SCIENCE
So, how are those commercial replacements working out for you, NASA?
This week marks the fifteenth anniversary of the final Space Shuttle return, heralding the conclusion of NASA’s Space Shuttle program. Space Shuttle Atlantis touched down at the Shuttle Landing Facility (SLF) at Kennedy Space Center 15 years ago, completing the program’s last mission.
STS‑135, originally designated STS‑335, was the Launch‑On‑Need (LON) mission arranged on short notice after the Endeavour’s flight 134. LON missions had been a safety measure since the Columbia tragedy, allowing a spare orbiter to be launched if a primary shuttle were compromised. Typical LON assignments received separate STS‑3xx designations—for example, STS‑317 accompanied the rescue mission for STS‑116, and STS‑318 followed STS‑117. Although the program was intended to wind down with STS‑134, lawmakers and NASA executives chose STS‑135 as the final flight.
Without a ready LON shuttle at that juncture, a damaged Atlantis would have necessitated crew evacuation via Soyuz capsules from the International Space Station (ISS). Moreover, the mission used only four crew members, the smallest crew size since Challenger’s mission 6 in 1983.
The four astronauts comprised Commander Christopher Ferguson—who later joined Boeing’s Commercial Crew Program and was slated to fly the Starliner capsule—pilot Douglas Hurley, who went on to command SpaceX’s Crew Dragon test flight in 2020, and mission specialists Sandra Magnus and Rex Walheim.
Atlantis launched on 8 July 2011 and returned on 21 July, formally ending the shuttle era. The United States did not immediately regain a domestic crew‑launch capability; it continued to rely on Russian Soyuz spacecraft to ferry astronauts to and from the ISS.
Subsequent contracts with SpaceX and Boeing eventually restored U.S. launch capacity, but only with SpaceX’s Crew Dragon becoming operational in 2020 and Boeing’s Starliner only achieving flight‑test status in haa?
SpaceX’s Star‑liner program faced setbacks, prompting NASA to return the capsule empty from the ISS and reschedule a later crewed flight on a SpaceX vehicle in 2025. A definitive launch date for the Starliner’s crewed mission remains unannounced.
In the fifteen years since the last shuttle return, the U.S. space program has navigated a complex transition. Rather than a single robust platform, the strategy has shifted to dual commercial providers to reduce risk, yet operational reliability has lagged behind expectations. Uncertainty persists regarding SpaceX’s willingness or capacity to sustain Fleet operations beyond the contracted missions, while Boeing’s Starliner remains unlaunched.
Despite challenges, both companies anticipate that their vehicles—SpaceX’s reusable Dragon and the planned Starship—will be capable of meeting ISS demands through the program’s conclusion and beyond. For SpaceX, the eventual transition to Starship appears inevitable.
The fates of the retired shuttles themselves vary. Atlantis now resides in a display configurated to appear airborne, and the California Science Center exhibits Endeavour mounted on its external tank and solid boosters as if launch‑ready. Discovery’s future remains uncertain, with proposals ranging from relocation to Houston, Texas, to potential reuse of Orion capsules.
