Atlantis Launch Tutorial

[SpaceMonkey]

Hello

Just recently got into orbiter - done all the DG tutorials and that's fine. I'm trying to do one of the standard scenarios in the Atlantis set. I can't seem to be able to reach a stable orbit from the launch pad, as I never build up enough speed to reach orbital velocity. I get up to about 80km at peak and just fall to Earth on a ballistic, ending up in the Atlantic.

All the Orbiter launch tutorials seem to be about the delta glider, and the NASA launch guidelines I've found I can't really follow to the letter as there is a lot of fly-by-wire operations in there.

Could anyone provide me with either an idiot-proof step-by-step guide, or a link to one? In particular, useful points would be things like:

What pitch should I be flying at for any given point in the launch? I've tried everything from 90 down to 45, tried starting at 78 and gradually levelling out over the launch too - which is what the NASA guides appear to say

When is the right time to ditch the tank?

Apologies if this was on the old forum - I'm not a member of that one

Thanks

 

[Andy44]

On the Orbiter M6 forums there is, or used to be, a sticky thread in which I posted a tutorial for manual shuttle launches about a year or 2 ago. It includes a pitch schedule. See if you can find it when the M6 is back up.

If you can't find it, here's how I built it:

Launch one of David413's shuttle fleet ships using the autopilot.

At intervals along the way, pause the sim and write down the altitude and pitch angle. Be sure to include key milestones such as throttle-down and throttle-up for max Q, SRB sep, etc.

I recorded my intervals at 1 km intervals up to about 10 km, and every 10km thereafter. Your mileage may very. As you approach MECO the pitch schedule becomes less important than controlling the vertical velocity.
Once you've got a good list you can cue yourself off it and do it manually. Keep an eye on things like vertical velocity and max acceleration, too.

After a few times you'll be able to do it without notes.

 

[Hartmann]

My problem is when i leave the launch pad, how orient the shuttle to the correct pitch and roll, i reached orbit but is difficult did it in the correct way

 

[Andy44]

Hartmann, try this: while sitting on the launchpad and for a few seconds as you begin the launch, set the HUD to orbit mode. You will see the arrow showing your motion in inertial space; this points to the east when sitting on the ground. Think of that as 90 degrees and do you're roll maneuver based on that as a reference. It won't be perfect, but until somebody makes a HUD modification addon, it's all we got. Once you get in the ballpark of your desired launch heading, start your pitch maneuver and roll/yaw as necessary to get on the proper course.

The real shuttle starts pitching and rolling at the same time, and so does David413's autopilot; for a manual launch this is a bit much to ask of an Orbinaut, so I recommend rolling quickly first following by pitchback.

 

[myles]

I like on the Surface HUD, you can see the numbers up top and that shows your heading, and you don't have to squint your eyes to see it, and the spaces are bigger, therefore it is more accurate.

 

[Cornflake]

If you can't find it, here's how I built it:

Launch one of David413's shuttle fleet ships using the autopilot.

At intervals along the way, pause the sim and write down the altitude and pitch angle. Be sure to include key milestones such as throttle-down and throttle-up for max Q, SRB sep, etc.

Haha, I did the exact same thing and was going to recommend it to SpaceMonkey :lol:. That reminds me, i forgot to write down throttle down and throttle up times. What is considered the max G you encounter during throttle down times?

Ok SpaceMonkey, here's the notes I use that I recorded from a Shuttle Fleet launch, it works well for me. It may not be detailed to the 1km at first like Andy44 does, but by the time I get my roll straightened out I'm at like 8km:

T + ~15 sec - begin roll
T + ~30 sec - end roll
At launch, fly vertical until done with roll.
Then, pitch to ° by the time your altitude reaches noted km:
60° - 7.6km
50° - 14km
40° - 20km
30° - 26km
20° - 37km
15° - 40km ~ SRBs will separate
Hold 15-20° until height is about 90km
Attemmpt to maintain zero vert. speed by ~110km

After ~110km:
- Gain speed while holding zero vert speed
- If your vert speed increases / decreases, pitch nose down / up to compensate
- Once your ApA (Apoapsis altitude) reaches your desired height, eg 300km, cut your engines. Then, wait until you orbit to your apoapsis then burn prograde to raise your PeA (basically orbit circulization).

As for the roll, that's tough. What I do, is look at the exterior of the shuttle, nose-on. I roll right until my stabilizer fin is pointed roughly in the direction I want to go in (You're ET is facing north, and tail fin pointed south on the launch pad). Then, I pitch down, and as I pitch down I look at my Surface MFD / Surface HUD compass and yaw and roll to get my desired heading, and have wings parallel to the ground. I do that all while trying to follow the guidelines for pitch. It's tough, but after a few tries you will get the hang of it.

Oh and as for the tank, if I have a few percent left in it after reaching orbit, I leave it on to help me dock with the ISS, etc - But in reality I believe this is done just after MECO, right after orbit is established.

Hartmann, try this: while sitting on the launchpad and for a few seconds as you begin the launch, set the HUD to orbit mode. You will see the arrow showing your motion in inertial space; this points to the east when sitting on the ground. Think of that as 90 degrees and do you're roll maneuver based on that as a reference. It won't be perfect, but until somebody makes a HUD modification addon, it's all we got.

Hmm I'll have to try that - never noticed it's pointed east when sitting on the ground.

I like on the Surface HUD, you can see the numbers up top and that shows your heading, and you don't have to squint your eyes to see it, and the spaces are bigger, therefore it is more accurate.

Yeah, but until you start pitching, it doesn't really know which way you're pointed.

 

[cjp]

Also, don't forget to enable the limited fuel option. The fuel tank needs to become more empty during launch, because a full fuel tank is simply too heavy to be lifted after SRB separation.

This might just be your problem if you can launch other vehicles perfectly, but just can't get the Space Shuttle into orbit.

 

[Andy44]

Oh and as for the tank, if I have a few percent left in it after reaching orbit, I leave it on to help me dock with the ISS, etc - But in reality I believe this is done just after MECO, right after orbit is established.

Very unrealistic. The real SSMEs cannot be restarted once they are shut down! The sequence is set in stone. A few seconds after MECO the ET gets jettisoned. OMS is for orbital maneuvering.