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Helicon Double Layer Thruster

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I think this thing deserves its own thread.

This piece of is already from April 2009 but couldn't find but a few threads that mentioned the Helicon Double Layer Thruster and it wasn't there:

--- Quote ---“EADS-Astrium has decided to fund the University of Surrey to produce a prototype Helicon Double layer thruster suitable for space use. For this to occur the University of Surrey requires the expertise of the SP3 group here at ANU,” said Dr Charles. “It is our thruster which will show that this type of propulsion system is suitable for space use and space missions that EADS-Astrium will fund.”

The satellite will incorporate Dr Charles’ Helicon Double Layer Thruster (HDLT), which is not only an innovative electrode-less magneto plasma thruster but the first thruster of its kind in the world which will be applied to satellite station keeping and interplanetary space travel. Launched to low earth orbit, the satellite will test the thrusting capacity of Dr Charles’ HDLT in an orbital context.

--- End quote ---

This means a new type of plasma thruster is going to fly pretty soon! Maybe it will be good since it has few eroding parts, and thus one could do long thrusting times (tens of years).
In some senses, it seems a bit similar to VASIMR, but I don't know if the ISP can be varied...

You can also use multiple propellants in it:

--- Quote ---The characteristics of the ion beam versus operating pressure closely follow those previously obtained in argon, xenon and hydrogen. The ion beam exhaust velocity in space is found to be in the 17–19 km s−1 range in N2, 21–27 km s−1 range in CH4 and NH3 and 14–16 km s−1 range in N2O.
--- End quote ---

You might note that the Isp for this Double Layer Helicon plasma thruster is not very high with a 6,000 m/sec exhaust velocity (Isp ~ 600 seconds) per the below URL.

Edit:  And yes it appears to be able to get up over an Isp of 1,000 seconds dependent on selected propellant, but this approach is in no way competitive to the VASIMR...

What is its specific power or thrust/weight? VASIMR is .67 kw/kg (1.5kg/kw), and its efficiency is around 65%, and it operates between 2000-30000 ISP depending on propellant and how much thrust you need. How does this compare to the helicon double layer thruster?

The problem is often a too *high* ISP in electric propulsion. The propellant (reaction mass) isn't a large portion of the system weight, but it's dominated by power source mass. (With a constant reaction mass flow, power source scales to exhaust velocity ^2, thrust scales to exhaust velocity)

Though 600 s is low. You wouldn't use Xenon anyway for larger thrusters as its so scarce. Higher ISP with lighter materials, Argon seems to go to around 900 s, and I assume the molecular stuff I mentioned earlier breaks into even lighter ions which means even higher ISP. And it could be really easy to store.

There's a concept of optimal ISP for electric propulsion if you assume a certain power source mass, like 100 W / kg and a certain mission delta vee and required acceleration.

Power source mass is variable. It depends on many things. Like, are you using the standard solar arrays, which aren't better than 200W/kg, are you using today's best of 500W/kg, or are you using advanced concentrated or thin-film solar panels which are above 1kw/kg (possibly up to 5kw/kg eventually)?

Also, your distance from the sun GREATLY varies your solar panel specific power (Power is proportional to (distance to the sun)^-2), so much that being near Venus gives you about twice the specific power as being near Earth.

Also, you have nuclear power that could be used, which has its own range of specific power (but is not very related to distance from the Sun, in fact it works a little better further from the Sun because it's easier to shield your radiators or you don't need to shield the radiators, once you get really far away).

What is the specific power of these other propulsion technologies?

Obviously higher ISP means lower thrust for the same power, but if you are awash in plenty of power from either advanced solar panels or being closer to the Sun, then you are limited by the specific power of your ion propulsion system.

Again, WHAT IS THE SPECIFIC POWER or THRUST/MASS OF THESE OTHER PROPULSION TECHNOLOGIES??? For the Earth-Moon system, a newly developed spacecraft would be limited by the specific power of the engine as well as the power source. Soon, you could have solar power that has 1-2kw/kg, which would make the question of the specific power of your propulsion system even more important. You can figure the thrust/mass out by inputing the specific power, efficiency, and ISP. Thrust is inversely proportional to ISP, and directly proportional to specific power. So, if you increase specific power of your whole system by a factor of 2, then you can increase your ISP accordingly and get the same acceleration.

I think it is pretty silly to have solar power with only 100W/kg for a newly designed spacecraft that needs a lot of delta-v if you are about 1 AU away from the Sun. You should use much better solar panels! Obviously, you are stuck with lower specific power if you are at Mars or the asteroid belt, in which case you are around 100W/kg even with state-of-the-art.


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