QUIZ – electric propulsion | GIESEPP MP H2020 project

#1. What would be the two major aspects that guide the selection of an orbital propulsion system for one application?

List price & availability of the system

Time to orbit & wet mass of the system

Technology & maturity of the system

Origin & experience with the supplier of the system

#2. What is a typically completely different requirement of an EP system for a GEO platform compared to a LEO platform?

Size

Delta V

Lifetime

Propellant

#3. What is today much more in focus of a modern propulsion system than it used to be in the past?

Marketing

Reliability

Low power consumption

Price

#4. What is the ratio between Full Electric, hybrid and Full Chemical propulsion in average for Starlink, One Web and Telesat constellations?

33%; 33%; 33%

66%; 33%; 0%

100%; 0%; 0%

#5. What are the two main stages where electric propulsion are commonly used on S/C?

Re-entry and fine positioning

Transfer to final orbit and station keeping or drag compensation

Fine positioning (<1m) and station keeping or drag compensation

Only transfer to final orbit

#6. What are the 5 main parameters to size the number of thrusters for a telecom S/C?

S/C dry mass, S/C Available electric power, thruster Impulse, duration of orbit transfer and thrust

Propellant Flow regulation accuracy and Electronic unit efficiency

Only electronic unit efficiency

Propellant Flow regulation accuracy, thruster Impulse and thrust

#7. What are the main advantages of RIT 2X compared to Hall Effect Thruster?

Propellant mass savings and high specific impulse

Propulsion units mass savings

Propulsion units mass savings and space pollution

Space pollution and propellant mass savings

#8. Why do the cryopumps, in contrast to e.g. turbomolecular pumps, have to be switched off and warmed up at regular intervals during tests with radio-frequency ion thrusters?

The connected compressor is not designed for continuous operation

The running cryopump acts as a source of interference for the RF current responsible for the power coupling into the thruster

The capacity of the cryopumps is limited, so the cryopumps must be regenerated

#9. Which of the following plasma properties can be determined with the help of a near-field Faraday probe?

The shape of the radial plasma density distribution

The electron temperature in the discharge vessel

The ion energy in the thruster plume

#10. Why do charge exchange processes play a key role in modelling grid erosion?

Slow charge exchange ions are attracted to the negatively biased grid of the thruster and sputter material there on impact.

The charge exchange processes significantly change the neutral gas density in the discharge vessel. The plasma responds to this change by changing the electron temperature and ion density. This changes the ion optics in the grid system.

The ion beam is broadened by the charge exchange processes and directly hits the grid if the grid voltage is not adjusted.

#11. What are the most relevant functions of a PPU in an EPS?

To ignite the main chamber of the thruster

To control the thrust through the beam current and voltages

To protect the system against unexpected events or failures

All of the above

#12. From an industrialization point of view, what is the most critical aspect of a PPU?

The use of Gallium Nitride transistors

The use of digital control

Automatic manufacturing and testing processes

Use of any type of COTS, as long as they are cheap

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QUIZ – electric propulsion

GIESEPP MP QUIZ

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