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Spaceflight

¨  How many gallons of gas does it take for the astronauts to get to the moon and back to earth?
¨  Can someone majoring in aerospace engineering go on a space mission?
¨  Would slow ascent to orbit and slow descent to earth be better for orbital space travel?
¨  Why do humans explore Space?
¨  Why doesn't NASA use the metric system?
¨  How are fuel loads figured on spacecraft on-orbit?
¨  How do you reduce impact damage to the space shuttle when it travels so fast?
¨
  Advice for boy interested in engineering / Inspiration from Homer Hickam
¨
  Why is it that spacecraft have to reenter the atmosphere at high speed?
¨  What are the 15 member countries of the European Space Agency?
¨
  Why do we spend money on space?
¨
  How could the space shuttle Columbia been saved while in orbit?

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QUESTION:
How many gallons of gas does it take for the astronauts to get to the moon and back to earth?

ANSWER from Roger Herzler on 24 February 2006:
The amount of fuel needed to get to the Moon is completely dependent on the weight of the vehicle making the trip AND the profile of the mission to get there.  The more it weighs the more fuel it needs to start with.  The mission profile refers to the distance to be traveled to the Moon (which can vary depending on where the Moon is in its orbit) and what type of landings are to be done.

Having said all of that, let's look at the Apollo missions of the 1960s and early 1970s as an example.  Keep in mind that a mission today would probably use different amounts of fuels, etc. due to changes in materials available.  However, it still comes down to weight and missing profile.  This website provides a wealth of information about the Apollo mission:

Apollo 11 30th Anniversary
http://www.boeing.com/news/feature/apollo11/factoids.html

It is probably important to point out that the fuel used was split into different parts of the complete rocket, called "stages".  As each "stage" is complete, the remaining section of the rocket that no longer has any use is dropped away since its fuel is spent.

So, according to that website, the Saturn V rocket itself had 5.6 million pounds (or 960,000 gallons) of propellant.  The total amount of propellant (fuel and oxidizer) in the Saturn V launch vehicle, service module, and lunar module was 5,625,000 pounds.

Note that it isn't "gas" as you might get from your local gas station.  It consists of a fuel and an oxidizer.  It can be liquid or solid.  Many missions use a combination of both.

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QUESTION:
Can someone majoring in aerospace engineering go on a space mission?

ANSWER from Stephanie Wong on 12 February 2006:
Definitely, if they become an astronaut!  Astronauts come from many different backgrounds.  Some are engineers, some are astronomers, and some are even doctors!  Being an aerospace engineer enables you to know more about aeronautics/space per se, but is certainly not a requirement to become an astronaut.  Astronauts need to be well-rounded, a team player and excel in whatever they do as a job.

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QUESTION:
The question is about slow ascent to orbit and slow descent to earth, will this be better way for orbital space travel?  Current practice is to burn rocket's LOX to reach Mach ~10, accelerating ascend to orbit and then descend in flat (maximum drag with heat shield protection), at probably Mach ~8.  In different scenario, I would prefer to ascend gradually (releasing appropriate amount of LOX burn, instead of full blast) and descend gradually (by means of using remaining LOX to provide reactive force and induce more drag) to attain slow and gradual descend.  This should reduce high temperature effects and shock-waves in hypersonic flight characteristics.  Please help to explain these benefits if we discard the short exposure time scenario.

ANSWER from Dean Davis on 6 February 2006:
First of all, Liquid Oxygen (LOX) is just an oxidizer.  In order to propel a rocket it must be combined with a propellant such as Liquid Hydrogen (LH2).

As far as your theory on slow ascent and descent improvements on the hypersonic flight profile, it has been considered in the past, but rejected due to massive fuel requirements for non-air-breathing systems such as we currently use to go into space.

However, your technique could work on a hybrid SCRAMJET/Rocket aerospacecraft.  Such a system could be launched initially via a rocket until sufficient air velocity could be forced into the LH2-fueled, Supersonic Ramjet (SCRAMJET) engines to ignite them.  The initial booster rockets would then be dropped and the launch vehicle would fly like an aircraft up to about 49 miles where it would run out of air, and would activate its LH2 and LOX engine to boost it into orbit.  Once in orbit it would maneuver and eventually deorbit via its LH2 and LOX engines.  Upon atmospheric reentry, it could once again use its LH2-fueled SCRAMJET engines to fly to an airfield for a safe, powered landing, unlike the unpowered glider landing of the current Space Shuttle.

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QUESTION:
Why do humans explore space?

ANSWER from Stephanie Wong on 6 December 2005:
There are many reasons that people explore space.  If you search on the Internet, you will find many opinions, so what I will do is provide my personal reasons for exploring space.

To me, the excitement of life is to discover new things, whether they may be trivial fancies, a cure for cancer, or, in my opinion the most fascinating, space.  Humans have been bound to this Earth for all their existence.  While there are many wonderful things to explore on this planet, what has been entirely mysterious to us is what is beyond our globe.  There are other planets, some of which have conditions suitable for life.  Each of them are relatively unexplored.  When we do explore them, many aspects are "alien" to us, entirely different.  Beyond the solar system, there are an infinite number of stars and galaxies.  Perhaps there are other "Earths" out there.  Perhaps other planetary systems out there are beyond our imaginations.  Space also tells us about our origins.  The Big Bang, the explosion that created our universe raises many questions, scientific and even religious.  More immediately, knowing the evolution of the planets Mars and Venus, can tell us much about our past, present and future climates, which of course is a big concern for human society.  To me, space is the unchartered territory that simply invites us to explore it.

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QUESTION:
A recent Galileo status report said, "The spacecraft has now entered the solar wind, which is a stream of particles emitted continually from the Sun that flows at roughly 400 kilometers per second (about 1 million miles per hour)".  Why are people at JPL perpetuating a very confusing use of units of measurement?  First of all, "about" seems to be a real stretch when speaking of numbers so large.  I am guessing that they are making comparison to miles per hour, like Americans see on speed limit signs, to make it more understandable to the average American.  But don't they use nautical miles (not land miles) for space type measurements?  This creates an even bigger difference in the estimate and a bigger confusion factor.  Why don't people at JPL and NASA use international units?  After the Mars Climate Orbiter disaster, the world is looking at these errors.

ANSWER from Joseph P. Fearey on 20 June 2000:
JPL has been using the MKS measurement system since at least the early Seventies.  MKS is meter, kilogram, second, the "standard" scientific measurement system.  The project that I have worked on since 1981 has always used MKS for computation, although we do put out reports in other measurement systems to meet user requirements (what we call presentation as opposed to representation).

I think what you are seeing in the Mission Status Bulletin that you sent was that sort of thing, presentation vice representation.  Note that they're trying primarily to reach an American audience (the taxpayers who foot the bills).  The international audience must necessarily come second in consideration.

By the way, I don't think space measurements are normally made in nautical miles, at least I have never seen such.  Have you ever seen any?  Incidentally, although my project uses MKS, we put out both nautical miles and knots, because some of our users employ those terms.

Also, a final word on the "Mars Climate Orbiter disaster".  As I understand it, JPL was using MKS.  The contractor was not!

Joseph P. Fearey
Jet Propulsion Laboratory, Retired

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QUESTION:
How are fuel loads figured on satellites once they are on orbit?  What are the factors needed to determine how much fuel is left onboard a satellite?

ANSWER from Paul Woodmansee on 3 June 2005:
It depends on the satellite (or spacecraft for missions that are not Earth orbiters).

Almost all spacecraft and satellites use fuel for pointing control to change the direction the satellite is pointing (if the satellite needs to change pointing at any time.  Also, if reaction wheels are not used then fuel may be needed for attitude control with thrusters.  And even if reaction wheels are used then fuel must be used for reaction wheel desaturation maneuvers.  Various factors cause perturbations, including solar wind, gravity from passing objects, tides, rarified gas from getting to close to an atmosphere, etc.

For a low Earth orbit the launch vehicle typically puts the satellite into the final orbit.  Then the satellite has to have onboard fuel to do maneuvers.  In low earth orbit, there is still some rarified atmosphere which causes drag on the satellite.  This drag must be made up for with engine burns that take fuel.

For higher orbits, such as geosynchronous orbit (GEO), the launch vehicle typically doesn't leave you in the final orbit, but rather in a geosynchronous transfer orbit (which is an ellipse with an apogee at GEO but a perigee at low Earth orbit).  In this case the satellite must make a maneuver at apogee to achieve GEO, which takes a lot of fuel for a satellite.

If a satellite needs to change its orbit anytime in its life, then that takes fuel too.

For a spacecraft which goes into deep space, we need a lot of fuel for various maneuvers.  These may be trajectory correction maneuvers (fixing errors in course), or planned trajectory changes, etc.  The biggest deep space maneuvers are orbit injection maneuvers.  These happen when a fast moving spacecraft arrives at a planet.  In this case the spacecraft has to slow down, and not just fly by, so the thrusters must slow the spacecraft down.  This takes a lot of thrust in a relatively short time, and hence a lot of fuel.

I hope this give you an idea about what factors need to be considered.  A lot of mission planning is done even before the spacecraft is designed to determine how much fuel will be needed, so that the spacecraft is sure to carry enough.

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QUESTION:
With NASA's new project (Prometheus), I would like to know how they plan to reduce damage to the shuttle when travelling at a fraction of the speed of light?  Even minute objects would devastate the shuttle when it travels at these high speeds.

ANSWER from Gregory H. Johnson on 13 July 2004:
Although the shuttle achieves high speeds during orbit (~17,500 mph), we don't reach such speeds until outside of the Earth's atmosphere and consequently well away from objects in our atmosphere that might impact the shuttle (birds, debris aloft, etc).  Indeed, history has shown that the greatest risk we've experienced from debris impact situations is from other parts of the shuttle system itself (External Tank (ET) debris, Solid Rocket Booster debris, or a debris strike from a piece originating from another portion of the shuttle itself).  Columbia's (STS-107) debris strike was in that category -- a chunk of foam flew off the ET and hit the shuttle's leading edge, causing damage.  We're working to minimize such risks by making design changes to the foam and other subsystem areas that pose the greatest debris risks.  However, we cannot eliminate 100% of these risks.

There is also a slight possibility we might encounter high speed debris on orbit from micrometeoroids.  Therefore, we're also working on techniques to identify, inspect, and repair any damaged areas if the shuttle does experience such a debris event.

You mentioned the possibility of small impacts devastating the shuttle.  Our experience and engineering modeling show that small impacts might damage the shuttle, but we don't expect devastating results even at very high relative speeds.  If an impact does happen, we will make every effort to repair the area, especially if it is part of the reentry heat shielding subsystem.  If an impact makes a hole in the pressurized cabin, our environmental control system can generate pressure to sustain cabin pressure -- so we can buy time to either repair the hole or promptly return to Earth.

Gregory H. Johnson
NASA Astronaut
Johnson Space Center

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QUESTION:
I am from Colombia, I am twelve years old, I am studying and I live with my sister and my mother in Madrid, Spain.  I have always interested in knowing about the NASA, because I admire the job that they do.

Since I was a little boy I liked the toys that they come in parts and then I assembled them.  I really enjoy making up new things, although I have to repeat several times until I get to do well.  Sometimes, first I do a plan on the paper and other times I plan it in my mind and then I do directly.  I like to assemble cars, different kind of planes, spaceship, submarines and robots.  Generally I do this activity on the floor and it takes me hours and hours.  I remember the last time I had to repair the motor because it damaged several times.  I enjoy this because it lets me use my imagination.

Very often I help my mother to repair things at home like the iron, the blinds, the table, the television set, plugs, etc.  She is happy for this but also she worries because she thinks that some might be dangerous for me.

I would like to know if there is some program or scholarship for interested boys in this subject (engineering) or if there is an opportunity for knowing some installations or laboratory where a company plans and makes machines.  I really like this activity and I would like to continue improving, acquiring knowledge and gaining experience; I don't like to leave it.

ANSWER from Dean Davis on 7 March 2004:
I am glad to hear that you are interested in the space program and that you have a great deal of curiosity about the way things work.  You seem to have the makings of a great scientist or engineer.  Keep up the good work.  However, pay attention to your Mom, electricity can be extremely dangerous.

As I understand it you are currently living in Madrid, Spain.  I used to work just north of your location in Toulouse, France for the European Space Agency (ESA) on the Hermes European Space Shuttle, Ariane 5 and Columbus European Space Station Module.  Sadly, the Hermes program was cancelled, but the Columbus and Ariane projects were completed.

Here in the United States they have a Club for students your age interested in the space program called the Young Astronauts.  I don't know if it's available in Europe.  There is also a European Space Camp in Cain, France you might check into.

Dean Davis
Senior Principal Scientist/Engineer
Boeing Aerospace Company
California, USA

ANSWER from Homer Hickam on 13 March 2004:
An author is always gratified when it's clear his work has touched so many people, especially young people around the world.  I hope you will get the true message of the Rocket Boys in my movie October Sky, which is this: it is important for everyone to find a passion in life, then work very hard to make it come true.  To only dream of a better future is inconsequential.  Each of us must take the next steps beyond and learn to map out what must be done to reach our goals.  After that, it's easy.

The Rocket Boys succeeded with their rockets and their lives because they followed what I call the "3 P's for a happy and successful life":

Passion, Planning and Perseverance.

We Rocket Boys decided what we really really wanted to do, our passion.  Then we asked people to help us make a great Plan to achieve that goal and we stuck to our convictions and the plan no matter what.  Persevere, Persevere, Persevere!  I hope you do the same.

As O'Dell said in Rocket Boys / October Sky, "A rocket won't fly unless somebody lights the fuse."  His was a literal meaning but he was also voicing an important idea.  Nothing will happen unless someone takes the initiative to make it so.  To be passive and wait for something good to happen in your life is to probably experience vast disappointment.  You must learn to move, to exert yourself, to let dreams translate into reality through hard work, study, and working with other people.  It is my belief that there are no boundaries to excellence and success except for those we place on ourselves.  There are so many people - our mentors and teachers, our parents, our families, and our friends - who are willing and able to help us if only we let them know what it is we want to do.

In the end, we determine our own success through our own labor.  As my dear teacher Miss Riley said to me once long ago, "All I've done is given you a book.  You have to have the courage to learn what's inside it."  She was referring to an advanced text on rocketry which required an understanding of higher mathematics quite beyond me at the time.  She was confident, however, that her challenge to me would be enough to make me try to learn.   She was right.  I studied, I learned, I worked hard, and I succeeded.  If a boy in a small, dying coal town in West Virginia can do those things, so can you.

Best wishes to you and good luck in all that you do.  Remember, if you never have dreams, they never come true.  AIM HIGH!

Sincerely,
Homer Hickam
author, retired NASA engineer

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QUESTION:
Why is it that spacecraft have to reenter the atmosphere at high speed?  Wouldn't it be possible to devise a slow, controlled reentry?

ANSWER from Paul Woodmansee on 16 January 2004:
To slow a spacecraft down takes propellant, i.e. rocket fuel, and lots of it.  If MER, or any other Mars lander, had to slow down even to orbital speeds then it would have to carry bigger rocket engines and a lot of propellant.  It would then be a larger spacecraft and have to get launched on a much bigger launch vehicle.  All of this would make the mission much more expensive.

That's what happens with Mars Orbiters, they have to be smaller and lighter spacecraft so that it doesn't take as much fuel to put them in orbit.  And even then, they typically need larger launchers.  To reduce the amount of fuel carried we have the orbiters dip slightly into the atmosphere again and again to slow down due to friction.  This is called aero-braking.

To slow a spacecraft down so much that it wouldn't have to enter at high speed would take so much fuel that we would be unable to launch the spacecraft off of Earth.

So that's why we do things the way we do them.

Paul Woodmansee
Propulsion Engineer
California

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QUESTION:
What are the 15 member countries of the European Space Agency (ESA)?

ANSWER from Stephanie Wong on 30 May 2003:
The European Space Agency was founded in 1975, an intercontinental organization to support space exploration in Europe.  The 15 member states of the ESA are: Austria, Belgium, Denmark, Finland, France, Germany, Ireland, Italy, the Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom, of which some are part of the European Union.  Canada acts as a cooperating cooperating state for the ESA.  Headquartered in Paris, France, the ESA has 4 other main branches: the European Space Research and Technology Centre (ESTEC) in the Netherlands, the European Space Operations Centre (ESOC) and European Astronauts Corps (EAC) in Germany, and the European Space Research Institute (ESRIN) in Italy.  The ESA's launch facilities are in French Guyana in the South America, although they frequently launch from Russia's spaceport in Baikonur, Kazakhstan.

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QUESTION:
Why do we spend money on space when we should be spending it right here on Earth?

ANSWER from Dave McCarter on 13 February 2003:
A student in one of my classes asked that very same question!  Bear in mind this is a student studying electronics and very keen on high tech, yet abysmally ignorant of economic realities, including the fact that one day soon he will be looking for a nice job in the high tech sector, maybe even working on equipment bound for space.  I told him how little the space program costs each Canadian per year compared to almost every other aspect of government.  I asked him if he thought we were shipping money into space to pay off the aliens so they will leave us alone.  Amazingly, it had never occurred to him that all we really send to space is a few hundred kilos of aluminum, and other junk, and the money goes into the pockets of highly trained technicians and engineers.  And he wants to be one of those!  Incredible!

Dave McCarter
President, London Centre
Royal Astronomical Society of Canada
London, Ontario

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QUESTION:
Greetings and condolences to all of you that are a bit closer to the heroes we lost.  I have a question about what could have been done assuming that it was discovered a critical number of heat shield tiles were missing from the shuttle orbiter Columbia.  It has been stated that there are no capabilities to repair missing tiles.  Would it have been feasible to dock the Columbia to the International Space Station and send Atlantis to bring back the Columbia crew?  If so, what would have become of the Columbia?  How would we have retrieved it?

ANSWER from Stephanie Wong on 5 February 2003:
Thank you for your message.  While we at Imagiverse are not directly working with NASA, we know of many people who work in the shuttle program.  It is appreciated that we have so many folks expressing their concerns and condolences.

I would like to remind you that we are not an official source.  We do not represent NASA, and what we say is factually correct to the degree that we can research.  Please refer to the NASA website www.nasa.gov for official information.

Since it is early in the investigation, one can only speculate what has happened to the orbiter.  You mentioned the shuttle tiles, which is attracting much attention, for it looks like the possible cause of the accident.  It is too early to tell if that was indeed the cause.

If you have heard the numerous NASA press conferences, they emphasize that there is nothing that they can do to repair the tiles once in orbit and that it is imperative to make sure no tile gets seriously damaged PRIOR to launch.  While in orbit, there is no mechanism to take the astronauts over to the underside of the orbiter.  And even if the astronauts could get there, it would be impossible to repair a tile in space.  It is difficult enough while on the ground.

Now, if it is known that an orbiter is incapacitated and that it would not survive reentry, you ask whether it could fly to the space station.  No.  The area around Earth is extremely large and the orbiter does not have enough fuel to change its inclination or its altitude to match that of the ISS.  Even if the orbiter was at the same inclination and altitude, it would not likely be along the same path as the ISS.  Its "right ascension" would be different, so the orbiter would trace a path that might not intersect with the ISS for hundreds of days.  In the case of Columbia, it was at an inclination of 39 degrees and at an altitude of 150 nautical miles. The ISS, on the other hand, is at an inclination of 51.6 degrees at an altitude of about 200 nautical miles.  Therefore, Columbia was very far apart from the station, and unlike a car, you just can't take a detour and drive off to another location.  Shuttle launches take a lot of planning in the part of determining the launch "vectors".  They have to launch at a certain speed, direction and time to get to the exact location they want to be.  For launches to the ISS, there is only a launch window of about 5 minutes from which the shuttle can reach the station.  It is a precise task to reach the station.

Suppose Columbia was near the vicinity of the ISS.  Still, Columbia did not have its docking adapter with it.  In this mission, the SPACEHAB laboratory module was attached to Columbia's airlock.  I am uncertain as to how the crew could have gotten out of the shuttle and into the station.  That would be a difficult task without the two spacecraft physically docked.  Another matter is that there were not enough EVA suits in Columbia.  How would EVA suits been transferred to them?

Now add Atlantis to the picture.  Atlantis was set to launch to the space station in early March.  If it was known that Columbia was in emminent danger, there was a good chance that Atlantis' processing could be quickened to get it into space a week or two earlier.  Since Columbia cannot get to the ISS, Atlantis would have had to somehow rendezvous with Columbia.  This sort of mission is very risky, considering astronauts have to be transferred between two detached spacecraft.  Plus, if the rescue was successful, there would have been a great deal of people inside Atlantis for landing.

Columbia would not have been retrieved.  It couldn't have been retrieved, as there is nothing big enough to enclose the orbiter to bring it home.  It would have been left there as "space junk" to deorbit, or have been put into a configuration where it would quickly deorbit and also be destroyed in the atmosphere.

Again, I emphasize that this is all hypothetical.  We still do not know exactly what happened to Columbia.  There was no indication of serious threat on Columbia while it was in orbit, so any rescue procedures are entirely speculative.

I would like to end off with a comment about the risks of spaceflight.  Going into space is not routine.  It takes thousands of people working on the ground and the astronauts up in space to pull off a mission.  But, however "dramatic" a space mission might be, take in mind all the people on Earth who risk their lives in their professions, too.  Construction workers, firefighters, miners, healthcare workers and an endless list of people put their lives in jeopardy every day.  They and the astronauts are all brave souls, willing to do good in spite of the danger.  We should thank them for that.

Stephanie Wong
Imagiverse

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