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What is a reusable launch vehicle or RLV?

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Why do spacecraft need to be lightweight?

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How is the RLV protected during re-entry?

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Those are some good questions.

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Now, let's get some answers from Kathy Kynard.

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She's an engineer here at NASA Marshall.

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Kathy, what are some of NASA's design challenges for the next generation of spacecraft?

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Jennifer, we have a great bunch of talented folks from around the country

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helping us choose the best design.

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Some work for the government, some work for private companies, and others for universities.

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SLI is designing the whole system for the next generation of reusable launch vehicles.

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Okay, we keep saying next generation.

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What was the first generation?

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Good question.

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The Space Shuttle is the world's first reusable launch vehicle.

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The Space Shuttle orbiter is designed to be launched again and again,

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and is our first generation of reusable launch vehicles, or RLV.

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And that's why we talk about the next-gen RLV.

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So, what are some of the things you're doing to get ready for the replacement of the Space Shuttle?

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Well, the most important thing is safety.

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The challenge is to make the vehicle as light as possible without reducing safety or strength.

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Yeah, that's understandable.

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So, I guess being lightweight isn't the only thing that matters.

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That's right. A part of the system might actually be heavier

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if, say, it made the whole system safer or less expensive to operate.

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The weight increase might reduce costs and help make the crew travel safer.

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We definitely want to keep space travel routine and safe for those next-generation space explorers.

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There are many things for the SLI program to consider and test.

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Different types of engines, fuels, and vehicle shapes,

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and these are only some of the parts of the entire system.

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We call the whole system the architecture,

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and we mean everything from mission planning to launch on orbit support

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to landing and getting the vehicle ready to fly again.

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Kathy, that sounds pretty challenging.

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Well, so have you come up with any designs yet?

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First, we had to decide what we wanted to do in space before we started designing.

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NASA sees the next-generation RLV as doing two main things,

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getting to the International Space Station and taking satellites into orbit.

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We select preliminary designs that best meet our needs.

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One challenge vehicle designers face is what type of engine to use.

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Some engines use kerosene and liquid oxygen.

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Others may use liquid hydrogen and liquid oxygen.

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Each option offers advantages.

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Well, why so much interest in engines?

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The type and performance of the main engines have a major influence on the whole spacecraft.

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They influence safety, weight, maintenance, preparation time, and cost.

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So what are some of the other things we can look for in the next-generation RLV?

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Well, one of the things that you might see are the reusable boosters that fly back to the launch site.

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A booster? What's that?

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A booster is the primary or first stage of a multistage rocket.

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Okay, that makes sense, but you said the boosters are going to fly back.

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How do they do that?

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Well, they have onboard computers for navigation,

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and they also have onboard computers that work sort of like your nervous system,

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alerting astronauts and people on the ground whenever there's any kind of problem.

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Right, that's really important.

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Besides the onboard computer systems, how else are you going to improve safety?

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Well, when a spacecraft goes from space to our atmosphere,

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friction with the air can heat up the outside of the vehicle to temperatures over 1,600 degrees centigrade.

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That's hot enough to melt steel.

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The part of the vehicle that protects the crew is called the thermal protection system, or TPS.

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So what is the thermal protection system made of, and how does it work?

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Currently, we are looking at a number of materials,

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and thermal protection systems work in two basic ways.

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The first way is absorption.

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Like a potholder, you design the skin of the spacecraft

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so that it can absorb the heat of reentry without damaging the vehicle.

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The second way is radiation.

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The outside of the vehicle is designed to radiate the heat from reentry

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like a fireman's coat protects him from a fire.

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Some designs will combine both of these approaches

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to protect the astronauts and spacecraft from the heat of reentry.

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The TPS has to be thin and light, but still strong enough to do the job over and over again.

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Kathy, that sounds difficult.

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Well, it is challenging, but remember, crew safety, it's our number one concern.

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For the next generation spacecraft system, we'll have other changes, too.

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What sort of changes?

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Well, for instance, the space shuttle carries both cargo and astronauts.

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For the next generation RLV, we want to divide those jobs.

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We are looking at two vehicles,

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a cargo ship with no crew on board and a smaller crew transport vehicle.

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Protecting the crew is much easier when they are not part of a huge cargo vehicle.

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The crew transport vehicle has a rocket engine to help it get away from the launch vehicle

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in case of any problems.

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The cargo vehicle doesn't need all the equipment required to protect people,

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so it can carry more cargo.

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It's really a win-win situation.

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That's super, Kathy.

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Thank you so much for all the information on the Space Launch Initiative.

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Now, before we move on, it's time for a cue card review.

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If you're watching the show on videotape, pause the tape now and discuss these questions.

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What is a reusable launch vehicle, or RLV?

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Why do spacecraft need to be lightweight?

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How is the RLV protected during reentry?