6 ms·
Because it's so close to Earth, the drag force will be much greater than any propulsion force achieved from solar particles, which means its orbit will decay an
by dandelany 16y ago
Because it's so close to Earth, the drag force will be much greater than any propulsion force achieved from solar particles, which means its orbit will decay and it will fall out of orbit. However, this doesn't preclude it from being a solar sail, it just means it's not a very efficient sail. Eventually, we'd like to send these into deep space, where there is no drag from the atmosphere, allowing the craft to accelerate indefinitely. But for now, it makes sense to keep it in orbit and study it at close range so we can be sure the "sail" effect works as predicted.
More info: http://www.nasa.gov/mission_pages/smallsats/10-109.html http://www.nasa.gov/mission_pages/smallsats/10-109.html
"The relatively low-deployment altitude means drag from Earth's atmosphere may dominate any propulsive power it gains from the sun, but the project represents a small first step toward eventually deploying solar sails at much higher altitudes... because the sail will deploy relatively close to Earth, researchers will have a difficult time detecting the slight solar effects."
- jacquesm 16y ago> allowing the craft to accelerate indefinitely. In theory that's all very nice, in practice the power available for acceleration decreases as the cube of the distance. Of course a bit of acceleration is better than nothing but this will only work well if you have very large amounts of time, and since all systems will have to survive for all that time I don't see this as a practical means of propulsion. Bussard Ramjets are a lot harder to construct (and shield) but I think if there ever is going to be a practical means of achieving speeds that are a significant fraction of lightspeed then I think that's where it's going to come from, not from solar sails (even though the technology definitely has its charm).
- jimmyk 16y ago>In theory that's all very nice, in practice the power available for acceleration decreases as the cube of the distance. This is why any solar sail intended to move very quickly will open up somewhere closer to Mercury.
- dandelany 16y agoI don't know that it's very practical either; but the fact remains that it is, in fact, a solar sail, just not a particularly good one.