by Fred Leslie, Payload Specialist, USML-2 (STS-73/Columbia)
There
is no sharp boundary between the Earth and space. The atmosphere gets thinner
as you move away from the surface (ever had your ears pop on an elevator
- that's what's happening). Near 3 miles it is too thin to let you get enough
oxygen to think clearly. At higher altitudes you gradually succumb to altitude
sickness and could eventually suffocate for lack of air. That's why mountain
climbers carry oxygen bottles and crews in unpressurized aircraft wear oxygen
masks or even full pressure suits if the plane is going above 14,000 feet.
For its records, the International Astronautical Federation considers that space starts at 62 miles (100 kilometers). The air is still thick enough to drag a satellite from orbit in an hour or two, so most spacecraft go into orbits at least 100 miles high. Even then a little atmosphere is left that will drag them back after a few days or weeks. The Space Shuttle usually orbits at 185 miles (300 km) - our flight was at 170 miles -- and many satellites orbit much higher if they are to last.
This is no doubt one of the most exciting parts of the mission. After the ground crew helps you strap into the seat and connect your launch/entry suit (a modified SR-71 spy jet ejection suit) to communications lines, cooling water, and oxygen, they leave and seal the middeck hatch. A leak test to ensure cabin integrity makes a loud hissing sound.
All of this adds to the anticipation of the launch. As the countdown continues, the vehicle seems to come alive since I felt vibrations and bumps, and heard noises, as Columbia made final preparations to bolt skyward. At about 6-1/2 seconds before launch (T-6.5 sec.), the three Main Engines ignite and the entire Shuttle vibrates. A T-0 the Solid Rocket Boosters (SRBs) ignite and the Shuttle is released. The noise and vibration increase and you feel the acceleration skyward. However, the ascent is not so violent that you cannot communicate through the headset.
As it picks up speed through the thick lower atmosphere, pressure on the Shuttle increases. The Main Engines are throttled back to reduce the aerodynamic loads - called "Q"when it is strongest - until the atmosphere is thinner. Then the engines throttle up.
After about two minutes (T+2:00), the boosters burn out. The Shuttle again throttles back to ease the jolt when the boosters are jettisoned and the Shuttle drops almost 200 tons of empty steel and equipment. When they leave, you see a flash of light in the windows from the small rockets that push the boosters away. Then the ride smoothes out as the Main Engines alone continue to push us "uphill."At this point the acceleration reaches its maximum of 3 g - 3 times the force of Earth's gravity - and stays there until Main Engine Cutoff (MECO). The acceleration is controlled to reduce stress on the Shuttle structure and on the passengers.
It takes about 8-1/2 minutes from lift-off until the main engines are shut down and you're almost there! The Shuttle is designed so the Main Engines shut down and the External Tank is jettisoned while the Shuttle is short of orbital speed. This ensures that the empty tank re-enters the atmosphere and burns up over the ocean.
About 45 minutes after MECO, the Shuttle Orbiter fires two smaller Orbital Maneuvering System engines to give it the final nudge into orbit. These engines are also used to slow us down at mission end to return home.
Yes, under certain circumstances. If an emergency exit (NASA calls it emergency egress) is required before liftoff (e.g., a fire at the pad), the crew can open the side hatch (that was my assignment since I sat near the hatch), get out of the Shuttle, and hurry over to some slide wire baskets.
Once in a basket with one or two others, you just hit the release, and you glide away from the launch pad to an concrete blast shelter. Once there, we can drive an M-113 armored personnel carrier away from the area. If a problem develops in flight (either on the way up or down) and the orbiter does not have enough energy to glide to a runway, we would have to bail out. In this scenario the SRBs and External Tank will have been jettisoned and the orbiter autopilot engaged to slow its sink rate and airspeed.
At around 40,000 feet and descending, a crewmember depressurizes the cabin. At around 30,000 feet, the side hatch is jettisoned and a bailout pole is extended out the side of the orbiter (this also was my assignment). Finally, each crewmember, in turn, attaches their lanyard to the pole and jumps. The pole guides them away from the fuselage so they are clear to fall free. A parachute is then automatically deployed around 14,000 feet to the slow the crewmember's descent. Of course, this has never been required since the system was developed.
A
number of things are different. In the absence of gravity's effects (gravity
is balanced by orbital motion, so we are really in freefall), fluid that
normally pools in the lower part of the body shifts upward. Initially this
makes your head feel a little full like when you do a hand stand. It was
noticeable but not annoying for me since I did reduce my intake of fluids
just before the flight. After a couple of days, I didn't really notice it
at all.
The feeling of orientation also changes. Even though the body cannot detect up or down, my mind determined orientation. Since I had trained in mockups of the orbiter in the landing position, the floor seemed to be "down" for me. The Spacelab tunnel has no obvious top or bottom, so I often felt like "down"was where my feet happened to be. Eventually, I could even trick myself . For example, I could put my feet on the ceiling and in a few seconds would suddenly feel like the ceiling was now "down."
Moving around in zero-g seemed natural to me. From the ground, capcom (capsule communicator, a term left over from the 1960s) Marsha Ivins (an astronaut) said it looked like I had flown before. An important thing to remember is not to push off too hard: you have to absorb that momentum when you hit the wall just a few feet away.
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| Patuxent River (Md.) Naval Air Station, southeast of Washington. | Typhoon Anglea swirls over the Pacific Ocean on its way to The Philippines. |
I noticed several things that were so much different from photos and movies of the Earth. One is that the Earth on the sunlit side is very bright. Like opening a window on a sunny summer day. it fills the cabin with light. Another is that you can see so much more detail because the eye is better at seeing a greater range of brightnesses than most cameras which tend to overexpose the bright areas if you are photographing something in the darker areas. Because of this it was easy to see the bright continents and ocean simultaneously with the darker thin shell of atmosphere fading to black with altitude. Finally, there was a definite 3-dimensional appearance in that mountain ranges stood distinctly above the surrounding terrain and clouds even higher. On the dark side, you could usually find an active thunderstorm somewhere by the lightning flashes.
Much of the food I had was dehydrated and stored in plastic bags. To prepare it, I took it to the galley (in the middeck on the port side) and placed it in the rehydration station - basically, a special water fountain. A needle penetrates a septum in the bag and you just dial in the amount of hot water you want and hit the hot button. The bag fills with hot water and you let it soak it up for a few minutes. Drinks are prepared in a similar way with cold water. The water is actually created as a biproduct of the fuel cells that makes the ship's electrical power by combining hydrogen and oxygen. Some food was in sterilized packages and just needed heating in the oven below the rehydration station.
It seems traditional to knock the food, but I thought
it was OK, although it can be characterized as warm and soggy. Before the
flight, our crew met with the NASA dieticians and tasted just about everything
that can be flown. We individually ranked each item and came up with our
own personal menus. The dieticians reviewed this and worked with us to ensure
that we had the necessary nutrients and calories for each of the 3 meals
per day. Our food packages were marked with a color identifying them for
each particular crewmember (mine were brown, the pilot's were yellow, and
so on). In reality, of course, once you get up to space, you do what you
do at home. We'd open up the food containers and just take what seemed good
at the time.
On
my flight, we slept in middeck sleep stations, boxes mounted against the
starboard wall with sliding doors which dampened out any cabin noise. Since
half the crew was awake while the other half was sleeping, it was important
that the sleeping crewmembers be isolated from activity in the middeck.
On some flights, the entire crew sleeps at the same time, so they just carry
sleeping bags that are attached to the walls.
I don't think anyone on our flight was apprehensive. We had been delayed so many time, we all just wanted to "get out of town." I had two desires waiting for liftoff. One was that we would encounter no more delays and the other was a hope not to suffer from space sickness for which there seems to be no way to determine preflight.
We were fortunate. No one got sick on our flight. Usually half the crew develops some symptoms of space motion sickness. It usually goes away after about three days, but there is a lot of individual variability.
Yes.
On our flight each crewmember was allowed to take 20 small personal items
in a Personal Preference Kit that met certain criteria. In addition, each
crewmember could also take 10 non-personal items for organizations (like
schools, clubs, etc.) in his Official Flight Kit. We also took 6 albums
(cassette or CD) each of music to listen to.
I did come back with a personal item that I
did not take up. My girlfriend took a child's book, I want to be an
astronaut, and pasted pictures of me and had friends add humorous comments
in it. Then she asked astronaut Cady Coleman to bring it along as part of
her personal kit. After we arrived on orbit and started to work, the book
was presented to me.
There is no shower on the Space Shuttle. "Bathing" is like a sponge
bath. Just squirt warm water into a bag of body bath and wipe yourself clean
and dry off. We also use a "rinseless"shampoo. Just lather it
into your hair, moisten, rinse, and wipe off. It actually works much better
than it sounds.
Pretty much the same as you do on Earth. On the Shuttle, the toilet is called the Waste Collection System (WCS). It works similar to Earth toilets except that is uses an air flow instead of using gravity to separate us from the waste.
I
would certainly like to, but I was a payload specialist as opposed to a
career astronaut. Career astronauts go into a regular rotation for flight
assignments. Payload specialists are used when a specific expertise is needed
for a mission that is not available in the astronaut corps. This typically
occurs for Spacelab missions which will be phased out as the International
Space Station becomes operational. It's not clear yet if or how payload
specialists will be used on the station.
Back to the start of the story.
Updated Jan. 28, 1997
Authors: Dr. Fred W. Leslie
, Dave Dooling
Curator: Linda Porter
NASA Official: Dr. Gregory S.
Wilson