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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."
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.
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.
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