Lunar economics etc

louis · 2019-05-22 04:31:19

Hi GW,

Sorry to hear you've been in hospital. Hope you are feeling much better.

Regarding knowledge of the surface, my understanding is that by various other methods (in addition to photography), including radar and spectrometers, NASA and ESA have been (through their orbiting satellites) acquiring pretty detailed knowledge of the surface. For instance, I think they can ascertain if a rock platform is many metres thick or not.

It's true that no one can be 100% sure until a landing takes place but the beauty of Space X's mission architecture is you send cargo craft first before humans arrive in the area.

Obviously I don't have specific technical knowledge... I am just going on what I have read about landing site selection in particular via this very helpful link:

https://www.nasa.gov/feature/mars-human … entations/

I was surprised at just how detailed the knowledge of potential landing sites is. I presume they are looking for a granite-style rock platform that isn't going to sink at all under the weight of a 1000 ton fuelled rocket.

So I think the takeaway points are:

- There are rock platforms that could serve as landing areas.

- We can be assured they aren't going to crumble on impact.

- We can be assured what the gradient is and so select a less than 5% gradient site in line with NASA requirements.

- We can send cargo craft first to Mars and thereby test the actual landing site conditions to a very high degree of confidence.

My view is that the propellant production and a possible need for rocket refurbishment (the latter rarely gets addressed) is far more challenging than the landing or take-off on Mars.

I get the impression that the lunar surface is more challenging for landing and take off than for Mars. So not sure how that plays out.

GW Johnson wrote:

In one of the other threads, Louis was talking about 6 cm resolution capability, which I presume is photography from one of the orbiting probes at Mars. He was trying to make a case that this "proves" there are safe places to land a Spacex Starship, with its current landing pad design sizing.
That's a very impressive photographic resolution, but photography is of the surface, and says absolutely nothing about what's beneath. Given the current state of humanity's technologies, the ONLY way to find out what's beneath the Martian surface is real ground truth. You have to go there and dig or drill.
His other point was based on some kind of definitional argument. Something about landforms being classified as "exposed rock platforms". Trouble with that is, anything definitional is just a best guess based on surface appearances. Ground truth trumps all. Best to be prepared to land in soft sand, which a lot of Mars seems to be. Then you can land anywhere, and not be restricted by local soil types.
For the Spacex Starship design, touchdown is less of a problem than re-launch after refilling. The refilled weight, even on Mars, is about 6 times the touchdown weight. You don't want it sinking into the dirt (and tipping over), while you refill it with propellants.
I've got those numbers posted over at "exrocketman" some time ago, along with a listing of various Earthly soil strengths I got out of an older edition Marks' Mechanical Engineer's Handbook. Doesn't matter that it's an old reference. Those numbers haven't changed in over a century.
GW

Last edited by louis (2019-05-22 06:25:05)

GW Johnson · 2019-05-22 10:07:04

I forgot about ground-penetrating radar. The resolution is far poorer, because resolution is inherently related to wavelength, but it ought to be capable of distinguishing a "thin" layer of rock from a "thick" layer of rock. May not be able to tell busted boulders laying together from solid rock, though. Quite a difference in strength there, at the larger weight-to-be-supported scale. I'm no electromagnetics expert, so I dunno, myself. Just what I read.

Hospital stay was for something resembling a mini-stroke, but imaging showed no damage, so it's not classified as such. I got classified in the grab bag bin: they don't know what it was, how it worked, or what causes it. It seems to be rare, though, and the recurrence rate is low, too. There's just 2 hours missing from my life, and I'm told I was awake and talking, and absorbing no new info, that whole 2-hour time. Been normal ever since I came out of that 2-hour gap.

Got home from the hospital Monday evening, and Tuesday went back to ER with something I never had before. I got stung by a wasp, and had the potentially-fatal reaction to it. Still recovering from that today, but I'm gonna be OK. Must carry the Benadryl-etc "kit" from now on, though.

GW

Last edited by GW Johnson (2019-05-22 10:09:54)

Void · 2019-05-22 11:23:00

GW, very happy for your recovery. Also I will express thanks for the work you do to keep us honest about what can and cannot work.

Earth and Moon from a "synestia":
https://www.space.com/39841-moon-formed … heory.html
Moon from magma ocean splash:
https://arstechnica.com/science/2019/04 … gma-ocean/
Earth's water from outer solar system:
https://phys.org/news/2019-05-formation … earth.html
Notion of how water forms on the Moon. First, solar wind embeds Hydrogen, then impactors impart enough energy, to cook up water from the Hydrogen, and Oxides in the regolith:
https://phys.org/news/2019-05-formation-moon.html

I think the information may be interesting to the members. It also suggests that going to the Moon to get more "Ground Facts" is justified even for space haters, as if we know more about the Moon, we may well then understand our home planet better, and that is a thing of value.

The last link suggests that the Moon may have a relatively constant flow of water formation, in most or all of the regolith. First Hydroxyl being formed and bonded to minerals as I understand it, and then actual water being formed and going into the Lunar atmosphere. Then some of that water, we now think gets captured to some of the polar shadowed craters.

So, up to a point, it may be a renewed resource for our utilization. We don't yet know how much we can take to conserve it for our long term needs.

So going to the Moon is quite justified in my opinion.

I will otherwise leave you and the other members alone on this topic.

Done.

Oh, I lied. I also wonder about solar wind impacting the atmospheres of Venus and Mars, and perhaps creating water. We typically assume that the water of Venus and Mars was all put there early on, and that the loss of Hydrogen, left a heavy Hydrogen concentration. But I am not completely sure about that. There may be a water cycle where Sun Hydrogen>Atmosphere>Hydrogen off to space. That also being able to concentrate heavy Hydrogen.

But not proven, not even properly examined yet.

Now I promise, I am done.

Last edited by Void (2019-05-22 11:34:36)

SpaceNut · 2019-06-04 21:55:04

We should probably know the answers to these Five ethical questions for how we choose to use the Moon

Void · 2020-04-22 17:50:20

Well I found a thread for the Moon. Glad, I did not want to start a new one.

Today I am thinking about steam rockets, and their cousins.

https://truestrangenews.com/perpetual-s … en-probes/

I am taking a break lack of sleep last night. A break will help.

So, it would be possible to launch from the Moon with steam. Not sure that is better than using Hydrogen/Oxygen combustion.

And I am not sure I like high pressure steam boilers. So, I will try to bring something else on board.

I hope I don't offend the U.K. people with this next, but it supports what I am thinking of.
https://en.wikipedia.org/wiki/Falklands … _Sheffield
What was burning, I believe was Aluminum. Get it hot enough, and even if you spray water on it, it burns.

So, I think that if a process on the Moon could extract Aluminum and Oxygen, and of course then you have your water from the poles, you may have some interesting options for several mix and match propulsion systems. I am saying that they are a sure thing, just interesting. As you know I want to have methods to deliver Aluminum to Mars, so that the Martians can focus on other processes at first that are easier to accomplish.

This is an interesting article about a cousin of the Steam rocket:
https://en.wikipedia.org/wiki/ALICE_%28propellant%29
It somewhat supports what I am after, but also their is one problem that I have detected from the article. I say it is worth a read though.
Here is the problem: The oxide layer in nano-aluminium powder, however, is thinner and easier to overcome than in that of larger particles.

I will proceed with this anyway, but another break now.

This is not going to well after all. I was thinking first of a solid aluminum portion into which you squirted hot steam. I suppose if you could make it so that it is sintered nanoparticles, maybe. I was thinking then of preheating the Aluminum portion close to the melting point. Its a big maybe. I wanted to heat a fuel, Aluminum, and an Oxydizer, Steam. In that way you have stored heat and then a chemical reaction to power your rocket, but it is looking pretty tough.

Actually it might be possible to 3D print connected Nano particles of Aluminum. Maybe.

Then I was thinking why not melt the aluminum and squirt it into the process like a liquid fuel. Maybe at high temperatures of melting you could. Aluminum apparently boils at 2470 degC / 4478 degF. But we could not likely have a containment for that that would not melt.

So, you try, and then squirt pressurized liquid aluminum into a rocket motor. I have my concerns that it would not work, so, I will try to add something else on.

So, I want to atomize or vaporize the aluminum stream going into the engine. I wish it could be done with something like a paint spray. Perhaps if mixed with a bit of Hydrogen. (Not sure of that at all, might be a chemical reaction in the Aluminum before the combustion).

So, next I would try an electrical charge. Exactly how to achieve that is not yet settled. I am hoping that you could cause the liquid Aluminum to repulse itself into small particles. Not so sure.

So, next may an electrical arc. The hope would be that you might even boil the Aluminum, without melting the nozzle(s). Good luck, but maybe. I am pretty sure that Aluminum steam would burn in water steam, if you could do it.

But then you need a significant source of electrical power. I though batteries at first. Of course they would add weight. But then I thought steam turbine with a generator. After all the steam reservoir is part of the rocket. So maybe...maybe.

Last edited by Void (2020-04-22 18:48:17)

tahanson43206 · 2020-04-22 18:38:51

For Void re #182 ... Thanks for the link to the wikipedia article on the Falklands War .... I appreciated the opportunity to review the perspective offered by the author(s). It's been a while since I thought about that conflict. However, I missed your reference to something burning. Could you select a bit of text in the article and paste it as a quote?

Beyond that, however, thanks for the steam rocket asteroid mining concept. That ought to be of interest to Calliban, if he ever gets time to resume his development of the asteroid mining theme he started.

I like the inherent simplicity of the concept. The thrust would be low, but the sophistication of the system would be low, and that seems like a reasonable trade.

Here is a quote from your post that I hope you will develop further:

So, it would be possible to launch from the Moon with steam.

This assertion needs support from someone with the necessary background.

I suspect you will find that the ISP of steam is insufficient to overcome the lunar gravity.

You may find support for your assertion. I would be happy to see it. Otherwise, I will remain doubtful.

An engineer friend with deep knowledge (though not as deep as that of GW Johnson) has dissuaded me from considering steam as a propellant, except for special cases such as your asteroid mining example.

(th)

Last edited by tahanson43206 (2020-04-22 18:39:41)

Void · 2020-04-22 18:49:52

Quote:

Sinking of HMS Sheffield[edit]

HMS Sheffield
On 4 May, two days after the sinking of General Belgrano, the British lost the Type 42 destroyer HMS Sheffield to fire following an Exocet missile strike from the Argentine 2nd Naval Air Fighter/Attack Squadron.
Sheffield had been ordered forward with two other Type 42s to provide a long-range radar and medium-high altitude missile picket far from the British carriers. She was struck amidships, with devastating effect, ultimately killing 20 crew members and severely injuring 24 others. The ship was abandoned several hours later, gutted and deformed by the fires that continued to burn for six more days. She finally sank outside the Maritime Exclusion Zone on 10 May.
The incident is described in detail by Admiral Sandy Woodward in his book One Hundred Days, in Chapter One. Woodward was a former commanding officer of Sheffield.[90] The destruction of Sheffield (the first Royal Navy ship sunk in action since the Second World War) had a profound impact on the British public, bringing home the fact that the "Falklands Crisis", as the BBC News put it, was now an actual "shooting

As I recall, the Aluminum of the ship was burning, and they could not put it out with water, water only made it burn more.

…..

Again:
https://truestrangenews.com/perpetual-s … en-probes/
Quote:

“It’s awesome,” Metzger says of the demonstration. “WINE successfully mined the soil, made rocket propellant, and launched itself on a jet of steam extracted from the simulant. We could potentially use this technology to hop on the Moon, Ceres, Europa, Titan, Pluto, the poles of Mercury, asteroids—anywhere there is water and sufficiently low gravity.”

The Moon and Mercury are both mentioned as feasible.

And if you read my posts, you would see that I am trying to soup up the thrust with hot Aluminum combustion.

Have a good night.

Last edited by Void (2020-04-22 18:55:15)

tahanson43206 · 2020-04-22 20:04:19

For Void re #184

Thank you for explaining that you are drawing from another resource, in asserting that aluminum in the ship was a problem. It may well have been. I note that the US Navy has experimented with aluminum. The article you quoted did not include that detail.

Perhaps that is OK if a ship is completely automated.

Image result for are littoral ships made of aluminum
The afflicted vessel is USS Independence, the second in the sailing branch's fleet of fast, reconfigurable Littoral Combat Ships. Eventually, these ships are supposed to be the workhorses" of tomorrow's Navy. ... In contrast to the first LCS, the steel-hulled USS Freedom, *Independence *is made mostly of aluminum.Jun 23, 2011
Builder Blames Navy as Brand-New Warship Disintegrates ..

And thank you for confirming my engineer friend's prediction. Please note that the authors (Metzger, et al) are NOT asserting steam would be used to leave the Moon by achieving escape velocity. Instead, the text you quoted specifically mentions "hopping" from one location on a body to another. The method would certainly work well for objects with small gravitational attraction.

I am interested in the concept, so did a little exploring. The low ISP of 195 quoted below seems about right, as I try to recall my engineer friend's objections. However, it probably ** could ** be made to work on the Moon, for a launch to escape velocity, if the designer is sufficiently clever and if the supply of energy to heat the working fluid is abundant.

https://en.wikipedia.org/wiki/Steam_rocket

More complex designs can involve passing the water through pumps and heat exchangers and employing nuclear reactors or solar heating; it is estimated that these can give a specific impulse of over 195 s Isp,[2], which is still well below the standards of more complex designs, for example the 465 s of the hydrogen-oxygen Vinci engine.

Here is a discussion about using aluminum from the Lunar regolith to make a propellant ...

https://space.stackexchange.com/questio … ant-source

The ISP quoted for aluminum and liquid oxygen was about 200.

That was just a discussion in Stack Exchange, so better references may give a more authoritative figure.

One advantage of a launch from the Moon is the absence of atmosphere, so that even a low ISP such as 195-200 could achieve escape if the launch is started in a horizontal run like the electromagnetic launcher kbd512 was talking about a few weeks ago. The launch vehicle could run along a track for as long as it needs to build up sufficient velocity to lift every so slowly off the track. After that it could continue to spiral out away from the surface, so the steam propellant idea might be made to work.

Perhaps we will be lucky enough to have earned an authoritative answer by someone more knowledgeable.

(th)

Void · 2020-04-23 08:53:05

(th)

I think you are correct, for the steam launch only situation. I could make the point that if you took away the solar panels and the drilling equipment, the device could do better with launching from the Moon. But that would only make sense, if the craft without those accessories, and without a payload, would be considered valuable in itself, to use as source materials to build things.

And thank you. I have decided to continue however because you have triggered alterations in my thinking, and also this site is so quiet just now, I don't think I am interfering with the works of others.

---
Let me say first, that I think that before anything like I am suggesting would happen, first Moon activities would be supported by craft such as Blue Moon, or perhaps Starship.
---
So, I am from here talking about later on, perhaps much later on.

So, you prompted me to do a better look at what the Moon is made of (On average).
https://www.bing.com/search?q=What+is+t … 0e872d70b0
So, under "What is the Moon made of? (Hint not cheese), the pdf is of interest.

Quote from the PDF listed there:

Crust
Oxygen, Silicon, Magnesium, Aluminum, Iron, Calcium, Titanium, Thorium, Potassium, Hydrogen,
Uranium
43% Oxygen, 20% Silicon, 19% Magnesium, 10% Iron, 3% Calcium, 3% Aluminum, 0.12%
Manganese, 0.18% Titanium

Aluminum is a disappointing 3%, although I am inclined to think that there are locations where it will be more.
However, Magnesium is a more robust 19% it seems, and again there may be locations where it is more.

So, I would want to conserve that Iron, Aluminum, and I suppose other metals that are in small quantities for construction of whatever on the Moon, and other places as well.

The Magnesium, I would want to consider using for a propulsion device if possible. That is to replace the Aluminum I previously endorsed for that purpose.

Danger Will Robinson! This will be a bit silly, but useful information anyway.
https://www.thewrap.com/lost-in-space-w … -melt-ice/
Quote

In the show, Will and his dad, John (Toby Stephens), gather flakes of magnesium to burn and use a torch to light it. Magnesium is highly flammable in small flakes or strips and burns very hot. It’s possible for magnesium fires to hit 5,100 degrees Fahrenheit — definitely hot enough to help get Judy out of her ice jam.

So, one could have three different situations. 1) Heated Magnesium, heated to almost the melting point would probably burn when hot steam was passed through it. 2) Liquid Magnesium (already past one phase change energy wise), could be pumped into a steam stream, hopefully to ignite. 3) Magnesium Steam if you could do it, should burn well, you are already 2 phase changes up in energy.

https://en.wikipedia.org/wiki/Magnesium
Quote:

Physical properties
Melting point
923 K (650 °C, 1202 °F)
Boiling point
1363 K (1091 °C, 1994 °F)

So, when I looked for it I found that Stainless Steel Type 304 Melts between 1400-1450 C (I believe), so, it might be able to contain Magnesium steam. Hope so. I hope I have not messed that up. Pretty tired.

I won't bother to provide the reference, but my understanding now is that if you burn Magnesium with water, you will get a Magnesium Oxide and free Hydrogen output. That sounds very good, since you will have heavy molecules, the Magnesium Oxide being pushed out by Hydrogen which is much favored for its expansion qualities. Not certain, but it sounds good.

As long is the Magnesium Oxide does not build up on the thruster nozzle so to plug it.

So, if this works, then I currently see two prominent options.

1) Small ones launched by the mass driver method of KBD512. In that case it would be desired that these little robots could be mass produced, and when launched, would be able to travel to and be properly received at some reception point. They would then be repurposed as scrap metal.

2) A big space ship perhaps even able to carry cargo inside of it, or attached to it's outside.

The Moon I think is quite good for this as you have the long lunar days to prime these things with heat.

Last edited by Void (2020-04-24 17:24:38)

tahanson43206 · 2020-04-23 09:21:38

For Void .... Just FYI ... in the new Physics topic, I have reported finding a link to a 1997 study about using steam as the MOST economical/effective method for launching to escape velocity from the Moon. I thought that (if you have time to glance at it) you might be amused to see how my skepticism has been answered.

It turns out (as well as I can understand the paper) that while hot steam is destructive of materials, the lower temperature chosen allows for robust propulsion and a sufficient ISP to allow the launch system to compete effectively against a comparable system using water split by electrolysis.

It seems (to me at least) a shame to throw away (literally) perfectly good Magnesium for propulsion. Aren't there more valuable uses for the material?

I know Magnesium is listed as a needed trace element for human health.

This topic is about Lunar Economics .... What is the most economically valuable use for magnesium?

(th)

Void · 2020-04-23 09:49:56

Well on average the Moons surface is 10% Magnesium. I think there is plenty for all purposes.

Also, on a note, I am imagining that build of these machines would be highly automated, and greatly controlled by people monitoring the situation on the Moon from Earth. Although there would be people on the Moon as well.

Pretty far in the future, but an interesting dream anyway, I think.

Void · 2020-04-24 17:22:42

Correction Magnesium = 19% of Moon, from what I read.

Also:

Melting point
923 K (650 °C, 1202 °F)
Boiling point
1363 K (1091 °C, 1994 °F)

So, when I looked for it I found that Stainless Steel Type 304 Melts between 1400-1450 C (I believe), so, it might be able to contain Magnesium steam. Hope so. I hope I have not messed that up.

So, now I am thinking liquid Magnesium, so that you don't have to deal with a strongly pressurized fuel tank. So a lower fuel tank would be inside of a retractable oven, and you would heat the Magnesium up to melt and then pump it in. Then you could put your Oxidizer into an upper tank. I am thinking of other Oxidizers now. Steam is also a hassle, as you have to have a strong pressure vessel.

Two alternatives to avoid that.

A mix of water and Hydrogen Peroxide not strongly heated.
In that case it is still a bit of a steam rocket, in the sense that a sauna can have steam if you throw water on hot rocks. And because it has some Hydrogen in the Water and the H.P., the output might be benefited by their extreme activity with heat.

Of course the other one could be LOX. No Hydrogen unless you choose to add it.

The engine(s) would have to deal with a thermally hot fuel, and a much cooler or cold Oxidizer.

Last edited by Void (2020-04-24 17:33:52)

kbd512 · 2020-04-24 20:36:16

Void,

Is this supposed to be another hybrid solid rocket?

Reusing a conventional liquid fuel type rocket engine would be fairly difficult unless you had a way to melt a plug of solid Magnesium through the various propellant feed lines, turbo pumps, and main injector plate. You'd most likely be feeding a cryogenic oxidizer and molten metal into a turbo pump and I'm not sure how well that would actually work in practice, even on the first firing. Maybe electric turbo pumps instead? Anyway, you'd still have to get every part of the fuel feed system scorching hot after the first firing. Perhaps single-use ceramic parts?

Void · 2020-04-24 21:12:28

KBD512

I am so happy you have taken an interest and....

May I sincerely wish good health for all of your family. I have been watching.

So, I also appreciate your criticisms, questions, and attempts to help with a solution.

……

For the Moon honestly for quite a time I think the game is Hydrogen and Oxygen. Maybe Methane and Oxygen if they can somehow source some Carbon.

I am just having some fun with Magnesium. If ever, I would expect any useful engine may be 50 years off, maybe 100.

The easiest game would indeed be a preheated Magnesium hollow slug, and you might shoot hot steam of water vapor through it. As you seem to have pointed out, it becomes hard to understand how to reuse such a thing. Not impossible, but a real problem.

But, say your game is to extract resources from the Moon to some orbit somewhere. Then you can prime such a machine do the burn(s), and then put it into the recycle bin to build things from it's metals. So, that may not be utterly ridiculous to think of. Mostly I think we want to get stuff from the Moon. At least at this time. Now I think I have been suggested to that you have speculated of a mass driver system. So, this then perhaps being a small device of many continual repeats of type, could be directed towards a reception. The Mass Driver would give it a kick, and hopefully it would be able to complete delivery to whatever reception area is possible and desired.

And that is perhaps the most conceivable edition of the method.

However instead of hot steam, it just might be possible to use a cold mix of water and Hydrogen Peroxide. In this case I am not too concerned that the Oxidizer is cold and the fuel is pre-heated. I think it could be OK.

And then LOX instead. I still think it could squeak through.

However, I really like the idea that Magnesium burning with a mix of water and Hydrogen Peroxide, will result in some molecules of Magnesium Oxide, and Hydrogen. At least that is what I have read. I know that Hydrogen is the desired propellant for Nuclear rockets, because of it's nature of expansion. I feel that it's expansion may be helpful to kick the Magnesium Oxide molecules out of the nozzle. And the Magnesium Oxide molecules should have relatively greater inertia, so the two working together might make a fine action/reaction situation for the rocket. I am exploring here you understand. I am not speaking as an expert. It might tend to plug the nozzle(s), but if it is a one time use situation, then perhaps it can be gotten away with.

So the above are, I think, what are called "Hybrid" Rockets. In this case the fuel is solid, and the Oxidizer is a fluid.

-----

But I think it is conceivable that the fuel could be a liquid. In that case perhaps hot steam of water could be used as the Oxidizer. Don't really have a complete notion of engine design, but think that even if the steam is high pressure, you have to impose pressure on it to push it into the combustion chamber. Perhaps Rocket Labs solution could work. Batteries. That is not too uncomfortable.

And then there is the option to consider cold Oxidizers against a hot liquid metal fuel. That is indeed scary to think of how to do and somehow get satisfying results. It is a long way off I think, if ever.

I feel that there is a possibility for a Kaboom, and it would be nice to harness that but maybe it is too much of a wild horse. Anyway I will continue.

Anyway water, or a mixture of Hydrogen Peroxide and water, and LOX, would the likely possibilities. However, as I think you have indicated, it is hard at this time to not fear failure in putting them together in an engine. However these should be things that can be able to have energy, of Kaboom! Just don't know what an engine like that would be like. Don't know if even possible.

In these cases if possible I would prefer a liquid of both the fuel and the Oxidizer, but then you are making a hot fluid interact with a cold fluid. Lots of challenges there. The reason I prefer it is that then the pressurization of the propellant tanks are not a big challenge.

Hot Steam of water is easier, but then you have to make the tank very thick. But that might be OK, if your objective it to deliver the tanks metal to some orbital location for recycle to a constructed object.

There are so many considerations in all of this.

-----

Then, what if you could have a steam of Magnesium?
I deferred to liquid Magnesium, because, I felt that that would be more dense than a steam of Magnesium, and easier to handle and produce.

But I will go there now.

If you go to post #189, you may see what I think the parameters for that are.

I believe that if someone really wanted to try that , then you could have a steam of Magnesium inside of a metal tank. Perhaps Stainless steel. (Unless I have the wrong numbers). Or go to Titanium if you must. Titanium is a very minor part of lunar materials I believe though.

So, then, in that case very hot steam of water, and a steam of Magnesium.

Probably not a good idea to use a cold Oxidizer.

Kabooms! And the attempt to harness them.

50 or more years off I think though, if ever.

Thanks for your interest KBD512, be well.

Done

Last edited by Void (2020-04-24 21:59:51)

GW Johnson · 2020-04-25 13:06:03

The easiest way to handle magnesium is as a particulate in a fuel-rich composite solid propellant. You burn that propellant for its magnesium vapor-rich effluent, which you then combust with a suitable oxidant in a second chamber. There will be copious mag oxide-rich slag produced, which tends to plug-up nozzles, clog equipment, and coat insulators.

Decades ago, I had extensive engineering design and test experience with this material and that fuel-rich solid "gas-generator" approach. Not only was it the fuel supply in the old Russian ramjet-powered SAM SA-6 "Gainful", I used it in a variety of other ramjets. In all of those, the oxidant was air scooped up with inlets fed to the second combustion chamber. But it could be any appropriate liquid rocket oxidizer, as well.

The Russian fuel propellant was a pressed composition resembling (but not at all the same as) a magnesium flare composition. I know how to make it. But my preferred form is a castable fuel propellant, made with a two-part silicone rubber binder and a dash of AP oxidizer. I used that stuff for decades as an utterly-reliable ramjet combustor igniter. It made a great ramjet fuel supply as well.

GW

Last edited by GW Johnson (2020-04-25 13:07:16)

Void · 2020-04-25 13:50:51

Wow! Thanks for showing up G.W.. The Moon does not seem to have much Carbon, so that last paragraph especially seems to point to a method.

As for those very exotic other things I pondered on, lets leave those for the Kids and Grandkids to figure out, 50 to 100 years from now. Or to fail, because it just can't be done.

Some times when a person is fudging around with things, it is best to find solid footing. You have given me some.
Also as I recall "Gerard K. O'Neill" had a notion of having bags of Lunar regolith flung by a mass driver to a rotating device that would catch them. I would not trust it, but he did try to find some sort of way.

I was afraid the nozzles would plug up. However, I am hoping that for a one time use somehow a way can be found to get away with it.

My notion(s) are to try to use a mass driver to boost something like a self guiding small rocket shell. That having been primed with some type of rocket propellant derived mostly from Moon materials. Maybe it is possible.

And then it will have greater guidance than a bag of rocks. A receiver not to different perhaps from what "Gerard K. O'Neill" had in mind.
A fairly gentile bump bump landing into a rotating device.

The metals to be recycled into useful things in orbit and to be sent to Mars. The AI and other important items returned to the Moon for reuse, if possible.

I guess at this point I think that K.I.S.S. needs to be applied to the degree that can work.

Thanks for the help Sir.

Last edited by Void (2020-04-25 14:03:03)

GW Johnson · 2020-04-25 15:58:42

Void:

Bear in mind that any such magnesium propellant system, even as a hybrid with liquid oxygen, is going to have relatively low performance. I'd guess under 300 seconds.

The propellant is ground-up particles of metallic magnesium, probably around 60% of the propellant mass, and around 30-50 microns average size. As a castable, you'll need about 20% AP, and 18% binder. I used a 2-part silicone from GE for that. The other 2% is ballistic tailoring aids and opacifiers, like yellow iron oxide and carbon black.

At 82% solids, it is easily sleeve/gravity castable. Being the dominant component, the mag particle size distribution is what will control your burn rate. Ballpark, it's about 0.5 inch/sec at 77 F soak temperature. Class 1.3 explosive. It'll show rather insensitive in most of the safety tests, with an autoignition temperature above 500 F. Burn rate exponent will be in the 0.2 to 0.4 range.

Whatever you do for a magnesium propellant, you need its heat of formation and empirical chemical formula for your thermochemistry code (and they go together, it's not a mix-and-match sort of deal). Then run it with something like liquid oxygen, for use in a solid fuel/liquid oxidizer hybrid. That gets you an upper bound on performance. As long as there is vapor oxygen among the oxygen stream being sent to the second chamber, the vapor mag will ignite hypergolically. No need for a secondary chamber igniter.

The gas generator nozzle throat will get slagged-up by the mag oxide. Steady-state (except it's not) that would be about the 50% throat area reduction class. It's an unsteady-with-time "slag-up and shuck" kind of behavior. The chamber pressure will vary wildly as this occurs, which of course varies the instantaneous propellant burn rate. You'd better have a pressure vessel capable of holding those wild swings. Factor 1.3+ on pressure, and it's that low only because the burn rate exponent is that low.

The mag oxide deposits will make your secondary chamber liner more effective at resisting erosion. But it will also affect the secondary throat area, pretty much the same way as the gas generator throat. I would think you want a gas generator throat that is choked to control its average flow rate to a fixed value. That means the min generator chamber pressure is at least twice the max secondary chamber pressure.

The gas generator igniter is far more effective if it is what is called a pyrogen igniter, because fuel-rich mag propellants are very difficult to light. I used little cubes of rocket propellant on a hot wire for that. Pellet-containing BKNO3-type igniters can be quite "iffy" because they are too brief a pulse, and far too brisant for this application.

You have to decide whether to make an end-burner versus an internal burner grain design. The web to be burned (distance through the propellant) is average burn rate times the required burn time. If that is some fraction under about 35% of the motor diameter, you are looking at an internal burner.

If it is longer, you are looking at an end burner. There are no end burners that burn ideally, without bondline burn rate augmentation. They will all "cone" to some significant degree. That can easily change the burning surface by a factor up to around 1.5, leading at low exponent to another factor of 1.2 on pressure.

You can do this, but there are a whole lot of real-world issues to address, as this post indicates. Most folks would never know to even worry about these things. That's just the nature of solid internal ballistics, one of the several engineering disciplines I am expert at.

There aren't a whole lot of us left with any experience at using mag propellants. That's rare indeed. But I am one.

GW

kbd512 · 2020-04-25 16:18:41

Papers from actual testing performed by NASA indicates Mg/CO2 and Mg/LOX top out between 220s (Mg/CO2) to 250s (Mg/LOX). Maybe modern technology could improve upon that by a little bit. That's not remarkably different than current production solid rocket technology.

Void · 2020-04-25 20:42:33

GW and KDB512 I really appreciate your interest and advice. I am pondering the situation. Of course I will never do these things, but I like the puzzle.

GW, it was great to have deep insight into what you did. I appreciate your sharing it. KDB512, I agree say 50 years from now if technology expands new tricks may be possible to enhance the possibilities.

Problems to solve are how to steer the thing. I suppose to regulate it's speed at certain points is part of that, and might be done with a Hybrid.

So, I have two ideas in my mind. In one case these things would be mass produced mostly by telepresence on the Moon's surface, and hopefully with lunar materials as much as possible.

The other one would be to just build a big rocket, and maybe as necessary include with it some Hydrogen/Oxygen booster or a Methane/Oxygen booster. On the Moon, that could be like a ring with several thrusters. It would be wrapped around the solid booster(Hybrid), and would help it get off the ground, and maybe guide the payload (The apparatus in the center), to its reception point.

Then the ring would detach and head back to the Moons surface.

So then we would have a sort of backwards space shuttle. Instead of the solid rocket(s) being on the outside, the solid rocket would be on the inside. The solid would be delivered to the reception point to be recycled into orbital space machines. The liquid ring rocket would be re-used as much as possible and would be well situated to not tip over when it landed back on the Moon.

The "Ring Ship" which would be liquid fueled, would have a hinge at one point and a latch 180 degrees opposite so that you could open it to encompass yet another solid rocket booster. It would need wheels on its legs.

So those are my two candidates, one for the small ones needs a Mass Driver. For steering thrusters, I wonder if we could use small centrifuges. Something like spin launch. You would time pulses of Oxygen into it so that they would shoot off in just one desired direction.

I wonder if you could make something like that howl? In other words could you actually heat the Oxygen up because you are creating something like re-entry heat. No matter, if you could push gas in one direction you would have steering, provided you could alter that direction as needed. You might need more than one of them. But maybe just one on the nose of the device actually.

So, for the small one a Mass Driver boost, and centrifuge steering in the nose perhaps. I want them to deliver LOX also actually. And so the body of the hybrid rocket to be recycled into orbital machines but also LOX delivered as well.

This is to replace the bags of regolith that Gerard K. O'Neill Had in mind. And those bags were supposed to impact a spinning "Catchers mitt", and so cling to the inside of it by centrifugal force.

The interior of the "Catcher" would need to be cold, or it would be necessary to process the object quickly so as not to loose the LOX.

For the "Big One", with the liquid rocket ring booster, the Hybrid might even be so built that you could remove the remnants of the fuel, and use is as is, joined to others??? Maybe.

GW, your recipe includes Carbon Black. I know that Elon Musk would like some Carbon on the Moon also, but it may not be available, so I will try to cheat reality. In the same way I might as well work with water ice. There are locations on the Moon remote from the poles, and if we had sourced water from somewhere then we might deliver it by a cheat mode. I presume that this Carbon and Water come from somewhere else in the solar system. Perhaps a NEO. Perhaps Mars even, or Earth.

So on the big version, I propose a liquid fueled ring booster. If we want to deliver Carbon and or water ice. We could somehow bring them from wherever the hybrid rocket was delivered. In some kind of minimal containment. Perhaps a bag. That would be fastened inside the ring booster. Maybe it would be a metal hopper of some kind with a door at the bottom to drop the stuff out before final landing burn.

See I don't want to pay full price, I just want the stuff to drop out somewhere where it can be retrieved. It is just Carbon and Ice after all.

I think you could drop Carbon anywhere on the Moon. The only trick is not to scatter it to much. Carbon has a very high vapor pressure I believe. Is that how it is said, I think?

This is mostly for the other readers, but a reference for us as well I suppose:
https://en.wikipedia.org/wiki/Carbon
The sublimation point is listed as "3915 K (3642 °C, 6588 °F)".

So the main concern for Carbon is that it does not scatter more than you want when you dump it overboard.

As for Water Ice, I have the ability to remember things that interest me and recall them as they are useful to a puzzle. Water ice well chilled could be also dropped on the night side or the Moon or the polar shadowed craters, with relatively little water loss, as long as it was collected before the sun can work on it.

This is my remembered item about that. Long ago I read that you could impact the dark side of the Moon with a block of ice, I presume at fairly high speed, and perhaps ~40% of it would vaporize, and so cool the other ~60% which would remain ice until the sun started working on it. The night side can be very cold as we all know.

But I don't propose really high speeds, I just want to dump it before the biggest part of the ring boosters landing burn.

I think I am starting to prefer the big version with the ring booster which would have liquid propulsion. If we can source Carbon, and Water Ice to locations on the Moon, then we may work with Methane and Oxygen if we like. We also don't have to feel guilty about depleting the polar deposits. And we could work at almost any location we wanted to on the Moon. For instance a preferred mineral deposit which was not near the poles.

I feel you have both be supportive and helpful. I appreciate it. Good Night

Last edited by Void (2020-04-25 21:32:24)

Void · 2020-05-01 15:52:12

I have not noticed if anyone posted this yet:
https://www.reuters.com/article/us-spac … SKBN22C3DI

Quote:

By Joey Rouelette
(Reuters) - NASA on Thursday selected space firms SpaceX, Blue Origin and Dynetics to build lunar landing systems that can carry astronauts to the moon by 2024, the White House’s accelerated deadline under the space agency’s moon-to-Mars campaign.
The three companies, which include firms of tech billionaires Elon Musk and Jeff Bezos, will share $967 million from NASA, though specific amounts each company will receive were not immediately known.
Boeing Co (BA.N) proposed a lander concept last year but was not selected.
Advertisement
“This is the last piece that we need in order to get to the moon,” NASA administrator Jim Bridenstine told reporters on Thursday, calling the agency’s first lunar lander procurement since 1972 “historic”.
Unlike the Apollo program that put astronauts on the moon nearly 50 years ago, NASA is gearing up for a long-term presence on Earth’s satellite that the agency says will eventually enable humans to reach Mars, leaning heavily on private companies built around shared visions for space exploration.
Picking three providers allows NASA to have redundancy in case one company falls behind in development, Lisa Watson-Morgan, NASA’s human landing system program manager, told reporters on Thursday.
“I think we’ve got the potential for an incredibly exciting future in space with a base on the moon, and ultimately sending people and having a self-sustaining city on Mars,” Musk, who also leads electric car firm Tesla, said Thursday.
Last year, Bezos unveiled Blue Origin’s design for the lunar lander, Blue Moon, it intends to build as a prime contractor with Lockheed Martin (LMT.N), Northrop Grumman (NOC.N) and Draper. Blue Origin plans to launch its landing system using its own heavy-lift rocket, New Glenn.
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And then SpaceX apparently has this:
https://www.floridatoday.com/story/tech … 086293002/
Quote:

SpaceX reveals new supersized Dragon XL for NASA’s lunar space station

I presume that they will use the not crew rated Falcon Heavy.

I know that quite a few here hate the Gateway, but I feel better about it now that they have a resupply method from SpaceX, and are planning for various options for lunar landers.

This is probably not how it will work, but it occurred to me that for the Dragon XL could be put into orbit by a Falcon Heavy, and then perhaps given more propellant by a Starship, so that it could do missions further. And you could get crew up to orbit with a crew Dragon,
Transfer to crew to the Dragon XL. Don't know that the Dragon XL would have life support though.

However if it eventually did, then you could use the Starship as un-crewed. And the Dragon XL might even be able to push a package to a location desired, that package could be on the exterior, similar to how the LEM was attached to the Apollo capsule.

Not saying it will be done, just saying I can imagine it.

Now that I think of it, a Dragon XL hooked to a crew Dragon, could probably stay in orbit a lot longer, provided that the Dragon XL provided extra consumables. And if the orbital assembly could be given more propellant by an un-crewed Starship, perhaps some type of longer mission might be possible. Don't know what that would be though.

And I might as well go further, you could perhaps just connect a crew dragon to a un-crewed starship, and do some kind of mission. Repair Hubble? That about all I can think of.

Too bad crew dragon cannot do a Lunar landing and assent.

Last edited by Void (2020-05-01 16:12:55)

Void · 2020-05-01 20:00:26

This is a nice article:
https://www.teslarati.com/spacex-moon-s … ards-mars/

I have read articles that suggest that a fuel source might travel with it to lunar orbit.

To me that makes perfect sense. Something like a barge is done in the USA. Here I believe the tug pushes the barge.

I am under the impression that in Europe, sometimes the loads are pulled. Right or Wrong on that does not matter.

And I read that the ship, if necessary could carry 4 suited crew members up and down.

Would have 2 airlocks, which makes me wonder why the crew needs to be in suits. Safety in case of a hard landing maybe.

So it suggests that the Moon-Starship, might push a depot, and a whole bunch or hardware for the Moons surface to Moon orbit.

I don't know how long Vacuum Raptor engines can fire. Don't know if there is a limit. But you would only be using 3 raptor engines to push a giga-ton of stuff to orbit around the Moon. Perhaps they can fire for a long time, tapping the propellant depot.

Among the things that could come along could be Carbon. If water were brought up from the Moon, then fuel could be manufactured in Lunar orbit, as per doing it on Mars. On the other hand if you brought Carbon down the Moon, you could generate CO2, by baking regolith in an oven with the Carbon. (I think). Then of course manufacture Oxygen and Methane on the surface of the Moon with the CO2 and Moon water.

And of course I am going to recommend the Carbon Drop. That is expel the Carbon to fall to the Moons surface before the Moon-Starship lands, lightening the load.

Substantial legs could be added to the Ship, and in them containers for Carbon. Drop the Carbon before you land. Less landing power then needed.

And as a matter of fact I think that the main cargo bays should be on the legs. It would make the lander bottom heavy, and make it easier to unload. Those leg cargo bays, could be attached to the Moon-Starship after it reached LEO.

Thereafter, no trouble with atmosphere, just a vacuum environment.

And I see this variant having other missions.

I see such a thing going into Martian orbit, using Ballistic Capture, and no Aerocapture.

Then to study Phobos and Demos.

I suppose many of you are not wild about that, but to know what Phobos and Demos would have to teach, would make it more probable that a attempt to settle Mars will succeed, as to know the history of Mars and it's moons is to better understand what you are dealing with.

However I expect that any scientific personal, to work with that mission, would first land on the surface of Mars in a Martian capable Starship, and then would be brought up to orbit, to assist in the analysis of those two moons.

Last edited by Void (2020-05-01 20:13:57)

Calliban · 2020-05-04 06:34:14

Interesting idea.

From memory, liquid aluminium and magnesium are quite corrosive to most metals and thus difficult to contain. On the plus side, pumping could be accomplished using MHD pumps which have no moving parts. The propellant tanks would need to be pressurized by a noble gas, as these are the only gases that won't react violently with Al or Mg vapour.

I take it most of the ISP is generated by super heated metal vapour rather than oxides themselves? In that case, the mixture would need to be fuel rich.

Void · 2020-05-04 10:59:10

Calliban,

Thanks for your interest and your insight. As you must have already discerned I am completely an amateur in this material.

I did want to explore heated combustible metals. I believe the Soviets/Russians have worked on combustible metals propulsion. Don't know much about it. GW was kind enough to describe his craft where he had a solid fuel that included a combustible metal (I believe).

As I thought about it I realized that if any such liquid metal fuel method were to appear ever, it would likely be 50-100 years from now. While it was fun to contemplate, I also annoyed two members who felt that the Magnesium should be used in material goods, such as alloys. They wouldn't let me have any mg

And just now there are so many fabulous machines being contemplated for the Moon using Hydrogen + Oxygen, or Methane + Oxygen.

Very exciting machines, and much closer to doable now or soon, so my excitement goes there for several reasons. I am capable of setting something aside. It does not mean that I abandon it forever. Supposing I see a new factor which might expedite the creation of molten combustible metal engines, then I might wake up my interest again.

But for fun, I will mention something which might better illustrate what I am after. I know that you already know what that is.

A "HOT CARBON HYBRID ROCKEAT". Of course there is not much hope of a large quantity of Carbon from the Moon.

But Mars, and perhaps some of the asteroids could be a source. The Earth? I suppose maybe, but the performance of the rocket would have to be fantastic to justify lifting Carbon from the Earth.

I realize that you almost certainly understand what the qualities of Carbon are. But there may be other readers.

https://en.wikipedia.org/wiki/Carbon
Quote:

Sublimation point:
3915 K (3642 °C, 6588 °F)

So, I do not plan to think that this would be used to lift off of any significant sized object. However in orbital space, perhaps something could be done. I am thinking hot Carbon, and LOX, a Hybrid rocket.

So supposing you could have a shell that the Carbon could be installed into. Then solar energy, and of course an insulating surround for the Carbon holding part. That is one heck of a high temperature to heat the Carbon to. Not even sure Titanium could handle it. I will take a look.

It's not looking as fabulous as I wanted.
https://en.wikipedia.org/wiki/Titanium
Quote:

Melting point
1941 K (1668 °C, 3034 °F)

So, that limits how hot you can heat the Carbon, unless some other canister material can be created. I am thinking it is not likely.

So within those limits, I would have a somewhat heated Carbon, and LOX, and I would also add a bit of Hydrogen, to, (Maybe), improve the ISP. I am an amateur, I have already admitted that.

But the above example if practical, would include heat energy, and chemical energy, as propulsion sources. And to some degree it will be a steam rocket. Not water steam.

------

To demonstrate, how about a sauna rocket. (Yes, completely silly). If you had a canister with highly heated rocks, and passed water into that, of course you would get a steam output. It would be a steam rocket. A very silly steam rocket.

Thanks for your attention.

Very happy with the Lunar landers that NASA is promoting. So, as interest goes, the above is quite on the back burner.

Last edited by Void (2020-05-04 11:21:18)

Grypd · 2020-05-07 13:44:44

I know getting Magnesium on the Moon is reasonably easy but so is to get Aluminium and with that we can create a reasonable solid rocket which could well be made on the moon and then launch resources like Oxygen and possibly lunar water to Earth orbit much cheaper than a supply from the Earth.
At the beginning of this topic GCNRevenger stated quite clearly and correctly that to launch from the Earth to the Moon takes just a little less energy than travelling to Mars. But travelling from the Moon to Earth is much less energy requirement and if you can create a vehicle that uses lunar propellant to be able to travel not only from the Moon to Earth but also the other way then a Future lunar base becomes a viable plan

Void · 2020-05-07 15:32:24

A very encouraging post.

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