Test Yourself Questions

Question 1

What is the strongest perturbation for Low Earth Orbit?

Answer 1

Atmospheric drag.

Question 2

What are the design requirements of solar sails?

Answer 2

Deployable, large unfolded area, reflective, low mass and small stow size.

Question 3

What planet in our solar system has the largest SOI?

Answer 3

Neptune. SOI is dependent on both mass and semi major axis.

Question 4

Why are Type II transfers sometimes more appealing than Type I?

Answer 4

Type II transfers arrive at the target planet with a lower velocity, meaning less energy must be used for the retrograde burn to enter a parked orbit.

Question 5

What kind of orbit is useful when using a low thrust engine?

Answer 5

Spiral orbit.

Question 6

What kind of trajectory is a good safety measure for crewed missions?

Answer 6

Free return trajectory. If something were to go wrong then the spacecraft will return to Earth regardless.

Question 7

What factors are to be considered when designing a ground station?

Answer 7

• Location
• Link data rates
• Requirements for data handling
• Communication between ground station and data users

Question 8

What is an omnidirectional antenna?

Answer 8

An antenna that radiates power equally in all directions (perpendicular to axis). It is useful when trying to establish communications when altitude is not completely known.

Question 9

What is the aim of a link budget?

Answer 9

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

Question 10

When is a launch vehicle considered to be successful?

Answer 10

• Accurate placement of payload in the desired orbit
• Keeps forces on the payload within the limits
• Reliable and cheap

Question 11

What % by mass does the payload take up in a launch vehicle?

Answer 11

1%

Question 12

How many stages do orbital launchers have?

Answer 12

Usually 2 or 3 main stages, some have additional boosters.

Question 13

What are the key components of an orbital launcher?

Answer 13

• Engines and combustion chambers
• Propellant tanks and fuel pumps
• Staging adapters
• Booster rockets and stages
• Avionics for guidance navigation and control
• Payload adaptor
• Aerodynamic faring

Question 14

Why is a 10% mass ratio achievable for individual stages but getting 12.7% for a SSTO reusable launcher hasn’t been achieved yet?

Answer 14

Getting the payload and additional SSTO system within the remaining 2.7% is difficult.

Question 15

What is Skylon?

Answer 15

Skylon is a SSTO spacecraft that aims to meet the system optimisation goals by using a Sabre engine capable of delivering 6100m/s Isp with a light airframe that achieves a 20% mass ratio.

Question 16

Which engine cooling methods are not suitable for SSTO reusable launchers?

Answer 16

• Heat sinks (too heavy)
• Radiative (must work in atmosphere)
• Ablative (would require re-application each launch)

Question 17

What causes combustion instability?

Answer 17

Rough Start - build up of propellant in the chamber before combustion, causes over-pressuring.

Chugging - low frequency oscillations (<100Hz), caused by feed system instabilities.

Screaming - high frequency instability (>1kHz), normally due to injector or chamber problems.

Question 18

What factors are competing upon re-entry?

Answer 18

• Deceleration (can bee too high as this can kill)
• Heating (high enough to dissipate energy but not too high that it causes damage)
• Accuracy

Question 19

What entry causes a greater total heating load, shallow or steep?

Answer 19

Shallow. The maximum temperature reached is lower, but the heating occurs for a longer period.

Question 20

Give an example of a survival spacesuit.

Answer 20

Sokol.

Question 21

What health problems can occur from being in space?

Answer 21

• Muscle loss
• Fluid and electrolyte problems
• Cardiovascular issues
• Bone degradation
• Radiation damage

Question 22

Which force, other than the centripetal force, is experienced by astronauts in a rotating spacecraft?

Answer 22

Coriolis force. This can cause disorientation when moving up and down with respect to the circumference of the rotating station.

Question 23

What is the approximate diameter of payload fairings?

Answer 23

3-5m

Question 24

Why are science instruments often moved away from the main body of the satellite?

Answer 24

To prevent interference, especially for magnetometers.

Question 25

What is the stowed length of a deployable boom as a % of the extended length?

Answer 25

2-5%

Question 26

What problems can strain deployment have?

Answer 26

Backlash. This is where the boom is still moving once it is fully extended.

Question 27

What support methods are used when testing deployable structures on Earth?

Answer 27

Gravity compensation methods such as water tables and parabolic flights.