Boots on the Moon "SPACE_200" Flashcards
Define a System as it applies to the system engineering process?
An integrated composite of people, products & processes that provide a capability to satisfy…
Systems Engineering Turns…?
Needs into Capabilities
What are the three basic elements illustrated in the systems Engineering “V”?
Design
Control
Realize
4 parts of the systems engineering universe?
Cost
schedule
Performance
Risk
Six tasks in the space mission design process?
- Develop a clear mission need statement
- From users goals define mission objectives
- Develop a logical conops
- Derive Mission Requirements
- Investigate alternative mission conops
- Select baseline concept
Purpose of CONOPS/ Operational View 1 (OV-1)?
Scope the system
Identify Integration/parts
Share with stakeholders
3 cost estimation methods?
Detailed bottoms up
Parametric Estimating
Analogy Based Estimating
Describe weightless feeling on orbit?
Free fall, velocity maintains a constant fall around the earth.
What happens to a satellites speed as it gets closer to earth?
Speeds up, faster
Kepler’s Second Law “equal areas covered”
According to Kepler’s third law, the square of the satellites orbital period is proportional to what?
Cube of the average distance to the sun
If the distance between two masses triples, will the gravitational force between the two objects increase or decrease? by how much?
Decrease
Inverse Square Law
1/R^2 AKA decrease by a factor of 9
How does an orbit’s total energy at perigee compare to its total energy at apogee?
Total energy remains unchanged KE+PE=Total energy // At perigee KE is greater At apogee PE is greater
How does angular momentum compare at perigee compare to at apogee?
Angular momentum must remain constant
Equal
?
Classical Orbital Elements (COE)
Semimajor Axis (a)- Orbit size Eccentricity (e)- Shape/ellipse Inclination(i)- Tilt, measured at ? Right ascension of the ASC node() - Argument at perigee()- Ture Anomaly (v)-
4 Common Orbit Types?
Sunsync
MEO Semi Sync
HIO
Geosynchronous
The Six Space Environment Effects Areas?
Gravity (covered previously) Atmosphere/Neutral Vacuum Micrometeoroids and Orbital Debris Plasma/Charged Particles Radiation
Levels of Earths Atmosphere?
Exosphere Thermosphere Mesosphere Stratosphere Troposphere
Orbit changed from LEO to MEO would change what hazards?
- Vacuum
- EM Radiation
- Charged Particles
- Neutral Atm particles
- MMOD
#3 charged particles Worse #4 Drag better #5 MMOD better
How does atmospheric drag affect spacecraft?
Slows and deorbits
How does the solar cycle affect the frag forces experienced by a spacecraft?
Solar cycle affects expansion and contraction of the drag area…
Most significant impact of the plasma environment on the spacecraft?
Charges the surface of he satellite, EM interference and arcing
What are the Van Allen radiation Belts?
Magnetic belt influenced charged particle collection zones
Why is man made orbital debris more serious than natural debris?
?
What part of the radio frequency spectrum is most affected by scintillation?
UHF
GPS if receiving on ground
Where and when does scintillation typically cause problems?
Equator and poles
Dawn and Dusk
How are wavelength and frequency related?
Inversely Proportional
International organization that controls frequency allocations?
FCC
Federal Communications Commission
Atmospheric effects that impact laser performance?
Distortion
Absorption
Thermal Blooming
Diffraction
Advantages of laser communications?
High data rates
Hard to Jam
Disadvantages of laser communications?
Signal attenuated by atmosphere
Requires accurate pointing
large power source
GPS inclination?
55 degrees
Fun fact: highest inclination from florida launch due to political marriage to shuttle
Inclination of the International Space Stations?
51.6 degrees
Fun fact: So the Russians could have easy access to said hanging BnB.
How many GPS satellites are required to be accurate?
4
3 is enough in a perfect world. The fourth is for timing.
List the 4 key issues in communication?
Distance
Language
Speed
Environment
What is the primary figure of merit for a digital communication link?
Bit Error Rate
Eb/No
Eb= Energy Per Bit
No=Noise Density
Identify two ways to increase the gain of a directional antenna?
Power & antenna size
?
Define bit error rate?
Bit Error Rate
Eb/No
Eb= Energy Per Bit
No=Noise Density
Open Loop Control system?
Fire and forget?
Closed Loop Control System?
Controller (thermostat), actuator (furnace), plant (house), sensor (Thermometer).
Generic components of a closed loop system?
Controller
Actuator
Plant
Sensor
Estimation method that utilizes mathematical relationships to relate costs to physical, technical and performance parameters
Parametric Estimating
Restricted two-body assumptions applied, what is the only satellite characteristic required to ….something
???
F=MA
Answer:MASS?
Restricted two-body assumptions applied, what is the only satellite characteristic required to ….something
???
F=MA
Answer:MASS?
Which COE describes the Shape of an orbit?
Eccentricity
Which COE describes the Shape of an orbit?
Eccentricity
Which COE(s) describes the orientation of orbital plane?
Inclination
Right ascension of the Ascending Node (RAAN)
Argument of perigee is?
Location of perigee within the orbital plan
Expressed in degrees starting from RAAN
Which COE defines the location of a spacecraft in its orbit?
True anomaly
0-360 Measured from Perigee
Describe CEO that make a Geostationary comms sat?
eccentricity 0
inclination 0
semi maj axis 42164 KM
Orbital perturbation that has small drag near perigee that leads to a more circular orbit?
Drag
Orbital perturbation that makes sun synchronous possible?
J2
Orbital perturbation that makes sun synchronous possible?
J2
Orbital perturbation that makes Molniya orbit to be 63.4 degrees?
J2
?
A satellite that is Sun Synchronous will always be illuminated by the sun?
F
A satellite that is Sun Synchronous will always be a retrograde orbit?
T
A satellite that is Sun Synchronous will pass over the same spot on the earth once every day?
F
List the four sources of energy (heat) that cause temperature changes in a spacecraft.
Sun
Earth
Internal Dissipation
Which heat transfer method is the ONLY one that removes heat from a spacecraft?
Radiation
List four design approaches used to control temperature on a spacecraft.
Insulation Louvers Radiators Phase change Materials Heat pipes
For most space missions, when are the most demanding loads applied to a spacecraft?
Launch
What issues make moving mechanisms on spacecraft problematic?
hard to test in relevant environment, failure point
What are some challenges that make successful software development for space systems so difficult?
Time
Complexity
What is the relationship between orbital inclination and launch site latitude that must exist to ensure two launch windows each day for direct orbits?
launch site latitude must be below the inclination
For the launch conditions below, answer true or false and briefly explain why:
a) We have two opportunities per day to launch directly into an inclination less than the launch site’s latitude.
False
For the launch conditions below, answer true or false and briefly explain why:
b) From Kennedy Space Center (L0=28.5°) we can launch directly into an inclination of 28.5° any time of day that weather permits and still obtain the specified right ascension of ascending node ().
False
You only have 1 window to launch into the exact inclination
For the launch conditions below, answer true or false and briefly explain why:
c) We cannot launch directly into an inclination less than a launch site’s latitude.
False
For the launch conditions below, answer true or false and briefly explain why:
d) We cannot launch directly into an inclination greater than the launch site’s latitude.
False
Why isn’t Kennedy Space Center used to launch satellites into retrograde orbits?
Danger, would go over CONUS
What launch azimuth (or direction) maximizes mass to orbit for a given launch vehicle?
East
Delta V required to get to orbit?
9.3 km/sec
Which of Newton’s three laws of motion best describes how rockets work?
3rd law-Every action has an opposite and equal reaction.
Thrust depends on how much “stuff” mass is thrown away from rocket
What two parameters determine the thrust produced by a rocket?
Mass
Exhaust velocity
What parameter describes rocket efficiency?
Specific Impulse
Isp = F(thrust)/MGo
What determines the amount of delta V produced by a rocket?
propellent efficiency (Isp) Initial mass (full tank) Final Mass (fuel expended tank)
Why can multiple-stage launch vehicles put more payload mass into orbit than single-stage launch vehicles?
Reduces total mass
How do thermodynamic rockets produce thrust?
Heat/pressure energy
Which type of rocket cannot be stopped and restarted?
Thermodynamic
Which type of rocket cannot be stopped and restarted?
Solid rockets (chemical)
What is the key advantage and associated disadvantage of electrodynamic rockets?
Adv:
high Isp (efficency)
Long life
Unlimited cycling
Dis:
Low thrust Mouse farts
High power
Describe the two elements of the mission operations system.
- Command, control and communications (C3)
2. Mission Management operations
What are the three activities performed by satellite control networks?
Tracking, Telemetry and Commanding (TT&C)
What are the five measurements are made to track a satellite?
Time, Elevation, Azimuth, Range & Range Rate(TEARR)
What are the two types of telemetry data?
State of Health
Payload or Mission Data
What are the two types of satellite control networks, and what is the basic difference between the two?
Common User Network (shared)
Dedicated User Network (not shared)
Describe the role of 22 SOPS. What is the “product” they produce of interest to satellite operators?
Network Tasking Order (NTO)
24 hour schedule
Describe the two segments of the NASA Space Network.
Space Segment (TDRS) Ground Segment (white sands/Guam)
What are the benefits of using a concurrent approach for space mission operations planning?
Critical
Grounds nerds in reality
Relevant experience
- When the restricted two-body assumptions are applied, what is the only satellite characteristic required to completely describe the acceleration (and, thereby, future changes in position and velocity) of a satellite in Earth orbit?
Distance
R^2
Sunsync Inclination
97 deg ish
Give example COE of Geostationary
42K
What characteristic of a Hohmann Transfer is the “key” to its efficiency?
tangential & in plane
Describe the velocity changes (number and direction) that must be generated to perform a Hohmann Transfer from a low-altitude circular orbit to a high-altitude circular orbit.
1 burn at perigee to get elliptical
1 burn at apogee to get circular
What is the most propellant (energy)-efficient way to change both the size and inclination of an orbit?
Combined plane change
If the final ΔV of a Hohmann Transfer is not performed, describe the resulting satellite motion.
Stuck in elliptical
What is the foundation of rendezvous and all space control missions?
SDA
List three types of rendezvous?
Hohmman
Fast Transfer
Co-Orbital
What are the two parameters that are traded in most rendezvous maneuvers?
Time
Propellent
Linear drift
Smaller semi major axis
Natural motion circumnavigation
Doing circles around target. More eccentric.
Where and when does scintillation typically cause problems?
Dusk
Equator and Poles
What two agencies provide space environmental support in the United States?
NOAA
557th Weather wing (USAF)
What is the best wavelength for detecting a missile plume at a temperature of 724 K?
4 Microns
Which type of observation resolution quantifies the minimum separation between features that must exist to differentiate one from the other?
Spatial resolution
Identify the parameters that determine diffraction-limited (or angular) resolution?
Distance from ground
Wavelength
Camera Aperture
- If the distance between a radar and its target object increases by a factor of 3, what happens to the strength of the reflected pulse when it returns to the radar?
R^4
How does a radar determine the range to a target object?
(Time/2) * Speed of light)
Identify two ways to increase the gain of a directional antenna.
Bigger antenna
Shorter wavelength
What are some methods that could be employed to increase the Eb/N0 (signal-to-noise ratio) at the receiver of a ground terminal?
Antenna size
Electronics temp
Drop altitude
What are the tradeoffs a comm subsystem designer must consider if she decides to use a high-gain, low-power antenna on the satellite?
Narrow pointing
Which multiple access strategy allows users to share the same frequency band by designating the specific time interval during which each user can transmit digitized data packets?
Time division Multiple access
What international organization controls frequency allocations for satellite communication systems?
ITU
Which spacecraft subsystem compensates for orbital perturbations to keep a spacecraft in the right orbit?
NGC
Navigation Guidance Control
Which spacecraft subsystem compensates for disturbance torques to keep a spacecraft pointed in the right direction?
ADCS
What external references do attitude control sensors typically use to determine a spacecraft’s orientation? Which provides the highest precision?
STARS (Most Precise)
Sun
Earth
List three characteristics that determine the amount of power per unit area (W/m2) produced by a solar panel?
Solar available
Solar cell material
Orientation
- List three momentum-based closed-loop attitude control systems.
Bias momentum
Reaction Wheels
Control Moment Gyro (CMG)
What are some of the key considerations in the design or choice of secondary (rechargeable) batteries?
Specific Energy Density
What are some of the key considerations in the design or choice of secondary (rechargeable) batteries?
Specific Energy Density #/Depth of discharges
What are some improvements being tested and/or considered for DoD satellite command and control (AFSCN upgrades)?
Phased array antennas
Interoperable Network
