Author Topic: NASA tests methane engine  (Read 9014 times)

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NASA tests methane engine
« on: 05/04/2007 08:26 pm »

Offline Lee Jay

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Re: NASA tests methane engine
« Reply #1 on: 05/04/2007 08:43 pm »
Wow.

Offline sandrot

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Re: NASA tests methane engine
« Reply #2 on: 05/04/2007 08:57 pm »
I always asked myself: why in the exhaust plume (at least at amospheric pressure) you have those light areas, as a string of pearls?
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Offline William Barton

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Re: NASA tests methane engine
« Reply #3 on: 05/04/2007 09:01 pm »
I think those are called "shock diamonds." Caused by compression of the plume by the atmospheric pressure?

Offline sandrot

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Re: NASA tests methane engine
« Reply #4 on: 05/04/2007 09:15 pm »
Thanks for the proper naming. From Wiki:
Shock diamonds or mach diamonds are a formation of shock waves in the exhaust plume of an aerospace propulsion system, such as a supersonic jet engine, rocket, ramjet, or scramjet. It is formed when the supersonic exhaust from a nozzle is slightly over or under-expanded, meaning that the pressure of the gases exiting the nozzle is different from the ambient pressure. A complex flow field results as the shock wave is reflected at the free jet boundary, and the visible diamond-shaped pattern that gives the shock diamond its name is formed.
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Offline pippin

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Re: NASA tests methane engine
« Reply #5 on: 05/05/2007 08:33 am »
Anybody an idea, what kind of ISP you can get from methane engines?
OK, you have a cooling advantage, it does not have the bad habit to diffuse through steel, it is more dense than LH2 so there must be some reason it has not been done before.
Energy should be close to LH2, or at least better than any other hydrocarbon, right?
Didn't NASA originally plan for methane for the EDS?

The Story with the CH4-Generation on Mars is Incorrect, isn't it. I mean: you would have to carry a much larger volume of LH2 to Mars just to add some carbon there - I bet it makes not sense from a technical point of view.

Offline ShuttleDiscovery

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Re: NASA tests methane engine
« Reply #6 on: 05/05/2007 09:01 am »
Great video! Thanks :)

Offline Heg

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Re: NASA tests methane engine
« Reply #7 on: 05/05/2007 10:16 am »
Quote
pippin - 5/5/2007  10:33 AM

Anybody an idea, what kind of ISP you can get from methane engines?

(...)
According to astronautix.com not so much big comparing to the best Kerosene/LOX engines - for an upper stage engine up to 381 s (vacuum)  vs. 362 - 365 (vac.); see: http://www.astronautix.com/props/loxlch4.htm and http://www.astronautix.com/props/loxosene.htm accordingly. Which is rather surprising, given that methane has  the highest fraction of hydrogen per molecule of all hydrocarbons. But of course LOX/LCH4 technology can be seen as an infant one, despite many studies, so futher development could probably make things better. Bui it's just my speculation.
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Offline TyMoore

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Re: NASA tests methane engine
« Reply #8 on: 05/05/2007 12:55 pm »
I think the main advantage with methane is storability. Liquid methane's boil point is close to that of liquid oxygen, which is a lot 'wamer' than liquid hydrogen--so the boil off should be quite a bit less. Also, you can save weight on a booster by thinning the insulation over the fuel tank a bit from liquid hydrogen...

As far as making methane on Mars--it's not as much balogny if there's plenty of water up there. Water can be electrolyzed into hydrogen and oxygen. The hydrogen can be reacted with carbon monoxide in a Fischer-Tropsch synthesis reaction to create methane. No problem really--you just need a power source to supply process heat.

Also, I have been reading about an interesting but industrially important reaction: calcium carbide or other alkali carbide reacted with water to form acetylene. For calcium carbide the reaction:

CaC2 +  2H20 --->  C2H2 + Ca(OH)2. Acetylene is an important chemical used of course as a fuel for oxyacetylene torches, but is also an important precusor chemical to other important polymer reactions--its reactive carbon triple bond makes it highly prized for versatility in chemistry.

Acetylene can be fully hydrogenated too:

C2H2 +  2H2 ---> C2H6 which is ethane. Ethane can be a really good rocket fuel too. It has a higher boil point than methane, can be stored indefinately, and burns very well with oxygen.

So there are many possibilities open to the future martian fuel chemist.

Offline pippin

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Re: NASA tests methane engine
« Reply #9 on: 05/05/2007 06:11 pm »
The carbide stuff is fine, the problem is: you don't find that stuff in nature since it tends to react heavily with water, so that won't be a lot of help on mars. Regarding martian fuel: You are right, but if can gegerate LH2, you can just use that, as long as you don't plan to store it for a long time, which is probably not necessary for a lot of applications. But OK, if you need storable propellant, e.g. for land transport vehicles, that may be of some help...

Offline PurduesUSAFguy

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Re: NASA tests methane engine
« Reply #10 on: 05/05/2007 06:33 pm »
So what is the likleyhood of LOX/CH4 being developed enough to use a methane engine for the Lunar CEVs?

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Re: NASA tests methane engine
« Reply #11 on: 05/06/2007 12:06 pm »
From the article I gather that the main attraction to a methane engine is the huge amounts of it available in the solar system.

Offline TyMoore

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Re: NASA tests methane engine
« Reply #12 on: 05/06/2007 01:42 pm »
Gasseous methane/oxygen combination would also make a pretty good RCS propellant too. It should spark ignite pretty easily, or even with a platinum glowplug. About the alkali carbides--it would just be an intermediary: the calcium, sodium, or lithium would likely be found on Mars bound up as sulfates or chlorides. I am assuming of course that a nuclear reactor main base powersource will provide process energy to synthesize the necessary ingredients to make the methane, atleast on Mars. Electrolysis of water can supply the hydrogen and oxygen. I don't care much for the idea of shipping a tank full of LH2 all the way to Mars just to make methane as Bob Zubrin suggests--I think that there is likely (not completely proven) a high probability of extensive saline aquifers or permafrost all over Mars. Chances are excellent that there will be plenty of water to support extraction of hydrogen and oxygen in industrial amounts.

I think the original suggestion for Methane--atleast as far as Mars was concerned--was that on a Dry Mars, we can ration out our hydrogen supply somewhat by 'diluting' it with carbon reduced from atmospheric CO2. However, I think the "Dry Mars" hypothesis is starting to crumble in favor of a 'damp' or 'icy' Mars in which the water is there, just locked away out of sight so to speak.

Still, I think methane would make an excellant insitu fuel for propulsion--it is easily storable without much refrigeration from Mars, on out in the solar system. Extensive native methane deposits may exist on many satellites, and methane may exist as lakes or small seas on Titan. I think a methane/oxygen chemical propulsion technology makes good sense. Besides, methane is not quite as 'bulky' as liquid hydrogen, so tankage ought to be a little smaller and hence lighter.

As far as the Lunar Vehicle is concerned--I think the descent stage is supposed to burn LOX/LH2 running several (4 I think) RL-10 derivative engines, and the ascent stage is still 'up in the air' regarding LOX/Methane. My guess is that it will probably end up being LOX/LH2 or even N2O4/monomethyl hydrazine, maybe powered by a couple of Shuttle OMS engines. I'm not sure, but I think methane is dead as far as the Lunar vehicle is concerned...




Offline pippin

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Re: NASA tests methane engine
« Reply #13 on: 05/06/2007 11:04 pm »
Quote
TyMoore - 5/5/2007  3:42 PM

...I am assuming of course that a nuclear reactor main base powersource will provide process energy to synthesize the necessary ingredients to make the methane, atleast on Mars. ...


How do you come to have a nuclear rector on mars? Build it there? What from? Send it there? These babies are heavy... and all the fuel involved....
You might want a high temperature reactor, but then they are not developed for operational use even on earth...

Sounds like a LOOONG term vision to me...

Offline TyMoore

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Re: NASA tests methane engine
« Reply #14 on: 05/07/2007 01:31 am »
You send up a small one (about 100KWe, or about 500 KWt--total system weight maybe about 7-10 tons) and send that along as a part of the payload manifest. They aren't really that heavy, not for what they give you which would be years of power and heat. The mass comes from power conversion systems, and heat rejection systems. The main bulk of the radiation shielding will be made from Mars itself: you bulldoze up a burm around the reactor--bingo, instant radiation shielding. Also you locate the thing some distance away from the rest of your base.


Offline hornet

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RE: NASA tests methane engine
« Reply #15 on: 05/07/2007 02:31 am »
wow that is awesome.......now to put it on a car ;)

Offline pippin

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Re: NASA tests methane engine
« Reply #16 on: 05/07/2007 07:17 am »
Quote
TyMoore - 6/5/2007  3:31 AM

You send up a small one (about 100KWe, or about 500 KWt--total system weight maybe about 7-10 tons) and send that along as a part of the payload manifest. They aren't really that heavy, not for what they give you which would be years of power and heat. The mass comes from power conversion systems, and heat rejection systems. The main bulk of the radiation shielding will be made from Mars itself: you bulldoze up a burm around the reactor--bingo, instant radiation shielding. Also you locate the thing some distance away from the rest of your base.


"bulldoze" requires a bulldozer, doen't it. Icluding power supply. Might even be lighter to send all the stuff from earth.
What kind of reactor are you envisioning? Pressurized water reactor as seafaring vessels? That's the "light" ones of today but requires extensive external cooling. Lots of water around a ship. None at all on mars. Hmmm. By the way... lot of mass comes from pressurized containment.
Pebble bed reactor (or similar high temperature design)? That's the one you WANT to use since it's got a non-critical design (no rapid unsccheduled disassemblies contamining your whole base due to your reactor going critical) and you can get away with radiation cooling and a gas turbine instead of a (heavy) steam turbine and you don't need a (heavy) pressurized containment. However, it's not operationally proven, so count 20 year of development time, no need to start developing methane engines for that scenario today...
Then there is fuel. You still need a few tons of that (we are not talking about "pure" U235 or something, but a mixture in a containment). How do you send it there? You probably don't want to contamine half of your current habitate due to one of those (rare) chemical launcher failures so you need LOTS of containment around that while sending it up...
I don't think you will see a large scale nuclear reactor (that is: more then a pem or something of similar size) on mars until you have enough infrastructure up there to at least assemble it there and find your fuel locally...

Offline khallow

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Re: NASA tests methane engine
« Reply #17 on: 05/07/2007 10:45 am »
Quote
pippin - 7/5/2007  12:17 AM

Quote
TyMoore - 6/5/2007  3:31 AM

You send up a small one (about 100KWe, or about 500 KWt--total system weight maybe about 7-10 tons) and send that along as a part of the payload manifest. They aren't really that heavy, not for what they give you which would be years of power and heat. The mass comes from power conversion systems, and heat rejection systems. The main bulk of the radiation shielding will be made from Mars itself: you bulldoze up a burm around the reactor--bingo, instant radiation shielding. Also you locate the thing some distance away from the rest of your base.


"bulldoze" requires a bulldozer, doen't it. Icluding power supply. Might even be lighter to send all the stuff from earth.

The reactor can be the power supply.

Quote
What kind of reactor are you envisioning? Pressurized water reactor as seafaring vessels? That's the "light" ones of today but requires extensive external cooling. Lots of water around a ship. None at all on mars. Hmmm. By the way... lot of mass comes from pressurized containment.
Pebble bed reactor (or similar high temperature design)? That's the one you WANT to use since it's got a non-critical design (no rapid unsccheduled disassemblies contamining your whole base due to your reactor going critical) and you can get away with radiation cooling and a gas turbine instead of a (heavy) steam turbine and you don't need a (heavy) pressurized containment. However, it's not operationally proven, so count 20 year of development time, no need to start developing methane engines for that scenario today...

There's water on Mars too. It may be difficult to get to (eg, require drilling to tap briny water underground or digging up ice cap), but it is there.

Quote
Then there is fuel. You still need a few tons of that (we are not talking about "pure" U235 or something, but a mixture in a containment). How do you send it there? You probably don't want to contamine half of your current habitate due to one of those (rare) chemical launcher failures so you need LOTS of containment around that while sending it up...
I don't think you will see a large scale nuclear reactor (that is: more then a pem or something of similar size) on mars until you have enough infrastructure up there to at least assemble it there and find your fuel locally...

Tons of fuel? No you don't need that much for a 100KW system. The reactor itself can and should be the launch containment system. I can't find any details of the system, but apparently Soviet Russia had launched a space nuclear reactor, the Topaz which produces 10KW. The next version, the Topaz 2 would generate 40 KW and weigh considerably under 4 tons (including fuel and a satellite), according to this Encyclopedia Astronautica article. Note this design doesn't use water.

Quote
Use of a new high radiation-safety orbit was also demonstrated. The Topaz used a new thermo-emission conversion method to convert heat to electricity. This would also power a range of new systems including electrostatic manoeuvring engines, ion orientation/stabilisation engines, solar sensors, magnetic momentum compensators, multi-channel wave devices, and special plasma weapons to provide a defence against anti-satellite weapons. The Plazma-A satellites carried instruments to map the magnetic field of the earth, with an eye toward developing a magnetic navigation system. Topaz provided over 10 kW of power and had long endurance and storage in a radiation-safe orbit. A follow-on Plazma-2 would have been equipped with the even safer Topaz-2. The spacecraft would be orbited by a Tsyklon 2 booster and have a mass of 3550 kg. Despite these encouraging tests, the US-AM nuclear-powered component of the Pirs system was abandoned on the instructions of Gorbachev in 1988 due to continued reliability problems and international incidents when the reactor cores of the satellites crashed to the earth.
Karl Hallowell

Offline TyMoore

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Re: NASA tests methane engine
« Reply #18 on: 05/07/2007 12:23 pm »
This is getting way off topic--but I didn't say tons of fuel. I said total system weight--reactor pressure vessel, control systems, coolant circulation, power conversion, heat rejection, and oh yeah, the bulldozer. A small reactor no bigger than refrigerator using highly enriched uranium as fuel, probably straight Uranium-235 (93% enriched) alloyed with Zirconium to brind the Uranium content down to about 10%, cald again with zirconium, and then stuck in a tungsten cermet structure. It could be cooled with a pressurized water loop, or it could be helium cooled for a relatively high efficiency Brayton conversion system using gas turbines and an alternator. You'll get good cycle efficiency, long life, and lots of process heat for everything from a green house, to oh yeah, making methane in a Fischer Tropsch process, which you can then burn in those neat little methane engines.



Offline pippin

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Re: NASA tests methane engine
« Reply #19 on: 05/07/2007 01:11 pm »
Quote
TyMoore - 6/5/2007  2:23 PM

This is getting way off topic--but I didn't say tons of fuel. I said total system weight--reactor pressure vessel, control systems, coolant circulation, power conversion, heat rejection, and oh yeah, the bulldozer. A small reactor no bigger than refrigerator using highly enriched uranium as fuel, probably straight Uranium-235 (93% enriched) alloyed with Zirconium to brind the Uranium content down to about 10%, cald again with zirconium, and then stuck in a tungsten cermet structure. It could be cooled with a pressurized water loop, or it could be helium cooled for a relatively high efficiency Brayton conversion system using gas turbines and an alternator. You'll get good cycle efficiency, long life, and lots of process heat for everything from a green house, to oh yeah, making methane in a Fischer Tropsch process, which you can then burn in those neat little methane engines.



Yep. You're right, this is getting way off topic. But this is exactly the kind of reactor I was talking about. Did you see one of thiose somewhere? Recently? It's the right technology, certainly, but it's not htere and definitely has to be developed.

Offline privateer

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Re: NASA tests methane engine
« Reply #20 on: 05/07/2007 02:43 pm »
Quote
TyMoore - 5/5/2007  7:55 AM
I think the main advantage with methane is storability. Liquid methane's boil point is close to that of liquid oxygen, which is a lot 'wamer' than liquid hydrogen--so the boil off should be quite a bit less. Also, you can save weight on a booster by thinning the insulation over the fuel tank a bit from liquid hydrogen...

In this case, propane may be better:

___________ Methane Propane
Melting point -182.5   -187.6   (LOX boiling point is -182.95)
Boiling point -161.6   -42.09   (all temps are in Celsius)
Liquid density  0.42     0.58

See? Propane will also stay liquid at LOX boiling temp (with larger margin), but it will remain liquid in much wider range of temps. (Heh, -42 celsius is a normal ambient temperature in many areas on Mars!) Density is also notably higher. Two reasons why tanks can be lighter.

Isp of methane, ethane and propane (with LOX) is virtually the same IIUC.

Quote
As far as making methane on Mars--it's not as much balogny if there's plenty of water up there. Water can be electrolyzed into hydrogen and oxygen. The hydrogen can be reacted with carbon monoxide in a Fischer-Tropsch synthesis reaction to create methane. No problem really--you just need a power source to supply process heat.

Now this can be a problem for propane. How hard it will be to produce it instead of methane?

Offline Tom Ligon

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Re: NASA tests methane engine
« Reply #21 on: 05/07/2007 08:34 pm »
Don't you guys know?  We're going to stick out a few solar panels on Mars and use those to make fuel for the return trip.

The illustration of this I saw would have been about enough solar panels for an off-the-grid home, if you were stingy with power and had Earth sunlight.  I wondered how long they figured it would take to refuel the ship.

With the problem of reactor cooling being about the same on Luna or in space, and only slighly better on Mars, I wonder if the best use of the nuke might be to just be honest and go with nuclear propulsion.  If you have to carry the reactor anyway, find a way to use it that gives better Isp than chemical.  You still need reaction mass, but water or hydrogen get the job done.

On the moon, long-term some sort of launch rail may make the most sense from the standpoint of scarce reaction mass.

Offline BarryKirk

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Re: NASA tests methane engine
« Reply #22 on: 05/07/2007 09:11 pm »
For lunar stuff an EM railgun launch makes some sense.

1) No air friction.
2) Lower escape / orbital velocity so acceleration required is less.
3) Required Acceleration or rail length is still a little high for manned launch, unless, the EM rail
just provides an initial boost.

But, there may be a better possibility for lunar launch.

Lunar soil contains lots of Oxygen, Aluminum, and Iron.  There was some discussion a while back
of manufacturing solid rocket fuel on the lunar surface.  The ISP would be horrible, but it doesn't take much
to launch off of the moon.

Offline Tom Ligon

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Re: NASA tests methane engine
« Reply #23 on: 05/07/2007 09:46 pm »
The ISDC will have panel discussions and speakers on topics like this.  I may be on a couple.  About the only thing I can offer them is the possiblity of plenty of electric power if Dr. Bussard's reactor works.

That won't help a lunar base in the next 5 years.

I'm sure we'll use rocket fuel shipped up from Earth initially.  Luna is the only target without the option of aerobraking.  It is not a big problem to get off it, but it is as much problem to get down to it.

The result will be an accumulation of whatever it takes to get the fuel down.  At least tanks, probably landers.  The mass involved in getting that fuel to orbit and into TLI is no doubt worse.  At some point, the accumulated mass of those starts to make you wish you'd invested that in sending up something better.  Better sooner than later if you plan a continued presence.

Luna has a curious phenomenon in which dust is lofted electrostatically to great heights as the result of sunlight charging it.  Originally, this was very mysterious as it made it look as if the Moon had an atmosphere that it clearly did not.   This suggests to me that very fine lunar dust might be usable as reaction mass in an electrostatic motor of some type.


Offline BarryKirk

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Re: NASA tests methane engine
« Reply #24 on: 05/07/2007 09:57 pm »
Well, the ISP for that type of motor would be huge.  Again the problem is low thrust.  But with the moon
the thrust to weight ratio required is much lower than for earth.

I had no idea that lunar dust was present at altitude.  Thank you for that interesting tidbit of info.

Offline TyMoore

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Re: NASA tests methane engine
« Reply #25 on: 05/08/2007 01:34 am »
Quote
privateer - 7/5/2007  7:43 AM

Quote
TyMoore - 5/5/2007  7:55 AM
I think the main advantage with methane is storability. Liquid methane's boil point is close to that of liquid oxygen, which is a lot 'wamer' than liquid hydrogen--so the boil off should be quite a bit less. Also, you can save weight on a booster by thinning the insulation over the fuel tank a bit from liquid hydrogen...

In this case, propane may be better:

___________ Methane Propane
Melting point -182.5   -187.6   (LOX boiling point is -182.95)
Boiling point -161.6   -42.09   (all temps are in Celsius)
Liquid density  0.42     0.58

See? Propane will also stay liquid at LOX boiling temp (with larger margin), but it will remain liquid in much wider range of temps. (Heh, -42 celsius is a normal ambient temperature in many areas on Mars!) Density is also notably higher. Two reasons why tanks can be lighter.

Isp of methane, ethane and propane (with LOX) is virtually the same IIUC.

Quote
As far as making methane on Mars--it's not as much balogny if there's plenty of water up there. Water can be electrolyzed into hydrogen and oxygen. The hydrogen can be reacted with carbon monoxide in a Fischer-Tropsch synthesis reaction to create methane. No problem really--you just need a power source to supply process heat.

Now this can be a problem for propane. How hard it will be to produce it instead of methane?

Propane is certainly possible. I am no chemical engineer, but what I do understand of Fischer-Tropsch Synthesis is that by tweaking the composition of the catalysts and the temperature and pressure of the chemical reactor, then virtually any hydrocarbon can be fairly easily synthesized given feedstocks of CO and H2, or even carbon and steam, or Methane and Oxygen...given an energy source and plenty of feedstock chemicals, it should be possible to synthesize heavier hydrocarbons for really useful things like polymers and synthetic lubricants and greases.

Propane could be useful as a propellant, however, I would imagine that methane may well be easier to synthesize and may thus be an easier and more useful hydrocarbon synthetic propellant system for initial sorties.

In regards to using solar panels to provide process energy--yes, certainly possible. However, the beautiful thing with a nuclear system is that it can provide process heat necessary to get the synthesis reactions going. This could be done with solar panels, but the heater loads would necessarily add more collection area to the panels--no way to get around that. Not only that, solar photovoltaic systems necessarily mean a cyclic synthesis--methane synthesis can only occur during daylight cycles, unless you want to figure out how to store that much energy--lead acid batteries are way out of there, unless you make them from Martian materials... A nuclear power source can provide electricity and process heat 24/7, and so a continuous synthesis approach can be used which is likely simpler and more efficient anyway.

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