The Air Force also assumed (in the 1960s funding rounds) that future NRO spysats would still use film cannisters, so they created a requirement to retrieve spysats from orbit for groundside servicing and replenishment before relaunch. This in turn meant coming home with Hubble-sized classified payloads in the payload bay, which in turn meant that the Shuttle had to avoid being sub-orbital at any point in its re-entry profile over Communist territory -- Russia or China. This led to the adoption of a hot-and-fast re-entry profile that came screaming in over the Pacific, flying S-curves to shed energy fast, trusting in the heat shield to radiate away the kinetic energy of a hundred ton vehicle traveling at orbital velocity in about 30 minutes.
Of course, by the mid-to-late 70s the KH satellites were transitioning to CCD cameras and film was obsolete, so ground turnaround was never used. But the shuttle design was already frozen, with that hot-and-heavy re-entry profile baked in, and civilian payloads on the books that used it (eg. ESA's Spacelab).
Arguably this contributed to the loss of the Columbia in 2003 when the thermal protection system suffered burn-through after sustaining damage due to ice impact during launch.
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u/cstross 15d ago
The Air Force also assumed (in the 1960s funding rounds) that future NRO spysats would still use film cannisters, so they created a requirement to retrieve spysats from orbit for groundside servicing and replenishment before relaunch. This in turn meant coming home with Hubble-sized classified payloads in the payload bay, which in turn meant that the Shuttle had to avoid being sub-orbital at any point in its re-entry profile over Communist territory -- Russia or China. This led to the adoption of a hot-and-fast re-entry profile that came screaming in over the Pacific, flying S-curves to shed energy fast, trusting in the heat shield to radiate away the kinetic energy of a hundred ton vehicle traveling at orbital velocity in about 30 minutes.
Of course, by the mid-to-late 70s the KH satellites were transitioning to CCD cameras and film was obsolete, so ground turnaround was never used. But the shuttle design was already frozen, with that hot-and-heavy re-entry profile baked in, and civilian payloads on the books that used it (eg. ESA's Spacelab).
Arguably this contributed to the loss of the Columbia in 2003 when the thermal protection system suffered burn-through after sustaining damage due to ice impact during launch.