Water Thrusters Steam vs Ionize and accelerate ions

tahanson43206 · 2025-02-08 17:42:25

The article at the link below reports on research on the possibility of making throw mass for ion accelerators, by ionizing water.

https://interestingengineering.com/spac … d-by-water

The ISP is likely to be greater than what might be achieved by simply heating water to make steam.

On the other hand, the amount of thrust will be less.

This idea appears attractive for satellite station keeping.

Thanks to feedback from SpaceNut and Void, and for advice from kbd512 I'm encouraged to this this topic might be able to deliver useful information.

In mid-February 2025, the mission of this topic is adjusted to foster competition between two ways of using water to accelerate a spacecraft.

The first method is simple steam. Steam has been recognized as a way to accelerate a mass for thousands of years.

The second method is of more recent origin. At some point in the past 300 years, humans learned how to separate hydrogen from oxygen in the water molecule, and how to accelerate those two atoms separately.

My concept is for this topic to become a souce of knowledge and perhaps even understanding.

The most reasonable way to approach this is to invite NewMars members to join either the Steam team or the Ion team.

(th)

tahanson43206 · 2025-02-08 17:47:04

This post is reserved for an index to posts that may be contributed by NewMars members over time.

Status of competition between Steam Team and Ion Team:

Steam Team:
To be reported when available.

Ion Team:
To be reported when available.

(th)

tahanson43206 · 2025-02-09 09:09:25

This topic provides an opportunity for a member to compute the comparison of the technology of the topic vs heating water molecules to a high temperature and allowing them to escape the heating chamber.

The mass for comparison will be one kilogram, and the amount of energy to invest would be the same.

A sample energy input might be given in watt hours, or joules or electron volts.

Whatever energy is chosen would be applied equally in the comparison.

The comparison would be between simple thermal acceleration of water molecules, and the concept of the topic.

The concept of the topic would be to split the water molecule and to accelerate the ions separately.

Since the same amount of energy is to be invested in both cases, some of the needed energy will be required to split the molecule.

The question that our (hypothetical) member will answer is:

Given the same mass and energy as inputs, and water as the "propellant", which method produces the better results?

For comparison purposes, let the mass of the system to be accelerated be 1 metric ton.

At this point, I don't think anyone has a way of making a prediction without math, but this forum often surprises.

(th)

SpaceNut · 2025-02-10 08:25:18

Power and heat are the methods to accelerate the water.

Void · 2025-02-10 10:39:21

Logic and Comparisons can have some aspects of Math. Other members might be able to directly do math to make an evaluation.

We know a little bit about nuclear power in space. Most nuclear thermal ideas revolve around Hydrogen, which could be 2 to 3 times as good as chemical propulsions (If I recall correctly the claims I have encountered).

I recall Dr. Johnson indicating that nuclear thermal with water working with water from the Moons of Jupiter.
What I have also read about that is nuclear thermal with water is about equivalent in results as the best chemical propulsion methods. So approximately 1 to 1. But that is steam, I expect, maybe I am wrong?

If you can go to plasma, then your results could be greater. This begins to look a bit like electric rockets, except I expect that this might be easier expand in size, provided you had the power for it.

Solar electric power could be considered, but I think that nuclear electric would be better in general, if you could get some. The thing about that over chemical is that you could push a load to Mars orbit, and still have a nuclear generator to process materials from Phobos and Deimos. I am not going to count on those moons to have large amounts of Hydrogen, but they will have Oxygen, so if your propellant is water, you might get Hydrogen from Mars, and process ores from Phobos and Deimos and get water. So to refill/refuel a ship in Mars orbit you would only need to lift about 11%? of the mass to Mars orbit. And as a side effect you might also get processed materials from the "Ores" of Phobos and Deimos.

I have often wanted to look into a mass driver that would expel Oxygen which is after all a waste product that we breath. If water to plasma works then perhaps this is a way to use the waste Oxygen for propulsion.

Hydrogen is hard to handle, but if you only produce it on the surface of Mars, and then lift it to orbit and then quickly combine it with Oxygen from Phobos and Deimos, after that both Hydrogen and Oxygen are easy to handle.

So in this case you would not be lifting the Oxygen and Carbon from the Mars surface to run raptor engines to get you from Martian orbit to Earth/Moon.

Also, since you would be nuclear-electric, you would not necessarily need heat shields to get into orbit of Earth/Moon.

Also, if you have water as your propellant, and an electric power source, you may make Oxygen to breath, if you need to.

If you bring Hydrogen to LEO, you might react it with Lunar Oxides. Then using water propellants you might bring Methane to Lunar orbit. Here again you may react the Methane with Lunar Oxides, and produce water and CO2. The water can become propellants in orbit, and also could give you Hydrogen and Oxygen. The CO2 can be reprocessed into Carbon or CO to react with Lunar Oxides, over and over again. You might only land Methane onto the Moon to allow raptors to lift Lunar Oxides to orbit.

Or the Moon may have lots of water and you could do it that way.

A water to plasma thruster method could be very useful, I think.

Ending Pending

Last edited by Void (2025-02-10 11:01:06)

tahanson43206 · 2025-02-10 12:00:29

Thanks to SpaceNut and Void for providing encouragement for this new topic.

Thanks to kbd512 for providing a link to information about use of a great variety of materials for ion acceleration.

I would like to (at least attempt to) guide this topic toward building up actual knowledge and useful information that would be of value to a reader.

We can imagine a reader who is thinking about building a thrust system for deep space travel.

The funder is willing to pay for systems that use water as the propellant, and our hypothetical engineer has the choice of using traditional steam fed by energy in the thermal regime, or of splitting the water and accelerating the hydrogen and oxygen ions separately.

To make this more interesting, I am proposing simple conditions for the evaluations:

1) Mass of water for use as propellant: 1 Kg
2) Mass of space vessel to be accelerated: 1 Metric ton

The amount of energy to be used is an option for the teams, but the amount must be the same for both methods.

To help start things out, I'd like to encourage the Steam team to calculate the amount of energy they would need to produce the best possible result.

An infinite amount of energy would produce an infinite acceleration, so the amount of energy chosen needs to be useful/practical in the Real Universe.

Once the Steam team has determined the maximum amount of energy that can be invested in accelerating a Real Universe space vessel, then that amount of energy can be applied by the Ion team to see what they can come up with.

The terms of this competition can be adjusted as participants provide feedback.

(th)

tahanson43206 · 2025-02-10 12:57:11

https://space.stackexchange.com/ contains discussion of the use of water as a propellant...

Among the points made is that the Steam Team has an additional option not mentioned earlier in this topic.

The Steam Team can electrolyze the water and use the products in an ordinary chemical rocket engine.

The result of combustion is steam (of course)

(th)

tahanson43206 · 2025-02-10 14:11:47

I've invited to GW Johnson to serve as a judge for the competition between the Steam and the Ion teams.

He has not yet confirmed if he is willing to take on that role. He ** did ** provide two sets of advice for team members.

Section 1 of 2:

I know very little about electric propulsion, except that the "chamber pressure" where the particles are accelerated is essentially vacuum, so that the density of the matter within the accelerating device is extremely low. That is why you only get milli-Newtons of thrust from devices massing several to many kilograms, not including the power supplies. It may be fundamental physics imposing that rather severe thrust per unit power limitation, I honestly don't know.
If the source material for these particles is not a gas, then it has to be vaporized. That requires an energy input, which is actually quite large in the case of ice or liquid water. Could also be quite large with many metals. Maybe not so much with things like iodine. Which might be part of why someone has tried it, along with the solid storage advantages.
An odd thought occurs: why not store the iodine in the form of nitrogen tri-iodide? It's a sensitive monopropellant but a very-mild explosive. Use that energy to vaporize and dissociate the material into iodine and nitrogen atoms. Then accelerate those electrically. This is the prank stuff you smear on toilet seats. When the victim sits, it explodes without hurting anybody, but the iodine stains a big purple circle onto the victim's butt. We made and used this stuff in high school chemistry. Although for me that was almost 60 years ago now. I no longer remember how to make it.
If the source material is not monatomic, then most of the chemistry I ever saw says it will dissociate into radicals, before you can ever actually ionize it in the sense of stripping-fully-loose any electrons. There is a dissociation energy input associated with that. Most of the stuff in high school chemistry dissociated only with lots of heat from a Bunsen burner flame, so that's another relatively-high energy input requirement.
And then there's the actual ionization energy requirement, to fully strip loose those electrons. Some are higher than others in the list we saw last night, but I honestly do not know how those energies compare to the energy requirements for dissociation and vaporization. However, since the most common electric thrusters use monatomic gas sources that have no vaporization or dissociation energies, I suspect those other energies might be every bit as "significant" as the ionization energies.
And then there's the applied electricity energy to accelerate those particles to high speeds out of the thruster. It's a momentum thing, you can get higher speeds out of lighter particles for a given electric power output, but whether high speed/lightweight, or lower speed/heavyweight, it's still the same momentum (and therefore the same thrust) for a given power input. So the atomic weight of the individual particles may not matter so very much.
It would be very interesting indeed to see a list of candidate materials with all those energies included and then summed, not just the ionization energies. But scientists don't think that way when they publish, only engineers do. I cannot do that, I don't have the right background of experiences to sort out what we need, to compile such a list. The person who does that really needs to know what he is doing. That would be some engineer at one of the electric thruster manufacturers.
As for the chemical-physical damage the particles do to the accelerator device hardware, you just carry spare parts and simply replace the worn-out ones. On a larger vehicle, you can do that while underway, manned or robotically. You must design your thruster to help make that process easy. Smallish satellites would need an on-site repair visit by some sort of tug analog to roadside tow truck assistance.
But what do I really know? Very little, actually.

Section 2 of 2

If you get steam hot enough, it dissociates, but not as free atoms. The dissociation final product is molecular hydrogen and molecular oxygen (I don't know all the detail steps, just the result). Get it hotter, and those begin to dissipate into monatomic hydrogen and monatomic oxygen, I dunno which is first. You have to get it yet hotter still to start stripping electrons loose.
I'm not sanguine about electric propulsion, but for thermal (heat engine) rockets, the ionization energies and dissociation energies are not convertible by the nozzle into exhaust momentum.
The expansion nozzle converts high P and T at essentially no V, into low P and T with high V, but only the internal energy is so converted! It does this in a way that conserves total enthalpy (which is internal energy plus a pressure term). This model presumes no changes in molecular identity, just changes in P, T, V, and stored heat content, all in accord with the ideal gas law.
Those are the underlying mathematics of compressible flow. Those underlying assumptions get violated in hypersonic flight above about Mach 7 or at most about Mach 8, here on Earth. It actually starts breaking down at around Mach 6. There is no "sharp boundary", just increasing dissociation and ionization effects throwing off the results from the compressible flow model predictions. You achieve less performance than you would predict.

(th)

tahanson43206 · 2025-02-11 08:17:17

The post #8 with quotes from GW Johnson contains hints of what might become a "universal" deep space propulsion system.

In the weekly Google Meeing, kbd512 showed us a table of energies of ionization of a large number of elements.

This topic was created to study the use of water as a propellant, but the work on water might fit into a larger concept of using whatever material is present in a location in the Solar System as source material for an ion drive.

I'll check to see if one of the existing topics might be adapted for a "Universal Ion Drive" concept.

Meanwhile ** this ** topic is available for accumulation of knowledge/insights/tips about use of water as a source material for propulsion.

It seems to me that a deep space exploration or mining vessel or probe that focuses on using water as a propellant source would have wide application. Water can be split and the elements accumulated until there is enough mass for a significant chemical burn to produce massive thrust for a brief period.

Water can also be split and used as propellant mass for an ion engine.

As long as solar energy is available such a vessel/probe could go anywhere water is available.

(th)

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#1 2025-02-08 17:42:25

Water Thrusters Steam vs Ionize and accelerate ions

#2 2025-02-08 17:47:04

Re: Water Thrusters Steam vs Ionize and accelerate ions

#3 2025-02-09 09:09:25

Re: Water Thrusters Steam vs Ionize and accelerate ions

#4 2025-02-10 08:25:18

Re: Water Thrusters Steam vs Ionize and accelerate ions

#5 2025-02-10 10:39:21

Re: Water Thrusters Steam vs Ionize and accelerate ions

#6 2025-02-10 12:00:29

Re: Water Thrusters Steam vs Ionize and accelerate ions

#7 2025-02-10 12:57:11

Re: Water Thrusters Steam vs Ionize and accelerate ions

#8 2025-02-10 14:11:47

Re: Water Thrusters Steam vs Ionize and accelerate ions

#9 2025-02-11 08:17:17

Re: Water Thrusters Steam vs Ionize and accelerate ions

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