Outline of Material Covered During the Past Several Meetings

NOTE: A small portion of these notes has NOT been discussed yet. Read and study all of the material to help prepare for the discussion later this week.

I. Newton’s Laws of Motion

A. About 400 years ago Sir Isaac Newton came up with three ideas or “laws” about how things move. His ideas, or Laws of Motion, are still used by scientists in designing all types of spacecraft.

1. Newton’s First Law of Motion—An object in motion tends to stay in motion in a straight line unless acted upon by an external force. An object at rest tends to stay at rest unless acted upon by an external force.

a) This simply means that once something starts moving, it will continue to move in a straight line until some force, like gravity or friction, effects it. It also means that when something is not moving (at rest) it will not move unless some force, like a rocket engine, makes it move.

2. Newton’s Second Law of Motion—An object’s change in speed or direction is proportional to force and mass.

a) In simple terms, a large object needs to be pushed harder than a smaller object to be moved faster or slowed down.

3. Newton’s Third Law of Motion—For every action there is an equal and opposite reaction.

a) Think of a balloon that is inflated and then released. The air flows out one direction while the ballon is thrust in the opposite direction.

NOTE: For easy reference, we usually refer to these laws as Newt 1, Newt 2, and Newt 3.

II. Space Shuttle Communications

A. Ground Tracking Stations (GTS)

1. Path of the radio signal between the Orbiter and MCC goes like this: Orbiter + GTS + MCC

2. GTS were the only means of communication between the Orbiter and Mission Control until the mid 1980’s

3. Disadvantages of the GTS

a) A GTS can only communicate when the Orbiter is overhead.

b) Because ¾ of the Earth is covered with water, the Orbiter was NOT within range of any GTS most of the time. In fact, about 85% of the time, the Orbiter was in LOS.

(1) This was a potentially dangerous situation. If something were to go wrong, the MCC would only have telemetry or communication with the crew for very short periods of time.

c) They were expensive to operate and maintain because there were so many of them.

4. In the mid-1980s the GTS system began to be replaced by Tracking Data and Relay Satellite System (TDRSS)

B. Tracking Data and Relay Satellite System (TDRSS)

1. Path of the radio signal between TDRSS and the Orbiter goes like this: Orbiter + TDRS Satellite + Ground Terminal + MCC

2. TDRS Satellites are in Geostationary Earth Orbit (GEO) about 22,000 miles altitude. This means that they are high enough to orbit at the same speed that the Earth rotates. This way they are always over the same spot on Earth 24-hours a day.

3. TDRSS uses just two satellites to send information back and forth between the Orbiter and MCC

a) Tracking Data and Relay West (TDRW) is “parked” in orbit above the Western Hemisphere over the Pacific Ocean.

b) Tracking Data and Relay East (TDRE) is parked over the Eastern Hemisphere near the west coast of Africa.

c) Both TDRW and TDRE have a back up satellite in a nearby orbit that can be activated if either one malfunctions.

4. The Orbiter must be within Line Of Sight of the TDRS Satellite to communicate with it.

a) Line Of Sight means that there is a clear straight path with nothing blocking the signal.

5. Ground Terminal

a) All communication between the Orbiter and MCC is relayed through the Ground Terminal

b) Located at White Sands Complex (WSC), New Mexico

c) There are two Ground Terminals located at WSC. One is the primary terminal that is normally used. The other is the backup in case the first one fails.

d) The TDRS Satellites must be within Line Of Sight of WSC to be able to transmit or receive signals.

6. Zone of Exclusion (ZOE)

a) The ZOE is an area over the country of India that is not within Line of Sight of either TDRE or TDRW. When the Orbiter passes through the ZOE it experiences and LOS that lasts about 5 – 7 minutes.

b) It is the responsibility of the GNC to advise the Flight Director and Crew 5 minutes and 1 minute before the Orbiter enters the ZOE.

c) Communicating in the ZOE

(1) GTS Diego Garcia sits on an island in the middle of the Indian Ocean in the ZOE. GTS Diego Garcia can be activated so that the Orbiter can communicate with MCC while in the ZOE. This is only done if something critical is going to take place during the time that the Orbiter is in the ZOE.

(2) Tracking Data Relay Zone (TDRZ) is a normally deactivated (shutdown) TDRS that orbits near the ZOE. If the Guam Remote Ground Terminal (GRGT) on the island of Guam is activated along with TDRZ, then the Orbiter can still send and receive signals with MCC while in the ZOE.

III. Telemetry

A. Telemetry is the information that is transmitted to MCC and then read on the Flight Controllers’ screens.

1. Telemetry is sent from the Orbiter > TDRS Sats > Ground Terminal WSC > MCC

B. Monitoring Telemetry

1. It is the responsibility of the Flight Controllers to monitor the telemetry

2. Telemetry values are recorded approximately every 15 minutes.

a) “Telemetry values” means the number that is on a telemetry screen at any moment. For example, the telemetry value of a LOX Tnk 1 Temp with a reading of -216 deg is “-216 deg”

b) We call these 15-minute periods our Telemetry Tracker Inputs.

c) The STS-2 Space Team created the jargon phrase “TeleTracker Inputs” to shorten this a bit.

3. Interpreting Telemetry Data—“Interpreting” simply means figuring out what is going on onboard the Orbiter by looking at the telemetry that is being sent to MCC.

a) Fluctuating Data—Telemetry Values are updated on your screen every 3 seconds and most will go up and down a little bit each time. This up and down movement is quite normal, and it is called fluctuation.

(1) Thresholds—Fluctuating data is usually safe as long as it stays within the Upper and Lower Threshold.

(a) For example, suppose the Upper Threshold for Cbn Pres is 15.5 psi and the Lower Threshold is 14.0 psi.

(b) If the current telemetry value for the Cbn Pres is 14.5 psi then that is a nominal value.

(c) If it drops to 14.2 psi it is still nominal. If it drops to 13.8 psi then that is an off-nominal value and we would say that it is red-lining.

(d) Of course, if the Cbn Pres climbed to 15.9 psi that would also be a red-lining value since it is above the Upper Threshold.

b) Linear Data—Starts at a certain value and then normally continues to either climb or fall throughout the mission. Linear data does not fluctuate--it either climbs or falls.

(1) An example, of linear data would be a LOX tank that is used to provide breathing oxygen for the crew. It would start out full and as the crew continued to breathe during the mission, the tank would slowly empty. Since the amount of oxygen in the tank drops, the telemetry value for that tank would also normally drop during the mission (They don’t breathe INTO the tank do they?)

c) Binary Data—Binary data is usually a simple red or green light indicating that something is working normally or that it is malfunctioning.

Notes on Ratty Data—Occasionally telemetry will appear on your screen that is obviously not correct. This is called Ratty Data.

1. An example of ratty data might be a LOX Tnk Pres that goes from 212 psi to 3587698 psi or even gibberish like $##**@(( psi. This is obviously not correct.

2. Some causes of ratty data

a) Computer error

b) Interference with the signals being sent from the Orbiter

c) LOS

d) Sensor malfunction. Sensors are devices that measure temperatures, pressures, etc.

IV. Systems Status Check (“Status” simply means “how something is doing”.

A. A Systems Status Check is usually done after a major event like liftoff or EI.

B. During a Systems Status Check the Flight Controllers take a detailed look at all of their telemetry to make sure that everything is nominal.

C. After the Flight Controllers review their telemetry, Flight calls each console for a report.

V. Polling

A. Polling is done before most major mission events like launch, opening the PBD, or before an OMS burn.

B. During a poll Flight calls each station to get a GO/NO GO. Each Flight Controller gives their approval with a GO, NO GO, NO CONSTAINTS, etc.

C. After the poll, Flight gives the GO to proceed with the event and CapCom relays that information to the crew.

VI. Multiple Redundant Systems

A. Multiple Redundant Systems is a long fancy word for a very simple idea. Read on!

1. The Space Shuttle travels in the dangerous remote vacuum of space where replacement parts cannot simply be bought or installed. Everything it needs must be carried with it.

2. Since it is almost impossible to replace broken parts or systems while in space, the Space Shuttle is designed with several parts that all do the same thing. That way if one breaks down, the others can still do the job.

3. Examples of Multiple Redundant Systems onboard the Shuttle are listed below. The number next to each one tells how many there are on the Shuttle. Remember, they all do the same thing, but only one is actually needed to do the job for the entire Shuttle.

a) APU—3

b) HPU—3

c) Fuel Cells-3

d) GPC-5 (Four run on the same program. The other one runs on a different program)

NOTE: “Redundant” means doing something over and over again