Posted by
Hemos
on from the checking-things-out dept.
hubie writes "The NEAR spacecraft flew by the asteroid Eros at a closest approach of only 3 miles! Despite what the story says, that is much less than the altitude of a commuter aircraft. Stay tuned for some expected cool closeup shots."
This is extremely dangerous. With the low (almost nil) gravity on Eros, an alien lifeform can easily knock down our probe with nothing more than a well-aimed rock. I consider it a serious lapse of judgement in our elected officials to allow NASA to spend billions on such a risky endeavour.
I propose a Congressional panel to carefully scrutinize NASA's policies in regards to alien surface-to-air defenses, and whether the NEAR probe and others (Cassini! The Saturnians are watching!) are unjust provocations to our extra-terrestrial brethren.
I, for one, would like to welcome our new overlords, and would like to remind them that as a loyal Slashdot reader, I can be instrumental in rounding up the open-source zealots to toil in their salt mines.
The NEAR spacecraft, and the information that it is gathering, are probably one of the most worthwhile missions that NASA has ever had. The detailed look at Eros that it is providing will fill in a lot of details about our scientific knowledge of asteroids.
You can expect to see similiar missions to asteroids in the coming years. SpaceDev, a publicly owned company, is proposing NEAP, the Near Earth Asteroid Prospector. This probe, tentatively scheduled to launch in 2003, was originaly planned to visit the Near Earth Asteroid (NEA) Nereus. Recent discovery of hundreds of previously unknown NEA's may cause SpaceDev to delay the mission, and redirect the probe to some better target asteroid.
Additional missions? None scheduled yet. But you can bet they'll happen. The accessable resources of the asteroids have an estimated dollar value of about $100 Billion per person currently living on Earth. Someday soon, someone is going to dig into that Bonanza.
Eros Photographed, Buggers Discovered!!!
by
Sir.Cracked
·
· Score: 5
In a leak from the Defense Department, the first Photos of Eros revealed a race of insectoid beings that insider's are calling Buggers. Speculation is flying as to how to deal with the threat, with one idea of gathering all the most brilliant children up and putting them on a space station to train as generals. More at 11.
If you don't know what I'm talking about, read Ender's Game
-- Where are we going, and why am I in this handbasket?
What processors NEAR runs off of..
by
eples
·
· Score: 3
Well you couldn't be more wrong about what processors are in this sucker!
There's actually 7 on-board, 6 of them are Harris
RTX2010's (Harris is now Intersil). This processor can do 6 MIPS at 8MHz..
There is also one Honeywell
1750A that runs the flight program. (2.5 MIPS - The military hybrid of this
chip also runs Linux ;.)
I quote from the above.PDF: "All processors are Harris RTX2010's except the G&C subsystem Flight
Computer which is a Honeywell 1750A."
If you look at frames 43, 44 & 45 of this orbital animation of eros you can clearly see a huge boo-scary tortured-looking face on the surface!
I know it's a meritless thing to point out and has no real scientific significance (like the infamous "face on Mars"), but considering that:
It's named after the Greek god of love (dual entendre, anyone?)
It's shaped like a loaf
It's almost Hallowe'en
...I found it pretty funny on three separate levels, which could lead to some great Onion-esque headlines...
Following Probe, Lusty Anthropomorphic Asteroid Hurtles Toward Uranus
Mister Hanky's Mothership Arrives
Approaching Space Demon "Eros" Denies Connection to Ancient Ones, Intention to Destroy Earth
-- Snickersnee3: Build your own 3-watt Luxeon Star headlamp from scratch
Re:Good going Noam and the NEAR Team!
by
Tackhead
·
· Score: 3
> This project is one example of an effective, efficient, non-disasterous project that demonstrates that
space can be done for cheap cost [... ]
Agreed. NEAR is an awesome bit of work. Though the mission came extremely close to disaster. The reason we're reading about this in 2000 is because they damn near lost the spacecraft on first approach, and executed a miraculous recovery. It delayed the mission a year (waiting for the next orbit), but it didn't cost us much in terms of scientific return at all.
It's also a great demonstration of the fact that if you're in orbit around something - thinking of NEAR, Eros, and the Sun - whether you throw an object "up" or "down" makes no difference, it'll intersect your position next orbit.
That is, if you want to go "up" or "down" and you're in orbit, you thrust "forward" or "back". The EROS recovery was basically "screw it, don't waste fuel chasing the rock this year, because if we just relax, Newton will put us back on target for another encounter next year")
You are right about being able to orbit at any altitude, of course, friction of the atmosphere would become significant at lower altitudes.
You were only partially right when you said that the earth's gravity pulls at 9.8 m/(s^2), actually, according to Universal Gravity, two bodies will attract eachother with a force governed by the following equation:
F=(G M m)/(r^2)
Where F is the force of attraction, G is the gravitational constant (about 6.67*10^-11 m^3/(kg/s^2)), M and m are the masses, and r is the distance between the the two bodies' centers of gravity.
That is all well and good, but it dosen't tell us what the force of attraction for the earth is. To discover that, we have to use another equation, Newton's second law:
F= m a
Where F is force, m is mass, and a is (you gussed it) acceleration.
We can set F equal to F and yeald:
m a = (G M m) / r^2
We can cancel out the two small 'm's to get:
a = (G M) / r^2
We need a 'r' and a 'M', so I will now stipulate that the radius of the earth is about 6.38*10^6 m and that the mass of the earth is 5.98*10^24 kg. An abitious slashdoter could most likely find much more accurate figures, but these will fit our purposes. Consequently, we can find the acceleration due to gravity with:
a = (6.67*10^-11 * 5.98*10^24) / ((6.38*10^6)^2)
a = 9.799 m/(s^2)
I hope you can see that 'a' would be significantly less were an object higher (say, 500km) from the surface of the earth, as 'r' would increase:
a = (6.67*10^-11 * 5.98*10^24) / ((6.38*10^6 + 500*1000)^2)
a = 8.427 m/(s^2)
Back to the original question: How fast must an object to travel to orbit the earth at the surface? To answer that, we have to call apon yet another equation, that of centripical acceleration in circular motion:
a = (v^2) / r
We know that the centripical acceleration is the acceleration due to gravity, which we found to be 9.799 m/(s^2) at the surface of the earth, and we know 'r' to be the radius of the earth, so to find 'v' (velocity) we could have:
v = sqrt( a r )
v = sqrt( 9.799 * 6.38*10^6)
v = 7906.81 m/s
v = 7.907 km/s (*)
As you can see, this is significantly less than your figure of 30,000 km/s!
(*) Us Americans, who's brains have been destroyed by the English System, would get more sense out of 17,687 mi/hr.
--
Jordan Bettis
``Wherever you go, there's another stupid sigfile quote.''
Slashdot Mirror
I propose a Congressional panel to carefully scrutinize NASA's policies in regards to alien surface-to-air defenses, and whether the NEAR probe and others (Cassini! The Saturnians are watching!) are unjust provocations to our extra-terrestrial brethren.
I, for one, would like to welcome our new overlords, and would like to remind them that as a loyal Slashdot reader, I can be instrumental in rounding up the open-source zealots to toil in their salt mines.
Any ideas to what shape an asteroid named "Eros" would be?
- I don't care if they globalize against free speech. All my best free thoughts are done in my head.
Here's a number of pictures of it:
http://nssdc.gs fc. nasa.gov/planetary/mission/near/near_eros.html
Enjoy =)
---
The NEAR spacecraft, and the information that it is gathering, are probably one of the most worthwhile missions that NASA has ever had. The detailed look at Eros that it is providing will fill in a lot of details about our scientific knowledge of asteroids.
You can expect to see similiar missions to asteroids in the coming years. SpaceDev, a publicly owned company, is proposing NEAP, the Near Earth Asteroid Prospector. This probe, tentatively scheduled to launch in 2003, was originaly planned to visit the Near Earth Asteroid (NEA) Nereus. Recent discovery of hundreds of previously unknown NEA's may cause SpaceDev to delay the mission, and redirect the probe to some better target asteroid.
Additional missions? None scheduled yet. But you can bet they'll happen. The accessable resources of the asteroids have an estimated dollar value of about $100 Billion per person currently living on Earth. Someday soon, someone is going to dig into that Bonanza.
In a leak from the Defense Department, the first Photos of Eros revealed a race of insectoid beings that insider's are calling Buggers. Speculation is flying as to how to deal with the threat, with one idea of gathering all the most brilliant children up and putting them on a space station to train as generals. More at 11.
If you don't know what I'm talking about, read Ender's Game
Where are we going, and why am I in this handbasket?
Well you couldn't be more wrong about what processors are in this sucker!
There's actually 7 on-board, 6 of them are Harris RTX2010's (Harris is now Intersil). This processor can do 6 MIPS at 8MHz.. There is also one Honeywell 1750A that runs the flight program. (2.5 MIPS - The military hybrid of this chip also runs Linux ; .)
I quote from the above
"All processors are Harris RTX2010's except the G&C subsystem Flight Computer which is a Honeywell 1750A."
Nice little satellite for early 90's.
I'm a 2000 man.
If you look at frames 43, 44 & 45 of this orbital animation of eros you can clearly see a huge boo-scary tortured-looking face on the surface! I know it's a meritless thing to point out and has no real scientific significance (like the infamous "face on Mars"), but considering that:
- Following Probe, Lusty Anthropomorphic Asteroid Hurtles Toward Uranus
- Mister Hanky's Mothership Arrives
- Approaching Space Demon "Eros" Denies Connection to Ancient Ones, Intention to Destroy Earth
Just look at it already, you'll see what I mean: http://n ssd c.gsfc.nasa.gov/planetary/image/near_20000919_larSnickersnee3: Build your own 3-watt Luxeon Star headlamp from scratch
Agreed. NEAR is an awesome bit of work. Though the mission came extremely close to disaster. The reason we're reading about this in 2000 is because they damn near lost the spacecraft on first approach, and executed a miraculous recovery. It delayed the mission a year (waiting for the next orbit), but it didn't cost us much in terms of scientific return at all.
It's also a great demonstration of the fact that if you're in orbit around something - thinking of NEAR, Eros, and the Sun - whether you throw an object "up" or "down" makes no difference, it'll intersect your position next orbit.
That is, if you want to go "up" or "down" and you're in orbit, you thrust "forward" or "back". The EROS recovery was basically "screw it, don't waste fuel chasing the rock this year, because if we just relax, Newton will put us back on target for another encounter next year")
You are right about being able to orbit at any altitude, of course, friction of the atmosphere would become significant at lower altitudes.
You were only partially right when you said that the earth's gravity pulls at 9.8 m/(s^2), actually, according to Universal Gravity, two bodies will attract eachother with a force governed by the following equation:
F=(G M m)/(r^2)
Where F is the force of attraction, G is the gravitational constant (about 6.67*10^-11 m^3/(kg/s^2)), M and m are the masses, and r is the distance between the the two bodies' centers of gravity.
That is all well and good, but it dosen't tell us what the force of attraction for the earth is. To discover that, we have to use another equation, Newton's second law:
F= m a
Where F is force, m is mass, and a is (you gussed it) acceleration.
We can set F equal to F and yeald:
m a = (G M m) / r^2
We can cancel out the two small 'm's to get:
a = (G M) / r^2
We need a 'r' and a 'M', so I will now stipulate that the radius of the earth is about 6.38*10^6 m and that the mass of the earth is 5.98*10^24 kg. An abitious slashdoter could most likely find much more accurate figures, but these will fit our purposes. Consequently, we can find the acceleration due to gravity with:
a = (6.67*10^-11 * 5.98*10^24) / ((6.38*10^6)^2)
a = 9.799 m/(s^2)I hope you can see that 'a' would be significantly less were an object higher (say, 500km) from the surface of the earth, as 'r' would increase:
a = (6.67*10^-11 * 5.98*10^24) / ((6.38*10^6 + 500*1000)^2)
a = 8.427 m/(s^2)Back to the original question: How fast must an object to travel to orbit the earth at the surface? To answer that, we have to call apon yet another equation, that of centripical acceleration in circular motion:
a = (v^2) / r
We know that the centripical acceleration is the acceleration due to gravity, which we found to be 9.799 m/(s^2) at the surface of the earth, and we know 'r' to be the radius of the earth, so to find 'v' (velocity) we could have:
v = sqrt( a r )
v = sqrt( 9.799 * 6.38*10^6) v = 7906.81 m/s v = 7.907 km/s (*)As you can see, this is significantly less than your figure of 30,000 km/s!
(*) Us Americans, who's brains have been destroyed by the English System, would get more sense out of 17,687 mi/hr.
Jordan Bettis
``Wherever you go, there's another stupid sigfile quote.''