Flight Question How to launch to reach an specific orbit?

[rcd463]

Hello

I had been "grounded" for a while and I am starting again with this wonderfull sim.

I had read a lot of posts, manuals, tutorials and all of them are talking about how to launch for a rendezvous with other vehicle or planet but I could not find what to do, how and why for an satellite insertion in an specific orbit.

I would like to deploy a Carina 2 satellite with the XR2 in an polar circular orbit at 250Km of altitude. So how can I do it if, for example, the LAN is 45º? How can I calculate the launch window? It is a polar orbit of 90º with the Ecuator so wich could be the best place for departure? (As northest as possible I think)

Sorry for my english (a little bit oxidaced) and thank you in advance.

 

[garyw]

You can go polar from anywhere because all you need to is fly north or south.

Launch windows for real missions factor in many things, for example, there are two launch windows to the ISS from Florida every day. In NASA's case, because of overflights of populated areas and TAL sites only an AN launch trajectory was used and because of the available dV of the shuttle the launch window was only five minutes long.

 

[ale131296]

I can help you in Spanish with private messages I don't know what are you going to do but I can help you if you are looking for a successful launch to an orbit with every inclination.

 

[kamaz]

The problem is that there are no tools for launching into desired orbit, only tools to for rendezvous operations (i.e. you cannot manually specify orbital elements, they must be taken from an existing spacecraft/moon). So just use a scenario editor to put a dummy target spacecraft in desired orbit and then follow any launch-to-rendezvous tutorial. (Basically, you launch north/south when target's ground path on MapMFD crosses your launch site, then do corrections as needed.) Note you don't actually have to rendezvous with target, just put yourself in orbit with the same SMi, SMa, Inc and LAN.

And you can use LaunchMFD [ame="http://orbithangar.com/searchid.php?ID=2802"]Launch MFD - v. 1.6.1 for Orbiter 2010[/ame]

 

[ale131296]

I prefer my methode: Think about a launch date with information from the tools that you got on Orbiter and know about the best orbit that you need. Stablish the launch date and wait until that date or going to the date with the Editor. Launch and if you practice that scenario in two hours your launch will be almost perfect.

 

[orbitingpluto]

Try this:[ame="http://www.orbithangar.com/searchid.php?ID=2464"]Azimuth calculator v. 1.5 - GUI[/ame]

It's a program external to Orbiter that calculates what compass heading you must launch towards to get the desired inclination. Just launch towards that heading, and a keep on eye on Orbit MFD's inclination value(remember to switch the frame in Orbit MFD to equatorial first though). Depending on what inclination your looking for and what latitude you are at, plus whether you are flying on the ascending node or descending node, that value will either grow or shrink- hopefully getting closer to the desired inclination. If it isn't, you have the option of yawing your ship off to one side to push your trajectory in the right direction, which is inefficient but can be done if you have the thrust and delta-v to spare; or you might have to start again and correct what caused you to go off course. So long as you aren't use the more restrictive settings though, the XR2 should be able to clean up a botched launch, so long as the mess up wasn't huge.

 

[STS]

Two good tutorials.

 

[rcd463]

Thank you for your help guys.

Azimut Calculator looks to be better than Space Calculator V2 because this one shows answers about -88º and the first one a northerly azimut.

Anyway the option proposed by kamaz was my first thought but it is not the way I thing it should be.

I supose that for launching a single satellite in a polar orbit the LAN does'nt matter but for a rendezvous with we need all parameters to reach it. Obiously the MFD will give us all this calculationes because it's in orbit but I would like to be as much precise as I can on the first launch.

Thank you again.

PD: I will use the Launch MFD and we will see what happen

 

[boogabooga]

Launch MFD is your friend.

LAN might matter for a polar launch for example if illumination from the sun is important.

 

[rcd463]

Launch MFD is your friend.

LAN might matter for a polar launch for example if illumination from the sun is important.

A very good reason. Thank you!!

 

[Ripley]

Probably related (still learning the basics), let's suppose this is the polar orbit today, where the ship is constantly lit by the Sun.

In 3 months from now, when the Earth will be 90° from its current location, the same orbit won't offer continous sunlight anymore.

So, if the particular mission needs constant sunlight, the orbit itself needs to rotate.
What is the parameter (orbital element) that must be considered?

 

[Urwumpe]

Important is the "Rate of change of the longitude of the ascending node" or "nodal regression":

The formula is on my user page in OrbiterWiki, I once formulated it there to be put into a proper article about non-spherical gravity and its effects:

http://www.orbiterwiki.org/wiki/User:Urwumpe

There is also a version that is already simplified for the constants of Earth, but I would need to find the lecture notes for that.

As you can see by that formula already, the most important number to control this nodal regression is the orbit parameter p.