Boldly Going: A History of an American Space Station

[e of pi]

The complexity of the changes that would be made to OV-101 Enterprise as she would be converted from shuttle to station are best seen with this collection of images taken of the historic orbiters as they were being built, and under maintenance over their lives. You can see how the primary structure is designed, and how the crew module fits into this as a single unit. How much of this would have to be revealed again in the process of tearing Enterprise apart for conversion is left to the imagination of the readers and the nightmares of the Space Station Enterprise Program Office planners ITTL.















When the crew module is inserted, the station Xo=576 bulkhead of the crew module rests against the Xo=582 ring bulkhead, which is part of the primary structure of the orbiter. There’s a removable hatch in the Xo=576 bulkhead which you’ll notice, which is used to gain access to the internal airlock on those orbiters which had them. It was a tight squeeze, but it allowed installing or removing the bulky airlock. It’s a pretty unique view, and though Enterprise never had an airlock here OTL and thus never had to have it removed ITTL, this hatch is relevant for some modifications to eliminate the need for a “bent” passage to the Spacelab module.






The assembly process and some of the scale of the External Tank can be grasped in some of these images of the assembly process, including some unique shots of the tanks before spray-foam application.

 

[Luath]

Montgomery Scott: Ah ma puir bairn!!

 

[groundhogday666]

Impressive pictures ! Never saw them before. can't help asking - where did you found that ?

 

[Polish Eagle]

Well, at least perhaps OV-101's wings will fly to orbit and back, incorporated into *Endeavour. I wonder if maybe the SSMEs can also be snipped out and recovered by a later Orbiter.

The planned 1987 launch date implies that Station Enterprise will have its launch delayed by a disaster in 1986, so it looks like a 1989 launch is more likely.

I wonder, given the extent of the modifications, whether using OV-101 like this is actually ending up a net savings over a new-build Shuttle-C-type space station core.

 

[Athelstane]

Will Enterprise be getting a remote manipulator arm at any point?

 

[UrbanNight]

Will Enterprise be getting a remote manipulator arm at any point?

I think the Canadarm had been already installed on Enterprise as a test and flown operationally with Columbia by this point, so maybe not.
As anytime a Space Shuttle goes up, it'll bring the Canadarm with it, unless they decide to permanently migrate it to Enterprise.

 

[KAL_9000]

I think the Canadarm had been already installed on Enterprise as a test and flown operationally with Columbia by this point, so maybe not.
As anytime a Space Shuttle goes up, it'll bring the Canadarm with it, unless they decide to permanently migrate it to Enterprise.

Five Canadarms were built in total. Assuming one is lost on the Discovery Disaster, that leaves three left for the remaining Shuttles if one is moved to Enterprise.

 

[Athelstane]

You could have one hell of a zero-g soccer game in that tank, if nothing else.

 

[JamesHunter]

Well, at least perhaps OV-101's wings will fly to orbit and back, incorporated into *Endeavour. I wonder if maybe the SSMEs can also be snipped out and recovered by a later Orbiter.

The planned 1987 launch date implies that Station Enterprise will have its launch delayed by a disaster in 1986, so it looks like a 1989 launch is more likely.

I wonder, given the extent of the modifications, whether using OV-101 like this is actually ending up a net savings over a new-build Shuttle-C-type space station core.

SSME's are very heavy and notoriously labour intensive (the Shuttle had to literally be dismantled and rebuilt each time it flew after all) with a limited reuse capacity. As the Enterprise is unlikely to launch using a new set (due to cost and the effort to get them home) they will probably be considered disposable and left in place.

Also as mentioned there is no certainty Discovery was lost in 1986 (although I accept that's up to the authors). While an accident waiting to happen the proximate cause of Challenger was unusually low temperatures even for a a Florida winter. As such the odds of it blowing up on any other day are fairly low and its vaguely possible the issue gets fixed before fate catches up (this is the pre 2003 NASA and safety though). Columbia in contrast was inevitable as the foam was Russian roulette just with 107 barrels instead of six. Going back to STS-1 the death shot could have come at any time.

Obviously as OTL OV-05 will be built of spare parts so the wings are probably inevitable. Although as with Columbia and (to a lesser extent) Challenger, Enterprise is a bit heavier than the later Birds so its wings might not be much use building a more advanced orbiter design.

 

[e of pi]

SSME's are very heavy and notoriously labour intensive (the Shuttle had to literally be dismantled and rebuilt each time it flew after all) with a limited reuse capacity. As the Enterprise is unlikely to launch using a new set (due to cost and the effort to get them home) they will probably be considered disposable and left in place.

While I'll leave the rest of the speculation for now,(though we will be covering it later), it's worth noting overhaul requirements changed a lot over the program life., dropping dramatically in overhaul frequency and labor time required. After the end of the program, the AR-22, essentially an SSME derivative, completed a test series in 2018 where they did 10 flight-duration firings in 10 days with no maintenance,. That rate was limited mostly by the ability to dry the engine between flights.

DARPA, companies declare success in AR-22 engine test series

A government-industry team announced July 10 they successfully completed a series of 10 test firings over 10 days of a shuttle-era engine.

spacenews.com

Heavy and hard to remove in-flight on EVA are definitely true.

 

[JamesHunter]

While I'll leave the rest of the speculation for now,(though we will be covering it later), it's worth noting overhaul requirements changed a lot over the program life., dropping dramatically in overhaul frequency and labor time required. After the end of the program, the AR-22, essentially an SSME derivative, completed a test series in 2018 where they did 10 flight-duration firings in 10 days with no maintenance,. That rate was limited mostly by the ability to dry the engine between flights.

DARPA, companies declare success in AR-22 engine test series

A government-industry team announced July 10 they successfully completed a series of 10 test firings over 10 days of a shuttle-era engine.

spacenews.com

Heavy and hard to remove in-flight on EVA are definitely true.

Ah I see. But it was a common criticism during the program and this is early days. It also doesn't help zero thought was ever given to on orbit engine maintenance (they can't be restarted anyway) so just designing a procedure for that EVA would be a nightmare. Also I guess removing them might cause centre of gravity issues?

 

[TimothyC]

Impressive pictures ! Never saw them before. can't help asking - where did you found that ?

The first several images are NASA sourced, but I've had them for so long that I don't remember where I got them from. I know that several of them are from Atlantis construction (that is the Atlantis crew compartment being moved via tractor). The colored diagram is, if my memory serves, from one of the reports relating to the Columbia Accident. The last two photos are from NASA, and we're actually just using the NASA server to host them, rather than rehosting them ourselves

 

[NHBL]

This is utterly amazing! I'm just starting to learn about some of the nuts and bolts of rocketry for my own timeline.
Next time I visit Kennedy Space Center, I'll be imagining Atlantis in this configuration.
FOLLOWING!

 

[JEF_300]

Another great update, but now I've got a whole bunch of OMS questions.
Is an OMS-1 burn required to put Enterprise in orbit?
Are the OMS engines going to be included at all?
If they are, will they be the primary method of station keeping?
I guess we'll end up seeing on orbit hypergol transfers earlier than OTL to keep the tanks full?
Have they adjusted the angle of the OMS engines to account for the fact that the ET is always going to be there? In OTL they never used the OMS while the ET was still attached (to my knowledge), and while all the studies do seem to indicate that it wouldn't have been a problem, it seems like something you would account for on the ground if you could.

 

[JamesHunter]

Another great update, but now I've got a whole bunch of OMS questions.
Is an OMS-1 burn required to put Enterprise in orbit?
Are the OMS engines going to be included at all?
If they are, will they be the primary method of station keeping?
I guess we'll end up seeing on orbit hypergol transfers earlier than OTL to keep the tanks full?
Have they adjusted the angle of the OMS engines to account for the fact that the ET is always going to be there? In OTL they never used the OMS while the ET was still attached (to my knowledge), and while all the studies do seem to indicate that it wouldn't have been a problem, it seems like something you would account for on the ground if you could.

Can't answer the rest but as the SSME can't be restarted on orbit they'll pretty much have to use the OMS for that job. Or build a new system that rather defeats the purpose of using a Shuttle in the first place...

 

[JEF_300]

Can't answer the rest but as the SSME can't be restarted on orbit they'll pretty much have to use the OMS for that job. Or build a new system that rather defeats the purpose of using a Shuttle in the first place...

The only reason I ask is because the OMS engines are a lot more than is needed for station keeping. A smaller more efficient custom system would seem reasonable if practical.

Which then ties into the other questions. If you don't need and OMS-1 burn, then maybe leaving the OMS engines off altogether and using a smaller system is a good idea. If you do need an OMS-1, then why add another engine when the OMS will do the job.

 

[ChairAgainstWall]

E of pi and the gang build another early space station. SHUT UP AND TAKE MY MONEY!

 

[JamesHunter]

The only reason I ask is because the OMS engines are a lot more than is needed for station keeping. A smaller more efficient custom system would seem reasonable if practical.

Which then ties into the other questions. If you don't need and OMS-1 burn, then maybe leaving the OMS engines off altogether and using a smaller system is a good idea. If you do need an OMS-1, then why add another engine when the OMS will do the job.

It can probably be used for orbital reboost though and as established tech may still keep costs down.

 

[Bureaucromancer]

I'll put this out there re the SSMEs: given the nature of the wetlab component here, I have to imagine that at some stage there will be an experimental attempt to remove at least one engine in a "can we do this" experimental mode.

My own big question at this point though is what of a lifeboat? Might we see CSM-119 (or at least the CM with a solid retro pack) going up on a shuttle?

 

[Athelstane]

My own big question at this point though is what of a lifeboat?

This will become an urgent question when the time comes to consider any permanent crewing of the station. But I'm sure our authors have given this serious thought.