Why does nobody use Liquid-Propellant rockets?

RadManCF said:

So, how difficult would it be to distill 90% H2O2 from a lower concentration?

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Very, since commercial H2O2 has stabilizers in it that make it very difficult.

It's also not something you really want to mess with -- rather nasty stuff, if you do manage to concentrate it.

-Kevin

cwbullet said:

Do they still produce hybrid motors? I have not seen a hybrid, outside of hypertek, in ages.

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Yes, in addition to Hypertek, Rattworks, and Contrail are doing well. I don't know about Skyripper. In addition there are EX hybrids.

Here's a quick report from John Carmack at Armadillo Aerospace on the handling of hydrogen peroxide. In a simple test, they pour peroxide on different common materials like shoes, cotton shirts, nylon, etc. Video too. Quote: "The lessons are simple wear cotton, and make sure you don’t have any leather shoes, belts, or jackets."

(about half was down the page under 'Material test')
https://armadilloaerospace.com/n.x/Armadillo/Home/News?news_id=130


>> apparently the government watches those who have 90% H2O2 very closely

Naw... government doesn't care. The problem is with FMC, the main supplier of high strength peroxide. They are paranoid and won't sell to amateurs.

I believe X-L Space is now selling drum size quantities to amateurs, however.
https://www.xlspace.com/products.html

>> So, how difficult would it be to distill 90% H2O2 from a lower concentration?

Not too hard.. not too easy.. I think TAM sells a peroxide still for about $5k. I would be careful trying to build a still though. There are hidden issues concentrating peroxide.
https://www.tecaeromex.com


-->MCS


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troj said:

Very, since commercial H2O2 has stabilizers in it that make it very difficult.

It's also not something you really want to mess with -- rather nasty stuff, if you do manage to concentrate it.

-Kevin

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As a follow on, is the density of H2O2 different enough from that of H2O that the two could be separated with a centrifuge, like in uranium refining?

RadManCF said:

As a follow on, is the density of H2O2 different enough from that of H2O that the two could be separated with a centrifuge, like in uranium refining?

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No clue, and to be honest, the process for separation of the two is outside the range of this forum. As such, I'd prefer such topics not be discussed here.

-Kevin

MCS said:

Here's a quick report from John Carmack at Armadillo Aerospace on the handling of hydrogen peroxide. In a simple test, they pour peroxide on different common materials like shoes, cotton shirts, nylon, etc. Video too. Quote: "The lessons are simple wear cotton, and make sure you don’t have any leather shoes, belts, or jackets."

(about half was down the page under 'Material test')
https://armadilloaerospace.com/n.x/Armadillo/Home/News?news_id=130


>> apparently the government watches those who have 90% H2O2 very closely

Naw... government doesn't care. The problem is with FMC, the main supplier of high strength peroxide. They are paranoid and won't sell to amateurs.

I believe X-L Space is now selling drum size quantities to amateurs, however.
https://www.xlspace.com/products.html

>> So, how difficult would it be to distill 90% H2O2 from a lower concentration?

Not too hard.. not too easy.. I think TAM sells a peroxide still for about $5k. I would be careful trying to build a still though. There are hidden issues concentrating peroxide.
https://www.tecaeromex.com


-->MCS


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Click to expand...

Ther Carmack interview is 11 years old, and times have changed since 9/11. The government does care and does check where the stuff is going. Homeland Security, AKA Big Brother, is watching....

I've been tracking AA for a decade or more and unless I have missed something, I believe that Armadillo Aerospace has largely abandoned peroxide for a more conventional LOX/Hydrocarbon propellant. Why do think that might be? I also found the "safety" video hilarious, as did most professionals watching the amateurish operations back then....

While it is possible to buy a H2O2 concentrator from XL-Space for $30K, and possibly one from TAM for $5K, operating the still is not as easy as advertised, and after the first explosition, (and you will have a first explosion according to folks who have used them,) it is much preferred to purchase the high test peroxide directly from a commercial supplier than to concentrate your own.

Furthermore, not only is 90% peroxide expensive, it is expensive to ship, as is the 70% feedstock for the XL-Space. Both are classified as UN2015, Hydrogen Peroxide, stabalized, >60% concentration, 5.1 (strong oxidizer), 8 (corrosive), PG I(highest of three hazard ranges within a class), and it can only be shipped by truck or ship, not by rail or air, in special aluminum or teflon-lined vented drums. When Nick Macomber flies the jet pack overseas, he must have the peroxide transported by ship 3 to 4 months in advance, and hopes it arrives on time, and clears the destination country's customs and import authorities before the event's scheduled date.

While untrained amateurs may believe that high test peroxide is benign, professionals know it's not, and that's the only reason why we don't read about severe injuries or deaths associated with the amateur use of high test peroxide as an amateur rocket propellant. Why an amateur would want to use a dangerous and expensive and inefficient propellant like peroxide defies logic. As a monopropellant, you get a specific impulse of only 120 s from 90% peroxide. For about 25% of the cost, you get a specific impulse of >200 s from a decent commercial or amateur APCP formulation, and none of the dangers and hassles of transporting and using it. :wink:

Bob

While untrained amateurs may believe that high test peroxide is benign, professionals know it's not, and that's the only reason why we don't read about severe injuries or deaths associated with the amateur use of high test peroxide as an amateur rocket propellant. Why an amateur would want to use a dangerous and expensive and inefficient propellant like peroxide defies logic. As a monopropellant, you get a specific impulse of only 120 s from 90% peroxide. For about 25% of the cost, you get a specific impulse of >200 s from a decent commercial or amateur APCP formulation, and none of the dangers and hassles of transporting and using it. :wink:

Bob

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Don't worry, from what I'd read before, I had no illusions. I was just idly curious about what is theoretically possible. Now this has got me wondering if I could make brandy with a centrifuge....

RadManCF said:

Don't worry, from what I'd read before, I had no illusions. I was just idly curious about what is theoretically possible. Now this has got me wondering if I could make brandy with a centrifuge....

Click to expand...

Uranium is separated in the gas phase as UF6. (Which is another nasty, toxic and flammable chemical.) The difference between between the molecular weights of the hexafluorides with U235 and U238 is less than 1%, so no matter which way you attempt to separate the isotopes, it has to have a cascade of many stages and it is is an extremely expensive process.

H2O and H2O2 are totally misable, but the vapor pressure of H2O2 is much lower than H20, so vacuum distillation is the method of choice for separation. You can't use regular distillation at atmospheric pressure since the peroxide will explosively decompose as it nears the boiling point. Dilute peroxide and high test peroxide react very differently. Dilute peroxide solutions are used to bleach hair, disinfect water and surfaces just like bleach and performs many other useful functions safely. Dilute peroxide solution will bubble vigorously if a chemically or thermally induced decomposition occurs, but steam will not be generated. High test peroxide on the other hand decomposes into steam and O2, instantly increasing its volume by a factor up to 5,000, and will explosively rupture a sealed container. It has been used to make IEDs and other explosive compounds and therefore is monitored by HSA.

While there there are niche spacecraft applications, hydrogen peroxide is a very mediocre and expensive propellant, and simply isn't worth messing with when compared to APCP or hydrids which are far cheaper, better and safer propellants.

Bob

bobkrech said:

Uranium is separated in the gas phase as UF6. (Which is another nasty, toxic and flammable chemical.) The difference between between the molecular weights of the hexafluorides with U235 and U238 is less than 1%, so no matter which way you attempt to separate the isotopes, it has to have a cascade of many stages and it is is an extremely expensive process.

H2O and H2O2 are totally misable, but the vapor pressure of H2O2 is much lower than H20, so vacuum distillation is the method of choice for separation. You can't use regular distillation at atmospheric pressure since the peroxide will explosively decompose as it nears the boiling point. Dilute peroxide and high test peroxide react very differently. Dilute peroxide solutions are used to bleach hair, disinfect water and surfaces just like bleach and performs many other useful functions safely. Dilute peroxide solution will bubble vigorously if a chemically or thermally induced decomposition occurs, but steam will not be generated. High test peroxide on the other hand decomposes into steam and O2, instantly increasing its volume by a factor up to 5,000, and will explosively rupture a sealed container. It has been used to make IEDs and other explosive compounds and therefore is monitored by HSA.

While there there are niche spacecraft applications, hydrogen peroxide is a very mediocre and expensive propellant, and simply isn't worth messing with when compared to APCP or hydrids which are far cheaper, better and safer propellants.

Bob

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And as I understand things, the enrichment process can take years, depending on the level of enrichment desired. IIRC, LEU can take up to a year, and is only about 3-5% U235. Weapons grade is upwards of 90% U235.
Thanks for the tip on vaccum distilation, I'll have to read into it; this thread has really got me curious about distillation without heat. The only process I knew of before this was that used for ice beer.

troj said:

Very, since commercial H2O2 has stabilizers in it that make it very difficult.

It's also not something you really want to mess with -- rather nasty stuff, if you do manage to concentrate it.

-Kevin

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I know all about H2O2 in bulk. I would stay FAR away from that stuff as far as I can, and I was only working on trucks that ship 75% concentration (product pump repair outside).

RadManCF said:

And as I understand things, the enrichment process can take years, depending on the level of enrichment desired. IIRC, LEU can take up to a year, and is only about 3-5% U235. Weapons grade is upwards of 90% U235.
Thanks for the tip on vaccum distilation, I'll have to read into it; this thread has really got me curious about distillation without heat. The only process I knew of before this was that used for ice beer.

Click to expand...

The isotope separation process itself doesn't take that long, but it is very expensive, and time consuming to built and start up. I'm guessing north of a billion dollars if you start from nothing...

Vacuum distillation still requires heat. It simply occurs at subatmospheric pressure. Water boils at 20 torr pressure at room temperature. If you pump on water at room temperarture, it will boil, carring away heat and cooling the water. If you continue to pump on the water without adding heat, you will eventually freeze the remaining water and make an ice cube! You can also concentrate liquids with fractional freezing, but this is a little more complicated.

Bob

At FAR Paul Breed has an H2O2 "refinery". It's on the barren end of the test site and partly buried. Additionally at FAR there are drums of explosives, chemicals, and other misc. dangerous things. The firesigns show 444 and they aren't kidding.

Liquid engines are extremely dangerous, as are the chemicals, and by the time you get to that level, you're not in the "hobby" world anymore.

bobkrech said:

The isotope separation process itself doesn't take that long, but it is very expensive, and time consuming to built and start up. I'm guessing north of a billion dollars if you start from nothing...

Vacuum distillation still requires heat. It simply occurs at subatmospheric pressure. Water boils at 20 torr pressure at room temperature. If you pump on water at room temperarture, it will boil, carring away heat and cooling the water. If you continue to pump on the water without adding heat, you will eventually freeze the remaining water and make an ice cube! You can also concentrate liquids with fractional freezing, but this is a little more complicated.

Bob

Click to expand...

So fractional freezing, that's the technical term for what's done to ice beer?

>> Homeland Security, AKA Big Brother, is watching....

It's only classified as a Chemical Of Interest. So is AP and aluminum powder.


>> While untrained amateurs may believe that high test peroxide is benign

ABSOLUTELY NO ONE SAID THAT!


>> Why an amateur would want to use a dangerous and expensive and inefficient
>> propellant like peroxide defies logic.

Because if your heart is set on building a liquid, a monoprop is way, way easier than any biprop.


-->MCS

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FWIW.. one of the few deaths in our hobby was Phil-{can't remember last name} who died in a runaway Peroxide explosion.

-->MCS

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MCS said:

Here's a quick report from John Carmack at Armadillo Aerospace on the handling of hydrogen peroxide. In a simple test, they pour peroxide on different common materials like shoes, cotton shirts, nylon, etc. Video too. Quote: "The lessons are simple wear cotton, and make sure you don’t have any leather shoes, belts, or jackets."

Click to expand...

Cotton may not react immediately, but if there is any source of ignition at all you will quickly turn into the human torch.

[video=youtube;5rSqrWHE8Gw]https://www.youtube.com/watch?v=5rSqrWHE8Gw[/video]

awseiger said:

Why does nobody use Liquid Propellant rocket motors? If someone were to develop one that was "pop in/out" like our AP and Hybrid motors are, could it be certified by the NAR and used?

It just seems odd. I feel like constructing a little mini liquid rocket wouldn't be terribly hard. Of course, you'd have to supply the fuel, which is probably not the safest thing to have hanging about in your basement. These things can be averted, however. A tank of oxygen and a bottle of kerosene are sitting in my garage...

Is there anything that explicitly denies Liquid propellant motors from being certified?

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I realize this thread is a little dated but I thought I'd drop in and share my personal experience on liquid propellant based rockets. As engineers we often talk about orders of magnitude. Building a liquid propulsion system is easily an order of magnitude more difficult and expensive then a simple AP/HTPB solid. I spent probably 5 years trying to keep my system as simple as possible. After getting the propulsion system working I went ahead and committed to building a flight vehicle around it. At this point I found myself with another order of magnitude worth of work to complete that project. Several years later my vehicle finally took to the sky.

Many thousands of hours of work for a 10 second engine burn. I still get exhausted today when I think about it. I also know that without the help of my fellow RRS members that none of this would have ever happened. I can't image a more rewarding project then this was. Everything had to be custom made, tested, re-tested, adjusted, etc. When you sit down and begin to write down what needs to happen it quickly expands and you quickly come up with a huge list. I think I had a thousand line items at one point that had to be accounted for. Who is bringing the LOX for the test?I Do I need to rent a dewar? Did I clean my LOX transfer hose? Where is it? Did I pack the welding gloves to handle the cryogenics. Are all the tools O2 clean? Do I need to do another leak check after transferring the test equipment to the MTA? The end result is you bring out about 5 tons of equipment and spares. Spare electronics, batteries, Pyro's, e-matches. Is the laptop charged? What happens when windows crashes your ground support software after you close the vents and pressurize the vehicle.

Now I don't want to discourage anyone from pursuing such a project. But to the OP's initial post I don't see a true liquid motor design as being feasible in the hobby community. I think hybrids are about as complex an engine as you'll see in the general rocketry world.

Liquid rockets actually get more challenging the smaller you go. The smallest liquid rocket I ever saw was made by Tom Mueller (SpaceX). He had an amazingly small liquid rocket that had pyro activated valves a super tiny combustor. It was also prone to hard starts due to its tiny size.

So I hope I added to the discussion a little.


Eric

Thanks for the information, Eric -- you've been there, done that, and have real world experience in what's involved.

-Kevin

In the 1990's there was a magazine called High Power Rocketry The October 1994 issue has a couple of different liquid engines. Page 12 Title is HOT & Steamy about using h20 turned into steam. Page 72 has a report from Reaction Research Society using 151 rum and LOX (75.5% ethly alcohol and water). static test on 20 march 1993 shows 1600 lbs thrust.

The Dec 1994 Issues has a 1000lb thrust (lox and jet-a)and the third report on the 1600lb (1620 Lbs now) thrust engine from the Oct. issue. It further shows different test engines including a hydrogen peroxide all plastic hybrid system.

The February 1995 issue has an article called the First Amateur Space Shot done by Pacific Rocket Society using a 2000lb lox/alcohol engine.

August 94 issues talks about some old tests done in the 50's using hydrogen peroxide as well.

Sadly I lost the issues due to several moves, the articles were full of awesome photos and charts showing output. I have an index telling what articles talked about what , but the magazines are long gone...

"awseiger says he has an oxygen cylinder and kerosene in the basement", if you try to make your system using this, just remember any hydrocarbon gets in the oxygen line while it flows under pressure will cause an explosion. (work at a welding supply store and safety is a big issue).


Mike

mbauer said:

In the 1990's there was a magazine called High Power Rocketry The October 1994 issue has a couple of different liquid engines. Page 12 Title is HOT & Steamy about using h20 turned into steam. Page 72 has a report from Reaction Research Society using 151 rum and LOX (75.5% ethly alcohol and water). static test on 20 march 1993 shows 1600 lbs thrust.

The Dec 1994 Issues has a 1000lb thrust (lox and jet-a)and the third report on the 1600lb (1620 Lbs now) thrust engine from the Oct. issue. It further shows different test engines including a hydrogen peroxide all plastic hybrid system.

The February 1995 issue has an article called the First Amateur Space Shot done by Pacific Rocket Society using a 2000lb lox/alcohol engine.

August 94 issues talks about some old tests done in the 50's using hydrogen peroxide as well.

Sadly I lost the issues due to several moves, the articles were full of awesome photos and charts showing output. I have an index telling what articles talked about what , but the magazines are long gone...

"awseiger says he has an oxygen cylinder and kerosene in the basement", if you try to make your system using this, just remember any hydrocarbon gets in the oxygen line while it flows under pressure will cause an explosion. (work at a welding supply store and safety is a big issue).


Mike

Click to expand...

That sounds awesome! I would have loved to see them. I'll see if I can find PDF'ed copies.

And for the record, I do NOT have an Oxygen Cylinder and kerosene in the basement. I'm simply saying that these two components are very easily obtained at my local hardware store.... Juts look on youtube for the numerous people that have constructed functional Hybrid systems using nothing but plumbing parts.

mbauer said:

In the 1990's there was a magazine called High Power Rocketry The October 1994 issue has a couple of different liquid engines. Page 12 Title is HOT & Steamy about using h20 turned into steam. Page 72 has a report from Reaction Research Society using 151 rum and LOX (75.5% ethly alcohol and water). static test on 20 march 1993 shows 1600 lbs thrust.

The Dec 1994 Issues has a 1000lb thrust (lox and jet-a)and the third report on the 1600lb (1620 Lbs now) thrust engine from the Oct. issue. It further shows different test engines including a hydrogen peroxide all plastic hybrid system.

The February 1995 issue has an article called the First Amateur Space Shot done by Pacific Rocket Society using a 2000lb lox/alcohol engine.

August 94 issues talks about some old tests done in the 50's using hydrogen peroxide as well.

Sadly I lost the issues due to several moves, the articles were full of awesome photos and charts showing output. I have an index telling what articles talked about what , but the magazines are long gone...

"awseiger says he has an oxygen cylinder and kerosene in the basement", if you try to make your system using this, just remember any hydrocarbon gets in the oxygen line while it flows under pressure will cause an explosion. (work at a welding supply store and safety is a big issue).


Mike

Click to expand...

The 1994 issue is actually how I found the RRS. I still have that issue in storage someplace. The engine I flew with as shown above was a 650-700 lbf LOX/Ethanol ablative cooled engine.

Eric

awseiger said:

That sounds awesome! I would have loved to see them. I'll see if I can find PDF'ed copies.

And for the record, I do NOT have an Oxygen Cylinder and kerosene in the basement. I'm simply saying that these two components are very easily obtained at my local hardware store.... Juts look on youtube for the numerous people that have constructed functional Hybrid systems using nothing but plumbing parts.

Click to expand...

You'd be amazed at what you can do with a a teflon seated brass ball vale bought at your local hardware store. When working with LOX you need to modify any ball valves and drill a vent port into the ball. If you don't the trapped liquid inside the ball cavity will blow the seat out of the valve when its c. The only lubricant that gets near LOX was krytox. You have to be judicial on keeping everything bagged and clean when working with liquid oxygen.

Eric

Sorry, but there are a lot of incorrect postings in reply to this thread.

1. I am not sure you will ever get a local section to allow you to launch a liquid, even if you have tons of successful test data and safety procedures. The reason is people are scared of what they don't know and (most) hobby guys don' know liquids. If you are serious about doing a liquid project just assme you are on your own for finding a safe LEGAL test site and flight location.

2. Liquids don't really have to be that complex. I designed three different small liquid rockets in college with highest thrust being 1000 lb. In reality hybrid rockets are extremely more complex than liquids when it comes to the science and designing one that performs how you want it to. Desiging a liquid rocket can be difficult but the methods are well doumented. Fuels don't have to be extremely dangerous or toxic. One rocket I designed used propane and nitrous oxide and another used alcohol. You don't need a turbopump for a low thrust rockets, since the mass flow is low. You can instead operate like a hybrid, using a pressurant in a blow down arrangement.

3. I don't recommend ANYONE try to build any kind of rocket engine (solid, liquid, or hybrid) unless you have an aerospace engineering degree and expeience designing mechanical systems and developing test procedures and safety protocols. You really need to be careful, not just for your safety but for legal reasons as well. Solids can go just as wrong as liquids, sometimes worse. I understand the attraction to design your own, because I've done it, but it is not something to be taken lightly.


My background: Rocket enthusiast, BS aerospace engineering, former ATK rocket design engineer, current aviation design engineer, MS aerospace engineering (coming soon ), designed built and flew solids liquids and hybrids

Liquids fall outside the NAR's safety regulations pertaining to using only pre-manufactured motors in accordance with the manufacturer's recommendations... being outside the safety code means any launch using a liquid motor would NOT be insured, and thus the section or landowner would be totally exposed to liability. Therefore, they WOULD NOT and WILL NOT be allowed at NAR section launches, period... (unless some manufacturer develops and certifies a liquid motor).

I doubt they'd be allowed under Tripoli rules either, though they're pretty fast and loose with their regs, especially when it comes to "research motors" or "research launches" and the like...

Liquid motors just aren't a part of hobby rocketry... more a research project...

Later! OL JR

CoyoteNumber2 said:

The R.A.T.T. Works K350 Tribrid (ABS/ethanol/nitrous) has been certified for quite a few years now.

https://www.thrustcurve.org/motorsearch.jsp?id=907

Click to expand...

That may be, but a tribrid is not a pure liquid engine, either...

later! OL JR

Since this thread still has some legs I thought I'd toss in the only video I've been able to find of my launch. The beginning has some footage of the ground support stuff, He fill/disconnect system. Video quality is fairly low.

[VIMEO]54742023[/VIMEO]



Eric

That is fascinating Eric. The amount of work you put into the project must have been phenomenal. Do you have any stats regarding the overall performance of the motor (thrust, classification, etc)?

Great work!

MarkII said:

It's a reaction mass but I think it would be a stretch to call it rocket fuel.

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Don't go saying that to Air Command - https://www.aircommandrockets.com/

Krusty

SSenesy said:

That is fascinating Eric. The amount of work you put into the project must have been phenomenal. Do you have any stats regarding the overall performance of the motor (thrust, classification, etc)?

Great work!

Click to expand...

It was about 5 years of work. Probably the most rewarding project I've done. The initial engine design, ground support equipment, electronics etc was about three years of work. The flight vehicle was another two. None of it would be possible without the support the RRS provided. I probably asked a thousand questions to Tom Mueller, Dave Crisalli, and the others guys there. The vehicle is pneumatically controlled so I needed a GSE system which was computer controlled. I designed that from scratch. A 6000psi He tank feeds a 3K-4K regulator that then is dropped down by an internal regulator to run valves and vents. All the tanks where instrumented so from the blockhouse I could check pressures. The pneumatic design I came up with worked really well and moved several valves and associated plumbing out to the ground support equipment and simplified the flight vehicle. You have to be able to vent tanks remotely, fill remotely, etc. Once the on board He tank is pressurized the system closes the loop internally and can operate in that mode until the He tank pressure drops below a certain pressure. At that point the vent valves open up automatically and the vehicle depressurizes. This way the flight vehicle is totally depressurized and vent safe after the flight,, or remotely safed on the stand if needed.

Below are the basic engine parameters. The engine has a fairly large margin of safety. Increase the tank pressures and you can push up the thrust and ISP. The engine was designed for 650lbf and the flight vehicle was set to run around 700lbf. Tank size would allow about 13 seconds of run time with a fuel rich shutdown. The flight was a little shorter due to a delay which allowed about 2 seconds of LOX to boil off prior to launch.



Here is the main GSE helium distribution box.



Here is the upper section of the vehicle. High pressure He distribution etc.



Here is the vehicle being prepared for loading LOX into the tank.





Eric

Eric

Thanks for your contribution to this thread.