Centaur G/G Prime High Energy Upper Stage

[DaveS]

Have to start this thread over as I deleted the original thread by accident.

The Centaur G/G Prime was two versions of the Centaur upper stage which today is flying on the Atlas V EELV. In this case, it was modified to be able to be launched on the Shuttle. The LH2 tank was enlarged from it's normal 10 ft diameter to 14 ft.

The primary difference between the G version and G Prime version was the LH2 tank length. The G version was 20 ft in length leaving 40 ft available for payloads. This was the version intended for GEO payloads.

The G Prime was the larger version at 29.6 ft leaving 30.4 ft available for payloads. This was the version intended for NASA interplanetary payloads such has Galileo, Ulysses and Magellan.

Only the G Prime version was ever constructed prior to the Challenger accident.

To house the Centaur in the payload bay of the orbiter, a special support system was designed, called the Centaur Integrated Support System (CISS).

The CISS carried the Deployment Adapter and the cryogenic plumbing used to support the Centaur stage while it was in the payload bay.

A special umbilical system was designed and constructed to service the Centaur hydrogen system, providing fill/drain and venting of the hydrogen tank. This umbilical system was called the Rolling Beam Umbilical System (RBUS).

 

[DaveS]

With the technical description out of the way, here's the Orbiter-relevant parts.

 

[DaveS]

Nearly done with the Centaur G Prime. However, I have run into a problem with the CISS, namely creating a clean animation of the CISS LH2/LOX service pipes.

The problem more closely explained is that the pipes become disjointed when the Deployment Adapter is rotated to the 45° deploy position. I have attached a screenshot of the problem.

Any ideas?

 

[Urwumpe]

Are there no flexible joints in the pipes?

 

[DaveS]

Are there no flexible joints in the pipes?

Unknown. There's no photos of the CISS duct work other than on two scale models. Photos of one can be found here: http://forum.nasaspaceflight.com/index.php?topic=2398.msg584118#msg584118

According to the poster in another post (http://forum.nasaspaceflight.com/index.php?topic=2398.msg584236#msg584236), the pipes on the Centaur scale model itself is incorrect (the GH2 vent line for example doesn't have a Y manifold). So the accuracy of the CISS scale model is in doubt.

And here's a photo of the other scale model showing a different layout: http://forum.nasaspaceflight.com/index.php?topic=6479.msg544662#msg544662

 

[Urwumpe]

Well, judging the big one on display: What if there is a disconnect between the rotating ring and the fixed part of the service structure? Essentially, you need to disconnect the pipes between ring and fixed CISS, with two disconnect valves, before you can display the stage.

 

[DaveS]

Well, judging the big one on display: What if there is a disconnect between the rotating ring and the fixed part of the service structure? Essentially, you need to disconnect the pipes between ring and fixed CISS, with two disconnect valves, before you can display the stage.

I could try that. Right now I'm going by the smaller scale model as it seems to be more accurate judging by the pipes on the Centaur.

I'm trying to get ahold of the the document mentioned in those posts, but it seems like Jim hasn't managed to dig it up yet after a recent move.

 

[Urwumpe]

I could try that. Right now I'm going by the smaller scale model as it seems to be more accurate judging by the pipes on the Centaur.

I'm trying to get ahold of the the document mentioned in those posts, but it seems like Jim hasn't managed to dig it up yet after a recent move.

I just tried finding somebody who might have the company archives of Convair, but after getting merged with GD Space Systems, it is completely lost.

 

[DaveS]

Here's two screenshots of the CISS with the Deployment Adapter is the 0° position. Where would you place the the disconnects? Please indicate with a thick line.

 

[tl8]

Try the maroon line. That way the pipes should swing clear.

 

[Urwumpe]

Looking at one of the more detailed models, I think there is a small coincidence, that your mesh does not have: The bend pipes between the fixed part and the rotating part are exactly bend around the rotation axis of the CISS.

What if the bend pipes telescope into each other?

It just doesn't fit to the NASA drawings... or the pipes are flexible. But that is pretty strange.

 

[DaveS]

Try the maroon line. That way the pipes should swing clear.

Tried this, no luck. It gets disconnected and causes a leak. I guess this project will be stalled until some accurate data comes our way.

 

[Urwumpe]

Tried this, no luck. It gets disconnected and causes a leak. I guess this project will be stalled until some accurate data comes our way.

I would say then, just waiting for the data to come around is not good...better we actively search out the data and hunt it.

 

[tl8]

Tried this, no luck. It gets disconnected and causes a leak. I guess this project will be stalled until some accurate data comes our way.

Sorry, I thought you were asking for that. Basically, if the pipes do not disconnected, at least part of the pipe will have to be flexible. As the pipe does not pass through the centre of rotation, there is no simple rotating joint.

The best way to find the best spot would be to model it.

If you want I can make a small Lego model to see if I can find the right spot where it needs to be flexible.

 

[DaveS]

Here's a photo of the Centaur G Prime in the CISS in the Shuttle Spacecraft Processing Facility (SSPF) at the Cape. Side seen is the +Z side. Interesting note is that the the propellant tanks are entirely covered with a radiation shield foil.

 

[Urwumpe]

Doesn't look like flexible pipes there, but they seem to pass much closer to the rotation joint as in the models.

 

[DaveS]

Doesn't look like flexible pipes there, but they seem to pass much closer to the rotation joint as in the models.

Well, given this is the +Z (zenith) side and the problem is on the -Y (port) side, we're not seeing the problem area, it is in the shaded part of the CISS.

And comparing the locations of the pipes on the model and the pipes on the CISS in the photo relative to their respective Deployment Adapters, they seem to be about the same. Model referenced is the smaller one, of the Centaur G not the larger G Prime scale model with Galileo.

---------- Post added at 09:37 AM ---------- Previous post was at 05:42 AM ----------

Some technical data I have managed to dig up on the Centaur G Prime:

CISS/Centaur sep velocity: 0.3 m/s
Centaur Attitude Control System: 12x27 N, 77 kg propellant capacity tank
Centaur Main Propulsion System: 2xRL-10-3-3A 36700 N, 4379.184 m/s
Propellant maximum capacity: 19438 kg
Centaur G Prime dry mass: 2605 kg

 

[tl8]

Doesn't look like flexible pipes there, but they seem to pass much closer to the rotation joint as in the models.

Agree about the flexible pipes. There looks to possibly be a QD on the last straight before the Centaur.

Other than that, I would almost expect a QD where I marked it earlier. If you use valves, that should seal it for long enough.

 

[DaveS]

Source document for the above data: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19840024341_1984024341.pdf

---------- Post added at 10:18 AM ---------- Previous post was at 09:52 AM ----------

Agree about the flexible pipes. There looks to possibly be a QD on the last straight before the Centaur.

Other than that, I would almost expect a QD where I marked it earlier. If you use valves, that should seal it for long enough.

The problem is that the Centaur is a cryogenic upper stage that uses LOX and LH2 that needs to be safely vented overboard(think shuttle loaded on the pad on launch day). And the CISS provides these services to safely vent/condition the propellants prior to deployment. So disconnecting the GH2/GOX CISS/Centaur vent lines is not a good idea while still in the payload bay.

 

[DaveS]

I've done some further photographic analysis and have come to the most likely conclusion that the pipes coming off the Deployment Adapter is actually telescoping in the way you suggested Urwumpe.

If you look closely on the Centaur in the SSPF photo, you can see the disconnect rings, between the CISS structure and the engine support stand struts.

I'm going to model this and see if things line properly (I have a pretty good feeling that they will).

---------- Post added 02-26-11 at 09:46 AM ---------- Previous post was 02-25-11 at 09:59 AM ----------

Just checking here, who's up to coding this beast? Obviously we're going to need some mission file additions that removes the payload bay umbilical panel flight doors from the orbiter so that the umbilicals are exposed.

The control panel could be a modified IUS Standard Switch Panel.

---------- Post added at 04:57 PM ---------- Previous post was at 09:46 AM ----------

Just completed modeling to point complete enough that would allow me to test the telescoping pipe idea and it works. We're going to need a scaling animation along with the main Deployment Adapter rotation animation though for the telescoping part.