We’ve been following the progress of the Japanese spaceship IKAROS — the first to unfurl a solar sail in deep space. Today, the ship made the only first that really matters: it caught the sun’s rays with its 3,000 square-foot sail and successfully used the energy to speed its way through space.
Each photon of light exerts 0.0002 pounds of pressure on the 3,000-square-foot sail, and one after another they succeeded in propelling the nearly 700-pound drone. Japanese scientists expect to be able to control IKAROS’s velocity by adjusting the angle at which incoming radiation strikes the sails. For a full technical explanation of how the drone is moving, check out the Japanese space agency JAXA’s press release.
Solar sail technology is important because it allows spacecraft to travel without fuel, which could allow them to penetrate ever deeper into space.
Via LA Times
11 Responses to “Japan’s Ikaros Spacecraft Successfully Propelled by Solar Sail”
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the article is incorrect when it says a single photon produces 0.0002 pounds of pressure.
the entire photon sail under full sunlight produces ~0.0002 pounds of thrust to the 700 pound unit
This seems wrong. Each photon???
Each photon of light exerts 0.0002 pounds of pressure on the 3,000-square-foot
Looks like a minor misunderstanding here… the force of 0.0002 lb is the total force of all the trillions of photons transferring momentum to the spacecraft. Thus, the sail is resulting in a very small, but continuous, acceleration.
pound is a unit of force, not pressure
Pressure is the force per unit area.
the pound is a unit of force.
In the world of imperial units a \”pound of pressure\” is generally meant to be pounds per square inch….thus .0002 pounds of pressure IS a unit of pressure.
The article incorrectly states that each photon carries 0.0002 pounds of force, while this is the total force delivered by all the light shining on the craft.
Type this into Google:
(1000 watt/m^2)(3000 ft^2)/c in pounds
As in the comments above, the total force from the light hitting the sail is .0002 pounds.
I’m going to say the same thing everyone else says…
If I did the math right…if this thing were have .0002 pounds of force applied in the same direction for a year (not that it would), then it’s change in velocity after a year should be about 198mph. Or 1978 mph in ten years. Unfortunately the amount of force drops rapidly as you move away from the sun.
Make the solar sail 1/2 mile on a side and the total force ramps up to nearly 1/2 pound. *Made sufficiently light* with ultra-thin material, that kind of force can do more serious acceleration over a few months.
well, 6 grams of carbon formed into buckycloth one atom thick would be about 3000 square feet. This strongest of known materials would also need ribs and edge bindings to create the optimal shape to take the strain of the solar wind.
Then if the payload was also 6 grams this combined theoretical craft of 12 grams with .1 grams acceleretion would accelerate at about .008 G or 8 cm/sec/sec would bring the craft to about 2,500,000 meters per second after one year. 300,000,000 m/sec = light speed, so it would be about 1% of light speed. By now the solar drive would have dropped a lot due to distance from the sun, so this needs to be re-calculated in stages that match the decline of the solar drive to have any accuracy at all.
It does show that light craft with high strength-light weight solar sails of bucky cloth are worth pursuiing for long term survey projects.