The Question

What do I have to do to became an astronaut?

The Answer

For this we can perhaps point you in the right direction. We do not know how far along you are in school now, so our suggestions might not be totally appropriate:

In school from K-12: Work hard and get A's. These programs are very competitive, so it is important to do well in school (especially in math and science).

You might also think about where you go to college. If you want to be pilot, you might think about going to one of the military academies (Air Force, Army, Navy), because they will teach you to fly. These have the advantage that they are free for you to attend and you will become an officer when you graduate. If you plan it correctly, you will be a pilot and get lots of flight experience and technical training. Most pilots are from a military background, while the mission specialists are usually civilians.

To be a mission specialist, you will need some academic area of expertise. If you work on the development of detectors on satellites, this would be very helpful. We suggest that you apply for the nasa summer programs and pick a major and research projects in the Earth or Space sciences, or Engineering, that involve NASA missions. You might want to look at the NASA programs home page at:

http://www.nasa.gov/centers/goddard/education/

so that you can apply for them when you become qualified.

Once you have obtained your B.S. and the required amount of experience, you will need to apply to the astronaut training program. All we know about this program we learned from reading the home page at:

http://www.jsc.nasa.gov/Bios/more.html

We suggest that you read this home page now, and periodically in the future, so you can plan towards that goal. You will need both to fulfill the basic requirements and be better than many others who apply.

Good luck, and we are sure that if you work hard toward this goal it will pay off for you in the long-run whatever you decide to do.

Jonathan Keohane and Koji Mukai
for Imagine the Universe!

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The Question

I have one silly question if you can respond to me. I am working in a Japanese cosmetic company, and our president plans to climb Mt. Everest this year. He is over 60, so he is worried about keeping his body temperature. He is wondering what kind of underwear astronauts wear to keep warm?? I checked the homepage of Star Child Team, and other homepages. They say astronauts wear same usual clothes inside, but how about outside of the shuttle??

The Answer

We work on developing, building and analyzing data from detectors designed to observe X-rays and gamma-rays, and don't have expertise with human space flight. I did do some hunting around for information about the astronauts and didn't find anything specific about what they wear underneath their space suits. I think the suit itself probably provides the protection from extreme cold temperatures but I am not sure of this.

You should submit your question to the Ask an Astronaut page. It can be found at

http://www.kennedyspacecenter.com/Ask-an-Astronaut.aspx.

Maybe you will get an answer from someone with first-hand experience!

There is also a database of questions previously answered by astronauts:

http://spaceflight.nasa.gov/feedback/expert/index.html.

Regards,
Padi Boyd
for Imagine the Universe!

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The Question

When you are up in space, do you ever get lonely?

The Answer

Our Laboratory at NASA's Goddard Space Flight Center is interested in sources of X-ray and gamma-ray emission in our universe. No one in our Laboratory has ever been into space. I can give you the following lead, however, to directly ask some of NASA's astronauts if they were ever lonely.

Because of the extremely high volume of e-mail they would receive if their addresses were public, astronauts' e-mail addresses are restricted. However, you can write them at the following address:

Astronaut Office/CB
NASA
Johnson Space Center
Houston, TX 77058

Good luck!

Regards,
Laura Whitlock

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The Question

My first graders want to know, How do astronauts go to the bathroom in space? I think the potty chair is in place. Is this correct?

The Answer

We have come up with a number of answers to your question. We will let you, as the professional teacher, decide which is appropriate for your classroom and what is best left to the teachers lounge.

---

I. The Official NASA pages:

A. There is a nice space shuttle web page at: http://shuttle.nasa.gov/. Digging in there I found a Q&A Web page. Here's what it says:
http://spaceflight.nasa.gov/shuttle/reference/faq/living.html

6. How do you take a bath, brush your teeth, and go to the bathroom in space?

We do not have a bath or shower on the Shuttle, so we just wash off with wet washcloths, using soaps that you don't have to rinse off. When we brush our teeth, we can either swallow the toothpaste or spit it into a washcloth. Designing a toilet for zero-gravity is tougher. We use air flow to make the urine or feces go where we want, since gravity will not do it for us. You have to be more careful and think about what you are doing with the toilet in the Shuttle.

B. Another colleague pointed out that Johnson Space Center is the home of the astronauts, and they have some web pages dealing with this issue too. (We really know little more than you do about the astronaut program -- but they do.)

Their home page at: http://www.jsc.nasa.gov/ has links for KIDS, EDUCATORS, and more.

I went to their page: http://www.jsc.nasa.gov/Bios/more.html and this is what I found:

This used to be under the old FAQ at Spacelink. It has since been removed.

---

4. HOW DO ASTRONAUTS GO TO THE BATHROOM AND TAKE CARE OF OTHER PERSONAL HYGIENE?

=Each Space Shuttle has a toilet that can be used by both men and women. Designed to be as much as possible like those on Earth, the units use flowing air instead of water to move waste through the system.

Solid wastes are compressed and stored on-board, and then removed after landing. Waste water is vented to space, although future systems may recycle it. The air is filtered to remove odor and bacteria and then returned to the cabin.

Astronauts brush their teeth just like they do on Earth. There is no shower on the Shuttle, so astronauts must make do with sponge baths until they return home.

The toilet that was first flown aboard STS-54 is completely new in design and offers new and improved features:

The new toilet features better hygiene, larger storage capacity, greater dependability, and an overall cost savings in maintenance.

-The previous model had a 14-day capacity for storage of waste material. The new model has an unlimited storage capacity.

-The new model features a cylinder system where a plastic bag is placed in the toilet before use. The bag is then sealed and is forced to the bottom of the cylinder after each use by a plunger attached to a lever. A new bag is then placed in the toilet for the next astronaut. When the cylinder is filled, it is replaced by a new cylinder.

-The previous model relied on air flow to pull the waste to a holding tank. None of the waste was separated as it is now. The new system provides better hygiene conditions. There was no way to empty the old system. When it was full, it simply could hold no more waste materials. It had a 14 day capacity.

-The new toilet also provides an odor-free environment. The old model did not.

-The opening in the lid of the toilet was increased from 4" to 8", allowing for easier handling of the plastic storage bags.

-The urine collection system was also improved. A newer type of fan system is being used to force the urine to a holding tank where it is periodically ejected into space, where it vaporizes.

-The previous system had trouble with corrosion in the fan system.

-The new toilet can be cleaned without removal from the orbiter at the completion of the mission, reducing the cost of servicing.

-The previous system must be removed and sent to a company in Houston, Texas for servicing.

---

I hope this helps.

Sincerely,

Jonathan Keohane and most all of the Ask an Astrophysicist Team
-- for Imagine the Universe!

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The Question

How would the unprotected human body react to the vacuum of outer space? Would it inflate to bursting? or would it not? or would just the interior gases hyperinflate? We are also relating this to short-term exposure only. This question primarily relates to the pressure differential problems. Temperature or radiation considerations would be interesting as well.

The question arose out of a discussion of the movie 2001. When Dave "blew" himself into the airlock from the pod without a helmet, should he have "blown up" or is there "no difference" as shown in the movie correct?

The Answer

From the now extinct page http://medlib/jsc.nasa.gov/intro/vacuum.html:

How long can a human live unprotected in space?

If you don't try to hold your breath, exposure to space for half a minute or so is unlikely to produce permanent injury. Holding your breath is likely to damage your lungs, something scuba divers have to watch out for when ascending, and you'll have eardrum trouble if your Eustachian tubes are badly plugged up, but theory predicts -- and animal experiments confirm -- that otherwise, exposure to vacuum causes no immediate injury. You do not explode. Your blood does not boil. You do not freeze. You do not instantly lose consciousness.

Various minor problems (sunburn, possibly "the bends", certainly some [mild, reversible, painless] swelling of skin and underlying tissue) start after ten seconds or so. At some point you lose consciousness from lack of oxygen. Injuries accumulate. After perhaps one or two minutes, you're dying. The limits are not really known.

You do not explode and your blood does not boil because of the containing effect of your skin and circulatory system. You do not instantly freeze because, although the space environment is typically very cold, heat does not transfer away from a body quickly. Loss of consciousness occurs only after the body has depleted the supply of oxygen in the blood. If your skin is exposed to direct sunlight without any protection from its intense ultraviolet radiation, you can get a very bad sunburn.

At NASA's Manned Spacecraft Center (now renamed Johnson Space Center) we had a test subject accidentally exposed to a near vacuum (less than 1 psi) in an incident involving a leaking space suit in a vacuum chamber back in '65. He remained conscious for about 14 seconds, which is about the time it takes for O2 deprived blood to go from the lungs to the brain. The suit probably did not reach a hard vacuum, and we began repressurizing the chamber within 15 seconds. The subject regained consciousness at around 15,000 feet equivalent altitude. The subject later reported that he could feel and hear the air leaking out, and his last conscious memory was of the water on his tongue beginning to boil.

Aviation Week and Space Technology (02/13/95) printed a letter by Leonard Gordon which reported another vacuum-packed anecdote:

"The experiment of exposing an unpressurized hand to near vacuum for a significant time while the pilot went about his business occurred in real life on Aug. 16, 1960. Joe Kittinger, during his ascent to 102,800 ft (19.5 miles) in an open gondola, lost pressurization of his right hand. He decided to continue the mission, and the hand became painful and useless as you would expect. However, once back to lower altitudes following his record-breaking parachute jump, the hand returned to normal."

References:

Frequently Asked Questions on sci.space.*/sci.astro

The Effect on the Chimpanzee of Rapid Decompression to a Near Vacuum, Alfred G. Koestler ed., NASA CR-329 (Nov 1965).

Experimental Animal Decompression to a Near Vacuum Environment, R.W. Bancroft, J.E. Dunn, eds, Report SAM-TR-65-48 (June 1965), USAF School of Aerospace Medicine, Brooks AFB, Texas.

Survival Under Near-Vacuum Conditions in the article "Barometric Pressure," by C.E. Billings, Chapter 1 of Bioastronautics Data Book, Second edition, NASA SP-3006, edited by James F. Parker Jr. and Vita R. West, 1973.

Personal communication, James Skipper, NASA/JSC Crew Systems Division, December 14, 1994.

---

Henry Spencer wrote the following for the sci.space FAQ:

How Long Can a Human Live Unprotected in Space?

If you *don't* try to hold your breath, exposure to space for half a minute of so is unlikely to produce permanent injury. Holding your breath is likely to damage your lungs, something scuba divers have to watch out for when ascending, and you'll have eardrum trouble if your Eustachian tubes are badly plugged up, but theory predicts -- and animal experiments confirm -- that otherwise, exposure to vacuum causes no immediate injury. You do not explode. Your blood does not boil. You do not freeze. You do not instantly lose consciousness.

Various minor problems (sunburn, possibly "the bends", certainly some [mild, reversible, painless] swelling of skin and underlying tissue) start after 10 seconds or so. At some point you lose consciousness from lack of oxygen. Injuries accumulate. After perhaps one or two minutes you're dying. The limits are not really known.

References:

The Effect on the Chimpanzee of Rapid Decompression to a Near Vacuum, Alfred G. Koestler ed., NASA CR-329 (Nov. 1965)

Experimental Animal Decompression to a Near Vacuum Environment, R.W. Bancroft, J.E. Dunn, eds, Report SAM-TR-65-48 (June 1965), USAF School of Aerospace Medicine, Brooks AFB, Texas.

---

You would probably pass out in around 15 seconds because your lungs are now exchanging oxygen out of the blood. The reason that a human does not burst is that our skin has some strength. For instance compressed oxygen in a steel tank may be at several hundreds times the pressure of the air outside and the strength of the steel keeps the cylinder from breaking. Although our skin is not steel, it still is strong enough to keep our bodies from bursting in space.

Also, the vapor pressure of water at 37 C is 47 mm Hg. As long as you keep your blood-pressure above that (which you will unless you go deep into shock) your blood will not boil. My guess is that the body seems to regulate blood pressure as a gauge, rather than absolute pressure (e.g. your blood vessels don't collapse when you dive 10 feet into a pool).

The saliva on your tongue might boil, however.

For more information and references, see

http://www.sff.net/people/geoffrey.landis/vacuum.html

Hope this helps!
The Ask an Astrophysicist Team

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The Question

I am curious to know what the effects of solar radiation have on space craft after they leave the protection of the Van Allen belt. How much protection do they need and how long could an astronaut survive in and out of his craft.

The Answer

Solar radiation and cosmic radiation are both things to worry about in space.

The ultraviolet (UV) radiation from the Sun (without our protective ozone layer and atmosphere to protect us) would be enough to rapidly give you sunburn, melanoma, etc. However, unless your spacesuit or spacecraft windows are specifically designed to let UV pass through, enough will be blocked that you don't have to worry about it too much. (If you are in space without a spacesuit or spacecraft, then you've got bigger problems than radiation.)

When the Sun flares, it produces x-rays, gamma-rays, and energetic particles. The energetic particles are the worst, but they are delayed compared to the X-rays and gamma-rays, so you have some warning that they are coming. This gives you time to get into a 'storm shelter', a well-shielded area that you can live in for a few days until the particles die down. A good place for a storm shelter would be in the center of the ship, surrounded by the water tanks. If you don't have a storm shelter (e.g. if you are out moonwalking in just your suit) a bad solar flare can kill you by radiation sickness.

The hard radiation (particles and x/gamma rays) from the non-flaring Sun is small compared to the galactic cosmic ray exposure. These particles come from deep space more or less continuously. Small amounts of shielding can cut out the majority of this, but the remainder will give you a somewhat increased risk of cancer. Using very conservative rules of thumb, a week in space's cosmic ray environment will shorten your life expectancy by about a day (statistically--it is very unlikely to give you cancer, but if it does, it will shorten your life by more than a day). Since space is inherently dangerous at the present state of the art, cancer due to cosmic rays is relatively small additional risk.

David Palmer
for Ask an Astrophysicist

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The Question

How is it possible for manned space flights to survive the effects of the Van Allen Radiation belt?

The Answer

As you know, the Van Allen radiation belts are doughnut-shaped regions encircling Earth and containing high-energy electrons and ions trapped in the Earth's magnetic field. Explorer I, launched by nasa in 1958, discovered these two regions of intense radiation surrounding the Earth. They are referred to as the inner and outer Van Allen radiation belts, after James Van Allen who designed Explorer I. The inner region is centered at about 3000 km above Earth and has a thickness of about 5000 km. The outer region is centered at about 15,000 -- 20,000 km above the surface of the Earth and has a thickness of 6,000 -- 10,000 km.

Typically, manned space flight (such as the Shuttle) stays well below the altitude of the van Allen radiation belts. Safe flight can occur below altitudes of 400 km or so.

SO ...what do we do when we have to fly through the radiation belts -- like when we went to the Moon or send probes to other planets?

In the 1960s, NASA asked Oak Ridge National Laboratory to predict how astronauts and other materials would be affected by exposure to both the Earth's Van Allen radiation belts and the Sun's radiation. Oak Ridge biologists sent bacteria and blood samples into space and exposed small animals to radiation. They concluded that proper shielding would be key to successful flight not only for living organisms, but for electronic instrumentation as well. To develop shielding for the Apollo crews, Oak Ridge researchers recycled the Lab's Tower Shielding Facility, which had hoisted shielding experiments aloft for the 1950's nuclear-plane project.

Regards,
Laura Whitlock
for Ask an Astrophysicist

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The Question

How are the Cosmonauts in MIR protected from Ultraviolet, X-Rays and Gamma-rays?

The Answer

Cosmonauts and astronauts are protected from UV, X-rays and gamma-rays by the material in the hull and windows of their spacecraft. The primary concerns are with gamma-rays and high energy particles, such as protons accelerated by solar flares. The choice of material and thicknesses are dictated primarily by structural and thermal considerations. Metals (which are often used to meet these considerations) are generally opaque to UV, X-ray and gamma-ray radiation.

I have not been able to find the specifications of the composition and thicknesses of the hull and windows of Mir. However, according to the Shuttle Reference Manual

http://spaceflight.nasa.gov/shuttle/reference/shutref/

the skin of the forward fuselage of the Shuttle is made of 'conventional 2024 aluminum alloy', while the crew compartment is constructed of '2219 aluminum alloy plate'. The windows are comprised of either 2 or 3 panes of glass, depending on the window location, with the panes between 0.25 and 1.3 inches and made of either aluminosilicate or fused silica.

Jim Lochner
for Ask an Astrophysicist

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The Question

Do you have a page about Laika and the Russian space program at that time?

The Answer

Laika flew on Sputnik II on November 3, 1957.

We have pages about Laika at:

http://starchild.gsfc.nasa.gov/docs/StarChild/space_level2/travel.html

and

http://starchild.gsfc.nasa.gov/docs/StarChild/space_level2/laika.html

You can find some pictures at:

http://www.enchantedlearning.com/subjects/astronomy/dogs/

I hope this is helpful!

Tim Kallman
for the Ask an Astrophysicist team

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The Question

This is the best site I could find to ask this question from my first grade class. We are studying bats (the mammals) and the students would like to know if a bat has ever been in space. If so, what happened?

The Answer

As far as we can tell, bats have never been in space. Oddly enough, Shuttle astronauts were asked the same question and Susan Still's reply implies that there have never been any bats on a Space Shuttle.

Sandy Antunes and Koji Mukai
for Ask an Astrophysicist

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The Question

I am working on an experiment for the Space Science Student Involvement Program for my Biology class. I was wondering if you could help me with my design. My proposal is about growing potatoes in space aboard the Spacelab. Please e-mail me any information that might be appropriate.

The Answer

Since we here at this laboratory work mostly on astronomy involving X-rays, gamma-rays, and cosmic rays, I don't have any real expertise in the subject of growing potatoes in space. However, as I am sure you know, there was an experiment on the shuttle spacelab flight STS73 which studied this subject. Some of the results are discussed in the following web page:

• http://www.engr.wisc.edu/centers/wcsar/astroculture.html

If this is information that you already have, or if you really want inside information about how the experiments were done, then I suggest that you get in touch directly via email or telephone with the experimenters mentioned in the first article. Most scientists are very happy to discuss their work with others, or at least to direct you to someone else who is! I hope that this is helpful to you.

Sincerely,

Tim Kallman
(for the Ask an Astrophysicist team)

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The Question

Do you have any knowledge about Valentina Tereshkova?

The Answer

Valentina Vladimirovna Nikolayeva Tereshkova was the first woman to travel in space in Vostok 6. Born in western Russia on March 6, 1937, she worked in a textile mill at age 18. Interested in parachuting as a hobby, she also trained as an airline pilot. She was not just the first woman to travel in space, but the first space traveler who hadn't been a test pilot, though her parachuting and piloting experience certainly qualified her for space work. Her Vostok 6 mission orbited the earth from June 16 through June 19, 1963.

You can see a picture of Tereshkova at the site:
http://starchild.gsfc.nasa.gov/docs/StarChild/space_level2/travel.html

For additional details, see the site:
http://www-108.worldbookonline.com/academic/article?id=ar551480

Jeff Silvis, Heather Muise, and Sandy Antunes

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The Question

My students in 4th and 5th grade are wanting to build a cardboard replica of the Friendship 7 capsule which John Glenn went into space with. We need to know its dimensions inside and out. It would also be helpful to know what it was like on the inside so we could see what it felt like to sit in the capsule like John Glenn did. Would you e-mail me that information or tell what resources would have that information?

The Answer

The best place for this information would be the National Air and Space Museum. They have a web site at http://www.nasm.si.edu and they even have links to places where you can ask questions!! (there is also a page of frequently asked questions which should be perused FIRST, of course, just like we have!).

Since the capsule is actually THERE, they are really the best source for this info.

Allie Cliffe (and Tim Kallman)
for the Ask an Astrophysicist team

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The Question

I just want to know how long it took to build the first space ship to the Moon?

The Answer

You can find a lot of interesting facts about the history of manned space (including the Apollo missions to the Moon) at:

http://www-pao.ksc.nasa.gov/history/

and

http://www-pao.ksc.nasa.gov/kscpao/history/apollo/apollo-11/apollo-11.htm

Besides web resources, there are a number of good books about the early space program in your bookstore or local library. "Liftoff" by Michael Collins, an Apollo 11 astronaut, is one that talks not only about the first Moon landing, but about the development of the first "space ships".

Other good books on the subject are "A Man on the Moon" by Andrew Chaikin, "Carrying the Fire" also by Michael Collins, "Moon Shot" by Deke Slayton and Alan Shepherd. There is also a video documentary called "Moon Shot" which covers the development of space ships and the subsequent Moon landing; it is both informative and interesting and has lots of interviews with Mercury, Gemini, and Apollo astronauts.

To answer your question:

Apollo 11 landed on the Moon in 1969, 8 years after President Kennedy's famous speech in 1961 (in which he proposed to send a man to the Moon and return him safely within the decade).

You can also find a history of (manned and unmanned) lunar exploration at:

http://nssdc.gsfc.nasa.gov/planetary/lunar/lunartimeline.html

Best wishes,

Maggie Masetti & Koji Mukai
for Ask an Astrophysicist

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The Question

I'm looking for a picture of the Apollo 15 astronaut dropping the hammer and falcon feather that hit the ground at the same time. Can you help?

The Answer

You can find a picture of this via the Kennedy Space Center's history pages devoted to the Apollo missions. Go to

http://www-pao.ksc.nasa.gov/kscpao/history/apollo/apollo-15/apollo-15-info.htm

and link to one of the image directories. The nasa Photo Id for the picture is S71-43788.

You'll see, unfortunately, that this image is rather fuzzy. But if you look carefully, you can see the hammer and the feather just as they hit the ground. If you need further assistance, you might also try KSC's Public Affairs office. Their web site is at

http://apps.ksc.nasa.gov/edcal/index.cfm

This site contains some additional names, contact numbers and other possible links that you might find useful.

You might also be able to find the picture in astronomy textbooks.

If you're desperate, there is a doctored picture illustrating the same principle in the expanded and illustrated edition of Stephen Hawking's 'A Brief History of Time'. See figure 2.3, but note that it is not a picture from Apollo 15 but maybe from Apollo 11.

Jim Lochner and Allie Cliffe
for Ask an Astrophysicist

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The Question

Was the Apollo 18 rocket flight of 1975 the last rocket to splash down?

The Answer

We assume that you are referring to the Apollo-Soyuz Test Project. Then, yes, it was the last splash-down that we know of. (Assuming that you mean a splash-down of a manned capsule by nasa.) Naturally, there have been many un-manned flights that have landed in the ocean when the flight was over. There are also many books on the space program that you can find at your local library, plus a NASA history home page at

http://www-pao.ksc.nasa.gov/history/.

We do not know if it was the last splash-down by any manned spacecraft, because we are not experts in space history. We suggest that you go to your local library to learn more about this.

Jonathan Keohane and Koji Mukai
for Imagine the Universe!

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The Question

I need all possible information you have on Skylab: its problems, interior, the astronauts who were on it, its take off, design, and any other information you can give me.

The Answer

We have a page on Skylab at:

http://heasarc.gsfc.nasa.gov/docs/heasarc/missions/images/skylab_images.html

I hope this helps.

Good luck,

Jonathan Keohane
for Imagine the Universe!

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The Question

I was wondering if you wouldn't mind sending information about the Challenger (the one that the teacher was in).

The Answer

A place to start is the web page at:

http://www-pao.ksc.nasa.gov/kscpao/shuttle/missions/51-l/mission-51-l.html

Tim Kallman
for the Ask an Astrophysicist team

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The Question

Where can I find information on the Internet regarding the results of the latest Space Telescope repair mission?

The Answer

The place to go visit is the set of "Second Servicing Mission" pages of the Space Telescope Science Institute (STScI):
http://oposite.stsci.edu/pubinfo/sm97/

The Mission Update page contains the latest status of the new instruments (although their description may lead you to think that it is an old page containing only the status of the Shuttle mission/spacewalk).

Koji Mukai
for Imagine the Universe!

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The Question

Do the astronauts have a hard time taking care of the Hubble telescope? Do the astronauts have to change the cameras on the Hubble telescope when the film runs out?

The Answer

The Hubble Space Telescope is run remotely from the ground (In fact, it is run from right here at NASA/Goddard !). It is not run by astronauts, and it does not need to be taken care of by astronauts. The astronauts on the recent space shuttle mission simply replaced some of the instruments. None of the instruments use film. The data is collected electronically and then sent down by satellites to receiving stations on earth.

Jim Lochner
for Imagine the Universe!

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The Question

What is the altitude at which the Space Shuttle orbits?

The Answer

The altitude at which the shuttle orbits depends on its mission. When the Shuttle docks with Mir, it goes up to 390 km (242 statute miles). Columbia, the oldest and heaviest shuttle in the fleet, can't reach that orbit.

David Palmer
for Ask an Astrophysicist

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The Question

How far has a spacecraft ever gone?

The Answer

Voyager 1 is the farthest a space probe -- over 10.4 billion km (over 6.4 billion miles) from the Sun (a bit farther than that from the Earth - in comparison, the Earth is about 0.1 billion miles from the Sun), followed by Voyager 2 -- 8 billion km (5 billion mi.) from the Sun -- as of 1/30/98. Voyager 2 was launched first, in August 1977, followed by Voyager 1 in Sept. 1977, so they've been traveling for over 20 years!
(see: http://voyager.jpl.nasa.gov/)

In addition to Voyager 1 being the farthest working space probe, it just recently became the most distant man-made object, surpassing Pioneer 10. (So, obviously, it's Pioneer 10 and not Voyager 2 that is the 2nd most distant at this time.) See the press release of Feb 13, 1998, available from
http://voyager.jpl.nasa.gov/news/pressrelease2.html.

Jonathan Keohane, Mark Kowitt and Jim Lochner
for Ask an Astrophysicist

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The Question

I think the solution to the exploration of the surface and atmosphere of Mars is in the use of a vehicle capable of flight. Current attempts at the construction of a vehicle to explore the surface have failed to meet expectations. It seems lighter-than-air vehicle would over come the limitations of surface transportation. An RPV (balloon w/ solar powered propulsion) could gather more information from a wider range of sources and possibly return to Earth or a retrievable distance under its own power. What do you think?

The Answer

The idea of using a balloon to study the atmosphere and surface of Mars has a long history. In 1987, the Planetary Society began advocacy and development efforts which led to the acceptance of a Mars Balloon for the Russian Mars 96 mission. Although the Russian space agency later pulled out of the project because of operational and funding problems, the concept has strong support and will probably be used on some future Mars mission.

I doubt if Mars balloons will be given a sample return capability. Sample return is difficult and will be applied mainly to returns from the surface, where the science is more compelling and the engineering much simpler.

An interesting byproduct of all the attention that has been given to the Mars balloon concept is an increased interest in long-duration balloon flights above the Earth! See:

http://asd.gsfc.nasa.gov/docs/balloon/workshop96/

Best wishes,

Paul Butterworth
for the "Ask an Astrophysicist" Team

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The Question

As it is 9 years and 1 week since Voyager left the vicinity of Neptune, I thought I would ask some Voyager questions. Voyager is without doubt the most fantastic probe ever to leave the earth, but what of them now? Are the probes still transmitting receivable data? Where are they in relation to our Solar System? i.e. still within the Heliopause etc.? What is the life expectancy of the on board computers and internal power supplies? Where (roughly) are the probes heading, and once there, will they still have enough power to transmit data? Are any more similar missions planned?

The Answer

The best answer to your question is to direct you to the JPL web site devoted to voyager:

http://voyager.jpl.nasa.gov/

It has the answers to at least some of your questions, and probably more information which you will find interesting. There is also a recent press release which we are appending which you might find interesting.

Tim Kallman and Maggie Masetti
for the Ask an Astrophysicist team

---

Date: Tue, 2 Sep 1997 16:12:38 -0400 (EDT)
From: NASANews@hq.nasa.gov
To: undisclosed-recipients:
Subject: Two Voyager Spacecraft Still Going Strong After 20 Years

Donald Savage
Headquarters, Washington, DC
(Phone: 202/358-1547)

Mary Hardin
Jet Propulsion Laboratory, Pasadena, CA
(Phone: 818/354-5011)

RELEASE: 97-189

TWO VOYAGER SPACECRAFT STILL GOING STRONG AFTER 20 YEARS

Twenty years after their launch and long after their planetary reconnaissance flybys have been completed, both Voyager spacecraft are now gaining on another milestone -- crossing that invisible boundary that separates our solar system from interstellar space, the heliopause.

Since 1989 when Voyager 2 encountered Neptune, both spacecraft have been studying the environment of space in the outer solar system. Science instruments on both spacecraft are sensing signals that scientists believe are coming from the heliopause -- the outermost edge of the Sun's magnetic field that the spacecraft must pass through before they reach interstellar space.

"During their first two decades, the Voyager spacecraft have had an unequaled journey of discovery. Today, even though Voyager 1 is now more than twice as far from the Sun as Neptune, their journey is only half over, and more unique opportunities for discovery await the spacecraft as they head toward interstellar space," said Dr. Edward Stone, the Voyager project scientist and director of NASA's Jet Propulsion Laboratory, Pasadena, CA. "The Voyagers owe their ability to operate at such great distances from the Sun to their nuclear electric power sources which provide the electrical power they need to function."

The Sun emits a steady flow of electrically charged particles called the solar wind. As the solar wind expands supersonically into space, it creates a magnetized bubble around the Sun, called the heliosphere. Eventually, the solar wind encounters the electrically charged particles and magnetic field in the interstellar gas. The boundary created between the solar wind and interstellar gas is the heliopause. Before the spacecraft reach the heliopause, they will pass through the termination shock -- the place where the solar wind abruptly slows down from supersonic to subsonic speed.

Reaching the termination shock and heliopause will be major milestones for the spacecraft because no one has been there before and the Voyagers will gather the first direct evidence of their structure. Encountering the termination shock and heliopause has been a long sought-after goal for many space physicists, and exactly where these two boundaries are located and what they are like still remains a mystery.

"Based on current data from the Voyager cosmic ray subsystem, we are predicting the termination shock to be in the range of 62 to 90 astronomical units (AU) from the Sun. Most 'consensus' estimates are currently converging on about 85 AU. Voyager 1 is currently at about 67 AU and moving outwards at 3.5 AU per year, so I would expect crossing the termination shock sometime before the end of 2003," said Dr. Alan Cummings, a co-investigator on the cosmic ray subsystem at the California Institute of Technology.

"Based on a radio emission event detected by the Voyager 1 and 2 plasma wave instruments in 1992, we estimate that the heliopause is located from 110 to 160 AU from the Sun," said Dr. Donald A. Gurnett, principal investigator on the plasma wave subsystem at the University of Iowa. (One AU is equal to 93 million miles (150 million kilometers), or the distance from the Earth to the Sun.)

"The low-energy charged particle instruments on the two spacecraft continue to detect ions and electrons accelerated at the Sun and at huge shock waves, tens of AU in radius, that are driven outward through the solar wind. During the past five years, we have observed marked variations in this ion population, but have yet to see clear evidence of the termination shock. We should always keep in mind that our theories may be incomplete and the shock may be a lot farther out than we think," said Dr. Stamatios M. Krimigis, principal investigator for the low energy charged particle subsystem at The Johns Hopkins University Applied Physics Laboratory.

Voyager 2 was launched first on Aug. 20, 1977, and Voyager 1 was launched a few weeks later on a faster trajectory on Sept. 5. Initially, both spacecraft were only supposed to explore two planets -- Jupiter and Saturn. But the incredible success of those two first encounters and the good health of the spacecraft prompted NASA to extend Voyager 2's mission to Uranus and Neptune. As the spacecraft flew across the solar system, remote-control reprogramming has given the Voyagers greater capabilities than they possessed when they left the Earth.

There are four other science instruments that are still functioning and collecting data as part of the Voyager Interstellar Mission. The plasma subsystem measures the protons in the solar wind. "Our instrument has recently observed a slow, year-long increase in the speed of the solar wind which peaked in late 1996, and we are now observing a slow decrease in solar wind velocity," said Dr. John Richardson, of the Massachusetts Institute of Technology, principal investigator on the plasma subsystem. "We think the velocity peak coincided with the recent solar minimum. As we approach the solar maximum in 2000, the solar wind pressure should decrease, which will result in the termination shock and heliopause moving inward towards the Voyager spacecraft."

The magnetometer instrument on board the Voyagers measures the magnetic fields that are carried out into interplanetary space by the solar wind. The Voyagers are currently measuring the weakest interplanetary magnetic fields ever detected and those magnetic fields being measured are responsive to charged particles that cannot be detected directly by any other instruments on the spacecraft, according to Dr. Norman Ness, principal investigator on the magnetometer subsystem at the Bartol Research Institute, University of Delaware.

Other science instruments still collecting data include the planetary radio astronomy subsystem and the ultraviolet spectrometer subsystem.

Voyager 1 encountered Jupiter on March 5, 1979, and Saturn on Nov. 12, 1980, and then, because its trajectory was designed to fly close to Saturn's large moon Titan, Voyager 1's path was bent northward by Saturn's gravity sending the spacecraft out of the ecliptic plane, the plane in which all the planets but Pluto orbit the Sun. Voyager 2 arrived at Jupiter on July 9, 1979, and Saturn on Aug. 25, 1981, and was then sent on to Uranus on Jan. 25, 1986, and Neptune on Aug. 25, 1989. Neptune's gravity bent Voyager 2's path southward sending it also out of the ecliptic plane and on toward interstellar space.

Both spacecraft have enough electrical power and attitude control propellant to continue operating until about 2020 when the available electrical power will no longer support science instrument operation. Spacecraft electrical power is supplied by Radioisotope Thermoelectric Generators (RTGs) that provided approximately 470 watts of power at launch. Due to the natural radioactive decay of the plutonium fuel source, the electrical energy provided by the RTGs is continually declining. At the beginning of 1997, the power generated by Voyager 1 had dropped to 334 watts and to 336 watts for Voyager 2. Both of these power levels represent better performance than had been predicted before launch.

The Voyagers are now so far from home that it takes nine hours for a radio signal traveling at the speed of light to reach the spacecraft. Science data are returned to Earth in real-time to the 34-meter Deep Space Network antennas located in California, Australia and Spain. Voyager 1 will pass the Pioneer 10 spacecraft in January 1998 to become the most distant human-made object in our solar system.

Voyager 1 is currently 6.3 billion miles (10.1 billion kilometers) from Earth, having traveled 7.4 billion miles (11.9 billion kilometers) since its launch. The Voyager 1 spacecraft is departing the solar system at a speed of 39,000 miles per hour (17.4 kilometers per second).

Voyager 2 is currently 4.9 billion miles (7.9 billion kilometers) from Earth, having traveled 6.9 billion miles (11.3 billion kilometers) since its launch. The Voyager 2 spacecraft is departing the solar system at a speed of 35,000 miles per hour (15.9 kilometers per second).

JPL, a division of the California Institute of Technology, manages the Voyager Interstellar Mission for NASA's Office of Space Science, Washington, DC.

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The Question

I have heard that nasa will be Launching a Nuclear Rocket which contains a fuel in it that could possibly lead to death of Thousands of Innocent Floridians. No one has the Right to Murder Innocent people for science. That is wrong. I'm sorry if I have the story wrong, but this is what I have heard. I deeply believe that this is a Huge mistake and should not happen. Please tell me what is going on.

The Answer

The upcoming Cassini mission to Saturn contains plutonium to power some of the scientific instruments on board Cassini. Plutonium is very toxic, but every precaution has been taken to ensure that the chance of any significant threat to humans will be very small even in the worst case scenario. The plutonium is in devices called radioisotope thermoelectric generators (RTGs) and in fact 23 NASA missions have been flown with RTGs on board. The current design of the RTG has been on two space missions which have had mishaps (from other causes) causing the the RTGs to return to Earth. One spacecraft fell into the ocean during a launch accident. The RTG was recovered from the ocean floor with no escape of radiation, and it was later re-used. Apollo 13's lunar module was carrying an RTG. After the accident the lunar module had to re-enter Earth's atmosphere at high velocity and fall into the ocean, but no radiation release was observed.

You may want to check out JPL's web pages on Cassini,

http://saturn.jpl.nasa.gov/.

Also attached below is a press release explaining that other government agencies have given their approval for the mission. For more information, there are links concerning this (and all other) NASA missions on the NASA WWW page at http://www.nasa.gov

Andy Ptak, David Palmer, Gail Rohrbach and Allie Cliffe
for the Ask an Astrophysicist Service

---

Douglas Isbell/Don Savage
Headquarters, Washington, DC
(Phone: 202/358-1547)

Matthew Donoghue
Department of Energy, Washington, DC
(Phone: 202/586-0619)

October 3, 1997

RELEASE: 97-225

NASA RECEIVES APPROVAL TO LAUNCH CASSINI MISSION

NASA today received formal approval from the White House Office of Science and Technology Policy (OSTP) to proceed toward the launch of the robotic Cassini mission to explore Saturn and its moon Titan.

"NASA and its interagency partners have done an extremely thorough job of evaluating and documenting the safety of the Cassini mission. I have carefully reviewed these assessments and have concluded that the important benefits of this scientific mission outweigh the potential risks," said OSTP Director Dr. John H. Gibbons, who signed the launch approval.

NASA Administrator Daniel S. Goldin said, "I am confident in the safety of the Cassini mission, and I fully expect that it will return spectacular images and scientific data about Saturn, in the same safe and successful manner as the Voyager, Galileo and Ulysses missions."

White House launch approval is required by presidential directive due to the type of power source used to provide electrical power for the Cassini spacecraft and its scientific instruments, and the heater units that it carries to keep the spacecraft's instruments and electronics warm in deep space.

The Radioisotope Thermoelectric Generators (RTGs) and Radioisotope Heater Units used to power Cassini and keep its internal systems warm have been used in previous NASA missions ranging from Apollo to Galileo, and have been approved by five previous administrations ranging from Nixon to Bush. RTGs produce power by the heat generated through the natural radioactive decay of non-weapons grade plutonium dioxide, which is transformed into electricity by solid-state thermoelectric converters.

Before Administrator Goldin sent the request for launch approval to OSTP, two separate processes were completed to address the environmental and safety aspects of the mission. NASA completed an Environmental Impact Statement in June 1995 and a supplement in June 1997, as required by the National Environmental Policy Act and NASA policy.

Consistent with long-standing Presidential policy, the Department of Energy (DOE) prepared over the past seven years a comprehensive Safety Analysis Report. In addition, an Interagency Nuclear Safety Review Panel, including safety experts from DOE, NASA, the Department of Defense (DOD), the Environmental Protection Agency (EPA), and a technical advisor from the Nuclear Regulatory Commission conducted a comprehensive evaluation of the safety analysis. This panel was supported by over 50 scientific experts from academia and industry.

DOD, EPA and DOE have written to the NASA Administrator confirming that, in their view, the safety analysis conducted for the mission is comprehensive and thorough.

Cassini is a cooperative endeavor of NASA, the European Space Agency (ESA) and the Italian Space Agency, or Agenzia Spaziale Italiana. The mission will send a sophisticated robotic spacecraft, equipped with 12 scientific experiments, to orbit Saturn for a four-year period and study the Saturnian system in detail. The ESA- built Huygens probe that will parachute into Titan's thick atmosphere carries another six scientific instrument packages.

Saturn is the second-largest planet in the solar system and is made up mostly of hydrogen and helium. Its placid-looking, butterscotch-colored face masks a windswept atmosphere where jet streams blow at 1,100 miles per hour and swirling storms roil just beneath the cloud tops. Previous spacecraft passing by Saturn found a huge and complex magnetic environment, called a magnetosphere, where trapped protons and electrons interact with each other, the planet, rings and surfaces of many of the moons.

Although it is believed to be too cold to support life, haze- covered Titan is thought to hold clues to how a primitive Earth evolved into a life-bearing planet. It has an Earth-like, nitrogen- based atmosphere and a surface that many scientists believe probably features chilled lakes of ethane and methane. Scientists believe that Titan's surface is probably coated with the residue of a sticky brown organic rain.

The launch of Cassini aboard a Titan IV-B/Centaur launch vehicle is scheduled for 4:55 a.m. EDT on October 13 from Cape Canaveral Air Station, FL. An on-time launch will deliver the Cassini mission to Saturn almost seven years later on July 1, 2004. Cassini's primary mission concludes in July 2008.

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The Question

My friend and I were wondering how do scientists get the space probes that search other planets, like Voyager etc. through the asteroid belt? If the probes went through the asteroid belt wouldn't they get hit by a rock and get damaged?

The Answer

Planetary probes can pass through the asteroid belt without any problem because, unlike in the movies, there is really a LOT of space between asteroids. More than 7000 have been discovered and several hundred new ones are found every year. There are probably millions of asteroids of various size, but those in the asteroid belt are spread over a ring that is more than a billion kilometers in circumference, more than 100 million kilometers wide, and millions of kilometers thick. For more information, you can look at http://nineplanets.org/asteroids.html

Thanks for your questions

Eric Christian
for Ask an Astrophysicist

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The Question

With government spending cuts, is it possible that nasa could offer commercial flights into orbit to the average citizen? Also I've read that Ron Howard took a flight on "the vomit comet" aircraft to research the film Apollo 13, and he and some other actors flew to altitudes where near weightlessness was achieved. How much did it cost and could I do the same?

The Answer

Your first question is about NASA, government cuts, and the possibility of commercial space flight for the average citizen. We are not aware of any effort by NASA to allow citizens in space other than the trained astronauts selected by NASA. The only effort we are aware of to put citizens in space is a program called Hankoh-Maru, a theoretical concept study in space tourism by the Japanese space program. You can learn more about Hankoh- Maru from the November 1996 issue of Aerospace America.

Your second question is about "the vomit comet" and its use in filming Apollo 13. The "vomit comet" is a NASA aircraft which is flown to high altitude and then sent into a ballistic parabolic dive, which it pulls out of at a much lower altitude. People in the plane "free-fall" during the dive, temporarily simulating zero g. The rather descriptive name for the plane comes from the common experience of stomach queasiness many people feel in free-fall. You may experience the same queasiness when you ride on a roller coaster ... which often has a ballistic arc much like the NASA aircraft only lasting a much shorter time. If you like free-fall, it is easy to experience it. Bungee jumping and sky diving are other ways.

The zero-g simulation aircraft is used by NASA for fairly specific purposes. Most often it is included as part of zero-g training and testing for astronauts and for experiment packages to fly in space, especially industrial applications which intend to use zero-g environment to grow ultra-pure crystals and such. The minute or so of zero-g which occurs allows testing of equipment to find and fix problems prior to actual use in space. It is not a service available to the general public.

The Apollo 13 film crew obtained special permission (and undoubtedly paid a good deal for the services) to film zero-g sequences in the movie. The realistic portrayal of zero-g in the film was made possible by filming in one minute segments inside the aircraft....and a realistic portrayal of space can only serve to help NASA achieve its goal of public space science and exploration education. Our library does not subscribe to Life magazine, but we recall that there is a good article on the filming of Apollo 13 and specific mention of the filming on the "Vomit Comet" around the time the movie came out. Check issues from July or maybe even June of 1995.

Jesse Allen, Gail Rohrbach, and Laura Whitlock
for "Ask an Astrophysicist"

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The Question

Will it ever be possible for a space ship to have gravity while in space?

The Answer

Gravity is the least understood of the four basic forces in Physics (Gravity, Electricity & Magnetism, and the Strong and Weak Nuclear Forces). We do know how to describe it, and understand it seems a property associated with mass. There is no known mechanism at this point for artificially creating gravity, other than having a suitably large mass at hand.

However, that's not to say you could not "fake it", so to speak. You could keep a rocket constantly accelerating at 9.81 meters per second per second, and then flip the rocket around halfway to your destination and constantly accelerated in the opposite direction the rest of the way. Anyone in the space vehicle would feel as if they were experiencing gravity on Earth, except for a few dizzy moments when the spaceship gets flipped around. However, there's a little problem of having to have fuel enough to keep a rocket firing at that high a rate the whole time. Even the largest rockets nasa and the Russian Space Agency have will only burn for a few minutes before running out of fuel: the rest of the journey for space vehicles is done "coasting" to their destination and then using much smaller rockets to adjust their speed to slow down or change their orbit.

Another "trick" would be to make the entire space vehicle spin. Imagine a ball on a string: you can twirl it around and feel the string tugging on your arm. If you have a bucket of water on a string, you can twirl it around and if you twirl it around fast enough, the water stays in the bucket even if you spin it so it goes upside down during part of the swing. The same thing could be done in space: take two space vehicles and connect them on a tether and make them swing around each other to generate a sense of gravity. Theoretically, this is a very attractive idea; early tests with Gemini XI and XII showed that, while it was possible to generate microgravity (too weak for the astronauts to feel), stationkeeping of two tethered spacecrafts was very difficult. NASA has also flown a couple of shuttle missions attempting to deploy a tethered satellite. There were several goals with the tether system, but at least one was to work out how to deploy tethered systems in space.

Jesse Allen
for Ask an Astrophysicist

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The Question

Is a manned trip to Mars and back possible very soon?

The Answer

President Bush directed nasa to plan a human landing on Mars by the year 2020. The Space Exploration Initiative that resulted was soon abandoned though. The current NASA manned space programs (space shuttle, joint operations with the Russians on Mir, and the new International Space Station) are not explicitly directed towards putting humans on Mars. There are a number of very serious challenges that would require solutions to make such a journey possible, not the least of which is the tremendous cost involved. Given the current emphasis on cost cutting, putting humans on Mars seems an unlikely goal for the near future.

Among the problems that would need to be solved before a human trip to Mars could take place would be:

1/ It's a two year round trip to Mars by a direct minimum energy orbit each direction, with a few month's wait at Mars as well. The current world record for the longest duration in space is about half that time and there are serious medical problems the Russian cosmonauts have encountered when they return to Earth (American astronauts have only very recently started long stays in space on the Mir space station and the current record of six months set by Shannon Lucid last year: see http://imagine.gsfc.nasa.gov/news/28oct96.html). The medical problems of returning to Earth will require solutions which research with Mir and the International Space Station might shed light on.

2/ Fuel. To send people to Mars, you'll need to take everything they need to get there, and live in space, for two years. That's a lot of material! A direct approach like that used for the Apollo missions to get to the Moon (take everything you need and throw it away in pieces as it gets used up) won't work for Mars: the mass required to get to Mars and back is well beyond the capability of even the most powerful rockets ever made (which happen to be the Saturn V rockets used for Apollo). So it certainly require assembly of the parts in space, with multiple launches to get the components put up there. This kind of assembly in space has been done essentially only once before with the construction of the Mir Space Station. The new International Space Station will also be assembled in pieces in low earth orbit.

3/ Martian environment. What's it going to be like there? Before putting astronauts on the Moon, NASA needed to explore the Moon in great detail with probes sent to the Moon to image it, map its gravitational field, study its surface, etc. NASA and the Russian Space Agency are both sending a number of probes to Mars in the coming years to explore the planet. Mars Pathfinder and Mars Global Surveyor are only the first in a fleet of probes heading to Mars in the next decade. Answers from these missions about Martian weather and conditions will be necessary to go to Mars.

So although NASA and other space agencies around the world may not be currently explicitly trying to send people to Mars, many of the current space activities will be necessary parts of any effort to go to Mars.

Jesse Allen
for "Ask an Astrophysicist"

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The Question

Is it possible that in the future we will live on another planet?

The Answer

It's hard to say whether in the future we will live on another planet. The Earth provides for us the right balance of necessary conditions so that we can live in reasonable comfort without artificial aid. Through advances in technology, we might certainly be able to create an environment in which we could live on almost any other planet (e.g. a space suit is a miniature of such an environment). But whether another planet out in space harbors conditions similar enough to earth that we would need little or no "artificial environment" is unknown. We might think that such another planet ought to exist, but it doesn't mean that it necessarily does.

The role of science is to take us from what we think **might** be true to what really is true and possible. In order for us to live on another planet, we must first find other planets (this is an active field of research that astronomers are now making great progress in), determine whether they are suitable for us, and then travel to them. All of these require significant advances in our knowledge and technology. This is not to say that it is beyond our capabilities, but rather to consider what would need to be done to do it.

It is a question worth pondering, and by thinking about it we can certainly learn many exciting things along the way.

I hope this helps,

Jim Lochner
for Imagine the Universe!

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The Question

Within the next 50 years will it be possible to travel to other stars within our own galaxy? ...outside our galaxy? ...ignoring money, what are the major limiting technologies? Thanks for whatever information you can supply!!

The Answer

It will not be possible to send people to other stars within 50 years. The nearest star to the Sun is about 4.3 light years away, so even if we had a spaceship which could travel at a tenth of the speed of light, we would have to leave in the next seven years in order to get there in time. Right now, we don't even have a space ship which could get to the Moon.

In 50 years, if we work hard, we might be able to build robotic probes which can get to the nearest stars a few decades later. One suggested probe is StarWisp
http://wwwssl.msfc.nasa.gov/newhome/headlines/prop08apr99_1.htm

which weighs about half an ounce--not much room for a passenger and life support.

The main problem is that of propulsion. Even using hydrogen fusion, we would need hundreds or thousands of times as much fuel as payload in order to get up to a few percent of lightspeed. Compared to that, the problems of maintaining a life-support system for the decades that the trip will take are trivial engineering details.

As for intergalactic travel, even the over-optimistic Star Trek: Voyager using hyperdrive requires a lifetime of travel just to get from the far side of the galaxy to here. The Magellanic Clouds are only 160,000 light years away, but the nearest big galaxy, in Andromeda, is a couple of million light years away.

Without major breakthroughs in physics, interstellar travel will always require heroic efforts over decades or centuries.

More information is available at
http://www.lerc.nasa.gov/WWW/PAO/warp.htm

David Palmer
for Ask an Astrophysicist

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