NASA mission STS-135, scheduled to launch on July 8, 2011, will be the final flight of the venerable and invaluable space shuttle program. Atlantis will be the last member of the surviving shuttle fleet to slip the surly bonds of Earth, carrying a crew of four astronauts into orbit for a 12-day resupply and repair mission to the International Space Station.

As this is the final space shuttle flight — and thus the last chance to use the shuttle’s massive payload capacity to service the ISS — Atlantis is jam-packed with components and supplies. (Not to worry, the shuttle’s swan song isn’t strictly a cargo run. Atlantis will test a new robotic system for repairing and refueling satellites in orbit — a function that will be necessary now that the shuttle’s massive orbital work platform and robotic grapple arm are being retired.) This cargo duty partially explains one of the more extraordinary aspects of STS-135: its four-man crew.

Not since the maiden flight of Challenger in 1983 has a space shuttle operated with just a four-man complement. This reduced crew size can accommodate the extra payload on STS-135, but the payload isn’t the reason Atlantis is flying with the smallest crew in 28 years. That’s just a bonus.

WHY DOES THE LAST SPACE SHUTTLE FLIGHT HAVE THE SMALLEST CREW IN 28 YEARS?

Get the answer.

The last space shuttle flight has smallest space shuttle crew because it’s the last space shuttle flight. Bear with me, that’s not a trick answer.

Since the loss of Columbia in 2003, NASA has strictly required a Launch On Need (LON) parallel mission for every shuttle flight. Put more simply, every time a shuttle flies, another shuttle is prepped on standby for an orbital rescue mission, should the primary shuttle suffer damage during launch that prevents it from safely returning to Earth.

STS-135 was originally STS-335, the Launch On Need standby flight for STS-134, the final flight of Endeavour that was intended to be the last shuttle mission. As NASA had already spent the money getting Atlantis flight-worthy, they convinced Congress to backdoor STS-335 into STS-135 — provided Endeavour didn’t need a rescue during its final flight. When Endeavour landed safely on June 1, 2011, STS-135 was finally, officially a go.

However, as both Discovery and Endeavour have been retired, there is no rescue shuttle on standby for STS-135. The Launch On Need plan for Atlantis involves not one, but a pair of three-man Russian Soyuz capsules, which can rescue two shuttle astronauts apiece with the help of each capsule’s respective pilot.

Requiring two LON craft is a daunting enough prospect, but flying Atlantis with a standard 6-man crew would require a logistically staggering triple-Soyuz Launch On Need mission. That was a non-starter for greenlighting STS-135, so the Atlantis mission profile was developed for a modern minimum four-man crew. (Only the first four shuttle flights, all shakedown missions for Columbia, included two-man crews. No shuttle has ever flown with a three-man complement.)

That’s not just a scientifically sagacious skeleton crew, it’s a fundamentally unforgettable return flight for Geek Trivia.

The quibble of the week

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