Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.cosmoworld.ru/spaceencyclopedia/publications/el_motor%2003engl.doc Дата изменения: Mon Mar 7 13:15:36 2005 Дата индексирования: Tue Oct 2 06:02:28 2012 Кодировка: Поисковые слова: ngc 3372

Introduction

The suggested invention relates to attitude control system of a
spacecraft. This system provides angle positioning of any spacecraft. The
system allows pointing of a spacecraft to any object on the Earth or in
space and spin control as well.
Attitude control system generates torque 2M, which is applied to the
spacecraft structure (see Fig. 1 and 2). Angle position of the spacecraft
begins to change. This system is indispensable part of any spacecraft.


























Fig.1 Applying of torque 2M (X - axis) to a spacecraft in reference to XYZ
coordinate system.






















Fig.2 Applying of torque 2M (X - axis) to the spacecraft in reference to Y-
Z plane.

Spacecraft's attitude control systems can be classified into two
types.

Systems with interaction with ambient. Here, for instance, we can put
systems, which interact with magnetic field of any planet (principle of a
compass needle), systems, which interact with solar rays (pressure of solar
irradiation). But those systems are not universal. First of all because of
necessity some special conditions (it can not work without any external
magnetic field, or in shadow). In the second those systems can generate
very small torque moment. That is why those systems can not be taken into
account.

Systems without interaction with ambient (Systems with jet engines)
Here, for instance, we can put systems, which can generate torque because
of jettisoning any particles or gas. Those systems can generate
considerable torque moment. But those systems are to be resupplied from the
Earth. The propellant, oxidant or gas tanks sooner or later are empty.
Sometimes the systems are accompanied by gyrodines (damping gyro) in order
to avoid frequent switching on of the system and make the attitude control
process smoother. gyrodines play a buffer role, accumulating any externally
applied moments within a predetermined range, but some time later jet
engines are to be started in order to unload the gyrodines otherwise
gyrodines gimbal axis can rich a stop interrupting the control. Systems
with jet engines are the widest spread. Other subtypes of the jet engines
system are arc-jets engine system, electrostatic jets engine system or
similar, which are not taken into account because of small moment value and
complexity. Virtually the same principle of jettisoning any particles or
gas is used in this type as well.

So first of all let's outline an "ideal system" we would like to have:
1. Independence of the outer conditions (any external sources of
radiation are absent),
2. Considerable moments value,
3. Independence of resupplying from the Earth (this main task is not
decided till now),
4. Any substance plume while the system work must be excluded,
5. High temperatures must be excluded,
6. Moving parts must be excluded,
7. High pressures must be excluded,
8. High voltages must be excluded,

The suggested attitude control system
The suggested attitude control system (which is described below)
corresponds to all points of the "ideal system". The main element of the
suggested attitude control system is an electrical motor, which main
feature is absents of a stator. This electrical motor satisfies all the
points of the "ideal system". A remote power controller satisfies all the
points as well because it is usual solid state electronic device, which
controls current through the electrical motor. So the suggested system
meets all points of the "ideal system" a usual system with jet engines can
meet points 1 and 2 only.


Block diagram of an attitude control system on the jet engines base
and an attitude control system on the suggested electric motors base are
shown in Fig. 3 and Fig. 4 in order to be compared.





















Fig. 3 Block diagram of an attitude control system on a jet engines base.




















Fig. 4. Block diagram of an attitude control system on the suggested
electric motors base.

Dotted line in Fig. 3 and Fig. 4 outlines an attitude control system.


So, comparing Fig. 4 and Fig. 3 you can see advantages of the suggested
system.

Advantages of the Suggested system over existing systems are indicated
in Table 1:

Table 1
|Performance |existing systems |Suggested system |
|reliability |Relatively low (because of high |Exclusively high (because |
| |temperatures, (high voltages for|high temperatures, high |
| |such subtypes of jet system as |voltages, high pressures |
| |arc-jet engine, electrostatic |and moving parts are |
| |jet engine or similar), high |absent) |
| |pressures and moving parts)) | |
|duration of |Depends on the fuel, Oxidant |Unlimited (within the |
|torque |mass and velocity of its |spacecraft life time) |
|generating |consumption by jet engines | |
|reactive |Present for combined system (jet|Absent |
|moment and its|engines + gyrodines) | |
|compensation | | |
|high |Propellant combustion generates |Absent |
|temperatures |high temperatures | |
|environment |Present because of the jet |Absent |
|polluting |engines plume | |
|Fuel and |Present |Absent |
|Oxidant store | | |
|torque |There is a single pulse of the |Generated torque depends on|
|adjustment |jet engines thrust. This pulse |electric current value and |
| |has a minimal duration with |duration of the current |
| |considerable tolerance. |passed to the electrical |
| |Decreasing of the generated |motor. Both values can be |
| |torque below this predetermined |easy adjusted very |
| |value is impossible. |precisely. |
|Check out of |Complicated. High temperatures, |Very simple because it is |
|the system |high pressures and moving parts |pure electrical equipment, |
| |generate hazard situations. |so it can be tested by |
| |Possible explosion of tanks, |standard electrical test |
| |test personnel poisoning by |devices. Hazard situations |
| |propellant and oxidant. |are absent. |
|manufacture |Complicated manufacturing |Simple. Manufacturing of |
| |(Propellant and Oxidant - |electrical equipment can be|
| |chemical industry, jet engines |concentrated in the only |
| |design - precision mechanical |place. |
| |engineering) and assembly. | |
|Redundancy |Redundancy can be achieved by |Simple. It is a system with|
| |installation of a redundant |distributed elements. A |
| |system, but it increases mass of|failure of a single element|
| |the system twice. |does not lead to a failure |
| | |of the system. |
|Maintenance |Refueling of the system, test of|Simple. (Electrical Built |
| |system pressurization, check out|in Test.) |
| |of valves, pipelines, pumps and | |
| |so on are complicated. | |
|material costs|High. High-grade steel, |Low. No expensive |
| |high-temperature steel, plenty |components are required. |
| |of metalworking operations, | |
| |expensive Propellant and Oxidant| |
| |manufacturing and storage. | |


Technical effect because of the suggested system maintenance:

. Increasing of a spacecraft life time,
. Increasing of reliability,
. Reduction of mass,
. Increasing of spacecraft stabilization and pointing accuracy (one
can adjust the applied torque with any degree of accuracy because
of precise electric power regulation),
. Simplifying of the system check out procedure.


Economical effects while the suggested system manufacturing:

. Reduction of manufacturing cycle (a simple system can be produced
faster),
. Absence of expensive components (High-grade steel, high-
temperature steel, propellant),
. Reduction of testing cycle (low voltage electrical equipment can
be checked out automatically, very quickly, without any special
precautions),
. Reduction of the test equipment cost (you should not check out
propellant and oxidant, tanks pressurization and so on),
. Protection of environment can be achieved easily because of
harmful and dangerous production (fuel + oxidant) absence.

Economical effect because of the suggested system maintenance:

. Absence of a spacecraft resupplying by fuel and oxidant (it is not
necessary to launch a cargo vehicle in order to restore fuel and
oxidant level in the tanks of the spacecraft, a control mission
center does not have an excessive work as well),
. Prolongation of any satellite life (it makes possible to use the
only satellite instead of two, three and more, because any
dependence and limitations connected with fuel consumption is
absent),
. Reducing of the check out cost (fast check out is possible because
of automatic test sequence execution),
. Contamination of environment by end product of fuel combustion is
absent (solar arrays surface is not contaminated, so the solar
arrays degradation is not observed because of this reason and it
is not necessary to exchange it for a new one). Illuminators and
optical surfaces are not contaminated.

Other features:

. Reduction of system mass and independence of propellant allows
easy planning of long term missions (Mars and other planet
exploration),
. It is possible to create artificial gravitation systems by means
of space vehicle rotation because it does not have any influence
on the fuel consumption.

Where this invention can be used

Any spacecraft has an attitude control system. So it is possible
implementation of the suggested system into any spacecraft (or satellite)
design. The main part of the system - electrical motor can be easy modified
(reconfigured) in order to meet any specific requirements of the spacecraft
design.
The market for offered attitude control system is unlimited owing to
its exclusive competitiveness caused by low cost of the system, extremely
high reliability and duration of operation of the system, unreachable for
usual systems.

Restrictions on the attitude control system manufacturing:
Statorless electric motor is the zest of the suggested attitude
control system. Mathematical model of the electric motor is a key element
for understanding of principles of electrical motor work. It is a tool for
designing any electrical motor as well. A description of key principal of
such a motor is available too in order to make understanding easy.
The engine can be designed for any specific spacecraft. It is the
simplest way to achieve an optimal parameters relation (mass of the
spacecraft - generated moment - power consumption - redundancy level).
Other components of the system can be chosen as standard components.
Any specific requirements to production shops are absent.
Manufacturing of the electrical motor and the system itself can be done in
electric and electronic production shops. Any specific training of the
production shop personnel is not necessary.

Performance of the suggested attitude control system:
For example: an attitude control system with the simplest design of
the electric motor can produce 10,5 Nm at 18 A current. Relatively to a
cylindrical spacecraft (see Fig. 1 and 2) with mass m=6800 kg and radius R
=1,4 m it means that complete turn over can be achieved for T = 89 s.
More complex versions of the attitude control system can produce 1000
Nm and more at the same current.


-----------------------

M



M



X



Z



Y


M

M


Y



Z


A spacecraft

An output regulator of the attitude control system

Electric Power supply

Power distribution system

Control system

Output regulators (jet engines)

Fuel tank

oxidant tank


Pipelines,
Valves,
Igniter system,
Pumps,
Flowmeters,
and so on

M

M

Electric Power supply

Power distribution system

Control system

Output regulators (electric motors)

M

M

Remote power controller

Attitude control system

Attitude control system

Remote power controller