportional to the electric current intensity,
facilitating ship speed control.
Powerful electromagnets are essential to create such a magnetic
field and are the key to the SEMP system. Research and experiments for
SEMP system should contribute to applications in superconductivity, and
intensive SEMP R&D is underway in Western and other countries.
In Japan, R&D has been undertaken by the Ship & Ocean Foundation
since 1985, using researchers from industry, government, and
universities. The ultimate goal of the project is to build a testcraft
and to demonstrate through sea trials that SEMP is applicable to ship
propulsion. Through theoretical studies, a 2.6-m long self-propelling
model ship was tested in a water tank and its feasibility was confirmed
in July 1988. Based on the test results, the testcraft Yamato 1 has been
under construction since November 1989.
The Yamato 1 has an overall length of about 30m, breadth of about
10m, with 185t displacement, maximum speed of 15 km/h and will have ten
crew members. The hull is made of aluminum alloy, and the bow is covered
with a transparent synthetic resin to provide a wide and clear view. The
propulsion system is an internal magnetic field system that generates a
magnetic field in seawater passing through ducts running from bow to
stern. An external magnetic field system for creating a magnetic field
in the seawater surrounding hull is also possible, but its defect is
attracting nearby metallic objects.
The propulsion system essentially consists of superconducting
magnets for creating a powerful magnetic field in the duct seawater, a
compact helium freezer for maintaining these magnets at cryogenic
temperature (-269 xC), a power generation system for passing a current,
and ancillary equipment such as electrodes. The superconducting magnets
are arranged concentrically on 6 sets of dipole coils to intensify the
magnetic field inside the duct and to minimize field leakage outside, and
are accommodated inside a single cryostat. At the start of a Yamato 1
voyage, a ground station will be used to create the initial
superconducting state. The station has a large helium liquefier for
cooling magnets to cryogenic temperature and electric source for
magnetizing.
Yamato 1 will be equipped with two thrusters, one manufactured by
Mitsubishi Heavy Industries, Ltd. and the other by Toshiba Corp. The
helium cryogenic system for the superconducting electromagnets is made by
Kobe Steel, Ltd. After the two SEMP thrusters are installed, Yamato 1
will begin sea trials in August 1991 at Kobe Port.
*Ship & Ocean Foundation
1-15-16, Toranomon, Minato-ku, Tokyo 105
Tel: +81-3-3502-2371
Fax: +81-3-3502-2033
SPACEPLANE CONCEPT STUDY
The National Aerospace Laboratory has made a concept study of the
spaceplane which may become the space transportation system in the 21st
century. According to this concept, the spaceplane is powered by a
hypersonic airbreathing propulsion system based on the liquid air cycle
engine (LACE) and SCRAM jet engine. It is planned to conduct research to
develop the basic technology and to participate in the Spaceplane Project
aimed at a commercial spaceplane by the early part of the 21st century.
The spaceplane is viewed as potentially replacing conventional
rocket based space transportation systems, both manned and unmanned.
Space exploration is now expanding toward manned planetary exploration
and is now developing advanced and diversified use of space beyond earth
orbits. As the earth to space transport in this new age, the spaceplane
is now regarded as an important part of global space infrastructure. One
of the basic concepts of future manned space transportation systems is
the development of separate freighter rockets whose basic function is to
transport large quantities of cargo efficiently at low cost. The basic
concept of the spaceplane has received useful information from the
development and operation of the U.S. space shuttle. In the space
shuttle system, limitations concerning operational costs, the turnaround
time (the period between landing and the next launching), the flexibility
of operation, etc., have been highlighted for improvement.
The spaceplane will be a horizontal take-off and landing reusable
manned space shuttle, combining the functions of an aircraft, a space
transporter and an orbital spaceship. The spaceplane will make a
horizontal take-off from a runway, just like a conventional airplane,
then accelerate and gain altitude. After passing the limit of the
atmosphere at hypersonic speed, it will continue to accelerate and gain
altitude using a rocket until it reaches the velocity (7.9 km/s) required
to enter orbit. Once in orbit, it will rendezvous and dock with a space
station, etc., which will be the base for manned activities in space, to
replace personnel and provide support facilities. After the mission has
been completed, it will re-enter the atmosphere, and land on a runway
just like an airplane.
The features of the spaceplane such as reuse, horizontal take-off
and landing, and an air-breathing engine system are exactly the same
concepts as in an airplane. However, present airplanes can reach
altitudes of only 30 km and speeds of Mach 3. The spaceplane requires an
operational envelope which is higher by one order of magnitude. To build
such a spaceplane, various technological breakthroughs are necessary.
Especially important is the development of an air-breathing engine with a
high specific thrust and engine operation performance (up to highest
speed of perhaps Mach 20), possibly using a SCRAM jet engine, with
innovations in ultralight and high heat resistant structural and material
engineering.
The National Aerospace Laboratory produced this new concept
considering that the spaceplane with a three-stage system involving
turbojet, SCRAM jet and rocket engine would make the vehicle too heavy for
practical purposes. The laboratory decided to work on a combined
propulsion system concept based on the LACE engine and SCRAM jet engine
being developed by Mitsubishi Heavy Industries.
In the LACE system, air is liquefied and pressurized with a
turbopump for combustion. Fueling with slush hydrogen compensates for
the low density and cooling of liquid hydrogen. Slush hydrogen is 16%
more dense and has 18% more cooling capability due to heat of fusion than
liquid hydrogen. The tank volume and the gross weight are reduced and
the specific impulses of LACE increased by effective air liquefaction
capability. The SCRAM/LACE propulsion system using slush hydrogen is a
potentially promising concept for a spaceplane and integrated aerodynamic
design. Design for the SCRAM/LACE propulsion system such as the
forebody/intake/afterbody is underway.
Under the existing plan, the vehicle will accelerate to Mach 5 with
the LACE engine up to an altitude of 20 km, then switch over to the SCRAM
jet propulsion for cruising at speeds of Mach 20 to an altitude of 50 km.
Beyond this, the LACE engine will be restarted for the flight into low
earth orbit.
When a speed of Mach 20 is attained with the SCRAM jet engine, the
ratio of fuel weight to total spaceplane weight will be about 68%. Since
the LACE engine itself is light, the spaceplane based on this concept
appears highly feasible.
*National Aerospace Laboratory, the Science and Technology Agency
7-44-1, Higashi-machi, Shindaiji, Chofu City, Tokyo 182
Tel: +81-422-47-5911
Fax: +81-422-49-8813
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