Friday, September 25, 2009

Your typical Space Shuttle Mission Part 3: Getting to space (AKA Countdown, Launch, Ascent and Orbit Insertion)

After reading all I wrote, now you know how a space shuttle roughly works, and all the people involved. A quick note, a shuttle crew, the astronauts, are usually a minimum of 2: The Commander (CDR on the radio) and the Pilot (PLT). If a mission requires extra hands, Mission Specialists are also included in the crew (MS1, MS2, and so forth). Up to now, the maximum number of crewmembers to ever have flown on the space shuttle is 7 (The CDR, The PLT, MS1, MS2, MS3, MS4 and MS5). The commander pilots the shuttle and speaks for the entire crew, while the pilot assists in piloting. To understand this, in normal flying, the CDR is the pilot, and the PLT is the co-pilot.

On to actual launch procedures!!!

top.discovery.launchpad.ap

COUNTDOWN

3 days before actual launch. Shuttle Discovery is in the pad, covered by the rotating service structure, protecting it from the weather. Countdown-wise, at T-43 hours (yet, 3 days before… remember, the holds), the countdown clock is started, and everyone is called to their stations. The Shuttle Test Team, the Launch team and the Mission Management Team start to work 24/7 to make sure the shuttle and crew are ready to launch, and that the systems and weather conditions allow for it, beggining with final checkouts to the shuttle and launchpad, and software loading into the shuttle’s computers.

The first built-in hold is at T-27 hours, and lasts 4 hours. During this hold, the pad is cleared of all non-essential personnel and the shuttle’s power reactant storage and distribution system is filled with cryogenic (read: uber cold) propellants. When the hold releases and it counts down again, the fuel cells’ storage tanks are filled with said cryogenic propellants.

The countdown holds again at T-19 hours, another 4-hour hold, unless the distribution system needs time to do an offload. They cut off the umbilical to the orbiter, clean and vacuum the crew cabin, and some other tasks.

The hold releases from T-19 hours. Now the 3 Main Engines are prepared for the fuel tanking and actual flight, the closing out of the orbiter and launchpad continues, and the Sound Suppression System tank is filled with water.

(A side-note: The SSS (sound suppress system) is composed of a 300,000 gallon water tank several meters away from the launchpad. This tank is connected via tubes and pumps to the launcher platform, which has several jets of water, some of them for quick-flooding the space below the launcher platform, and some that suppress fire from the launch as soon as the vehicle clears. The REAL purpose is flooding the compartments below the launcher platform, so the sound shockwave generated by the engines and boosters is dampened by the water, and doesn’t harm the orbiter on the rebound. The entire system, on peak maximum pumping, shoots a whooping 900,000 gallons of water per minute (meaning it’ll be over in less than half a minute, considering there’s only 300,000 gallons). This is the sudden rush of water you see flowing from below the platform at 16 seconds prior to liftoff. Watch a Youtube video of a launch to see what I mean)

The hold once again hold at T-11 hours. This is the LOOOOOOOOOONGEST hold, lasting 13 or 14 hours. This is where the rotating service structure opens up to reveal the shuttle, and sets itself on the ready launch park position, as pictured below.

space-shuttle-discovery-launch-pad

Now, weather and engineering briefings occur during this hold, and the pad and surrounding area is checked for debris. The late flight crew equipment is stowed at this point, the IMUs (inertial measurement units, for the shuttle’s position) and the communication systems are activated, and the shuttle’s switches are put in the correct initial position for startup and launch.

Finally, the countdown resumes, and the orbiter’s fuel cells are finally activated. The blast area is cleared of all nonessential personnel for the duration of the count, and the orbiter purges its air to clean it.

We reach the T-6 hour hold, which lasts 2 hours, or one, if the launch was scrubbed and this is another next-day attempt. This is an important hold, where the Mission Management and Launch teams receive weather briefings. Launch team verifies that everything is ok for launch before ordering the External Tank fueling (called Tanking). Once everything is ok, the pad is cleared of all personnel, the go for tanking is given, and the fuel lines are chilled down to the temperatures of the liquid hydrogen and oxygen, and finally, tanking starts, where hydrogen and oxygen are pumped slowly, then quick. Usually, when tanking starts, the hold is released, and the countdown reaches T-3 hours, where another hold occurs.

At the T-3 hour hold, the tanking process finally reaches “Stable Replenish” mode. This is because a bit of the liquid hydrogen and oxygen will evaporate and escape the tank via exhaust lines. The fuel pumps keep pumping just a small stream of the liquids to replace whatever gets evaporated. All in all, the tanking is complete.

The IMUs are calibrated, and the Merritt Island Launch Area (MILA) tracking antennas are aligned. The final inspection team arrives at the pad and checks for possible ice damage (read: uber-cold liquid hydrogen and oxygen) and other issues. Finally, the Closeout Crew goes to the pad and prepares the orbiter for the astronauts’ entry (ingress).

The hold releases, and the astronauts depart to the launchpad, and they go up to the crew access arm and reach the “white room”, a small room at the end of the crew access arm that is put against the orbiter’s hatch. It has air conditioning for the comfort of the astronauts and closeout crew and it has a hose that blasts cool, clean air inside the orbiter. One by one, the astronauts are helped inside the orbiter, seated and harnessed into their seats. Once seated, they perform a basic voice check with both the NASA Test Director and Mission Control. All communications are in this format: the callsign of the one you’re calling, your callsign, and the situation, if any. This is an example of the commander’s voice check:

Mission Commander: “NTD, CDR, Comm check.”
NASA Test Director: “CDR, NTD, Loud and clear. Good afternoon!”
Mission Commander: “NTD, CDR, loud and clear. Glad to be here.”

After a brief pause, the commander checks communications with Mission Control, AKA “Houston”.

Mission Commander: “Houston, CDR, Comm check.”
Mission Control Center: “CDR, Houston, Loud and clear. Good day, and good luck.”
Mission Commander: “Houston, CDR, thanks!”

The Pilot, whose callsign is PLT, and the mission specialists, MS1, MS2, etc, also conduct their voicechecks. This is to ensure communications are possible to the ground, and that their mike lines are properly connected.

Once all astronauts are seated, the Closeout crew closes the orbiter hatch, latches and seals it for flight, and pressurizes the cabin, finally checking for leaks, before closing out the white room and leaving the pad. The astronauts perform several checks and configurations during this time.

Finally, we reach the second to last hold, at T-20 minutes, only lasting 10 minutes. The NTD makes a final launch team briefing during this hold, and the orbiter’s IMU alignment is complete.

The countdown timer resumes, and the crew is given the go to transition all GPCs to OPS 101, the terminal countdown phase of the OPS 1 (launch ops on the GPCs, remember?), and the cabin vent valves of the crew cabin are closed for flight.

And we finally reached the T-9 minute hold!! This hold typically lasts 45 minutes, but the time is adjusted to the launch window at this point (the precise moment when the shuttle must launch to reach a certain point in orbit by using the least amount of fuel possible, usually nowadays to catch up to the ISS). In this hold, the flight recorders (black boxes?) are activated. And the final flight readiness polls are done independently of all 3 teams. In the final 7 to 5 minutes of the hold, the official, final flight readiness poll is conducted as follows, assuming everything is ok for launch (transcript from STS-123 Endeavour launch poll, with names removed):

NTD: “Attention on the net, this is the NTD, conducting the Launch Status Check. All stations verify ready to resume count and go for launch. OTC?”
OTC: “OTC is Go.”
NTD: “TBC?”
TBC: “TBC is Go.”
NTD: “PTC?”
PTC: “PTC is Go.”
NTD: “LPS?”
LPS: “LPS Go.”
NTD: “Houston Flight?”
Houston: “Houston Flight is Go.”
NTD: “MILA?”
MILA: “MILA’s Go.”
NTD: “STM?”
STM: “STM is go.”
NTD: “Safety Console?”
Safety Console: “Safety is Go.”
NTD: “SPE?”
SPE: “SPE’s Go.”
NTD: “LRD?”
LRD: “LRD is Go.”
NTD: “SRO?”
SRO: “SRO is Go, you have a range clear to launch.”
NTD: “…and CDR?”
Mission Commander: “CDR is Go.”
(At this point, the Shuttle Test Team is Go, and will report to the Launch Director immediately confirming the CDR’s Go for launch. Launch will then poll his team.)
NTD: “Launch Director, NTD.”
Launch: “Launch Director.”
NTD: “Launch Team is ready to proceed.”
Launch: “Ok, I copy, thank you. Chief Processing Engineer, verify no constrains for launch.”
CPE: “No constrains, we’re ready.”
Launch: “Ok, thanks. KSC Safety Mission Assurance?”
KSMA: “KSC Safety Mission Assurance is ready to go.”
Launch: “Thank you. Payload Launch Manager?”
Payload: “The <insert whatever important cargo is hauled to space and the teams overseeing the operations> is ready to proceed.”
Launch: “Thank you. Range Weather?”
Weather Officer: “Weather has no constrains for launch.”
Launch: “Thank you. And OPS Manager?”
(The OPS Manager reports the readiness of the Mission Management Team)
OpsMan: “Ops Manager, Launch Director, the MMT is working no issues, you are go for launch.”
Launch: “Thank you, sir. Endeavour, Launch Director.”
Mission Commander aboard Endeavour: “Go ahead, Launch Director.”
Launch: <Insert praises to team, crew and weather, and gives the go for launch>
Mission Commander: <Thanks Launch Director, etc etc.>
Launch: “And NTD, you are clear to launch Endeavour.”
NTD: “Copy, clear to launch, thank you.”

And with this, the shuttle has been given the green light, the Go for Launch. The countdown usually resumes 2 to 4 minutes following the end of the Launch Status Check.

NTD: “Countdown will resume on my mark… 3…. 2…. 1… mark.”

T-9 minutes and counting.

This is the point where everything gets very dynamic, fast, and tense. Several things happen at the point of the hold releasing the 9-minute countdown. First of all, duh, the countdown timer starts to tick the final countdown to launch. Second, everyone is now checking their systems VERY CLOSELY for any problems. And third, and most importantly, all control of the countdown and all shuttle and pad systems have been transferred to the Ground Launch Sequencer Computer, or GLS. From T-9 minutes to T-31 seconds, the GLS can hold the countdown if requested by any launch controller or if it detects a problem. After that, only a cutoff and a launch scrub is possible, because the GLS gives control to the 5 GPCs aboard the orbiter.

At T-9 minutes, GLS Auto Sequence is initiated and it starts to check all systems, and perform several duties. The GLS console operator is monitoring and calling out anything the GLS reports to him.

T-7 minutes, 30 seconds. The tension rises.

“GLS is go for retract orbiter access arm.”

The crew access arm, complete with white room, slowly swings out of the way, leaving the astronauts truly confined to the orbiter. Within 30 seconds, the arm is out of the way.

T-6 minutes, 15 seconds. The pilot is given an instruction.

OTC: “PLT, OTC. Go for APU Pre-Start.”
PLT: “PLT, in work.” (a few seconds later after working on the corresponding switches on his panel) “APU Prestart complete.”

The countdown keeps rolling. Steadily it makes it to 5 minutes.

T-5 minutes.

GLS: “GLS is go for APU Start.”
OTC: “PLT, OTC. Start APU.”
PLT: “PLT in work.” (some seconds later) “APU Start complete.”

The Auxiliary power units are enabled. The shuttle’s aerosurfaces become active.

T-4 minutes, 55 seconds.

The GLS does two simultaneous checks. One is to check if the SRB’s ignition is armed and ready, and the other, which we hope never to use, is the SRB Range Safety System. This, in case the shuttle strays off course into a populated area while latched onto the SRBs, an army officer will have no choice but to activate the Range Safety System, which will detonate the SRBs and the External Tank, destroying everything, which of course results in the loss of the orbiter and the crew. Like they say, we’d rather lose 7 astronauts than hundreds or thousands of civilians.

The GLS also terminates the Liquid Oxygen Stable Replenish mode and shuts down the pump.

T-3 minutes, 55 seconds.

The GLS commands the shuttle to begin a series of programmed motions of its aerosurfaces to test them, and for warm hydraulic fluid to course through them.

T-3 minutes, 30 seconds.

With the aerosurface profile test done, the 3 main engines are gimballed (Moved around in place. The nozzles can be aimed if you didn’t know) in a preset motion pattern.

T-3:03. The gimbal check is complete, and the 3 engines are spread wide apart to avoid colliding with each other at ignition. The body flap under the engines is verified to be in launch position.

T-2:55. The GLS commands the External Tank to begin pressurization of the liquid oxygen. 5 seconds later, the cap on top of the ET, that removed whatever evaporated oxygen came out and drawed it out of the way, is removed, and moved out of the way of the shuttle.

T-2:35. The cryogenic reactant distribution system no longer fuels the fuel cells, and the fuel cells begin to take their reactants off their internal orbiter tanks to generate its own power.

T-2:00.

OTC: “OTC, crew. Close and Lock Visors.”

That means that the crew must close and lock their helmet visors for their suits to become pressurized, in the unlikely event of cabin depressurization.

T-1:57. Liquid hydrogen stable replenish terminated, all tank valves closed.

T-1:46. The External Tank begins Liquid Hydrogen pre-pressurization.

T-50 seconds. Ground power is cut from the shuttle, letting it use its internal power.

And this is the moment of truth. T-31 seconds.

“GLS is go for Auto-Sequence Start.”

From this point on, GLS arms the Cut-off command, the only command available from this point to T-0. It also initiates the Redundant Set Launch Sequencer, which will monitor that everything goes smoothly with the last 4 commands to be given by the shuttle’s computers, otherwise it’ll force a cut-off to the GLS. The countdown control is transferred to the shuttle’s computers as well, which continue the final countdown, the Auto-Sequence for launch.

T-28. The SRB APUs are started, which control the nozzles of the SRBs. 7 seconds later, the SRBs do a quick gimbal test.

atlantis-sss

T-16. The Sound Suppression System activates. A loud whistling is heard as 300,000 gallons of water are quickly pumped into the SRB and SSME’s trenches under the Mobile Launcher Platform, to mitigate the sound shockwave from the engines’ roar and lessen damage to the orbiter. From afar, a torrent of water is seen blasting down from under the platform, as you can appreciate in the picture.

T-10 Seconds.

hyd burn off

Sparks begin to fly. But not yet from the engines. A system called the Free Hydrogen Burn Off System ignites, aiming hundreds of sparks at the engine nozzles, burning off any residual hydrogen that may be in its vicinity. It’s done like this so the ignition of the engines is controlled, and no errant explosions occur that may crack or break the engine nozzles. At the same time, the GLS gives its green light to the GPCs onboard the shuttle to start its engines.

“GLS is go for Main Engine Start.”

Everyone is on the edge of their seats. Will the engines ignite? The RSLS system monitors for the successful ignitions of all 3 engines. Everyone holds their breath.

T-6.6 seconds. The GPC sends Main Engine #3 the start command.
T-6.48 seconds. Main Engine #2 is ordered to start.
T-6.36 seconds. Main Engine #1 is last.

ssmestart

Almost instantly, a loud whoosh and rumble comes out of the launchpad as red hot flames shoot out of the 3 main engines. The instant incredible heat hits the water in the trench, which is divided into 2 sections. A massive cloud of water vapor shoots out of the front of the pad as the water from the SSS is flash-evaporated. At first, the flames look out of control. But just as quickly they settle into a normal down-blasting direction, and the flame blast is almost invisible, save for the white halo core ‘inside’ the flame blast. The engines have ignited!! The entire stack makes a motion, a small nod. If you look at the top part of the ET, you see it lurches forward a bit, then settles back up straight in time for T-0. The movement is completely imperceptible from a moderate range.

Everyone still holds their breath, though. The engines have to reach 100% power within 3 seconds, or the RSLS will cut off the launch. It has happened 5 times in NASA’s shuttle flight record. Everyone silently prays this isn’t a 6th time. 6….5….4…3…

The engines reached 100%. RSLS is standing by for the final command. …2…1…

The point of no return is here.

T-0 seconds. Booster ignition.

LAUNCH

Simultaneously, the SRBs are given the ignite command. Almost instantly, a mass of white-hot flames shoot out of each of the SRBs’ nozzle, flash-evaporating the water on their side of the trench, shooting a massive cloud to the back of the platform. And at the same time, the bolts holding down the entire shuttle stack are detonated, releasing the entire shuttle. Since the SRBs have a powerful thrust, the shuttle literally leaps up and out of the launchpad.

…and LIFTOFF!!!!

discovery_liftoff_2009_nyreblog_com_

ASCENT

The countdown is no more. It is now the mission elapsed time counter. The count is now read as “x days, x hours, x minutes, x seconds into the flight”.

Now begins the ascent part of the flight. As soon as the shuttle clears the launchpad, Kennedy Space Center instantly surrenders all responsibility, communications and monitoring of the shuttle to Mission Control Center at Johnson Space Center, Houston, Texas.

All functions from this point to MECO (Main Engine Cut-off) are controlled by the shuttle’s onboard GPCs, and is fully automatic, unless there’s an emergency. Different milestones occur during ascent. Let’s assume Discovery’s the one lifting off.

NOTE: All times from this point on are estimates based on a real mission. It will vary from mission to mission.

T+0. The GPCs are transitioned into OPS102, the “First Stage Ascent” Phase of OPS1. Discovery lifts off thanks to the combined power of both SRBs and the 3 Main Engines.

T+6.5 Seconds. Discovery clears the tower around this timeframe. Instantly, Mission Control Center at Houston, Texas assumes control of the mission.

T+11 seconds. Discovery does a roll and pitch maneuver. Basically, the engine nozzles move so that the shuttle turns until the top side of Discovery is aiming at the desired flight path. Then it begins to pull its nose up, aiming the nose at the flight path, which is up and away from the pad. It seems like a backflip, because Discovery ends flying upside down. It remains like this for almost all of the ascent. Once the roll maneuver is underway, Discovery’s CDR calls it out.

Discovery: “Houston, Discovery. Roll Program.”
Houston: “Roger Roll, Discovery.” (it seriously almost sounds like rock and roll…. look up STS-119 launch on Youtube and you’ll see… er, hear what I mean, immediately after CDR Lee Archambault’s callout of the roll program.)

T+30 seconds. Discovery’s already flying at 365MPH, 1 mile in altitude, and 7 miles downrange (meaning away) from KSC.

T+45 seconds. Discovery begins to go past the speed of sound, and the main engines are commanded to drop to 60% power to reduce the stress the strong aerodynamic pressure is causing on the orbiter. If you are viewing the launch, at this point, you’ll see the indication of the shuttle breaking the sound barrier because of the vapor-shockwave-like cloud forming around it, usually when something goes past the speed of sound. Later on, the atmosphere is already thinning out, and the stresses are no more.

T+1:05. Discovery’s engines are commanded to throttle up to 104%, its maximum power.

Houston: “Discovery, Go at throttle up.”
Discovery: “Discovery copies. Go at throttle up.”

At this point, the shuttle travels at a speed that makes the atmosphere cause the highest amount of aerodynamic pressure on Discovery. This region, which is quickly passed as the atmosphere keeps thinning out, is called Max Q.

All systems are in good shape. The engines are still going, the fuel cells are healthy and the APUs are working perfectly.

T+1:16. A little over a minute, and Discovery’s already at 1800MPH, 10 miles high and almost 12 miles away from KSC.

T+2:05. The SRBs have burned all of their useful propellant. At this point, explosive bolts are blown that cut off the SRBs from the External Tank. They go up for a bit due to the speed they were going, before dropping down to the ocean, where the SRB Salvage Ships, the Liberty Star and the Freedom Star, are waiting. The GPCs onboard Discovery transition to OPS 103, “Second Stage Ascent”. Now, several abort options are called out, the one available at this point being the “Return To Launch Site” abort, or RTLS abort, if one or 2 engines fail. I’ll explain the abort options on the next post. But note that if in any moment of the ascent, until when the shuttle’s path is permanently increasing in altitude and the shuttle goes past 300,000 feet, all 3 engines fail, the only option is to ditch the orbiter into the ocean

At this point, Discovery is now flying under the power of its 3 main engines. The flight path goes up, remains level, then seems to drop, but then, it goes level, then shoots up in altitude. This is because the 3 main engines don’t have that much power to keep Discovery climbing at first, and the climb decreases until it begins to fall back to Earth. However, since it’s wasted so much propellant at that point, and it keeps wasting it, Discovery begins to get extremely lighter, until the main engines are more than enough to propel Discovery clear out of the atmosphere. It stops dropping, and again starts to climb at an ever increasing rate. Either way, it keeps developing horizontal speed, which is very important. It needs to reach over 17,000 MPH by the end of the ascent.

A few seconds later after the SRBs are released, the OMS engines (remember, the 2 small engines on either side of the back used for orbit maneuvers) fire for a few minutes, providing an assist boost to the 3 Main Engines.

T+2:15. Thanks to the assistance of the SRBs, Discovery’s at 3600MPH, 32 miles high and 43 miles away from KSC, and now accelerating quickly.

T+2 minutes, 39 seconds.

Houston: “Discovery, 2-engine Moron.”
Discovery: “2-engine Moron.”

No, Houston didn’t just insult Discovery’s engines. This is a call to Discovery indicating that they are sufficiently high and fast to make it to a Transatlantic abort landing site if just one of the engine fails. Still, if 2 engines fail, it’s an RTLS abort. If all 3 fail, I already told you. There are several transatlantic landing bases, which are checked before launch and selected due to weather. The two sites usually chosen are Zaragoza and Moron Air Force Bases in Spain. Right now, for this flight path, Moron AFB is chosen. However, all 3 engines are still doing great.

T+3:05. Discovery’s speed is 4,300MPH, 48 miles high and 83 miles away from KSC.

T+3:42. Discovery’s at 5000MPH, 56 miles high and 127 miles away from KSC.

T+3 minutes, 55 seconds.

Houston: “Discovery, Negative Return.”
Discovery: “Discovery copies, Negative Return.”

The first major milestone in the second stage ascent has been reached. Discovery is too high and too fast to be able to do an RTLS abort. Tensions rise, because in this period, 2 engine failures would be catastrophic, but Moron AFB can be reached if just one fails. However, the engines are still burning and at 104%.

T+4:18. Discovery’s at 6000MPH, 62 miles high, 177 miles downrange.

T+4:55. Discovery’s at 7000MPH, 65 miles in altitude, and 235 miles downrange.

T+5 minutes, 17 seconds.

Houston: “Discovery, Press to ATO.”
Discovery: “Discovery. Press to ATO.”

Finally, the shuttle is flying sufficiently fast and high to reach a safe lower orbit than planned if an engine fails. Then it’s just a matter of adjusting the orbit with the OMS engines and the mission goes as planned. But, all engines are still good. To date, only one mission suffered an ATO abort. Tensions rise again, because once again, a 2-engine failure would be catastrophic.

T+5 minutes, 39 seconds.

Houston: “Discovery, Single Engine OPS 3.”
Discovery: “Single Engine OPS 3.”

A welcome sound. At this point, an engine burnout would still initiate an ATO abort (which, when you come to think of it, isn’t really an abort, just a plan to reach a lower orbit and continue the mission), but if 2 fail, the crew has a failsafe. Now a Transatlantic abort to Moron AFB is possible.

T+5 minutes, 50 seconds.

Discovery’s zooming along at 9000MPH. The GPCs command the engines to swivel and cause the entire shuttle to roll to a heads-up position, or right side up again. By 6:15, the roll is complete. This is done to have a better signal and use the NASA TDRS Network, way high above the Earth, for tracking.

T+6 minutes, 3 seconds.

Houston: “Discovery, Single Engine Zaragoza, 104.”
Discovery: “Single Engine Zaragoza, 104.”

The Transatlantic Abort site has been switched to Zaragoza AFB, and can be reached on one engine. If just one of the 3 engines fail, it still triggers an ATO. This will change in a few seconds…

T+6 minutes, 20 seconds.

Houston: “Discovery, Press to MECO.”
Discovery: “Press to MECO.”

Most would breathe a slight sigh of relief at this point. The ATO option is discarded. Discovery is well on its way to orbit, and has a little over a minute to go until Main Engine Cut Off. If an engine should fail at this point, the MECO point can still be reached. If 2 fail, Zaragoza is standing ready.

T+6:40. Discovery’s at 11,000MPH, 66 miles in altitude. Some callouts are done around this point for the MECO plan.

Houston: "Your shutdown plan is nominal. You are GO for the Plus X, GO for the Pitch."

Discovery: "Nominal Shutdown, Go plus X, Go Pitch."

T+7 minutes.

Houston: “Discovery, Single Engine Press 104, good readback.”
Discovery: “Single Engine Press 104.”

An even bigger sigh of relief from everyone. All the scary abort modes are gone, and now, even if 2 of the 3 engines fail, the correct MECO altitude and speed can be reached. The ‘good readback’ remark was to indicate that Discovery read the previous instructions correctly (the MECO plan).

T+7:35. As the ET gets lighter because the 3 main engines have eaten up almost all of the liquid hydrogen and oxygen, the shuttle begins to climb excessively, and accelerates faster than it was doing. The acceleration becomes uncomfortable as the astronauts are pressed like pancakes to their seats. The shuttle also has some structural limits that can easily be overshot if the engines remain at 104%. This is why, at this point, the engines are commanded to throttle down until the GPCs see that the acceleration stress is just under 3gs, that is, they’re feeling they’re just under 3 times heavier than usual. Go to your bathroom scale, and multiply that number by 3, and think about what that means for you.

Astronauts are effin’ hardcore.

T+7:43. Discovery’s massive acceleration boost has it now at 14,800MPH, 64 miles high (over 337 thousand feet, well above the thick part of the atmosphere), and 700 miles downrange.

T+8:30. Discovery’s engines are commanded to start throttling down even more, in preparation for MECO, 8 seconds later.

T+8 minutes, 38 seconds.

The GPCs send the shutdown command to the 3 engines, and cuts off the hydrogen and oxygen flow to them. The engines instantly die out, and the acceleration ceases. In a particular Youtube video, which I will post below, show the several milestones. However, at 10:09 they call the throttle down, and at 10:12, you see the seats slowly bend forward as the engines’ power is lessened. At 10:18, the seats bend all the way to an upright position because they reached MECO, and the acceleration is now 0. It’s fun to hear them whoop as they finally reach initial orbit. Who says they don’t have fun? Apparently this guy doesn’t know that orbiter is spelled orbiter, not orbitor…

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Houston: “Discovery. Nominal MECO on schedule. OMS 1 not required.”
Discovery: “Copy Houston. Nominal MECO, OMS 1 not required.”
Houston: “Good copy.”

The callout confirms that MECO has occurred perfectly and on time. The ‘OMS 1 not required’ call means that Discovery doesn’t have to do an initial orbit adjustment, since launch and ascent went superbly, and it put them in the correct altitude and flight path.

A bit of history. Initially, the shuttles had to do both an OMS 1 and an OMS 2 burn to stabilize the orbit, until NASA explored the possibility of a ‘direct insertion’ launch, coordinating the time of the launch, and the assistance of the OMS engines shortly after SRBs are separated from the shuttle. Almost all flights from there onwards use this launch method, and ultimately saves propellant. An OMS1 burn can still be done if needed. I’ll explain more about orbital maneuvers and how they work at a later post.

MECO

ET Tank sep

T+8:55. The External Tank is released from the orbiter, and the orbiter does a small upward thrust using its RCS thrusters, separating the orbiter from the tank. The tank tumbles downward, and will continue on a ballistic trajectory, meaning up, then down. It’ll burn up over the Indian Ocean. And believe it or not, Discovery will suffer the same fate… but before it does, it will execute its OMS2 burn to stabilize and ‘circulize’ the orbit.

ORBIT INSERTION

And here we are. Discovery is travelling at roughly 17,250MPH, over 400 thousand feet, or slightly 76 miles above the planet. It’s well above the atmosphere, and the guys are weightless. Or are they? More on that on a later post.

Since OMS 1 burn wasn’t required, the crew has time to set up they various orbiter systems in preparation for their stay in orbit, be it thermal control systems (in space… no one can hear you scream “ITS HOT—NO, COLD OMGWTFHAX!!!111” Considering that in the shade, temperatures drop to finger-snapping-off minus 100 degrees Farenheit, and in direct sunlight, a nice, boiling, cancer-causing 200 degrees Farenheit. The orbiter acts as a gigantic Thermos, shielding the crew from said temperature changes), attitude control systems (RCS, vernier thrusters), and the like. In the meantime, the GPCs are transitioned to OPS 105, the final orbit insertion burn phase of OPS 1. OPS 105 executes the OMS 2 burn. (We skipped OPS 104 because OMS 1 isn’t required.)

Right now, the orbiter’s apogee, or the highest point of the orbit, must be at 150 or 200 miles, or something in between. However, the perigee, or lowest point, is still passing under the atmosphere. That has to be changed in order for Discovery to remain in space. Which is where the OMS 2 burn comes in. By accelerating for a few minutes, the perigee of the orbit changes until it is either safely above 400,000 feet, at the same altitude as the apogee, or higher (thus, becoming the apogee), depending on the mission needs. The OMS 2 burn is automatic, and only needs to be commanded to be done via the right keypad on the front of the orbiter. After that, it’s waiting until the orbiter reaches apogee, roughly 45 minutes after it reaches orbit, or, on the opposite side of the planet from where KSC is (at orbital speed, the shuttle goes around the planet once every roughly 90 minutes.) Once it does, the OMS engines fire until the perigee is at the desired altitude, then stops. The GPCs are then transitioned to OPS 106, the final checkout phase of OPS 1 before heading over to in-orbit OPS 2. After the shuttle is checked out, the GPCs are transitioned to OPS 2, and the mission officially is underway.

And that, my friends, is how a shuttle takes off and reaches space. My fingers are bleeding.

On the next post (because I’m a masochist, and because I can), I’ll explain about the abort modes, and later, about the orbit maneuvering and mechanics… which is a bit of geometry in itself.

Monday, September 21, 2009

Your typical Space Shuttle Mission Part 2: Shuttle processing in a nutshell

shuttle-landing-gpn-2000-000965-sw

Hooray! Discovery touches down after a successful mission! Time to work around the clock to get it ready!!! *pulls hair off*

Seriously. No sooner than the orbiter lands, lots of things start to be set in motion. The astronauts power down and safe up the orbiter, until they leave it, in which Kennedy Space Center employees take over (unless the unfortunate possibility of an Edwards Air Force Base, California landing occurred, in which it takes some days for the orbiter to be latched onto a Shuttle Carrier Aircraft so it’s taken back to Florida, THEN it starts).

The orbiter is towed to the nearby Orbiter Processing Facility, in which it’s prepared for its next mission, while being checked for any problems that may have occurred during the previous mission. Sometimes, payload is installed at this point.

142993main_sts121srbstack

In the meantime, the SRBs, refurbished from an earlier flight, arrive at KSC in pieces in trains, and a new External Tank arrives in a wharf (read: big ass boat). Both SRBs are taken to the Vehicle Assembly Building (the famous big, cube-like building in Kennedy Space Center), where a crawler-transporter with a mobile launcher platform on top is waiting. The lower segment of the SRBs are bolted to the mobile launcher platform (MLP), and are assembled from the bottom up.

STS125ETstack1-785885

The External Tank already comes in one piece. It is dragged out of the wharf and is towed to the VAB, where it is hoisted by a powerful crane and lowered between the SRBs, already completed and attached to the MLP. The tank is then latched onto the SRBs.

sts125stack3big-714970

And finally! The orbiter clears the Processing Facility, is finally ready for its next mission, and is towed to the VAB, where it is also hoisted by a crane, and lowered in its position in front of the SRB/ET Stack. Then all connections and bolts are placed, and finally, the entire shuttle stack is complete! Following that is the rollout to the pad.

KSC-96EC-1195

The bluish-gray thing below the white-gray platform is the crawler transporter, and the white-gray platform is the mobile launcher platform. From what you just read, the whole stack is bolted only in the SRB points. Therefore, the crawler has to go at speeds less than one mile per hour to avoid stressing those bolts and having the stack topple over. It must travel 3 to 4 miles to the launchpad. At best, it takes over 6 hours to get there. Once it does, the crawler lowers the MLP into the pedestals in the launchpad, and leaves it there, and goes back to a parking spot it has near the launchpad, where it will wait until launch is over, then it goes back to fetch the empty MLP for servicing and use for a later mission.

So the shuttle sits at the launchpad until the time of liftoff, where it will do its mission, and later come home, and the cycle starts all over again.

Your typical Space Shuttle Mission Part 1: About launch personnel and systems

Shuttle? Check. Launchpad? Check. Systems? Personnel?

Yep, there are various things to be done before an actual launch, and those systems, and several situations are monitored very closely by several people. And those people have to be checking the shuttle and launchpad systems over 3 to 4 days before the actual launch. I can’t tell you the exact realtime frame because that usually varies thanks to the various built-in holds in the countdown. Which brings us to our first, and most important system.

The Countdown/Mission Elapsed Timer

countdown

That up there is one of the most famous timepieces in the planet: the NASA countdown clock. It’s called a countdown clock until the shuttle launches, in which it becomes a “Mission Elapsed Timer”, which is exactly what it is, a timer of the mission’s duration.

The time is read normally when it’s counting the mission duration, but when it’s counting down towards the actual launch, the time is read in the following format: T minus x days, x hours, x minutes, x seconds and counting (or holding). Of course, if the days are zero, it’s ommited, same for hours, and same for minutes when it’s counting from 59 seconds downward. How do you read the above pic?

It would read T minus 9 minutes and counting, but at the moment the pic was taken, it was read as T-minus 9 minutes and holding, because it’s in a built-in hold. ….a what?

A built-in hold are programmed holds in the countdown, where the count stops for minutes or hours, before it resumes. Usually, things are done during these holds, and for the hold to release the timer, they have to have done those things successfully, things like fueling the external tank, turning stuff on and checking, or the infamous flight readiness poll, which is the go/no go for launch call.

The Launch Team

firing room 4

This is a view from an upper console in Kennedy Space Center’s Firing Room 4, where most of the launch team is assembled during the countdown. There are 3 teams that verify if all systems are ok and if all conditions are met for launch. Inside one of those 3 teams is “Houston Flight”, which is none other than Mission Control Center, Houston, but in a launch, they answer to one of those 3 teams. Launch poll goes in the following order: NTD polls his team, reports to Launch Director, Launch Director polls his team, asks for MMT, and MMT gives their go/nogo. Launch Director then reports to the crew that they’re either go for launch, or the launch got scrubbed to a later date.

The NTD, or Nasa Test Director, is in charge or the safety of all personnel on and off the launch pad, including the crew, and works to integrate all of the systems, personnel and crew, testing to verify if all is go for launch. This is the director that initiates the Final Flight Readiness Poll. The teams that answer to the NTD are the following:

  1. OTC - Orbiter Test Conductor, checks all orbiter systems
  2. TBC - Tank/Booster Test Conductor and Tank/Booster Test Conductor, checks External Tank and Solid Rocket Booster systems and fueling operations.
  3. PTC - Payload Test Conductor, verifies the cargo is working and stowed properly.
  4. LPS - Launch Processing System Test Conductors, verifies the systems controlling major aspects of the launch
  5. Houston Flight – Mission Control Center, where the mission will be watched over from.
  6. MILA - Merritt Island Spaceflight Tracking & Data Network Stations, used to track the shuttle on its mission, using the powerful NASA TDRS Satellite Network.
  7. STM - Support Test Manager
  8. Safety Console - Safety Console Coordinator
  9. SPE - Shuttle Project Engineer
  10. LRD - Landing and Recovery Director
  11. SRO - Superintendent of Range Operations, checks for airspace and weather in the flight path of the shuttle, and checks weather constrains 10 nautical miles around the launchpad and 20 nautical miles around the shuttle landing facility in case of an abort.
  12. GLS – Ground Launch Sequencer, an engineer watching over the GLS, a computer managing the final 9 minutes to launch.
  13. CDR – Mission Commander, aboard the shuttle

The Launch Director’s team verifies that all 3 teams, including his team, is ready to support a launch, and gives the final decision for a go/nogo to launch. Mike Leinbach has been the Launch Director for the past several missions. When called to verify go/nogo for launch, he polls his team at the moment, which includes the chief engineer (supervises flight hardware and launch systems and their integration into the launch), the shuttle safety mission assurance officer (advisor for mission management team), payload manager (checks out the cargo to be taken), and range weather (ensures all weather criteria allows for a good launch and, if needed, a good return to the launch site in the event of an abort). Afterwards, Mission Management gives their go, and the Launch Director gives his final decision, and informs it to the shuttle crew.

The Mission Management Team are the executives that work with… well… executive problems and issues regarding a launch and a mission. They are the last to be polled, and the last to report their go/nogo for launch. Up to date, the leader of the Mission Management Team, Mike Moses, polls his team, and when called, gives the go/nogo for launch on behalf of his team.

I’ll give the actual transcript and more explanations of the countdown in the next blog. (finally!)

Wednesday, September 16, 2009

Nifty little tool (pt 2)…

Test posting works. Let’s see if picture posting does too. >.< Had to open a Flickr account… here we go…

shuttle-launch

If you can see this clearly, this is a shuttle launch, viewed from a nearby harbor farther up north of Merrit Island (the island where the shuttle’s launchpad, LC 39A, is). Notice that the shuttle doesn’t go straight up, but rather, go up, and forward (to the east). This is because in order to actually stay in orbit, they must exceed HORIZONTAL speeds in excess of 17,000MPH. The altitude matters little once they reach 400,000 feet, it’s the speed that matters. Watching a shuttle launch from a TV, or from Kennedy itself, gives you the illusion that they’re going straight up, since you’re looking to the east already. This view from a northern part of Florida can’t make it any clearer.

Beautiful, isn’t it?

Sunday, September 13, 2009

An explanation about the orbiter's systems

This is a longer explanation about the Space Shuttle. It has myriads of systems that need to be explained better to fully understand the entire system.



The orbiter has several noteworthy systems. The most important are the 5 GPCs, the 3 APUs, the 3 Fuel Cells, the 3 SSMEs, the OMS. the RCS, the payload bay, cooling systems, the RMS, the TPS, the Aerosurfaces, and later on, the APDS, and OBSS.

The GPCs (longest explanation)

The 5 GPCs, or General Purpose Computers, are 5 computers that have control of all the systems in the orbiter. For all of you old-age science fiction aficionados, imagine 5 HAL 9000s controlling the shuttle... only without AI, following a set pattern of instructions. In order to embrace the horror of it should it have AI (artificial intelligence), I give you a quick photoshopped image:


"I'm afraid I can't let you do that, Dave..." ...5 times.

Ok, so it's not very reassuring imagining our favorite 1960's science fiction insanely homicidal computer, or rather, 5 of them, controlling the air we breathe. This ain't the case, lol. The GPCs ensure automatic perfect operation of the orbiter's systems, and accept input by means of 3 keypads, 2 of them beside the commander's seat and pilot's seat, respectively, and one on the aft-flight deck. In other words, it executes commands, it doesn't 'think' them.

...yet.

Actually, 4 of those GPCs are the primary control computers, and GPC #5 is the BFS, or backup flight system. The first 4 are constantly checking each other and #5. If one of the main computers fails, the others vote it out of system control. To date, there have been no GPC failures, and therefore, no need to use the backup flight system. But, NASA loves to double (or quintuple in this case) up on everything.

The GPCs have several programs, but the most used are 3 programs which control the 3 phases of any mission, called Operational Sequences, or OPS. Each OPS is divided into major modes, for example, OPS 201, and OPS 202, which means OPS 2, Major Mode 01 and 02. And each major mode is divided into Specialist Functions, or SPEC, which control individual aspects of the major mode. Try viewing it like this: You have a computer with an installed operating system, like Windows or Mac OS X (the OPS). You have many programs, but at the moment, you are using Word (the major mode). In Word, you can write documents, or letters, or envelopes, you can spell-check, print, and many more things (the SPEC functions).

The first program is OPS 1, which controls the launch, 8 1/2 minute ascent, and orbit insertion of the shuttle. OPS 101 through 106 control specific portions of final countdown, liftoff and ascent with the solid rocket boosters and the shuttle main engines, the remaining ascent with the shuttle main engines, and orbit insertion. Once orbit insertion is complete, the orbiter's GPCs are transitioned to OPS 2.

OPS 2 controls the in-orbit operations of the orbiter, and is less dynamic than the other 2 main OPSes. Therefore, GPC 5, the BFS, and if I'm not mistaken, GPC 3, are shut down. OPS 201 and 202 have several functions, ranging from orbit maneuvers and course/altitude corrections, operation of the KU antenna and star trackers for tracking satellites or the ISS to payload bay doors and radiators operation, RMS arm operations, orbiter cooling systems, and the like. It is mostly controlled through the aft keypad, unless it's an OMS burn. Once the mission is complete, the GPCs, plus GPC 5, are transitioned to OPS 3.

OPS 3 controls the deorbit, entry, approach and landing phases of the mission. OPS 301 thru 305 control specific aspects of the pre-deorbit configuration, the deorbit burn, the entry into the atmosphere, course corrections, approach, final approach and landing.

The APUs

The APUs, or auxiliary power units, are only used in the launch and entry parts of the mission, and are otherwise shut down. They are the ones responsible for the hydraulics controlling the aerosurfaces and the main engine nozzle gimbal (AKA aiming the engine nozzle). Anyone familiar with planes knows most or all planes have an APU, for the aero surfaces' hydraulics. The orbiter has three.

The Fuel Cells

The fuel cells are compact power plants, using liquid hydrogen and liquid oxygen on the orbiter's internal tank to produce electricity for the entire orbiter, and water as a byproduct of the process. How more eco-friendly can you get? Oh. They're worth AN ARM AND A LEG (best effect reached when said in a low, deep voice). The orbiter has three of them.

The SSMEs

Picture taken from STS-128-Discovery's live coverage, 2 seconds prior to liftoff.


The 3 Space Shuttle Main Engines provide the thrust for the liftoff, and complete ascent of the orbiter. They are fueled by the External Tank, with a mix of roughly 2 parts liquid hydrogen and roughly 1 part liquid oxygen. The exhaust plume the engines generate is no more than super-heated ol' water vapor. Once the engines shut down at the end of ascent and the External Tank is cut off and jettisoned, the engines become useless for the rest of the mission. In other words, the movie Armageddon was a big fat hoax. But a pretty darn good one.

The engines begin to pressurize using their turbopumps a few seconds away from main engine start, which is 6.6 seconds before liftoff, and each powers on 0.12 seconds after the other. Maybe turning them on at the same time is bad, but turning them on one at a time at 6.6, 6.5 something, and 6.4 something seconds is safer? Meh.

The OMS

The Orbital Maneuvering System, the 2 small engines above the left and right SSME, respectively, is what provides for the orbital course correction burns to be executed, known as OMS burns. They have their own propellant, and are used for orbit insertion, changes in the orbit to catch up to a satellite or the ISS, changes in the orbit altitude, and of course, the final deorbit burn. The burns are executed by the GPCs, in which the burn targets are loaded and executed.

The RCS

The Reaction Control System is an attitude and position maneuvering system, comprised of several small jets in the front and back of the orbiter. They fire either constantly, or in pulse mode, making attitude control a breeze. This ensures the orbiter is not spinning uncontrollably, and remains in one set attitude. Also, it's used to be able to match and control the relative movement of the orbiter to the satellite they're trying to grapple, or to the ISS.

The AeroSurfaces

This is the method of control during atmospheric flight. Powered by the 3 APUs, the surfaces are similar to those on a plane, but with slight differences. The normal ailerons and elevators used for pitch and roll on a plane are combined into one on the orbiter and are called the elevons. When deflected into the airstream, they control turning and banking, and pitch. The body flap, a flap in the aft of the orbiter, juts out just below the 3 SSMEs. It serves to protect the engines from reentry, and to provide another means of managing sinking rate. There are 2 additional flaps in the back of the vertical tail in the back of the orbiter. If one opens to the left, the orbiter yaws to the left. If the other flap opens to the right, it yaws to the right. If both flaps open, it becomes a nifty speed-brake.

This system is used to manage the energy of the orbiter, meaning the relation between the speed it's travelling at and how fast it is sinking down, and remember, without engines, the orbiter has only one shot of reaching the runway and landing safely. So one has to make sure he's going fast (or slow) enough, while at the same time making sure the sink rate isn't too fast in order to reach the runway in time, while at the same time staying on course.

The Payload Bay and Cooling Systems

The payload bay is used for ferrying cargo to space and/or back. It supports several payload options. Inside the right side of the payload bay is the RMS arm, and since 2005, on the left side is the OBSS extension. The cargo is protected during launch and entry because of the payload bay doors, which are closed during those phases, Once in orbit, the doors are opened, since the radiators for the cooling system are stored in the inside door panels, coursing with freon coolant, keeping the orbiter systems and cabin within safe operating temperatures. Also inside the payload bay, at the front left edge of the payload bay, is the KU Antenna, which supports high-speed communications like video downlink.

The RMS and OBSS

The Remote Manipulator System is the orbiter's robotic arm, designed and constructed by CSA, the Canadian Space Agency. The code name for the arm is "Canadarm". It has 3 points of fixed movement, at the shoulder (imagine your arm latched onto your shoulder. The point where your shoulder becomes your arm is the point I'm talking about), at the elbow (ditto), and the wrist (double-ditto). The shoulder controls pitch (up/down) and yaw (sideways left-right movement). The elbow only has pitch control. Finally, the wrist, where the "hand" of the RMS, called the End Effector, has controls for all 3 attitude position controls: pitch, yaw and roll (roll is spinning in place to the left or right). These 3 points are used so as to move the end effector to a grapple point. The end effector has a camera to aid with the grappling target. Once contact is made, the end effector is commanded to capture, where the grapple pin is firmly grabbed by the end effector, and thus, executing a successful grapple of whatever it is that needs to be grappled. The arm can then move the grappled object around, and release it whenever it need be. Applications for this include taking a satellite out of the payload bay and hoisting it above the orbiter before releasing it and leaving it behind, or the reverse, possibly for servicing by the astronauts before being released again, or for taking it back to Earth.

The Orbiter Boom Sensor System is an extension boom to the Canadarm, also made by the CSA. It has a grapple point on one of the ends and in the middle of the extension boom. At the other end are laser sensors and cameras. Its use is simple, to be grappled by the RMS, and maneuvered so that the sensors are aiming at the underside of the orbiter. The TPS is scanned for damage, and if no damage is found, the TPS is cleared for reentry. The inspections are done on the second day of flight and 2 days prior to deorbit.

The TPS

The Thermal Protection System, AKA the thermal tiles, these line the nose, the leading edges of both wings, and the whole underside of the orbiter. Their job is to dissipate the heat of the ionized airstream and prevent it from harming the orbiter. Such a very important system is always checked, before, during, and before the ending of a mission, to ensure the safety of the vehicle and crew during reentry (checks were implemented into the mission after the Columbia disaster). They aren't your regular floor and wall tiles. Rather, these are tiles made of high-temperature-resistant material, varying in composition, according to the area it protects. The Reinforced Carbon Carbon Tiles (not a typo... they use the word carbon 2 times), or RCC Tiles, are the strongest tiles, and are used in the nose and wing leading edges, since these are the areas where maximum heating occurs. The other areas use lighter materials, since the heat dissipation isn't as much.

The APDS

The Androgynous Peripheral Docking System is a major upgrade done to the orbiters when the ISS became operational. This allows docking with ISS-Harmony's PMA, or Pressurized Mating Adapter. It's latched onto the front of the payload bay, where the old airlock door of the orbiter was. It allows for more storage room inside the orbiter's crew cabin, as it essentially becomes an extension of the middeck, and when docked to the ISS, is like an interconnecting tunnel between both vehicles. It has a capture ring that is extended, and as soon as it comes in contact with the ISS's mating adapter, it captures it in a process known as soft-dock. Once relative movement between both vehicles has stabilized to 0, the ring retracts, bringing the two vehicles together until the seal is airtight. Several botls and latches are driven to ensure that the seal isn't broken, and once this process is complete, it is known as the completion of hard-dock. The APDS them pressurizes the space between both hatches, and after leak checks, both hatches are opened and the two vehicles are officially one. Once the hatches are closed when joint operations complete, the air is let out of the space between both hatches, and when leak checks confirm that both hatches are securely closed, the APDS releases the latches and bolts, and, thanks to a spring-loaded mechanism, separates both craft.

On my next blog, I will *hopefully* explain the launch milestones, unless I see that further explaining is needed before that.

Saturday, September 12, 2009

Explanation about the space shuttle

The space shuttle is a big technological marvel that never ceases to amaze. And what never ceases to amaze is the amount of technical jargon it can use in a single shuttle mission. I'm going to try and explain these in a nutshell.

A quick navigational tip: Forward is the front, Aft is the back.

The space shuttle, seen here, is the name given to the whole system. The space shuttle system consists of 3 parts. The first, and obviously main part, is the orbiter, the white, delta winged space plane. The second part is the external tank, the big orange tank in which the orbiter is latched onto. The third part is actually 2 parts, the solid rocket boosters, the 2 white 'sticks' latched onto each side of the orange external tank. Easily identifiable in that picture, right? Good.

The Solid Rocket Boosters

The function of the solid rocket boosters is to assist the other two pieces, the orbiter with the external tank, into orbit. It's called Solid Rocket Boosters, or SRBs, because the gasoline used inside them is not liquid, but solid. If you want an easy example, grab a match and strike it. That 1 second flare it does before settling and burning out is done thanks to the tip of the match, which is a typical type of a solid fuel, or propellant. Now imagine that, blown up a million times bigger (I'm exaggerating, but you get the idea). And imagine not just the tip, but ALL of the stick, is solid propellant, sealed inside a cylinder. BOOM. It's funny. I can imagine one day, decades ago, NASA was striking matches and they said, "why don't we build a BIG match and use that as a rocket?" Fast forward to April 12, 1981, where two of those "big matches" helped launch the very first space shuttle flight into orbit. Today, they're still used.

One problem about the boosters is that once ignited, they can't be turned off until they burn out 2 minutes later after ignition. That means that when the countdown hits 0 and the boosters are ignited, the entire shuttle is commited to liftoff, and there can't be any cutoffs until the SRBs burn out. Remember this. Once they burn out, they separate from the external tank and fall into the ocean, using parachutes stored in its nose to reduce its fall, where two recovery ships, the Liberty Star and the Freedom Star, are waiting to drag them back to land for refurbishing for a later flight.


The External Tank: Big gas tank... or is it liquid gas?



The function of the external tank, besides being the backbone of the entire system (the orbiter and boosters are latched onto the tank), is to store the liquid propellant for the orbiter's 3 main engines. Since the orbiter was designed to carry cargo to and from space, it didn't have space for a tank for its main engines. Therefore, the external tank was created. It fuels the main engines on its 8 and a half minute climb to orbit, the first 2 minutes being assisted by the SRBs.

The tank consists of 3 halves. The upper half houses the liquid oxygen tank, where liquid oxygen (also called LOX... because they can.) is kept at -297 degrees farenheit. Think about it, the very air you breathe, chilled to the point where it becomes liquid. The lower half houses the liquid hydrogen tank,, where, of course, liquid hydrogen is stored at−423 degrees farenheit. The middle, called the intertank, contains all the controls for the tank. Because of the temperature of the liquids, the tank os covered in insulating foam, to preserve temperature on the inside, and prevent ice buildup on the outside.

The orbiter: The main part of the shuttle system


The orbiter, depicted here flying around 225 miles above the Earth (picture taken from the International Space Station), is the main part of the shuttle system. This is the vehicle that reaches orbit, with cargo and crew, executes in-orbit operations, and safely returns crew and cargo back to Earth in an unpowered glider configuration.

The shuttle has 4 means of getting around. The first is the three space shuttle main engines (SSMEs), used only in the 8 and a half minute climb to orbit. Above the left and right engine are two smaller engine nozzles, called the Orbital Maneuvering System engines (OMS engines), which are used in orbit to raise the shuttle's speed, and therefore, orbit height, decrease it, decrease it to a point where the lowest point in the orbit causes entry in the atmosphere (that event is called a Deorbit burn), and make course corrections, if the mission calls for it (example, for catching up to the ISS - International Space Station). The OMS engines are sometimes used immediately after SRB separation during ascent to provide an assist boost for the main engines. Third are the RCS (reactant control system) jets, only usable in orbit, several located in the front, and several in the back. They are used to control the shuttle's attitude (position) , move around slowly, and make precise speed corrections, usually for approaching an object in space, be it a satellite or the ISS. During re-entry, the forward (front) RCS jets are turned off, and only the aft (back) jets are used for the maneuvers necessary to bleed off speed. These are later slowly deactivated as the air thickens around the shuttle, in which the 4th control system slowly kicks in: the aero-control surfaces. Nothing special about them, they are the same aero-control surfaces found in each and every regular airplane. They permit control during atmospheric flight like any other plane, and allow the commander and pilot to steer the shuttle towards landing.

"So... they have engines during landing, right?"

NO. They have one shot, and one shot only, to land the shuttle safely. With no engines, the shuttle's like a big, heavy glider, relying on its speed and its aero-surfaces to stay up long enough and remain fast enough till it swoops down to a landing site. Repeat this again, one shot only. Of the 128 missions flown to date, of which 126 made it safely to landing ( the 2 exceptions are explained below), ALL 126 landed successfully. That's for those who complain that astronauts are overpaid. In my opinion, they are UNDERpaid.

The shuttle consists of several components, most notably the crew cabin, payload bay, the engines, which we already covered, the shuttle's robotic arm, and its TPS. The payload bay is for, of course, the cargo payload for that mission. The robotic arm is on the side inside the payload bay, used to grapple things like satellites or cargo. Takes extreme skill to operate it. TRUST ME. The TPS, or thermal protection system, is mainly on the underside of the shuttle, nose, and the leading edges on the wings. They consist of hundreds of reusable thermal tiles that protect the shuttle from the super-heated ionized air as it cuts down into the atmosphere at speeds over 20 times above the speed of sound during reentry. These tiles are resistant to heat, but are fairly fragile to impact damage.

The crew cabin consists of the flight deck, where the commander, pilot and 2 other crew members sit, the mid deck, where 3 other crew members sit, and personal and science cargo is stored, and the lower deck, where shuttle control electronics are stored.

To finish, a little bit of history. Run.

As of this date, there have been 6 built orbiters, but only 5 have been used for actual flights. Shuttle Enterprise was the very first shuttle, used for fitting tests and approach-and-landing tests, but never saw space. Columbia was the second shuttle, and the first to fly. Challenger followed, with Atlantis and Discovery completing the 4-shuttle fleet.

Unfortunately, Challenger was lost in a regrettable and tragic accident, just 73 seconds after liftoff on its ill-fated STS-51L mission, along with its crew (the would-be first teacher in space was on that flight) and cargo (the most important being a NASA TDR Satellite (or TDRS. Will explain in a later blog.)). One of the SRBs produced a leak, which was more like a flare, due to an overlooked design flaw, which burned into the external tank. At T plus 73 seconds (meaning 73 seconds after ignition and mission start) the SRB broke free of the external tank and collided with it, breaking up the entire system. Because of the already fast speeds they were going, the air pressure broke everything up that would otherwise be in a perfect orientation to allow good air passage, producing that image you see above. It was all over in less than a second. The two clouds jutting above the massive one are the SRBs, free of the external tank and flying crazily out of control, before the range safety console detonated them (more explanations about the different launch and f light controllers at a later blog). A very sad January 28, 1986.

To replace Challenger, the youngest shuttle of the fleet, Endeavour, was made. The SRBs were corrected of their design flaws. The external tank was also revised. Several contingencies were created to prevent this, and any related accidents at liftoff. The crew even began to use full-pressure suits, as it was later discovered that some of the crew were still alive after the breakup, but suffocated due to air pressure loss, and... let's say fortunately, were unconscious the moment the cabin section of the broken orbiter hit the ocean at over 200MPH. They said this would give them a chance should cabin pressure loss should occur.

...they forgot about re-entry.


I remember this. February 1, 2003. I came home from college, turned on the TV, tuned into channel 4, and this video burned into my eyes. The fragments of space shuttle Columbia breaking up as they reentered the atmosphere.

Apparently, at launch, a piece of foam broke off the external tank and impacted the leading edge of the left wing, where most of the heat is concentrated on during reentry. At the speed they were going, a briefcase-sized chunk of foam (or, imagine your laptop, but made of foam) was as lethal as a car hitting you at over 100 miles per hour. This broke off several thermal tiles off the left wing's leading edge. Engineers voiced concern, but since this has happened before, albeit on lesser critical areas, mission management waved off those concerns. Unfortunately, the engineers' concerns came true, as during reentry, at the point of maximum heating of the critical areas, the spuer-heated air penetrated the leading edge, and started to break up the shuttle. When the shuttle lost all control, it pitched and rolled violently, exposing the more fragile parts of the shuttle to the high-pressure, high-temperature air stream. Within seconds, the shuttle broke up, becoming a mass of meteorites streaking across the Texas sky, still going at over 10 times the speed of sound. Even if they had bailed out on time, they were going at such an extreme speed, that if the high-pressure current didn't break them apart like paper, the high-temperature, ionized air would have burned them.

....astronauts who still brave the shuttle are sorely underpaid.

The shuttle fleet was grounded on both tragedies. Years passed, accident reports, investigations galore... in the post-Columbia scenario, they evaluated that there was nothing that could be done, due to the reasons stated above. So they opted for early failure detection mechanisms, and contingency plans to send a rescue mission while the orbiter with the failed TPS awaits at the International Space Station, by that moment operational, albeit much smaller than it is today. To detect any problems in the TPS, new, more powerful, higher resolution cameras were installed throughout the launch pad, and the orbiter was equipped with an extension to their robotic arm, called the Orbiter Boom Sensor System, or OBSS, which is maneuvered to aim below the orbiter to scan the underside for possible damage, both on the second day of the flight, and 2 days prior to the first scheduled deorbit burn. On missions that head directly to the ISS, the ISS crew members poise themselves on a window as the orbiter approaches. Once within 600 feet, the orbiter does what you may consider a backflip. It spins up, until the underside it in plain sight of the ISS, where the ISS crew takes a hundred and something hi-res images of the TPS, before the orbiter returns to it's upright opsition before initiating docking with the ISS.

After the tragedies, the next shuttle flight mission was called, on both times, the "Return to Flight" mission. After Challenger, almost 3 years later, on September 29, 1988, STS-26 was launched. After Columbia, on July 26, 2005, the more known second Return To Flight mission, STS-114, flown by ex-astronaut Eileen Collins, the first woman to be an STS mission commander, testing the new systems designed to prevent a second Columbia-like scenario. Guess which was the shuttle selected for both Return To Flight missions?

Discovery. My favorite orbiter. We're both the same age. Discovery just celebrated its 25th anniversary, and I'm also 25. Lol.

There's been several controversies in that the shuttle system is unsafe, and requires everything to be perfect to be able to commit to anything, be it launch, any inorbit operation, and of course, entry operations. Also, there's been speculation that the amount of money wasted in the shuttle era is substantially more than what was wasted in the Apollo era. Consider this: each and every piece of the Apollo vehicle, the one used to reach the moon, was expendable and non-reusable, meaning they were purchasing new rockets, new engines, new flight hardware, everything, with every launch, since everything either got lost in orbit, burned up in the atmosphere, or got lost in deep space. With the shuttle, only the external tank is expendable. The orbiters and the SRBs are reusable. But when something in the reusable parts breaks, ooooooooooooh boy..... not to mention that Apollo could land anywhere in the open ocean, provided a U.S. Navy Aircraft Carrier was close by to pick them up. The orbiter only has one single shot to land at one of 3 places, either Kennedy Space Center, or Edwards Air Force Base, California, or the last resort, White Sands Missile Testing Center. If all three, by any stroke of incredibly lousy bad luck, were under siege by weather conditions, our astronaut friends would run out of air and die, unless they decide to risk a landing at a non-supported airstrip, assuming the landing strip is wide and long enough for the orbiter. Thankfully, this freak event hasn't ever occurred.

...yet.

On my next blog, I'll talk about the milestones during a launch event.