I was wondering if lunar material could be thrown from the moon's surface in such a way that it would be retrievable with a tug sent from L2.
On the thread about lunar slings I showed some work I did where a lunar sling on the near side could throw to a lunar elevator stretched from the sub-L2 point on the farside across the L2 point and arrive at the elevator with zero relative velocity. A whole lot simpler in my opinion than the complicated O'Neill catcher-bag, many of the engineering details of which were pretty sketchy at best.
Interesting. In the thread you started "Sling stuff FROM the Moon"? Am poking around in that thread but can't find that.
Quote from: Hop_David on 09/20/2009 02:18 amI was wondering if lunar material could be thrown from the moon's surface in such a way that it would be retrievable with a tug sent from L2.Without need for extreme precision the launcher might be able to send payloads on trajectories that loiter in the vicinity of L5 for quite some time, awaiting the arrival of a tug.
Quote from: sdsds on 09/20/2009 03:18 amQuote from: Hop_David on 09/20/2009 02:18 amI was wondering if lunar material could be thrown from the moon's surface in such a way that it would be retrievable with a tug sent from L2.Without need for extreme precision the launcher might be able to send payloads on trajectories that loiter in the vicinity of L5 for quite some time, awaiting the arrival of a tug.Given an ideal CR3BP (Circular Restricted 3 Body Problem), I don't think so. The L3, L4 and L5 are in a region known as the Forbidden Realm. Orbits are time reversible.
This notion of considering orbits in the CR3BP as time-reversible deserves consideration. It's obviously true, if you could run time backwards. But reversing the spacecraft's velocity is not equivalent to running time backwards. Instead, wouldn't one need to reverse the velocity of all three objects to get the equivalent reverse orbit?