Slashdot Mirror

If we can monitor things so closely, can anyone explain to me why we can't watch iraq, or afganastan for movement by terrorists?

The higher the resolution of the data, the less frequently it can be obtained.

Images of the earth at 1-km resolution are acquired by geosynchronous satellites about every 15 minutes (e.g. GOES).

Images of the earth at 250-m resolution are acquired about once a day (e.g. MODIS)

Images of the earth at 15-m resolution are acquired as often as once every two weeks (e.g. LandSat 7

Data from the above three satellite instruments are publicly available. You could create your own database, if you had the bandwidth and storage capacity.

There are other satellite instruments that take much higher-resolution images, but these are generally "targeting" instruments - you need to give them specific locations to capture, because there isn't enough storage and bandwidth to cover the entire earth regularly at that resolution. It typically takes weeks or months (if not longer) to create a high-resolution mosaic of something like a city.

Note, though, that geosynchronous satellites are the only ones that could take continuous images of a particular location, and they're too far away to take high-resolution images. High-resolution imagers have to be taken from lower orbit, which means that the satellites are moving, and thus they can't stay focused on the same spot for very long.

Also, many high-resolution images are taken from aircraft, not satellites. This is a convenient way to get high-resolution images of major cities, but this doesn't help us with reconnaisance in Iraq or Afghanistan, for obvious reasons...

If we can monitor things so closely, can anyone explain to me why we can't watch iraq, or afganastan for movement by terrorists?

The higher the resolution of the data, the less frequently it can be obtained.

Images of the earth at 1-km resolution are acquired by geosynchronous satellites about every 15 minutes (e.g. GOES).

Images of the earth at 250-m resolution are acquired about once a day (e.g. MODIS)

Images of the earth at 15-m resolution are acquired as often as once every two weeks (e.g. LandSat 7

Data from the above three satellite instruments are publicly available. You could create your own database, if you had the bandwidth and storage capacity.

There are other satellite instruments that take much higher-resolution images, but these are generally "targeting" instruments - you need to give them specific locations to capture, because there isn't enough storage and bandwidth to cover the entire earth regularly at that resolution. It typically takes weeks or months (if not longer) to create a high-resolution mosaic of something like a city.

Note, though, that geosynchronous satellites are the only ones that could take continuous images of a particular location, and they're too far away to take high-resolution images. High-resolution imagers have to be taken from lower orbit, which means that the satellites are moving, and thus they can't stay focused on the same spot for very long.

Also, many high-resolution images are taken from aircraft, not satellites. This is a convenient way to get high-resolution images of major cities, but this doesn't help us with reconnaisance in Iraq or Afghanistan, for obvious reasons...

Gravity will pull it closer to the sun, but it will not pull it into the sun. If you drop your speed relative to the sun, all you will get is a closer orbit around the sun. Witness the wacky path we took with Mariner 10 and the even longer and even crazier path we're using for MESSENGER. And that's just to get to Mercury.

The grandparent is right. You basically need a velocity of about 31.8 km/sec [Gurzadyan 1996, Theory of Interplanetary Flights, pp. 58-60] to actually get to the sun from Earth, unless you use a gravity assist from other solar bodies.

Orbits just don't "decay" in the sense that radioactive materials decay. Some are stable, some are instable, and some are affected by interactions with atmospheres or collisions with other particles. All are affected (however slightly) by the gravitation of everything else. This makes long term precise orbital calculations in the real world very difficult. Bank shotting radioactive material around the solar system sounds pretty dangerous to me. Even if we had rocket motors that could get us to Sol directly, there's a chance you could miss and put the stuff on a highly elliptical orbit with aphelion near the Earth's orbit. We could shoot ourselves nicely with that.

ummm.... worldwind from NASA is free and seems to be the same thing...

Mostly those big blue areas. Until recently, I know we had explored less of the ocean floor than of the Moon; that may still be true. Either way, the deep oceans are really the least examined and least-visted areas of Earth.

On land, this photograph will probably give you a good idea where to start looking. The places without lights are probably pretty seldom visited--mountains, deserts, and tundra.

Small correction, Clark said that it would be 50 years after everyone stopped laughing, not 10.

http://science.nasa.gov/headlines/y2000/ast07sep_1 .htm

Nylon is hardly the strongest stuff we have.

Carbon nanotubes are theorised to achieve 130-150 Gpa
http://www.nas.nasa.gov/About/Education/SpaceSettl ement/Nowicki/SPBI1MA.HTM

Still a way off from producing it though.

NASA didn't used an ion drive for the Cassini mision. It was a regular chemical rocket with gravity assist to get to Saturn. NASA would not have risked such an expensive mission to unproven ion drives. There is also the little fact that Deep Space 1 was the first spacecraft to actually use ion propulsion to reach another planetary body and was launched Oct. 24, 1998 while Cassini was launched late 1997 I think it was October 13th. I would have been _really_ stupid of NASA to use an ion engine on Cassini when they were never tested yet. A quote from the Cassini mission overview

After a seven-year voyage that includes four gravity-assist maneuvers, Cassini will enter Saturn's orbit in July of 2004.

NASA didn't used an ion drive for the Cassini mision. It was a regular chemical rocket with gravity assist to get to Saturn. NASA would not have risked such an expensive mission to unproven ion drives. There is also the little fact that Deep Space 1 was the first spacecraft to actually use ion propulsion to reach another planetary body and was launched Oct. 24, 1998 while Cassini was launched late 1997 I think it was October 13th. I would have been _really_ stupid of NASA to use an ion engine on Cassini when they were never tested yet. A quote from the Cassini mission overview

After a seven-year voyage that includes four gravity-assist maneuvers, Cassini will enter Saturn's orbit in July of 2004.

NASA didn't used an ion drive for the Cassini mision. It was a regular chemical rocket with gravity assist to get to Saturn. NASA would not have risked such an expensive mission to unproven ion drives. There is also the little fact that Deep Space 1 was the first spacecraft to actually use ion propulsion to reach another planetary body and was launched Oct. 24, 1998 while Cassini was launched late 1997 I think it was October 13th. I would have been _really_ stupid of NASA to use an ion engine on Cassini when they were never tested yet. A quote from the Cassini mission overview

After a seven-year voyage that includes four gravity-assist maneuvers, Cassini will enter Saturn's orbit in July of 2004.

"This flight is a key milestone and a major step toward the future possibilities for producing boosters for sending large and critical payloads into space in a reliable, safe, inexpensive manner,"

I think I got it. From this page: http://www.grc.nasa.gov/WWW/K-12/airplane/sound.ht ml Speed of sound is still 684 mph at 100,000 ft

START SHAMELESS PLUG

Many reasons have already been mentioned in this thread so I won't reiterate. However, here's my group at NASA JPL that's directly involved with this experiement. A lot more information can be found there that directly answers your questions as well as those of others.

END SHAMELESS PLUG

The magnetic poles have been measurably accelerating over the last several years, from ~10 kmh to ~40kmh, maybe it's time. It's moving north though. I recently did some research on just this subject, and it's quite suprising just how little is known. We don't know for sure why the Earth has a magnetic field, we don't know why it flips, and we don't know what it will mean when it does happen.

Some interesting info

P.S. To the moderators; A post that starts with 'I wonder if' might be '+1 interesting', but is rarely '+1 informative'

The last flight was 11 seconds. Haven't heard on this one yet. See here.

By the way (and massively OT), doesn't a "Guinness Record" sound like something you'd like to break yourself, at least if it involved consumption?

The B-52B (tenth off the assembly line) first flew on June 11th, 1955 and among other things, has carried the X-15, Shuttle solid rocket booster, and finally the X-43A (on the same pylon as used by the X-15). Read more about the ol' BUFF at NASA.

NASA launched Deep Space 1 back in 1998.

Welcome to the party.

From the article:
April 6, 1999: The ion propulsion system on Deep Space 1 is the culmination of over 50 years of development on electric engine systems in space. Launched on Oct. 24, 1998, Deep Space 1 will be the first spacecraft to actually use ion propulsion to reach another planetary body.

This 1 minute, 16 second narrated movie provides an overview of the X-43A as it prepares for a Mach 10 flight.

2. The ESA did _not_ come up with an ion propulsion system. NASA had an ion propulsion system back in 1998 that was used on Deep Space 1. This is just the ESA continuing what NASA has done.

However, it would be quite useful to use this technology to bring cargo to the Moon for possible astronauts to use. For instance, it's possible to deploy an entire habitat--crew quarters, energy producer, perhaps even in-situ resource production ("mining" water-ice for oxygen and hydrogen to feul your return vehicle)--all before we launch humans on a high-energy tracjectory that will get them there in three days, thus avoiding high radiation exposure.

You could do similar things with Mars. Here's a reference done by the Revolutionary Aerospace Systems Concepts part of NASA:

OASIS

It will take a suite of technologies to get safely to other planets, and possibly another suite of technologies to get back.

It'll be interesting to see, if the Pluto probe ever flies, whether that uses ion propulsion. An ion drive could really make a difference on such a long-haul flight.

My data is in the final stages of being bundled onto a spaceship.

Its due to be launched on 30th December this year, and in August 2005 will be sent crashing into a Comet!

I have encoded my lifes work into a hash which remarkably is the same as an ASCII string containing the names of my family.

More info here: http://deepimpact.jpl.nasa.gov/mission/index.html

How do we justify a $1.6B repair for a device that originally cost $1.5B. Seems we could design and launch a much improved model for the same amount.

We are going to design and launch a much improved space telescope for considerably less than that amount.

However, Hubble has incredible public relations value for NASA. So they're going to try to hang onto it as long as they possibly can, cost be damned.

• Observatory (Calibration, Focal Plane, Telescope, Cross-Instrument Issues)
  
• ACS (Advanced Camera for Surveys)
  
• FGS (The Fine Guidance Sensors)
  
• NICMOS (Near Infrared Camera and Multi Object Spectrometer)
  
• STIS (Space Telescope Imaging Spectrograph)
  
• WFPC2 (The Wide Field Planetary Camera 2)

• Near Infrared Camera (NIRCam)
  
• Mid Infrared Instrument (MIRI)
  
• Near Infrared Spectrograph (NIRSpec)
  
• Fine Guidance Sensor (FGS)

How do we justify a $1.6B repair for a device that originally cost $1.5B. Seems we could design and launch a much improved model for the same amount.

3.1415926535897932384626433832795

sqrt(163) ~=
12.7671453348037046617109520097808923473823637 8030 12588512126029838487261728902392595594234838675318 724

pi ~=
3.141592653589793238462643383279502884197169399375 10582097494459230781640628620899862803482534211706 79

sqrt(163) * pi ~=
40.1091699911325197553500836229041400539005348 1224 58734406107015404701087892483085085878768851896494 372

e ~=
2.718281828459045235360287471352662497757247093699 95957496696762772407663035354759457138217852516642 74

e ^ (sqrt(163) * pi) =
262537412640768743.9999999999992500725971981856 888 79353856337336990862707537410378210647910118607312 6534265238592035364

a Star Trek-style thruster

Had the ion drive fallen just 5 per cent short of maximum thrust, Smart-1 could have collided with the Moon.

They work by using electricity from solar panels to charge atoms of the noble gas xenon, which are then fired into space at 1,000mph to power the probe.

This stream of ions accelerates Smart-1 at just 0.2millimetres per second.

In space, this builds up over time to generate speeds of up to 10miles per second, or 36,000mph.

Why newspapers publish drivel like this, I'll never know. If it was hard to get right you wouldn't have amateurs fisking this stuff on Slashdot!

Here it is. My kids are still fascinated by this (come to think of it, so am I). Just how fast can you make it go before the wheel flies right off or you get Carpal Tunnel Syndrome?

It is well known that planets do radiate their own energy,s ome of it left over from the formation of the planets. I've often wondered what would happen to Earth if Geothermal energy were deployed on massive scales. If you think of the earth's crust as an insulating blanket, then every whole punched into it is letting the heat out where it can radiate into space. Natural volcanos are one thing, but I wonder what effect massive geothermal deployment would have. Would tha mantle cool down and become less molten or even solid, slowing down plate tectonics?

I know you were just being facetious, but the NASA budget is here.

NASA cost $25bn last year. That means the average cost to taxpayers was $191.24. However, for the bottom 95% of the population, the cost came out to less than $95.62 for the year.

Well I think for now the main goal of scramjet technology is a better stage one boost to space. I've always felt that space travel will remain impractical as long as the main way of getting there is to strap a bomb to yourself and hope it explodes slowly. And solving the boost to space problem will go a long way towards making space commercially viable.

But there is hope for over-land super sonic flight some day. http://www.dfrc.nasa.gov/Education/Educator/Resear chEducation/ResearchOportunities/SSB.html/

Well, NASA stands for National Aeronautics and Space Administration; this is well within the original (1915) charter of the organization, which was called the National Advisory Committee for Aeronautics (NACA) before space exploration was added to their role along with the name change in 1958.

Besides, this project is in the tradition of the X-1 thru the X-15, all NASA projects, IIRC. NASA drives the research, but it's private industry (Lockheed, Douglas-Martin, Boeing) that figures out how to build 'em, and we end up riding in better airliners, eventually.

Tests were devised in which tanks containing liquid hydrogen under pressure were ruptured. In many cases, the hydrogen quickly escaped without ignition. The experimenters then provided a rocket squib (a small powder charge) to ignite the escaping, hydrogen. The resulting fireball quickly dissipated because of the rapid flame speed of hydrogen and its low density. Containers of hydrogen and gasoline were placed side by side and ruptured. When the hydrogen can was ruptured and ignited, the flame quickly dissipated -, but when the same thing was done with gasoline, the gasoline and flame stayed near the container and did much more damage. The gasoline fire was an order of magnitude more severe than the hydrogen fire. The experimenters tried to induce hydrogen to explode, with limited success. In 61 attempts, only two explosions occurred and in both, they had to mix oxygen with the hydrogen. Their largest explosion was produced by mixing a half liter of liquid oxygen with a similar volume of liquid hydrogen. Johnson and Rich were convinced that, with proper care, liquid hydrogen could be handled quite safely and was a practical fuel-a conclusion that was amply verified by the space program in the 1960s. At the time, however, Johnson and Rich filmed their fire and explosion experiments to convince doubters.

The confidence of Johnson and Rich in hydrogen handling was not always shared by their hydrogen consultant, Russell Scott, who was often amazed at what he saw going on in the test areas of Fort Robertson.14 The facility, however, was well equipped with an explosion-proof electrical system, non-sparking safety tools, hydrogen sniffers or monitors, and other safety devices. In the three years of work and the handling of thousands of liters of liquid hydrogen, there was not a single accident caused by hydrogen. There was, however, one close call. In keeping with Kelly Johnson's philosophy of austerity, the ovens used for simulating hot wing temperatures of Mach 2.5 flight were made partially of wood. There were five such ovens, and early one morning, about 2 a.m., one of them caught fire. The Skunk Works personnel, including Rich, were summoned because the fire department could not be called, for security reasons. At the time there were 2000 liters of liquid hydrogen stored in the area and Rich decided that the best course of action was to dump the liquid hydrogen on the ground. It was winter and very humid; the cold hydrogen quickly filled the revetment with fog about five feet thick. Rich and about two dozen other people were in the revetment and all they could see of each other were their heads, an eerie sight. Luckily, the hydrogen did not ignite.

For FY 2002 and FY 2003, The X-43A program only cost a combined $52 M; the total budget for the project is $227 Million.

Forest cover is 3/4ths of what it was in 1630. (Powell)

"The forest cover in the U.S. has actually increased in the last 100 years" Note also the climate has been altered as the central prairie has been replaced by farmland...and erosion control effects.

"created" != "transformed"

It's called the law of conservation of energy

Same for me at NASA's Mission to Planet Earth - EOSDIS project http://spsosun.gsfc.nasa.gov/eosinfo/Welcome/index .html.

Amazing how fast a cluster of Cray YMPs can execute "Hello world"!

You have forgotten the second law of thermodynamics.

No, I haven't forgot it. My point was that 100% of a given quantity of matter may be transformed into energetic particles (e.g. photons, pions, beta radiation, etc.) without violating thermodynamics. Keep in mind that thermodynamics also states that energy and matter may NOT be created or destroyed. It may only be converted from one form to another.

The reason why there are losses in a system is that a certain amount of heat will be lost in a process due to the fact that heat travels from a warmer body to a colder one. The closer the colder body is to the temperature of the warmer body, the more energy is lost in the transferance. Once the temperatures are equalized (i.e. complete entropy), there is no way of extracting more energy from the system. The system can only be disturbed by adding energy from outside the system. Eventually, our Universe (the largest system) will reach complete entropy and there will be nothing but equally distributed particles with equal amounts of energy.

Some energy will always be lost, and because fission/nuclear decay. itself does not completely destroy an atom, merely reduce it to smaller parts that are often radioactive themselves, you will always wind up with a huge load of useless radioactive crap with enormous half lives.

The remainder is left because fission is not an efficient process, not because of thermodynamics. You see, fission is the result of an atom becoming too heavy. When it gets too heavy, it collapses in on itself and splits into several smaller atoms. The energy released by this split causes some of the particles to gain kinetic energy and become independent, as well as cause some particles to become zero mass or low mass particles such as photons. The new atoms that are "created" in this process are what we think of as "waste".

When I say useless, I mean useless in the worst sense of the word.

Fission byproducts are by no means "useless". Americium-241 is used in smoke detectors, Sr-90 and Pu-238 work well in atomic batteries, Pu-239 can be recycled into more fission fuel, CS-137 has been used in hydrologic studies, and Tritium is commonly used for professional "glow-in-the-dark" applications. Carbon-11, Nitrogen-13, Oxygen-15, and Fluorine-18, and many other isotopes have been used as medical tracers.

When I say that stuff is useful, I mean it in the best sense of the word.

The crap that is left over only puts out extremely low quality heat but more than enough radiation to seriously, for lack of a better word, fuck up anything with DNA.

Not all radiation types pose a threat. In fact, low level radiation often doesn't pose a threat at all. Alpha particles can't penetrate the skin, nor can low levels of Beta radiation. Gamma and X-Ray radiation penetrates so well that it's most likely to completely miss your body! Only neutron radiation is a major concern, but that stuff is only produced during fission.

And as of yet there are NO viable ways to store this material for the neccesary period of time.

Again, that stuff is useful. Some of it can be reprocessed into fission fuel, and some of it can be made into products we use every day. (Duck! Your smoke alarm is emitting radiation!) The remaining stuff is miniscule in size, and most likely wouldn't harm anyone.

(Estimated to be about 100,000 years or more.)

Anything that takes 100,000 years to become "not-so-dangerous" is already "not-so-dangerous" as long as it's kept out of the water and food tables.

So no, due to logistical and environmental concerns, nuclear fissions is not a viable answer to our long term energy needs.

Ahem. Nuclear Fission is a fine source of energy with few problems. The primary issue is that advancement and processing techniques have been held back by the fear of "terrorists".

Seriously, why is this being done by NASA? This is a neat thing happening with this guy but don't we have dozens of people who've actually been in space for extended periods of time? Why aren't CAT scans of them enough?

I can't see how this has any practical relevance to the space program from the viewpoint of manned space (we have more than enough data on that front) or unmanned where this is completely unrelated.

What ever happened to NASA being the Aeronautics and Space administration. Wasn't the VSE supposed to put the kibosh on all this science fair side issue stuff? Shouldn't this be relegated to some university psych program with a government grant?

Hmmm, the Shuttle SRBs are one candidate (and an obvious point of comparison, too) - they are only 86 tonnes empty. Big step up to 300 tonnes. Perhaps you could make them lifting bodies or something? Not so much to have them fly/glide home, but at least slow the descent somewhat. Maybe retrorockets to soften the blow.

Orbits do degrade, especially low earth orbits, just look at Hubble, or ISS, which need reboosts every once in awhile.
Low orbit still is subject to significant drag affects of the atmosphere.
There is no good definition of where space starts, usually its considered around 100miles, but the atmosphere extends up to 1000 miles into space. So you can have a vehicle designed to achieve the speed of 2 orbits and not have the energy to achieve more.

NASA's website fucker!

http://visibleearth.nasa.gov/Countries/China/133_8 .html

Specifically, the proposed Jupiter Icy Moons Orbiter mission. Browse the site if you're interested, lots of info there, and linked from there.

The following contains some links to mostly non-technical explanations of planetary roundness. I'd like to point out that part of this explanation, by "Derek Sears, professor of cosmochemistry at the University of Arkansas and editor of the journal Meteoritics and Planetary Science," is wrong. He says "Planets are round because their gravitational field acts as though it originates from the center of the body and pulls everything toward it." But this is a circular argument (pardon the pun). Generally a non-spherically symmetric distribution of matter doesn't have a gravitational field that acts as if it originates from the center of the body (the "center" being the center of mass). Spherically symmetric mass distributions do have this special property, so what Sears really implied is that planets that are already round will have gravitational fields that point towards the object's center of mass. This does absolutely nothing to address cases of objects that deviate from perfect roundness, i.e. all celestial bodies. This explanation by Dr. Sten Odenwald suffers from the same argument, and there's even a hint of it here. Nonetheless, these explanations are approximately true, and require bizarre shapes to break them.

For example, imagine a homogenous, perfectly shaped doughnut (a torus with a circular cross section). At the center of the doughnut hole we'd feel no gravitational field at all (a perfectly balanced tug-of-war). But deviate from the exact center just a tiny amount, and the closer side of the doughnut becomes more attractive than the other. One suddenly experiences a gravitational field that points away from the center of mass.

Doesn't this mean earth should have some huge dent in it, and not be so round? Look at the sizes of Mars and Earth. Are you surprised earth is still here after a crash of that magnitude? I am. Maybe earth was a lot bigger before a Mars-like planet destroyed itself crashing into earth, but then I go back to my question about the roundness of the earth.

Maybe someone more knowledgeable wants to talk about that. The article doesn't go into any great detail on that, which causes a lot of questions to be raised.

Slashdot has mentioned SATS.

It will allow you to physically commute 400 miles each way daily for working.

This would be great as an add-on dataset for NASA's 3d Earth explorer.

I'll be happier when I can actually visit. :)

I'll bet that Sojourner was just laying low and camping for all this time.

It seems like it might be there, water on the moon that is in the form of ice

http://nssdc.gsfc.nasa.gov/planetary/ice/ice_moon. html

The data show a distinctive 4.6 percent signature over the north polar region and a 3.0 percent signature over the south, a strong indication that water is present in both these areas.