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Next Goals For The ESA
zeux writes "With all the news we got recently from space I tried to gather some information about the next goals of the ESA (European Space Agency). Along with a space vehicle designed to carry supplies to the ISS between 2004 and 2013, they are working on the new 'Vega' launcher (2006) and still playing with the SMART-1 probe which is slowly heading to the moon testing an ion drive that is ten times more efficient than the usual chemical systems (1500 hours cumulated thrust time so far)."
Looking at the ESA site, if we're thinking of going back to the moon soon and possibly bringing back a bunch of old Apollo systems, why don't we buy some of the ESA's ATV's and slap on a larger booster? seems like it'd be a nicer ride (once modified) than the old Apollo craft. With the added bonus of being a spacecraft that is actually in production (no need to try and re-invient the wheel).
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But they are economical of fuel. Jettisoning the exhaust at such high speed means you need hardly any fuel; which is good, but the energy source is an issue.
The reason that they are inefficient is that the exhaust velocity is too high. It turns out that the optimum exhaust velocity for minimum energy is about 2/3 the mission delta-v- and the delta-v to get to the moon is about 4.1 km/s whereas an ion drive exhaust velocity is usually around 30km/s... hugely too high from an energetic point of view.
Ok, big deal- it's only energy right? Wrong. The solar panels end up pretty enormous, and pretty heavy, pretty quickly. Nuclear energy? Power/weight ratio is little better.
Still, it works, but it's not even as efficient as chemical rocketry; chemical rockets can hit 80+% energetic efficiency in fact (it's very high because of the high temperatures used in the combustion chamber, rocket engines are actually classed as heat engines).
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"Gravity is only a theory, not a fact!"Just because Bush unveiled grandiose plans for NASA, and they took note of it and adjusted a few of their plans (which in retrospect were due for a change anyway) does not mean other space agencies will follow suit.
The reaction given to Bush's plans by other nations have been circumspect, lets see where this all goes after the elections are over.
Bush's moon and mars plan seem like such a comprehensive change for NASA that they might also have a serious impact on the ESA. With NASA's budget redirected into the new plan, will the ESA pick up the slack with greater involvement in the ISS beyond the ATV? Or will they have a significant involvement in the moon and mars plan - maybe using the ATV to supply a moon base? It would be a shame for them to spend a fortune developing the ATV, only to be told that it was no longer needed because the ISS was no longer maintainable due to a lack of US funds.
You need an element which is easily ionized. you also want the individual ions to be pretty massive. A bonus is if the ionized version of the element is not too reactive. Early drives used mercury or cesium, but they had a habit of sticking to things and clogging them up, and had to be heated before they were ionized.
i'm pretty sure the cost of the xenon is negligible compared to almost any other cost around.
So it seems that ESA is working on a next-gen cargo craft, and NASA is working on a next-gen human transporter. Could it be that Europe and the United States are actually splitting the design costs necessary to replace the Space Shuttle?
These two separate systems can do what the Shuttle could do by itself -- haul cargo and move people -- and I'm betting it's cheaper, too, to do things with two separate devices.
An ion drive is still nowhere near effective enough for a manned
interstellar probe.You need a fairly pure fusion drive, or antimatter, or some flavour of beam-rider to get interstellar journey times down to a few years or decades without completely silly mass ratios.
They're not trying to minimize the amount of energy used. They're trying to minimize the weight of the vehicle. Yes, the solar panels have to be bigger if they eject the ions at a higher speed, but this is more than made up for by not having to carry as much fuel.
I don't doubt that chemical rockets have a very high energetic efficiency, but they come with the major disadvantage that you have to transport all the energy out of the gravity well and into low earth orbit. With solar energy, you can wait until you're in space to collect it, so it's OK if you can't use it as efficiently.
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Also let us not forget the last time Europe send somebody into the unknown. He stumbled upon a new continent. Look what mess that brought us in. Europe does not want to make that same mistake again. ;-)
Yeah, Europe doesn't want to have some upstart criminals on some new continent to bail them out of two world wars that they couldn't solve themselves, do they? ;)
Other things DO work. CERN is ione, wich brought us HTTP. Airbus is another example. The question remains if Europe wants it at this moment. It will naturaly be good footage on newsprograms. OTOH it will draw away money that could have been used better. I am not saying it would not be a good idea. I just wonder if the money spend can't be used better.
My guess is that Europe is putting to the test an unmanned space program. Here in the US a LOT of people criticize NASA for spending too much time and money putting men into space when they could be pursuing other things, and it looks like Europe is putting that to the test.
One thing's certain, from what I can see. :) It sure is nice to see different space exploration models cropping up besides NASA's. NASA may have gotten us to the moon, but they seem to have burned out sometime around SDI.
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