Thank you, Jared. I understand now. Best wishes, Joe ________________________________ From: Jared Smith <jared@smithplanet.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Monday, January 2, 2012 9:43 AM Subject: Re: [Utah-astronomy] Time it takes to get to the Moon On Mon, Jan 2, 2012 at 12:27 AM, Joe Bauman <josephmbauman@yahoo.com> wrote:
Thanks for the info, Jared. But I'm still having trouble understanding the reason why this approach is preferable, since they went farther and used more fuel than they otherwise would have. -- Joe
They used a bit more fuel than would have been necessary to simply get the probe to the moon (as in slam into it or fly past it). But it would have required substantially more fuel for both launch and for braking to also stop at the moon via a direct Hohmann transfer. By using the Lagrange point and the very slow approach, the overall fuel requirements were decreased, and payload mass could thus be increased. The tradeoffs are that it takes a long time to get there and it requires much planning, computing power, and adjustments on-the-fly due to the instability of the Lagrange point. If we were willing to wait years or centuries to get there, we could use various Lagrange points to send probes to almost any place in the solar system with barely more fuel than is required for escape velocity. We can even park probes at a Lagrange point and then nudge them on to some other interesting place (most any planet, the sun, a comet or asteroid such as was done with ISEE-3 - http://en.wikipedia.org/wiki/ISEE-3, etc.) or back to Earth at will. See http://en.wikipedia.org/wiki/Interplanetary_Transport_Network Jared _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php