The Spy Satellite HEXAGON: Ah, Now The Shuttle’s Design Makes Sense.

Whilst the Space Shuttle will always be one of the most iconic spacecraft that humanity has created it’s design was one of compromises and competing objectives. One of the design features, which influenced nearly every characteristic of the Shuttle, was the requirement from the Department of Defense that stipulated that the Shuttle needed to be able to launch into a polar orbit and return after a single trip around the earth. This is the primary reason for the Shuttle being so aeroplane like in its design, requiring those large wings so it has a long downrange capability so that it could return to its launch site after that single orbit. The Shuttle never flew such a mission, but now I know why the DoD required this capability.

It was speculated that that particular requirement was spawned out of a need to capture spy satellites, both their own and possibly enemy reconnaissance craft. At the time digital photography was still very much in its infancy and high resolution imagery was still film based so any satellite based spying would be carrying film on board. The Shuttle then could easily serve as the retrieval vehicle for the spy craft as well as functioning as a counter intelligence device. It never flew a mission like this for a couple reasons, mostly that a Shuttle launch was far more expensive than simply deorbiting a satellite and sending another one up there. There was also the rumour that Russia had started arming its spacecraft and sending humans up there to retrieve them would be an unnecessary risk.

The Shuttle’s payload bay was also quite massive in comparison to the spy satellites of the time which put further into question the DoD’s requirements. It seems however that a recently declassified spy satellite, called HEXAGON, was actually the perfect fit and could have influenced the Shuttle’s design:

CHANTILLY, Va. – Twenty-five years after their top-secret, Cold War-era missions ended, two clandestine American satellite programs were declassified Saturday (Sept. 17) with the unveiling of three of the United States’ most closely guarded assets: the KH-7 GAMBIT, the KH-8 GAMBIT 3 and the KH-9 HEXAGON spy satellites.

…

“I see a lot of Hubble heritage in this spacecraft, most notably in terms of spacecraft size,” Landis said. “Once the space shuttle design was settled upon, the design of Hubble — at the time it was called the Large Space Telescope — was set upon. I can imagine that there may have been a convergence or confluence of the designs. The Hubble’s primary mirror is 2.4 meters [7.9 feet] in diameter and the spacecraft is 14 feet in diameter. Both vehicles (KH-9 and Hubble) would fit into the shuttle’s cargo bay lengthwise, the KH-9 being longer than Hubble [60 feet]; both would also fit on a Titan-class launch vehicle.”

HEXAGON is an amazing piece of cold war era technology. It was equipped with two medium format cameras that would sweep back and forth to image an area, capturing an area 370 nautical miles wide. Each HEXAGON satellite carried with it some 60 miles worth of film in 4 separate film buckets which would detach from the craft when used and return to earth where they would be snagged by a capture craft. They were hardy little canisters too with one of them ending up on the bottom of an ocean but was retrieved by one of the navy’s Deep Submergence Vehicles. There were around 20 launches of the HEXAGON series of craft with only a single failure towards the end of the program.

What really surprised me about HEXAGON though was the resolution they were able to achieve some 30+ years ago. HEXAGON’s resolution was improved throughout its lifetime but later missions had a resolution of some 60cm, more than enough to make out people and very detailed images of say cars and other craft. For comparison GeoEye-1, which had the highest resolution camera on an earth imaging craft at the time of launch, is only just capable of a 40cm per pixel resolution (and that imagery is property of the USA government). Taking that into consideration I’m wondering what kind of imaging satellite the USA is using now, considering that the DoD appears to be a couple decades ahead of the commercial curve.

It’s always interesting when pieces of a larger puzzle like the Shuttle’s design start falling into place. Whilst it’s debatable whether or not HEXAGON (and it’s sister craft) were a direct influence on the Shuttle there’s enough coincidences to give the theory a bit of credence. I can see why the USA kept HEXAGON a secret for so long, that kind of capability would’ve been down right scary back in the 80’s and its reveal makes you wonder what they’re flying now. It’s stuff like this that keeps me obsessed about space and what we, as a species, are capable of.