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#71
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Lunar Sample Return via Tether
Ian Stirling wrote:
Not at all. If you make the sail be slightly bowl shaped instead of flat, then you should be able to make both "newtonian" and "cassegrain" sails which will allow you to both thrust normaly, at odd angles to the sail and even directly towards sun by moving of and changsing the angle of the "secondary sail". Sure, its not free. But the overall thrust on the sail system can never be towards the sun. And the seperation between them can never be larger than some hundred times the diameter of the primary sail, sharply limiting the use. Why is that limiting? This is not, after all a telescope, so you don't really care about optical quality and mass-center problems should be handle-able (or probably even handled better) by placement of the payload. Well, if the solar sail has a cenrtal pole that connects primary and secondary sails, the mass-center could also be movable (by moving the payload), so as to wary where the sail goes. but may well not be worth it. Oh, a question - why would a "cassegrain" sail not have its thrust towards Sun? | ... | | /|\ | | / | \ | |/ | \| ..... | ...... (allowing that ... are curved surfaces, etc). -- Sander +++ Out of cheese error +++ |
#73
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Lunar Sample Return via Tether
(Vincent Cate) wrote:
In order to avoid spinning too fast when you are winching a sample in on one tether, you let the other tether out on the other side at the same time. This stores up the angular momentum and gets the other tether ready to pickup a sample. Sample #92 in my simulator now does this (winching one tether in while another is winching out). In order to get rid of waves in the tether I gave the winch a new option. You can specify that a winch should only pull in when the tension is less than some percentage of the recent average tension seen at the winch (you specify the time period). Also when letting out you can specify that the minimum tension for letting out is a percentage of the recent average. Values near 100% (so limit is recent average) work well at minimizing waves even though the speed and tension are changing as we come in or out. Also, much of the power for winching in can come from the winch/generator on the tether that is going out. They won't be going the same speed most of the time since the tension is higher for whichever is longer at the time. You can specify a winch/generator power limit too. Simulator is at: http://spacetethers.com/spacetethers.html - Vince ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~ Vincent Cate Space Tether Enthusiast http://spacetethers.com/ Anguilla, East Caribbean http://offshore.ai/vince ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~ You have to take life as it happens, but you should try to make it happen the way you want to take it. - German Proverb |
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