This goes by itslef since most of the mission is in atmospheric flight, part of the mission is in space ( higher than 100km) but none of the mission is in orbit.

As a starter and to show how realistic Orbiter is, SpaceShipOne is one of my favorites. I tried it with my students, making a contest to see who would be the first to reach 100km to win the X prize ( in their case a trip in the classroom simulator was the prize). In Orbiter, you will hear original radio chatter ( want proof, watch this video before you try the mission)

This mission is availbe in my standard 2006 pack.

Use the first mission, just prior to release.

You start in the White Knight, you must pres CTRL + J  to jettison SpaceShipOne

Once automatically transferred to the SS1, press the + on the numpad and right control key to get engine at full power, while holding the +, press the CTRL key to lock the engine at full power. If you have a joystick just throttle down then up to start the engine..

You can then use the insert/delete to adjust trim (just a little bit) to slowly raise your nose ( I go up somewhere between 70 and 80 degrees) . Careful, once you start to leave the denser part of the atmosphere, it becomes quite easy to lose control and get into a spin. (That really happened on one of the flights) . When dynamic pressure becomes zero, press K to open up wings. On the way back down, press K again at 20km altitude. Drop your nose until you get your speed vector ( circle with cross in it) in front of you and then  pull back to get of gentle glide path that will get you to the runway.

Hint:  Wait a bit before pressing CtRL+J because you are quite far from the runway which is straight ahead. 150-200s mission time is OK. Keep White Knight level, you might even get a bit more horizontal speed before separation. Every little bit helps.

 You can check out the pdf in our documents section for all control keys.

Also, get the transparent crew texture here and put it in your textures folder. (Backup your original !)