Problem Apollo 8 TLI Problems

[tomas2]

Hey everyone, i am doing the Apollo 8 basic mission to the moon from NASSP (I've completed Apollo 7 with little problems). And I keep running into a problem executing my TLI Burn, the SIVB orientates itself towards the earth than burns (Causing it to re-enter ). I think the problem is when I am setting up the burn, i am not sure to set both GET the same (69:13:58) or should they be different after I set up the burn (MFD 1: 70:36:19 and MFD 2: 69:13:58 as they are in the picture below), would this be the problem, if so how can i fix it? Or have I forgotten to do some checks from the checklist?

P.S The PeA is supposed to be -241.1k but this is a screenshot from before I fixed it

 

[MJR]

It is way easier to use the Transfer MFD and Orbit MFD. Are you sure that your orbit is a complete one and your PeA is really low? Make sure that you have the switches one for roll, yaw, and pitch, then orient prograde.

 

[tomas2]

Hey MJR, my PeA even though it is relatively low (184.3k) it is still stable and above most of the earth's atmosphere. And the Apollo 8 mission flight plan says to use the IMFD for precise maneuvers, etc. Even though using way you stated is way easier . And I have checked and the roll, yaw, and pitch switches are set to their correct positions.

 

[MJR]

Give me all the steps that you did leading up to the TLI and during the TLI so I can see if you did anything wrong.

 

[tomas2]

Give me all the steps that you did leading up to the TLI and during the TLI so I can see if you did anything wrong.

Oh boy this is going to take a while (i did everything the checklist said)

1) Launch 000:00:00 -No problems-Followed checklist
2)Insertion-No problems-Followed checklist
3)Did my 1st System Check- Had some issues with the ECS checks (some things were not working properly, but most likely wouldn't effect TLI)
4)I began to set up for the TLI, using the IMFD program
5)I used the Project Apollo MFD to orientate the SIVB to the "Proper" position but it orientates itself downwards towards the Earth than burns (causing early re-entry )

(Since this is the basic scenario, i just used the checklists) (this is a simplified version of what i did, because it would take forever to write all of the information of what i did )

 

[MJR]

Oh boy this is going to take a while (i did everything the checklist said)

1) Launch 000:00:00 -No problems-Followed checklist
2)Insertion-No problems-Followed checklist
3)Did my 1st System Check- Had some issues with the ECS checks (some things were not working properly, but most likely wouldn't effect TLI)
4)I began to set up for the TLI, using the IMFD program
5)I used the Project Apollo MFD to orientate the SIVB to the "Proper" position but it orientates itself downwards towards the Earth than burns (causing early re-entry )

(Since this is the basic scenario, i just used the checklists) (this is a simplified version of what i did, because it would take forever to write all of the information of what i did )

Did you follow the checklist to activate the SIVB RCS?

 

[tomas2]

Yes i did, the only thing I did not do is: TVC SERVO POWER 1 - AC1/MNA




---------- Post added at 01:32 PM ---------- Previous post was at 12:59 PM ----------

I have redone the mission (from Launch to TLI) and still the SIVB is orientating itself towards the Earth than burns Is it possibly the scenario?

 

[Tschachim]

This might be a version incompatibility problem, which NASSP version (beta modules pack date) and which IMFD version are you using?

Cheers
Tschachim

 

[tomas2]

The NASSP version I'm using is ProjectApollo_Beta_20090322
And the IMFD Version im using is IMFD 5.1

 

[Tommy]

This may be a problem with trying to burn to soon. This can happen when using a "predetermined" GET that may not be correct for your particular flight. After you've achieved your parking orbit and set up the course using Target Intercept open the "Orbit Eject program, and set it to "course" rather than "Higher Orbit". Check the GET for the ejection burn, and use that time to perform your TLI.

 

[Tschachim]

Then you need to update to the latest IMFD version or use LunarTransferMFD as it's better for TLI anyway (and supports ProjectApolloMFD in the same way): http://koti.mbnet.fi/jarmonik/Orbiter.html

Cheers
Tschachim

 

[tomas2]

Ok thank you everyone for your help
I am now on my way to the moon with Apollo 8! (using the Lunar Transfer MFD , even though I had to change the GET so I would not burn in the atmosphere )

Thank you

 

[tomas2]

Ok I have not made it to the moon, I missed by 22M! :embarrassed: The reason being when I launched the launch autopilot (the one that comes with NASSP) it launched me into orbit with a RInc of 55 degrees. How do I fix this with the limited amount of fuel that I have? Or have I done something wrong with my planning and the orbit is supposed to be like this?

Thank you

 

[MJR]

You are way off plane with the Moon. You have to set up a better plan. I haven't went lunar in forever so I don't remember much.

 

[tomas2]

You are way off plane with the Moon. You have to set up a better plan. I haven't went lunar in forever so I don't remember much.

But how can I do this with the Apollo Computer? :huh: I have made dozens of trips to the moon with none Apollo style vehicles, i usually just used the Align MFD and Transfer MFD, but I don't know how to do it with the Apollo Capsule (without running out of fuel )

Thank you

 

[Tschachim]

Could you post/attach a scenario saved after you set up the burn in LunarTransferMFD so I can take a look?

Cheers
Tschachim

 

[tomas2]

Could you post/attach a scenario saved after you set up the burn in LunarTransferMFD so I can take a look?

Ok here it is :

 

[Tschachim]

Thanks for the scenario, it looks like there's a kind of bug in LunarTransferMFD, I need to talk with Jarmo about that.

Meanwhile you can use IMFD 5.3b as it seems to work fine, I attached a scenario with a burn already set up in IMFD. But I didn't set up the offsets, so you'll crash directly into the Moon...

Cheers
Tschachim

 

[jarmonik]

What's the problem. I tested the scenario and couldn't find anything wrong. After TLI, altitude of lunar flyby was -260k when -240k was targeted.

P.S. Non-spherical gravity sources must be enabled from launchpad.

 

[Tschachim]

Hi Jarmo,

wow, thanks for the fast reply! :speakcool:

I just wrote you an e-mail:

The problem is that after requesting the burn data the first time, the S-IVB changes it’s attitude according to that. Because the S-IVB has attitude thrusters only at its rear end, there’s a rather huge “translational component” during that manoeuver, that means the S-IVB changes it’s orbit slightly. After the manoeuver, the S-IVB requests the burn data again with the hope to get new burn data w.r.t. it’s now-current orbit. Then it changes its attitude again according to that, requesting again and so forth for a couple of times.

With IMFD (including 5.3b) this is working fine, but LTMFD seems not to update its burn data when the S-IVB is manoeuvring. Did I anything wrong or is that really the case and would it be possible to change that?

Cheers
Tschachim