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Extra ASS > Questions on Notes > Flashcards

Questions on Notes Flashcards

1
Q

List the types of perturbations

A

Secular: linear variation of an orbital element
Short period: varies with the period < orbital period
Long period: varies with the period > orbital period

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2
Q

List the perturbations and their effects

A

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

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3
Q

What can be found at the different Lagrange points

A

L1: solar observation eg Sun-Earth Explorer
L2: space observation eg James Webb telescope
L3: no found use so far
L4&5: smaller moons

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4
Q

What factors affect the effect the atmosphere has on a spacecraft’s orbit

A
  • spacecraft design
  • orbital velocity
  • atmospheric density
    • altitude
    • latitude
    • solar activity
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5
Q

What is the difference between solar winds and solar radiation pressure

A

solar winds: electrons and protons

SRP: photons

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6
Q

Name and label the components needed to describe a hyperbolic trajectory

A

θ: True anomaly of the asymptote
β: Angle asymptote to apsides
𝛿: Turn angle
Δ: Aiming radius

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7
Q

What is the sphere of influence

A
  • 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
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8
Q

What does patched conics ignore

A
  • other bodies
  • perturbations
  • launch windows
  • course corrections
  • planes and angles
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9
Q

What is RLA and DLA

A

RLA: right ascension of the launch asymptote
DLA: declination of the launch asymptote

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10
Q

Briefly describe the Mars Express mission

A
  • Launch June 2003
  • Used a fast transfer
  • no aerobraking
  • J2 effect to produce global coverage
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11
Q

List the types of scientific missions

A

Astronomy (telescopes in space)

  • Deep space
  • Exoplanets

Solar System

  • planets
  • comets
  • asteroids

Heliosphere environment

  • sun
  • space weather

Fundamental physics
- testing theories

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12
Q

What are primordial objects

A

comets or asteroids with ancient composition from the early solar system which haven’t got close tot he sun or been in many collisions

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13
Q

Details two spacecraft that have studied comets

A

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
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14
Q

Function of the ground segment

A

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

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15
Q

Ground station elements

A
  • Antenna system
  • Transmit and Receive RF equipment
  • System clcok
  • Mission data
  • Data-user interface
  • Telemerty time and control equaimepent
  • Station control centre
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16
Q

Ground station design

A
  • Coverage
  • Horizon mask
  • Data-user needs
  • cost
  • Accessibly for maintenance
  • Availability
  • Transmission of data to users
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17
Q

Name the UK launch vehicles, old and new

A

Old

  • Black night
  • Blue Streak
  • Black Arrow

New
- Orbex

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18
Q

List the delta V, specific impulse and mass requirements of a launcher

A

required delta-V for orbit: 9.3km/3
specific impulse of H2/O2: 4500m/s
launcher has to be 87% fuel

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19
Q

Describe the benefits of SSTO over two stage

A

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

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20
Q

The requirements of propellant injectors

A
  • produce smooth even combustion
  • promote rapid mixing and burning
  • prevent the flame from reaching the injector head
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21
Q

Describe open and closed pump fed systems

A

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
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22
Q

Define ECLSS

A

Environmental Control
- maintaining the environmental conditions that sustain life

Life Support
- providing the material resources and removing the waste products to sustain life

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23
Q

Detail the 3 most basic human life support inputs

A

Oxygen: 0.9kg
Water: 2.3kg
Food: 0.6kg (3000Cals)

24
Q

List the 4 food types

A
  • Irradiated
  • Freeze dried
  • Thermostabilsed
  • Rehydrated
25
Q

What is the short term effect of zero-g on the human body and how can it be combated

A

Space adaption syndrome

  • Impaired balance
  • lasts about 4 days
  • drugs
26
Q

What are the long term effects of zero-g on the human body and how can it be combated

A

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
27
Q

List all countermeasures to the effects of zero-g

A
  • Drugs
  • Exercise
  • Suits
  • Bungie cords
  • Vibrating plates
  • Artificial gravity
28
Q

What are the design considerations for a deployable truss

A

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
29
Q

Why is there a demand for SSTO

A

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

30
Q

SSTO launcher requirements

A

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%
31
Q

What affects atmospheric effects on a spacecraft

A
  • Spacecraft design
  • Orbital velocity
  • Atmospheric density:
    • altitude, latitude
    • solar activity
32
Q

Provide details on a solar obsevation spacecraft

A

Parker Solar Probe

  • Heat shield
  • niobium wires
  • retractable solar panels
  • water coolant system
33
Q

What is EIRP

A

Equivalent isentropic Radiation Power

- The sum of the gain of the transmitter and transmitter power

34
Q

Draw and describe the Sabatier Process

A

see notes

35
Q

What are the two suit types

A

Survival suit: in case of cabin pressure loss

Space Suit: used for EVA

36
Q

What are the two methods of solving the restricted 3 body problem

A

Special perturbation

General perturbation

37
Q

What is the required drift of Argument of Perigee (ω) for a Molniya orbit

A

dω/dt=0

38
Q

How high does Earth’s atmosphere extend

A

past 350km

39
Q

Describe B-plane targeting

A

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

40
Q

Why was Mars Express launched when it did

A
  • Most advantageous launch energy in 6000yrs

- Already developed sensors from passed failed missions

41
Q

What are the main 2 perturbations acting on a

satellite in GEO?

A

Luni-Solar perturbations and nonsphericity (𝐽2 mainly) effects

42
Q

Describe the design features of a solar sail.

A

Large deployed area, small stowed size,

reflective coating, steerable, low mass

43
Q

How can a solar sail use solar radiation

pressure to travel further from the Sun?

A 
Align the sail to reflect sunlight along the
orbital direction (retrograde), producing a
prograde force.
44
Q

What are the three mission segments of the

patched conics method?

A

Hyperbolic departure from original planet,
heliocentric transfer, hyperbolic arrival at target
planet

45
Q

Which planet in our Solar system has the

largest sphere of influence?

A

Neptune as the SOI depends on both the semimajor axis of the planet and its mass

46
Q

Ignoring any differences in C3, why might
a Type II transfer be preferable for a
spacecraft going into orbit around the
target planet?

A

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

47
Q

How could the ‘available’ C3 for a given

mission be increased?

A

Using a more powerful launcher or making the

spacecraft lighter

48
Q

What is an omnidirectional antenna and why
would one be useful on a satellite or
spacecraft?

A

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.

49
Q

What is the aim of a link budget?

A

To ensure a suitable margin in the communication
system to give an acceptable signal-to-noise ration at
the receiver

50
Q

What are the key launcher components?

A
  • Engines and combustion chambers
  • propellant tanks and fuel pumps
  • staging adaptors
  • booster rockets/stages
  • avionics for guidance navigation and control
  • payload adaptor
  • aerodynamic faring
51
Q

What other force acts on astronauts on a spinning

space stations?

A

The Coriolis force which can cause disorientation when

moving ‘up’ and ‘down’ with respect to the circumference of the rotating station

52
Q

What is a rough stowed length percentage for a

modern deployable boom?

A

Around 2-5%

53
Q

What is space weather and why is it important?

A

Short term fluctuations in emissions from the Sun

Can disturb power and communication systems both on satellites and on the ground

54
Q

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
  • 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.
55
Q

What are the typical engineering constraints on an astronomy mission?

A

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

56
Q

How can the “double whammy” cost issue of two stage to orbit launchers be addressed

A

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.

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