Author Topic: Ion Thruster Prototype Breaks Records in Tests, Could Send Humans to Mars  (Read 5431 times)

Offline Star One

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A thruster that's being developed for a future NASA mission to Mars broke several records during recent tests, suggesting that the technology is on track to take humans to the Red Planet within the next 20 years, project team members said.

The X3 thruster, which was designed by researchers at the University of Michigan in cooperation with NASA and the U.S. Air Force, is a Hall thruster a system that propels spacecraft by accelerating a stream of electrically charged atoms, known as ions. In the recent demonstration conducted at NASA's Glenn Research Center in Ohio, the X3 broke records for the maximum power output, thrust and operating current achieved by a Hall thruster to date, according to the research team at the University of Michigan and representatives from NASA.

"We have shown that X3 can operate at over 100 kW of power," said Alec Gallimore, who is leading the project, in an interview with Space.com. "It operated at a huge range of power from 5 kW to 102 kW, with electrical current of up to 260 amperes. It generated 5.4 Newtons of thrust, which is the highest level of thrust achieved by any plasma thruster to date," added Gallimore, who is dean of engineering at the University of Michigan. The previous record was 3.3 Newtons, according to the school.

https://www.space.com/38444-mars-thruster-design-breaks-records.html

Online spacenut

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I think the thrusters should use argon.  Mars' atmosphere is about 3% argon.  It is also more plentiful on earth.  It may not give as high a thrust or it may be a little more bulky than xenon, but a large spacecraft that would fly between earth and Mars could have a pre launched lander pulling argon out of the atmosphere, then launch it up to dock with an incoming ship from earth to refuel for the crew return to earth.  If a lot of travel is to eventually be done between earth and Mars, argon may be the way to go. 

One could use Vasmr thrusters that can use almost any gas, even oxygen to ionize.  They take more power and a larger amount of propellant, but, still less mass than chemical brute force. 

Offline john smith 19

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https://www.space.com/38444-mars-thruster-design-breaks-records.html
That's impressive as a single unit. Previously people have been talking about clusters of ion thrusters to get this, and that can cause problems.

On a 400 tonne spacecraft that 5.4N gives an acceleration of about 1.37 micro g.  That's roughly a speed increase of 1 m/s every 74 seconds. 74 000 seconds, or 20 hours. 

The problem is the 100Kw needed to power the thing.
« Last Edit: 10/14/2017 09:19 AM by john smith 19 »
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline Star One

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https://www.space.com/38444-mars-thruster-design-breaks-records.html
That's impressive as a single unit. Previously people have been talking about clusters of ion thrusters to get this, and that can cause problems.

On a 400 tonne spacecraft that 5.4N gives an acceleration of about 1.37 micro g.

The problem is the 100Kw needed to power the thing.

Nuclear power?

Offline IRobot

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It's 5.4N for 100KW, which is more than double of the 5N for 200KW for VASIMR.

Offline sanman

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I think the thrusters should use argon.  Mars' atmosphere is about 3% argon.  It is also more plentiful on earth.  It may not give as high a thrust or it may be a little more bulky than xenon, but a large spacecraft that would fly between earth and Mars could have a pre launched lander pulling argon out of the atmosphere, then launch it up to dock with an incoming ship from earth to refuel for the crew return to earth.  If a lot of travel is to eventually be done between earth and Mars, argon may be the way to go. 

One could use Vasmr thrusters that can use almost any gas, even oxygen to ionize.  They take more power and a larger amount of propellant, but, still less mass than chemical brute force.

Carbon fullerenes and buckyonions are relatively easily ionizable, and have been tested for use in ion thrusters. They have high molecular weights which improves thrust, and carbon is present in the Martian atmosphere.
« Last Edit: 10/14/2017 02:26 AM by sanman »

Offline savuporo

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The problem is the 100Kw needed to power the thing.

Not really, 100kW arrays are on the radar, with specific power of 150w/kg.
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Offline envy887

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https://www.space.com/38444-mars-thruster-design-breaks-records.html
That's impressive as a single unit. Previously people have been talking about clusters of ion thrusters to get this, and that can cause problems.

On a 400 tonne spacecraft that 5.4N gives an acceleration of about 1.37 micro g.  That's roughly a speed increase of 1 m/s every 74 seconds.

The problem is the 100Kw needed to power the thing.

You lost a kilo there somewhere. Either 400 kg craft, or 74,000 sec.

Offline john smith 19

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You lost a kilo there somewhere. Either 400 kg craft, or 74,000 sec.

Ooops.  :( I should have realized that was too good to be true.  So 1 m/s faster about every 20 hours.
The downside for ITS would be you've basically added 50% to the power requirement

Not really, 100kW arrays are on the radar, with specific power of 150w/kg.
The ISS array is 200Kw but it's also pretty heavy. If that number's real then you have an array below a tonne. That suggests it could still generate significant power even in the outer planets, although solar levels at 30AU are 1/900 that at Earth.

It's 5.4N for 100KW, which is more than double of the 5N for 200KW for VASIMR.
I did not know that

I guess VASIMIR could still have the edge in Isp or ability to use different fuels?
Either way you're committed to a very serious power supply, and that won't be cheap.

Nuclear power?
In theory yes,  in practice no.

The Kilopower test of the first space rated nuclear reactor for electrical generation to be designed in the US since the early 60's is for 1Kw, with the Mars version up to 10Kw, although IIRC they have a road map up to 1MW. Tiny by power grid utility standards, huge by those of space systems.

AFAIK the Kilopower team are hard at work on their Nov/Dec live ground test at the Nevada Test Site. IMHO this is a critical test for the future of the use of fission generated electric power in space. A near nominal (because nothing goes perfectly in these situations) would be a huge step forward.

What NASA needs for probes is basically a 10Kw thruster (to match a 10Kw Kilopower package), but none of the units for comm sats are that big, and apparently they are difficult to cluster.
« Last Edit: 10/14/2017 09:16 AM by john smith 19 »
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline savuporo

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Not really, 100kW arrays are on the radar, with specific power of 150w/kg.
The ISS array is 200Kw but it's also pretty heavy. If that number's real then you have an array below a tonne. That suggests it could still generate significant power even in the outer planets, although solar levels at 30AU are 1/900 that at Earth.

You have to remember that ISS was designed 30 years ago. That number is from ROSA and ATK UltraFlex/MegaFlex designs. ROSA is getting commercialized by SSL geosat platforms, by the way.

« Last Edit: 10/14/2017 06:10 PM by savuporo »
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Offline MP99

Why would they not quote the Isp?

Cheers, Martin

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Offline Comga

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Why would they not quote the Isp?

Cheers, Martin

An excellent question.

Searching for that value leads to Edward Florenz's 2014 thesis on the X-3 100 kW 5 N Hall Thruster.

Skimming the 169 (!) pages failed to produce that value.  It is attached. 

Edit:  Figures 6.1 thru 6.8 on page 99-105 show "anode Isp" of ~2370 sec. (The attached image has a purple and yellow circle for the approximate point on the graph)

Figure 1.1 shows historical values of IsP vs thrust for all sorts of engines.  Hall thrusters top out around 3000 sec, although the highest value for a flight system was ~2000 sec.  The Isp for X-3 falls between these values.
« Last Edit: 10/14/2017 08:10 PM by Comga »
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline Comga

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Figures 6.1& 6.7 from Florentz
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline john smith 19

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Why would they not quote the Isp?

Cheers, Martin

An excellent question.

Searching for that value leads to Edward Florenz's 2014 thesis on the X-3 100 kW 5 N Hall Thruster.

Skimming the 169 (!) pages failed to produce that value.  It is attached. 

Edit:  Figures 6.1 thru 6.8 on page 99-105 show "anode Isp" of ~2370 sec. (The attached image has a purple and yellow circle for the approximate point on the graph)

Figure 1.1 shows historical values of IsP vs thrust for all sorts of engines.  Hall thrusters top out around 3000 sec, although the highest value for a flight system was ~2000 sec.  The Isp for X-3 falls between these values.
That's interesting. VASIMR is meant to have an exhaust velocity of 50 Km/s or an Isp of > 5 000 secs. It also implies that doubling the power level wouldn't give you  double the Isp as they seem to top out at 3 000 secs.

So (on the same fuel) VASIMR could give double the Isp at double the power input (or double the Isp at substantially lower thrust for the same power ?)

I guess it depends on what's more important to the mission planners, Isp or power generating capacity
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline tea monster

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I made a model of one of an advanced ion engine ship with X3 thrusters. It uses mega-rosa arrays.

Offline Nilof

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You lost a kilo there somewhere. Either 400 kg craft, or 74,000 sec.

Ooops.  :( I should have realized that was too good to be true.  So 1 m/s faster about every 20 hours.
The downside for ITS would be you've basically added 50% to the power requirement

Keep in mind that the thruster only weighs 200 kg, so you're only devoting one 2000th of the spacecraft to SEP propulsion. Don't expect a miracle. Dedicate 5% of the mass to propulsion and suddenly you're going to get much more delta-v.

I made a model of one of an advanced ion engine ship with X3 thrusters. It uses mega-rosa arrays.
(image)

Oh I remember seeing you post that render in the SEP threads a couple of years back, and tweaking it to get it to look perfect. There was a lot of discussion about the X3 thruster back then. The render is a great illustration of what a SEP spacecraft would look like. You can also take the propulsion element as a standalone tug and have it push a docked ship (like the BFS). The thrusters can gimbal easily to thrust through the COM and the bending moments with SEP are going to be fairly small.
« Last Edit: 10/14/2017 11:54 PM by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline Nilof

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Also worth noting is that the X3 thruster was the baseline for the COMPASS mars mission study from  few years ago which considers SEP/Chem in a NASA DRM-5 equivalent mission: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140002512.pdf

Regarding specific impulse the compass study mentions this:

"The X3-80 nested Hall thruster operates at nominally 250 A when all channels are operating, and it can be operated at 175 kW at 700 V (3000 s Isp), 125 kW at 500 V (2400 s Isp), or at 75 kW at 3000 V (2000 s Isp). "

So the specific impulse depends on the voltage you feed it, typically both Isp and thrust scale as roughly as the square root of the voltage you run an electric thruster at. Voltage is directly proportional to the power that isn't spent on ionization if the mass flow is kept constant.

I do know that for the X3 you're supposed to be able to run a subset of the rings at higher power/voltage to get "gears" like Vasimr, i.e. run at a lower thrust but higher ISP, or higher thrust lower ISP when everything is on.
« Last Edit: 10/15/2017 12:26 AM by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline Robotbeat

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By the way, one of the ADVANTAGES of Hall Effect thrusters are their lower Isp.

Low Isp means you can get more thrust out of the same power, meaning your burn can be much shorter for the same impulse.

Too high of an Isp is actually very suboptimal.
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Offline aceshigh

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By the way, one of the ADVANTAGES of Hall Effect thrusters are their lower Isp.

Low Isp means you can get more thrust out of the same power, meaning your burn can be much shorter for the same impulse.

Too high of an Isp is actually very suboptimal.

usually, not always.

nuclear-salt water rocket concept for example... 13 meganewtons of thrust at 66 km/s exhaust velocity...

Offline Star One

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I imagine this would be ideal for something like a Pluto orbiter.

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