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Riding an Ion Drive to the Asteroid Belt
Posted by
samzenpus
on Thu Jun 07, 2007 06:57 AM
from the to-infinity-and-beyond dept.
from the to-infinity-and-beyond dept.
Iron Condor writes "JPL is now close to embarking on another of its trademark, one-of-a-kind missions, this time to the heart of the asteroid belt: The Dawn mission is being prepared for launch this summer from Kennedy Space Center. Dawn will explore Ceres and Vesta, the two largest known asteroids in our solar system, which lie in the vast expanse between Mars and Jupiter. In the process, the mission will make history on several fronts. Besides being the first spacecraft to orbit a main-belt asteroid and the first to ever orbit two targets after leaving Earth, Dawn will be the first science mission powered by electric ion propulsion, the world's most advanced and efficient space propulsion technology."
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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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"Electric ions"? (Score:5, Insightful)
Re:"Electric ions"? (Score:5, Informative)
Parent
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Re:"Electric ions"? (Score:5, Interesting)
That being said, ion drives are many, many times more efficient than traditional chemical propellants. If my memory serves, about 3 orders of magnitude more efficient. This yields a much smaller propellant tank. Especially when you consider that the tanks must also be dragged around.
Parent
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p = m * v
p = momentum, v = velocity, m = mass
Yeah, an ion drive is just spitting out...well...ions [wikipedia.org]. As there's negligible gravity the further your distance from any large body, you don't have (noticeable) friction / angular acceleration to slow you down. Spitting out a single ion might not get you moving much faster, and it might not give you a lot more momentum, but it is still a measurable effect.
Now spit out trillions upon trillions of ions... It's moved from being a measurab
Re:"Electric ions"? (Score:5, Informative)
There are some really neat drives on the horizon that combine the best of thermal and ion drives, such as VASIMR. The particles are heated with radio waves to extreme temperatures (like in some fusion apparatuses), but since they're ionized, they're affected by magnetic fields. The fields collaminate them into a spiralling plasma, converting their chaotic energy distribution into a directed flow. A magnetic nozzle then redirects this out the back. Moderate thrust plus high ISP -- a nice combination.
My favorite "long range" design is the dusty fission fragment rocket. Most of the energy of fission reactions is contained in "fission fragments" -- basically, the fission of your fissionable fuel blasts microscopic fragments of the fuel at high speeds. In a normal reactor, these bump into the rest of the fuel or the moderator and are "thermalized"; the heat is then converted into electricity lossily. In a fission fragment reactor, the design is such that the fragments (where are inherently ionized) are allowed to escape the core; they can then be A) decelerated to produce electricity, or B) redirected with a magnetic field and vented out the back to produce a ridiculously high ISP thrust. You can do that with ionized particles.
Parent
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Exactly, human language needs more of parentheses, like in mathematics, so it's "electric (ion propulsion)" rathern than "(electric ion) propulsion". :-)
Re:"Electric ions"? (Score:5, Funny)
Parent
Re:"Electric ions"? (Score:5, Funny)
Move along, there's no warping to see here.
Parent
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Of course, the velocity of the exhaust itself is more useful in calculations (who needs Earth's gravity factored in?), but that's just how things go.
Not the first ion thruster propelled spacecraft (Score:5, Informative)
No, a quick Wikipedia check says otherwise: http://en.wikipedia.org/wiki/Ion_thruster#Mission
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we all know deep space 1 was just a NASA trip to get more doritos that got a bit out of hand
Re:Not the first ion thruster propelled spacecraft (Score:5, Informative)
Parent
Re:Not the first ion thruster propelled spacecraft (Score:4, Funny)
Parent
Re:Not the first ion thruster propelled spacecraft (Score:5, Informative)
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Re:Not the first ion thruster propelled spacecraft (Score:4, Interesting)
>involving ion propulsion have been for
>the purpose of testing ion drives,
>while this one is expected to perform
>scientific exploration and happens to
>use an ion drive.
Not even that; The Russians have been using them for decades for various spacecraft, and at least some current US comsats use them as well. I am working on another one right now, a comsat that uses it for orbit raising and on-orbit stationkeeping/repositioning.
I read TFA and it's mostly a load. I don't see why JPL has to jump on the same "we did it first" (except for all the other people who did it before us) bandwagon. I expect that sort of nonsense from ESA but JPL shouldn't have to pump themselves up, since they actually did do a lot of legitimate "firsts".
Brett
Brett
Parent
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Deep Space 1 and the various other previous ion tests by NASA were engineering missions, not science missions. This distinction is mostly important to the program officers.
Where they really fell down is not incluidng the Japanese asteroid mission, Hayabusa, which was certainly a science mission, just not from NASA.
Actually, there's a subtle distinction (Score:3, Informative)
Addition
Not the first to use ION Propulsion (Score:3, Informative)
We're doomed! (Score:5, Funny)
Re:We're doomed! (Score:4, Funny)
Layne
Parent
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Layne
TIE Fighters get smashed (Score:5, Funny)
Parent
acceleration with patience (Score:5, Interesting)
Space exploration and the related technology are still in their infancy, it is really exciting to to see the stuff of decades old sci-fi making into reality. Who can predict what non-conventional propulsion systems will look like in 50 years?
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http://en.wikipedia.org/wiki/Variable_specific_imp ulse_magnetoplasma_rocket [wikipedia.org]
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Propulsion systems will likely be driven by some sort of nuclear energy. The theory of operation of these systems will probably revolve around some set of quantum effects, maybe even superposition. These will be early systems based on this technology and, as such, may be prone to various difficulties imposed by the limits of an unrefined technology. They will be capable of traveling at unprecedented speeds using amazingly small amounts of fuel.
While there will definitely be privately-fund
Stairway to heaven (Score:3, Interesting)
Every once in a while I drift back to Doc Smith on the bookshelf. Although his space suits were made of Bakelite, some of his thoughts were rather far-seeing (thinking for example of the replicated logic units of his Skylark electronic brain) considering he wrote in the 30's, where Einstein's mass-energy equation hadn't yet been popularised. Pre-atomic era. He thought that with enough energy you could turn energy directly into matter
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Misguided: they assume Orion launching from the surface, not in space beyond effective EMP range. Most modern proposals call for a space launch.
Obsolete: We now do have the technology to initiate fusion chain reactions on even a miniscule amount of fusion fuel (antimatter-initialized microfusion, AIM)
Of course, Orion itself is an obsolete design, having been replaced by Medusa [wikipedia.org]. Every part of the design (system mass, ability to scale down, specific impulse, r
Two targets? (Score:4, Interesting)
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Well, most of the Apollo missions orbited both Earth and the moon. The Lunar Module orbited the moon on two separate flights, before descent and after ascent.
Re:Two targets? (Score:5, Informative)
Of course, most probes orbit the Earth for a while after launch, before injection into their transit path. All the early moon probes orbited both the earth and the moon, and the manned ones then orbited the earth again after return. So you could say that three targets have been orbited before, back in the '60s. This was just the project team looking for a 'first' to impress Americans with.
I suppose the difficulty levels go:
Orbit your base
Orbit your base and your target
Orbit your base, then gravity assist from other object, then orbit your target
Orbit your base, then gravity assist, then swing by one target, then orbit final target (typical multi-planet probe)
Orbit your base, then gravity assist, then orbit one target, then orbit another.
In fact, I was most impressed with the few probes which altered their trajectories in mid-mission to do swing-bys of targets of opportunity. You need flexible fuel provision to do that!
Parent
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Because those are so good with facts...
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And very good math!
Correction (Score:5, Informative)
Correction: Ceres is now the smallest dwarf planet.
Screw that, we need nuclear propulsion. (Score:5, Interesting)
You are attempting... (Score:5, Funny)
Not Kennedy (Score:2)
American exaggeration...? (Score:2, Insightful)
First to visit an asteroid
First to orbit two targets
or First to use an Ion Drive
and, in fact, space probes are now becoming sufficiently common for the launches to be a yawn in the press. The Europeans are dropping probes on Titan, for christsake!
What is it with us? This kind of trumpeting makes the rest of the world assume we're so insecure that we need to keep pretending that we're the best...... Oh wait, maybe that's true??
Re:American exaggeration... (not really, no) (Score:3, Insightful)
People seem to forget the number of failures exploring Mars. The Americans lost the Observer, the Climate Orbiter, Deep Space 2, and the Polar Lander sin
About time (Score:3, Insightful)
As scary or foolish as it may seem, our only future is to get off this rock and learn to live in space. Mars is El Dorado, worthless except in the minds of poets and dreamers. There may be hope for purchase on some of the moons, but to get to them or Mars we'll have to have already adapted to space.
I don't think it will work with out fusion, but if they find gold or oil in one of those rocks, who knows what could happen.
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You don't count NEAR [wikipedia.org]?
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