Shuttle System

Ken Fore

Swing Arm Engineer

Which console do you man in the Firing Room?

C7

What system(s) do you monitor and control from that console?

Our team monitors two swing arms, the Orbiter Access Arm and the Gaseous Oxygen Vent Arm. We are responsible for a third swing arm, the Hydrogen Vent Line Access Arm. However, we can't monitor that arm from a console; we have to manually verify that it works correctly. We also monitor the Sound Suppression System and the Emergency Egress Fire Detection System.

How are those systems used by the Space Shuttle?

Swing arms are retractable mechanical systems that reach out from the launch tower to the Space Shuttle. They are used to service the Shuttle when it’s at the launch pad.

Technicians, engineers, and astronauts use the Orbiter Access Arm to access the Space Shuttle crew module. An environmentally controlled "white room" at the end of this arm provides a safe and protected area to transfer astronauts and their equipment to the orbiter before launch.

The Gaseous Oxygen Vent Arm is positioned over the External Tank (ET) nose cone during Shuttle fueling operations. At the end of this arm is a hood, nicknamed the Beanie Cap. This hood uses heated gaseous nitrogen to remove the extremely cold gaseous oxygen that vents out of the ET. This prevents vapor that forms at that vent from condensing into ice which could fall and damage tile or other critical Shuttle surfaces.

The Hydrogen Vent Line Access Arm is used to mate the External Tank (ET) Ground Umbilical Carrier Plate (GUCP) to the launch pad hydrogen vent line. The GUCP provides support for plumbing and cables, called umbilicals that transfer fluids, gases, and electrical signals between two pieces of equipment.

During Shuttle fueling operations, hazardous hydrogen gas is vented from a fuel tank inside the ET. This gas travels through the GUCP and vent line over to a flare stack located a safe distance from the Shuttle. The flare stack is a tall pipe with a flame igniter at top that safely burns away the hydrogen gas.

The Hydrogen Vent Line Access Arm also provides contingency access to the ET. It is retracted several hours before launch, leaving the umbilical attached. When the solid rocket boosters ignite, the umbilical carrier plate releases from the ET and falls back against the tower. A curtain of sprayed water protects it from flames produced by the Shuttle engines during launch.

The Sound Suppression System protects the Shuttle and pad structure from acoustical and heat damage during launches. Right before the engines ignite, 382,000 gallons of water are delivered to a distribution system. Just prior to launch and at liftoff, a series of valves are opened to supply water to the Space Shuttle Main Engine (SSME) and Solid Rocket Booster (SRB) flame holes. This prevents sound shock waves generated by the engines from damaging critical control surfaces on the Orbiter. It also protects the Shuttle from overpressurization when the SRBs ignite.

The Emergency Egress (EE) Fire Detection System is a collection of flame and heat detectors on the Shuttle launch access structure. This system helps personnel in the Firing Room detect and locate fires if an emergency evacuation occurs during the launch countdown.

What are your responsibilities with regard to those systems?

After the Space Shuttle has been moved to the launch pad, NASA and contractor Swing Arm engineers, with the assistance of pad technicians, power up the high pressure pneumatic and hydraulic extend/retract system. This system extends the Orbiter Access Arm (OAA) and Gaseous Oxygen (GOX) Vent Arm.

When the OAA is fully extended, the white room dock seals are inflated to provide a weather tight seal on the opening to the crew module. The OAA usually remains in this position until late in the launch countdown. The GOX Vent Arm is initially extended to do an alignment verification with the External Tank. At a later date, it is re-extended to prevent ice formation during the launch countdown.

The OAA is considered a launch critical system. It is retracted away from the Orbiter at 7.5 minutes before launch. In the event of an emergency or launch abort, it must be extended back out within 30 seconds to provide an escape path for the astronauts and allow rescue personnel to reach them.

The GOX Vent Arm, Sound Suppression System, and Emergency Egress Fire Detection System are launch critical as well. They have Launch Commit Criteria (LCC) associated with them that can result in a launch hold or scrub if not met.

During launch countdown, contractor and NASA engineers use consoles to activate and monitor the OAA and GOX Vent Arm high pressure extend/retract system. They also activate and monitor the GOX Vent Arm heated purge system to ensure that ice doesn't form at the ET nose cone.

Engineers keep on eye on all system functions including pneumatic/hydraulic pressures, electrical power availability, purge temperatures, fluid levels, limit switch, and position indicators. Our engineering responsibility is to monitor this data to make sure that our systems are ready to support launch. We also help resolve any problems that might occur.

If problems are encountered, discussions are initiated with launch countdown managers. These discussions continue until either the problem is resolved or a countdown hold is announced to allow more time to fix the problem. There is a lot of redundancy designed into these systems. Engineers can issue commands from consoles to open/close valves, increase/decrease temperatures, and switch systems from primary to backup. This gives the launch team greater flexibility to make decisions and take responsibility for the hardware under their control during the launch countdown.

What was your most exciting or memorable experience while working in the Firing Room?

One of the most memorable experiences was a problem that occurred on the Orbiter Access Arm during STS-113. The OAA retract system is powered up and monitored for about two days before launch. This normally gives the engineering team enough time to recognize trends in the data displayed on the console. However, data that indicated a problem with the arm's hydraulic retract system was initially overshadowed by another known problem that had been deemed acceptable for launch.

The pressure and hydraulic fluid level data continued to indicate something wasn't normal, even considering the known problem. One member of our engineering team recognized that we probably had a second problem. Upon further investigation, the likely cause was determined to be a positioning error in one or two manually operated valves at the launch pad. Because these valves can't be operated remotely and the Shuttle was already loaded with fuel, a hazardous operations team, called the Red Crew, was sent out to the pad to reposition the valves.

What makes this so memorable is the great teamwork exhibited by all of the groups who help resolved this problem. If our team had not recognized it, the Orbiter Access Arm would not have retracted just prior to launch, resulting in a launch scrub.