Need help getting to orbit with OMS burns

[Flights]

I have another question about the Space Shuttle Ultra. This time I'm asking about how to perform OMS1 and 2 burns to get to orbit. After ET separation, I need to know what to do next. I've read the manuals that come with the addon, and I've read other posts on the forums but I can't figure out why the OMS engines won't fire! I make sure the OMS switches are set to ARM/PRESS. I understand that the data needs to be computed into CRT MFD but that's one thing I can't figure out how to do. How do I enter the data into CRT and then perform the burns?

 

[Urwumpe]

The process is explained in detail in the NASA flight data files (also known as checklists)

DPS Dictionary
ORBIT OPS (Page 9-2)

The display works pretty simple. You enter the target data (velocity change vector, ignition time) into the fields of PEG7 (or get default data presented, that was loaded into the computer before launch) and then "load" the data (ITEM 22 EXEC). This makes the computers calculate how to achieve this change in velocity. Next, you start the timer (ITEM 23 EXEC), which displays a countdown in the right corner of the CRT. Next you check the burn solution, write it down on your MNVR PAD and then confirm if you want the computers to execute this burn by selecting MNVR (ITEM 27 EXEC) . Now, the Shuttle will turn for the burn.

From T-15 seconds on, you need to press EXEC to give the computer go for the OMS burn. If you miss it, nothing will happen.

 

[Flights]

The display works pretty simple. You enter the target data

That's my problem. I can't figure out how to "enter the target data." I can't find a simplified reply on how to enter the required data into CRT.

 

[DaveS]

That's my problem. I can't figure out how to "enter the target data." I can't find a simplified reply on how to enter the required data into CRT.

Just use the CRT keyboard(s) on the center panel console.

 

[Flights]

But how do I enter the required data (the velocity and the attitude and TIG) for the OMS burns? Could it be that my modules are corrupt or something?

 

[DaveS]

But how do I enter the required data (the velocity and the attitude and TIG) for the OMS burns? Could it be that my modules are corrupt or something?

You click on the actual CRT keyboard keys in the VC. Make sure that CRTMFD is open in one of the three "CRT" MDUs on panel F7.

If you open CRTMFD in CRT1, one make sure that the switch "LEFT CRT SEL" is set to 1. This switch controls which CRT receives the input from the left CRT keyboard. It can either be CRT1 or CRT3.

 

[Flights]

Ok I know how to use the keypad. What I'm trying to ask is how to enter the required parameters for orbit? In my CRT MFD on OMS1 MNVR all the items read 0. Heres a screenshot:



You can see how all the fields say 0. What do I enter into the keypad to set those to the proper parameters for OMS burn?

 

[DaveS]

Ok I know how to use the keypad. What I'm trying to ask is how to enter the required parameters for orbit? In my CRT MFD on OMS1 MNVR all the items read 0. Heres a screenshot:

View attachment 10921

You can see how all the fields say 0. What do I enter into the keypad to set those to the proper parameters for OMS burn?

You enter them as ITEMs. Like this for a TIG of MET 38 minutes and 37 seconds: ITEM 10+000+38+37 and then finish with EXEC (Execute)

I suggest that you read the Shuttle Crew Operations Manual (SCOM): http://www.nasa.gov/centers/johnson/pdf/390651main_shuttle_crew_operations_manual.pdf

 

[Flights]

Yes! Thank you! That's exactly what I was looking for! Now I can get to successful orbit! Thanks!

 

[Urwumpe]

Yes! Thank you! That's exactly what I was looking for! Now I can get to successful orbit! Thanks!

Remember to use the PEG7 parameters in SSU, not the PEG4 - not sure if these had been implemented yet, they are only needed for AOA aborts or off-nominal deorbit burns.

 

[SiameseCat]

Remember to use the PEG7 parameters in SSU, not the PEG4 - not sure if these had been implemented yet, they are only needed for AOA aborts or off-nominal deorbit burns.

PEG4 has been implemented. I think it's actually used for nominal OMS-1/OMS-2/deorbit burns.

 

[Urwumpe]

PEG4 has been implemented. I think it's actually used for nominal OMS-1/OMS-2/deorbit burns.

Not for the nominal OMS-1/OMS-2 burns. I am also not sure about the de-orbit burn there, I do know that the PEG4 parameters appear in the various AOA abort paths.

 

[romanasul]

I also have a question regarding the Delta V target for the OMS burn or orbital burns. How do you know what Delta V to enter in feet per second and in what direction? Also, I'm having trouble understanding how to control the autopilot. For example, how do you point the ship prograde for a burn? Well in any direction for that matter. Can you control the attitude manually?

 

[SiameseCat]

You have to calculate the DeltaV manually. Note that the +X axis points in the direction of the velocity vector, the +Z axis points down (toward the center of the Earth) and the +Y axis points out-of-plane (in what Orbitersim considers the anti-normal direction).

One you've entered the burn targets (ITEM 22), the required burn attitude will be computed; entering ITEM 27 will maneuver the shuttle to the correct burn attitude. The MM 201 UNIV PTG display can be used for general attitude control; it lets you hold a target inertial or LVLH attitude.

If you haven't done this already, you should take a look through the documents at http://www.nasa.gov/centers/johnson/news/flightdatafiles/index.html. The SCOM (Shuttle Crew Operations Manual) and the Data Processing System Dictionary are particularly useful. The checklists should tell you what is happening at any point in the mission (although a lot of stuff isn't simulated in SSU yet).

 

[romanasul]

You have to calculate the DeltaV manually. Note that the +X axis points in the direction of the velocity vector, the +Z axis points down (toward the center of the Earth) and the +Y axis points out-of-plane (in what Orbitersim considers the anti-normal direction).

One you've entered the burn targets (ITEM 22), the required burn attitude will be computed; entering ITEM 27 will maneuver the shuttle to the correct burn attitude. The MM 201 UNIV PTG display can be used for general attitude control; it lets you hold a target inertial or LVLH attitude.

If you haven't done this already, you should take a look through the documents at http://www.nasa.gov/centers/johnson/news/flightdatafiles/index.html. The SCOM (Shuttle Crew Operations Manual) and the Data Processing System Dictionary are particularly useful. The checklists should tell you what is happening at any point in the mission (although a lot of stuff isn't simulated in SSU yet).

Thank you for your response, I'm also wondering if the space shuttle ADI is simulated within this addon. Because there is no way to tell your current attitude in the virtual cockpit.

 

[SiameseCat]

The ADI is not simulated yet. Surface MFD has an artificial horizon, which should work for most purposes.

 

[Goth]

I'm following the checklist in "Doc\Space Shuttle Ultra\Flight Checklists.doc" and also what is being written in this topic.
I'm after MECO and I have to do the OMS burn.
I insert all the required items (the CRT confirms that I did it correctly) and then I do:

ITEM 22 EXEC

Everything seems fine and the countdown starts.
Then I do:

ITEM 27 EXEC

but the shuttle doesn't change its attitude.
When the counter reaches zero the engines don't fire.

I pressed EXEC when T-15 seconds too as suggested by Urwumpe.
APU is ok. Both OMS ENG buttons are ARM/PRESS.
MPS ENGINE POWER are all ON.

Possible reasons?

 

[Urwumpe]

Wrong DAP mode?

 

[Loru]

Maybe it just needs a push

 

[Goth]

Wrong DAP mode?

What's the correct mode for this phase?