Question about launchers

[holmec]

As far as I understand, rocket launchers commonly take satellites and ships to certain orbits and inclination.<br /><br />Also I understand that the majority of launches are for geo-syncronous orbits, which is mostly along the equator (ie geostationary -- edited).<br /><br />So what happens when a satellite needs a polar orbit or some strange inclination? Does the upper stage compensate or does the whole launcher need to be 're-calibrated' for a such a inclination? <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[jimfromnsf]

Don't really understand the question.<br />The flight software is changed so that the LV flies to the required orbit. It changes the azimuth the vehicle flies to and the number, length and direction of the upperstage burns<br /><br />For a Delta II, the 3rd stage is omitted for LEO or PEO orbits and it is traded for payload mass. For vehicles, like Altas V and Delta IV, those vehicle's upperstages just burn longer into LEO and don't have another burn for GTO.<br /><br />there are different environments, especially US launchers that have to use CCAFS or VAFB, for the different missions and the LV's have to be able to handle them

 

[holmec]

Thanks Jim.<br /><br />You answered it. The LV takes the payload directly to orbit. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[propforce]

<font color="yellow">what happens when a satellite needs a polar orbit or some strange inclination? Does the upper stage compensate or does the whole launcher need to be 're-calibrated' for a such a inclination? </font><br /><br />Another way to look at this explain the difference between launching from the Cape vs. from VAFB.<br /><br />For orbits that circulate about earth around the equator, such as the GEO, MEO and LEO (somewhere near zero deg inclination), you'd want to take advantage of earth's rotation as much as possible. Therefore the advantage is launch from as near equator as possible and launch it toward "east". This saves the launcher propellant mass which can be used toward the spacecraft mass delivered to orbit. <br /><br />But we don't have a launch site exactly located at the Equator. If we have, this will save us 1,520 feet/sec of velocity. The closest U.S. launch site is the CCAFS (cape canveral, Florida) but it only save us 1,336 ft/sec because it's located at 28.5 deg instead of zero degree as on the Equator. The French Arianne launch from Kourou, a launch site at the French Guiana in northeastern south america. Its inclination is only 5.5 degree so it has a 177 ft/sec of velocity advantage over launches from CCAFS.<br /><br />That is also another advantage of Boeing Sea Launch has. It just goes to the equator south of Hawaii and launch the rocket from there, capturing the maximum advantage of earth's rotational velocity.<br /><br />Now for payloads (that's what launchers call the spacecrafts) that goes to geosynchronous orbit (GEO), such as commercial communication satellites, there're 2-ways of getting there. The first and, the most common way, it that the launcher delivers the payload to a <i>geostationary transfer orbit</i> (GTO). The spacecraft takes a several hours coast to GEO, once it gets there, it fires its smaller rocket giving it sufficient velocity to "circularize" the orbit and stay there.<br /><br />The second way to get <div class="Discussion_UserSignature"> </div>

 

[holmec]

Thanks. <br /><br />The PAM is what I was after. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[henryhallam]

They're easily confused, but actually a geo<i>synchronous</i> orbit is any which has a period of 23h 56m (one sidereal day). A satellite in such an orbit returns to the same point over the Earth's surface at the same time each day.<br />A geo<i>stationary</i> orbit is a special case of a geosynchronous orbit, which has zero equatorial inclination and zero eccentricity. A satellite in geostationary orbit stays at the same point over the Earth's equator all the time.<br /><br /><img src="/images/icons/wink.gif" /> *mutters about fuel vs propellant*

 

[henryhallam]

Very well thanks - I'm taking a course in Astrodynamics from Dr Richard Battin, who developed many of the navigation techniques for Apollo and played a large part in designing software for the AGC. Still struggling with foot-pounds and horsepowers.<br />Hope things are well in Florida!

 

[chode]

Wow, Dr Battin is still teaching courses at MIT. Good to see another Apollo pioneer still around to pass the torch. <br /><br />P.S. If you get a chance, could you ask him if he has any source code listings of Colossus or Luminary sitting around. There is a small, but determined group of Apollo AGC nuts who are attempting to create a "virtual" AGC, that simulates the workings of the AGC using modern computers. "Authentic" source code listings are hard to find!<br /><br />Regards

 

[henryhallam]

I will do that! Do you have an email address I can pass on to him if he finds something useful?

 

[edkyle98]

<blockquote><font class="small">In reply to:</font><hr /><p><br /> I understand that the majority of launches are for geo-syncronous orbits, which is mostly along the equator.<br /><p><hr /></p></p></blockquote><br /><br />In recent years, it hasn't been a majority. This year to date, for example, there have only been 15 geosynchronous launch attempts out of 40 orbital launch attempts overall. Last year it was 32 out of 66. It was 23 out of 55 in 2005, and so on. Low earth orbit missions typically make up the largest share of orbital types.<br /><br /> - Ed Kyle

 

[MeteorWayne]

THere are only so many geostationary slots available, so until a spacecraft runs out of propellant, most of the slots are full. <br /><br /> educational article on Geosyncronous and Geostationary satellites <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>