Does Photoelectric Conversion Affect Momentum Transfer in Solar Sails?

In summary, the conversation discusses the concept of a solar sail and its ability to convert photons into electrical energy. The question arises if this conversion affects the momentum transfer of the photons onto the sail. It is determined that in a perfect conversion, all photon energy would be converted to electrical energy, including momentum. However, in reality, only half of the momentum would be transferred in an absorptive sail, while twice the momentum would be transferred in a reflective sail.
  • #1
sanman
745
24
Suppose you have a solar sail that was capable of perfect photoelectric conversion.

So this means that photons from the Sun are striking your solar sail, and also being photoelectrically converted to electrical current.

My question is - does the photoelectric conversion at all affect the momentum transfer of the photons to the solar sail?
 
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  • #2
If conversion was PERFECT,all photon energy would be converted to electrical...this would include momentum...so it would appear some current momentum would be converted to electrical in a "PERFECT conversion.

does the photoelectric conversion at all affect the momentum transfer of the photons to the solar sail?

via your established criteria, seems like it...whether that's practical or not is another question..such as solar cells getting warm in the sun...

Edit: Ignore the above...it seems the poster is addressing spacecraft solar SAILS...I wasn't paying attention...I missed photoELECTRIC instead of photoVOLTAIC...
 
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  • #3
Naty1 said:
If conversion was PERFECT,all photon energy would be converted to electrical...this would include momentum...so it would appear some current momentum would be converted to electrical in a "PERFECT conversion.



via your established criteria, seems like it...whether that's practical or not is another question..such as solar cells getting warm in the sun...

So only SOME photon momentum would be converted into electrical energy, or ALL of it would?
 
  • #4
Naty1 said:
If conversion was PERFECT,all photon energy would be converted to electrical...this would include momentum...so it would appear some current momentum would be converted to electrical in a "PERFECT conversion.

No, momentum is still conserved in an inelastic collisions.

Normally solar sails are designed to be reflective, so you have an elastic collision between light and the sail. To make a photovoltaic sail, it would have to be absorptive, so you have an inelastic collision, with only half the momentum transfer.
 
  • #5
Why half?
 
  • #6
If the photon is absorbed, its momentum changes from p to 0, so the momentum of the sail increases by p.

If the photon is reflected, the momentum changes from p to -p, so the momentum of the sail must increase by 2p. (actually it will be slightly different than this due to the fact that there is also energy transferred, resulting in a different wavelength.)
 

Related to Does Photoelectric Conversion Affect Momentum Transfer in Solar Sails?

1. What is a Photoelectric Solar Sail?

A Photoelectric Solar Sail is a type of spacecraft propulsion system that uses photons from the sun as a source of propulsion. It works by reflecting the photons off of a large reflective sail, which creates a small amount of thrust that can be used to propel the spacecraft forward.

2. How does a Photoelectric Solar Sail work?

A Photoelectric Solar Sail works by using the pressure of photons from the sun to push against a large reflective sail. This creates a small amount of thrust, which can be directed and controlled by adjusting the angle of the sail in relation to the sun.

3. What are the advantages of using a Photoelectric Solar Sail?

One of the main advantages of using a Photoelectric Solar Sail is that it does not require any fuel, making it a sustainable and cost-effective form of propulsion. It also has the potential to reach very high speeds, making it ideal for long-distance space travel.

4. What are the potential applications of a Photoelectric Solar Sail?

A Photoelectric Solar Sail could be used for a variety of applications, including deep space exploration, satellite propulsion, and even interstellar travel. It could also be used for maintaining the orbit of satellites or for de-orbiting space debris.

5. What are some challenges associated with using a Photoelectric Solar Sail?

One of the main challenges of using a Photoelectric Solar Sail is the need for a large and lightweight sail material, which can be difficult to construct and deploy in space. There are also limitations on the speed and direction of the spacecraft, as it is dependent on the angle and intensity of the sunlight. Additionally, the sail may be vulnerable to damage from micrometeoroids or other space debris, which could impact its effectiveness.

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