Centaur G/G Prime High Energy Upper Stage

[GLS]

This is what I know:

Discovery benefited from lessons learned in the construction and testing of Enterprise, Columbia and Challenger. At rollout, its weight was some 6,870 pounds less than Columbia. Two orbiters, Challenger and Discovery, were modified at KSC to enable them to carry the Centaur upper stage in the payload bay. These modifications included extra plumbing to load and vent Centaur's cryogenic (L02/LH2) propellants (other IUS/PAM upper stages use solid propellants), and controls on the aft flight deck for loading and monitoring the Centaur stage. No Centaur flight was ever flown and after the loss of Challenger it was decided that the risk was too great to launch a shuttle with a fueled Centaur upper stage in the payload bay.

source: http://science.ksc.nasa.gov/shuttle/resources/orbiters/discovery.html

And there's a very similar text somewhere in Jenkins book.

 

[DaveS]

Well, that's incorrect. Atlantis and Challenger were the only Centaur capable orbiters in the fleet. I think Jenkins' mistook the partial Mod Kit installation on Atlantis to mean that she had the full Mod Kit. He also states that the LO2 for Centaur would been tapped from MPS plumbing in the aft. This is incorrect. The Centaur cryo plumbing was independent from the orbiter MPS plumbing.

 

[DaveS]

Another nice upload by the San Diego Air and Space Museum:

 

[DaveS]

Q for GLS on MECO targets for the STS-61F/G: I see that they have been changed to a 180 km MECO apogee. What is the source for this? All my sources agree on 240 km MECO apogee for both missions.

Total loaded mass for STS-61G was to be 29 250 kg which included a 955.8 kg propellant offload for the Centaur. The total loaded mass for STS-61F was to be 28 102 kg with not propellant offloading.

 

[barrygolden]

Great work David S. you really did a lot of research on this project. Centaur G/ G prime would have been a beast. What would the smaller Centaur been used for? Do you have both versions in the SSU stuff ?

 

[DaveS]

Great work David S. you really did a lot of research on this project. Centaur G/ G prime would have been a beast. What would the smaller Centaur been used for? Do you have both versions in the SSU stuff ?

The smaller version was the Centaur G and was intended for GEO-bound spacecrafts. The the larger G Prime was really only for the NASA interplanetary spacecrafts in work at the time (Galileo and Ulysses, formerly known as the International Solar Polar Mission or ISPM).

 

[GLS]

Q for GLS on MECO targets for the STS-61F/G: I see that they have been changed to a 180 km MECO apogee. What is the source for this? All my sources agree on 240 km MECO apogee for both missions.

Total loaded mass for STS-61G was to be 29 250 kg which included a 955.8 kg propellant offload for the Centaur. The total loaded mass for STS-61F was to be 28 102 kg with not propellant offloading.

Well, it was supposed to be 194.46Km (or 105nm), which was the lowest orbit the shuttle could do, and that's what I've read all along. But clearly there's something wrong because it only gets to 180Km... just played a bit with the SSME tailoff dV, and even overspeeding by 5 or 10fps at MECO the apogee doesn't even get into the 190s.
After checking of the code, the Earth radius value might not be helping things: in the MECOTool the value used is 6378Km, but in AscentGuidance that value comes from "EarthRadius = oapiGetSize(hEarth);", which checking orbiter's documentation would give 6371Km, so there's 7Km gone. But then the perigee used in the MECOTool is 55Km and I'm getting 60Km so the radius is not the only source of problems.

About the masses, I don't have info except there was a Centaur propellant offload for the Galileo mission as everything was getting heavier and heavier.

 

[DaveS]

Well, it was supposed to be 194.46Km (or 105nm), which was the lowest orbit the shuttle could do, and that's what I've read all along. But clearly there's something wrong because it only gets to 180Km... just played a bit with the SSME tailoff dV, and even overspeeding by 5 or 10fps at MECO the apogee doesn't even get into the 190s.
After checking of the code, the Earth radius value might not be helping things: in the MECOTool the value used is 6378Km, but in AscentGuidance that value comes from "EarthRadius = oapiGetSize(hEarth);", which checking orbiter's documentation would give 6371Km, so there's 7Km gone. But then the perigee used in the MECOTool is 55Km and I'm getting 60Km so the radius is not the only source of problems.

About the masses, I don't have info except there was a Centaur propellant offload for the Galileo mission as everything was getting heavier and heavier.

Yes, the MECOTool problem has been discussed extensively earlier but not yielded anything so far on a fix. For some reason it has always been pushed away with some explanation.

The masses I used came from two principal documents, Centaur G Technical Description (GDC January 23 1984) and A high energy stage for the National Space Transporation System

 

[Donamy]

How is the control panel coming ?

 

[GLS]

The math seems correct, the only thing that wrong I can see is the radius (maybe that's the only problem). I could correct it, but the MECOTool project is from VS2008, and I would have to convert it... and usually it's a mess... so if anyone has VS2008, it's just changing a number and compile.

 

[DaveS]

How is the control panel coming ?

You mean the one you made? That was the for the IUS. Despite my extensive searches, I have come up with absolutely nothing whatsoever on the panel(s) for the Centaur. So we might have to come up with a design of our own based on what we do know. Same goes for the DPS displays.

 

[GLS]

to keep the threads "clean" I'm moving the MECOTool discussion to http://www.orbiter-forum.com/showthread.php?p=484410&postcount=508

 

[DaveS]

I have recently gotten in touch with a really good source with access to alot of good information on the whole Shuttle-Centaur program. This information is not digitized so in order to cut down on the amount to be scanned, an idea of what is most urgent is required.

So it would be great if you could post what is required in terms of documentation to get a first version up and running.

 

[Urwumpe]

I have recently gotten in touch with a really good source with access to alot of good information on the whole Shuttle-Centaur program. This information is not digitized so in order to cut down on the amount to be scanned, an idea of what is most urgent is required.

So it would be great if you could post what is required in terms of documentation to get a first version up and running.

Well... can you get a TOC for us first? Would make it easier to decide what can be found.

From my POV, information about flight planning and the panels in the flight deck (And of course the CRT SPECs for it) would be interesting.

Pre-launch processing would be interesting sometime later, if the source is only temporarily available, we should grab such information as well.

 

[DaveS]

Well... can you get a TOC for us first? Would make it easier to decide what can be found.

From my POV, information about flight planning and the panels in the flight deck (And of course the CRT SPECs for it) would be interesting.

Pre-launch processing would be interesting sometime later, if the source is only temporarily available, we should grab such information as well.

I'll ask when he gets back to me. I have already asked about procedures and Standard Switch Panel (SSP) graphics.

 

[GLS]

Yeah, a TOC would be nice. But in any case CRT displays, redlines, timelines, LCCs (if any), panel diagram and numbers (masses, pressures, etc.) would be appreciated.

 

[DaveS]

Quote from SSU Development Thread (2.0 to 3.0):

But we're still going to have at least 1 texture for OV-099 and OV-102 in a release, right?

Currently we don't have any real missions for them. The CCE (Centaur Cargo Element) for STS-61F/G is just really a dummy for now. Even the default Carina satellite is more functional and it is just a cfg.

You could get started on the CCE as everything required is there. The only thing really missing is the twin-RL10's on the Centaur.

 

[GLS]

Can we hack a spacecraft file vessel for this release only? If we want to release in the short term, there's no way we're going to be able to do the Centaur with all its bells and whistles...

 

[DaveS]

Can we hack a spacecraft file vessel for this release only? If we want to release in the short term, there's no way we're going to be able to do the Centaur with all its bells and whistles...

That's how things are setup currently. No way to control things remotely. We could create a separate branch to get Centaur dev started without holding up the trunk for release.

 

[GLS]

That's how things are setup currently. No way to control things remotely. We could create a separate branch to get Centaur dev started without holding up the trunk for release.

I don't think it's a major problem having to change vessels (we have bigger "holes" in SSU at the moment). The lack of dump capability is not really a problem as we still don't have aborts.
Although I really want to have the Centaur working, it has to wait until after the configuration program/editor/whatever is done. Once we have that square away, I'm planning on creating a branch for centaur (and another for OMS/RCS), and get that train moving.