Shuttle Mission: STS-110
Orbiter: Atlantis
Date: April 8

Did You Know?

When members of the flight crew arrive at the launch pad, the Closeout Crew (who wear white coveralls), assist the astronauts as they don their helmets, adjust and secure their equipment, enter the orbiter and are strapped into their seats. Once all astronauts are aboard the Shuttle, the Closeout Crew seals the crew module hatch about two hours before the launch.

It takes about 50 minutes to get all flight crew members strapped into their seats. The astronaut's seats are folded up, unhooked from the floor, and stored away while on orbit.

At T-2 hours, NASA's two Solid Rocket Booster (SRB) Retrieval Ships, Freedom Star and Liberty Star, will be on station in the Atlantic Ocean about 7.5 miles from the predicted impact points of the rocket boosters.  While there, they will perform electronic searches  to insure the area is clear of shipping. The two ships departed from Cape Canaveral Air Force Station will be on station in the Atlantic off the coast of Jacksonville, FL at launch time.

After launch, the boosters are jettisoned about two minutes into flight and impact the ocean about 5 minutes later.

Divers aboard the ships pump water out of the boosters and prepare them for towing back to Hangar AF at the Cape Canaveral Air Force Station. Depending on weather conditions, and the progress of recovery efforts, the boosters are expected to return to Hanger AF at the Cape Canaveral Air Force Station.

The motor segments will then be disassembled and shipped back to Thiokol in Utah for refurbishment and refilling within a week. The aft skirts and forward frustums are refurbished here at Kennedy Space Center.

Walkout of STS-110 Crew

Flight crew departs the Operations and Checkout Building (O&C) and proceeds to the Launch Pad (live on NASA TV).

Astronauts arrive at the launch pad and begin entering the orbiter.

Close-out Crew begins sealing off Atlantis' crew compartment.

At approximately T-50 minutes and counting, Pilot Stephen Frick configures switches in the cockpit to pre-activate the orbiter's three water spray boilers.  Each of the orbiter's three hydraulic systems has a boiler used to cool the system's hydraulic fluid and Auxiliary Power Unit lubrication oil. Boiler steam is vented overboard.

During the launch, orbital checkout, and reentry through landing phases, the spray boilers are activated if the hydraulic fluid exceeds 208 degrees Fahrenheit or 250 degrees Fahrenheit for the lubrication oil. The spray boilers are located in the orbiter's aft fuselage and hold about 120 pounds of water.

At T-45 minutes and counting, the Terminal Count Range safety closed-loop test begins. This test verifies the paths the destruct signal would travel and confirms that the Shuttle’s range safety receiver responds correctly to the commands sent. This is also a health check of the range safety signal. Console operators in the Eastern Test Range Control Center at Cape Canaveral Air Station will also get verification that the orbiter has received the signal.  This test normally takes about five minutes to complete and is done to ensure down range shipping lanes and the booster splashdown area are clear and that the tracking station is ready.

Also at this time, NASA Test Director, Steve Altemus, coordinates with Mission Control in Houston, Texas, to switch Atlantis' S-band antennas to high power mode and to configure the onboard communications system so that it will transmit and receive by radio at liftoff (during launch countdown, communications with the orbiter are hard wired).  This system can communicate either directly between the orbiter and ground or through the TDRS satellite system.

By T-40 minutes and counting, the Ground Launch Sequencer mainline computer program is active and begins processing data. This program will monitor various key commands and systems prior to assuming control of the countdown at the T-9 minute and counting mark.

By T-30 minutes, the Orbital Maneuvering System (OMS) gaseous nitrogen tanks have been pressurized for launch. Gaseous nitrogen is used to operate the valves allowing the hypergolic propellants to flow into the OMS engines during flight.

At about this same time in the countdown, the post launch inspection and safing teams begin assembling approximately one mile from the launch pad.

Within the next minute or so, the preflight test of Atlantis' Master Events Controller (MEC) is completed. The MEC relays commands from the orbiter's computers to fire explosive charges to the Solid Rocket Booster hold-down bolts at launch and to separate the tank and twin boosters in flight.

By the T-25 minute mark, the Closeout Crew has evacuated the launch pad.

Over the next few minutes, Commander Michael Bloomfield performs a series of voice checks, configures Return-To-Launch-Site (RTLS) altimeter settings, and completes other preflight checklist items.

Also during this period, the Kennedy Space Center Launch and Johnson Space Center Flight Directors are briefed about impending launch and RTLS weather conditions.