The "Real Aerospace" Thread

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Mjolnir
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Re: The "Real Aerospace" Thread

Post by Mjolnir »

On the 7th, Intelsat 29e developed a fuel leak and comms problems. On the 8th it was drifting from its orbital slot and pieces of debris were visible.
On the 11th: https://www.youtube.com/watch?v=aqPrVn71IqY

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Re: The "Real Aerospace" Thread

Post by icekatze »

hi hi

Geeze. I wonder what caused the incident. Debris, micro meteor, something else?

A lot of people don't seem to think that space debris is currently a problem, or are actively ignoring the problem. (I was in a conversation with someone recently about space stuff and I tried to quote Kessler's work, and they just shut down the conversation as though I was raving mad for even suggesting it.)

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Re: The "Real Aerospace" Thread

Post by Absalom »

Mr.Tucker wrote:So, I've just had a reeeeally crazy idea I've been mulling over for about two weeks, and I'd like to pass it by here.

Firstly, I started from the concept of the Nuclear Thermal Turbo rocket, an idea for a Air Augmented Nuclear Thermal Rocket, that uses air-breathing propulsion to lofts itself out of the lower atmosphere, transitioning from a ramjet type of system (powered by a turbofan spun by gasses leached from the reactor chamber), then to a scramjet (using the air directly by heating, and leaving the fanblades at idle angles of attack), then finally using standard NTR-type propulsion for the final ascent and orbital circularisation.
Mr.Tucker wrote:But... then I realised that, since I already have a nuclear reactor onboard, how about going even more speculative...and mate it to this:
Bit late, but I've been thinking, and...

Why does the reactor even need to be on your atmospheric vehicle? Why not just use rectennas to receive power from an orbiting source (now THAT you might want to be nuclear), which you then use to drive rotors for the lower atmospheric portion of the trip? You get some (or perhaps even most) of the benefit for a reduced chance of nuclear incidents, hopefully lower engine mass, etc. If you feel like being thorough, maybe you use either a second frequency or frequency conversion to implement a microwave version of a Lightcraft engine for high altitudes, presumably with a magnetic nozzle. If you feel really really thorough, maybe you even try to implement an externally pumped VASIMR for that last push into orbital. Regardless, rectenna-powered rotors/fans + rockets strike me as a good first-glance alternative to actually dragging the reactor around every time you want to go somewhere.

Especially if you'll be doing in-atmosphere hops at all.

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Mjolnir
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Re: The "Real Aerospace" Thread

Post by Mjolnir »

Absalom wrote:
Mr.Tucker wrote:So, I've just had a reeeeally crazy idea I've been mulling over for about two weeks, and I'd like to pass it by here.

Firstly, I started from the concept of the Nuclear Thermal Turbo rocket, an idea for a Air Augmented Nuclear Thermal Rocket, that uses air-breathing propulsion to lofts itself out of the lower atmosphere, transitioning from a ramjet type of system (powered by a turbofan spun by gasses leached from the reactor chamber), then to a scramjet (using the air directly by heating, and leaving the fanblades at idle angles of attack), then finally using standard NTR-type propulsion for the final ascent and orbital circularisation.
Mr.Tucker wrote:But... then I realised that, since I already have a nuclear reactor onboard, how about going even more speculative...and mate it to this:
Bit late, but I've been thinking, and...

Why does the reactor even need to be on your atmospheric vehicle? Why not just use rectennas to receive power from an orbiting source (now THAT you might want to be nuclear), which you then use to drive rotors for the lower atmospheric portion of the trip? You get some (or perhaps even most) of the benefit for a reduced chance of nuclear incidents, hopefully lower engine mass, etc. If you feel like being thorough, maybe you use either a second frequency or frequency conversion to implement a microwave version of a Lightcraft engine for high altitudes, presumably with a magnetic nozzle. If you feel really really thorough, maybe you even try to implement an externally pumped VASIMR for that last push into orbital. Regardless, rectenna-powered rotors/fans + rockets strike me as a good first-glance alternative to actually dragging the reactor around every time you want to go somewhere.

Especially if you'll be doing in-atmosphere hops at all.
You're talking about funneling gigawatts through your rectennas and power system before reaching whatever you're using for propulsion, with some significant fraction being lost to heat at each step. Any failure will result in your craft doing a fair imitation of a moth hitting a bug zapper. Reduced mass seems unlikely.

Lightcraft rely on direct heating of the working fluid by the beam. The vehicle itself doesn't need to handle that power directly. A beam powered electric propulsion system might make sense in orbit, where you can spread huge rectenna arrays and can work with far less thrust, allowing much lower power densities, but it seems unlikely to propel a spacecraft at the multiple gravities needed to launch from Earth.

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Re: The "Real Aerospace" Thread

Post by Absalom »

Mjolnir wrote:
Absalom wrote:
Mr.Tucker wrote:So, I've just had a reeeeally crazy idea I've been mulling over for about two weeks, and I'd like to pass it by here.

Firstly, I started from the concept of the Nuclear Thermal Turbo rocket, an idea for a Air Augmented Nuclear Thermal Rocket, that uses air-breathing propulsion to lofts itself out of the lower atmosphere, transitioning from a ramjet type of system (powered by a turbofan spun by gasses leached from the reactor chamber), then to a scramjet (using the air directly by heating, and leaving the fanblades at idle angles of attack), then finally using standard NTR-type propulsion for the final ascent and orbital circularisation.
Mr.Tucker wrote:But... then I realised that, since I already have a nuclear reactor onboard, how about going even more speculative...and mate it to this:
Bit late, but I've been thinking, and...

Why does the reactor even need to be on your atmospheric vehicle? Why not just use rectennas to receive power from an orbiting source (now THAT you might want to be nuclear), which you then use to drive rotors for the lower atmospheric portion of the trip? You get some (or perhaps even most) of the benefit for a reduced chance of nuclear incidents, hopefully lower engine mass, etc. If you feel like being thorough, maybe you use either a second frequency or frequency conversion to implement a microwave version of a Lightcraft engine for high altitudes, presumably with a magnetic nozzle. If you feel really really thorough, maybe you even try to implement an externally pumped VASIMR for that last push into orbital. Regardless, rectenna-powered rotors/fans + rockets strike me as a good first-glance alternative to actually dragging the reactor around every time you want to go somewhere.

Especially if you'll be doing in-atmosphere hops at all.
You're talking about funneling gigawatts through your rectennas and power system before reaching whatever you're using for propulsion, with some significant fraction being lost to heat at each step. Any failure will result in your craft doing a fair imitation of a moth hitting a bug zapper. Reduced mass seems unlikely.
Can I trust that you're not talking about the rotor stage? Quadcopters show well enough that the rotor stage shouldn't be a major design issue, maybe even without dedicated radiators. As far as frequency conversion, I do question the heat load of that myself. The only reason it even comes to mind is that I'm uncertain about the ability to switch to microwave-frequency lightcraft operation before electric rotorcraft operation becomes ineffective.
Mjolnir wrote:Lightcraft rely on direct heating of the working fluid by the beam. The vehicle itself doesn't need to handle that power directly. A beam powered electric propulsion system might make sense in orbit, where you can spread huge rectenna arrays and can work with far less thrust, allowing much lower power densities, but it seems unlikely to propel a spacecraft at the multiple gravities needed to launch from Earth.
I am aware of how lightcraft work, yes. Mostly I'm uncertain about whether it would be practical to use microwave frequencies effectively in the lower atmosphere. It appears that the related microwave frequency research has been on thermal rockets instead of lightcraft.

Though, supposing that you can get the correct frequency to the atmospheric craft from an orbital source in the first place, I am curious as to whether this would be enough to adapt VASIMR to an upper-atmosphere air-breather, with only the ionization & confinement provided in the engine (and maybe not the ionization). Not that I've worked out how much energy might be spent on even just confinement for useful thrusts in the upper atmosphere.

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Re: The "Real Aerospace" Thread

Post by Zarya »

icekatze wrote:Geeze. I wonder what caused the incident. Debris, micro meteor, something else?
It’s plausible Intelsat 29e was hit by debris. I don’t think Boeing delivered a faulty product.
It happened with other active GEO satellites too: AMC-9, Telkom-1, AMOS-5, Eutelsat-33B, EchoStar-3...

Quoting @TSKelso on Twitter:
“If we add objects that pass in & out of GPZ, that brings the total to 1,616 objects, with 541 active satellites, 380 dead ones, 390 rocket bodies, 289 pieces of other debris, & 17 analyst satellites. Search for SL-12 R/Bs & you’ll see just part of the problem (67 are inside GPZ).”
GPZ is theoretically kept clean by anybody locating objects at orbital slots. IMO we have a serious tragedy of the commons problem here, where any GEO satellite has an increasing chance of being hit by something during its active lifetime, usually between 15-20 years.
icekatze wrote:A lot of people don't seem to think that space debris is currently a problem, or are actively ignoring the problem. (I was in a conversation with someone recently about space stuff and I tried to quote Kessler's work, and they just shut down the conversation as though I was raving mad for even suggesting it.)
My eyes would not glaze over (in fact I’d buy you another beer) and I’d readily agree that junk in orbit (at any distance from Earth) is a tremendous problem, even if we throw more engineering at it for example by hardening spacecraft with Whipple-shields.

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Re: The "Real Aerospace" Thread

Post by Mjolnir »

Absalom wrote:
Mjolnir wrote:You're talking about funneling gigawatts through your rectennas and power system before reaching whatever you're using for propulsion, with some significant fraction being lost to heat at each step. Any failure will result in your craft doing a fair imitation of a moth hitting a bug zapper. Reduced mass seems unlikely.
Can I trust that you're not talking about the rotor stage? Quadcopters show well enough that the rotor stage shouldn't be a major design issue, maybe even without dedicated radiators. As far as frequency conversion, I do question the heat load of that myself. The only reason it even comes to mind is that I'm uncertain about the ability to switch to microwave-frequency lightcraft operation before electric rotorcraft operation becomes ineffective.
Mjolnir wrote:Lightcraft rely on direct heating of the working fluid by the beam. The vehicle itself doesn't need to handle that power directly. A beam powered electric propulsion system might make sense in orbit, where you can spread huge rectenna arrays and can work with far less thrust, allowing much lower power densities, but it seems unlikely to propel a spacecraft at the multiple gravities needed to launch from Earth.
I am aware of how lightcraft work, yes. Mostly I'm uncertain about whether it would be practical to use microwave frequencies effectively in the lower atmosphere. It appears that the related microwave frequency research has been on thermal rockets instead of lightcraft.

Though, supposing that you can get the correct frequency to the atmospheric craft from an orbital source in the first place, I am curious as to whether this would be enough to adapt VASIMR to an upper-atmosphere air-breather, with only the ionization & confinement provided in the engine (and maybe not the ionization). Not that I've worked out how much energy might be spent on even just confinement for useful thrusts in the upper atmosphere.
Rotor craft are good at hovering at low altitudes with small payloads. Launch vehicles accelerate heavy payloads at multiple gravities while traveling at supersonic speeds through high altitudes to vacuum. Rotors aren't useful here.

VASIMR doesn't have anywhere near the thrust required to climb to orbit from air-breathing speeds and altitude with reasonable power requirements. A high specific impulse engine effectively sacrifices power efficiency to improve propellant efficiency, which makes it a poor fit to an application like this where you have a high minimum required thrust. An air breathing mode with the reaction mass already moving at multiple km/s would make the power requirements even worse while making the propellant efficiency gains irrelevant.

A Merlin 1D in vacuum has a mass flow rate of 345 kg/s and an exhaust velocity of 3.05 km/s while producing 1053 kN of thrust. In terms of exhaust kinetic energy, it has a power output of 1.6 GW. Regenerative cooling and the simplicity of chemical engines mean it absorbs very little of this.

VASIMR runs at optimum efficiency (72%) with an exhaust velocity of 50 km/s. For the same thrust as the Merlin, it'd need 21 kg/s of mass flow and 26 GW, and would produce over 7 GW of waste heat, all of which has to be removed somehow. Unfortunately, this vehicle no longer has a torrent of cryogenic propellants being blasted out the back to absorb this with.

Air breathing at, say, 7 km/s means a couple hundred kilonewtons of drag just inside your engine, and power requirements to maintain the same thrust go up to around 30 GW. Worse, it wouldn't operate nearly as efficiently with air. And this is only one M1DVac's worth of thrust. And I haven't even gotten to the heating from atmospheric drag or the compressed airstream going into the engine...

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Re: The "Real Aerospace" Thread

Post by Mr.Tucker »

And wouldn't ya know it, Mr. Bucknell just published his newest iteration on the nuclear thermal turbo and associated air breathing chemical rocket:
https://www.nextbigfuture.com/2019/04/t ... s2019.html
He's also answering questions in the comments, so feel free!

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Re: The "Real Aerospace" Thread

Post by Arioch »

The May 4 Falcon 9 CRS-17 launch included an experimental module for the ISS to test X-ray communications in orbit, called XCOM.

And yes, the team is aware of the significance of the name. Check out the mission patch.

Image

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Re: The "Real Aerospace" Thread

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I for one wouldn't like to be on line-of-sight of such a transmission! ;)
Image

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Re: The "Real Aerospace" Thread

Post by Mjolnir »

https://i.imgur.com/KZZcMf7.png
https://pbs.twimg.com/media/EDAy_7sUwAAmMbl.jpg:orig

That's the first full-flow staged combustion rocket engine to reach flight worthiness, with a 300 bar chamber pressure and burning methane fuel. Easily the most advanced chemical rocket engine in existence.

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Re: The "Real Aerospace" Thread

Post by Zarya »

Mjolnir wrote: That's the first full-flow staged combustion rocket engine to reach flight worthiness, with a 300 bar chamber pressure and burning methane fuel. Easily the most advanced chemical rocket engine in existence.
Hmz, the Russian RD-170/RD-171 and derivatives like the RD-180 (ox-rich kerolox), or the Vulcain (hydrogen + lox) aren't full flow staged combustion cycle engines?

Addition: I always thought the Soviets were first (NK-15/NK-33), but it may have been the Britons

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Re: The "Real Aerospace" Thread

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Zarya wrote:
Mjolnir wrote: That's the first full-flow staged combustion rocket engine to reach flight worthiness, with a 300 bar chamber pressure and burning methane fuel. Easily the most advanced chemical rocket engine in existence.
Hmz, the Russian RD-170/RD-171 and derivatives like the RD-180 (ox-rich kerolox), or the Vulcain (hydrogen + lox) aren't full flow staged combustion cycle engines?

Addition: I always thought the Soviets were first (NK-15/NK-33), but it may have been the Britons
Nope, those are all oxygen-rich staged combustion, with most of the fuel being pumped directly into the combustion chamber by a single turbine, a small part of it being burned in a single preburner to run that turbine. A full-flow staged combustion engine has two preburner/turbine/pump sets, all the fuel going through the preburner for the fuel pump, all the oxidizer going through the one for the oxidizer pump, and both turbines exhausting into the combustion chamber. This uses both the fuel and the oxidizer as working fluid for the pumps, allowing them to run at higher pressures and lower temperatures. It should also allow for more independent control of fuel and oxidizer.

The Soviets worked on the engine cycle as the RD-270 for a time, but it was canceled before being developed into a flight-worthy engine, though they did fire experimental versions. Rocketdyne worked on a powerhead demonstrator in the early 2000s, but never even got as far as building an engine around that powerhead. The Raptor's the only FFSC engine to have ever flown.

edit: Correction, the Vulcain is actually a gas-generator engine like the Merlin. It pumps both fuel and oxidizer into the chamber with a pump driven by a turbine running from a small fraction of the propellant flow and dumping its exhaust separately. Simpler to develop but less efficient.
Last edited by Mjolnir on Thu Aug 29, 2019 11:02 pm, edited 1 time in total.

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Re: The "Real Aerospace" Thread

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Why do I get the sneaking suspicion that we'll meet aliens before we ever become an extra-solar species, and we've already met them?

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Re: The "Real Aerospace" Thread

Post by Zarya »

Mjolnir wrote:edit: Correction, the Vulcain is actually a gas-generator engine like the Merlin. It pumps both fuel and oxidizer into the chamber with a pump driven by a turbine running from a small fraction of the propellant flow and dumping its exhaust separately. Simpler to develop but less efficient.
heh - you're more than 99% right about the Vulcain, although it also re-injects the exhaust product of the pre-burner to create a 'film' inside the engine that protects the nozzle & engine bell. The original idea to create a slightly cooler chamber wall by injecting something extra, such as fuel, dates back to the A4 motor that powered the V-2 and it was also applied in the F-1 used for the Saturn V. My point: the Vulcain is not simply dumping the exhaust product of the pre-burner over the side, while not being a full-blown staged combustion either.

The Bristol Siddeley Gamma is brilliant in its own right, it applies the properties of H2O2 to achieve "staged combustion like efficiency".

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Re: The "Real Aerospace" Thread

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Zarya wrote:
Mjolnir wrote:edit: Correction, the Vulcain is actually a gas-generator engine like the Merlin. It pumps both fuel and oxidizer into the chamber with a pump driven by a turbine running from a small fraction of the propellant flow and dumping its exhaust separately. Simpler to develop but less efficient.
heh - you're more than 99% right about the Vulcain, although it also re-injects the exhaust product of the pre-burner to create a 'film' inside the engine that protects the nozzle & engine bell. The original idea to create a slightly cooler chamber wall by injecting something extra, such as fuel, dates back to the A4 motor that powered the V-2 and it was also applied in the F-1 used for the Saturn V. My point: the Vulcain is not simply dumping the exhaust product of the pre-burner over the side, while not being a full-blown staged combustion either.

The Bristol Siddeley Gamma is brilliant in its own right, it applies the properties of H2O2 to achieve "staged combustion like efficiency".
It's a pretty standard technique, the Merlin 1D Vacuum does the same, but the turbopump exhaust contributes little to thrust, it just lets you use a lighter nozzle extension. It's still a gas generator cycle, with the limitations on chamber pressure and less efficient use of reaction mass that come with it...the Vulcain only runs at 100 bar, the Merlin 1D at 97 bar. The RS-25 runs at 206 bar, RD-180 at 270 bar. The Vulcain gets a vacuum Isp of 431 s, compared to the staged combustion RS-25's 452 s. The Merlin 1D's 311 s is quite good for a kerosene burning gas generator engine, but the staged-combustion RD-180 gets 338 s.

Raptor gets 380 s with methane...near the performance of hydrogen with a far denser propellant that's a close match in physical properties to liquid oxygen.

The Gamma: that depends on how brilliant you consider using HTP to be. As far as I'm aware, the Black Arrow was the only launch system in existence to ever get to orbit using HTP as an oxidizer, which it did exactly once before being canceled. Many others have tried, with the expectation that a room temperature oxidizer would be easier to work with than cryogenic oxygen, but nobody's succeeded. Instead, the main room temperature alternative to LOX has been nitrogen tetroxide. People get misled by thinking of the heavily diluted stuff you can buy in the store, hydrogen peroxide in high concentrations is quite dangerous and difficult to handle. (Its instability is the reason the Soyuz can't stay longer at the station...the Soyuz uses it for attitude control, but it decomposes over time no matter what you do.)

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Re: The "Real Aerospace" Thread

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You're right about the Vulcain as well as about the higher chamber pressures - up until the late 1990s considered 'extreme' - for closed-cycle/staged combustion engines. Although the RD-180 is still used to launch NRO satellites and has a spotless track record, it has never been man rated, presumably because of the chamber pressures.
The Raptor and in due course the BE-4 or their successors may be among the first staged combustion engines with high chamber pressures that will ever be used for manned flights. I think they will be literally have to be tested to destruction over a lengthy period before they will be trusted.

I also feel we should be kind about the Bristol Gamma: its story started well over 60 years ago in the age of slide rulers and engineers wearing woollies on stone cold test sites, with the UK looking to develop its own launch vehicles 'on a shoestring' to develop a capability that'd perhaps allow the country to field its home-grown nuclear deterrent. For the delivery vehicle they needed a storable propellant and oxidizer and for that they went with HTP. The Royal Navy already had experience with high-test peroxide for their torpedoes - including a serious mishap with it - so at that time it was probably considered not as exotic and dangerous as nitrogen tetroxide.

Looking at the Black Arrow launches the exhaust plume is super-clean and the rocket itself is relatively small. Those are all advantages. Puck/Prospero, the satellite it launched during its very last launch, is indeed still in orbit. In short HTP and kerosine allowed for a very efficient launcher that was never adequately funded and that came too early to lift commercial payloads into orbit.

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Re: The "Real Aerospace" Thread

Post by Mjolnir »

Zarya wrote:You're right about the Vulcain as well as about the higher chamber pressures - up until the late 1990s considered 'extreme' - for closed-cycle/staged combustion engines. Although the RD-180 is still used to launch NRO satellites and has a spotless track record, it has never been man rated, presumably because of the chamber pressures.
The Raptor and in due course the BE-4 or their successors may be among the first staged combustion engines with high chamber pressures that will ever be used for manned flights. I think they will be literally have to be tested to destruction over a lengthy period before they will be trusted.

I also feel we should be kind about the Bristol Gamma: its story started well over 60 years ago in the age of slide rulers and engineers wearing woollies on stone cold test sites, with the UK looking to develop its own launch vehicles 'on a shoestring' to develop a capability that'd perhaps allow the country to field its home-grown nuclear deterrent. For the delivery vehicle they needed a storable propellant and oxidizer and for that they went with HTP. The Royal Navy already had experience with high-test peroxide for their torpedoes - including a serious mishap with it - so at that time it was probably considered not as exotic and dangerous as nitrogen tetroxide.

Looking at the Black Arrow launches the exhaust plume is super-clean and the rocket itself is relatively small. Those are all advantages. Puck/Prospero, the satellite it launched during its very last launch, is indeed still in orbit. In short HTP and kerosine allowed for a very efficient launcher that was never adequately funded and that came too early to lift commercial payloads into orbit.
The BE-4 actually has a weirdly low chamber pressure. Only 134 bar, more in line with a high-end gas generator engine than a staged combustion engine. It's their first large engine, so perhaps they're just being very cautious with its design. (Though they've also had problems bringing it up to full thrust, so maybe there's other issues.)

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Re: The "Real Aerospace" Thread

Post by White »

The Starship SN5 hopped succesfully.

Scott Manley has a video on it.



Also, SpaceX released some footage.


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Re: The "Real Aerospace" Thread

Post by Arioch »

Flying silos! It must be tornado season in Nebraska!

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