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STS-112 Space Shuttle
 
Question and Answer Board

Everett from Altanta
After a flight, are all of the engines removed and rebuilt or simply inspected?
That is a good question, Everett. Yes, every flight we take out all three main engines and we have a special shop where we take them. They are not automatically rebuilt usually after a certain number of flights. Generally speaking we take them out and do a lot of inspections and replace some of the components because they have a certain amount of time on them. So we replace them, but those aren't the lion's share. Most of the stuff we take off is something we've had a little bit of a problem with. So you are right after every flight we take them out, bring them to the shop for a whole bunch of inspections and replace them.
Erin from Ann Arbor
How is the orbiter able to stay attached to the ET while sitting on the ground with so few points of contact?
I guess that might be a little bit of a mystery to the folks out there. There are three points in which the orbiter is attached to the external tank. One of them is at the nose; two are down by the engine compartment. They are actually quite small bolts, very strong and specially built and obviously very expensive. These bolts have explosives in them so at the right time about eight minutes and 30 seconds into the flight after the main engines have shut down and the external tank is empty, we blow these bolts and they separate.
Sauli from Helsinki
During shuttle maintenance and processing the shuttle is lifted by a huge lifting system. How does this lifting system work? How can it get a firm hold of the shuttle so it won't fall down or damage any parts of the shuttle (such as the heat tiles)?
As you can imagine that is something we are concerned about. When we bring the orbiter over to the Vehicle Assembly Building we attach it to this huge lifting device, the lifting frame we call it, and we use two overhead cranes, which have the capacity of 250-300 tons of lifting each. One is attached to the fore of the orbiter and one is attached to the aft of the orbiter. These attach points are obviously structural attachments that were designed when we built the orbiter, two in the front and two in the back. We take the orbiter from horizontal up to vertical. Once that is done we can detach the back two. Then we use just one crane and then attach to the external tank in the three locations that I was telling you about.
Shane from Mitchell
How long does it take to build the ET and where do you get all that metal?
It's a long and involved process involving a lot of machining. There are these huge, what we call inglets that are brought in from manufacturer. And they are not just plain aluminum, they're a special aluminum called aluminum-lithium which is lighter. When we first started flying external tanks they weighed as much as 70,000 pounds and by using aluminum-lithium they got that weigh down to 57,000 pounds for the external tank. There's a plant near New Orleans, Louisiana and it takes months, literally, to make each of the sections and that have to be welded together. Each time there is a weld there's are a whole lot of inspections. Then we stack up the weldings, and eventually we have it all added up to a bare aluminum External Tank. Then we have to add foam to the outside, and that is another process that takes a long time. It takes months and months; we can't just call up and order one for next week.
Grady from Cincinnati
What is the escape velocity required for a space shuttle, and how much fuel does this require?
Escape velocity is a term we use when we want to escape from the Earth's gravity. Well, we are not actually escaping from Earth's gravity. We re actually going into what is called the gravity realm. So we don't actually achieve escape velocity. That would actually be if were going at least 25,000 miles per hour. For our purpose, we go into a low Earth orbit we need about 17,500 miles per hour. So that is what we have to do is go from a standing start up to an altitude of about 80 miles and get going to about 17,500 mph and to do that it takes half of million gallons of liquid hydrogen and liquid oxygen.
Duane from Bend
Would you explain the advantages of the cam on the fuel tank? Are there anomalies associated with the launch or the tank separation?
There are no anomalies associated with the launch. This is strictly for Public Relations purposes. And to be honest, I am as excited as the rest of you to see this view. I really want to see this myself. It will be the first movie ever from that location. And I think it is going to be pretty spectacular. So no there are no anomalies with the launch. We are curious and we think it will look pretty cool!.
Steve & Karen from Fairbanks
We read about the cam that will be on the exterior of Atlantis for launch. Will it also be broadcast live on the web? Will there be a video feature for those of us 4 hours behind KSC?
It will be broadcast live from the web and also can be viewed after launch in the archives at: http://www.nasa.gov/missions/highlights/ndirect_shuttle-archive.html
Alessio from Maglie
What temperatures does the water reach that is released during the launch? And does the water become vapor?
Absolutely it becomes vapor. The main engines on the orbiter use liquid oxygen and liquid hydrogen and when you put those two together you get water. In this case it is very hot water so it steams. What you see coming out of the back of the orbiter is essentially water at a very high temperature and at a high speed. The water we use underneath to cool the pad as well as to deaden the noise from the engines, that is going to get super heated as well. What you see is a lot of steam coming out of the exhaust ducts.
Prashannajeet from Bhopal
Why does the space shuttle start rotating just after the launch?
Aah, very good question! The reason we do that it is because the launch was built in orientation for taking the shuttle out to the pad. We could have designed the pad so it didn't have to rotate but it was much simpler and would of cost a whole lot of money. The reason we do that rotation is because we want to get the orbiter in the right plane. When we lift-off we are almost at a north/south and we want to rotate about 90 degrees and end up northeast in order to line up with the launch pad. We do that for stability of the vehicle, so the whole stack is on the bottom making it more stable and plus when the astronauts look out their window, since we are upside-down the astronauts can see the horizon of the Earth and in some kind of emergency that requires them to take action and fly the orbiter away from the shuttle stack they would have a visual cue of their orientation making it much safer for them.
Caitlin from Michigan City
Is it possible for the shuttle to make a return trip to Mars? If not, what are the limiting factors?
I wish we were, Caitlin. We are not making them right now, we are thinking about them. In order to make a shuttle go faster and farther and further, it would take a lot of design work. We have people who are working on it, thinking about those sorts of things right now, but not actively involved in the construction of a spacecraft that would be better than the shuttle. We can fly the shuttles for at least another ten years, which will give us plenty of time to decide on what we can improve upon, what can we make better, what areas of technology can we advance in so we can make it better, faster, cheaper those sort of things.
Danielle from Chicago
Are you making a shuttle that will be able to get to Pluto with people in it?
Unfortunately, no we are building any Pluto capable vehicles that will carry humans right now. We are looking at designing crafts that will go in low Earth orbit. And the plan right now as I understand it, is we will build something in the low Earth orbit that gets out of this deep gravity that won't use up 90% of fuel just to get out of the Earth's gravity. We will build the spacecraft that will leave low Earth's orbit up in space so it can take off to the Moon, Mars, Pluto or wherever we want to go.
Danielle from Lagrange
If there were any malfunctions aboard the shuttle while in space what would you do?
That is always a very good question. We spend an awful lot of time looking at whatever the failure modes might be. In fact, we have these huge documents that would take up many bookcases that tell us what to do in an event of a catastrophe, a problem or an anomaly, that we could plan on. There are folks out there in Houston during a fantastic job going through and deciding what if this failed or what if this failed. Or what if this box didn't work or what if it didn't work in this way, and they go through and try to analyze and they have a whole bunch of preplanned procedures so that we know what to do. Those involve coming back early, or they might stay up longer. Depending upon how bad the failure is we might be able to finish the whole mission or there might be a situation where they have to come home early. It runs the whole gamut of possibilities. So I can't give a single answer there is a whole range of possiblities and we are looking at them all the time.
Travis from Prineville
Is there a plan for the shuttle if there was a problem during landing and couldn't re-enter Earth's atmosphere?
That would be very bad. The way we designed the orbiter was such that any of what we a call a criticality-run system -- one where if it did not work the astronauts could be killed -- we designed it so that there are back-ups and we have over designed them so we feel there is no possible way it could fail. We go to great lengths during the design phase to make sure the astronauts would be safe. You cannot believe the expenditure of time and money to prevent these very things from happening.
Butch from Rochester Hills
From looking at the KSC Video Feeds, it looks like the cargo bay is removed form the shuttle and another cargo bay is put in its place for the next launch. Is this correct?
As a matter of fact no, it's not possible. We do not remove the cargo bay. What you see is a device called a canister and it does look exactly, to the untrained eye, like the orbiter's payload bay. What we do is insert the payload into the canister, take it out to the pad, lift it up and join it up to the orbiter's payload bay and insert the payload, but the canister never goes into the orbiter -- it's just the payload itself that goes in.
Miguel from Madrid
From what countries can I see the space shuttle when it detaches and goes into orbit?
Just about every country with the possible exception of Antarctica. You can go to many of NASA's Web sites and it will tell you where to look. And usually right before dawn or just after dusk is the best time to see it. If you go these Web sites they will tell you what time to go outside, where to look, and how it will appear to you. I don't think there are countries anywhere in the world where you can't watch the shuttle or the space station go over, except maybe down in the South Pole.
Alexandria from Orlando
How long does it take for the orbiter to get in to orbit?
Very good question, it only takes eight and half minutes. It's quite a wild ride when you consider that they have to go from that standing start to 17,500 mile per hour. In the initial acceleration, right off the launch pad going straight up it's faster than a Corvette, I do believe. And the amazing thing is that the whole shuttle stack weighs about four and half million pounds, not just 3,000 pounds like a Corvette.
Norman from Ireland
How safe is the shuttle after the recent cracks were found in the main engines, is she ready to fly with confidence?
Absolutely, she is. A very alert inspector found the cracks, we deeply appreciate his effort. These cracks were found in the flow lines of the main propulsion system so we have taken a great deal of care and a great deal of time to go through and verify a technique to repair these cracks. We only found three cracks and they are very small. The biggest crack we found was only something on the order of three-quarters of an inch long. We are very careful, these are critical systems so we needed to be extremely careful. So first we validated our repair technique, then we practiced our repair technique, validated the practice. We have some of the best minds working. Then we went through and did the repair and now we're ready to go flying.
Mark from Christchurch
Is it possible to modify the shuttle for a lunar mission? If not, could NASA get back to the moon? Does NASA have plans if the money was not a problem?
Sadly, it cannot be modified to take us on a lunar mission. It would take more fuel than we can carry up on the orbiter. Only Apollo was designed to do that and the orbiter is not designed to do that. There are really no plans for us do that, but we are looking for a new vehicle design to build up in orbit and then take it to the Moon.
 
 
NASA's John F. Kennedy Space Center