When a space shuttle shuts down in the last seconds before liftoff, the launch team has its most important work to do.
- By Gregory Freiherr
- Air & Space magazine, January 1996
(Page 2 of 5)
Sofge's football metaphor is apt. The law of the firing room is concentration; its most frequent activity is drill. Although the room's windows provide a view of the launch pad, the launch team members rarely see a shuttle liftoff. They read its status in the numbers on their computer screens.
The firing room looks a lot like mission control, its sister control room in Houston, which takes over from Florida as soon as the shuttle's solid rocket boosters ignite. Banks of gray metal consoles with computer screens fill the basketball court-size room. On each bank of consoles there is a cryptic nameplate: HAZ GAS (hazardous gases), LOX SYS (liquid oxygen system), MPS/SSME (main propulsion systems/space shuttle main engines). About 200 engineers sit at the consoles, immersed in the illusion of a shuttle countdown. The training goal is to make the monitors look exactly as they would if a real launch were under way. The engineers report to the NASA Test Director (NTD) and the Orbiter Test Conductor (OTC), who communicate with the flight crew on the shuttle.
"The last command we give the astronaut flight crew is at two minutes and 30 seconds," says Bartolini. At that point the shuttle begins running solely on internal power, and the OTC tells the astronauts to close and lock their visors and initiate oxygen flow. "He usually gives them a little send-off, and then it gets real quiet. The only talking that's being done is by the ground launch sequencer engineer calling out the different milestones as we go on down and the NTD, who starts calling at one minute, then 45 seconds... on down. Other than that the firing room is extremely quiet. Everybody is looking at their data hoping that they don't get an anomaly."
In today's simulation, everyone gets plenty of anomalies. Data systems engineer Robert Pierce and two math modeling colleagues have loaded the computers with a variety of virtual emergencies. "We're really taking a polished team and putting a high gloss on it," Pierce says. "We plan for things that have a
likely occurrence of happening. 'Likely' for us space nuts is less than one percent. We don't like surprises."
Many of the problems Pierce and his gremlins throw at the launch team occur during a pad abort. After the orbiter's computers command a main engine cutoff, they grind through the procedures for safing the vehicle: starting a spray of water to disperse unburned hydrogen exhausted from the main engines, for example, sealing the hydrogen and oxygen valves to the engines, disarming the explosive bolts on the solid rockets. Progress is reflected on computer screens filled with blue, green, yellow, and--to show exceeded limits or other trouble--red or flashing numbers. The red numbers require engineers to respond according to well-documented procedures.
In one simulated emergency, engineers begin to see temperatures in red because the shuttle's ground cooling unit fails. "You don't want to cook your equipment," Pierce explains. The NTD issues an order to activate backup systems, then another to shut down a series of electronic systems on the shuttle that produce heat. An engineer at the environmental control console manually flips a switch to turn on a chilled-water heat exchanger. Others activate radiators on the inside of the payload bay doors. At another environmental control console, a team lowers the temperature of air being pumped into the payload bay by a purge system.
Next, the NTD orders staff at the LOX and liquid hydrogen consoles to prepare to drain the external tank, a precaution in case power to the shuttle must be turned off. The next step is to reestablish power from the ground in order to shut down the onboard fuel cells, which are major heat generators.