Orbit changes - equatorial to polar

[l3p3r]

Hi all! <br /><br />I'm curious about this... say you set yourself into an equatorial orbit (post launch, perhaps) but you want to change your orbit to a north-south polar orbit. Sure you could just burn loads of propellant to cull your EW orbital velocity and increase your NS orbital velocity - but are there any other maneuvers one could make to accomplish this? Like redirects around the moon / lagrange points etc?<br /><br /> <div class="Discussion_UserSignature"> </div>

 

[h2ouniverse]

Yes<br />Using the gravity well of another body is a very efficient way to transfer kinetic energy from orbital plane to the normal to the (initial) plane.<br />Jupiter is frequently used for that purpose<br />Was used e.g. for Ulysses probe.<br /><br />Another example: We also intend to use that for Solar Orbiter mission. The spacecraft will be placed in a 2:3 resonant orbit vs Venus. So after 3 orbits of spacecraft around the sun, Venus has made two so we meet again Venus and can have a GAM (Gravity Assisted Maneuver). Each GAM is used to increase inclination of the orbit (about the Venus-Sun axis) so that end of life we reach more than 30° of inclination. If it was not for operations cost and spacecraft lifetime, we could go his way up to 90°.<br /><br />Around Earth, this has been done with Moon already to recover from a launch failure (bad injection), this time the other way round. The telecom satellite Asiasat3 had its initial orbital inclination brought back to the equatorial plane for a clasical GEO operation.<br /><br />http://query.nytimes.com/gst/fullpage.html?res=9E0DE7DC1F3DF93AA25755C0A96E958260<br /><br />best regards.

 

[l3p3r]

Ah great thanks! <br /><br />I have trouble getting my head around these maneuvers! You don't know of any diagrams or animations that might describe that process, by any chance? <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>

 

[h2ouniverse]

I know Solar Orbiter pretty well so:<br />http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=27584<br />

 

[h2ouniverse]

They had made a video some time ago (mission profile is obsolete btw, no more electric propulsion, but still many GAMs vith Venus to incline the orbit, as on video)<br />http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=37441

 

[h2ouniverse]

To visualize that, think of Einstein's tensed elastic membrane with planet as a ball distorting the membrane. Sun is distorting the whole thing making a kind of cone locally.<br />You come with your tiny ball rolling on the membrane, on your elliptic trajectory around the Sun. As you approach Venus, you roll in Venus well and your trajectory is altered.<br />If you arrive in a plane that includes Venus center of gravity, you will not change plane inclination.<br />But if Venus CoG is not in your orbit plane, your velocity vector is going to be defelcted with an out-of-orbital-plane component = /> your i changes!<br /><br />Regards.

 

[3488]

STS 41 Discovery. Ulysses Launch.<br /><br />Ulysses Jupiter swingby, put Ulysses on a 80.2 degree inclination heliocentric orbit.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[l3p3r]

Thanks for all the info guys! Orbital maneuvers are fascinating <img src="/images/icons/smile.gif" /> <br /><br />That video was exactly what I was after thanks H20! =D <br /> <div class="Discussion_UserSignature"> </div>

 

[l3p3r]

Do you think it would be cheaper to do it like that, though?<br /><br />Obviously using the moon to change the inclination (or most of it) will take a long time... years maybe? <br /><br />edit:<br />I suppose there is also the question of the size of the orbit. If you want to use the moon to change your inclination you have to get out there first, and then once your inclination has been changed you'll need to lower you apogee again - would this end up requiring more energy than a brute force inclination adjustment like the one you suggested? <div class="Discussion_UserSignature"> </div>

 

[jimfromnsf]

"Obviously using the moon to change the inclination (or most of it) will take a long time... years maybe? "<br /><br />Not really. The HGS-1 spacecraft used the moon<br /><br />http://solarsystem.nasa.gov/missions/profile.cfm?MCode=Asiasat<br /><br />http://en.wikipedia.org/wiki/HGS-1<br /><br />Also <br />Supersynchronous transfer orbits are used by comsats to save fuel. The more efficient launch vehicle upperstage is used to put the spacecraft in a higher orbit than needed. The spacecraft does the inclination change and reduces the orbit down to GSO. <br /><br />There where plans of launching DOD GSO spacecraft from VAFB using bielliptical transfer orbits.

 

[h2ouniverse]

Yes, that was Asiasat3 initially.