You wake up the morning
of the launch, about three hours before liftoff. Prior to this, the launch vehicle
has been fueled overnight. As part of the last minute training for your mission,
your sleep cycle has been synchronized so that a liftoff with no delays in the countdown occurs at about 9:00 in your workday,
assuming youd wake up at 6:00. Let us therefore assume that lift-off time for
your mission is 9:00 in the morning.
Some of the established
NASA traditions for astronauts include the breakfast, typically with cameras present for a last posed portrait before liftoff. After this, you are suited up. The old
suits were blue flight suits with no pressure capacity, and helmets hooked up to emergency air packs. After STS-33 these were replaced with orange full pressure suits called Launch and Entry Suits. These orange suits also replaced the 1m diameter rescue balls carried for rescue spacewalks. In the unlikely event of cabin pressure loss or another problem with the cabin pressure during launch or
entry, this suit will keep you alive while an abort is performed.
After this is the walkout. Amid a usually modest flurry of cameras and reporters, you make your way to the silver
van that will take you to the launch pad. (Bigger media crowds were present on
STS-1, the first Shuttle launch, STS-33, featuring Christa McAuliffe, the would-be first teacher in space, STS-26R, the first
flight after the STS-33 launch disaster, and STS-95, featuring John Glenn on his second flight, his first being the first
ever manned orbital mission of NASA, the reason for his fame. Ironically, STS-107
had an unusually small crowd due to the security measures around Isreali astronaut Ilan Ramon.)
After arriving at the
pad, the pad elevator takes you to the White room, the small room in the end of the crew access arm next to the shuttle hatch. A small carpet has been rolled out for you over the hatch bottom to protect it from
being damaged by the closeout crew and astronauts walking over it. The closeout
crew is beginning to power up the shuttle in preparation for the arrival of the astronauts, and after helping you into your
seat (which is oriented 90 degrees backwards, making it hard to get into), they make sure the hatch is properly buttoned when
they leave about 20 minutes before the launch.
The countdown has several
planned interruptions or holds where the countdown is stopped, usually for set periods.
There are other opportunities to stop the countdown in case of problems. On
this mission, the hold at T - 9:00 (T minus 9 minutes) lasts 45 minutes. The
launch window is only 5 minutes long and the T - 9:00 hold is there to take up the slack left in the countdown for previous
delays to line up the countdown with this launch window. The reason why the launch
window is so small is because youre mission has a rendezvous target (like the Hubble Telescope, or the Space Station.) In order to rendezvous efficiently on orbit, the Shuttle needs to be launched into
the orbital plane of the target. The orbital plane does not change with time,
but the earth rotates, so the launch site is only under the orbital plane twice per day.
There is only one launch window per day because the Shuttle must fly northeast from the launch window, and the other
pass would require a southeast launch. The launch window occurs roughly the same
time each day. In fact, the daily launch windows occur about 6 minutes earlier
each day because the orbital plane of the target is also fixed relative to the sun, and earth revolves around the sun as well. Launch control orders a hold at the last opportunity T - 5:00 to wait for a report
on the weather at the Zaragosa downrange landing site in Spain, at which the Shuttle might land in an abort situation. The weather at Zaragosa is a go, so the countdown continues.
The crew access arm
had already retracted two and a half minutes before the hold. At T - 4:30 the
shuttle goes plugs-out, meaning that it is powered by its internal fuel cells with no help from the pad. At T - 2:00 the beanie cap on top of the external tank, there to keep ice from forming on the tank, which
can then break off and damage the tiles on the bottom of the Shuttle. T - 31
seconds is when the computer gives a go for autosequence start. This is the first
opportunity your launch can be scrubbed by a computer. The next occurs at T -
20 seconds when the autosequence actually starts. At this point, the computers
on board the shuttle are making thousands of decisions per second to bring the crew for launch, and a thousand times each
second, are considering whether or not to scrub the launch.
At T - 15 seconds, the
launch pad begins drowning itself in water to prevent damage from the solid boosters to the orbiter and external tank from
shockwaves rebounding back into the shuttle just after lift-off. At T-9 seconds
the hydrogen burn off system starts. This is the shower of sparks just before
main engine ignition that make it look like NASAs using a fancy match to start the motors.
This system is actually used to burn the hydrogen used to start the main engine turbopumps in order to prevent the
concentration of hydrogen from rising to the point where it could start a fire. At
T-6.6 seconds, the main engines start, one at a time staggered by 0.12 seconds (so actually, T-6.60, T-6.48, and T-6.36 seconds
is when the engines start.) This pushes the vehicle down from your perspective,
and (over about 6-12 inches, visible in close-up videos.) The shuttle rebounds
back to the vertical just in time for booster ignition and lift-off.
The boosters burn for
2 minutes, during which time they cannot be throttled down or shut down. If something
goes seriously wrong early enough in the flight (as happened on STS-33), there is nothing that can be done about it. The shuttle rises straight up for 7 seconds and then begins to roll right and pitch
over. This brings the shuttle in line with the orbital plane of your docking
target (I oversimplified a bit here, forgive me) with the shuttle upside-down hanging from the external tank. You can hear Mission Control as it takes control of the shuttle over from Launch Control say Roger Roll,
in response to the commander.
At 30 seconds, the shuttle
approaches the speed of sound and aerodynamic pressure build up on the shuttle. This
is, in astronaut tech-speak, known as Q-bar. The point at which this pressure
peaks as the shuttle begins to clear the atmosphere is known as Max-Q, a familiar term if youve watched shuttle launch videos. The engines throttle down to 65 or 72%, depending on the mission and payload, to lower
Max-Q and prevent damage to the shuttle. At 67 seconds, the engines throttle
back up. The commander and mission control exchange Go at Throttle Up.
At 90 seconds into the
flight, the launch stack weighs half as much as it did on the pad, even though it doesnt look like it. This is a reality of high thrust rocketry; you are going to expend a lot of fuel on the way to orbit. Fuel in this case includes the oxidizers, which are required because oxygen isnt available
in space. In the shuttles main engines, the oxidizer actually weighs six times
as much as the fuel. Because the fuel and oxidizer for the last second of the
ascent burn have to be carried along for the previous 509 seconds, the requirement adds up exponentially. The formula has been used in calculations for the ISTS concepts in the main document.
Back to your flight,
at two minutes, the boosters burn out and are jettisoned and cleared from the shuttle in spectacular fashion by frangible
bolts and small solid motors, separate from the main motors. At this point, your
first abort mode becomes available, RTLS, which stands for Return To Launch Site. In
this abort, the shuttle continues downrange to use up excess propellant in the external tank, and then pitches around under
power by gimballing the main engines. At cutoff, the shuttle is flying fairly
slowly, and can simply glide back to the landing runway at the Kennedy Space Center.
Shortly after the boosters
stage, you hear Mission Control say Two engine Moron. This means that if one
of the main engines quit, the shuttle can land at Moron, Spain by executing a TAL abort, which stands for Trans-Atlantic Landing. This is alternately known as a transoceanic abort, but strangely, not as an intercontinental
abort. At just past 4 minutes in this quieter phase of the flight after those
noisy solid rocket booster have cleared, you hear mission control call up Negative Return.
This means that your shuttle has used up too much fuel and is going too fast, too high, and has gone too far to be
able to return to the Kennedy Space Center in an abort situation. Fortunately,
you can still land at Moron if something goes wrong.
Shuttle, Houston, you are press to ATO, select Zaragoza. This mission control call says that the shuttle can get abort to orbit if one engine
fails. If this happens, you still get to go to orbit, but wont be able to dock
with your target. Select Zaragoza, means that your shuttle will land at Zaragoza
instead of Moron if a TAL abort is needed. Abort to orbit isnt viable in all
emergency situations. If you lose cabin pressure, for example, youre not going
to want to go to orbit...youre gonna want to get back on the ground fast!
Shuttle, Houston, you
are single engine OPS 3. This cryptic call, not usually explained by the NASA
commentator, means that the flight software needs to select an entry mode instead of an abort mode if two engines fail. This is because the shuttle is going fast enough that a proper series of banking S-turns
is required to slow the shuttle down safely. If this were to have happened while
that call was being made, youd likely be parachuting into Portugal or the ocean.
A few seconds later,
Shuttle, Houston, you are press to MECO. MECO stands for Main Engine Cut-Off
and reflects that your shuttle is going fast enough that it can make its regular orbit, and still dock with your target, if
one engine fails.
Single Engine Zaragoza
104" is short for TAL to Zaragoza, Spain if two engines fail. The one remaining
engine is throttled at 104%. This is actually normal throttle. 109% is overdrive for these engines. The latest batch of engines
has been tested on the stand up to 120%, but well never see that used in flight, I hope.
The last two calls before main engine cut-off is, as you might guess, Single Engine press to ATO, and Single Engine
press to MECO. You might be thinking about what might happen if all three engines
should fail, but thats not likely, because it is such an unpleasant topic. 20
seconds after MECO, already startling in itself because of the instant transition between 3g acceleration and total weightlessness,
the External Tank separates with a startling clang.
The shuttle, despite
using such a small proportion of its total volume for its cabin compared to earlier craft, is still quite roomy with two decks. The cabin consists of the flight deck, with most of the instrumentation and all of
the windows, and the mid-deck, which side hatch, payload bay hatch, and on some missions, the mid-deck airlock. The flight deck does have overhead hatches for emergency egress (exiting the vehicle) in case of a water
The space shuttle can
also carry many payloads which add to its habitable volume, making it even more roomy.
The earliest was the Spacelab system, designed and built in Europe. In
this system, the payload bay hatch on the mid-deck leads to a tunnel, which in turn, leads to the Spacelab module. The more modern Spacehab system flown on STS-107 an several other missions, is nearly identical in concept,
but also includes logistics modules for servicing both Mir and ISS space stations. STS-88
added habitable volume in a much more interesting way: It carried the Unity Node to the Zarya module, starting the International
Space Station. They used the robotic arm or crane, formally known as the remote
manipulator system or RMS, to lift the Unity mode out of the payload bay and dock it on to the docking module at the extreme
forward end of the payload bay. This docking module contains the docking port
for the International Space Station and is now standard on most shuttle launches.
After docking and opening
Unity Node on the docking port, the Shuttle Endeavor rendezvoused with the Zarya Functional Cargo Block (the Russian acronym
is FGB, not FCB as would be the English convention.) The basic description of
Zarya is basically a spaceborne locker room with thrusters and solar wings. This
seemingly unglamourous device is the logical first step in a space station by providing maneuvering and power generation functions
to the station while waiting for the proper modules for those functions to arrive.
Your shuttle is equipped
with a station docking port for your target, an Ariane 5 launched Treehouse man-tended research module, not a full blown space
station that can be continuously occupied. (Note: the Treehouse is totally fictional.) You have previously been visiting the Treehouse with Delta Sprint, an interim spacecraft
used to resume manned spaceflight from the US in a small way until the shuttle could become operational again after the Columbia
catastrophe at the end of STS-107. The Shuttle might be a far cry from Delta
Sprint in terms of the state of the art of space system reusability, but the Shuttle has a payload capacity some 30 times
what the Delta Sprint could handle. As the shuttles commander is talking to Houston
about the upcoming NCC rendezvous burn, you can just see the Treehouse by pointing a 28X telescope (not standard equipment)
out one of the overhead windows. Nestled between its two large solar wings is
the two modules it consists of, the blocky looking Treehouse module itself, and a Delta Sprint logistics ship, left in space
as a lifeboat.
The shuttle is carrying
the standard issue ISS docking module in the forward portion of the bay. You
ignore this as you float from the payload bay hatch down the tunnel to the Spacehab double logistics module, crammed full
of electronics and experiments for installation into the Treehouse, and food and consumables for a three week mission. Aft of this is an international airlock (fictional) which is capable of supporting
both Russian Orlan and US EMU/MMU spacewalking suits. There will be several spacewalk
missions to install the Treehouses exposed experiments facility, which is at the very back of the bay. Eight feet off to your right, and up, although you cant see it because its outside, is the Canadarm space
crane, formally known as the Robotic Manipulator System or RMS.
The functionality of
the shuttle compared to the Delta Sprint is plainly obvious as you begin unloading the experiment racks from the huge logistics
module for installation into the Treehouse. The Canadarm installs the Exposed
Facility, and three spacewalks are made to complete the connections and set up the exposed experiments. Finally, near the end of the three weeks, the experiments left running on the Treehouse are shut down,
sealed and stored in the shuttle for the return trip. The shuttle undocks, leaving
the Treehouse unmanned for another six months, running passive experiments not requiring continuous human presence in order
to run (the continuous human intervention experiments run, predictably, on the ISS.)
Once again, you put
on your orange Launch and Entry Suit and take your seat, as the Commander and Pilot discuss the deorbit burn, as well as the
weather at the Cape, which is very favorable. For coverage of imaging systems
over Europe, the Treehouse was put on the same inclination that STS-107 flew on (39 degrees).
There is a pang of remembrance and a short, informal moment of silence when Mission Control mentions that the orbit
335 entry ground track is nearly identical to Columbias last entry.
This entry is perfectly
normal. You can see the plasma vortex forming just above your head outside the
overhead window. The glow out all the windows is a fiery pink before you can
feel any effect of gravity. Thinking that perhaps its just your imagination when
you first feel it, you let go of your digital camera in mid-air and watch it float towards your lap. As soon as that happens, the commander and pilot excitedly announce that the shuttles sensors are starting
to feel gravity again.
The tension of the entry
grows as the shuttle nears the point where Columbia broke up. The pink
glow yields to a fiery yellow at maximum heating, and the shuttle banks over to its second roll reversal, with its left wing
tipped down 57 degrees. The Capcom says Shuttle, Houston ... Guys, youre over
Dallas right now. Its awfully quiet down here, so you guys remember to breathe,
eh? The commander replies quite normal sounding, Roger Houston, go at Dallas,
and everything up here is tickety boo. The shuttle descends over New Orleans
and starts to look like normal airliner type flight again as the gees ease off and you can lift your camera again.
Youre trying to admire
the view as you overhear the only glitch of this particular landing, Your slightly high at the 180 as the shuttle turns around
in the heading alignment cylinder to line up with the Kennedy Space Center runway. You
barely feel the main gear touchdown, but the nose gear touching down is an obvious whump as the cockpit end of the shuttle
comes to rest.
So this, the step rocket
that lands like an airplane, is the illusion of routine spaceflight. They say
the solid rocket boosters are reusable, but that isnt entirely accurate. They
are basically fished out of the ocean and raided for spare parts. The boosters
are taken apart into smaller segments and shipped by rail to Utah, where they are rebuilt and refueled before being shipped
back to Florida, where they are again painstakingly reassembled. The flight frequency
of the shuttle is now so low that event he true reusability of the orbiter can be questioned.
Every 3 or 4 missions now, the shuttle is stripped down and rebuilt because of changes in technology, such as the Glass
Cockpit, which replaced the original clunky, electromechanical instrumentation with modern 777-like LCD displays. The external tank was never reusable, nor was it ever intended to be.
Occasionally it can be seen in pictures of space stations which proposed to lift tanks the last little bit to orbit,
where they would then be fitted out as the main elements of space stations. This
is the closest the tank ever got to being reused.
Did you know before
your trip on the space shuttle that a company named Aerojet General built a facility for building huge solid rocket motors
in single unsegmented pieces right in Florida, next to the Kennedy Space Center. This
would have eliminated the problem that caused the Challenger catastrophe because it was a problem with one of these
segment joints that brought her down. You cant have a problem with segment joints
if you dont have segment joints. They actually built and fired a 260 inch
diameter motor, about 50% heavier than the 156 inch boosters used on the space shuttle.
Aerojet Generals first bid for the original solid rocket boosters was rejected in 1974 when NASA selected Thiokol from
Utah to build the boosters (The administrator at the time was from Utah, this might have had something to do with it.) Aerojet Generals second bid in 1986 after the STS-33 Challenger disaster was
also rejected. The facility has since been sold and shut down. (Details at http://www.astronautix.com/engines/aj2602.htm.)
Aerojet Generals big boosters would have been safer and easier (and cheaper) to reuse than the ones they actually got.