Calculation of the "lightness number" for solar sails

In summary, the "lightness number" for solar sails is a dimensionless parameter that represents the efficiency of converting photon momentum into thrust. It is calculated by dividing the total sail area by the spacecraft mass and multiplying it by the reflectivity of the sail material. The factors that affect the lightness number include the reflectivity of the sail material, the angle of incident sunlight, and the orientation of the sail in relation to the sun. This number is important because it determines the amount of thrust and therefore the acceleration and speed of the spacecraft. To improve the lightness number, highly reflective materials can be used, the orientation of the sail can be optimized, and the spacecraft mass can be minimized.
  • #1
Val---
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Hello,
In the wikipedia article about solar sails the lightness number is mentioned and the calculation is the characteristic acceleration ac divided by the Sun´s local gravity (distance: 1AU): λ = ac / 5.93

why do they use 5,93 m/s^2 for the sun´s gravity and not 274 m/s^2?
 
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  • #2
Val--- said:
why do they use 5,93 m/s^2 for the sun´s gravity and not 274 m/s^2?
They don't use 5.93 m/s^2, but 5.93 mm/s^2, or 0.0053 m/s^2. They do this, because that's the gravitational acceleration at the distance of 1 AU.
274 m/s^2 is the surface gravity, which falls with the square of the distance.
 
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Likes Val---

FAQ: Calculation of the "lightness number" for solar sails

1. What is the "lightness number" for solar sails?

The "lightness number" for solar sails is a dimensionless parameter that represents the efficiency of a solar sail in converting photon momentum into thrust.

2. How is the lightness number calculated?

The lightness number is calculated by dividing the total sail area by the spacecraft mass and multiplying it by the reflectivity of the sail material.

3. What factors affect the lightness number of a solar sail?

The lightness number of a solar sail is affected by the reflectivity of the sail material, the angle of incident sunlight, and the orientation of the sail in relation to the sun.

4. Why is the lightness number important for solar sails?

The lightness number is important because it determines the amount of thrust that a solar sail can generate and therefore, the acceleration and speed of the spacecraft.

5. How can the lightness number be improved?

The lightness number can be improved by using highly reflective materials for the sail, optimizing the orientation of the sail in relation to the sun, and minimizing the spacecraft mass.

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