Slashdot Mirror
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)."
What are the technical obstacles to Lagrange point colonies?
Well, to give it equal footing to the Spirit, here's some new high res photos that the ESA's orbiting photo taker took. Apparently there's also one of it looking down on the crater that the Sprit is in. http://www.esa.int/export/SPECIALS/Mars_Express/in dex.html
If you RTFA'd, you would realize that the satelite isn't on a direct moonshot, it's spiralling out from an earth orbit, to a lunar orbit. This would be hella slow compaired to a direct shot, which should get it there in a few days at worst. The thing is traveling at 3850km/h, it's just not doing it with a direct vector to the moon, rather, a spiral.
"Victory means exit strategy, and it's important for the President to explain to us what the exit strategy is." G.W.Bush
The ESA also has a probe named Huygens headed for Titan, the largest moon of Saturn that will land on the surface in 2005 and send back photos. Titan is the only moon in our solar system with a thick atmosphere. It is believed it may be similar to that of Earth's millions of years ago.
I've only read that Xenon is used in current Ion drives... kinda wondering why more common gasses *read, nitrogen, probably the cheapest* can't be used. Anyone know?
"Victory means exit strategy, and it's important for the President to explain to us what the exit strategy is." G.W.Bush
SMART-1 is part of the Small Missions for Advanced Research in Technology; these missions are specifically designed to develop new space-based technologies. A sister mission, due for launch in June 2007 is SMART-2 , which will be a testbed for laser ranging. The technology will eventually be put to use by LISA (Laser Interferometry Space Antenna), a proposed ESA mission intended to look for the gravitational waves predicted by Einstein's General Theory of Relativity.
The knowhow obtained from SMART-2 will also prove instrumental in developing ESA's Infra-Red Space Interferometer, known informally as Darwin. Darwin, part of ESA's Horizons 2000 programme, will consist of 6 infra-red telescopes flying in precise formation, with the aim of performing nulling interferometry of nearby solar-type stars. Darwin will be sensitive enough to detect the infra-red absorption-line signatures of water, ozone and carbon dioxide in the atmospheres terrestrial-sized planets orbiting one of these stars; these signatures, if detected together, would amount to strong evidence for extraterrestrial life.
Tubal-Cain smokes the white owl.
The Italians had to fight tooth and nail to get the Vega launch system to be accepted by ESA for development. Part of it was, again, iirc, because it was would be separate from Arianespace. The whole point was to have an European developed follow-on for the Scout rockets that the Italians were building under license from the US.
The ATV is an excellent idea. I find it a little sad at this point that ESA hasn't successfully gone down the path of an independant manned space flight capability. Sure, they can use the Russians or the US or even the Chinese, I suppose, but it'd be interesting to see ESA come up with their own. I know they tried the Hermes space plane, but that turned out to be something of a boondoggle, didn't it?
Do you know why the road less traveled by is littered with the bones of the unwary?
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).
Jesus saves souls and redeems them for valuable cash prizes
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).
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"The ATV design strikes me as particularly interesting because it brings up a point that I've been wondering for awhile: Why don't we have more automated exploration and maintenance vehicles in Earth orbit. It seems to me that a spacecraft that could launch, orbit earth, and return to earth (not that the ATV can do that) without humans onboard and built in a mass manufactured way would be extraordinarily effective for Earth orbit science experiments. It might also be useful for maintenance of high value satellites (like HST). Since Earth orbit is almost real-time transmission there is no reason to think that putting a mechanical arm on a spacecraft to do maintenance would be any different that a surgeon doing a remote operation via a mechanical hand. The most complicated part would be the approach of the satellite to be maintained, but since the Space Shuttle obviously had no problem doing this there is no reason to believe that an automated spacecraft (with real-time human backup in a controlling station) couldn't do the same (a little more complicated than the ATV's purpose of docking with the ISS, but I don't think its inanely so).
Suddenly, the hairy finger of a familiar monkey tapped me on the shoulder. It was time.--G. T.
A little flash animation for those confused about ion drives: http://www.esa.int/export/esaSC/SEM3K81P4HD_index_ 0.html . Of course depends on mass, momentum, etc. too....
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.
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.
Still, it works, but it's not even as efficient as chemical rocketry
One word: fusion. As soon as fusion comes along, coupled with ion drives, chemical rocketry is history. Period.
Tubal-Cain smokes the white owl.
OTOH, a fairly fast trip to Mars requires about 20 kps in velocity changes. Which makes a 30 kps ion drive just about right.
But there's complexities there, too. Most of these velocity changes come at the beginning and end of the journey (getting into an elliptical orbit, then getting out of it once you reach Mars).
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.
Hear recorded Slashdot headlines on your phone! New service beta testing. Just call (248) 434-5508
Nine Planets has a big list of all spacecraft - past, current and future (although it is a little out of date).
Perhaps they are not the most efficient for Mars travel, but much beyond that, give me a break (having not done the math for Mars, I don't know). Chemical rockets spit far too much of their inital mass out the back to be even *somewhat* considered for longer term missions (remember the rocket equation?). There are several differnt kinds of "ion" engines all of which exceed 50% efficiency. At this point it becomes a bit more important to define "efficiency" - (power in)/(power out) may not necessarly be relevent if (mass start)/(mass end is near zero [what is the point of accelerating all of your "80%" fuel if you fling the crap out the back in a somewhat effiecent matter?) I may be (ok I am) a bit baises since I'm a grad student working in Ion Propulsion but the field obviously has merit or I would not have funding.
You said: "One word: fusion. As soon as fusion comes along, coupled with ion drives, chemical rocketry is history. Period.'
Unlikely.
There are two main designs for a fission rocket.
(1) To couple a semi-conventional PWR or BWR with an ion engine. The big downside to this is that you have to have a large secondary system to use the steam to make electricity. What this means is that you have to have a large heat sink (large radiators) and lots of moving parts. A design like the GT-MHR could simplify this, but not hugely so.
(2) Using a bladder of fuel (hydrogen, or water or whatever), you use this as coolant to a critical reactor that jets the superheated portion directly to space. The downside is that this doesn't make electricity, so you would have to divert some of the coolant (which requires construction of the additional secondary systems) or use solar panels or RTGs to electrically power the spacecraft (there will be additional power requirements due to reactor safety equipment).
There are two main designs for fusion power:
(1) Tokamak: basically shaped like a donut, a low atomic number elemental plasma is magnetically confined and heated (with I^2*R losses or X-rays) to the point where fusion occurs. The means of useful energy transfer is via neutrons emitted which hit a water tank surrounding the fusion reactor. From here its just like the secondary side of a normal fission nuclear reactor (ex 1 above).
(2) A pellet of low atomic number elements is simultaneously hit by energetic radition from all directions compressing it until fusion occurs. Heat transfer like above.
You could argue that either of these fusion reactions could operate like the fission reaction #2 above (with part of coolant directed to make electricity), but an important point is that a significant fraction of the energy released by fusion (if it ever produces more energy than is required to induce it) is required to sustain it. This requires the construction of a very large secondary system compared to that of the fission reactor (a lot more heat being transferred). Since a fission reactor will probably provide way more power than is needed anyways, there is no reason to build a much heavier fusion reactor.
Suddenly, the hairy finger of a familiar monkey tapped me on the shoulder. It was time.--G. T.
ESA has a long term exploration program called Aurora that aims to take humans to the Moon by 2020 and Mars by 2030. This was announced some time ago, well ahead of Bush's proclamation. The nearer term goals include ExoMars, a long-duration rover, and a Mars sample return mission with the ambitious launch date of 2011.
Beagle is alive! I just got a message from it in my inbox! Lemme double-click it and see what it says..
Oh.. wait...
They are not ignored by "mainstream" science. Mainstream science has already determined that they don't work.
So mainstream science "ignores" them only in the sense that they also ignore reading chicken entrails to fortell the future.
For starters, this is not a drive without a reaction mass. That's what the ball is.
When the ball hits the spring the spring compresses,i.e. deforms, otherwise it wouldn't be a spring, now would it? But only some of the energy of the ball goes into compressing the spring. Some of that energy goes into driving the entire tube "backwards." When the spring expands, again, some of that energy goes into driving the ball forwards, but some into driving the tube backwards again. In the process, as you note some energy is lost as heat.
When the ball "klunks" it drives the tube forward and the ball backward and some energy is lost as heat.
There is no essential difference between the spring and the klunk with regards to energy transfer other than the difference between the energy losses, as you note, which are very small (the klunk heats the ball more than the spring does).
What you have described is an oscillator that winds down after a relatively few klunks because energy is lost at each exchange. Use your brain. Analyze what "energy is lost" means.
It means the thingy goes back and forth a few times and then stops.
Unless you add energy.
By driving a reaction mass.
i.e. the ball.
And you still need a rocket to get it "up there" 'cause it ain't gonna do squat but fall over if you set it up on end and start it going here on earth. And that rocket has to carry the fuel to get the ball going in the first place, and all the fuel to keep it going, so that it can sit there in space and wobble until the fuel runs out. A quantity of fuel that still has to equal the energy value you intend to get out of the device.
This is nothing more than an obfuscated version of the drop hammer that lifts veeeeeeeeery slowly and thenswings down against a stop suddenly.
When the hammer lifts slowly the machine moves backwards slowly. When it swings down and hits the stop it moves forwards quickly but an equal distance less the heat loss in the impact versus the heat loss in the bearings as it rises and it needs fuel to drive it. Fuel which must be lifted into space and carried by the device. About the same amount of fuel that a conventional rocket uses.
And all it does is wobble.
KFG
> hasn't had much sucess lately (due to the
> Arianne and Beagle 2 fiascos)
Beagle 2 was a late "add on" to the Mars Express Mission... Beagle 2 was developed by the British. Attributing the failure of Beagle 2 to ESA is tantamount to saying there is UNIX code in Linux.
The Mars Express is SUCCESFULL, and is already returning clear stereo pictures of the Martian surface.
I am still sorry Beagle 2 failed.. but dont catogorise the whole mission a failure for ESA, just because of one part. rememebr the original mission did NOT include a lander....
Have a nice day!
It's interesting that one of ESA's greatest achievement areas, namely Earth Observation (things like ERS 1/2, Envisat) are not mentioned. This is an important area, with all the exciting stuff about oceans rising and engulfing towns and the Seychelles (serves them right for living in a bloody paradise :D). There are a large number of unknowns regarding the Earth's environment that could be alleviated by a (relatively) cheap fleet of EO microsatellites. I don't know whether ESA wants do commit more budget to these areas (after all, a lot of the stuff on Envisat is only of very limited commercial interest, and they seem to be pushing for commercial use), but it certainly would help. On the other hand, looking at the deforestation rate over Siberia might not be as cool as putting some gimp on the Moon...