OMS-2 burn.

[iam_inorbit]

Hi,

I am having Trouble Orbiting Earth. Some people here, said that "I need to circularize orbit, which requires a second burn (called an OMS-2 burn) on the other side of the planet from your launch site.

Can anyone tell me how should i orbit. Or give me link to any tutorial/Playback which can help me.

 

[Urwumpe]

Hi,

I am having Trouble Orbiting Earth. Some people here, said that "I need to circularize orbit, which requires a second burn (called an OMS-2 burn) on the other side of the planet from your launch site.

Can anyone tell me how should i orbit. Or give me link to any tutorial/Playback which can help me.

Look at this short and incomplete article about it.

http://www.orbiterwiki.org/wiki/Orbit_insertion

Otherwise: Read the BASIC tutorials, like "Go play in space" or this

http://www2.jpl.nasa.gov/basics/

 

[-Pv-]

I suspect based on many other posts you've made, you prefer the short answers posted here as opposed to the long answers you have to read the technical docs for. In Orbiter we can often give the 5 word answers to user interface and hardware considerations, but the sim itself is often quite technical and the long answer is the one that has fewer chances of requiring 20 questions and 20 answers, thus what you get in the end is the long answer.

An attempt to the short answer (I'm over-simplifying everything) for Shuttle Fleet craft flown manually (again I recommend the launch autopilot to start with so you can see how it should be done, then go manual) is:
1) Your initial orbit insertion will be slightly elliptical. No use hauling that big, empty external tank along, so we burn to circularize after we lose it.
2) Up ahead of you in the Orbit MFD circle along the path of your orbit (the green circle) is an open (non-filled) circle placed on your orbit circle. This is the "Apoapis" or highest point of your orbit before you go back around the back side and encounter the atmosphere at the filled (closed) "Periapsis" circle. You need to raise the periapsis close to the same altitude as the Apoapsis to "circularize" the orbit (get it high enough to don't fall back to Earth.)
3) By the time you get to Apoasis (I'm leaving out details here you understand) you need to use the Orbiter autopilot to turn Prograde and burn full throttle until the ApD and PeD are the same and/or Ecc is the lowest reasonable number (if you burn too long, the number will start to go up and you'll have wasted fuel.) If you think you might over-run this burn point before you are ready, pause the sim until you have it figured out then go for it. It's also good to save just after the tank is jettesoned so you can start from there as often as it takes to get it right.

If the short answer doesn't work for you, please refer to the suggested docs.
-Pv-

 

[iam_inorbit]

3) By the time you get to Apoasis (I'm leaving out details here you understand) you need to use the Orbiter autopilot to turn Prograde and burn full throttle until the ApD and PeD are the same and/or Ecc is the lowest reasonable number (if you burn too long, the number will start to go up and you'll have wasted fuel.) If you think you might over-run this burn point before you are ready, pause the sim until you have it figured out then go for it. It's also good to save just after the tank is jettesoned so you can start from there as often as it takes to get it right.

I Understood, Should i Burn the main engines during prograde and acc time to 100x

 

[FordPrefect]

I Understood, Should i Burn the main engines during prograde and acc time to 100x

That's right, though using time accel during burns is generally a bad idea. Burns are critical, as are the burn times, if you want to hit the numbers closely... unless of course you have a reaction lag of less than 1/1000 of a second.

 

[-Pv-]

I agree with the above. The burn is not that long that it cannot be done in real time. It will be over before you realize it. Most of us avoid warp when doing anything with the autopilot turned on, and I don't use anything above 10X with the AP on when I expect to be in AP mode a long time. 100X can work, but gets increasingly risky depending on what is happening. Might as well enjoy the show while you are learning. You'll get more out of it.
-Pv-

 

[iam_inorbit]

I am still unable to do this burn successfully. Alt of the shuttle is falling still. what should i do now. is there any playback,tutorials,pdf's anything for this.
:facts:

-Pv- = hey can you suggest how to raise "Apoapis" "periapsis" better way.

 

[tl8]

I am still unable to do this burn successfully. Alt of the shuttle is falling still. what should i do now. is there any playback,tutorials,pdf's anything for this.
:facts:

Can you get into a stable orbit with the DG?

 

[Yoda]

You know, ......it's not rocket science.......:rofl:
Pull up Orbit MFD, when you are on the oposite side of the globe from were you launched, press Prograde "[" and burn till the circle on the Orbit MFD shows a "perfect" circle around the globe.
( Kinda the abreviated unscientific way of doing it but it works).
Welcome to Orbit.

 

[HiPotOk1978]

hey can you suggest how to raise "Apoapis" "periapsis" better way.

my first question for ya iam, and by no means is this intended as an attack on you in any way what so ever intended to insult you so here it goes...

Do you understand what these things are... Do you understand what the various screens that you have at your disposal are telling you? Do you understand these terms such as prograde and apogee and perigee? If you don't you need to read and learn cause everything your going to want to do, you will be required to understand them and what they are.

If you are having a problem with understanding what the instruments are telling you, your gonna hate your experiences with orbiter. Learning the elements of the sim are something that you simply cannot ignore and learn after you do something cool (eg enter LEO). If you are set that you don't want to fly anything BUT the shuttle this is completly doable, your time to learn is going to be MUCH MUCH longer.

Go Play in space is by far (in my opinion of course) REQUIRED reading! Once you understand what the orbital elements are in OrbitMFD you can then learn to change them. Once you learn how to change them, you can learn how to do it more fuel efficently, and then change them to useful values to accomplish mission goals.

Now as far as learning, this site is a GREAT place to do so. I have asked several questions here, and granted most of them were answered with do this first in the DG, or read this info at this URL but those are valid helpful answers. If you have problems with establishing an stable orbit, listen to the advice of those that say for example with your questions you have posted, fly the DG first. Many people, including myself hate to type out these long posts containing infomation that was included with Orbiter or can be found on the web.

Now the DG or Delta Glider is a great way to have a ship that is EASY to fly, plenty of potential dV to do just about anything, and has the power to correct mistakes (that you and I and everyone else that has loaded up Orbiter Space Flight Sim have done, are doing, or will do) If the stock DG is too much for ya still, you may want to try Dan Polli's DGIV availiable at http://orbiter.dansteph.com/
This craft is neat in the fact it has built in auto-pilots to get you from surface of Earth to LEO. I learned a lot by watching the DGIV fly itself into orbit, including modeling my own manual ascents on the way that it flys.

In closing, This is a game of Rocket Science. and rocket science is hard. There are all sorts of terms and procedures and methods to accomplish something as simple as establishing a simple circular orbit around the earth

 

[-Pv-]

"I am still unable to do this burn successfully. Alt of the shuttle is falling still. what should i do now. is there any playback,tutorials,pdf's anything for this.
:facts:

-Pv- = hey can you suggest how to raise "Apoapis" "periapsis" better way."

There are tutorials and "PDFs" in the doc portion of the Orbiter Installation. There are playbacks and tutorials in your Orbiter if you installed the Shuttle Fleet. There are tutorials on the home page of this forum.

Study the Orbit MFD and you will understand what I said about "periapsis" (the lowest "I'm going to hit the Earth" portion of your orbit) and "Apoapsis" (the highest point of your orbit just after you shed the external tank and the green circle is furthest away from the grey circle [the Earth.]) I'm not going to write a book which is the next step in explaining what you need to know.

One of the reasons many people try to explain things in here is it's a permanant record uncounted numbers of people can read in the future so we don't have to type it again and again (thus the resistance to type it again and again.) You'll be amazed what you find if you use the search feature of this site. I bet you'll find someone who has already explained better and 40 different ways than what you have seen so far.
-Pv-

 

[Rathelm]

Another thing I don't think anyone mentioned, but might help, is when you are looking at the Orbit MFD hit the PRJ button to switch the mode from "ECL to ECL" to "ECL to SHP". It will give you a "top down" view of how your orbit looks and you might with a few failures understand what exactly is going on.

 

[Tommy]

Also, it may help to press the DST button on OrbitMFD. That will change from Radial measure (distance from the planet's center) to Altitude (distance above the planet's surface). If OrbitMFD shows a line for ApR, you're in Radial mode. If it shows ApA, you're in Altitude mode.

Altitude mode is a little more intuitive, and easier to understand exactly what is happening.

If you are falling back down, it means you aren't going fast enough. Orbital velocity for LEO is around 7.5k m/s. You need to make a longer OMS-2 burn. It's possible that you got your Ap up high enough without gaining enough orbital speed, and the OMS can't increase your speed enough to raise the Pe above the atmosphere. If that's the case it means your initial ascent was too steep.

 

[iam_inorbit]

Thanks, now i can do oms-2 burn, thanks for your help.