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astronomy

Solar electric propulsion

Solar electric propulsion is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Solar electric propulsion rather than just read about it. In short: Solar electric propulsion (SEP) is the combination of solar cells and electric thrusters to propel a spacecraft through outer space. This technology has been exploited in a variety of spacecraft designs by the European Space Agency (ESA), the JAXA (Japanese Space Agency), Indian Space Research Organisation (ISRO) and NASA.

Solar electric propulsion — main illustration
Solar electric propulsion — illustration

Key takeaways

  • Solar electric propulsion belongs to astronomy; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Solar electric propulsion to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Solar electric propulsion from memory before moving on to harder problems.

Reference excerpt

Solar electric propulsion (SEP) is the combination of solar cells and electric thrusters to propel a spacecraft through outer space. This technology has been exploited in a variety of spacecraft designs by the European Space Agency (ESA), the JAXA (Japanese Space Agency), Indian Space Research Organisation (ISRO) and NASA. SEP has a significantly higher specific impulse than chemical rocket propulsion, thus requiring less propellant mass to be launched with a spacecraft. The technology has been evaluated for missions to Mars.

Overview Solar electric propulsion combines solar panels on spacecraft and one or more electric thrusters, used in tandem. There are many different types of electric thrusters, including a so-called ion thruster, a term that is often incorrectly used to describe all types of electric thrusters. It is also possible to generate electricity from the Sun without using photovoltaic panels, such as with solar concentrators and a Stirling engine. A 50 kilowatt SEP system was studied in the 2010s for a mission to an asteroid. In February 2012, NASA awarded a contract for a Solar Electric Propulsion Flight System. An example of work on this type of technology is Advanced Electric Propulsion System. The NASA Solar Technology Application Readiness (NSTAR) ion engine has been used with photovoltaic solar panels, which was tested on the Deep Space 1 mission along with Solar Concentrator Arrays (Launched in 1998 as part of the New Millennium Program). SEP has been studied as a technology for a mission to Mars. In particular the high specific impulse of the ion engines could lower overall mass and avoid having to use nuclear technology for power when coupled with solar panels. A 1998 study for SEP for a human mission suggest that a human-sized spacecraft would need 600 to 800 kilowatts of electrical power coupled with ion engines with a specific impulse of 2000 to 2500 seconds.

Mission examples BepiColombo mission to Mercury (launched) Dawn to asteroids Vesta and Ceres (completed) Deep Space 1 to asteroid Braille and comet Borrelly (completed) GSAT-9 communication (launched) Hayabusa to asteroid Itokawa (completed) Hayabusa2 to asteroid Ryugu (primary mission completed, extended mission ongoing) LightShip space tug for Mars exploration (under development) Lunar Gateway space station orbiting the Moon (under construction) Psyche to asteroid Psyche (launched) GSAT-20 (launched) Starlink low-earth-orbit internet (thousands of satellites in service)

Electric propulsion technologies Resistojet rocket Ion thruster High Power Electric Propulsion Pulsed plasma thruster Hall-effect thruster Magnetoplasmadynamic thruster Microwave electrothermal thruster Field-emission electric propulsion Variable Specific Impulse Magnetoplasma Rocket (VASMIR)

See also Batteries in space Liquid-propellant rocket List of spacecraft with electric propulsion Nuclear electric rocket Solar sail Solar thermal rocket

References

Illustrations

Solar electric propulsion: Artistic view of Deep Space 1, showing both the solar panels and ion engine (with blue exhaust), major aspects of this solar electric design. Solar energy may also be temporarily stored in chemical batteries inside the spacecraft bus.
Artistic view of Deep Space 1, showing both the solar panels and ion engine (with blue exhaust), major aspects of this solar electric design. Solar energy may also be temporarily stored in chemical batteries inside the spacecraft bus.
Solar electric propulsion: The Dawn spacecraft's xenon tank prior to integration with spacecraft. The xenon was the propellant for the solar-power ion drive of the spacecraft which would go on to orbit two different asteroids in the early 21st century.
The Dawn spacecraft's xenon tank prior to integration with spacecraft. The xenon was the propellant for the solar-power ion drive of the spacecraft which would go on to orbit two different asteroids in the early 21st century.
Solar electric propulsion: Roll-out solar panel tested in Earth Orbit at the International Space Station (ISS), 2017.
Roll-out solar panel tested in Earth Orbit at the International Space Station (ISS), 2017.

Worked examples

Example 1 — a first encounter with Solar electric propulsion

Start with the simplest possible case. Write down what Solar electric propulsion claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Solar electric propulsion before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Solar electric propulsion ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Solar electric propulsion

In research
Solar electric propulsion appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Solar electric propulsion in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Solar electric propulsion is common in secondary-school and first-year university syllabi. It links to neighbouring topics Solar power and space, Spacecraft electric propulsion, Spacecraft propulsion, so understanding it makes those chapters shorter.
In everyday life
Look for Solar electric propulsion outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study Solar electric propulsion in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Solar electric propulsion means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Solar electric propulsion out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Solar electric propulsion in simple terms?

Solar electric propulsion (SEP) is the combination of solar cells and electric thrusters to propel a spacecraft through outer space. This technology has been exploited in a variety of spacecraft designs by the European Space Agency (ESA), the JAXA (Japanese Space Agency), Indian Space Research Orga…

Why does Solar electric propulsion matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Solar electric propulsion?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Solar electric propulsion.

Tags

  • Solar power and space
  • Spacecraft electric propulsion
  • Spacecraft propulsion

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