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This option allows you to preset all of the properties of the sail
that depend only on the material. A short list is given of materials
that either are available or have been proposed as producible in the
near future with technology currently under development. Click the
button to preset the yellow boxes to the values for the
chosen material. After that, you can change the
attributes to see how the properties affect the final outcome.
The green boxes are not constrained by the material. You
can change them as you see fit to find out what size of sail you
need for a given payload and so on. However, there is no guarantee
that your selection will be feasible in the real world.
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For any real sail material, the reflectivity will be less than 100%.
That part of the incident radiation which is not reflected must be absorbed by
the sail, and that power must be balanced by
radiation from the unlit side. If we assume the best possible
emission characteristic, that of a black-body radiator, the radiated
power depends only on the temperature.
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Maximum temperature at which the material retains adequate strength |
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| Power radiated from the unlit side of the sail at maximum temperature |
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| The reflectivity of the material together
with the radiated power determines the maximum incident radiation that
the sail can withstand. That in turn limits how close to the Sun
the sail can be launched.
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Reflectivity |
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| Maximum incident power |
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| Minimum launch distance from the centre of the Sun |
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| Of course we may choose to
launch from further out. The Sun is a violently active object and
various unpredictable phenomena may make it unsafe to approach to the
theoretical limits of the material. In fact, with a sufficiently high
temperature material such as Tungsten, the minimum launch distance may even be inside the
Sun (695,500km ≡ 0.00465 AU).
Check this box to always use the minimum launch distance or uncheck the box and enter the desired launch location either in km or AU
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Actual launch distance from the centre of the Sun |
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| Incident power at launch |
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| Sail temperature at launch |
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| Radiation pressure at launch |
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| The density of the material and
the thickness of the sail determine the areal density (mass per unit
area). This together with the radiation pressure will determine the
acceleration of the sail |
Material density |
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| Sail thickness |
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| Areal density (mass per unit area) of the sail |
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| Initial acceleration without payload |
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| The size of the sail can be
increased to give an acceleration as close to the unloaded value as we
like, but what size is needed for a given payload? |
| Diameter of the sail |
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| Mass of the sail |
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| Payload |
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| The resulting performance of your
launch system:
The fields should update automatically as you change the
entries, but if not just press this
button.
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| Initial acceleration including payload |
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| Final speed |
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| Time to reach 95% of final speed |
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| Time to reach Proxima Centauri |
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