How to change orbit?

[unnamedkid]

Just wondering how can I change orbit altitude nd attitude? Can I use RCS only to change the orbit?

 

[Urwumpe]

Just wondering how can I change orbit altitude nd attitude? Can I use RCS only to change the orbit?

1. By changing velocity vector at a position.

For example:
http://en.wikipedia.org/wiki/Hohmann_transfer_orbit

If you accelerate at a point (prograde burn), you increase the orbit altitude opposite of your current position.

If you decelerate at a point (retrograde burn) you lower the orbit altitude opposite of your current position.

If you change the direction of your velocity vector outside the orbit plane (Normal, Antinormal), you change the orientation of the orbit plane (inclination, LAN). If you change the direction of your velocity vector inside the orbit plane, you change the eccentricity, but keep orbit period.

A Hohmann transfer is a standard maneuver in Orbiter, so you should practice it from time to time and ideally learn how to estimate the fuel costs for such a maneuver. Also useful is learning to do a bi-elliptic transfer. It is similar to a Hohmann transfer, but saves fuel for bigger orbit changes.

http://en.wikipedia.org/wiki/Bi-elliptic_transfer

2. Yes, but much slower. For bigger maneuvers (>10 m/s velocity change) it is common to use main engines.

 

[martins]

Certainly, any force that induces a velocity change will modify your orbit. The problem with RCS is that the force is small, and therefore requires a long sustained burn, which is generally harder to calculate than a short high-thrust impulse burn (i.e. approximately instantaneous velocity change). Also, you may run out of fuel if you can't cross-feed from a larger propellant store.

 

[garyw]

I STRONGLY recommend printing out Go play in space and reading it. The document contains a lot of information on orbits and how they work.

 

[the.punk]

When you burn your main engines forward you get faster so your orbit changes to an elliptic orbit when you first where in a round low orbit. When you burn retrograde your PeA (lowest point of your orbit) gets lower when you first were in a round orbit. Same is for RCS thrusters...only smaller. And I also recommand Go play in Space.

 

[vonneuman]

I recommend this video [ame="http://vimeo.com/4718661"]DG4 to ISS: Orbiter Tutorial on Vimeo[/ame]
It is done by Tex. It explains a lot of the mechanics of space flight. Including how to change orbits, change orbital plain, and how to dock.

 

[Ark]

I recommend this video DG4 to ISS: Orbiter Tutorial on Vimeo
It is done by Tex. It explains a lot of the mechanics of space flight. Including how to change orbits, change orbital plain, and how to dock.

Great video, has all the basics of getting to the ISS, which is an important first step.

 

[vonneuman]

I know. I learned everything from this

 

[unnamedkid]

thanks guys!

 

[Keatah]

Look for the Orbital Operations Manual by Smitty. It is a basic manual that explains exactly how to change orbit size, eccentricity, altitude, attitude, planes, etc.. With the goal of matching orbits and stuff like the space station or something.

http://smithplanet.com/stuff/orbiter/orbitaloperations.htm

It has lotsa pretty pictures and illustrations that are relevant to the topic at hand. Believe me, if my girlfriend can understand this, then *ANYBODY* can..

 

[BRIGHAM]

Hi, its a so nice and good site ever. Its a really great and fantastic post here in this site. So, thank you for the sharing of your ideas and thoughts to all of us.

 

[rucinter]

A Hohmann transfer is a standard maneuver in Orbiter

Is this also true for, say, real Mercury, Gemini or Space Shuttle flights? Which transfer method is more conservative regarding fuel consumption?

 

[Urwumpe]

Is this also true for, say, real Mercury, Gemini or Space Shuttle flights? Which transfer method is more conservative regarding fuel consumption?

A Hohmann transfer is the most conservative maneuver possible and generally also the most fuel saving, since you only burn tangential (no gravity losses, all energy goes into changing orbit energy). The Shuttle actually uses mostly Hohmann maneuvers with tiny off-plane/radial components.

If you do large changes in semi-major axis (more than 11 times bigger or smaller the initial orbit radius, a bi-elliptic transfer is slightly more fuel saving (three instead of two burns, first burn exceeds the target or increases semi-major axis initially before lowering it).

 

[garyw]

Recommended reading as it talks about various rendezvous techniques that were tried out on the Gemini missions -> [ame="http://www.amazon.co.uk/How-NASA-Learned-Fly-Space/dp/1894959078/ref=sr_1_fkmr0_2?ie=UTF8&qid=1268299664&sr=8-2-fkmr0"]How NASA Learned to Fly in Space: An Exciting Account of the Gemini Missions Apogee Books Space: Amazon.co.uk: David M. Harland: Books[/ame]

 

[rucinter]

Wishlisted, thanks.