Moon's Orbital Inclination, affects on Lunar Missions

[patriot1776]

Hello! I'm new here. This might be a little bit of a complicated question. Anyway, I've been looking at the 2007 Old Farmer's Almanac and it has an article (The Last Lofty Moon, p. 74) about the Moon's currently high orbital inclination period coming to an end next year.<br /><br />This got me to thinking. Looking at the article's projections about how the Moon will be at its lowest inclination by 2014 and then will begin to rise again 2016, it got me to wondering what effect the Moon's orbital inclination will have on launches when NASA hopefully starts sending astonauts back to the Moon by that timefrime. From what I know of how launches from KSC are done, the biggest impact the Moon's orbit incination has on this is that it would affect the launch azimuth in putting a spacecraft in the right parking orbit for it to boost to the moon and reach it.<br /><br />I went back and did some simple math and found according to some VERY rough calculations, the Moon was close to the orbit inclination it was at now during the original Apollo missions, and wondering about the affects that had on the Saturn V launches.

 

[patriot1776]

If this is in the wrong place, I kindly ask somebody to move it to the proper spot on this forum.

 

[MeteorWayne]

Welcome to SDC! Great question.<br />While it's OK to ask it here, I'd think it will be answered more thoroughly and by more expert people in Missions and Launches.<br /><br />What think ye Mods?<br /><br />I have no idea as to an answer BTW, so won't even hazard a guess. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[vogon13]

IIRC, the trick is to leave earth orbit as you cross the plane of the moons orbit (whatever inclination it happens to have at that time), or more precisely, you time your departure to be crossing the plane of the moons orbit at the time you arrive there.<br /><br />In actuallity, the plane of the moon's orbit is rather more aligned with the ecliptic (the plane that the planets orbit the sun in) than you might suppose, and launches to the various planets have similar constraints, and we are able to launch to them.<br /><br />The big factor in this is it just reduces the flexibility (time wise) you might want in launching to the moon, but it won't preclude it.<br /><br /><br />If fuel is unlimited, you can go when ever you want, in reality, you will want to work with the 'system' as much as possible.<br /><br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[telfrow]

<i>While it's OK to ask it here, I'd think it will be answered more thoroughly and by more expert people in Missions and Launches. <br /><br />What think ye Mods?</i><br /><br />Methinks thou art correct. <img src="/images/icons/wink.gif" /> <br /><br /> <div class="Discussion_UserSignature"> <strong><font color="#3366ff">Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild.</font> - <font color="#3366ff"><em>Tennyson</em></font></strong> </div>

 

[patriot1776]

So vogon13, you're saying the Moon's inclination has more of an effect on your launch window, narrowing or widening it, then launch azimuth given the contraints of the spacecraft/launch system you're using and what you're wanting to do on a particular mission?<br /><br />Plus, I've also been wondering whether the Saturn V launches had steeper orbital inclinations than the current ISS missions, because I've got the impression they were from how Apollo 8 for example had a launch azimuth of 72.124 degrees. I'm guessing that if so, that was to allow lining up with the Moon's orbital plane without significant changes the S-IVB/Apollo stack's attitude prior to TLI after SECO.

 

[vogon13]

The moon doesn't really care from what direction you approach from, as long as you have a velocity appropriate for orbiting (if that be what you want to do) at the time you get there.<br /><br />Note the Apollo astronauts orbited the moon in a retrograde sense. (althought the moon rotates so slowly (~28 days) it didn't really affect the braking manuever too much (think about it).<br /><br /><br />The NASA brass were aware of the various launch timings available to the Soviets at their facilities more northerly location, and only had to watch for lunar launches at specific times. IIRC, there was a Soviet launch opprotunity prior to the Apollo 8 liftoff, and when the Soviets didn't use it, NASA knew they could 'win' with Apollo 8 if it was successful.<br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[henryhallam]

I haven't read the article, but I can't think of any reason why the Moon's orbital inclination should change significantly... it seems a bit counterintuitive to me, given the huge change of momentum that that would require.

 

[chode]

This effect is caused by the nutation of the orbit of the moon relative to the ecliptic. The moons orbit remains at a relatively fixed angle to the ecliptic plane (Earth's orbital plane), but the plane rotates with a period of about 18 years, due to the sun acting on the orbit. This nutation will cause the angle of the plane of the moon's orbit relative to the Earth's equator to change over an 18 year period. This doesn't mean that it is any more difficult or easy to reach the moon, as has been stated, it's more a matter of planning your trip so you intersect the moons orbit when the moon is there.<br /><br />Regards