Samenvatting
Summary Introduction to Aerospace Engineering-II
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This summary explains the subject clearly and covers the entire course. Many explanatory graphs, tables and illustrations are added which make the subject a lot easier. I really recommend this summary, especially for those of you who don't have much time left to study for the test.
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Voorbeeld van de inhoud
AE1110-II Introduction to Aerospace Engineering-IIIntroduction to Aerospace
Engineering-II
AE1110-II
Delft University of Technology
1
, AE1110-II Introduction to Aerospace Engineering-II
Table of Contents
Introduction, heritage and trends.………………………………………………………………………………………………………3
Launch vehicles………………………………………………………….……………………………………………………………………….5
Satellite orbits………..…………………………………………………………………………………………………………………………..8
Rocket motion and launchers………….……………………………………………………………………………………………….16
Space environment…………………………………………………………………………………………………………………………..24
Ground systems and operations……………..………………………………………………………………………………………..31
Satellite and mission characteristics………………………….……………………………………………………………………..35
Spacecraft subsystems and configurations.………………………………………………………………………………………40
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, AE1110-II Introduction to Aerospace Engineering-II
Introduction, heritage and trends
Why do we go in space?
- We are curious
- It is challenging
- We have the necessary technology
- It stimulates technological innovations
- We can afford it
- It provides a unique environment
- It enables new applications
- We can do new business
- It provides access to new world
- It is there
What can we do in space?
- Observe the universe
- Observe and monitor Earth
- Experience and exploit weightlessness
- Perform science experiments
- Travel to new worlds
- Space tourism
- Make money
Important applications
- Space physics
- Space astronomy
- Telecommunication
- Navigation
- Meteorology
- Disaster monitoring
- Global change
- Micro-gravity research
- Solar system exploration
- Espionage and surveillance
- Space tourism
What are the challenges?
- To get there, stay there and return
- To do this in an affordable, efficient way
- To deal with a harsh and hostile environment
- To develop the technology
- To invent innovative applications
- To (remotely) operate the (sub)systems
- To deal with the unexpected
Enabling technologies
- Miniaturization of electronics
- Radio communication and radar technology
- Capability to build large light-weight structures
- Advanced heat-resistant materials
- Light-weight, powerful gas turbines and pumps
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, AE1110-II Introduction to Aerospace Engineering-II
- Liquid-propellant rocket engines
- Active guidance using gyroscopes
- Solar cells
- Heat engines
- Digital computers
- Life support systems
History
- 1571-1630: Johannes Kepler solves the mystery of celestial mechanics.
- 1642-1727: Sir Isaac Newton defines the physical principles of force, motion and gravitational
attraction.
- 1865: Jules Verne describes a virtual trip to the moon.
- 1903: Konstantin Tsiolkovsky publishes his theoretical study on rocket propulsion and multi-
stage rocket motion.
- 1920’s: Hermann Oberth pioneers the theoretical fundamentals of spaceflight.
- 1925: Walter Hohmann analyzes the method to perform interplanetary flight.
Rocket history
- 1920-1940: Robert Goddard launches first US liquid propellant rocket; Sergej Korolev does
the same in Sovjet Union.
- 1940-1945: Wernher von Braun develops first operational short-range missile (V2).
- 1950-1960: Sovjet Union and USA develop Intermediate Range and Intercontinental Range
Ballistic Missiles (IRBM’s & ICBM’s).
Spaceflight history
- 1957: launch of Sputnik I.
- 1958: launch of Explorer I.
- 1959: Luna 2 makes a hard landing on the moon.
- 1961: first manned satellite flight (Yuri Gagarin; Vostok I).
- 1962: first US manned satellite flight (John Glenn; Mercury).
- 1962: Mariner II to Venus.
- 1965: first EVA (Extra Vehicular Activity) by Aleksej Leonov; Voskhod 2.
- 1967: first launch of largest rocket ever (Saturn V).
- 1968: first European scientific satellite (ESRO II).
- 1969: first men on the Moon (Neil Armstrong and Buzz Aldrin; Apollo 11).
- 1974: first Dutch satellite (ANS).
- 1976: first soft landing on Mars (Viking 1/2).
- 1977: Voyager 2 to Jupiter, Saturn, Uranus and Neptune.
- 1979: first successful flight of the European Ariane launcher.
- 1981: first flight of the Space Shuttle.
- 1986: first launch of Mir, the permanent Russian space station.
- 1990: launch of Hubble Space Telescope.
- 1998: launch of the first element of the International Space Station, the Russian Zarya
module.
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, AE1110-II Introduction to Aerospace Engineering-II
Launch vehicles
Commercial spaceflight (also known as new space)
A lot of things are going on now concerning commercial spaceflight:
- Reduction of costs
- Developments driven by private funding
- NASA and other customers
- SpaceX
- Orbital ATK
- Boeing
- Contracts for servicing ISS
- Re-usability of rocket stages and capsules
- Blue Origin
- Space tourism
Current trends
Larger Satellites:
- Geostationary
- Increased bandwidth requirements
Smaller satellites:
- Reduction of costs
- Involvement of non-classical players
- Cube sats
- Constellations
Smaller launchers
- Reduction of costs
Bigger launchers
Hosted payloads
- Reduction of cost
- Military, civil
Manned missions to the Moon, Mars
- International competition
- Private competition
- Larger rockets
- Resource utilization
- Additive manufacturing
Low-thrust propulsion
- Interplanetary missions
- All-electric geostationary spacecraft
Solar sailing
Green propellants
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, AE1110-II Introduction to Aerospace Engineering-II
Space
Vacuum
Space is a vacuum, it is at an altitude of more than 120 km. In space there is almost no lift and drag.
Space has very harsh conditions, there is no way humans can breathe in space. Also for propulsion in
space it is very important that there is no oxygen for combustion. There is also an outgassing of
materials, this means that because of the conditions and the temperatures materials ultimately
disappear. Due to the high temperatures when the spacecraft is between the earth and the sun there
is a lot of evaporation, this results in the fact that lubrication of parts is very difficult. Space is a very
aggressive environment since the atomic oxygen erodes plastic.
Thermal environment
Because there is no atmosphere and very few elements there is no convection, this means that the
major source of heating is radiation and within systems, spacecraft etc conduction is also possible.
The intensity of sunlight is much larger in space compared to earth (∓500 𝑊/𝑚2 on earth compared
to 1367 𝑊/𝑚2 in space). It can be extremely hot and cold in space (−270℃ − 120℃) compared to
an earth temperature of 293 𝐾.
Radiation
In space there is no atmosphere to protect against dangerous types of radiation, some types of
radiation can destroy living tissue, electronics or plastics. The good thing about this is that for some
applications in satellites the full electromagnetic spectrum is visible.
High-energy particles
Space is filled with protons and electrons. There are radiation belts (van Allen radiation belts). The
sun sometimes has eruptions in which it throws out lots of charged particles. On Earth this can be
seen sometimes as the aurora borealis and the aurora australis.
Weightlessness
There is weightlessness because there is no acceleration. There is a conservation of momentum.
There is still a gravitational force, this means that there is an attraction inversely proportional to the
square of the distance between the centers of the bodies.
Gravity
𝑀𝑠𝑝𝑎𝑐𝑒𝑐𝑟𝑎𝑓𝑡 𝑀𝑒𝑎𝑟𝑡ℎ
𝐹𝑔 = 𝐺
(𝑅𝑒𝑎𝑟𝑡ℎ + ℎ𝑜𝑟𝑏𝑖𝑡 )2
𝑀𝑒𝑎𝑟𝑡ℎ 𝜇
𝑔=𝐺 2
=
(𝑅𝑒𝑎𝑟𝑡ℎ + ℎ𝑜𝑟𝑏𝑖𝑡 ) (𝑅𝑒𝑎𝑟𝑡ℎ + ℎ𝑜𝑟𝑏𝑖𝑡 )2
𝑀 𝜇
To find 𝑔0 we say that ℎ0 is equal to zero, we then find:𝑔0 = 𝐺 𝑅2𝑒𝑎𝑟𝑡ℎ = 𝑅2
𝑒𝑎𝑟𝑡ℎ 𝑒𝑎𝑟𝑡ℎ
Staying in orbit
To stay in an orbit there is a centripetal force directed to the center of the earth.
The centripetal force can be found using the following formula:
2
𝑉𝑜𝑟𝑏𝑖𝑡
𝐹𝑐 = 𝑀𝑠𝑝𝑎𝑐𝑒𝑐𝑟𝑎𝑓𝑡
𝑅𝑒𝑎𝑟𝑡ℎ + ℎ𝑜𝑟𝑏𝑖𝑡
The gravitational force and the centripetal force should be in equilibrium, we then find:
𝑔0
𝑉𝑜𝑟𝑏𝑖𝑡 = 𝑅𝑒𝑎𝑟𝑡ℎ √
𝑅𝑒𝑎𝑟𝑡ℎ + ℎ𝑜𝑟𝑏𝑖𝑡
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Rockets
We use rockets to go into space because jet engines and propeller engines do not work in space
because of the absence of air and oxygen. Rocket engines are used to provide the force to overcome
gravity and the drag force. Also it is a way to achieve the high velocities required in space.
Types of space propulsion
There are various different types of space propulsion, some of which are still under development:
- Solid-propellant rocket engine: this type is easy for storage and for use in the future since the
solid stays in the rocket when stored.
- Liquid-propellant rocket engine
- Hybrid rocket engine
- Thermo-nuclear rocket engine
- Electro-magnetic propulsion (ion-plasma)
- Solar radiation pressure (solar sailing)
Principle of rocket motion
The basic principle of rocket motion is Newton’s law: every action has an equal but opposite
reaction. This means that since the propellant is expelled out of the engine at a high velocity, the
spacecraft will go into the other direction. The thrust is computed with the formula: 𝑇 = 𝑚 × 𝑉𝑒 . In
this formula 𝑚 is the mass flow and 𝑣𝑒 is the exit velocity. The acceleration of the spacecraft is then
𝑇
given by the formula: 𝑎 = 𝑀, where 𝑀 is the mass of the spacecraft. The theoretical final velocity of
𝑀
the spacecraft can also be computed: 𝑉𝑒𝑛𝑑 = 𝑉𝑒 × ln ( 𝑀𝑠𝑡𝑎𝑟𝑡 ).
𝑒𝑛𝑑
History
The history of rockets started with the V2 in Nazi-Germany, this rocket really was a technological
masterpiece. It was single stage rocket with a liquid propellant. The range of this rocket was several
hundreds of kilometers.
Main rocket components
The main rocket components are:
- Structure
- Propellants
- Rocket engine
- Aerodynamic shape
- Control systems
- Avionics
- Payload
- Payload fairing
Schematic liquid-
propellant rocket engine
A typical liquid-propellant
rocket engine looks like the
figure on the right, in this
figure the fuel is first used
to cool down the nozzle,
there are also rockets where
the propellant is used to
cool the nozzle and then
directly ejected.
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, AE1110-II Introduction to Aerospace Engineering-II
Payload fairing
The payload fairing (the ‘shield’ around the payload):
- Protects payload during ascent against aerodynamic forces and aerodynamic heating.
- Maintains a “clean-room” environment for “sensitive” payloads.
- Is affected by heat generated by friction during the launch phase.
- Is jettisoned outside the atmosphere, exposing the payload. This causes a mechanical shock
and a spike in acceleration.
- Is typically a cone-cylinder combination. Due to aerodynamic considerations, however,
specialized fairings are in use as well.
Stages
Most rockets have several stages, this is done because you can then lose mass, therefore the climb
will become easier. So if you do not need a tank anymore for example you can drop it and continue
with less mass.
Launch constraints
If a rocket has multiple stages there are some launch constraints. For example you want to drop the
stages in the ocean and not on land, therefore you want to launch in the direction of the ocean or
sea.
European launcher development efforts
- ELDO, founded in 1962: Europa, never reached orbit (consisted of first stage, existing French
second stage and a newly developed German third stage).
- France: Diamant (1965-1975), some satellites were launched.
- UK: Black Arrow (1969-1971), one satellite was launched.
- ESA: Ariane 1-5, Vega and Ariane 6 is in development.
Current challenges
Current challenges are decreasing the launch costs by a factor 10 or 100. Also the reliability needs to
increase, from 1957-2009 out of 5038 launches, 417 launches failed. This gives a success rate of 91.7
%.
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Satellite orbits
Kepler’s laws of planetary motion
1. The orbits of the planets are ellipses, with the Sun at one focus of the ellipse.
2. The line joining a planet to the Sun sweeps out equal areas in equal times as the planet
travels around the ellipse.
3. The ratio of the squares of the revolutionary periods for two planets is equal to the ratio of
the cubes of their semi-major axes.
Newton’s laws of motion
1. In the absence of a force, a body either is at rest of moves in a straight line with constant
speed.
2. A body experiencing a force F experiences an acceleration 𝑎⃗ related to 𝐹⃗ by 𝐹⃗ = 𝑀𝑎⃗, where
M is the mass of the body. Alternatively, the force is proportional to the time derivative of
the momentum.
3. Whenever a first body exerts a force 𝐹⃗ on a second body, the second body exerts a force −𝐹⃗
on the first body, 𝐹⃗ and −𝐹⃗ are equal in magnitude and opposite in direction.
Attraction of masses
All point masses are attracted to each other. The force between these two masses can be calculated
𝑀 𝑀
using the formula: 𝐹 = 𝐺 1 2 2 .
𝑟
Acceleration between two masses
To find the acceleration between two masses, we can use the 2nd law of Newton.
𝐹 𝐹 𝑀1 + 𝑀2
𝑟̈ = −𝑎2 − 𝑎1 = − − = −𝐺
𝑀2 𝑀1 𝑟2
If one of the two masses is a lot bigger compared to the other mass (for example the Earth and a
𝑀 𝜇
satellite), we can say the following: 𝑟̈ = −𝐺 21 = − 2 . Where 𝜇 is a constant which can be different
𝑟 𝑟
for different planets and stars.
General equations of motion for satellites, planets and moons
𝜇 𝜇 𝑟⃗ 𝜇
The 1D case is: 𝑟̈ = − 𝑟2 , to convert this to a 3D case we find: 𝑟̈ = − 𝑟2 𝑟 = − 𝑟3 𝑟⃗. This can also be
𝑥̈
𝜇 𝑥
written as: ( ̈ ) = − 3 (𝑦𝑧).
𝑦
𝑟
𝑧̈
Conservation of angular momentum
𝜇
𝑟⃗ × 𝑟̈⃗ = − 𝑟⃗ × 𝑟⃗ = 0
𝑟3
𝑑
(𝑟⃗ × 𝑟̇⃗) = 𝑟̇⃗ × 𝑟̇⃗ + 𝑟⃗ × 𝑟̈⃗ = 0
𝑑𝑡
𝑟⃗ × 𝑟̇⃗ = 𝑟⃗ × 𝑉⃗⃗ = 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 = 𝐻 ⃗⃗
- The motion is in one plane
𝑑𝜑 𝑑𝜑
- 𝐻 = 𝑟𝑉𝜑 = 𝑟 (𝑟 𝑑𝑡 ) = 𝑟 2 𝑑𝑡
= 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡
𝑑𝐴 1 𝑑𝜑 1
- Area law (second law of Kepler): 𝑑𝑡 = 2 𝑟 2 𝑑𝑡
= 2𝐻
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, AE1110-II Introduction to Aerospace Engineering-II
Conservation of energy
𝜇
𝑟̇⃗ ∙ 𝑟̈⃗ + 3 𝑟̇⃗ ∙ 𝑟⃗ = 0
𝑟
1𝑑 1𝜇 𝑑 1𝑑 2 1 𝜇 𝑑 2
(𝑟̇ ∙ 𝑟̇⃗) + 3 (𝑟⃗ ∙ 𝑟⃗) =
⃗ (𝑉 ) + (𝑟 ) = 0
2 𝑑𝑡 2 𝑟 𝑑𝑡 2 𝑑𝑡 2 𝑟 3 𝑑𝑡
𝑑 1 2 𝜇
( 𝑉 − )=0
𝑑𝑡 2 𝑟
𝑉2 𝜇
Integration gives: 2 − 𝑟 = 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 = 𝐸
This equation shows kinetic and potential energy per unit mass.
Orbit equation
𝜇
𝑟⃗ ∙ 𝑟̈⃗ + 𝑟⃗ ∙ 𝑟⃗ = 0
𝑟3
𝑑 𝜇
(𝑟⃗ ∙ 𝑟̇⃗) − (𝑟̇⃗ ∙ 𝑟̇⃗) + = 0
𝑑𝑡 𝑟
Note: 𝑟⃗ ∙ 𝑟̇⃗ = 𝑟⃗ ∙ 𝑉
⃗⃗ = 𝑟𝑉𝑟 = 𝑟𝑟̇ and 𝑟̇⃗ ∙ 𝑟̇⃗ = 𝑉
⃗⃗ ∙ 𝑉
⃗⃗ = 𝑉 2
This gives the following:
𝜇
𝑟𝑟̈ + 𝑟̇ 2 − 𝑉 2 + = 0
𝑟
𝑉 2 = 𝑉𝑟2 + 𝑉𝜑2 = 𝑟̇ 2 + (𝑟𝜑̇ )2
𝜇
𝑟̈ − 𝑟𝜑̇ 2 = − 2
𝑟
Combination of equations
𝑝
Combining the equations gives the 1st law of Kepler: 𝑟 = 1+𝑒 cos(𝜃):
- 𝜃 = 𝜑 − 𝜑0 = 𝑡𝑟𝑢𝑒 𝑎𝑛𝑜𝑚𝑎𝑙𝑦
- 𝜑0 = 𝑎𝑟𝑏𝑖𝑡𝑟𝑎𝑟𝑦 𝑎𝑛𝑔𝑙𝑒
- 𝑒 = 𝑒𝑐𝑐𝑒𝑛𝑡𝑟𝑖𝑐𝑖𝑡𝑦
𝐻2
- 𝑝= 𝜇
= 𝑠𝑒𝑚𝑖 − 𝑙𝑎𝑡𝑢𝑠 𝑟𝑒𝑐𝑡𝑢𝑚
From this we can derive the orbital equation: 𝑟 =
𝑎(1−𝑒 2 )
1+𝑒 cos(𝜃)
:
- Pericenter A distance 𝑟𝑝 = 𝑎(1 − 𝑒)
- Apocenter A’ distance 𝑟𝑎 = 𝑎(1 + 𝑒)
𝑟 +𝑟
- Semi-major axis 𝑎 = 𝑎 𝑝
2
𝑟 −𝑟
- Eccentricity 𝑒 = 𝑟𝑎 +𝑟𝑝
𝑎 𝑝
- Location of focal center 𝐶𝐹 = 𝑎 − 𝑟𝑝 = 𝑎𝑒
10
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