Europeans And Australians Make Space Propulsion Breakthrough

[rlb2]

The European Space Agency and the Australian National University have successfully tested a new design of spacecraft ion engine that dramatically improves performance over present thrusters and marks a major step forward in space propulsion capability.<br /><br />Ion engines are a form of electric propulsion and work by accelerating a beam of positively charged particles (or ions) away from the spacecraft using an electric field. ESA is currently using electric propulsion on its Moon mission, SMART-1. The new engine is over ten times more fuel efficient than the one used on SMART-1. “Using a similar amount of propellant as SMART-1, with the right power supply, a future spacecraft using our new engine design wouldn’t just reach the Moon, it would be able to leave the Solar System entirely,” says Dr Roger Walker of ESA’s Advanced Concepts Team, Research Fellow in Advanced Propulsion and Technical Manager of the project<br /><br />Since they must operate continuously in space for tens of thousands of hours providing a small thrust, ground tests in a vacuum facility must last several thousand hours to prove their reliability. Only after all this could the first flight models be launched.<br />Once ready, these engines will be able to propel spacecraft to the outermost planets, the newly discovered planetoids beyond Pluto and even further, into the unknown realm of interstellar space beyond the Solar System. Closer to home, these supercharged ion engines could figure prominently in the human exploration of space. With an adequate supply of electrical power, a small cluster of larger, high power versions of the new engine design would provide enough thrust to propel a crewed spacecraft to Mars and back.<br /><br />“This is an ultra-ion engine. It has exceeded the current crop by many times and opens up a whole new frontier of exploration possibilities,” says Dr Walker.<br /><br />http://www.scien <div class="Discussion_UserSignature"> Ron Bennett </div>

 

[john_316]

Is it any better than the NEXIS engine?

 

[JonClarke]

It's hard to compare the two, as NEXIS is a much more developed engine. the ANU study is still at the prelinary concept trials stage. However NEXIS is supposed to have an exhaust velocity of 80 km/s, this thruster has a velocity of 210 km/s, 2.5 times as fast.<br /><br />The ANU team led by Rod Boswell have done some very innovative work, their Helicon thruster has the potential, according to talks I have heard, of delivering similar performance to VASIMR but using much simpler technology. They also have improved the focus of the plasma beam, leading to more efficient thrust, and significantly reduced the degree to which the grids are eroded, which improves the life of the thuster immensely.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[chriscdc]

Can someone explain why using 4 grids, with 2 high and 2 low, avoids the collision problem that 2 grids face?

 

[cuddlyrocket]

If I understand things correctly, I think it works as follows:<br /><br />Ion engines work by accelerating positive ions (atoms with electrons missing) using an electric field. The field is generated between two plates, with a potential difference (voltage) between them - usually one is negative, the other positive. The ions move away from the positive, towards the negative. The negative plate has holes in it, so that the ions can get out the back! Obviously you want the ions to go through the holes, rather than hit the plate, causing erosion etc, and which is done by designing the fields carefully etc.<br /><br />The greater the potential difference, the faster the ions, but that means you have less time to control them, and need to put more force into changing their direction, and the net result is that more of them hit the plate instead of going through the holes.<br /><br />With the four plate system, the first two plates are both positively charged, but one more than the other. The potential difference is quite low, and this makes it easier to produce a nice beam of ions through the holes in one plate. The second set of plates are negatively charged, but with a much greater potential difference between them and the positive plates. As you are already dealing with a beam of ions going in the direction you want then, despite the higher velocities, it is a lot easier to make them go through the holes in the negative plates.

 

[grooble]

Could you do 6 and 8 plates to make it even faster?

 

[mlorrey]

How does it compare to the VASIMR? As I recall, the VASIMR is the one that pioneered the use of the Helicon device.

 

[ragnorak]

<br />I doubt it but it certainly overcomes the technical problems with boosting the ISP on the two grid system, namely the engine degradation. Maybe this is Europe's route to their own Prometheus mission - but a bit more successful! ;-)

 

[mikejz]

Yeah, I'll eat my words the first time Europe launches a nuclear mission.

 

[JonClarke]

Meaning what exactly?<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[krrr]

<font color="orange">Yeah, I'll eat my words the first time Europe launches a nuclear mission.</font><br /><br /><font color="yellow">Meaning what exactly?</font><br /><br />Probably meaning that Europe won't (in the foreseeable future) launch a nuclear (reactor) mission.<br /><br />Since NASA is abandoning all advanced propulsion concepts, ESA (or Russia) might have a chance to demonstrate the benefits of Solar Electric Propulsion. <br />

 

[nacnud]

We already have, forgotten SMART 1 already?<br /><br />You probably mean for manned missions but I would have though an interplanetary probe mission using these new ion engins would happen first.<br /><br />How about a tour of the minor planets inside Jupiters orbit? That should test solar cells and the ion engines to the limit.

 

[rlb2]

The breakthrough announced above is astounding and is comparable to the proposed VASMIR engine, high kudos for the Ausse's and ESA, if it ever gets off the ground, but you need energy to propel these new propulsion systems - where is that coming from.....<br /><br /><font color="orange">Probably meaning that Europe won't (in the foreseeable future) launch a nuclear (reactor) mission.<font color="white"> <br /><br />I digress.<br /><br />You would need RTG's maybe but not necessarily nuclear propulsion rockets and or nuclear electric energy propulsion unless you plan a manned mission beyond Jupiter. The budget for nuclear propulsion in the USA by NASA has been cut. <br /><br />I was at a conference where the Russian were considering nuclear electric propulsion an ion or hall effect engine, American were proposing a nuclear thermal drive engine, why build an convertible to electricity to another form of propulsion when you don’t need it, was the mind set of the lead scientist from the USA. The energy to drive these things, Ion drive, Hall Effect, VASIMER etc. needs to come from somewhere. <br /><br />You don't need fissionable nuclear anyway for exploration of the inner solar system. In fact it would be more of a burden than it would be worth......Think concentrated solar cells, Boeing has developed concentrated solar cells that are operational today that can take 250 sol’s of energy, if the suns energy was striking the earth surface it would be multiplied by 250 times with a solar concentrator, turn it into electricity at approximately 40 percent efficiency. Now go beyond that to monochromic light beam where it is possible to convert up to 80 percent of the monochromic light striking the cells to electricity and Bammmmmmmm…………<br /><br />Future manned propulsion to the otter solar system and beyond may be beamed energy with nuclear fission or fusion as backup only…….Why go up to 10 percent the speed of light when you can go light speed, unless you perfected a way to tap into virtual</font></font> <div class="Discussion_UserSignature"> Ron Bennett </div>

 

[JonClarke]

ESA has no firm plans for any mission that might need NEP. But since the Europeans haved alrwady had one nuclear powered mission, the RTG equipped Ulysses solar polar mission I don't see why they not use such technology if required.<br /><br />However, although the big story aspect of the ANU research is applications to human missions and deep space probes, the big, immediate application is to more effcient station keeping for commerical satellites. <br /><br />There has been a lot of funding of this work from several governments and there is a lot of commercial interest too, I understand.<br /><br />Jon<br /><br /> <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[yurkin]

nancud<br />Less we forget, Smart uses Solar electric propulsion.<br />but re reading the thread i think thats what u meant.<br /><br />Jon<br />I had forgotten about Ulysses. It may have been an ESA mission but the generator was built by the US Department of Energy. Presently there are not plans for development of a European RTG, or even of a nuclear powered mission. And I have to see I don’t see that changing in the foreseeable future. <br />But nuclear missions are generally very expensive so perhaps this has as much to do with it as anything else.

 

[mikeemmert]

<blockquote><font class="small">In reply to:</font><hr /><p>Think concentrated solar cells, Boeing has developed concentrated solar cells that are operational today that can take 250 sol’s of energy, if the suns energy was striking the earth surface it would be multiplied by 250 times with a solar concentrator, turn it into electricity at approximately 40 percent efficiency. Now go beyond that to monochromic light beam where it is possible to convert up to 80 percent of the monochromic light striking the cells to electricity and Bammmmmmmm………… <p><hr /></p></p></blockquote><br /><br />I've often wondered about making a solar concentrator using a diffraction grating. Diffraction grating lenses have been mads. They are cheaper and easier to produce than conventional mirrors or lenses, using photolithographic techniques to make them and requiring considerably thinner films of material than either conventional lenses or mirrors.<br /><br />If you look at a CD, you can't help but notice chromatic abberation. For telescopes, it's interesting to notice that the chromatic abberation is backwards, i.e. red light is bent more than blue, thus a combination of conventional lens and diffraction grating lens cancels chromatic abberation.<br /><br />But for a solar collector, you WANT chromatic abberation, which you can get from either conventional or diffraction grating lenses. The trick here is to have different kinds of solar cells at the focus for each color, thus improving efficiency. Colors (blue, UV, IR) to which solar cells are not sensitive could be allowed to pass through the system, thus they would not contribute to heating the cells.<br /><br />I know nothing of the Boeing system, I thought of this myself after reading about diffraction grating lenses in the print version of Scientific American. I wouldn't be surprised if the Boeing system is similar.<br /><br />Could you provide a link?<br /><br />Personally, though, for propulsion I would prefer a gas-core nuclear reactor and get some

 

[mikejz]

Actually, I have to find the link--but there was an academic paper done on using flexible Fresnel lenses as solar concentrators--that would lay flat until the array was deployed and then extend. It seemed like a very attractive technology.

 

[mikeemmert]

Happy hunting. My source (Scientific American print) is not on the web.<br /><br />It seems to me that Fresnel lenses would not be as robust as diffraction gratings. The ridges on the Fresnel lens could distort when they are rolled up or in a million other dings and accidents, but diffraction gratings are flat, so there's nothing to distort.

 

[JonClarke]

Like I said, apart from a Europa mission, there isn't a flight being discussed that needs nuclear. All the other ESA plans are for the Moon, Mars, Mercury, and Venus. So no need for RTGs. <br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[mikeemmert]

You guys worry too much about nuclear power. People accept it in spacecraft when it's needed.

 

[rlb2]

Here are some links.<br /><br />http://www.boeing.com/news/releases/2003/q3/nr_030918o.html<br />http://www.boeing.com/news/releases/2003/q3/nr_030725s.html<br />http://www.renewableenergyaccess.com/rea/news/story;jsessionid=a9jjmhoRnGa9?id=34626<br /><br /><br />Below is my rendered image of a solar concentrator type that I favor using in space. The concentrator umbrella parabolic shape would be made out of thin low mass reflective material that would unfold in space.<br /><br />The image below is at:<br /><br />http://arrow-space-innovations.com/ <div class="Discussion_UserSignature"> Ron Bennett </div>

 

[JonClarke]

The rate at which solar technology is advancing is staggering. Fiften years ago space solar arrays were 10% efficient. Current space qualified systems are 20%. Thin film arrays with masses of 0.2 kg/m2 and over 30% efficiency are under development. Efficiencies of up to 70% may be possible with current technology. There is tremendous synergy with terrestrial and space applications in the field. <br /><br />Jon<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[rlb2]

I agree it sure is a good time to apply what we have today into a viable re-usable space transportation system to take us to the moon and Mars. The risk to humans in transit to Mars would be drastically reduced if we can get there a lot faster. <div class="Discussion_UserSignature"> Ron Bennett </div>

 

[najab]

><i>Efficiencies of up to 70% may be possible with current technology.</i><p>I'd buy 40-50% with current technology, but 70%? Nah.</p>

 

[mikeemmert]

Thanks for the links, rib2.<br /><br />Reading them, I see hints that they are in fact taking advantage of chromatic abberation. That might be a trade secret. It would increase the efficiency of solar cells. As you have stated in an earlier post, if the color falling onto a solar cells matches the color of the cell's peak efficiency, conversion of at least 80% is possible (I've heard 90%).<br /><br />About the engine (after all, the thread started on that), I wonder what the thrust/weight ratio is? Specifically, I wonder if it can accelerate a reasonable payload at 2 g's if it had a high powered energy source? If so, gravitational boosts with power assist are possible.<br /><br />This would be most useful for powering infrared telescopes outside of the plane of the ecliptic. There is significant interference from dust and particles floating around there. That messes up the signal-to-noise ratio.