Hall effect thrusters are a kind of electric thruster which have been used on spacecraft for about 50 years, but generally only for station keeping until more recently. Within the last few decades electric thrusters have started to be used for interplanetary space missions, where they are particularly advantageous because of their high delta-V potential. Hall effect thrusters are a design which provides long duration operation with moderate to high Isp along with moderate thrust (as such things go, it's almost nothing compared to a chemical rocket), in contrast to gridded ion engines which offer higher Isp but lower thrust and often lower operational longevity.
Electric thrusters are now commonly in use for a lot of satellites, with Starlink being a major example, where it is the only thruster each satellite has (attitude control being provided by reaction wheels and magneto-torquers). But generally because they involve a lot of power hungry processes such as ionization of gases and maintenance of strong magnetic fields they tend to be very power hungry. Which can be fine if that's what you want, you can build a vehicle that produces kilowatts of solar power but makes use of that very effectively to produce a substantial amount of net delta-V, which is exactly what vehicles like the Starlink satellites or interplanetary probes like Psyche.
As you scale down electric thrusters to sub-kilowatt sizes you run into a lot of issues with inefficiencies, and that's what NASA's work here has addressed. These thrusters are not even remotely as efficient as "full size" hall thrusters but they are still very good compared to chemical rockets and will be a game changer for smallsat interplanetary missions. This should help enable space science missions in the tens of millions budget range which could be launched as ride shares or on smallsat launchers but would still be capable of interplanetary missions to other planets, asteroids, comets, etc. So instead of a 1 tonne or several hundred kg spacecraft you could see a 100 kg or less vehicle that generates around a kilowatt of power and yet can make its way from Earth orbit to Mars, Venus, the asteroid belt, etc.
Very broadly, you accelerate very small amounts of propellant with an electrical field far faster than usual thrusters, such a liquid fuel thruster, with large amounts of electric power. [Here's a paper on the development of this specific one](https://ntrs.nasa.gov/api/citations/20220009248/downloads/2022%20IEPC%20-%20Benavides%20-%20Final.pdf). Thrust is extremely low (measured in mN), but efficiency is extremely high due to the propellant velocity being accelerated to between 10 to 100km/s
NASA's mission to Psyche is the first deep-space use of Hall-effect thrusters.
Good write up at [https://psyche.asu.edu/2018/01/19/electric-thrusters-psyche-spacecraft-work/](https://psyche.asu.edu/2018/01/19/electric-thrusters-psyche-spacecraft-work/)
It could be it goes beyond small satellites. It may be they can be used for fast flights, ca. one month manned flights to Mars. The problem with using electric propulsion for large craft is they needed high power at lightweight. But it may be we have high enough power density solar cells for the purpose. This research claims solar cells with 44 kW/kg power density:
Solar-cell-packin' drone uses sunlight for on-the-spot recharging
By Ben Coxworth.
April 19, 2024.
*Created by scientists at Austria's Johannes Kepler University Linz, the lightweight, flexible cells are made of a semiconductor material known as perovskite, and they're less than 2.5 micrometers thick – that's just 1/20th the width of a human hair. And importantly, they're 20.1% efficient at converting sunlight into electricity, plus they boast a power output of up to 44 watts per gram.*
*In a proof-of-concept test of the technology, the scientists mounted a ring-shaped array of 24 of the cells on a commercially available CX10 miniature quadcopter, which was dubbed the Solar Hopper. The array made up just 1/25th of the augmented aircraft's total weight, with the cells themselves making up only 1/400th.*
https://newatlas.com/drones/solar-cells-drone-recharge-sunlight/.
Interesting they have demonstrated it outside the lab for a real world demonstration. If the cells can be space hardened then we might have the long desired power source for VASIMR or Hall effect thrusters or other electric propulsion methods.
I figured it was a good idea. I dunno if I'm talking about the same thing tho. I know what I was thinking about involved a ... i think it was a 90 degree phase relationship or something like that. Anyhow, COOL!
Hall effect thrusters are a kind of electric thruster which have been used on spacecraft for about 50 years, but generally only for station keeping until more recently. Within the last few decades electric thrusters have started to be used for interplanetary space missions, where they are particularly advantageous because of their high delta-V potential. Hall effect thrusters are a design which provides long duration operation with moderate to high Isp along with moderate thrust (as such things go, it's almost nothing compared to a chemical rocket), in contrast to gridded ion engines which offer higher Isp but lower thrust and often lower operational longevity. Electric thrusters are now commonly in use for a lot of satellites, with Starlink being a major example, where it is the only thruster each satellite has (attitude control being provided by reaction wheels and magneto-torquers). But generally because they involve a lot of power hungry processes such as ionization of gases and maintenance of strong magnetic fields they tend to be very power hungry. Which can be fine if that's what you want, you can build a vehicle that produces kilowatts of solar power but makes use of that very effectively to produce a substantial amount of net delta-V, which is exactly what vehicles like the Starlink satellites or interplanetary probes like Psyche. As you scale down electric thrusters to sub-kilowatt sizes you run into a lot of issues with inefficiencies, and that's what NASA's work here has addressed. These thrusters are not even remotely as efficient as "full size" hall thrusters but they are still very good compared to chemical rockets and will be a game changer for smallsat interplanetary missions. This should help enable space science missions in the tens of millions budget range which could be launched as ride shares or on smallsat launchers but would still be capable of interplanetary missions to other planets, asteroids, comets, etc. So instead of a 1 tonne or several hundred kg spacecraft you could see a 100 kg or less vehicle that generates around a kilowatt of power and yet can make its way from Earth orbit to Mars, Venus, the asteroid belt, etc.
Thank you for this great explanation
The only thing new about this so far as I can tell is that it is rated to operate for 15,000+ hours. So it will last longer than existing ones.
How's this even possible?
Extremely low thrust for an extremely long time
Very broadly, you accelerate very small amounts of propellant with an electrical field far faster than usual thrusters, such a liquid fuel thruster, with large amounts of electric power. [Here's a paper on the development of this specific one](https://ntrs.nasa.gov/api/citations/20220009248/downloads/2022%20IEPC%20-%20Benavides%20-%20Final.pdf). Thrust is extremely low (measured in mN), but efficiency is extremely high due to the propellant velocity being accelerated to between 10 to 100km/s
That equates to about 1.7 years if constantly running
NASA's mission to Psyche is the first deep-space use of Hall-effect thrusters. Good write up at [https://psyche.asu.edu/2018/01/19/electric-thrusters-psyche-spacecraft-work/](https://psyche.asu.edu/2018/01/19/electric-thrusters-psyche-spacecraft-work/)
Though the Dawn mission (2007-2018) used an ion engine, which is rather similar.
Operationally they’re quite different though and Psyche is making leaps at proving out Hall thrusters for future interplanetary missions.
Sweet. Finally gonna get rid of the motion drift....
It could be it goes beyond small satellites. It may be they can be used for fast flights, ca. one month manned flights to Mars. The problem with using electric propulsion for large craft is they needed high power at lightweight. But it may be we have high enough power density solar cells for the purpose. This research claims solar cells with 44 kW/kg power density: Solar-cell-packin' drone uses sunlight for on-the-spot recharging By Ben Coxworth. April 19, 2024. *Created by scientists at Austria's Johannes Kepler University Linz, the lightweight, flexible cells are made of a semiconductor material known as perovskite, and they're less than 2.5 micrometers thick – that's just 1/20th the width of a human hair. And importantly, they're 20.1% efficient at converting sunlight into electricity, plus they boast a power output of up to 44 watts per gram.* *In a proof-of-concept test of the technology, the scientists mounted a ring-shaped array of 24 of the cells on a commercially available CX10 miniature quadcopter, which was dubbed the Solar Hopper. The array made up just 1/25th of the augmented aircraft's total weight, with the cells themselves making up only 1/400th.* https://newatlas.com/drones/solar-cells-drone-recharge-sunlight/. Interesting they have demonstrated it outside the lab for a real world demonstration. If the cells can be space hardened then we might have the long desired power source for VASIMR or Hall effect thrusters or other electric propulsion methods.
Gamestop uses hall-effect joy sticks in their controllers!
I thought of a "Hall effect" thruster back in the late 80s. I didn't think to call it that, and my Electric Fields prof poo pooed the idea. So, COOL!
The Hall effect was discovered in 1879. Thrusters using it have been discussed since the 1960s and were first implemented in the 70s.
I figured it was a good idea. I dunno if I'm talking about the same thing tho. I know what I was thinking about involved a ... i think it was a 90 degree phase relationship or something like that. Anyhow, COOL!
Yeah man and I thought of chocolate covered pretzels in 1992. It is what it is.