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STS-111 International Space Station
Question and Answer Board

Krunal from Bensalem, Pennsylvania
Do you believe in that the design of the ISS will cause a problem in case of a meteor shower? Why?
That's a really good question. The space environment is a very harsh environment: there's radiation and micrometeorite strikes, and other things in the environment that cause it to be very hazardous. So, one of the things that we've designed the space station for is to protect the astronauts against micrometeorite striking the outer shell of the space station. Now, in doing so, the basic design philosophy of the pressurized modules has been to develop an inner shell, which contains the pressurized interior of the space station, and then a layer of insulation around that inner shell, and then an outer armor plating, if you will, to the exterior. And what that does is protects against small pieces of debris that strike the station and can cause leaks. Now, for larger pieces of debris: they actually track them and have to actually move the space station out of the way of the larger pieces that could cause serious damage to the station.
Luis from San Juan
What kind of contingency plan does the ISS have in case of an emergency? How long do life support systems on board last for the stranded astronauts? Is there such a thing as an emergency launch to the ISS using the current space shuttles?
Well, there are several redundant systems on the space station, which really enable the astronauts to survive for long periods of time without a space shuttle or a Russian re-supply ship coming to bring additional supplies. Now, in the event of an outright emergency, where the lives of the astronauts were threatened, they would have to evacuate the space station using the Soyuz module, but the life support systems themselves are designed to last for months at a time without a re-supply ship.
Mark from Whitehaven, United Kingdom
What would you say to date has been the greatest benefit to mankind from the space station, and what is its predicted benefits?
Well, I think it's all a matter of judgment, but to me the greatest benefit of the space station is the international cooperation to date that we've had with over 16 different countries contributing to the International Space Station; countries that were at one time, enemies of each other, have now come together to do something that will benefit mankind. I think down the road the space station will bring great leaps in science, in medical fields, in the materials manufacturing fields, and it will also teach us a lot about long duration human space flight so that we can expand our civilization beyond Earth.
David from Oakdale, California
Why is the center truss section called S-Zero?
That's actually a really good question, because the trusses are named for whether they're on the starboard side or the port side; so you have S-Zero, S-One, P-One, S-Three, P-Three, P-Four, S-Four, P-Five, S-Five. Well, S-Zero being in the middle, I guess they couldn't decide whether to call it S-Zero or P-Zero, and maybe they flipped a coin or whatever else and decided to call it S-Zero, but it's actually in the center, it's not on the starboard side or the port side, so it could have just as easily been named P-Zero.
Chary from the Philippines
Does the International Space Station have any hardware or machines that were specifically invented for it and cannot be found anywhere else? What are they?
Well, the International Space Station has lots of unique hardware elements that were designed specifically for the International Space Station. They also use off-the-shelf technology when possible; one instance of that is the cameras that they use on the space station for the interior of the space station are actually just off-the-shelf camcorders. But, some, there's certainly a great amount of technology that was developed specifically for the International Space Station to function specifically in the space environment. I think one of the best examples of that is the Canadian robotic arm. The Canadian robotic arm was developed specifically for the International Space Station and fills the task of actually constructing the International Space Station, and it doesn't even function in the Earth environment in the one-G conditions that we have here on Earth.
Sandeep from Kuala Lumpur
When will the International Space Station be completed?
Well also that's a very interesting question. The core complete milestone that we are reaching for right now is due in the mid-2004 timeframe. Now, after we finish building what's essentially the core of the International Space Station then we have a lot of additional options to add elements developed by international partners, and other additional features that we might want to add. The fact that the space station was designed the way it was allows us to once we get to the core complete milestone to expand it to provide lots of additional capabilities.
Bernardo from Mexico City
Which ISS docking port is being used by the Soyuz TM-34 spacecraft? Also, where on the station will Endeavour and Leonardo dock?
Well, the Soyuz module is nominally docked to the end of the Russian service module. Now, there are additional docking ports on the Russian functional cargo block, I'm sorry, on the bottom of the service module, where the Soyuz modules can be docked. And when they bring a second one up onto orbit in order to switch out the first one when they have to replace them, they actually have to move one of the Soyuz modules from the end of the service module to the bottom of the service module, and the second service module goes on to the end. The space shuttle, on the other hand, docks to the American side of the space station, to the Destiny laboratory. And the MPLM, Leonardo, in this case, is docked to Node-1, which was also built by an American company, Boeing.
Raymond from Fresno, California
Is it possible to give the times and locations of when the ISS passes over Central California?
Well, it's actually possible to find out when the space station will be passing over your head no matter where you live, and there's a website, it's, and if you go that website, you can follow links and actually no matter what city you are in the country, you can find out when the space station will be traveling overhead.
Mike from Mt. Dora
With respect to the space station, why can't we just shoot the trash off towards the sun instead of bringing it back to Earth?
Well, that's actually a question that I used to wonder about when I was growing up, why didn't we just put all the trash into the sun to save our garbage problems here on Earth. Unfortunately, it would take a lot of rocket power to get anything to the Sun, and so it's sort of a limiting factor to be able to launch something out the sphere of influence of the Earth. Now, the trash on the International Space Station, not all of it is brought back to Earth. Some of it is placed in the Russian Progress modules, which are sent on a trajectory into the Earth's atmosphere that burns it back up. So it's not all brought back to Earth, just some of it in the MPLM modules.
Ryan Voll from Red Deer
After the completion of the ISS, how much will it contribute to the flight of humans to Mars, and return trips to the Moon?
Well, this kind of goes with the earlier question, about what the benefits of the International Space Station are. If we're going to go to Mars, or spend long periods of time on the Moon, we have to learn what the effects of long term space flight is going to be on our astronauts. We don't have a lot of information about what the space environment does to our astronauts, beyond, say six months. There are astronauts, particularly from Russia, who have spend more time than that in space, but very few, so we don't have a large amount of data, and it'd be very risky to send astronauts to Mars, to spend say, a year and a half outside of the Earth environment, or more, without knowing exactly what the effects of the long term exposure to space would be. So, the International Space Station in addition to us just developing the technology to live in space for large amounts of time, it gives us the information that we need about how long astronauts can safely stay in space.
Daniel from Zenon Park
Is it possible to use a flywheel mechanism to produce power for the space station? Have there been any experiments using this technology to produce power in space?
Well, it's actually not possible to use flywheels to generate power in the classical sense, but you can use flywheels to store power. So, you would have to use some other source to generate the power, but then to store it you could spin up flywheels and then use the kinetic energy from the flywheels to actually store energy. But because the power requirements of the space station are so large, it's a lot more practical for us to use batteries to store power on the station. So, the answer to the question is no, we don't use flywheels to store power.
Taylor from Colorado Springs
How many different civilian contracting companies, on average, participate in the building of one of our space station modules?
Well, most of the American space station modules were developed and built by the prime contractor for the space station, which is Boeing. Now, Boeing has dozens, if not hundreds of subcontractors that it uses to build everything from the smallest screw used on the space station to a complex computer, or a solar array. So, there's one prime contractor, but dozens, if not hundreds of subcontractors.
Butch from Rochester Hills
When the space station needs to make an orbital adjustment, do the occupants of the space station feel the movement of the adjustment?
Well, the reason why I think that's such a good question is because it really highlights one of the most fundamental laws of physics we have, and there are basically three laws of physics that Isaac Newton postulated hundreds of years ago, and one of those laws it that force equals mass times acceleration. Now, the key thing about these laws is that no matter where you are in the universe, they are true. So whether you're on Earth or whether you're in space, these laws are true. Now, this particular law, force equals mass plus acceleration, when you press the gas pedal in your car, your car accelerates, you go from say, 55 miles an hour to 60 miles an hour. That acceleration is what causes you to feel that force. Now, in space, when they fire the thrusters on the space station, the space station also accelerates. But the acceleration is generally very, very small. So sometimes the astronauts might not notice the space station is accelerating. But that also brings in another interesting point, in what they might see, since the astronauts are floating free with respect to the space station, that when the space station fires it thrusters, the space station would move, and the astronauts, not touching one of the surfaces, would not move, so they would see the space station actually moving around them.
Joey from Australia
During a 24 hour period, how many times does the ISS orbit the Earth?
Well, the space station orbits Earth about every 90 minutes, so that means in a 24 hour day, the space station orbits approximately 16 times.
Matt from Columbia
In operating, maintaining, and troubleshooting problems on the ISS, how involved does the ISS crew get versus the control center team?
Well, that's a very good question. NASA has an entire army of people supporting the operations of the International Space Station. Of course, the astronauts are often the first line of defense, and especially in emergency situations, they have to make quick, critical decisions that will allow everybody to be safe. Now, the mission control people are a huge part of supporting that and laying out those plans for the emergency situations. But, in the event that something goes wrong on the station, NASA has the ability to go back to the people who actually designed the hardware and ask them what they think about the problem, and if it's something they might have seen before in ground testing. So it's a collaborative effort across all of the different countries that make up the hardware that we use on the International Space Station.
Diana from Hilton Head
On certain days we are able to visualize the space station as it seems to streak across the sky. How fast is the ISS traveling?
Well, in order for the space station to stay in orbit, it has to travel at seven kilometers per second, which the equivalent in miles per hour, is around 15,500 miles per hour. So that's pretty fast!
NASA's John F. Kennedy Space Center