Author Topic: Powerful Krypton Ion Engine/Mars SEP  (Read 22907 times)

Offline Tywin

Powerful Krypton Ion Engine/Mars SEP
« on: 04/07/2021 11:01 pm »
Should Spacex invest in a powerful ion engine of Krypton, for a Mars SEP?
« Last Edit: 10/14/2022 07:46 am by zubenelgenubi »
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Offline Vultur

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Re: Powerful Krypton Ion Engine...Mars SEP...
« Reply #1 on: 04/08/2021 03:52 am »
Not yet - they have enough on their plates!

In the long run, after Starship's development is finished, it might make sense, depending on what else is going on, and what SpaceX wants to do other than Mars and Starlink.

Offline Robotbeat

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Re: Powerful Krypton Ion Engine...Mars SEP...
« Reply #2 on: 04/08/2021 04:09 am »
It doesn't really make sense for crew transfer given SpaceX's approach with Starship, but depending on how much SEP costs and launch costs, then it might make sense for cargo and propellant.
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Offline ZachF

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Re: Powerful Krypton Ion Engine...Mars SEP...
« Reply #3 on: 04/08/2021 01:36 pm »
It doesn't really make sense for crew transfer given SpaceX's approach with Starship, but depending on how much SEP costs and launch costs, then it might make sense for cargo and propellant.

It would probably need something cheaper than krypton.

Best I can tell, the cost of Krypton is around $300 per kg.

Assuming an ISP of ~2000, a cargo tug with the dV to go to Mars orbit and back with ~half it's non-fuel weight in cargo is going to require each Kg of cargo requiring more than it's mass in Krypton, so that's over $300/kg in just fuel, nevermind the amortized cost of the tug itself.

If Cargo Starship can launch for $15m and tankers for $10m, that's $300/kg for a 3x refill flight.
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Offline Robotbeat

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Re: Powerful Krypton Ion Engine...Mars SEP...
« Reply #4 on: 04/08/2021 01:43 pm »
It doesn't really make sense for crew transfer given SpaceX's approach with Starship, but depending on how much SEP costs and launch costs, then it might make sense for cargo and propellant.

It would probably need something cheaper than krypton.

Best I can tell, the cost of Krypton is around $300 per kg.

Assuming an ISP of ~2000, a cargo tug with the dV to go to Mars orbit and back with ~half it's non-fuel weight in cargo is going to require each Kg of cargo requiring more than it's mass in Krypton, so that's over $300/kg in just fuel, nevermind the amortized cost of the tug itself.

If Cargo Starship can launch for $15m and tankers for $10m, that's $300/kg for a 3x refill flight.
Agreed. Argon is super cheap and is available on Mars and Earth as a byproduct of atmospheric harvesting of gases for launch vehicles (nitrogen and oxygen on Earth, CO2 on Mars).
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Offline Robotbeat

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Re: Powerful Krypton Ion Engine...Mars SEP...
« Reply #5 on: 04/08/2021 01:51 pm »
Martian Argon is one of the most interesting options. Could potentially launch it cheaper from Mars than from Earth. And the high Isp means you could get to Earth with most of your propellant. Of course, same logic goes the other way.

Probably for a long time, just Earth launch chemical rockets (with ISRU on Mars only for return) will be what is cheapest. Then maybe SEP with Argon from Earth to reduce Earth launch costs. Then maybe Argon and propellant delivered from Mars, when there is huge demand for Earth-Mars transport. Allowing you to offload energy costs and launch rate from Earth, so you only launch up people and rare/expensive hardware to LEO and the Mars ISRU-based transportation system does the rest. That’d cut down on require Earthside launch by a good factor of 10 or more. But not before you’ve got Gigawatts of power on Mars and massive infrastructure in place.
« Last Edit: 04/08/2021 01:52 pm by Robotbeat »
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Offline spacenut

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Re: Powerful Krypton Ion Engine...Mars SEP...
« Reply #6 on: 04/08/2021 01:57 pm »
Vasimr engines, from what I understand, can use oxygen for propellant.  Not as efficient as using more expensive propellants, but could use this cheaper method for taking non perishable cargo to Mars via slow route. 

I also agree, argon would be better for more efficient thrusters. 

I also think building a very large Nautilus X type, in space only spacecraft for long term in space travel using nuclear, or SEP propulsion, refueled and reloaded with cargo or people for trips from earth orbit or LL2 to trips to Mars orbit and back. Refuel at Mars for earth return.  Starships may become the ferries (space trucks) from Earth to the ship and from Mars to the ship.  In space only very large ship would become the container cargo ship or cruise ship.   

Offline Robotbeat

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Re: Powerful Krypton Ion Engine...Mars SEP...
« Reply #7 on: 04/08/2021 02:13 pm »
VASIMR isn’t any better than a lot of other electric thrusters. You can use oxygen, but oxygen is super reactive so using CO2 or nitrogen or water would likely be better, but Argon is available on both Mars and Earth and is super cheap, so I dunno why you wouldn’t just use that.

Water makes sense if you wanna do asteroid mining, though. Momentus is already doing it with SpaceX.
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Offline rakaydos

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Re: Powerful Krypton Ion Engine...Mars SEP...
« Reply #8 on: 04/08/2021 02:20 pm »
I am skeptical of long term, post-space-industrialization use of ion propulsion. Basically, the exaust velocity is TOO high, and the propellant will usually be lost in solar orbit, "forever" (and if it's greater than SOLAR escape velocity, it's lost for ACTUALLY forever).

This, to my mind, makes it the "fossil fuel" of the solar system- amazing and powerful, but relying on what is ultimately a limited resource. Yes, the earth and martian atmospheres are thick with the stuff, and that's not even counting other sources, but exponential growth of space industry is going to be a helova drug.

Offline Robotbeat

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Re: Powerful Krypton Ion Engine...Mars SEP...
« Reply #9 on: 04/08/2021 02:48 pm »
I am skeptical of long term, post-space-industrialization use of ion propulsion. Basically, the exaust velocity is TOO high, and the propellant will usually be lost in solar orbit, "forever" (and if it's greater than SOLAR escape velocity, it's lost for ACTUALLY forever).

This, to my mind, makes it the "fossil fuel" of the solar system- amazing and powerful, but relying on what is ultimately a limited resource. Yes, the earth and martian atmospheres are thick with the stuff, and that's not even counting other sources, but exponential growth of space industry is going to be a helova drug.
The Sun is continuously shedding mass in the form of solar wind. But it’s not gonna run out and will, in fact, go super giant.

So at some scale, you just have to accept that. And using sunlight is actually an inefficient use of energy from the Sun even if you’re worried about propellant availability over millions of years. Jupiter and Saturn and Uranus and Neptune have plenty of propellant, as does the Oort Cloud. We won’t be running out.

Eventually you’ll have really high Isp solar electric propulsion. Solar cells extremely thin and lightweight, with Isp of like 100,000s, comparable to the solar wind. Propellant will last as long as the sun will last.
« Last Edit: 04/08/2021 02:52 pm by Robotbeat »
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Offline Nomadd

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Re: Powerful Krypton Ion Engine...Mars SEP...
« Reply #10 on: 04/08/2021 02:53 pm »
 It would be interesting to figure out how much extra power it would take to harvest a ton of Krypton at your LOX plant once you've already gone as far as separating the major components.
 But, once Tesla starts offering Starships in their lineup, it's hard to imagine ion being any cheaper than just adding more methane rocket to the mix for relatively short, inner system runs.
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Offline Robotbeat

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Re: Powerful Krypton Ion Engine...Mars SEP...
« Reply #11 on: 04/08/2021 03:02 pm »
It would be interesting to figure out how much extra power it would take to harvest a ton of Krypton at your LOX plant once you've already gone as far as separating the major components.
 But, once Tesla starts offering Starships in their lineup, it's hard to imagine ion being any cheaper than just adding more methane rocket to the mix for relatively short, inner system runs.
As Musk himself said, the nitrogen/oxygen plant will also be producing Argon. I think that’s primarily gonna be used for welding, but it’s an acceptable alternative to Xenon or Krypton. And they can produce it in-situ in Texas (or Mars).

Could also see SpaceX doing Neon, just one step down from Krypton and probably about 10 times as plentiful and 10x cheaper.
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Offline daveglo

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Re: Powerful Krypton Ion Engine...Mars SEP...
« Reply #12 on: 04/08/2021 03:13 pm »
Solar-powered electric might be fine using today's technology, but wouldn't nuclear-electric ion thrust be a better choice in the long run?  Certainly if we start talking beyond Mars.

Offline Robotbeat

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Re: Powerful Krypton Ion Engine...Mars SEP...
« Reply #13 on: 04/08/2021 03:16 pm »
Solar-powered electric might be fine using today's technology, but wouldn't nuclear-electric ion thrust be a better choice in the long run?  Certainly if we start talking beyond Mars.
depends entirely on the cost and the specific power.

Solar is beamed energy. All you need is a micron-thick energy conversion device. It’s not obvious that nuclear wins on both cost and weight until you get out to, like, the Kuiper Belt.
« Last Edit: 04/08/2021 03:17 pm by Robotbeat »
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Offline Vultur

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Re: Powerful Krypton Ion Engine...Mars SEP...
« Reply #14 on: 04/08/2021 04:16 pm »
Solar-powered electric might be fine using today's technology, but wouldn't nuclear-electric ion thrust be a better choice in the long run?  Certainly if we start talking beyond Mars.
depends entirely on the cost and the specific power.

Solar is beamed energy. All you need is a micron-thick energy conversion device. It’s not obvious that nuclear wins on both cost and weight until you get out to, like, the Kuiper Belt.

Yes, and solar technology is being actively developed by many companies, while nuclear technology advances slowly because of governmental/regulatory limits.

And in space the one disadvantage of solar on Earth goes away, since there's no clouds and no night, as long  as you stay out of the shadow of planets. (And I wouldn't be surprised if solar wins out in the long run on Earth anyway, as batteries improve -- even if we do get fusion.)

I don't know where the outer limit of solar's practicality will be, but Dawn's demonstrated SEP in the asteroid belt (low thrust, sure, but it can be scaled up - and I think with thin films you can do quite a bit better on power/weight of solar arrays). So I can't see nuclear-electric making sense anywhere sunward of Jupiter.

Offline ncb1397

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Re: Powerful Krypton Ion Engine...Mars SEP...
« Reply #15 on: 04/08/2021 08:58 pm »
I am skeptical of long term, post-space-industrialization use of ion propulsion. Basically, the exaust velocity is TOO high, and the propellant will usually be lost in solar orbit, "forever" (and if it's greater than SOLAR escape velocity, it's lost for ACTUALLY forever).

This, to my mind, makes it the "fossil fuel" of the solar system- amazing and powerful, but relying on what is ultimately a limited resource. Yes, the earth and martian atmospheres are thick with the stuff, and that's not even counting other sources, but exponential growth of space industry is going to be a helova drug.

1.3% of earth's atmosphere is Argon. Which translates to on the order of 72 trillion tons. You could use a 100,000 tons a year for the next 720 million years. If you want it to last until the sun becomes a red giant and destroys the earth anyway, you would have to limit yourself to 14,400 t per year (which can be done by increasing specific impulse). When you run out of that, you could use Neon which is more abundant in Jupiter's atmosphere than Argon. Long story short, I wouldn't worry about running out of ionizable matter anytime soon. And if you do run out, that just means the free wheeling days of cheap trips around the solar system are over after 100s of millions of years and "humanity" (and I mean that term loosely) is restrained to more isolated communities.

Using Mars' drinking and carbon supply to refuel ships is probably a bigger immediate concern.

Even Xenon, there is 2 billion tons in the atmosphere, if each refueling requires 200 t, you could refuel 10 million vehicles.
« Last Edit: 04/08/2021 09:17 pm by ncb1397 »

Offline rakaydos

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Re: Powerful Krypton Ion Engine...Mars SEP...
« Reply #16 on: 04/09/2021 12:47 pm »
I am skeptical of long term, post-space-industrialization use of ion propulsion. Basically, the exaust velocity is TOO high, and the propellant will usually be lost in solar orbit, "forever" (and if it's greater than SOLAR escape velocity, it's lost for ACTUALLY forever).

This, to my mind, makes it the "fossil fuel" of the solar system- amazing and powerful, but relying on what is ultimately a limited resource. Yes, the earth and martian atmospheres are thick with the stuff, and that's not even counting other sources, but exponential growth of space industry is going to be a helova drug.

1.3% of earth's atmosphere is Argon. Which translates to on the order of 72 trillion tons. You could use a 100,000 tons a year for the next 720 million years. If you want it to last until the sun becomes a red giant and destroys the earth anyway, you would have to limit yourself to 14,400 t per year (which can be done by increasing specific impulse). When you run out of that, you could use Neon which is more abundant in Jupiter's atmosphere than Argon. Long story short, I wouldn't worry about running out of ionizable matter anytime soon. And if you do run out, that just means the free wheeling days of cheap trips around the solar system are over after 100s of millions of years and "humanity" (and I mean that term loosely) is restrained to more isolated communities.

Using Mars' drinking and carbon supply to refuel ships is probably a bigger immediate concern.

Even Xenon, there is 2 billion tons in the atmosphere, if each refueling requires 200 t, you could refuel 10 million vehicles.
Actually, it isnt, which is my point-  chemical rockets are weak enough that the exaust gasses during departure fall suborbitally, (because departure velocity minus exaust velocity is less than (+/-)orbital velocity) returning to the host planet and burnt CO2 and H2O.

You see a boundless supply of argon, I see argon-powerd spacecraft getting mass produced to fulfil the supply. We're all a bunch of paperclip maximisers.

Offline ncb1397

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Re: Powerful Krypton Ion Engine...Mars SEP...
« Reply #17 on: 04/09/2021 01:40 pm »
I am skeptical of long term, post-space-industrialization use of ion propulsion. Basically, the exaust velocity is TOO high, and the propellant will usually be lost in solar orbit, "forever" (and if it's greater than SOLAR escape velocity, it's lost for ACTUALLY forever).

This, to my mind, makes it the "fossil fuel" of the solar system- amazing and powerful, but relying on what is ultimately a limited resource. Yes, the earth and martian atmospheres are thick with the stuff, and that's not even counting other sources, but exponential growth of space industry is going to be a helova drug.

1.3% of earth's atmosphere is Argon. Which translates to on the order of 72 trillion tons. You could use a 100,000 tons a year for the next 720 million years. If you want it to last until the sun becomes a red giant and destroys the earth anyway, you would have to limit yourself to 14,400 t per year (which can be done by increasing specific impulse). When you run out of that, you could use Neon which is more abundant in Jupiter's atmosphere than Argon. Long story short, I wouldn't worry about running out of ionizable matter anytime soon. And if you do run out, that just means the free wheeling days of cheap trips around the solar system are over after 100s of millions of years and "humanity" (and I mean that term loosely) is restrained to more isolated communities.

Using Mars' drinking and carbon supply to refuel ships is probably a bigger immediate concern.

Even Xenon, there is 2 billion tons in the atmosphere, if each refueling requires 200 t, you could refuel 10 million vehicles.
Actually, it isnt, which is my point-  chemical rockets are weak enough that the exaust gasses during departure fall suborbitally, (because departure velocity minus exaust velocity is less than (+/-)orbital velocity) returning to the host planet and burnt CO2 and H2O.

You see a boundless supply of argon, I see argon-powerd spacecraft getting mass produced to fulfil the supply. We're all a bunch of paperclip maximisers.

You may not have fully considered how digging up buried ice and releasing it into the atmosphere over 100s of millions of years will affect the planet. Mars' atmosphere is naturally lost to space. You take the water and release it into the atmosphere or in space in the region of mars, you will increase its exposure to radiation from space that naturally strips it away. The one saving grace is that, at least for current large spacecraft design proposals, the landing burn (assuming propulsive landing) requires more fuel at mars than it does at earth. This will be a net import of water, hopefully that balances things out. The reverse would be the case for many other routes. For instance, a trip from mars to a moon of Jupiter would have the opposite effect (the propulsive maneuvers in the jupiter system would be larger and more fuel intensive than the propulsive maneuvers in the vicinity of Mars). This would necessarily be a net exporter of water from mars to the Jovian system or beyond.



At least with electric propulsion, you have greater options in what you want to do as isp is a parameter you can vary by need. For instance, instead of refueling at 2 different bodies in order to establish a round trip trade route, maybe you only need to refuel at one. This would potentially allow for imports from the Jovian system to Mars of needed materials that would otherwise use more resources than it delivers (for instance, Starship uses ~1000 t+ of propellant but delivers on the order of 100 t + of supplies per landing). 
« Last Edit: 04/09/2021 01:41 pm by ncb1397 »

Offline spacenut

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Re: Powerful Krypton Ion Engine...Mars SEP...
« Reply #18 on: 04/09/2021 01:54 pm »
On Mars I don't think they will release any water to the atmosphere.  It will be filtered for potable water, separated to make methane and lox as well as breathable oxygen.  Nothing wasted or released, except during liftoffs of Starships to space.

Now if you make a very large cargo ship in space using argon ion propulsion to go from Mars orbit to Earth orbit, the used Starships on left on Mars to bring up Argon to refuel at Mars as well as some return cargo such as rocks and soil for research back on earth.  You only use most of the Starships on earth to reload this cargo ship and refuel it with argon for return trip to Mars.  This would basically eliminate in space refueling of Starships except for quick human flights to and from Mars. 

The large ion ship would slow gradually into a lower earth orbit to be able to dock with cargo Starships loaded with Mars supplies and argon for return to Mars.  Same with Mars gradually lower itself into a low Mars orbit so Starships launching argon and return items can easily reach the large ship without excessive fuel needs so it can re-land back on Mars. 

Starships then become large trucks. 

Even a vary large SEP cargo ship could carry passengers for a crew with a centrifuge on board for daily gravity use. 

At some point refueling Starships 6 times just for one trip to Mars may get too expensive.  6 cargo flights to dock with a large SEP cargo ship could get the cargo at least 5 flights of cargo and one to fill up of Argon to get a tug ship on its way.   It may only take one cargo Starship of argon to be able to take 1000 tons of cargo, not just 500 tons to Mars. 

Something to think about. 

Offline rakaydos

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Re: Powerful Krypton Ion Engine...Mars SEP...
« Reply #19 on: 04/09/2021 02:00 pm »
On Mars I don't think they will release any water to the atmosphere.
You apparently missed my complaint, that Ncb was responding to- that a rocket engine fired in orbit (with an exaust velocity less that twice orbital velocity) "recycles" it's propellant back to the planetary atmosphere in  the form of exaust gasses, but that a constant thrust ion engine, if it cant point it's drive directly at a planet the whole trip, can eject propellant into interplanetary space, lost forever.

Ncb's point of atmospheric erosion is taken, but there are measures that can be taken to compensate, such as a superconductor ring around the equator for an artificial magnetic field.

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