From: vince@offshore.ai (Vincent Cate) Newsgroups: sci.space.tech Subject: Re: Earth to Earth Moon L5 Cycler orbit References: NNTP-Posting-Host: 209.88.68.33 Message-ID: <9186edb5.0305251234.2743b261@posting.google.com> alexterrell@yahoo.com (Alex Terrell) wrote in message news:... >I was wondering whether it would be possible to have an >Earth orbit with the following characteristics: You can play with this sort of thing with my simulator at http://spacetethers.com/spacetethers.html Check out the examples for "Earth-Moon Lagrange Orbits" (sample #27) and "Moon safe return orbit" (sample 41, 42). >As the cycler ship passes near the rotovator, it exchanges passenger >modules, dropping of passengers returning to Earth and collecting >passengers coming from Earth. The exchange period is very short, like under 1 second. I worry that if your passengers leave the rotovator but don't hook up with the cycler that they could experience a "bad failure mode". You may be able to make something that does not release unless it is pulled so hard that it must have hooked up. But there is an issue here. My father (Henry Cate) and I are working on a design where you toss from a LEO rotovator to a pair of hotels on a 20 km tether in GEO. See examples 46 and 47 in my simulator. These hotels each have tethers on winches for picking up or tossing payloads (they would go out from either hotel). There are several nice things about this: 1) When coming from a LEO toss to the GEO tether, if you fail to hookup you just return to Earth 4 hours later (4 hours each way). 2) Could launch a suborbital rocket to LEO tether every 90 minutes when it comes by as it will always be able to toss to GEO hotels. 3) You can accumulate a bunch of payload and tourists at GEO and then toss toward the moon in your cycler every 14 days or so. It takes like 8 days to go past the moon and come back but about 14 days for moon to be crossing the plane of the GEO orbit again, so that 14 days is the limiting thing. 4) At the moon you can have another tether that goes from the cycler to the surface of the moon. As long as you pick up as many Kg of stuff (returning tourists, water, aluminum, rocks) as you send down, it is almost free to operate. 5) The two GEO hotels act as lots of ballast for your GEO tether tosses. 6) The two GEO hotels can have some gravity so (1/6 G in sample) so that farming and dealing with water, dust, etc, is easier. 7) The delta-V from GEO to either GTO or moon toss is not very high, so it is not hard to have a tether strong enough to handle a good sized cycler. The cycler is really just a smaller hotel. By winching in different lengths you can do different tosses. 8) Even if the tether between the two hotels broke, neither hotel is in danger of reentry or having escape velocity. They average GEO speed and are not really that far from it at any given time. Buzz Aldrin and Ron Jones have some interesting Moon Cycler orbits on page 186 of "Space The Free Market Frontier". One is an orbit that takes about a month, the other has 3 short trips per month. My "safe return orbit" sample is similar to one pass of the 3 short trip idea. These are fun orbits. I don't have them in my simulator yet though. With a big tether in GEO you catch the cycler after it comes back from the moon each time, so you don't need a cycler period that matches the period of the moon's orbit. >The cycler ship should pass the L5 colony twice on each orbit, >allowing a transfer every 14 days. >[...] >Is such an orbit possible? The moon will be pulling on your cycler, so it is either tricky or not possible to make one that is going to continue for many months without major course correction. But I encourage you to try with my simulator. Even if you don't get it you will get a feel for the orbits. If you do get it, please send me the input so I can add it to my list of samples. -- Vince ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Vincent Cate Space Tether Enthusiast vince@offshore.ai 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