Space Systems Fundamentals

Professional Development Short Course On:

Space Systems Fundamentals

Instructor:
Dr. Mike Gruntman

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349 Berkshire Drive • Riva, Maryland 21140
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NEW! May 18-21, 2009
Albuquerque, New Mexico
June 22-25, 2009
Beltsville, Maryland
$1590 (9:00am - 4:30pm)
quot;Register 3 or More & Receive $10000 each
Summary Off The Course Tuition.quot;
This four-day course provides an overview of the
fundamentals of concepts and technologies of modern
spacecraft systems design. Satellite system and
mission design is an essentially interdisciplinary sport
that combines engineering, science, and external Course Outline
phenomena. We will concentrate on scientific and 1. Space Missions And Applications. Science,
engineering foundations of spacecraft systems and exploration, commercial, national security. Customers.
interactions among various subsystems. Examples 2. Space Environment And Spacecraft
show how to quantitatively estimate various mission Interaction. Universe, galaxy, solar system.
elements (such as velocity increments) and conditions Coordinate systems. Time. Solar cycle. Plasma.
(equilibrium temperature) and how to size major Geomagnetic field. Atmosphere, ionosphere,
spacecraft subsystems (propellant, antennas, magnetosphere. Atmospheric drag. Atomic oxygen.
transmitters, solar arrays, batteries). Real examples Radiation belts and shielding.
are used to permit an understanding of the systems 3. Orbital Mechanics And Mission Design. Motion
selection and trade-off issues in the design process. in gravitational field. Elliptic orbit. Classical orbit
The fundamentals of subsystem technologies provide elements. Two-line element format. Hohmann transfer.
an indispensable basis for system engineering. The Delta-V requirements. Launch sites. Launch to
basic nomenclature, vocabulary, and concepts will geostationary orbit. Orbit perturbations. Key orbits:
make it possible to converse with understanding with geostationary, sun-synchronous, Molniya.
subsystem specialists. 4. Space Mission Geometry. Satellite horizon,
The course is designed for engineers and managers ground track, swath. Repeating orbits.
who are involved in planning, designing, building, 5. Spacecraft And Mission Design Overview.
launching, and operating space systems and Mission design basics. Life cycle of the mission.
spacecraft subsystems and components. The Reviews. Requirements. Technology readiness levels.
extensive set of course notes provide a concise Systems engineering.
reference for understanding, designing, and operating 6. Mission Support. Ground stations. Deep
modern spacecraft. The course will appeal to engineers Space Network (DSN). STDN. SGLS. Space Laser
and managers of diverse background and varying Ranging (SLR). TDRSS.
levels of experience. 7. Attitude Determination And Control.
Spacecraft attitude. Angular momentum. Environmental
Instructor disturbance torques. Attitude sensors. Attitude control
techniques (configurations). Spin axis precession.
Dr. Mike Gruntman is Professor of Astronautics at Reaction wheel analysis.
the University of Southern California. He is a specialist 8. Spacecraft Propulsion. Propulsion
in astronautics, space technology, sensors, and space requirements. Fundamentals of propulsion: thrust,
physics. Gruntman participates in several theoretical specific impulse, total impulse. Rocket dynamics:
and experimental programs in space science and rocket equation. Staging. Nozzles. Liquid propulsion
space technology, including space missions. He systems. Solid propulsion systems. Thrust vector
authored and co-authored more 200 publications in control. Electric propulsion.
various areas of astronautics, space physics, and 9. Launch Systems. Launch issues. Atlas and
instrumentation. Delta launch families. Acoustic environment. Launch
system example: Delta II.
What You Will Learn 10. Space Communications. Communications
• Common space mission and spacecraft bus basics. Electromagnetic waves. Decibel language.
configurations, requirements, and constraints. Antennas. Antenna gain. TWTA and SSA. Noise. Bit
rate. Communication link design. Modulation
• Common orbits. techniques. Bit error rate.
• Fundamentals of spacecraft subsystems and their 11. Spacecraft Power Systems. Spacecraft power
interactions. system elements. Orbital effects. Photovoltaic systems
• How to calculate velocity increments for typical (solar cells and arrays). Radioisotope thermal
orbital maneuvers. generators (RTG). Batteries. Sizing power systems.
• How to calculate required amount of propellant. 12. Thermal Control. Environmental loads.
• How to design communications link.. Blackbody concept. Planck and Stefan-Boltzmann
• How to size solar arrays and batteries. laws. Passive thermal control. Coatings. Active thermal
control. Heat pipes.
• How to determine spacecraft temperature.
60 – Vol. 97 Register online at www.ATIcourses.com or call ATI at 888.501.2100 or 410.956.8805

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Mike Gruntman Space Systems Fundamentals – Part 02. Universe. … Coordinate systems

Coordinate Systems

Coordinate systems play an
exceptionally important role in
exploration of space. They
provide the means to describe
complicated motions of celestial
bodies and spacecraft.

The most commonly used
coordinate system in science and
engineering is the Cartesian
coordinate system formed by
three orthogonal (perpendicular
to each other) vectors x,y,z. The
coordinate system that is used
In the spherical coordinate system, one
most often in space (and in
describes a position of a point by a distance
astronomy as well) is the
from the center of coordinates and two angles
spherical coordinate system.
between the direction to the point and two
coordinate-system-specific reference vectors.
2006 by Mike Gruntman 2006_06_MG_SSF_Part_02 13/20


Coordinate Systems
• Reference vectors
reference vector selection determines
the reference plane (normal to the
vector)
• Center associated with natural phenomena
Depending on (provided by nature)
application, the center of • rotation of the earth about its axis
the coordinate system is defines the equatorial plane
selected in such a way • motion of the earth around the sun
as to simplify the
defines the ecliptic plane
description of particle
(spacecraft) motion: assumed fixed in inertial space
geocentric • in reality, precession
heliocentric reference vectors are preferred to be
perpendicular to each other
planetocentric
• how do we define the second
center of galaxy
vector?
….



Ecliptic
and
Equatorial
Planes

• The plane, which contains the earth’s orbit around the sun, is called the ecliptic plane.
Obviously, the sun is in this plane. The axis of the earth’s rotation around the sun (and
correspondingly the ecliptic plane) is fixed in inertial space (except for small precession).
• An angle between the orbital plane of a planet and the ecliptic plane is called the
inclination of the orbital plane. The orbits of the planets are close to the ecliptic plane,
except those of Mercury and especially Pluto.
• The Earth rotates about its axis (which defines the South-North direction). This axis of
rotation is fixed in inertial space (except for small precession) and its direction does not
change as earth moves around the sun.
• The axis of rotation is not perpendicular (normal) to the ecliptic plane; the angle between
the axis of earth’s rotation and direction perpendicular to the ecliptic plane is 23.5 . This
inclination of the axis is the most important factor “responsible” for the seasons.



Vernal Equinox Vector



Vernal
Equinox
Vector

• The vernal equinox is a reference vector to establish longitude in both celestial and
heliocentric systems of coordinates.
• There are two equinoxes each year, in the spring and in the fall. At equinox, earth is
located at the intersection line of the equatorial and ecliptic planes. The equinox in the
spring (around March 21) is called the vernal equinox; the equinox in the fall – the
autumnal equinox.
• The direction from the center of mass of the Earth to the center of the sun at the vernal
equinox is the reference vector (the vernal equinox vector) to determine longitude.
• The vernal equinox was first established thousands of years ago. At that time the vernal
equinox vector passed through constellation of Aries (The Ram). The astronomical sign
of the Ram, , is still used for the vernal equinox vector although over the years the
vector moved to Pisces (The Fishes).
• The equinox vector precession rate is 0.014 degrees per year …. Why does it happen?


Coordinate Systems
• Geocentric Celestial
For a spacecraft orbiting the Earth, it would be convenient to use the
system of coordinate with the center at the Earth’s center and using the
Earth’s equator as a reference plane. Such a coordinate system is called
the geocentric system of coordinates (see figure). The equatorial plane is
the reference plane and the X-axis is the vernal equinox vector.
• Heliocentric
For a spacecraft traveling from one planet to another, say from Earth to
Jupiter, it would be convenient to place the center of the coordinate system
at the Sun and use the ecliptic plane as a reference plane. Such a
coordinate system is called the heliocentric system of coordinates. The
equatorial plane is inclined at an angle 23.5 with respect to the ecliptic.
• Galactic
For determining position of stars belonging to our galaxy, it would be
convenient to use the galactic plane as a reference plane. Such a
coordinate system is called the galactic system of coordinates.
• Space missions typically require use of various systems of coordinates



Time
Apparent Solar Time Mean solar time
• One day is determined as an • This is the time that you have on your
interval between two successive watch.
high noons (two successive solar • It assumes a circular orbit of the Earth,
transits across a local meridian). the spin axis normal to the ecliptic
The problem is that all days are plane, no axis-wobbling, etc.
slightly different because • A mean solar day is equal to exactly
Earth’s orbit is not exactly 24 hours or 1440 minutes or
circular 86,400 seconds
Earth rotates around the Sun Universal Time
Earth rotates about its axis
• The mean solar time at Greenwich
the spin axis is not normal to (England) is called the Universal Time
the ecliptic plane (UT).
Earth’s axis slightly wobbles • Scientific data obtained from
• All these effects are small and spacecraft are very often time-tagged
predictable. So it is possible to using the UT system.
build a time scale based on the
mean motion of the Earth relative
the Sun, mean solar time.



Sidereal Time

• In this time scale, the motion of the Earth relative to the stars determines the
time. A sidereal day is slightly different from the mean solar day.
This difference is illustrated in figure.
• A mean solar day = 1.0027379 mean sidereal day.
• 1 sidereal day = 23 hr 56 min 4.09 sec
• Spacecraft in geostationary orbit (GEO)


Space Systems Fundamentals

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