Before we dive right in let’s make sure we’re all on the same page as to the primary reason the Shuttle was designed the way it was. NASA’s primary goal since the very beginning of the Shuttle concept was that a crew would be required for every flight to ensure that the Manned Spaceflight program would remain the main focus of NASA. Really no more and no less than that as can be shown by the fact the Orbiter was built and wired to be flown remotely from the beginning, (should something happen to the crew) but the only way that could be done was by hand connecting a special wiring harness between the flight computers and the control computers. While installed for the first two flights it was never carried on-board again during a flight. Combined with an operational plan that called for the Shuttle to be the ONLY US launch system by the year 2000, (originally 1990 but the schedule slipped due to the operational date of the Shuttle being pushed back) this was guaranteed to ensure NASA Manned Spaceflight would remain the supreme purpose of NASA. Cynical of course but there it is.
From this reasoning then it can be clearly seen that any concept or utilization of the STS components that did NOT require a crew on every flight were dismissed out of hand due to violating that prime reasoning. Hence even though Rockwell itself had studied and forwarded such concepts to NASA they were trashed upon receipt or filed away somewhere ‘safe’. (Like in a storeroom behind the Men’s lavatory with a prominent sign saying “Beware the Leper!” for example)
A secondary reasoning was the need to recover the “upper” stage engines which was found to be problematical in general. But oddly enough coupled with the primary reason led to the idea that they (crew and engines) should be connected together in some manner which also led to the idea of installing a place for carrying cargo between the two. So no matter how much other things had to be compromised or rearranged in the end the trinity of crew, cargo-bay and engines remained intact.
Until a very cold morning in 1986 and the launch and subsequent destruction of the Space Shuttle Challenger. At this point someone finally admits the Emperor has no clothes but OTL the reaction from NASA is to continue to insist that the primary purpose of the Shuttle is to fly a crew on every flight while the official report to both NASA and Congress, (and the public) clearly states, well first of all “Don’t fly when it’s cold” but also points out there is no real reason to fly both cargo and crew as most flights do not in fact really NEED the crew once you ‘fix’ that whole remote flight system which of course NASA ‘declined’ (prime directive and all that) but considered for the ‘next’ crew vehicle. In general this gave NASA an excuse to drop “commercial” payload support which was one of their main justifications for having the Shuttle declared the primary US launch vehicle but for which they didn’t have the capacity to support. (In fact this is the point also where the Air Force does another about-face from full support of the Shuttle to looking for alternatives which will eventually push to the EELV program beginning in 1994) This causes the satellite industry to go looking for alternatives as most US launch providers had already begun to ramp down production to cede it to the Shuttle. (China, Russia and France all were very appreciative of the whole deal)
And then NASA “fixed” the Shuttle by adding an escape system, (the fire pole) while designing into the next vehicle they wanted (Shuttle II) an actual escape capsule. (Nice idea but given how complex that sucker got to avoid using SRBs along with the mass of that escape capsule you can see why it never got anywhere)
The mantra of don’t-fly-cargo-and-crew on the same flight, (one could argue the REAL “lesson-learned” was better expressed as “have a crew escape system” but…) brought up again those previously rejected concepts into the light of day. Enter Shuttle-C, Z, etc. Still at this point the ISS is being built and launches scheduled so the actual ‘need’ for an unmanned shuttle seems to be less and if we’re being totally honest there is no real incentive either politically or in NASA to make any radical changes because NASA is finally getting its post-Apollo dream: A space station serviced by a reusable space shuttle. Full stop.
Literally that’s IT for NASA’s foreseeable future. And why not since NASA is going on and on about the ISS being the “first” step in a return to the Moon and Mars and now G. W. Bush is proposing the whole VSE thing and encouraging NASA to “dream big” not that they need the help…
But let’s back up to 1986 again and suggest that this was a perfect opportunity for NASA to come clean about the Shuttle’s shortcomings as both official and unofficial investigation was pointing out that Congressional hands were almost as ‘dirty’ as the officially blamed “NASA culture” for those shortcomings. NASA’s budget was getting a temporary boost to ‘fix’ the main issues with the Shuttle but was instead spent on ‘band aids’ (fire pole) and accelerating already in work fixes, (SRB joints) so that the Shuttle could officially return to flight in order to work on the ISS. And I’d like to think that handled with vigor and aplomb, (ie: blackmail if needs be) a compromise could be worked out where NASA is assured that as long as it really works out the Shuttle issues and allows enough expanded option to cover its original commitments that Congress will allow an adequate budget and support for building up a Cis-Lunar infrastructure capable of eventually going beyond LEO. BUT! NASA has to submit and stick to a comprehensive NEAR-TERM (no Mars but maybe LATER the Moon, you’ve been warned) sustainable and affordable plan that they and Congress can agree on.
Nearly ASB or course if for no other reason that Congress has no need or really basis to actually trust NASA to stick to any bargain they make since they have not done so at any point in their history if they thought they could get away with it. Armored by the assurance in their own minds that as had happened in 1979, (see:https://arstechnica.com/science/201...-why-did-jimmy-carter-save-the-space-shuttle/, and https://www.alternatehistory.com/forum/threads/wi-carter-lets-the-space-shuttle-die.396883/) “a miracle” would occur since no one would DREAM of shutting down American space flight and closing NASA! Hyperbole? Oh heck yes as it was only in the minds of some of the same people who never accepted cuts in the Apollo budget that demanding NASA do what it actually said it was doing was a possible outcome. Or that there was more to “US space flight” than manned flights. That Congress looked to be doing exactly that was no help whatsoever of course. But…
Here NASA has two incentives, one long term and one near term; First they get enough to actually ‘fix’ most of the real Shuttle issues though to be honest ‘crew-escape’ is likely not one of them beyond the fire-pole. Beyond this in the near term they are going to ‘lose’ some manned flights but as per OTL they can managed to keep the majority by being more careful and reducing the flight pace. They are going to ‘lose’ the manned portion of some but played right it will allow them to turn the aptly named “Space Transportation SYSTEM” into an actual system and increase their general flight schedule. Which in the long run means MORE not less manned flights after all.
See while they no longer can insist that every flight be manned at the same time developing an unmanned, possibly recoverable version of the STS is quite possible AND it cuts the Air Force running to build/buy another launch system off at the knees. (OTL till the EELV came online Congress allowed the Air Force an additional budget to purchase Titan-IV’s which the Air Force lied about being ‘cost-effective’ because it played on the Titan ICBM legacy. In reality about the only thing they had in common was the name and propellants because the Titan-IV cores were all new and specially built which drove up the cost greatly) And since an STS based LV could dispense with the ‘standard’ Shuttle payload interfaces and replace them with say, Titan based ones the fact that the Air Force canceled and re-ordered all its post-Challenger satellites with Titan rather than Shuttle interfaces means we’re SAVING the Air Force money!
Don’t laugh manically at the Air Force there NASA its rude. Seriously, its unbecoming and frankly beginning to get a little, ok a LOT creepy. I’m serious stop it right now or go to your room… I can still hear you!
Uhm, where was I? Oh yes…
Now while the “Sidemount” configuration has issues, (see previous posts) a very important point is that by making small and incremental changes, (afore mentioned SSI External Tank modifications study) such as needed to utilize both or either Aft Cargo Carrier (ACC) and/or Forward Cargo Carrier (FCC)) and other modifications. Along the way it might be more clear that the idea of incorporating the required structural elements also allows in essence ends up with an ET fully capable of being used as an ‘in-line’ heavy launch vehicle pretty easily. (Note the studies on the ACC showed it was pretty straight forward to turning it into an engine-thrust structure which the Air Force confirmed with their Titan based booster module studies)
Which in and of itself is a huge step forward for the whole ‘system’ since once the ORBITERS are retired NASA and the US will continue to have a basic man rated launch vehicle for any follow on crew vehicle designed to utilize the same system.
What’s that? A capsule? Quaint of course, and as we’ll find out OTL during the OSP program actually what NASA requirements are more suited to, but in fact we could just as well develop a smaller manned winged or lifting body, (even one developed from the original Orbiter as per: https://www.aiaa.org/uploadedfiles/...uttle_launches/shuttlevariationsfinalaiaa.pdf) that is lofted by SRBs and engines mounted on the ET. Sounds like Energia you say? Well WE say the Russians copied us so there…
More seriously in this type of arrangement, especially once you understand the STS is in fact a ‘system’ and treat it as such then replacing the current “orbiter” with a more advanced version while retaining the general configuration actually is pretty straight forward.
What, you say that doesn’t solve the crew escape situation? Keep in mind that neither the SRB nor the ET rupture directly killed Challenger. What did her in was once she lost thrust she had no control over her attitude since she was going too fast for effective aerodynamic control AND still attached to the SRBs and what was left of the ET. Had she been able to jettison those items she had a fighting chance to wrestle herself into a glide back to the runway. AS the whole design was based on any emergency NOT happening when the SRBs were running that wasn’t possible. But give her onboard propellant and propulsion (page 3 figure 5 above) and she can not only separate but if she has to remain to SRB burnout there’s a fighting chance she can power her way into keeping the nose forward till that point. Further by developing and deploying either of the recoverable engine pod concepts, (page 2 figures 1 to 4) we can get back into at least long distance of the initial cost reduction goals. (Higher flight rate helps, recovery distance hurts so it’s may be a wash but it trying at least)
Annoyingly the SSME’s themselves on the Orbiter greatly hindered its flight characteristics. Moving them to a pod under the ET frees up mass on the Orbiter and once it is re-balanced it will have lighter less stressful entry and landings which is always a good thing. Boeing also chimed in with some ‘minimum’ (page 10 figure 22) but very promising ‘straight-forward’ modification to enhance the STS.
And while we’re at it we might as well acknowledge that by 1986 there was an interest in the utilization of the external tanks on-orbit to the point that despite what happened post-Challenger OTL both Congress and President Reagan directed NASA to make external tanks “available” to entrepreneurs and interested parties. (See:https://spacefrontier.org/external-tanks/ Good links to ET technical papers and concept here too. The ‘catch’ was and the out used by NASA was those parties had first prove and provide functions ON-ORBIT before NASA would plan a delivery. Arguably this is a good call since it was known that if the tanks wasn’t stabilized and drained within a few hours of reaching orbit it would explode due to internal pressure build up)
A positive incentive TTL versus OTL is that with an expanded mandate (and the support to maintain a higher flight rate) NASA has a bit more incentive to reach out to commercial interests that could help get these concepts off the ground. (Pun intended) The downside as mentioned previously is companies like Boeing and LM are going to either jump into opening services for these outposts or lobby to have them denied to protect their own share of building orbital modules. But it is hard to understate how different both operational and future planning would be given any possible on-orbit use of the available volumes involved. (The ET LH2 tanks is over 53,000 cubic-ft while the LOX tank is another 19,000 cubic-feet and neither includes the inter-stage volume)
The most prominent downside is most of the more expansive concepts take some serious EVA work to accomplish. A LOT of serious EVA work to be upfront and the issue is no Space Suit is really designed to be capable of that kind of work because no one requires them to. It’s a very fair point when it comes to ‘wet’ module design but the main counter is that WVB along with several other engineers from his design team, (aka a bunch of engineers in their mid-to-late 50s at the time) stuffed themselves into space suits and dove into the neutral buoyancy simulator at Marshall and actually put their ideas on building a wet lab to the test. (And from a maintenance man’s perspective my hard hat is off to them for putting their ideas to the test instead of leaving for someone else to try) The final report was that it was quite doable, (but keep in mind they were using modified Gemini suits which in fact were horrible for EVA use) and that extra hand holds and fittings would be helpful. Now take into account that unlike the S-IVB stage used previously the ET had significant pre-installed openings that were only sealed by a bolt-on door and which was remarkably easy to expand to a size allowing a fully suited astronaut to enter and exit and OTHER than the space-suit issue the utility of the ET is obvious.
Again the main issue is there are/were no space suits designed for extensive manual on-orbit work.
But as a very “plus” column outcome the requirements for possible commercial use, (which OTL NASA fought tooth-and-nail) would have required a ‘fix’ for the loose insulation as well as some beefing-up of the ET general structure. But in the common “Chicken/Egg” issue delivery of an ET to orbit requires some sort of on-orbit presence by someone who would utilized the tank before such a tank could be delivered. (The often mentioned idea of ‘storing’ ET’s on-orbit neglects the very real and prolonged danger this represents as well as the number of international agreements it violates. Hence the need for an ‘on-orbit’ presence to USE the tanks before they can be delivered catch-all) Still an extended mandate and more direct support FROM commercial interests is likely to engender similar reciprocation from NASA in the form of less hostility towards those same commercial interests.
So as per the illustration in the SSI document on page 37 (page 51-53 shows a much more complex but capable ACC Service Module Station Core) showing an ACC fitted out with a Spacelab module and a Shuttle mission that carries the crew to orbit along with a cargo bay carried ‘emergency’ return vehicle “getting” that capability may be pretty straight forward. And if that is too much work the possibility of a ‘dry’ module launched on a sidemount, or inline SDV is always there.
What is around to prevent this is simply that in capability and possibility utilizing the STS and External Tank to their logical conclusion presents quite possibly far too MUCH to both NASA and others. Even if we assume no more than the budget given to construct the ISS OTL it becomes clear that the amount of pressurized space available is far too vast for that budget to outfit. Worse the required on-orbit operations will require a drastic and extensive re-working of space suits into models capable of being used efficiently and effectively for long hours in addition to a paradigm shift in the planning and execution of EVA activities. Even if we only assume that half (4 of 8) a “good” year’s flights deliver an ET to a usable orbit and make it available it would rapidly outstrip both the available budget and capability available to NASA or anyone else to utilize. While it won’t necessarily stay that way the situation will not change rapidly and as noted above it cuts out a majority of large aerospace companies who are not directly tied to ACC or other modular construction contracts. (A disincentive both for NASA and Congress)
And trust me when I say this hurts to admit for there was a time, not very long ago when the idea of calling a 300 foot diameter, (eight LH2 tanks connected by eight ‘angle’ segments carried up as ACC cargo) AG station capable of handling over 200 people in comfort “too much” would be unthinkable but in truth it is very much so given the capability available to utilize it let alone build it. Keep very much in mind that most industrial research benefits more from a smaller scale experimental system and specifically requires micro-gravity to function. One could argue that ANY AG station is only useful for curiosity sake since any BLEO operations are likely not going to include AG.
There is also the consideration of how this effects general commercial operations which will change significantly as well. Once you have an on-orbit presence the temptation to utilized it to expand and service commercial operations means that many initial and advanced concepts that dealt with everything from LEO-cluster arrays, (a non-starter when you have a lot of infrastructure and operations in LEO already) to cheaper access, (SpaceX and BO for example are very unlikely to be founded) get pushed aside. On the other hand you have MEO and GEO satellites that are now designed to take advantage of what on-orbit services are offered. Designed to be serviced and repaired and there is incentive to make them even bigger, more robust satellites with more of a ‘plug-and-play’ architecture to facilitate such activities and upgrades. Which further reduces the need for general space launch rather than enhances it. So we can try and assume factors like Space Tourism or industry but really there were somewhat sound reasons NASA and most official space agencies opposed the concepts. (In the industrial case the rationalizations are marginal at best anyway but this way there are at least more opportunities to experiment and possibly find viable business models)
It's arguably a "win" but the question of how much "better" it would be if probably very subjective
Randy
From this reasoning then it can be clearly seen that any concept or utilization of the STS components that did NOT require a crew on every flight were dismissed out of hand due to violating that prime reasoning. Hence even though Rockwell itself had studied and forwarded such concepts to NASA they were trashed upon receipt or filed away somewhere ‘safe’. (Like in a storeroom behind the Men’s lavatory with a prominent sign saying “Beware the Leper!” for example)
A secondary reasoning was the need to recover the “upper” stage engines which was found to be problematical in general. But oddly enough coupled with the primary reason led to the idea that they (crew and engines) should be connected together in some manner which also led to the idea of installing a place for carrying cargo between the two. So no matter how much other things had to be compromised or rearranged in the end the trinity of crew, cargo-bay and engines remained intact.
Until a very cold morning in 1986 and the launch and subsequent destruction of the Space Shuttle Challenger. At this point someone finally admits the Emperor has no clothes but OTL the reaction from NASA is to continue to insist that the primary purpose of the Shuttle is to fly a crew on every flight while the official report to both NASA and Congress, (and the public) clearly states, well first of all “Don’t fly when it’s cold” but also points out there is no real reason to fly both cargo and crew as most flights do not in fact really NEED the crew once you ‘fix’ that whole remote flight system which of course NASA ‘declined’ (prime directive and all that) but considered for the ‘next’ crew vehicle. In general this gave NASA an excuse to drop “commercial” payload support which was one of their main justifications for having the Shuttle declared the primary US launch vehicle but for which they didn’t have the capacity to support. (In fact this is the point also where the Air Force does another about-face from full support of the Shuttle to looking for alternatives which will eventually push to the EELV program beginning in 1994) This causes the satellite industry to go looking for alternatives as most US launch providers had already begun to ramp down production to cede it to the Shuttle. (China, Russia and France all were very appreciative of the whole deal)
And then NASA “fixed” the Shuttle by adding an escape system, (the fire pole) while designing into the next vehicle they wanted (Shuttle II) an actual escape capsule. (Nice idea but given how complex that sucker got to avoid using SRBs along with the mass of that escape capsule you can see why it never got anywhere)
The mantra of don’t-fly-cargo-and-crew on the same flight, (one could argue the REAL “lesson-learned” was better expressed as “have a crew escape system” but…) brought up again those previously rejected concepts into the light of day. Enter Shuttle-C, Z, etc. Still at this point the ISS is being built and launches scheduled so the actual ‘need’ for an unmanned shuttle seems to be less and if we’re being totally honest there is no real incentive either politically or in NASA to make any radical changes because NASA is finally getting its post-Apollo dream: A space station serviced by a reusable space shuttle. Full stop.
Literally that’s IT for NASA’s foreseeable future. And why not since NASA is going on and on about the ISS being the “first” step in a return to the Moon and Mars and now G. W. Bush is proposing the whole VSE thing and encouraging NASA to “dream big” not that they need the help…
But let’s back up to 1986 again and suggest that this was a perfect opportunity for NASA to come clean about the Shuttle’s shortcomings as both official and unofficial investigation was pointing out that Congressional hands were almost as ‘dirty’ as the officially blamed “NASA culture” for those shortcomings. NASA’s budget was getting a temporary boost to ‘fix’ the main issues with the Shuttle but was instead spent on ‘band aids’ (fire pole) and accelerating already in work fixes, (SRB joints) so that the Shuttle could officially return to flight in order to work on the ISS. And I’d like to think that handled with vigor and aplomb, (ie: blackmail if needs be) a compromise could be worked out where NASA is assured that as long as it really works out the Shuttle issues and allows enough expanded option to cover its original commitments that Congress will allow an adequate budget and support for building up a Cis-Lunar infrastructure capable of eventually going beyond LEO. BUT! NASA has to submit and stick to a comprehensive NEAR-TERM (no Mars but maybe LATER the Moon, you’ve been warned) sustainable and affordable plan that they and Congress can agree on.
Nearly ASB or course if for no other reason that Congress has no need or really basis to actually trust NASA to stick to any bargain they make since they have not done so at any point in their history if they thought they could get away with it. Armored by the assurance in their own minds that as had happened in 1979, (see:https://arstechnica.com/science/201...-why-did-jimmy-carter-save-the-space-shuttle/, and https://www.alternatehistory.com/forum/threads/wi-carter-lets-the-space-shuttle-die.396883/) “a miracle” would occur since no one would DREAM of shutting down American space flight and closing NASA! Hyperbole? Oh heck yes as it was only in the minds of some of the same people who never accepted cuts in the Apollo budget that demanding NASA do what it actually said it was doing was a possible outcome. Or that there was more to “US space flight” than manned flights. That Congress looked to be doing exactly that was no help whatsoever of course. But…
Here NASA has two incentives, one long term and one near term; First they get enough to actually ‘fix’ most of the real Shuttle issues though to be honest ‘crew-escape’ is likely not one of them beyond the fire-pole. Beyond this in the near term they are going to ‘lose’ some manned flights but as per OTL they can managed to keep the majority by being more careful and reducing the flight pace. They are going to ‘lose’ the manned portion of some but played right it will allow them to turn the aptly named “Space Transportation SYSTEM” into an actual system and increase their general flight schedule. Which in the long run means MORE not less manned flights after all.
See while they no longer can insist that every flight be manned at the same time developing an unmanned, possibly recoverable version of the STS is quite possible AND it cuts the Air Force running to build/buy another launch system off at the knees. (OTL till the EELV came online Congress allowed the Air Force an additional budget to purchase Titan-IV’s which the Air Force lied about being ‘cost-effective’ because it played on the Titan ICBM legacy. In reality about the only thing they had in common was the name and propellants because the Titan-IV cores were all new and specially built which drove up the cost greatly) And since an STS based LV could dispense with the ‘standard’ Shuttle payload interfaces and replace them with say, Titan based ones the fact that the Air Force canceled and re-ordered all its post-Challenger satellites with Titan rather than Shuttle interfaces means we’re SAVING the Air Force money!
Don’t laugh manically at the Air Force there NASA its rude. Seriously, its unbecoming and frankly beginning to get a little, ok a LOT creepy. I’m serious stop it right now or go to your room… I can still hear you!
Uhm, where was I? Oh yes…
Now while the “Sidemount” configuration has issues, (see previous posts) a very important point is that by making small and incremental changes, (afore mentioned SSI External Tank modifications study) such as needed to utilize both or either Aft Cargo Carrier (ACC) and/or Forward Cargo Carrier (FCC)) and other modifications. Along the way it might be more clear that the idea of incorporating the required structural elements also allows in essence ends up with an ET fully capable of being used as an ‘in-line’ heavy launch vehicle pretty easily. (Note the studies on the ACC showed it was pretty straight forward to turning it into an engine-thrust structure which the Air Force confirmed with their Titan based booster module studies)
Which in and of itself is a huge step forward for the whole ‘system’ since once the ORBITERS are retired NASA and the US will continue to have a basic man rated launch vehicle for any follow on crew vehicle designed to utilize the same system.
What’s that? A capsule? Quaint of course, and as we’ll find out OTL during the OSP program actually what NASA requirements are more suited to, but in fact we could just as well develop a smaller manned winged or lifting body, (even one developed from the original Orbiter as per: https://www.aiaa.org/uploadedfiles/...uttle_launches/shuttlevariationsfinalaiaa.pdf) that is lofted by SRBs and engines mounted on the ET. Sounds like Energia you say? Well WE say the Russians copied us so there…
More seriously in this type of arrangement, especially once you understand the STS is in fact a ‘system’ and treat it as such then replacing the current “orbiter” with a more advanced version while retaining the general configuration actually is pretty straight forward.
What, you say that doesn’t solve the crew escape situation? Keep in mind that neither the SRB nor the ET rupture directly killed Challenger. What did her in was once she lost thrust she had no control over her attitude since she was going too fast for effective aerodynamic control AND still attached to the SRBs and what was left of the ET. Had she been able to jettison those items she had a fighting chance to wrestle herself into a glide back to the runway. AS the whole design was based on any emergency NOT happening when the SRBs were running that wasn’t possible. But give her onboard propellant and propulsion (page 3 figure 5 above) and she can not only separate but if she has to remain to SRB burnout there’s a fighting chance she can power her way into keeping the nose forward till that point. Further by developing and deploying either of the recoverable engine pod concepts, (page 2 figures 1 to 4) we can get back into at least long distance of the initial cost reduction goals. (Higher flight rate helps, recovery distance hurts so it’s may be a wash but it trying at least)
Annoyingly the SSME’s themselves on the Orbiter greatly hindered its flight characteristics. Moving them to a pod under the ET frees up mass on the Orbiter and once it is re-balanced it will have lighter less stressful entry and landings which is always a good thing. Boeing also chimed in with some ‘minimum’ (page 10 figure 22) but very promising ‘straight-forward’ modification to enhance the STS.
And while we’re at it we might as well acknowledge that by 1986 there was an interest in the utilization of the external tanks on-orbit to the point that despite what happened post-Challenger OTL both Congress and President Reagan directed NASA to make external tanks “available” to entrepreneurs and interested parties. (See:https://spacefrontier.org/external-tanks/ Good links to ET technical papers and concept here too. The ‘catch’ was and the out used by NASA was those parties had first prove and provide functions ON-ORBIT before NASA would plan a delivery. Arguably this is a good call since it was known that if the tanks wasn’t stabilized and drained within a few hours of reaching orbit it would explode due to internal pressure build up)
A positive incentive TTL versus OTL is that with an expanded mandate (and the support to maintain a higher flight rate) NASA has a bit more incentive to reach out to commercial interests that could help get these concepts off the ground. (Pun intended) The downside as mentioned previously is companies like Boeing and LM are going to either jump into opening services for these outposts or lobby to have them denied to protect their own share of building orbital modules. But it is hard to understate how different both operational and future planning would be given any possible on-orbit use of the available volumes involved. (The ET LH2 tanks is over 53,000 cubic-ft while the LOX tank is another 19,000 cubic-feet and neither includes the inter-stage volume)
The most prominent downside is most of the more expansive concepts take some serious EVA work to accomplish. A LOT of serious EVA work to be upfront and the issue is no Space Suit is really designed to be capable of that kind of work because no one requires them to. It’s a very fair point when it comes to ‘wet’ module design but the main counter is that WVB along with several other engineers from his design team, (aka a bunch of engineers in their mid-to-late 50s at the time) stuffed themselves into space suits and dove into the neutral buoyancy simulator at Marshall and actually put their ideas on building a wet lab to the test. (And from a maintenance man’s perspective my hard hat is off to them for putting their ideas to the test instead of leaving for someone else to try) The final report was that it was quite doable, (but keep in mind they were using modified Gemini suits which in fact were horrible for EVA use) and that extra hand holds and fittings would be helpful. Now take into account that unlike the S-IVB stage used previously the ET had significant pre-installed openings that were only sealed by a bolt-on door and which was remarkably easy to expand to a size allowing a fully suited astronaut to enter and exit and OTHER than the space-suit issue the utility of the ET is obvious.
Again the main issue is there are/were no space suits designed for extensive manual on-orbit work.
But as a very “plus” column outcome the requirements for possible commercial use, (which OTL NASA fought tooth-and-nail) would have required a ‘fix’ for the loose insulation as well as some beefing-up of the ET general structure. But in the common “Chicken/Egg” issue delivery of an ET to orbit requires some sort of on-orbit presence by someone who would utilized the tank before such a tank could be delivered. (The often mentioned idea of ‘storing’ ET’s on-orbit neglects the very real and prolonged danger this represents as well as the number of international agreements it violates. Hence the need for an ‘on-orbit’ presence to USE the tanks before they can be delivered catch-all) Still an extended mandate and more direct support FROM commercial interests is likely to engender similar reciprocation from NASA in the form of less hostility towards those same commercial interests.
So as per the illustration in the SSI document on page 37 (page 51-53 shows a much more complex but capable ACC Service Module Station Core) showing an ACC fitted out with a Spacelab module and a Shuttle mission that carries the crew to orbit along with a cargo bay carried ‘emergency’ return vehicle “getting” that capability may be pretty straight forward. And if that is too much work the possibility of a ‘dry’ module launched on a sidemount, or inline SDV is always there.
What is around to prevent this is simply that in capability and possibility utilizing the STS and External Tank to their logical conclusion presents quite possibly far too MUCH to both NASA and others. Even if we assume no more than the budget given to construct the ISS OTL it becomes clear that the amount of pressurized space available is far too vast for that budget to outfit. Worse the required on-orbit operations will require a drastic and extensive re-working of space suits into models capable of being used efficiently and effectively for long hours in addition to a paradigm shift in the planning and execution of EVA activities. Even if we only assume that half (4 of 8) a “good” year’s flights deliver an ET to a usable orbit and make it available it would rapidly outstrip both the available budget and capability available to NASA or anyone else to utilize. While it won’t necessarily stay that way the situation will not change rapidly and as noted above it cuts out a majority of large aerospace companies who are not directly tied to ACC or other modular construction contracts. (A disincentive both for NASA and Congress)
And trust me when I say this hurts to admit for there was a time, not very long ago when the idea of calling a 300 foot diameter, (eight LH2 tanks connected by eight ‘angle’ segments carried up as ACC cargo) AG station capable of handling over 200 people in comfort “too much” would be unthinkable but in truth it is very much so given the capability available to utilize it let alone build it. Keep very much in mind that most industrial research benefits more from a smaller scale experimental system and specifically requires micro-gravity to function. One could argue that ANY AG station is only useful for curiosity sake since any BLEO operations are likely not going to include AG.
There is also the consideration of how this effects general commercial operations which will change significantly as well. Once you have an on-orbit presence the temptation to utilized it to expand and service commercial operations means that many initial and advanced concepts that dealt with everything from LEO-cluster arrays, (a non-starter when you have a lot of infrastructure and operations in LEO already) to cheaper access, (SpaceX and BO for example are very unlikely to be founded) get pushed aside. On the other hand you have MEO and GEO satellites that are now designed to take advantage of what on-orbit services are offered. Designed to be serviced and repaired and there is incentive to make them even bigger, more robust satellites with more of a ‘plug-and-play’ architecture to facilitate such activities and upgrades. Which further reduces the need for general space launch rather than enhances it. So we can try and assume factors like Space Tourism or industry but really there were somewhat sound reasons NASA and most official space agencies opposed the concepts. (In the industrial case the rationalizations are marginal at best anyway but this way there are at least more opportunities to experiment and possibly find viable business models)
It's arguably a "win" but the question of how much "better" it would be if probably very subjective
Randy