ESA's Dual Stage 4 Grid Ion propulsion

[Astronuc]

Is it possible to build an ion thruster that can accomodate multiple types of propellant? For example able to use Xenon but can also use Hydrogen

Certainly. If one reads various studies, one finds that thrusters have been tested with different propellants.

However, it is unlikely that a propulsion system would use alternative propellants during a mission. If hydrogen offered superior performance, then hydrogen would be used throughout the mission.

when you run out of Xenon in space you can mine some water and extract the hydrogen and use it?

Current practice is to carry propellant with the craft until mission is completed. Mining water to extract hydrogen would require an entirely different infrastructure. I would imagine that a plant would be established whereby a transport ship docks with a refueling station near or en route to a destination. It would make more sense to extract ammonia or methane from a moon, e.g., Titan (Saturn), that is rich in hydrogen.

https://www.nasa.gov/mission_pages/cassini/media/methane20060302.html

However, let's not get to far off topic, which is the DS4G, which is a type of electrostatic thruster.
https://beyondnerva.com/electric-propulsion/gridded-ion-thrusters/

In theory, the DS4G is more efficient in terms of I_sp, e.g., 10000-15000 (using Xe), compared to about 4000-8000 for more conventional grid thrusters. The greater I_sp, the lower the thrust for a given power level. The 'best' thrust reported for the DS4G was 5.4 mN vs 237 mN for NEXT-C. However, NEXT-C used approximately 6.9 - 7 kW, vs about 0.61 kW for DS4G. One really needs to compare technologies on the same basis, e.g., same kW level, and mass flow rate.

Erosion of the grid is a long term problem.
https://beyondnerva.com/electric-propulsion/gridded-ion-thrusters/

 

[darkdave3000]

Certainly. If one reads various studies, one finds that thrusters have been tested with different propellants.

However, it is unlikely that a propulsion system would use alternative propellants during a mission. If hydrogen offered superior performance, then hydrogen would be used throughout the mission.Current practice is to carry propellant with the craft until mission is completed. Mining water to extract hydrogen would require an entirely different infrastructure. I would imagine that a plant would be established whereby a transport ship docks with a refueling station near or en route to a destination. It would make more sense to extract ammonia or methane from a moon, e.g., Titan (Saturn), that is rich in hydrogen.

https://www.nasa.gov/mission_pages/cassini/media/methane20060302.html

However, let's not get to far off topic, which is the DS4G, which is a type of electrostatic thruster.
https://beyondnerva.com/electric-propulsion/gridded-ion-thrusters/

In theory, the DS4G is more efficient in terms of I_sp, e.g., 10000-15000 (using Xe), compared to about 4000-8000 for more conventional grid thrusters. The greater I_sp, the lower the thrust for a given power level. The 'best' thrust reported for the DS4G was 5.4 mN vs 237 mN for NEXT-C. However, NEXT-C used approximately 6.9 - 7 kW, vs about 0.61 kW for DS4G. One really needs to compare technologies on the same basis, e.g., same kW level, and mass flow rate.

Erosion of the grid is a long term problem.
https://beyondnerva.com/electric-propulsion/gridded-ion-thrusters/

I thought DS4G solves the problem of erosion????

Also thought you might want to see this:

The left rectangular is using your numbers, looks like according to you the Dual Stage 4 Grid has a better power efficiency. But on my right with the numbers I extracted from the wikipedia the numbers are shifted in favor of Next-C. I guess maybe I got theoretical numbers.

 

[Astronuc]

The left rectangular is using your numbers, looks like according to you the Dual Stage 4 Grid has a better power efficiency.

They are not 'my' numbers. I did not do the tests, nor measure performance. I simply reported what is cited in the literature. I've not made any endorsement, expressed or implied, regarding the validity of the data. I do point out that one must compare different technologies on an equal basis.

I thought DS4G solves the problem of erosion????

It's a 'gridded' technology. Metal grids are subject to erosion from the impingement of atoms/ions, which pass through the grids. The greater the speed (kinetic energy) of the ions/atoms, the greater the erosion potential for a given fluid density, as well as temperature of the grid.

As I've indicated, further development of the DS4G is required.

 

[darkdave3000]

They are not 'my' numbers. I did not do the tests, nor measure performance. I simply reported what is cited in the literature. I've not made any endorsement, expressed or implied, regarding the validity of the data. I do point out that one must compare different technologies on an equal basis.It's a 'gridded' technology. Metal grids are subject to erosion from the impingement of atoms/ions, which pass through the grids. The greater the speed (kinetic energy) of the ions/atoms, the greater the erosion potential for a given fluid density, as well as temperature of the grid.

As I've indicated, further development of the DS4G is required.

Can you reply my conversation I started with you?
https://www.physicsforums.com/conversations/the-space-plane-corporation.240119/#convMessage-362895

 

[Peter034]

The answer is not simple, because is depends on the thermodynamic efficiency of the entire system. We were targeting 100 MWe from 300 MWt, or about 0.33 efficiency, which could be greater or lesser depending on the thermodynamic cycle for thermal to mechanical conversion. I don't have my notes at hand, but it was something like 100 MWe and perhaps 10 tonnes (metric tons, or 1000 kg) for the reactor, or about 10 MWe/tonne, or 10 kWe/kg. However, one has to consider the rest of the mass of all the equipment, which would reduce about an order or magnitude, or about 1 kWe/kg. As mentioned earlier, the radiator was the single largest mass. The mass depends on how much heat must be rejected (area), the temperature at which the radiator operates, and the alloys used to construct the radiator.

Well that's real interesting. I can engineer how to fix my garage but when I tried to imagine a hundreds of megawatts radiator fit for an advanced propulsion system in near space then it started out looking like about 88 watts per kilogram with the latest thermal salt which would not have been known to science 35 years ago. If maybe you call that kind of stuff a coolant then I am curious what kind of it you would have been using for temperatures in the vicinity of 1500 K?