All topics Flashcards
slide 1 space weather (140 cards)
1
Q
What purposes to satellite’s fulfil [4]
A
- Weather
-Navigation
-Space Physics - Communication
2
Q
What do planetary Explorers do? [4]
A
- Fly-bys
-Probes
-Landers
-Rovers
3
Q
What do Manned Spacecraft do? [3]
A
-Probes
-Lunar Landers
Stations
4
Q
Force Equation of two planets
A
F=MmG/r^2
5
Q
Spacecraft Angular Momentum
A
h=r*v=const (both vectors)
6
Q
Velocity of circular orbit
A
v=sqrt(mew/r)
7
Q
period of circular orbit
A
P=2pi*sqrt(r^3/mew)
8
Q
Escape velocity
A
v=sqrt(2mew/r)
9
Q
Specific energy(kinetic plus temp specific)
A
e=-mew/2a
10
Q
velocity for all orbits
A
sqrt(2mew/r -mew/a)
11
Q
a for parabolic and hyperbolic
A
a=infinity a<0
12
Q
eccentricity [2]
A
sqrt(1-h^2/(mew*a)) c/a (c is foci and middle)
13
Q
co planer equation
A
change in v= 2vi*sin(a/2)
14
Q
What is the vernal equinox vector?
A
The vector from the centre of earth to the sun on the spring equinox day. Its a reference system.
15
Q
Equation for launch site on earth
A
cos(i)=cos(latitude)sin(azimuth)
16
Q
What does equation for launch site assume?
A
Earth doesn’t rotate
17
Q
Draw out space craft horizon thing find sw,ah,Dh
A
check in ipad
18
Q
What is a sidereal day?
A
a full earth rotation- not counted as an actual day.
19
Q
What is a solar day?
A
An actual day, when you’ve turned around enough to face the sun again
20
Q
What is rotation of Apsides?
A
Earths pivot point changing each day
21
Q
What is regression of nodes?
A
Nodes of an orbit decreasing due to drag
22
Q
What is a patched conic orbit
A
A way of getting from one planet to another by orbiting the sun and using hyperbolic orbits
23
Q
What is C3 in regards to patched conic orbit?
A
Vhe^2 used to asses energy required for launch of planetary mission
24
Q
How does Photon propulsion work?
A
Powerful laser beam directed to provide momentum.
25
How does Solar sail propulsion work?
Large sheet of film, highly reflective use energy of solar radiation particles
26
What do Space rockets need that Aircraft engines don't
oxygen to carry with them
27
Rocket Equation
v=v0+ vr*ln(m/m-f)
28
Rocket Equation w/ Impulse
v=v0+Isp*g*ln(m/m-f)
29
What is Cold Gas propulsion?
Letting pressurised gas out of a nozzle
30
Why would you use Cold Gas over over propulsion?
Simple
31
What is Thermal-Solar rockets?
Uses solar energy to increase heat of something
32
Why would you pick a liquid rocket? [3]
Controllability, Throttling, Restart avalible
33
What is Throttling?
Changing the Thrust
34
Why would you pick a solid rocket? [3]
Simple, reliable, quick launch time
35
What is a hybrid rocket?
solid fuel, liquid oxidiser
36
What can liquid rocket systems be subdivided into?
Monopropellant and bipropellant
37
What is monopropellant?
Catalytic decomposition of a single propellant
38
What is bi propellant
Chemical reaction between fuel and oxidiser
39
How does Electric thermal work
heat up propellant by passing over a heating element and means it expands and go out fast.
40
Electrostatic thrusters what they do?
Accelerate positively charged particles in static electric field
41
Lorentz and Hall what do they do?
Use there own force to move particles to create propulsion
42
What does nuclear propulsion do?
Some kind of nuclear reaction created heat and therefore pressure
43
What is Albedo radiation?
Planets reflecting sun radidation
44
What is predicted temperature range?
results of thermal modelling of the system
45
What is design operating range?
extremes of predicted temperature range
46
What is Acceptance temperature range
Limits for operating and non operating modes of a unit
47
What is a black body?
A material that absorbs all incident radiation
47
Qualification temperature limit
Flight hardware should be able to operated within these limits to be accepted as part of the satellite (biggest temp limit)
48
Absorptivity
percentage of incoming radiation that is absorbed by a material
49
Emissivity
Proportion of radiation emitted by surface compared to a black body at the same temp
50
Equilibrium Temperature eq
G a A cos(theta) = A omega Eir T^4
51
Scaling G
G1 * D1^2=G2*D2^2 (unchecked)
52
What is surface irradiation?
G- total amount of radiation incident upon the surface per unit time and area
53
What is surface Radiosity?
Total amount of radiation leaving the surface per unit time
54
What do you assume when doing thermal analysis on real
uniform Temp, constant J, G,a,e across surface.
55
Equation for net thermal energy leaving a surface
q=(E-J)/(1-e)/eA
56
Sum of view factors are
unity
57
Two parts of Oppenheim network for each surface
Node with temp, node with J
Node with temp connected to J with eA/(1-e)
Node with G connected to everything else with AF
58
Oppenheim Thermal network: Deep space what changes?
Temperature of 0 so Js=0 now thermal branch
59
Oppenheim Thermal network: Insulated walls what changes
j=sigmaT^4
60
How do you include conduction in the network?
Make new radiation constant with different temperatures i guess
61
What's the difference between thermal active and passive control systems?
Active is active pumping shit and passive just like let heat out
62
What is a heat pipe?
Way of getting rid of heat by vaporising wick and then it flows to the outside and then condenses again.
63
What is an Optical Solar Reflector?
Reflective surface with low absorptivity
64
Downsides of Optical Solar Reflector
High cost and fragile
65
What is like an Optical Solar Reflector but more durable?
Silver coated teflon
66
What is a Phase Change Device
Absorbs heat from sources that use high power over a short period
67
What are Cryogenic systems
Used to cool IR detectors
68
Is it easier to cool for a long time or a short time?
Short time
69
Active refrigeration Systems, how long, pros and cons
Long duration, problems with vibration, operating life
70
Expendable cooling systems, how long, how does it do it
short duration mission, fluid absorbs heat and then is yeeted into space
71
What are moving hardware torques?
deployment of solar panels, antennas, cameras
72
What are two types of mass expulsion torques
unintentional, intentional
73
What are some examples of unintentional mass expulsion torque?[2]
leakage of fuel, accidental thrust firing or in the wrong direction
74
What are some examples of intentional mass expulsion torque?
Dumping of propellant, payload separation
75
What is Propellant slosh?
The torque caused by fluid in a partly filled tank
76
How can you mitigate propellant slosh?
Small tanks and tanks with baffles- type of vane
77
What is the problem with Crew motion?
Can cause disturbances and change attitude
78
Why does gravity gradient torque disturbances occur?
Because of the variation in the Earths magnetic field
79
What Shape of spacecraft is most affected by gravity?
Long ones
80
What is Solar Radiation Torque caused by?
Radiation incident on spacecrafts surface
81
Solar Radiation Torque depends on? [4]
Intensity, surface geometry and optical properties, direction of the sun
82
What is the Aerodynamic force disturbance?
Due to atmosphere effects
83
Equation linking torque force and, S distance between cog and cop
T=F*S
84
What causes Magnetic Torque disturbances?
The interaction between the spacecrafts magnetic field and the planets magnetic field
85
What parts of the Spacecraft cause a magnetic field?
Current loops and metallic components residual magnetism
86
What is a spin stabilised system?
a spacecraft that it made to spin in one direction that makes it resistance to disturbance torques
87
Pros of spin stabilised systems [4]
Simple to stabilise, good pointing accuracy, don't need sensors sometimes, natural scanning motion
88
Cons of spin stabilised systems [3]
Bad at manoeuvring, need redundant solar arrays, some equipment such as antenna not possible
89
What are dual spin systems
Most of it spinning apart from one bit on top
90
What makes dual spin system better then spin stabilised? [2]
Allows body pointing sensors and higher pointing accuracy
91
What makes dual spin system worse then spin stabilised? [2]
Expensive, break easily
92
What is a three axis stabilised system?
Maintains alignment, using sensors, thrusters and reaction wheels.
93
Pros of 3 axis stabilised? [2]
Unlimited pointing accuracy, All solar arrays are used all the time.
94
Cons of 3 axis stabilised? [3]
ACS hardware complex, expensive, too many points of failure
95
What is gravity gradient stabilisation?
Only for long objects gravity will keep them facing the same way.
96
Advantages of Gravity Gradient stabilisation? [2]
Long life time, simple
97
Disadvantages of Gravity gradient stabilisation [2]
Only good for low orbits, modest pointing accuracy
98
Attitude determination for spin stabilised system
If you know spin axis and spin rate of your space craft. Use earth and sun sensors and measure angle and rate of them. Direction matching of one will be stable.
99
Attitude determination for 3 axis stabilised systems
use distance to the sun and distance to some other star and use that to find the coordinate system and therefore where it is
100
What are sensors?
They provide information about the position of spacecraft to known quantities
101
Inertial sensors what?
Measure position of sun, earth, bright stars
102
Rate sensors what
Detect spacecraft rotations in inertial space
103
Earth Horizon Telescope what?
a telescope with a narrow field of view, sends a pulse when starts seeing and stops seeing earth.
104
What does an analogue sensor output?
Continuous function of sun angle
105
What does sun presence sensor output?
Constant output when sun is in FOV
106
What does digital sun sensor output?
digital encoded output as a function of the suns angle
107
What is a analogue sun sensor?
Normally a solar sensor, measure current use cos to work out angle
108
How can you improve an analogue sun sensor?
Use multiple in different angle or just a bar or masks
109
what is a sun presence sensor?
like a photo cell in a slit
110
What is a digital sensor?
Strips of photocells
111
How accurate are star sensors?
Very
112
Can star sensors operate when they are close to facing the sun
no
113
What does a magnetometer sense?
Senses planets magnetic field
114
Pros of magnetometer? [3]
Reliable, lightweight, low power requirements
115
Cons of magnetometer? [2]
Only work close ish to planet
Solar winds can disturb them
116
What is a gyroscope?
Uses a rapidly spinning mass to sense and respond to changes in inertial orientation.
117
What is an actuator?
Used to change satellite attitude
118
What can be used as a actuator? [4]
Thruster, magnetic torque rods, movable appendages, momentum wheels
119
What is a momentum wheel
store angular momentum
or make manoeuvres happen
120
What is a magnetic torque rods?
Torque rods are surrounded by a coil each tried to control it
121
Downside of magnetic torque rods?[2]
interferes with reading of magnetic field, and can only be done close to a planet
122
What is proportional control equation
t=-K* theta
123
What is position plus rate control?
T=-K*theta rate -K2*theta
124
What is bang-bang control? (where theta is error)
T=-a/aTmax
125
What is the geospace?
The area with size 200 Re around earth
126
What are ground induced currents caused by
Space weather leads to earths magnetic field changing which induces the currents
127
What do ground induced currents effect? [2]
PowerGrid's
Pipelines
128
What is reconnection?
The coming together of antiparralel magnetic fields which produce space weather
129
What effects to solar flares cause? [3]
-Radio Blackouts
Degradation of solar panels
Increased drag as X-rays are absorbed heating up atmosphere
130
What are coronal mass ejections?
Magnetic fields interacting lead to energised particles being released from the sun
131
What are galactic cosmic waves?
High energy particles from supernova events from different suns
132
Equation decay or orbit radius
Cd*rho*A/m*sqrt(mew*r)
133
Equation decay of orbit period
-3pi*Cd*rho*A/m*r
134
Source of Energetic Particles in Space [3]
Cosmic Rays, the sun, radiation belts
135
What is deep dielectric charging
Build up of energetic particles lead to charge on internal electronic components
136
What is Displacement damage?
Energetic particle knocks nuclei from regular position
137
What is total ionising dose?
Ionisation slowly degrading efficiency of solar arrays
138
First stage comes off first or last
1st
139
Difference between space craft horizon and swath width.
Spacecraft horizon is circle that spacecraft can see and swath width is the diameter of the circle
