Working as an Astronaut

Every trip into space is different, but to get a feel for what it's like to work and live as an astronaut, let's look at an idealized NASA mission involving a space shuttle launch to the International Space Station (ISS), where a crew switchover is performed.

­Preparations for a launch actually begin two w­eeks before a mission's launch window. At a launch readiness review, the shuttle mission management team, other top-level NASA officials, space shuttle program managers, engineers and contractors meet at Kennedy Space Center for a thorough review of the mission. The group conducts a comprehensive evaluation of the entire mission, including the readiness of the space shuttle, flight crew and payloads to determine if everything is set to proceed with launch. After the review is completed, the chairman of the mission management team conducts a poll of the team members. If there are no unresolved issues, the members then sign a "Certification of Flight Readiness" to verify that all flight preparation processes to that date have been successfully completed. The official launch date is then set and announced.

At approximately the same time, the seven astronauts scheduled to ride on the shuttle enter the spacecraft to rehearse for the launch. All launch procedures and conditions are duplicated precisely to make the rehearsal seem as real as possible. That means the astronauts dress in their bright orange pressurized flight suits. It also means they participate in a full practice countdown.

The launch takes place at Launch Complex 39 at the Kennedy Space Center (KSC). There, a shuttle launch team consisting of around 500 professionals manages the final launch procedure. The official countdown starts at T-43 hours (read "T minus 43 hours"), which is actually three days before liftoff. The extra time is built in to ensure all launch preparations can be completed. It takes roughly 72 hours to conduct a shuttle countdown.

After the countdown clock starts ticking, the Launch Control Center is staffed around the clock. As subsequent countdown milestones are met, however, the composition of the team will change considerably, depending on which system is being prepared. For example, fueling the shuttle requires several teams working at key milestones. At T-27 hours, a crew begins operations to load cryogenic reactants into the orbiter's fuel cell. At T-19 hours, another crew begins final preparations of the orbiter's three main engines for main propellant tanking and flight. And at T-6 hours, a third crew begins loading the external tank with about 500,000 gallons (1.9 million liters) of cryogenic propellants.

The fueling process is completed by the T-3 hour mark. At this time, a fresh team begins at the Launch Control Center and will remain until the launch. The T-3 hour mark is also when the astronauts arrive to the launch pad and enter the shuttle. Prior to this, the astronauts stay at the Operations and Checkout Building, which is part of the KSC campus. They walk out of the Operations and Checkout Building clad in orange pressure suits and ride an AstroVan to the base of Launch Pad 39A. They climb into an elevator and ride up to the level where they enter the crew compartment of the shuttle. Then they are secured in their seats, where they await the final countdown.

Beginning approximately 15 minutes before launch, the shuttle launch team checks to make sure all systems are working well. If everything is found ready, the shuttle launch director conducts a poll of KSC management. Assuming all responsible personnel agree, the launch director gives permission to proceed with the countdown to the NASA test director (NTD). The NTD in turn sets in motion the final nine minutes of the countdown, which are controlled automatically.

It's almost launch time! What happens next? Read on to find out.