Outline of Material Covered During our Meeting February 2, 2001

A. ET (External Tank)

1. The ET actually contains two smaller tanks

a) LOX Tank—Liquid Oxygen (oxidizer)

b) LH2 Tank—Liquid Hydrogen (fuel)

2. LOX and LH2 supply the propellant for the three SSMEs.

a) LOX and LH2 are pumped through two very thick lines to the SSMEs.

NOTE: The pumps that force LOX and LH2 from the ET to the SSMEs work fast enough to pump all of the water out of an Olympic size swimming pool in just seconds.

b) SSMEs are ignited at T-minus 6 seconds.

c) SSMEs are liquid fuel rocket engines

(1) Advantages of SSMEs

(a) Because they are liquid fuel, their thrust can be easily increased or decreased by adjusting the main engine valves.

(b) They can be shut down if necessary.

NOTE: The ability to increase or decrease the amount of fuel flowing into an engine is called “throttle.” An event called the “Throttle Bucket” takes place about 40 seconds after liftoff. At that time, the Shuttle is going so fast that the air is pressing too hard on the surfaces (wings, tail, etc.). To keep it from ripping apart, the SSMEs are throttled back to about 65% of their power. After the Shuttle’s altitude climbs, the Earth’s air is thinner so the pressure on its surfaces is not as high. At that time the Shuttle can be throttled back up to 104%. This period of time when the pressure on the Shuttle is great enough to cause damage is called Max Q.

II. Communication “Comm” Loops of Russell Space Center (RSC)

A. MCC Loop (Mission Control Loop)—used for Flight Controllers to communicate with each other during a mission.

1. All Flight Controllers can hear and speak on the MCC Loop

2. The Astronaut Crew cannot hear the MCC Loop, but everything that they say on the Air-to-Ground Loop can be heard on the MCC Loop

3. All communication on the MCC Loop goes through Flight

4. The Flight Controllers use Call Signs to identify each other. For example, the Flight Surgeon is simply called “Surgeon.”

B. Air-to-Ground Loop (AGL)—used to communicate between the Astronaut Crew and Mission Control.

1. Only the CapCom talks directly with the Astronaut Crew on the AGL

C. Spaceflight Meteorology Group Loop (SMG Loop)—used to communicate between Mission Control and the Spaceflight Meteorology Group

1. GNC communicates directly on the SMG Loop and relays the information to Flight.