Launch Complex 39 at the Kennedy Space Center has served as the springboard for U.S. human spaceflight since the Apollo lunar landing program in the 1960s. The first launch conducted from one of the two LC 39 pads was Apollo 4 on Nov. 9, 1967. Since then, teams staffing the consoles in one of the Launch Control Center firing rooms have sent into space astronauts who walked on the moon, interplanetary explorer spacecraft destined for the far reaches of the solar system and Space Shuttle crews to conduct research and to service, deploy and retrieve spacecraft.

The first Space Shuttle launch was conducted from Pad 39A on April 12, 1981. Today, Shuttles lift off regularly from either Pad 39A or B under the management of the launch team in the Launch Control Center.

The Space Shuttle launch team is a highly organized and disciplined group of approximately 500 professionals. Membership of the launch team reflects the complexity involved in preparing for and conducting a human space launch. Civil service and contractor personnel from Kennedy occupy central roles, but other NASA centers, contractor personnel and agencies also contribute.


The Shuttle launch team is organized into three groups, according to major functional responsibility. All three groups report to the Shuttle Launch Director, who has overall technical and safety responsibility for the countdown.

1. The prime launch team is responsible for test, checkout and monitoring of the flight hardware and ground support equipment to ensure that all system parameters meet the criteria to commit the vehicle to launch. This team includes the group stationed in the prime firing room in the Launch Control Center, as well as offsite personnel with critical launch support responsibilities. The prime launch team is headed by the NASA Test Director (NTD), who reports to the Shuttle Launch Director.

Approximately 200 of the 300 members of this team are stationed in the prime firing room for the mission at hand. The NTD and other managers overseeing the countdown process are stationed at consoles facing into the firing room. Reporting to the NTD are 11 test conductors, each responsible for a specific subset of requirements to be met prior to launch.

For example, the Orbiter Test Conductor (OTC) is the individual in charge of the system-level engineers monitoring the hardware and software on board the orbiter itself. Other test conductors are responsible for the external tank and solid rocket boosters, the payloads, support operations, landing operations, safety, communications and other functions.

Also stationed in the prime firing room is the Shuttle Project Engineer, who is the lead engineer and reviews all technical issues for the NTD.

The astronaut assigned to command the Shuttle mission represents his flight crew as he communicates with the NTD from inside the vehicle at the pad.

Seated at seven console sets facing the windows of the prime firing room and looking toward the two launch pads are the teams of system-level experts who report to the test conductors. They represent all orbiter, external tank and solid rocket booster components. Mission-specific payload experts are assigned to this team also.

Also part of this configuration is an eighth console called the integration console, which includes the Ground Launch Sequencer that automatically controls the final nine minutes of the countdown.

At the rear of the room is the Master Console, which monitors the Launch Processing System computer network with which all Shuttle processing, checkout and launch are performed.

Each console is arranged in its own semicircle and includes up to a dozen individual operator stations. The number of stations dedicated to a major function, such as payloads, varies. Besides the software giving the operator control over a particular system, each console has radio hookups and video displays monitoring Shuttle and pad hardware. Click here for photo of a typical console.

A console chief is assigned to each console. This typically is a senior system engineer. One of the console chief's functions is to communicate with personnel in an adjacent backup firing room so the expertise of both rooms is combined.

The system engineers at the seven console sets have their own method of assigning the various responsibilities that encompass their particular set of requirements. For example, the lead engineer for the liquid hydrogen system has approximately eight engineers reporting to him or her, each of whom are responsible for a portion of the entire system. This includes the storage tank at the pad, pressurization systems, the cross-country pipelines used to load the external tank, the hydrogen portion of the tank itself, and so on. In turn, each of these elements has its own set of responsibilities and requirements to monitor.

Seated behind the console operators are additional engineers and technicians. They are available to provide technical expertise or to help troubleshoot any glitches that may occur during the countdown.

Approximately 100 members of the primary launch team are located outside the confines of the Launch Control Center, yet oversee systems and hardware critical to the launch process. These include representatives from Johnson Space Center, which manages the Space Shuttle program and is responsible for on-orbit operations. U.S. and overseas contingency landing site readiness is the JSC team's job also. The Eastern Range, managed by the U.S. Air Force, is responsible for ensuring range safety as well as providing weather information. Located nearby is the Merritt Island Launch Area (MILA) Station, which provides voice and data transmission paths to and from the vehicle. Goddard Space Flight Center manages the MILA station.

2. The engineering support team has a similar composition and organization to that of the launch team, but is not directly responsible for system management. Acting in more of an oversight capacity, they provide technical support should problems arise. This extra set of eyes is composed of extremely experienced engineers who can assist in solving problems in real time. These engineers are stationed primarily in the backup firing room, Firing Room 2, located between Firing Rooms 1 and 3 on the LCC third floor. They work at computer hardware and software similar to that of the prime team, but perform systems-monitoring only, with no command capability or responsibility.

Because of space limitations, an additional room on the third floor also is used, called the Engineering Support Area (ESA). The engineering support team also includes personnel outside KSC, such as other centers and contractor facilities. All represent a pool of expertise from which the prime team can draw at a moment's notice if need be.

3. The senior government and contractor managers that comprise the Mission Management Team (MMT) are charged with reporting any issues that may affect the safety or success of the countdown or mission. Reportable issues can originate during any phase of the preflight hardware component processing as well as during the countdown itself. All issues raised must be resolved prior to clearing the launch vehicle for flight. During the countdown, the MMT is located in the Operations Support Room area of the prime firing room.


The launch of the Space Shuttle marks the finale of many thousands of individual tasks performed by highly trained and motivated workers at the Kennedy Space Center and elsewhere. Approximately four months of system tests, refurbishment and unique configurations for the upcoming mission are required to prepare the Shuttle for its next flight.

The countdown formally begins with the call to stations, issued by the NTD from the Launch Control Center. The countdown clock begins ticking at T-43 hours about three days before liftoff. With built-in hold time included, it takes roughly 72 hours to conduct a Shuttle launch countdown.

The reference tool for conducting a Shuttle launch countdown is a five-volume manual encompassing some 5,000 pages of instructions. More commonly known by its identification number, S0007, the Shuttle countdown manual is the lengthiest Operations and Maintenance Instructions (OMIs) used at KSC to document procedures for assembly, processing, testing and launching of the Shuttle. S0007 is reviewed and updated prior to each mission.

The first volume of S0007 contains all the preparations necessary to lead up to the beginning of the three-day countdown. Volume 2 is the actual set of countdown instructions that logically and sequentially configure the vehicle for launch. It is this integrated set of instructions that contains all the requirements necessary to launch.

Volume 3 contains all the instructions to follow in the event a launch is scrubbed. In this case, the vehicle and facilities are recycled for a subsequent launch attempt. This next attempt could be in as little as 24 hours or could be several days later. Volume 4 contains all the specific individual system instructions that are initiated from Volume 2. Volume 5 is a set of preplanned contingency procedures and emergency instructions available in the unlikely event they are required.

This entire set of instructions is performed under the direction of the NTD.

The beginning of a countdown is not unlike a routine power-up of the orbiter. System checks are conducted and the vehicle configured for later operations. Once preparations get under way to load the orbiter's fuel cell power reaction and storage distribution system at around T-28 hours, the spaceship's configuration is getting more oriented toward flight. The remaining countdown milestones focus on pad and vehicle closeouts: closure of the payload bay doors; retraction of the Rotating Service Structure at the launch pad; installation of the crew escape pole; activation of the onboard fuel cells; loading of the external tank, and boarding of the flight crew.

After the countdown clock starts ticking, the prime firing room is staffed around the clock. Personnel are typically selected for this prime launch team at about the time an orbiter is being transferred from the Orbiter Processing Facility to the Vehicle Assembly Building for integration with the other Shuttle flight elements.

As subsequent countdown milestones are met, the composition of the prime firing room team will change. Assigned shifts of teams will report on station at varying times, depending on which system they oversee. For example, a loading crew comes on station at T-9 hours to begin preparing for cryogenic loading of the Shuttle external tank at the T-6 hour mark. Once its task is completed by the T-3 hour mark, this group of individuals will be succeeded by a fresh crew to carry on through launch.

Another example of a specialized countdown crew are the personnel who oversee the ground launch sequencer (GLS). GLS operators may be on hand earlier in the countdown, but they do not have a formal role until the day of launch. The GLS crew -- a primary operator, two backups and a fourth to retrieve data -- are on station by the T-2 hour mark to call up the GLS software and prepare for the final count. At T-20 minutes, the GLS will begin issuing active commands, and at T-9 minutes, it assumes automatic control of the count.

As they work through S0007, the launch team members at the consoles in the prime firing room are monitoring vehicle and support system performance according to acceptable measurements and parameters. The full set of measurements that must be checked totals about 25,000. About two thirds of these originate from the flight vehicle and one third from the ground support equipment and facilities. Measurements generally fall into one of two categories, Launch Commit Criteria or supporting data.

Launch Commit Criteria are those parameters that have safety-related or mission success implications; they define what constitutes a vehicle that is ready to fly as well as the conditions under which it is permissible to launch. Launch Commit Criteria is implemented at T-6 hours (prior to ET load). There are Launch Commit Criteria that guard against flight hardware damage and those designed specifically for astronaut safety. For instance, there is a permissible concentration of gaseous hydrogen within the orbiter's aft fuselage that deals with astronaut safety and a slightly different permissible concentration that may affect shuttle hardware issues. Even the weather must meet specific Launch Commit Criteria requirements in order for a liftoff to proceed.

The other set of data represents supporting information available for the engineers to help maintain a specific hardware configuration or to aid in troubleshooting problems. An example would be the temperature limits for the hydrogen vent line that is used to safely transport the gaseous hydrogen from the external tank to its flarestack at the pad for disposal by burning.

This vast data base on system performance is part of the Launch Processing System and is available for the engineers to access at any point in the launch countdown. About 2,300 Launch Commit Criteria measurements are monitored. As the countdown progresses toward liftoff, all attention focuses on the Launch Commit Criteria. All the parameters must be met prior to passing a "Go" for launch.


Communication in the prime firing room is carefully routed through the Operational Intercommunications System (OIS). It is a closed-loop digital voice system utilizing fiber optic cable. During countdown, the NTD uses one frequency as the command channel for overall countdown integration. The Test Conductors use separate channels to individually lead their specific subset of the countdown. The Test Conductors and the NASA Test Director communicate with each other on an as-needed basis on issues such as status checks, safety and command responses. The use of different channels separates communication traffic and keeps it at a manageable level.

Acronyms are used liberally by the entire team to keep verbiage to a minimum. All Firing Room console positions are assigned unique 'call signs' that are used by the team for quick and positive identification of who is talking. The protocol has the initiator of the dialogue calling the person he wishes to talk to followed by his own call sign. This allows the person called to know who is calling. For instance,

"OTC, NTD, Begin crew module closeout" means

the NTD is directing the OTC to begin preparing the crew module for closing the hatch and launch. Other acronyms are used for system descriptions such as PRSD for the Power Reactant Storage and Distribution System which is the liquid oxygen and liquid hydrogen fuels that power the orbiter's on-board fuel cells that create electric power. When the flight crew enters the orbiter, the astronauts will hook up to the same communication channel as the OTC. At the T-20 minute mark, the NTD switches over to this channel and it now becomes the Command channel. The integration console in the prime and backup firing rooms maintain communication channels with the other centers, such as the Mission Evaluation Room at Johnson Space Center in Houston, and the Huntsville Operations Support Center at the Marshall Space Flight Center in Alabama. The Mission Evaluation Room plans and implements flight data retrieval, processing, exchange analysis, evaluation and reporting, and post-mission evaluation. The Huntsville center provides technical support on the Shuttle main engines, external tank and solid rocket boosters.

Hookups also are established with the contractors' home offices. Orbiter manufacturer Rockwell International maintains a support room at its Downey, Calif., plant that remains open around the clock throughout a Shuttle mission.


A special type of discipline is exercised in the prime firing room, commensurate with its importance. Launch team members undergo training in the rules and regulations governing their conduct. These include limiting conversation to the business at hand, no personal telephone calls except in emergency, and no reading of non-work related materials. During time-critical operations, personnel remain at their assigned stations.

From T-3 hours on, entrance into the prime firing room is restricted. Only personnel with firing room badges are allowed in and movement is minimized. A prime firing room badge is issued only to personnel having a direct console position related to the terminal portion of the count. At T-20 minutes, the door to the prime firing room is locked. The intent is to eliminate distractions and allow the team to focus its attention on the countdown.


While countdown activities are controlled from the LCC prime firing room, personnel at the pad perform different tasks required for launch preparations. From T-11 hours to T-6 hours, a great deal of final preparation work occurs at the pad: rollback of the Rotating Service Structure; installation of time-critical flight crew equipment; performance of the pre-ingress switch list; sampling of crew seat oxygen; and installation of the crew escape pole in the orbiter. Overseeing these activities and keeping the NTD informed of their progress is the pad leader.

After the External Tank is loaded, only critical and highly specialized teams will travel to the pad again before liftoff. One of these is the Final Inspection Team, also referred to as the ice team, which conducts a preflight walkdown of the vehicle and pad during the two-hour hold at T-3 hours. Another ice team is stationed in the backup firing room. Its job is to monitor the external tank's insulation and attachment struts for excessive ice formation before, during and after loading of the supercold liquid hydrogen and liquid oxygen. Click here for a picture of the ice team on the Mobile Launch Platform.

Another specialized team is the white room closeout crew, which also proceeds to the pad during the two-hour-hold at the T-3 hour mark. Their task is to insure that the orbiter cockpit is properly configured for flight and to assist the astronauts with entry into the orbiter. They also ensure the side hatch is properly closed and that the white room is configured for launch.

Handling of any anomaly at the pad that should occur during or after external tank loading is the responsibility of a red crew. This is not a pre-existing unit, but a team assembled from a pool of specially trained workers with experience in the particular problem area. Members have been specially trained in fire and rescue techniques and must have undergone special certification. Their activity at the pad would be conducted by the system engineer responsible for the anomalous system and under the strict direction of the NASA Test Director..


Beginning approximately 15 minutes before launch, readiness polls are conducted by the three teams that together comprise the Shuttle Launch Team. The NTD verifies that the prime launch team is reporting no violation of the Launch Commit Criteria. The Engineering Director who heads up the Engineering Support Team verifies no constraints to continuing with the final count. And the Mission Management Team Chairman verifies that there are no open issues with any of the senior element managers.

These three verifications are passed on to the Shuttle Launch Director, who conducts a KSC management poll. Assuming all responsible personnel are in agreement, the Launch Director gives his permission to proceed with the countdown to the NTD. The NTD in turn sets in motion the final nine minutes of the countdown, automatically controlled by the Ground Launch Sequencer.

Once the Shuttle's twin solid rocket boosters ignite at T-0, responsibility for the mission switches from KSC to the Mission Control Center at Johnson Space Center in Houston. KSC once again assumes responsibility after the orbiter has landed and the flight crew has exited the vehicle.

Countdown Home Page

Last Updated Thursday June 08 14:23:42 EDT 1995
NASA KSC - Public Affairs Office