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Exploration Through Navigation Challenge
Welcome to the Winter 2009 NASA Quest Challenge Webcast

Exploration through Navigation logo

February 25, 2009 Opening Webcast Archive
Exploration through Navigation Challenge
Charting a Course to the Moon

Featured in this webcast students were Astronomer Brian Day and Science Journalist and Space Historian Andrew Chaikin, author of A Man on the Moon: The Voyages of the Apollo Astronauts. During the live Questions and Answers time, students requested more information to help in their challenge projects.

Ask your Questions
Use the chat room on the right:
Please include in your user name (no last name) something about where you are, or your teacher's name.
For Example:

>> Hello and welcome to part II of the NASA Quest challenge.

This is part two of our Challenge.

We're focusing on charting a course to the Moon in this section.

Let's recap the fall challenge, part I.

We have a few slides that we're going to show you to recap that challenge for those of you who participated.

To begin with, the task at hand was charting a course from the big island of Hawaii to Rapa Nuiy or Easter island.

About a 5,000 mile trip.

For many of you who participated in our challenge you got to hear from our expert navigator who came to us from Hawaii and shared with you his knowledge of ancient Polynesian navigation.

In this particular challenge we have another slide coming to you.

In this particular challenge we explored aspects such as ocean currents and seasonal weather.

That includes tropical storms such as typhoons in both the southern and northern hemisphere.

We looked at the currents and how they change with latitude.

We also explored sea marks and landmarks and how those can be useful for ocean navigation so there is the white turn that you see pictured in the middle of the screen and that's a very important bird that relates to signs of being near your target island.

We also have features such as age holes and reefs that can be helpful in ocean navigation and we also have weather patterns such as prevailing winds, cloud formations and then the seasonal weather like we mentioned before such as typhoons and hurricanes.

But more importantly, we learned about directional navigation.

That will tie in to our challenge that we're beginning this spring.

In celestial navigation you can use objects in our solar system such as the Moon, the Sun, the stars and even the planets to help guide you.

Recognizing key stars at night and understanding there alignment with the star compass is very important and useful to both navigation here on Earth and in space.

As you see pictured in the lower right corner of the screen, that's a picture of the star compass which many of you may be familiar with if you participated in the challenge.

It's being able to chart the movement of the stars and being able to orient yourself in regard to the heavens above.

So that's a recap of what we learned last fall.

But let's move on to part II of our challenge, which is going to be focusing on space navigation.

So we'll take our newly learned navigation from the fall and we'll go a step further and apply them to the environment of outer space.

There are a few commonalities between navigating on our home planet and navigating in outer space but the two environments are drastically different.

I'm Rebecca Greene, I'm coming to you from NASA Ames Research Center here at Moffet Field in northern California.

And we have several people joining us today to help with this webcast.

First we have Linda Conrad, she is the Challenge coordinator and the person guiding you along with eight-week process of making a navigation plan in outer space.

Today her role will be to field your questions that you may have as this chat continues.

So be sure and submit those questions as soon as you think of them.

Don't save them until the end because we want to make sure that we see your questions and that we have time to answer them.

So as things come to mind submit them to the chatroom and Linda will pass those on to us.

We also have Brian Day.

He's joining us today via video.

In that video presentation he'll tell you all about the LCROSS mission.

Finally we have Andrew with us here live and in person.

Andy is an author, a science journalist and space historian and energeticly passionate about space exploration.

We're grateful to have Andy with us today.

While he's here when it comes time for his segment of the webcast he'll tell us about the space environment and how it's different than flight here in our own atmosphere.

With that said, let's give Andy a chance to say a few words.


>> Well, it's very exciting to talk about our going back to the Moon and LCROSS is one of the first major steps in going back to the Moon.

I'm excited to be here today to connect with the students and because they are the ones who are going to carry exploration forward in the future and we want to get all of them pumped up and excited and ready for those challenges.

And first we're going to hear from Brian, Brian Day, who is going to tell us about the LCROSS mission, which is really the first step in the new exploration of the Moon and we're going to learn from Brian about what the LCROSS mission is all about.


>> I'm the education and public outreach lead for NASA's LCROSS mission.

Today we'll do a brief overview of the mission and see what it is going to accomplish.

The good news is we're returning to the Moon.

The plan is to have people living in a human outpost on the Moon in the 2020s.

We'll have robotic and manned mission going to the Moon in the next few years.

The lunar host is envisioned.

Where will it be?

If you look at the Moon you can see our previous landing spots have all been clustered on the near side of the Moon and more or less near the equator.

It's not because it's the most interesting place to be, it's because it's the easiest place to go.

In choosing our site for our lunar outposts we have several considerations.

One is the general accessibility of the site.

How easy is it to get to?

Another is landing site safety.

You don't want a big Boulder field to try to land in.

Another is mobility.

We probably won't find everything that is interesting right there in one place.

We have to be able to get into our lunar car and drive around.

Another is having this be analog.

One of our primary reasons for going back to the Moon is to develop the technologies and techniques that we're going to need to live on Mars.

Another consideration is power.

You have to keep in mind that on the Moon, most places have two weeks of daylight followed by two weeks of dark.

That two weeks of dark can be a real problem in terms of power.

You either have to carry a lot of really big batteries with you, which are really, really heavy, or you carry some sort of a nuclear powered generator which is also really heavy.

There are certain areas on the Moon where you get much closer to constant sunlight and therefore from a power standpoint, those would be very favorable.

Communication is also another important issue.

It's a lot easier to communicate with the Earth from the near side of the Moon than on the far side.

Geologic diversity.

We want to make sure the place we go is actually scientifically interesting.

And finally, I have here highlighted, it says INRU considerations.

Just what does that mean?

That means being able to live off the land, to use resources that are there on the Moon already rather than having to bring everything with you.

One of the really important resources that we will need to have for people living on the Moon is water.

There are a couple of options.

We can carry the water with us all the way there, but that's pretty heavy.

Water is heavy and it is expensive to transport water from the Earth to the Moon.

Costs about $100,000 per gallon.

Now, it would be nice if we could actually find water on the Moon.

But one thing we know from our experiences with the Apollo missions is that the samples that came back from Apollo were really dry, very dry.

Very little moisture, if any, on the surface of the Moon.

The Moon is dryer than many of the meteorites we get from deep space.

Now that doesn't mean we're completely out of luck.

There is oxygen within a lot of the minerals that you find on the Moon and there is hydrogen coming down in the form of the solar wind.

So you could manufacture your own water on the Moon from the native elements.

But that requires a whole lot of energy.

To get that oxygen and hydrogen out of the lunar you have to heat the rocks to 700 degrees.

It's energy intensive.

Life would be a lot easier if we could just find water on the Moon.

And it just might be there in certain places.

A couple of previous robotic missions to the Moon gave us hints that at the poles of the Moon there might be water ice.

Back in 1994, the Clementine probe was bouncing radar signals off the surface of the Moon.

And in the vicinity of the lunar pole, when those radar signals bounced off the surface, they reflected in a peculiar way that was indicating that they might be bouncing off crystals of water ice.

Now, some people, when they look at that data say look there is water ice.

Other people look at the same data and say we think something else could have caused it.

Another interesting piece of information came from another probe, lunar prospector.

This was in 1999.

And lunar prospector had a neutron spectrometer to detect hydrogen.

It found hydrogen was concentrated at the poles of the Moon.

We don't think that's elemental hydrogen.

That wouldn't remain on the Moon very long.

It would float into space.

Scientists think it's probably the form of some compound, one of the most likely compounds is H2O or water.

To test it out at the end of lunar prospector's mission it was de-orbited in such a way it would crash into the south polar of the Moon.

The plan was to see if there were any signs of water ice.

The problem is that lunar prospector came in at a shallow angle.

6.3 degrees and lunar prospector didn't weigh very much and it wasn't moving very fast.

The plume it created wasn't very big and so we really didn't get any conclusive answers.

It was a neat idea.

So if we're going to look for water ice on the Moon, just where do we look?

The answer is in these craters very near the poles.

There are craters near the poles of the Moon where the floor of those craters is permanently shadowed.

The Sun never shines there.

As a result, these craters are very, very cold.

Over 200 degrees below zero.

They've been that way for billions of years.

As come either and meteorites strike the surface of the Moon, the Moon will have a very tenuous, thin atmosphere that will escape into space.

Any of that atmosphere that gets into the cold, dark craters will encounter what we call a cold trap and any water vapor that might be in that atmosphere would condense and might form deposits of water ice.

Over time, for billions of years, you might be able to accumulate a fair amount of water ice.

So how do we go about looking for water?

Well, we're going to do it with two robotic space probes, the lunar reconnaissance orbiter and the LCROSS.

We'll talk about LRO first.

The lunar reconnaissance orbiter is going to go into orbit around the Moon and map the Moon in finer detail than we've ever done before.

As a matter of fact your coffee table were on the surface of the Moon, LRO would probably be able to see it.

It's pretty fantastic.

In addition to mapping the Moon with this beautiful photographic camera it will also look at the temperature environment on the Moon.

What the the highs and lows and the radiation environment on the Moon.

These are all things that we'll really want to know before we have people living on the surface of the Moon.

So the plan for LRO is that it will use its own propulsion system to enter into a circular orbit around the Moon going around the north and south pole at about 50 kilometers high.

From this for one year it will map the surface of the Moon for what we call the Exploration Systems Mission director, the people who are planning our future presence on the Moon.

After that one-year mission it will be turned over to the science mission director at NASA who will use it to do lunar science and the history of the Moon's surface and how it came to be the way it is.

LCROSS is a very different concept.

LCROSS is going to take the upper stage of our Moon rocket and LRO and LCROSS will share the same Moon rocket.

LCROSS will take that upper stage and it will direct it at high speed and at a steep angle toward one of those permanently shadowed craters.

That centaur upper stage is going to hit at 2.5 kilometers per second, 5600 miles-per-hour.

When it hits the floor of that crater, it will create a huge plume of debris arching 10 kilometers or so into the Moon's sky and we'll analyze that debris to see if, in fact, there is any water ice in there and if so, how much.

When the centaur, this upper stage of the Moon rocket hits, it will create a crater about 20 to 25 meters across.

And about 3 to 5 meters deep.

This will result in a minimum of 200 metric tons of material being flung into the sky.

Sounds like a pretty big crater but in reality it's not.

There are features on the Moon that are over 1,000 kilometers in diameter.

So 20 meters is pretty small in comparison.

The LCROSS system consists of two main components.

You have the centaur upper stage of our Moon rocket, which again that has takes us out of Earth orbit and propels us toward the Moon.

And then later on we'll use that empty upper stage as our impactor and we also have the shepherding spacecraft.

This is what guides and targets that upper stage toward its target crater and it also carries the scientific instrumentation on board to measure and analyze the plume we create.

There is a range of instrumentation on board.

We have cameras and spectrometers working in the invisible and infrared wavelengths.

They're both scheduled to launch together in the spring of 2009.

They'll launch aboard an Atlas 5 rocket flying out of cape Canaveral in Florida.

As they climb out of the Earth's atmosphere they'll get rid of the lower stage of the Atlas 5 rocket and it will fall back to Earth in the ocean.

We'll climb through Earth orbit.

After being there a very brief time, fire the engine of the centaur.

The centaur will take LRO and LCROSS out of Earth orbit on its way to the Moon.

Two hours after launch LRO separates and take its own path to the Moon to conduct its mission.

Five days after launch, LCROSS, still attached to that centaur upper stage, will do a fly-by of the Moon and will use the Moon's gravity to fling us into a very highly tilted, highly inclined orbit around the entire Earth/Moon system.

Each one of these big loops takes about 38 days.

We call this lunar gravity assist lunar return orbit.

The idea is when we meet up with the Moon again we'll do so so we're coming in at a steep angle relative to the Moon's pole.

About nine hours before the end of the mission the shepherding spacecraft will separate from the centaur.

It will fire its thrusters to pull away so it's following four minutes behind the centaur.

The centaur again is going to hit this permanently-shadowed crater at about 5600 miles-per-hour creating this huge plume of debris.

LCROSS is going to be perfectly situated to be able to look down and see that impact.

Over the next four minutes, the LCROSS shepherding spacecraft will actually fly down through the plume of debris sampling it and letting us know what it's made of.

Is there any water and if so, how much?

Four minutes after the centaur hits, the LCROSS shepherding spacecraft will also hit creating a second plume of debris.

That plume of debris, both plumes of debris will be observed from the surface of the Earth through some of the greatest telescopes on the Earth, from telescopes in Earth orbit such as possibly the Hubble space telescope and from instruments in orbit around the Moon such as the lunar reconnaissance orbiter.

We're planning the ground-based observations using the great observatories of the world to be centered around the great telescopes in Hawaii up on top of mountain with some of the best viewing conditions in the world.

We think amateur astronomers will also be able to get very good views of the LCROSS impact.

So we're encouraging amateur astronomers to take images and share these images with us.

Because these could be very valuable for us scientifically.

We're also looking to have the amateur astronomers track the spacecraft during those big looping orbits.

To image the spacecraft as it flies on its way in the mission.

The question, is that really possible with amateur backyard telescopes?

The answer is yes.

We learned that very dramatically back in 2002.

Then an amateur astronomer discovered what appeared to be an asteroid.

The asteroid was interesting because it was coming close to the Earth and Moon.

But that orbit was an unstable one and so eventually it got shot out of the system and started receding off into space.

The whole time amateur astronomers were imaging it, tracking it and measuring it's position.

Someone suddenly realized that could be the upper stage, the S4B stage from Apollo 12 way back when.

That was lost into solar orbit a long time ago.

Pretty neat.

Again, the amateur astronomers really demonstrated what they're capable of.

What is it we're expecting to see?

Well, on a time frame of just the first few seconds, there will be this thermal flash, this real bright flash caused by the heat generated when the centaur hits the surface.

Over the next minute or so the plume will expand high into the Moon's sky.

It will arch up to the point where it's out of the shadow of the crater and it will be illuminateed by the sunlight.

That's when we're hoping everybody will be able to start catching images.

For a number of hours after that there will be a thin cloud of gas, we think possibly OH, oxygen and hydrogen bound together and it could be expanding for hours but it will be something observed by the big telescopes of the world.

How do we guesstimate what this impact is going to be like?

After all we've never really done this before.

But we've done tests.

Here at Ames we have something called the vertical gun range.

This is a big cannon that shoots hyper velocity project tiles into a chamber.

Timing is everything in the LCROSS mission.

The fact this is happening in 2009 corresponds with the international year of astronomy.

Some 400 years ago, Galileo was pointing his telescope up into the sky and discovering the rings of Saturn and looking at this really interesting terrain of the Moon.

It also corresponds with the International Polar Year.

The International Polar Year is an effort where countries around the world gather to study the science of what is happening at the poles.

NASA is a big participant in this.

The International Polar Year consists of six poles according to NASA, two on the Earth, two on Mars, and two on the Moon.

We'll have one of the Moon's poles pretty well covered here.

It also corresponds with the 50th anniversary of NASA.

Kind of an appropriate time to be heading back to the Moon.


>> We want to thank Brian for that nice presentation in explaining the LCROSS mission.

As you can see, there are many ways to be involved in the mission, whether it's looking at a telescope in your own backyard or participating in this Quest Challenge.

Well aboard as you're official participants in the LCROSS mission.

Andy, you have researched and written a lot about the Apollo missions and you've even spoken to the men who have flown those Apollo spacecraft.

Tell us about the missions and how the environment of space is so different than the environment here on Earth and how traveling in space is different.


>> Got it.


So the thing about Apollo, LCROSS is really in a sense beginning this new phase of lunar exploration where Apollo left off.

And nobody has been to the Moon since 1972.

But I spent eight years talking to the men who went to the Moon and the men who made the Apollo program, the men and women who made the Apollo program happen and I wrote a book called "the man on the Moon."

I looked at the human experience as well as the technology and learned a lot about that.

One of the things you have to know about when you talk about going to the Moon is that it's very different to fly in space than it is to fly on the Earth.

And one of the things that you need to think about is something called inertia.

And so inertia is the property that objects have that says if an object is moving, it's tendency is to keep moving unless acted on by an external force.

If an object is at rest its tendency is to remain at rest unless acted on by an external force.

If I push on it, it goes somewhere.

If I let it sit there, it stays.

Now, the difference is that here on the Earth, if I push on something, notice that the bottle did not keep moving until it fell off the table.

It stopped.


Because there is friction with the surface of the table.

In space, there is no friction at all.

There is no air and things are not rubbing up against each other because of gravity.

They're floating.

And so you push on something in space, it will keep going indefinitely.

So we're about to see in a second I'm going to show you a little video of a computer graphic representation of the early part of an Apollo mission and you'll see two things.

You'll see some panels that get cast off because they're no longer needed and they tumble and keep going because of inertia because there is nothing to stop them.

There is no friction or anything like that.

But the spacecraft which separates from its rocket booster has little engines that it can use to control its motion.

So it doesn't have to keep going when it doesn't want to.

When I say it keeps moving unless acted on by an external force, in this case the external force comes from this rocket engine.

Let's look at the video.

We're going to see the very beginning of an Apollo mission.

There is the third stage of the Saturn 5 rocket speeding away from the Earth.

It is getting to 25,000 mile-per-hour.

The spacecraft is separating with the astronauts.

Look at the panels go tumbling away.

They keep going out into space.

The spacecraft that the astronauts are flying has these little maneuvering rockets around it so they can turn around, come back and grab their lunar lander.

They dock with the lander, separate and head out onto the Moon and meanwhile those panels, which have no rocket engines to control them, just keep going into space with inertia leading the way.

Now, let's talk about another aspect of flying in space, which is the fact that when we get on an airplane, of course, we're using the air to control our flight, okay?

So if you look at a jet plane, the jet has engines on the wings that give it power to go forward.

But the way it stays in the air is because the wings themselves create lift, air flows over the wing, creates a partial vacuum which lifts the plane up.

How many of you remember about a month ago there was a very big news story about a jet airliner that took off from New York City and while it was taking off it got hit by some birds.

The birds actually went into the engines of the plane and knocked out the engines.

So at that point the plane had no power at all.

And pilots always have to be ready for the unexpected.

The pilot did a beautiful job of gliding, now, because there was no power, but just using the wings to control the flight of the airplane and actually land in the Hudson River.

Everybody was safe.

He was a big hero, it made big news.

That's our high pressure emergency situation flying on Earth.

Now let's talk about Neil Armstrong and buzz ALDRIN coming down on the Moon.

They were playing in space.

You can't use wings.

The only thing you can use to control your path is your rocket engine and they are in a lunar lander with a big rocket on the bottom.

Because it doesn't fly it just looks like a big mechanical spider.

At the bottom of this spider there are legs sticking out and the astronauts ride up at the top and there is this rocket engine that is balanced on the thrust of that engine.

The only way it changes direction is by tilting and Neil Armstrong had to control his flight to avoid some craters in the final part of that descent to the Moon.

Let's roll the video.

It's an airbus 320.

You can see where the engines are and you can also see some flaps called ailerons that are used to change the way air flows over the wings, tilt the wings and adjust the flight.

Here they're taking off.

They still have power.

Now it's after the bird strike.

They don't have any power at all.

This is real data that was used to make this animation and you can see the pilot, who is trying to control the flight of this plane down to the Hudson river, using just the air, no engine power.

So he's literally piloting a big glider.

He's flying it over this bridge, he knows that he only has one chance because there is no power and he can't fly around and try it again.

Now he's coming into the river.

The important thing is to keep the nose up slightly and just touchdown as gently as possible going very, very fast.

He did a beautiful job.

So now, if we continue with the video, we see the Apollo lunar lander with its descent rocket and the maneuvering thrusters used to change its orientation.

Flies only in the vacuum of space and doesn't look streamlined like an airplane at all.

Here is a computer graphic reconstruction of the very first landing on the Moon.

Again, using real data.

You can see that rocket engine at the bottom is supporting the lander as it comes down.

It is burning and its thrust is keeping them from falling faster than they want.

It's stirring up dust on the surface of the Moon.

It's confusing for Neil Armstrong as he tries to bring it in.

The maneuvering thrusters are trying to keep the orientation of the lander the way they want it.

After hovering for a few seconds he touches down on the Moon.

Probes at the bottom of the legs that signal the time of lunar contact.

He shuts down the engine and Neil and buzz are safely on the Moon.

The date is July 20th, 1969.

What an amazing event that was and I have to say for me as a 13-year-old kid, witnessing that moment was one of the high points of my growing up and I'm really happy for all of you kids that you are going to see future explorations of the Moon and beyond.

Well, once they landed on the Moon, what was it like to actually walk around on the Moon?

We're going to see a video now and it shows how much fun it is to walk around on the Moon where the gravity is only 1/6 of what it is here.

Let's have the video of the astronaut running.

You see two astronauts working in a crater on the Moon and the guy on the right is climbing up out of the crater.

He and his space suit weigh more than 300 pounds on Earth.

On the Moon they only weigh about 50 pounds.

Look at the dust go flying in the low gravity.

Now you'll see how much fun it is.

HIPPITY hop, over the hill.

Da da da.

HIPPITY hopping along.


>> What do you think, does it look like fun?

Would you like to try that?


>> It looks like fun.


>> It's an amazing thing to watch.

I actually had a chance to go in the NASA airplane that they use to train astronauts for weightlessness and lunar gravity.

Walking on the Moon is almost like floating in weightlessness.

It's like somebody had a dimmer switch and turned down the gravity slightly.

Even though he's wearing the heavy equipment how easy it is for him to bounce across the Moon.

There was another demonstration that was done on one of the Apollo missions that shows a very important fact about gravity.

And that is something that Galileo first demonstrated 400 years ago.

We're celebrating the 400th anniversary thisier when Galileo pointed the first telescope at the Moon and it was the beginning of the age of astronomy with telescopes.

He went up to the top of a building called the leaning tower of PISA.

He dropped a pair of balls.

One was made out of wood, one metal and he wanted to find out whether or not they fell at different speeds.

Everybody -- he had people down at the bottom to see when they hit the ground.

Everybody was amazed they hit the ground at exactly the same time.

What that shows you is that the speed of a falling object has nothing to do with the weight of the object.

It only has to do with how strong is the gravity.

So on the Earth, anything you drop will fall at a particular speed and it doesn't matter how heavy it is except for one situation, and that is when you drop something really light and it falls a little slower.

I don't know if you could tell.

The paper falls a little slower than the pen or bottle because of air resistance when you get a light object, the air creates enough resistance to slow down the object.

What if you did that same experiment on the Moon?

One of the astronauts tried it with a hammer and a feather.

Let's see what happened.


>> Watch this.


>> Beautiful picture, Dave.


>> In my left hand I have a feather.

In my right hand a hammer.

I guess one of the reasons we got here today was because of a gentleman named Galileo a long time ago who made a significant discovery about falling objects in gravity fields.

We thought that where would be the better place to confirm his findings than on the Moon?

And so we thought we would try it here for you and the feather happens to be appropriately a falcon feather for our falcon.

And I'll drop the two of them here and hopefully they'll hit the ground at the same time.

How about that?

Mr. Galileo was correct in his findings.


>> Pretty cool, huh?


>> That's great.


>> You can see on the Moon where there is no air at all, no atmosphere, there was no air resistance so the feather fell at exactly the same speed as the hammer.

Now, because they're on the Moon, they didn't fall at the same speed as they would on the Earth because the Moon's gravity is only 1/6 of what it is here.


>> Excellent.


>> Maybe the people who go back to the Moon will find other cool ways to demonstrate lunar gravity.


>> Thank you very much.


As you see there are scientific topics to consider as you think about space travel.

The idea of inertia, laws of motion, low gravity, microgravity environment, frictionless environment and the sort.

Now it's time for our Q and A portion of this webcast.

So we're going to begin answering some of the questions that you've started to submit.

If you haven't submitted a question yet, I'll give you a couple things to think about.

Certainly anything that you learn from Brian's video or from Andy's talk we've just had might have sparked some questions but also when you're thinking about the navigation plan you're going to be creating, remember that the LCROSS spacecraft will actually be impacting the Moon as opposed to landing on it.

There is a difference that you'll need to consider.

And also you can think about just the general motion of objects in our solar system, which include the Sun, the Moon, other planets.

I misspoke earlier about stars.

Certainly those are outside of our solar system.

But as far as the objects in our solar system they're constantly moving and so as you leave our Earth and are headed towards the Moon, keep in mind that it is going to be moving along its orbital path.

It won't stop and wait for us to arrive.


>> You know what?

Before we do the Q and A can I show a picture that I wanted to show everybody?

I forgot that when we talk about flying to the Moon, we are talking about a thing that we call a gravity well.

Can we get that up on the screen?

Is that easy to do?


This is not -- don't look at this picture literally.

This is just a way to think about gravity.

Gravity is like a deep well.

The bigger planet, the stronger its gravity and the deeper the well.

So we have one other picture that shows that the Earth, which has much stronger gravity than the Moon, has a very deep gravity well.

Notice that the size of the well are steeper the closer you get to the Earth.

The Moon's gravity is only 1/6 what it is on Earth so it's like a little dimple in the side of the Earth's gravity well.

In order to fly from the Earth to the Moon you have to fire your rocket to go fast enough to climb out of that gravity well and reach the Moon's gravity well.

That turns out to be a speed of just under 25,000 miles-per-hour.

Now, again, it's not really a physical well.

But it is a way for you to be able to think about how gravity changes as you get farther away from a planet.


>> Excellent.

Great, thank you.


>> I wanted to make sure I got that in?


>> Very important point.

Thank you very much.


>> You're welcome.


>> Linda, what kind of questions do we have so far?


>> They look like questions all over the place.

I'll go right with the one I just got because it relates to the last topics we were talking about.

Why did the hammer and feather land at the same time?


>> Well, that's a very good question.

And you know, I have to say that we don't really understand why gravity works the way it does.

All we can do is investigate how it works.

And when scientists have done calculations, as I say, Galileo went up to the leaning tower of PISA.

You can experiment here on Earth.

Don't use something so light that air resistance slows it down.

If you have a ball made out of -- an object made out of -- I don't know, something like wood or -- then an object made out of something like metal, those are heavy enough they won't be slowed down by air resistance and you can hold them out, drop them, let them go at the same height and same time.

Time after time they will hit the ground at the same moment.

That is because the only thing that affects how fast you fall is the strength of the planet's gravity that you happen to be on at that moment.


>> Okay.

That's great.

Eileen from miss Jameson's class wants to know what type of rockets are best for the trip and what is the best-sized rocket for the trip?


>> Very good question, Eileen.

There are different kinds of rockets.

If you watch the space shuttle take off, for example, you'll see the shuttle itself has three liquid fuel rockets which use hydrogen and oxygen to burn.

Whereas on the side of the shuttle on the external fuel tank are tall, solid rockets which use solid propellants, now, the difference is that you can't turn off a solid rocket once you turn it on.

So in a situation where you need to control when you're firing your rocket and how much thrust you're putting out, liquid fuel rockets are best.

So for the lunar mission to do things like get out of orbit from Earth orbit and head out to the Moon or like we saw in the video, to land on the Moon where you're actually changing the amount of thrust almost like the throttle on a car engine, you need a liquid fuel rocket to take care of that.

Now, there is one other kind of rocket that is an ion propulsion rocket.

What that is, instead of throwing out very hot gases and because of Newton's third law of motion, there is a balloon and you let the air out the air rushes out one end, the balloon goes the other way.

A liquid or solid fuel rocket spew hot gases and that makes the rocket go in the other direction.

An ion engine takes atomic ions.

It takes longer to get going to a fast speed.

If you have a lot of time on your hands and you don't care how long it takes you to get to the Moon, you could use an ion engine once you're in space to get out of low Earth orbit and spiral out to the Moon.

But when you have a lot of thrust at your disposal for things like landing on the Moon or taking off from the Moon or taking off from the Earth, for that matter, you need either a liquid rocket or a solid rocket.

The liquid rockets will be better for things like landing on the Moon.

I hope it wasn't too much information.


>> We don't want to give away the whole challenge, right?


>> That's true, too.


>> But then again, you know, when you're researching it's always good to have some answers.


I have a question here from Romania.

It tickles me they're online at this hour.

Julian wants to know how do you find out how much water is on the Moon so you can say how much hydrogen you can receive from it?


>> That's a really, really good question, Julian.

I have to say, it's also a complicated answer.

We don't know how much water is on the Moon, okay?

We think that there may be frozen water in these permanently shadowed craters at the north and south poles of the Moon.

The whole purpose of the LCROSS mission is to slam into one of those craters and we hope it will kick off a bit of water ice in all of the rock and dust that it blasts out from its impact.

If it does, we'll see that when we fly through the plume of ejected stuff.

Now, so we'll be able to answer your question about that better, much better, after the LCROSS impact.

One point I need to make is that there are other sources of hydrogen on the Moon.

The Moon has no atmosphere and for that reason the Sun is able to -- well, the Sun is always spewing charged particles out into space.

It's called the solar wind.

Some of that solar wind is made of hydrogen.

On the Earth it doesn't get to the surface because we have an atmosphere around us.

On the Moon it does get to the surface and it gets mixed up in the lunar dust so there is probably a whole bunch of hydrogen on the Moon that is derived from the Sun.

And again, we'll find out how much is there once we go back and do some more exploring.


>> That's great.


We have some inquisitive fourth graders here.

I love it.

Caroline would like to know if we did find water on the Moon, would the Sun make it evaporate?


>> Very good question.


And you know there are two things that would cause water on the Moon to evaporate.

One is heat and the other is the fact there is no atmosphere to provide pressure.

If you boil water on a stove what you're doing is raising the temperature of the water so the vaipor pressure equals or exceeds the atmospheric pressure.

When you have no pressure at all, because there is no air on the Moon, the water just starts boiling right away.

Now, if it's in the form of ice it just evaporates.

It does what is called sublimateing.

So if we send astronauts to the Moon and want them to get water from ice in the lunar soil, they'll have to collect it and then keep it contained in special containers that keep it from evaporating away.


>> Okay, great.

Alec looks like same class would like to know if we find water that is usable on the Moon, can we plant trees and create different atmosphere?


>> Boy, great question, Alec, you know, that is a really important capability that we want to have available for astronauts.

Not only who go to the Moon but who go to Mars.

Because if you're going to go all the way to the Moon or you're going to go all the way to Mars and live there for many, many months, you're not going to be able to bring all your food with you.

It is so heavy that you would need a rocket too big, you couldn't even build a rocket that big to get all of the supplies that you would need to live on the Moon or Mars for six months or a year.

So we're looking forward to the time when astronauts can grow their own food on the Moon or on Mars using greenhouses just like we have here on Earth to grow plants in the wintertime.

And, of course, plants and every kind of living thing that we know of requires water to live so yes, water would be required for that as well.


>> Okay.

I think someone here wants us to answer the questions of the challenge for them but we're going to give them something here.

Samantha wants to know what obstacles.


>> Wouldn't be much of a challenge if we gave them the answers now, would it?


>> We're assuming we have all the answers, which is not necessarily true.


>> There is a point.


>> What obstacles will be faced in plotting a course to the Moon and how or what can be used to plot this course to the Moon?


>> I'll have to tread carefully here so I don't give you the answer to the challenge questions.

The Moon isn't always the same distance away from the Earth.

Sometimes it takes more power to reach the Moon than in other times, okay?

The other thing is that the Moon is always moving.

So you are trying to hit a moving target.

That makes it more complicated.

You want to hit a particular spot on the Moon?

Well, you're going to have to look at the best way to reach that spot at different times of year.

Because the Moon's orbit is at a slight angle relative to the Earth's orbit.

At one time of year it will be in a slightly different orientation with respect to the Earth that it would be at other times of the year.

The problem -- the reason it's complicated is because the conditions keep changing all the time.


>> Good answer.


>> I didn't give too much away, did I?


>> You didn't.

I will also add one thing she should remember is spacecraft do not travel in straight lines.

So keep that in mind.

It is not going to be a simple direct course from point A to point B.


>> That's exactly right.


>> Also keep in mind that you're wanting to reach a lunar pole as opposed to the equatorial region of the Moon so that will change your course a little bit.


>> You might have to do some fancy maneuvering to reach the poles of the Moon, and how would you do that especially if you didn't have a lot of extra fuel, hint, hint.


>> Good point.

Since you mentioned fuel, we should point out that we are wanting our spacecraft to have time to offgas any residual fuels so when they impact the lunar surface we don't have a contaminated sample of lunar dust.


>> The big centaur upper stage is full of fuel when it blasts LCROSS and LRO into Earth orbit and onto a path to the Moon.

We want to make sure that the centaur vents all of its extra fuel into space long before it hits the Moon because we don't want to see any of that fuel in the ejecta that comes from the impact.

We just want to see what's on the Moon, not what we made to power the rocket when we sent it into space.


>> Exactly.


>> Okay.

We're getting some great questions here.

Jacqueline would like to know how the lunar probes stay on the Moon if there is such little gravity on the Moon.

Would that be the same way other things would be kept down?


>> Well, that's a good question.

So there is less gravity on the Moon than there is on Earth but remember we looked at the astronaut hopping on the Moon, so he put some force in with his legs and he pushed off and he did go up but he didn't stay up forever and he certainly didn't fly off the Moon.

He did come back down.

So you can see there is enough gravity on the Moon to keep things down without any other special means necessary.


>> Okay.

Dylan wants to know how fast does the Moon orbit in relation to the Earth and how fast will the rockets propel the craft?

Now we're getting into the nitty-gritty.


>> The Moon goes along with its orbit at 2,000 miles-per-hour.

It goes its own diameter.

It's 2100 miles across.

It goes its own diameter once every hour.

I think I've got that right.

You should probably check that.

You can research that.

You're asking me things you could research.

So let's talk about how much thrust you need.

So in Apollo, remember we saw that video of the rocket engine, the rocket stage leaving the Earth when I showed my little video there.

That rocket, which was called the S4B.

It was the third stage of the giant Saturn 5 rocket.

That put out 200,000 pounds of thrust with a single engine.

That's because the Apollo spacecraft was so big and heavy it needed that much power to get it going up to the right speed to reach the Moon.

With LCROSS, the spacecraft and the centaur upper stage are much less heavy so the centaur only needs about 33,000 pounds of thrust so get LRO and LCROSS onto the right path for the Moon.


>> Okay.


>> The right speed, I should say, for the Moon.


>> All right.

The question from Andre again in Romania, why did you choose these methods to crash a rocket and another rocket to see if there are molecules of water and not send a robot or a rocket to land there and search for it?


>> Well, you know, you could do that but here was a case where we already knew we were going to be sending this lunar orbiter, this very high-powered orbiter called lunar reconnaissance orbiter.

Somebody realized that hey, there is an opportunity here because once that centaur upper stage is done with boosting LRO towards the Moon, we could use it as an excavation.

We could use it as if it was a big drill or a big scoop to blast dust out of the Moon and get it going high enough so we could actually send another little spacecraft through the ejected material and analyze it and by the same time, we would also be able to maybe observe it in telescopes from Earth.

So this was a case of an opportunity that came up and somebody was smart enough, a bunch of people were smart enough to be able to take advantage of that.

Now maybe someday, especially if LCROSS does find evidence that there is ice at the poles, I would bet you that we will send a robot to go explore that ice in more detail.


>> Terrific.


Simone from miss Jameson's class would like to know how much memory does the computer hold on the LCROSS and LRO?

And how many gallons of fuel does the craft's tank hold?


>> You know what?

I don't have the answer to either of those.

So will you do me a favor and look into that on the web?

I'll bet if you Google it you can figure all that stuff out and email us and let us know what you find.


>> That's a great suggestion.

All right.

Esther would like to know whether you'll be able to see the plume with binoculars.


>> I think you need kind of a sort of backyard telescope size.

I'm not sure if you'll be able to see anything with binoculars or not.

Brian would know the answer to that.


>> They're saying that probably telescopes with about a 10 to 12 inch diameter will be able to see the plume, assuming that North America is positioned in the right location when the impact happens.

Binoculars may not be quite powerful enough.


>> Sounds like binoculars won't be powerful enough.

A 10 inch telescope is a nice sized amateur telescope.

And again as Rebecca said, because the Earth is turning, it depends on when LCROSS hits the Moon which country or countries are facing the Moon at that moment.

They're the ones who will be able to observe the impact.


>> Exactly.


>> Okay.

Another question from Felix.

Considering this project will reveal water on the Moon, how will the water be used as long as the water has no natural cycle for it?

There has to be a cycle for the water just like Earth's for the outpost to last.

And will there be a risk of evaporation?


>> Really good question, really good question.

You know what?

You've just identified one of the most important challenges for engineers to solve in order to make it possible for humans to live on other worlds.

And that is that we -- water is a very precious resource on any alien world, whether it's the Moon or Mars or anywhere else.

And so one of the things we want to do is learn how to recycle water.

All kinds of waste water, whether it's urine or perspiration or there is even a little bit of moisture in your breath as you breathe out.

We're already developing those systems for use on the International Space Station, which is in low Earth orbit.

And so if we can solve those challenges on the Space Station and with other work down here on the ground, we'll be able to develop ways of recycling water and getting as much use out of it as possible.


>> Okay.

Myself Jameson's class has already started to do their research.

Randall is asking what kind of engines are you using for the LRO and LCROSS?

And what are the specifications of the engines and crafts used?

And what will be the consideration for our challenge navigation design?


>> And what is my answer to that question?


>> Wow.


>> We're going to send you back to the web because that information is on the web and if you're clever with your web searching you'll be able to find the specifications of all of those things, which I don't have in my brain at this moment.

But they are easily available on the LCROSS website and by googling around you can find just type in LCROSS, thrust, you know, rocket, LCROSS rockets fuel and you'll get to it.


>> For the purposes of this challenge in particular, our main focus is the path that you'll be following and not as much the type of spacecraft that is following that path.


>> Right.

But if they want to get for extra activities if you want to really carve out some time to look into these other things, that information is definitely available to you.


>> Just a couple more that we can hit.

We have some good questions in here about when people will travel to Mars and things like that.

For the purpose of this shortened time I want to stick with the ones that are right on the challenge.


>> We'll stop with this question here.

The time has crept on for us.

Let's see, the question comes from HMS girls.

I don't know who you are, girls, but great, welcome.


>> They're ready to set sail.


>> They're asking a very important question.

What kind of dangers do you encounter for a spacecraft on a trip to the Moon?


>> Oh my goodness.

That's a great question.

I sort of feel like they should answer that and tell me, don't you think?

But think about the fact that there is no air.

What are the things -- here, what are the things that the atmosphere on Earth protects us from?


So if you start thinking about that, and then you say there is no air in space to protect you and it should be a pretty straightforward process to figure out what the dangers are.

I'm going to leave it at that.

Start with the fact that there is no air in space and ask yourself, if I don't have any air around me, what are my dangers?


>> Okay.

Well, that concludes the Q and A portion of our webcast.

I want to thank Linda for fielding your questions and passing those along to us.

I certainly want to thank you, Andy, for giving such good, detailed answers.


>> My pleasure.


>> And also thank you to our audience.

We really appreciate that you've signed on and joined us today and so it's very exciting to us to have your participation.

Before I do the final wrap-up, Andy, would you like to make any comments to the students out there?


>> Yeah.

I think as you start to think about these challenges and the other questions that you asked, you know, think of yourselves as explorers and discovererers.

You're training your minds to go out and explore and discover what is out there.

And so you're getting prepared for the next great explorations that we're going to do in space.

And so we're passing the torch to you.

Go out there and do great things.


>> Great.

Thank you.


So to wrap up, we have a couple slides that I want to show you to give you an idea of what you're going to be doing.

The next step for you as a challenge participant is to research space navigation.

We've given you some things to think about today and certainly want you to go and explore those topics in more detail.

You're going to use your research and the information from our educator guide and from this webcast to developing the navigation plan and that plan is going to be guiding a spacecraft from Kennedy Space Center cape Canaveral, Florida all the way to the Moon's north pole.

Think about how you'll do that.

What is that navigation path going to look like and what instruments will you need to make that happen?

We're going to ask you to submit the written plan and your map to us by March 30th for review.

That's going to be a preliminary review.

We'll take a look at your ideas.

We'll give you some feedback and some further guidance and then you will have time to refine your plan and send us your final project by the end of April.

So certainly if you want us to review it ahead of time, March 30th is the magic date.

You may be wondering how else can I get information?

So there is some helpful tools that we have available for you.

One is the educator guide your teacher should have.

Inside that guide we have some basic information that will get you started, as well as a whole list of links of other websites you can go to.

We also have the website, the challenge website on quest at

It also has all the links listed.

That's another path to those bits of information.

We will also be archiving this webcast.

If you want to go back and listen to it again it will be posted on the web.

Okay, so a couple of other things I want to remind you of as we have some weekly questions that we'll start posing to you beginning on Monday.

These are just kind of fun questions to keep you going throughout this eight-week process.

We will be choosing the best answers and the ones that come in the fastest and those classes will be receiving a prize.

We also plan to have a web event midway through this challenge at the beginning of April, so keep looking at the calendar for that.

And then for our teachers I want to remind you that if you haven't already, be sure to register your class and to fill out the pre-challenge survey.

This certainly helps us in monitoring the effectiveness of these challenge activities and finding out how many people are actually participating.

It only takes a moment.

The surveys are short and the registration page is short as well.

If you haven't had time to do that please register your class now before they begin the research process so that we can do an accurate assessment.

That really helps us out a lot.

And the final thing that I want to mention is for those classes who do register and whose teacher completes the pre-challenge survey and the post challenge survey, we will enter those classes into a drawing and we'll select one winner who will receive a slice of an actual Moon rock.

That's pretty exciting.

That could be a really neat feature to add to your classroom.

A little motivation there to fill out the registration page and the pre and post challenge surveys.

With that said we'll draw to a conclusion and we wish you good luck.

 FirstGov  NASA

Editor: Linda Conrad
NASA Official: Liza Coe
Last Updated: October 2008