Questions on Notes Flashcards
List the types of perturbations
Secular: linear variation of an orbital element
Short period: varies with the period < orbital period
Long period: varies with the period > orbital period
List the perturbations and their effects
Three body solution
J2: time-varying RAAN and argument of periapsis
Lunar-solar: gradual change in RAAN, inclination, the argument of periapsis and eccentricity
Atmospheric drag: gradual reduction in semi-major axis and eccentricity
Solar radiation pressure: time varying change in eccentricity
What can be found at the different Lagrange points
L1: solar observation eg Sun-Earth Explorer
L2: space observation eg James Webb telescope
L3: no found use so far
L4&5: smaller moons
What factors affect the effect the atmosphere has on a spacecraft’s orbit
- spacecraft design
- orbital velocity
- atmospheric density
- altitude
- latitude
- solar activity
What is the difference between solar winds and solar radiation pressure
solar winds: electrons and protons
SRP: photons
Name and label the components needed to describe a hyperbolic trajectory
θ: True anomaly of the asymptote
β: Angle asymptote to apsides
𝛿: Turn angle
Δ: Aiming radius
What is the sphere of influence
- the zone where the attraction of one body is greater than the attraction of all other bodies
- it is not the only body exerting an influence, just the dominant one
What does patched conics ignore
- other bodies
- perturbations
- launch windows
- course corrections
- planes and angles
What is RLA and DLA
RLA: right ascension of the launch asymptote
DLA: declination of the launch asymptote
Briefly describe the Mars Express mission
- Launch June 2003
- Used a fast transfer
- no aerobraking
- J2 effect to produce global coverage
List the types of scientific missions
Astronomy (telescopes in space)
- Deep space
- Exoplanets
Solar System
- planets
- comets
- asteroids
Heliosphere environment
- sun
- space weather
Fundamental physics
- testing theories
What are primordial objects
comets or asteroids with ancient composition from the early solar system which haven’t got close tot he sun or been in many collisions
Details two spacecraft that have studied comets
Rosetta
- orbiter and lander
- mass spectrometer
- harpoons and ice screws
Hayabusa 2
- touch and go sample return
- mass spectrometer
- fired a projectile at the comet
Function of the ground segment
Supports the space segment
- command and control
- monitor health: temperature, power, propellant pressure
- track and determine the orbital position
Relay mission data to users
- downlink mission data
Ground station elements
- Antenna system
- Transmit and Receive RF equipment
- System clcok
- Mission data
- Data-user interface
- Telemerty time and control equaimepent
- Station control centre
Ground station design
- Coverage
- Horizon mask
- Data-user needs
- cost
- Accessibly for maintenance
- Availability
- Transmission of data to users
Name the UK launch vehicles, old and new
Old
- Black night
- Blue Streak
- Black Arrow
New
- Orbex
List the delta V, specific impulse and mass requirements of a launcher
required delta-V for orbit: 9.3km/3
specific impulse of H2/O2: 4500m/s
launcher has to be 87% fuel
Describe the benefits of SSTO over two stage
Two-stage
- high cost of developing both stages a then the complex integration
- having to integrate the two stages will never allow for an aircraft-like turnaround
Single Stage
- no “double whammy” development cost
- turnaorund more aircaft like
However technically more challenging
The requirements of propellant injectors
- produce smooth even combustion
- promote rapid mixing and burning
- prevent the flame from reaching the injector head
Describe open and closed pump fed systems
Pump-fed
- use turbines to raise the pressure of the propellants
- lower pressure tanks, therefore lower mass
- higher chamber pressure
- more complex
Open
- exhaust is dumped overboard
Closed
- Exhaust is introduced to the main chamber so it can be expanded through the nozzle system
- More efficient
- more difficult to develope
Define ECLSS
Environmental Control
- maintaining the environmental conditions that sustain life
Life Support
- providing the material resources and removing the waste products to sustain life
Detail the 3 most basic human life support inputs
Oxygen: 0.9kg
Water: 2.3kg
Food: 0.6kg (3000Cals)
List the 4 food types
- Irradiated
- Freeze dried
- Thermostabilsed
- Rehydrated
What is the short term effect of zero-g on the human body and how can it be combated
Space adaption syndrome
- Impaired balance
- lasts about 4 days
- drugs
What are the long term effects of zero-g on the human body and how can it be combated
Stables and recovers on Earth
- Loss of muscle - reduced by exercise
- Loss of thirst due to an electrolyt imbalance
- Cardiovascular system weakness
- Reduced red and white blood cell count
Continues and limited recovery
- Bone calcium metabolism - vibrating plates
- Radiation
List all countermeasures to the effects of zero-g
- Drugs
- Exercise
- Suits
- Bungie cords
- Vibrating plates
- Artificial gravity
What are the design considerations for a deployable truss
Stowed configuration
- packing effceincy
- holddown and relases mechniacsm
- stored strain energy and long term storage effects
Deployment process
- Actively controlled: motor, inflation, centrifugal force
- Strain energy driven
- Testing: gravity compensation, parabolic flights, in orbit testing
Why is there a demand for SSTO
On-demand: shorter turn around and shorter lead times to launch
Cheap: currently the limiting factor limiting access to space
Reliable: improve on the loss and abort rate
Return capability: allowing two-way traffic from space
SSTO launcher requirements
Structural Optimist
- effective exhaust velocity of H2/O2 4500m/s
- 12.7% structural mass or less
Engine Optimist
- an effective exhaust velocity of 10,200m/s would allow for a structural mass of 40%
- turbojets can provide 10,000m/s
System Optimist
- SABRE engine have an effective exhaust velocity of 6,100m/s
- this would, therefore, require and structural mass of 22%
What affects atmospheric effects on a spacecraft
- Spacecraft design
- Orbital velocity
- Atmospheric density:
- altitude, latitude
- solar activity
Provide details on a solar obsevation spacecraft
Parker Solar Probe
- Heat shield
- niobium wires
- retractable solar panels
- water coolant system
What is EIRP
Equivalent isentropic Radiation Power
- The sum of the gain of the transmitter and transmitter power
Draw and describe the Sabatier Process
see notes
What are the two suit types
Survival suit: in case of cabin pressure loss
Space Suit: used for EVA
What are the two methods of solving the restricted 3 body problem
Special perturbation
General perturbation
What is the required drift of Argument of Perigee (ω) for a Molniya orbit
dω/dt=0
How high does Earth’s atmosphere extend
past 350km
Describe B-plane targeting
We target the point B on the B plane. The B plane is a plane which slices through the centre of mass of the target planet and is normal to the asymptote of the approach trajectory (NOT the approach trajectory itself). T is a vector lying along the reference plane. The reference plane could be the target equatorial plane or ecliptic or the Earth’s equator
Why was Mars Express launched when it did
- Most advantageous launch energy in 6000yrs
- Already developed sensors from passed failed missions
What are the main 2 perturbations acting on a
satellite in GEO?
Luni-Solar perturbations and nonsphericity (𝐽2 mainly) effects
Describe the design features of a solar sail.
Large deployed area, small stowed size,
reflective coating, steerable, low mass
How can a solar sail use solar radiation
pressure to travel further from the Sun?
Align the sail to reflect sunlight along the orbital direction (retrograde), producing a prograde force.
What are the three mission segments of the
patched conics method?
Hyperbolic departure from original planet,
heliocentric transfer, hyperbolic arrival at target
planet
Which planet in our Solar system has the
largest sphere of influence?
Neptune as the SOI depends on both the semimajor axis of the planet and its mass
Ignoring any differences in C3, why might
a Type II transfer be preferable for a
spacecraft going into orbit around the
target planet?
A Type II transfer will have a lower arrival speed
at the target planet than a Type I transfer,
meaning less fuel is needed to put the spacecraft
into a closed orbit
How could the ‘available’ C3 for a given
mission be increased?
Using a more powerful launcher or making the
spacecraft lighter
What is an omnidirectional antenna and why
would one be useful on a satellite or
spacecraft?
An omnidirectional antenna radiates power in all
directions (perpendicular to an axis) equally. It would be
useful to establish communications when attitude is not
known precisely.
What is the aim of a link budget?
To ensure a suitable margin in the communication
system to give an acceptable signal-to-noise ration at
the receiver
What are the key launcher components?
- Engines and combustion chambers
- propellant tanks and fuel pumps
- staging adaptors
- booster rockets/stages
- avionics for guidance navigation and control
- payload adaptor
- aerodynamic faring
What other force acts on astronauts on a spinning
space stations?
The Coriolis force which can cause disorientation when
moving ‘up’ and ‘down’ with respect to the circumference of the rotating station
What is a rough stowed length percentage for a
modern deployable boom?
Around 2-5%
What is space weather and why is it important?
Short term fluctuations in emissions from the Sun
Can disturb power and communication systems both on satellites and on the ground
You are designing a mission to measure space weather. What typical payload might it have?
What orbit would you put it in? Explain your reasoning including any disadvantages of the
chosen orbit.
- A couple from: instruments to measure magnetic fields (magnetometer), X ray, electrons, protons
- L1 points towards the Sun so would intercept particles between Sun and Earth, but more thermal shielding might be needed
- An Earth orbit would also work. Geosynchronous is what the GOES satellites do to measure weather at the same time, so these satellites can measure what is coming to one hemisphere.
What are the typical engineering constraints on an astronomy mission?
Orbit – L2 is often used because it gives a good view of deep space with the Earth and Sun
lined up in the opposite direction
Infra red detectors need to be cool and therefore have good heat shields
Telescopes need to have well-designed mirrors
How can the “double whammy” cost issue of two stage to orbit launchers be addressed
1) Make the stages simple and cheap. For example Kistler Aerospace K1 this used kerosene LOX propellants and an existing rocket engine.
2) Have the two stage identical and accept non-optimum staging (Siamese). If the two stages are the same then there is only one
system to develop. No-one has ever attempted the development of such a system
3) Use an existing aircraft for the lower stage
The message with all these approaches is that non-optimum separation systems or not using hydrogen and oxygen propellants end up with mass ratios well below the aircraft norm.
