Wednesday, January 15, 2014

For Want of a Mission - The Space Launch System; STS Revisited, With All The Same Worries

As I mentioned in my last entry ("Dreaming of the Final Frontier"), there were concerns about what the space shuttle would do when it was being developed. As initially conceived, the shuttle was to support other missions, provided, of course, that those other missions were funded. As it turned out, NASA was given kind of a devil's deal; you can have a space station, extended lunar missions, or the shuttle, but not all of them, in fact, only one. The initial push for the shuttle during the Nixon years indicated that there was a firm belief that it could be used as a "means", basically building the road so that you could not only travel down it, but build alongside. Everything else would follow.
That's not exactly how it happened, of course.
After the summer of 1975's space settlement studies, it was increasingly apparent that while the shuttle had the capability, the planned missions were a far cry from what had been imagined.
One thing that did emerge from the space settlement studies were shuttle derived launch vehicles, or shuttle derived vehicles, SDV, for short. These were to be used for the really heavy lifting that would be necessary for space settlement to take place. 
If you look at these images, you can see a seed being planted, one that has persisted to this day. The Space Transportation System had the potential for a lot of growth.

The shuttle compared to proposed SDV's.
From "Space Settlements - A Design Study", NASA, 1976.
Other launch vehicles emerged from this study as well, namely the very large F-1 Flyback Booster. While not truly a shuttle derived vehicle, it was still impressive.

F-1 Flyback booster concept.
From "Space Settlements - A Design Study", NASA, 1976.
And as I mentioned in my previous entry, Congress, as well as an apathetic administration, killed any further studies. The SDV's, however, lived on.
By 1978, you find Morton Thiokol, the prime contractor for the SRB's, looking into large SDV's, capable of lobbing huge payloads into orbit. If you look at this design, you can see where this sort of thinking would eventually lead. 
SDV concept, 1978
Courtesy NASA/Morton Thiokol, via Wikipedia
The idea persisted because many at NASA considered the shuttle to be just one component of a growing space infrastructure. While optimistic,  this was somewhat unrealistic, given that NASA's budget had been steadily eroded for a decade by the late-1970's. Still, the studies continued. 
As the 1980's rolled along, with President Reagan's push for a space station, the SDV's began to resurface, with one design leading the pack.
That's C as in "cargo".
Final design for Shuttle-C
Courtesy NASA/MSFC
If you look at the comparison drawing up there, you can see the genesis of Shuttle-C. In theory, it was extremely simple; replace the orbiter with a self propelled cargo container. When you look at a space shuttle orbiter, you are in effect looking at a 240,000 lbs. (109,000 kg) payload. The shuttle was designed to handle around 64,000 lbs (29,000 kg) as payload (in practice, the "useful" load was 55,250 lbs, or 25,000 kg). If you took the orbiter off, used two or three space shuttle main engines (SSME's), you could, theoretically, create a launch vehicle that could lob a considerable amount. 
Most designs for the Shuttle-C called for it to lift just over 140,000 lbs. (63,500 kg) to LEO. That is more than twice the "useful" payload of the space shuttle. 
Unfortunately, the development costs for Space Station Freedom killed Shuttle-C, and by 1990, any serious work on the design ground to a halt, though the aerospace industry continued to play with the design, as did some at NASA.
Other independent design studies would come along. Robert Zubrin proposed a variant he called "Ares", which would use shuttle derived components for use in his "Mars Direct" proposals.
Zubrin's Ares, courtesy Wired/Mars Underground
When you look at Zubrin's proposal, it seems so very simple. Use SSME's mounted in a pod on the back of the external tank. Extended SRB's wouldn't be that difficult. The only real challenge was the upper payload shroud. 
Of course, dreams of launching a mission to Mars by 1999 never became more than just dreams, so Zubrin's Ares remained only a paper tiger, though an impressive one.
When President G.W. Bush proposed the Vision for Space Exploration (VSE) in January, 2004, he proposed new craft and new missions; a return to the Moon, new launch vehicles, etc. Removing the lunar mission concept, the proposed CEV was really a lackluster replacement for the shuttle. The new launch vehicles that grew out of the VSE would also be named "Ares", but were only superficially similar to Zubrin's ideas. Still, they relied upon the STS as a starting point, even if the core in would be a fairly new design of slightly larger diameter.
Ares V and Ares I.
Courtesy NASA via Wikipedia
Only one Ares launch vehicle was ever tested, the Ares I-X flight on October 28, 2009 - 

As has been the case too often, when a new administration entered the picture, VSE was doomed, and with it the Ares boosters. There was plenty of criticism of the VSE, such as mandating a date for the shuttle stand down and withdrawal from the ISS, but this pattern of changing NASA plans was set several presidents back. However, politics, with all the assorted headaches, is not something I am going to venture too far into here. 
As the Obama administration killed VSE, it changed NASA's goals once more. No missions to the Moon for the immediate future. Development of commercial human spaceflight. Asteroid retrieval missions. A new spacecraft for exploration. Not surprisingly, that capsule would simply be the revamped Orion, initially designed for the VSE goals. 
The heavy lift boosters that came out of this administration's plans look familiar as well.
The various SLS configurations.
Courtesy NASA via Wikipedia
The currently unnamed SLS boosters are, once more, shuttle derived launchers. Everything here harkens back to those designs from the summer of 1975. The diameter of the core components is based upon external tank designs, the solid rocket boosters are simply stretched versions of the SRB that lobbed the shuttle into orbit. The engines are really no different, of course, choosing the proven RS-25 series, the SSME from the shuttle.
Bottom line; SLS is simply STS, Phase II. 
And sadly, looking at the track record, I fear that these designs are begging for missions that are not being funded properly or simply do not exist at this time as part of NASA's goals. Like the shuttle and STS before it, the SLS seems to be a powerful machine in want of a mission. The recently passed budget is smaller than needed. There are plenty of questions about the Orion MPCV, and its budget is shrunk as well. NASA's budget, and therefore its space mission scope, has never been smaller. We feared that the shuttle would never fly, and the budget NASA was working was paltry. While the current budget, adjusted for inflation, is comparatively better, NASA is not just developing one system, but in effect three (the Orion MPCV, the SLS, and helping to fund commercial crew vehicles). 
With the revelation of the most recent budget, and NASA's narrowed scope for human spaceflight, I worry that when 2016 rolls around, the next administration will continue the glorious old tradition of killing the previous one's space programs. And with its large price tag, SLS will be ripe for the picking.

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