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European Moon Mission Ready for Launch
merryprankster writes "Europe's first mission to the Moon is set for blast off from Kourou in French Guiana just after midnight, local time, on Sunday. SMART
1 will study the composition of lunar rock through X-ray observations. The probe uses a new solar electric propulsion system which converts solar energy its panels into motion via the expulsion of ions. Details at the ESA mission site."
The probe uses a new solar electric propulsion system which converts solar energy its panels into motion via the expulsion of ions.
IMHO that is much more interesting than the mission itself. The less chemical fuel needed to get moving once in space could mean more room for payload.
Beat the weenies to the punch:
I, for one, welcome our new ion propelled masters!
Imagine a beowulf cluster of these!
Natalie Portman could fly one of these to my house anytime!
The lengths people will go to to hurt the ego of chemical-rocket engineers!
Chemical rockets, 70, found dead in their suburban home, truly an American icon.
Obligatory goatse.cx link.
Trolling is a art,
I hate to burst everyone's bubble, but NASA used ion propulsion on the Deep Space 1 mission several years ago. Yes, cool technology but like most stuff it's been researched for years and used before.
Well, they should add another one to the ship. Twin Ion Engine craft are pretty speedy, and highly manueverable as well.
--
"Outlook not so good." That magic 8-ball knows everything! I'll ask about Exchange Server next.
And the payload isn't really greater at all.
The payload in the Apollo program was launched from a Saturn V, which can put nearly 120,000 kg in low orbit and so had enough oomph to put it's payload immediately into a lunar trajectory. The payload for this mission will be launched from an Ariane V, which can only put ~16,000 kg in low orbit, but at (IIRC) a tenth the price.
Hopefully they can perfect the ion drive, however through this to increase the speed and payload capacity.
The drive itself is pretty near perfect; the problem is that if you're going to kick out exhaust at such insane velocity that you don't need a whole lot reaction mass to get good deltaV, then you need a whole lot of energy to get good deltaV instead. And these guys are getting that energy from solar panels, which takes a while. If we had that anti-matter reactor you want (or cold fusion, or anything else providing lots of energy from little mass) we might eventually want something fancy like VASIMR, but in the short run we'd probably just plug the reactor in to bigger or more ion drives.
Sure the Ion drive is a really neat addition, but it's soooo slooooow. It's going to take them 15 MONTHS to get there!
Actually, Ion propulsion is faster. It just has much less tork, if I may use the analogy.
Unlike rocket propulsion, Ion propulsion has a constant push. Although is exerts a smaller force, it can accelerate for as long as there is fuel, and it uses very little of it.
That's how they'll be able to send people on mars in a matter of months (last figures I had was 9 months) instead of more than a year (it was reported to be somewhere around 16-18 months using rocket propulsion).
For a moon mission, though, speed isn't necessarily important, so they can afford the longer trip time to same money and augment the payload (instead of carrying all that fuel).
Solar electric propulsion is hardly new. It's been used for getting communications satellites out to their final geosynchronous orbits for a number of years now, and NASA demonstrated using solar-powered ion engines for interplanetary primary propulsion on Deep Space 1 back in '98.
What ESA is claiming is new about this mission is that they'll be combining ion propulsion with gravity assist maneuvers. AFAIK that hasn't really been done yet (although I know some guys at JPL who're working on it), and given how difficult it can be to work out low-thrust trajectories in the first place I would imagine that successfully throwing gravity assists into the mix would be a significant acheivement.
The reason ion engines are a good thing is because they are so efficient. But they also have their share of problems.
;) I did my senior thesis on a solar electric propulsion Mars mission, and I find it to be far more interesting than most people seem to.
The figure of merit for rocket propulsion is specific impulse (Isp). It is a measure of unit thrust per unit mass of fuel consumed per unit time. Conventional (chemical) propulsion, such as solid rocket boosters, have an Isp in the 200 - 300 range. But they generate many many thousands of kilonewtons of thrust. That's why we use them for launching things out of gravity wells.
Ion engines, on the other hand, have Isps from 2000 - 3500 (though the higher end of that range is only test-stand stuff right now). They, however, produce only millinewtons of thrust, and cannot be used for fast orbit transfers or launches. But they can be made small. Very, very small, with correspondingly small amounts of fuel, which is pure joy for aerospace engineers trying to design robotic missions.
Unfortunately, they are also power-hungry little buggers. A single ion engine can use a kilowatt of power while running...and they must be running all the time to generate enough delta-v to have an effect on the course of a spacecraft. (Delta-v is the measurement of how much of a change in a velocity vector is necessary to effect the desired change in course, and mission designers begrudge every cm/s...every maneuver burns propellant, and there are no gas stations in space.) There are only two ways to get power in space right now: solar cells, and some form of nuclear decay. Only solar cells have a good enough power/mass ratio to run ion engines, and as missions proceed farther out from the Sun, array area must be bigger, which adds mass. It's a tricky balancing act.
For this mission, however, the craft will always be close enough to the sun to generate the power it needs fairly easily. (Except when it's in shadow, but that's why we have storage batteries.)
Ion propulsion is an old technology, incidentally. It's been around in some form or another since the 60's. It's only recently that it became economical, though.
I could go on for pages, but I'm unconvinced anyone wants to see that.
-Carolyn
Like Daddy always said: if you can't dazzle 'em with brilliance, baffle 'em with bullshit.
What exactly is innovative about this mission? It is the same mission as flown by Clementine years ago. Solar electric propulsion is commonplace. Here are some spacecraft that have flow them to date:
I don't think this story is slashdot worthy.
an ill wind that blows no good