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Ion Rocket to Map Moon with X-Rays
Posted by
CmdrTaco
on Sun Nov 07, 2004 12:06 PM
jralls writes "The Guardian is reporting that a European ion-rocket has taken the last year to reach the moon and is about to enter lunar orbit. Once it slows and gets into a very low orbit, it will probe the surface with x-rays in an effort to solve the long standing puzzle of the moon's origin."
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New Ion Engine Enters Space Race 168 comments
Bibek Paudel brings us a BBC report on the development and testing of an new ion engine by a security firm named Qinetiq. The engine will be used in an ESA spacecraft tasked with mapping the Earth's gravitational field from orbit. Only a handful of ion drives have been used for space missions before, some of which we have discussed. Quoting:
"Cryogenic pumps can be heard in the background, whistling away like tiny steam engines. Using helium gas as a coolant, they can bring down the temperature in the vacuum chamber to an incredibly chilly 20 Kelvin (-253C). The pressure, meanwhile, can drop to a millionth of an atmosphere. Ion engines ... make use of the fact that a current flowing across a magnetic field creates an electric field directed sideways to the current. This is used to accelerate a beam of ions (charged atoms) of xenon away from the spacecraft, thereby providing thrust."
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Visibile from Earth? (Score:3, Interesting)
Play iCLOD Virtual City Explorer [iclod.com] and win Half-Life 2
Re:Visibile from Earth? (Score:2)
Re:Visibile from Earth? (Score:5, Informative)
Parent
Re:Visibile from Earth? (Score:2, Troll)
Re:Visibile from Earth? (Score:4, Insightful)
If we used some sort of higher powered rocket to generate the velocity, I wonder if ion rockets could hold that velocity for a long time.
Since we are using this space, I wonder what we would need the ion rocket for to hold that velocity. In space, there is not much that could slow you down.
Parent
Re:Visibile from Earth? (Score:4, Interesting)
Jeroen
Parent
ESA doesn't have a moon capable rocket (Score:3, Interesting)
Re:Visibile from Earth? (Score:2)
Re:Visibile from Earth? (Score:3, Informative)
I wonder if we are able to observe this interplanetary tortoise from earth? If it passes the bright side in full moon, we should have quite a clear view of it since it's going so slowly.
I'm curious what make you think it will be going slowly? It will be orbiting the moon at exactly the same speed as any other craft at the same altitude would be orbiting the moon. The type of engine or thrust has nothing at all to do with orbital mechanics.
Where do you think the Moon came from? (Score:3, Funny)
I say the moon came from Uranus, what do you say? Here take a survey [opinionpower.com]!
Survey...
Uranus
Another Galaxy
Mars-sized planet crashed into the earth
Comet
Meteor
Microsoft
Another Dimension
It was a spaceship!
Cowboy Neal
Re:Where do you think the Moon came from? (Score:5, Funny)
Parent
Re:Where do you think the Moon came from? (Score:2)
ROFTLMAO!!!!!
Re:Where do you think the Moon came from? (Score:2)
Great title (Score:5, Funny)
Moon mining? (Score:5, Interesting)
"The sun emits X-rays and these are reflected back into space by atoms on the Moon's surface. A magnesium atom will reflect an X-ray in a different way from an iron atom, and Grande's detector can detect these differences.
Flying over the lunar poles, so that it covers the entire Moon as it revolves below, Smart will create strip maps of the surface - and eventually a global map of its composition."
Look like useful data to me if we were in the 'mine the moon' business... maybe in a not so distant future?
Re:Moon mining? (Score:2)
Now that GWB is back in office, someone send up a note quick that there is oil and wealth on the moon!
Maybe something useful could come out of his re-election, afterall!
Keep in mind.... (Score:3, Insightful)
Re:Keep in mind.... (Score:4, Informative)
Parent
MOD DOWN PARENT (Score:4, Informative)
Parent
A year to reach the moon? (Score:2, Insightful)
Re:A year to reach the moon? (Score:5, Informative)
But the mass being expelled at high speeds (the ions) is so low, that accelleration is VERY slow. So it takes a long time to get up to speed, but the maximum speed you can theoretically reach is much greater than that of chemical rockets.
Parent
Re:A year to reach the moon? (Score:5, Informative)
The difference is that it will take a chemical rocket much more propellant to get there, because it is far less efficient in its use of propellant mass (i.e. it has a lower specific impulse).
Parent
Basic rocket physics makes it a bit clearer (Score:5, Informative)
Look up any reasonable book on mechanics and you will find a formula for the final velocity of rockets that have a empty mass M, mass of fuel m, and have an exhaust velocity v. The final velocity of the vehicle is ...
In other words ion rockets will beat chemical rockets because they eject their exhaust at a reasonable fraction of c, whereas chemical rockets have exhaust velocities more like velocities we see on earth (e.g. bullets). So chemical rockets need lots of mass, but that's ok because they throw out lots of mass. Trouble getting to space is expensive ... each kilo of fuel you put in orbit better be wisely used ... so in space ion rockets make sense (apart from the fact you can't use them on Earth anyway ... wouldn't be able to lift off even).
Hope this makes things a bit clearer.
Parent
Re:A year to reach the moon? (Score:3, Funny)
Re:A year to reach the moon? (Score:5, Informative)
> chemical propulsion.
Depending of course on the fixed mass of the spacecraft, vs it's propellant mass, of course. You get more momentum change from given amount of propellant, but if you only had a teaspoon full of propellant, or the spacecraft was exceptionally massive, you wouldn't get more velocity.
> But the mass being expelled at high speeds (the ions) is so
> low, that accelleration is VERY slow. So it takes a long
> time to get up to speed, but the maximum speed you can
> theoretically reach is much greater than that of chemical
> rockets.
To expand, the measure of efficiency of a rocket engine is the specific impulse or ISP. It's how much momentum change you get per unit of propellant mass, and the usual unit is seconds (lb-sec/lb). The highest actually-achievable ISP from a chemical rocket is somewhere in the 475 seconds. The Saturn 5 first stage was more like about 350, and monopropellant thrusters used for many satellite propulsion systems is more like 150-180! That means that if you want to change the velocity a lot, you need a whole lot of propellant.
I'm not sure which engine this particular program uses, but the ISP of the typical Xenon ion thruster is something like 1800. So you have to carry fantastically less propellant for a given velocity change, meaning it can weight less at liftoff, meaning you can use a weaker/cheaper booster.
The downside is that you don't get something for nothing. It takes, not surprisingly, a whole lot of electrical power to make it go. So you put in 4000-5000 watts of power, and it only generates
Brett
Parent
Re:A year to reach the moon? (Score:5, Informative)
There was no extra weight margins on the launch vehicle to do so. However, if you have a more powerful booster (i.e. lots more money), you can then get higher intial speed.
This mission was to prove to EU that their ion engine worked. So they wanted it to keep running for quit some time. NASA did this be creating deep space one, which ran around picking up steam via its ion engine.
Down the road, you can bet that EU will launch a number of deep space probes based on ion engines with high initial speeds.
In addition, their will be a real push for micro sats with ion engines to control them. Makes a lot of sense to send these to other planets. think of 100 small satillites going though out jupitor or saturn planets. Or better yet, small micro sats around Mars providing surface to space communication, pictures, glp, etc. Send about 100 of these to orbit mars and we would have a very through pic of mars, moon, etc.
Parent
Re:A year to reach the moon? (Score:3, Funny)
Re:A year to reach the moon? (Score:2)
This is insane! (Score:2, Funny)
It's from Wisconsin. (Score:4, Funny)
New tourist slogan (Score:4, Funny)
Doesn't quite have the same ring...
Parent
Possible Resolution to US moon landing hoax theory (Score:5, Funny)
A Space Odyssey (Score:2, Funny)
wow (Score:5, Funny)
Re: wow (Score:2, Funny)
> sobering thought that that headline sounds exactly like something you might hear in a pulp sci-fi movie from the 50's...
Science has finally caught up with fiction!
From the article -- galactic bowling physics? (Score:5, Insightful)
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 [nasa.gov]. 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.
Re:From the article -- galactic bowling physics? (Score:3, Informative)
There is a reason why small objects, like asteroids, are often irregular in shape, while large objects, like planets, tend to be nearly spherical. All parts of an object are attracted to each other by gravity, this tends to pull the object into a spherical shape. Above a certain size (which depends on the materials involved) the object is not strong enough to maintain its shape and collapses
Biq == Round (Score:5, Insightful)
The mountains on Earth may appear huge to us insects on the surface, but from a distance the earth appears as smooth as a billiard ball.
Ironically this event was so big, that unlike latter smaller hits, all evidence in the way of dents will be gone as the entire globe virtually liquefied and coalesced again. Though I wouldn't rule out some exotic mass distributions that might lend evidence of it.
Parent
Gooey, Hot, Weightless and EXTREME PRESSURE (Score:4, Informative)
Recent speculation is that the very center has a high ratio of Uranium, enough so that the pressure actually creates a self-sustaining natural nuclear reactor. When it gets too hot it diffuses and shuts down, only to coalesce and restart again (never a big boom). This starting and stopping of the nuclear processes at the Earth's core may be responsible for our planets large magnetic field, and occasional shut downs and reversals of the magnetic field as this nuclear process fluctuates.
You're right that the center would be weightless, but under more pressure than we can possible create in the lab with the best diamond anvils. It only takes a few miles of crust to crush carbon to diamonds, and here we are talking 8,000 miles of rock pressing down. Though the rock (iron) at the center isn't adding any additional pressure, it has thousands of miles of rock above it that is. Quite the hellish place.
BTW, I don't know how I typed Biq in my rirst post when I meant to type Big (no one seems to have noticed)
Parent
Not confusing Anything (Score:3, Interesting)
Here is a link to a Discovery article [discover.com]
Nuclear Planet
Is there a five-mile-wide ball of hellaciously hot uranium seething at the cent
Re:From the article -- galactic bowling physics? (Score:5, Interesting)
The following contains some links to mostly non-technical explanations of planetary roundness. I'd like to point out that part of this explanation [sciam.com], 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 [astronomycafe.net] by Dr. Sten Odenwald suffers from the same argument, and there's even a hint of it here [nasa.gov]. 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.
Parent
Re:From the article -- galactic bowling physics? (Score:4, Informative)
For anybody who is interested, here's a theory [uc.edu] (bottom of the page): "one theory says the moon formed when a big, molten chunk of crust was knocked/blown off from the rest of the planet". And much more info [google.ca] about it.
Parent
Re:From the article -- galactic bowling physics? (Score:4, Informative)
Parent
Just remember... (Score:3, Funny)
The ion drive is the real story (Score:5, Interesting)
Quoting from the article,
"We have shown that even a small ion engine like Smart's can get us across space. Now we are planning to build space telescopes and robot probes to planets such as Mercury, using bigger and more powerful ion engines. These will take years off space-travel times. Instead of decades-long missions, we will take only a couple of years to cross space for future projects."
But,
"Ion engines need electricity and only solar panels can provide enough at present. So ion engine missions will be restricted to planets and moons near the Sun."
So the solution to deep space exploration is nuclear-powered ion-drives and NASA is working on it.
Re:A year?! (Score:5, Informative)
they give less trust/second, but they can keep burning for allot longer, since the sun gives a constant supply of fuel (in the form of electricity from solar panels).
so you've got a smaller probe, which means easier to get into orbit from where it can fly on it's own power, so even tho it takes longer to get where you want, it will be cheaper to get it into orbit.
btw, they are planning on bigger engines in the future, so hopefully they will go faster someday.
Parent
Re:A year?! (Score:5, Informative)
The tradeoff is betwen the extra time it takes to get to the destination (due to the low thrust of an ion engine), and the reduced cost created by being able to launch a much smaller amount of mass into space in order to do the mission.
btw, they are planning on bigger engines in the future, so hopefully they will go faster someday.
The issue with ion enginer thrust is not so much size, as it is power. The thrust you get is directly proportional to the amount of power you can generate. If you're using solar arrays, then you're limited to something between 15-20 kW (the Boeing 702 has solar arrays that produce ~15 kW at end-of-life).
Parent
Re:A year?! (Score:5, Informative)
The last months the orbit was also synchronized with the moon. The highest part of SMART-1's orbit coincided with the lowest point of the moon's orbit. This helps the craft to get an extra boost every month. Take a look at a graph of the orbit here [esa.int].
Oh, and they do have normal propellant onboard, there's some 70kg left iirc. I think it was installed in case the ion engine failed, but I'm not sure of that. It could also be to correct the initial orbit if the launcher would have placed it in a wrong one. Anyway I *hope* it will be used to attempt a soft landing after the mission is over.
Parent
Re:This begs the question: (Score:4, Insightful)
In all seriousness it's nice to see some other serious large-scale attempts being made by countries other than the US and Russia. As with all things scientific, the more head working together the more we all learn.
Parent
Re:Accreted Rings (Score:3, Insightful)
In any case, the planets you see now are just the ones that stayed in the system. Material didn't just cleanly accrete directly into the existing bodies. Most of t