I think there was also a bit of a catch-22: the Shuttles were so expensive to operate that they had no money left to design and build a replacement.
That was what I was looking for when I found the article I posted. I vaguely remember that a filler was planned to be used to fill the space left by a missing tile.
Or the space station they were originally designed to construct and service. It took over a decade after they entered service for the ISS to be approved, and another two decades before it was fully assembled, right before retirement of the STS. The original plan was that the shuttles would operate on two week to a month centers with each shuttle flying at least three to six times a year, with increases in rate as experience with the system improved, and it would serve as the exclusive heavy launch system for DoD, NASA, and eventually commercial payloads from the United States. Instead, the launch rate slowed; no shuttle ever flew more than four times in a 12 month period , and that was back when only Columbia and Challenger were operational, and after the Columbia failure they were struggling to get four flights out of the remaining three OVs. (2009 was a banner year with five flights as they raced to complete the ISS before retirement of the Shuttle fleet.)
The attempt to develop a replacement in the X-33, which was going to be a technology demonstrated for the full sized commercial Lockheed Martin VentureStar, were stymied as much by poor management decisions to utilize immature technologies as budget limitations, but regardless there was little constant initiative to develop a replacement, and the Constellation program with the Crew Exploration Vehicle went back to a capsule-on-stick expendable paradigm. (Technically the CEV was intended to be reusable as it its commercial successor the Orion Multi-Purpose Crew Vehicle, but the ascent propulsion system is not.) Frankly, there is a good case for not using large winged or lifting body vehicles for heavy lift; for the STS that was a political decision made early in the development long before contractors have provided even the initial concepts, and for reasons having to do with avoiding having competing efforts for heavy lift and personnel transport. It didn’t work out well for reasons that are obvious now but were not as apparent then, especially in the assumptions about how often it would fly and how reliable it would be.
My pick for a future heavy lift vehicle is most along the lines of the Chrysler SERV proposal which was rejected for being too different (and ostensibly for the technology advances that would be required for its base plug aerospike propulsion system) but that offer a system that would be more robust and flexible than any winged shuttle, albeit not as capable of the desired cross range that the Air Force required of the Shuttle for the once-around polar orbit mission that it never flew. Flying such a vehicle from a rudimentary sea platform–little more than a raft of floating barges-- and powered landing offshore would reduce most of the logistical problems that plague such a system operating in the conditional rocket launch paradigm.
While the concept of winged spaceplanes seems appealing in that they look like airliners, the reality is that space launch vehicles operate in very different environments from aircraft and the wings are parasitic mass that has to be carried and protected throughout the entire flight only to provide benefit in the last few minutes of descent, which makes no sense from any operational standpoint.
Stranger
Note that Skylab was intended to be used and assisted by the shuttles. The delays in the shuttle program caused by annual budget cutbacks meant that Skylab’s orbit decayed before it could be saved. The ISS was the “Plan B”, space station-wise, which explains the long gap, etc.
All too often with the US space program people decide to cut back a bit on a program’s annual budget, stretching it out over more years and making the total cost greater.
and don’t forget that it also makes the jobs last longer…
The thing I read back before the accidents said that the secret Keyhole spy satellites were one of the drivers for the large cargo bay - 15 feet in diameter.
There is a story that a government agency asked that the cargo bay be larger. When NASA asked, “Why?” their response was, “It isn’t large enough.”
That is not quite correct. From Space Shuttle: The History of the National Space Transportation Program, pg 101:
Accommodating all potential Department of Defense missions required an orbiter that could handle payloads up to 60 feet long, could launch 40,000 pounds into polar orbit, and over 65,000 pounds into a due-east orbit. This was significantly more than the payload specified by the NASA Phase A RFP, and more than seemed possible while still keeping the vehicle size within the realm of possibility. Of the critical design parameters of the Space Shuttle, only the maximum payload width of 15 feet was based primarily on a potential NASA requirement, this being a projection that any future space station would be built using modules of that diameter. The NASA was seemingly even somewhat unsure of this requirement, and was willing to accept payload bay diameters as small as 12 feet, while at the same time asking various contractors to investigate ones as large as 22 feet.
As it turned out, the 15 foot diameter payload requirement was fortuitous as it was sufficient to accommodate the Hubble Space Telescope, but the origin of the requirement was to support space station modules.
Stranger
Eh, if the payload bay had been 12 or 18 feet, the Hubble would have been designed to match that, too. It’s the Puddle Anthropic Principle.
No; the 2.4 m diameter f/1.2 primary mirror and the 4.2 m overall diameter were based on commonality with the KH-11 surveillance satellite. While the HST is not, as sometimes suggested, just a repurposed KH-11 (the optics requirements are very different), the commonality allowed reuse of fixtures and some housing designs, which likely saved considerable budget in terms of non-recurring engineering for a one-off satellite. A payload bay that could accept only a 12 ft diameter payload would have likely had about a 2.1 meter aperture, which would have significantly reduced the light gathering capability of the telescope (to about 75%). Of course, the KH-11 size was almost certainly based on the shuttle payload bay capability, but again, that came from a NASA requirement, not an NRO or DOD one.
Stranger
It came out in the investigation after Challenger that at the time, there were NEVER 4 operational shuttles. Not at the same time. Let’s call them A, B, C, and D. A is in orbit and B is on the pad being loaded. C and D are in a hanger missing parts. When A lands, after it’s been safed, it is cannibalized for parts to complete C. Then any parts that D needs that are still on A are removed and put on D. After B completes its mission it happens again and C and D are now flight ready.
The problem with the STS was it was supposed to do everything and do it well. Look, a mini-van can be useful, but it can’t do what a Corvette can do. And a Corvette is great but it can’t do what a Freightliner can do. STS was the lone hammer in the tool bag and the missions turned out not to be ALL nails.
I’m not sure what specific part of the Rogers Commission report you are referring to but it is important to note that the first flight of Atlantis (the fourth OV in the fleet) was STS-51-J in October 1985, and the in-flight catastrophic failure of Challenger was STS-51-L in January 1986, barely four months after Atlantis entered service, so until Endeavor was fielded there was only a brief period where the fleet was even comprised of four OVs. It was always understood that some parts, and in particular engines, valves, and composite overwrapped pressure vessels (COPVs) would have to be removed and serviced or refurbished between missions because of their limited service life. There are also a number of modular components that were intended to be swapped out to support different kinds of missions, most obviously the Canadarm manipulator (there were actually several evolutions of the manipulator) but also different instrumentation packages, experiment and payload mounting fixtures, and even the life support system would be modified for different crew and mission duration requirements). One of the Air Force objections to the “Blue Shuttle” program was that they would have to share OVs with NASA, and thus, be subject to mission delays and limitations on orbiter availability, especially since their polar orbit missions would be very different in nature and require a unique configuration.
So while it is true that not all four OVs, either in the pre- or post-Challenger fleet were all at operational status simultaneously and shared compnents between them, to call it “cannibalized for parts” gives the misapprehension that this was some kind of desperate, ad hoc effort to keep the fleet alive rather than a planned effort of regular maintenance and refurbishment that wasn’t a surprise to anyone actually working at the program level. Nor was their any requiement or operational need for all OVs to be operational simulataneously, and in fact, NASA mission control could only support two missions simultaneously, and in terms of vehicle processing it would have been literally impossible to have more than two missions launched out of the Cape overlapping.
Stranger
In line with this, here is Enterprise with ET and SRBs at SLC-6 in Vandenberg, CA undergoing fitment checks in 1985: https://mk0spaceflightnoa02a.kinstacdn.com/wp-content/uploads/2016/01/enterprise.jpg
Enterprise couldn’t fly orbitally but they were serious enough to use an actual orbiter to test the pad facilities.
Nineteen separate times there were two shuttles on Pad 39A and B in Florida. Here is Atlantis and Endeavor both ready to go: https://upload.wikimedia.org/wikipedia/commons/5/53/Space_shuttles_Atlantis_(STS-125)_and_Endeavour_(STS-400)_on_launch_pads.jpg
However there were statements in the Rogers Commission report that discussed cannibalization of parts. Even before Challenger there was concern once four OVs became operational in 1986 (with one sent to Vandenberg in CA), there would be no OVs left to borrow parts from:
https://history.nasa.gov/rogersrep/v1ch8.htm
The report indicates this was a funding and management issue, not necessarily one inherent to the design. For a period in 2017, spare parts and maintenance of the Navy’s F/A-18 was so poor that fleet readiness was only 33%. But this doesn’t indicate the aircraft was incorrectly designed: https://www.popularmechanics.com/military/aviation/a22778556/us-navy-fighter-shortage-progress/
Yet there is a good argument that given the shuttle’s conflicting design priorities of budget, schedule, performance and maintainability, that maintainability lost out. However it has never been convincingly explained what alternate design could have achieved the mission requirements (inc’l maintainability), given the same budget and using early 1970s technology.
It’s easy to look at paper designs which never progress to the intense technical scrutiny of late development stages, and think they would have worked. If you don’t do extensive and realistic modeling of structures, load paths, margins, etc, lots of designs look nice. This one looks nice, that doesn’t mean it would have worked: https://photos.smugmug.com/photos/i-2tBk3CN/0/1f54f426/O/i-2tBk3CN.jpg
