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The "Real Aerospace" Thread 
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Post Re: The "Real Aerospace" Thread
GeoModder wrote:
Arioch wrote:
Even bombers and cruise missiles eventually crash in your own territory.

Or submarines sink in your own territorial (littoral) waters.

Ships can sink without breaching their reactors. When aircraft crash, it's a different matter.

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Sat Apr 13, 2019 11:19 am
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Post Re: The "Real Aerospace" Thread
Not the case in littoral waters of course, but couldn't a submarine nuclear reactor implode when the water pressure gets high enough?

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Sat Apr 13, 2019 2:58 pm
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Post Re: The "Real Aerospace" Thread
hi hi

It's hard to say what would happen at the bottom of the Mariana Trench, but nuclear submarine losses in the Atlantic show that their nuclear components are reasonably stable. This isn't surprising since they are not pressurized with air, and any impact with the ocean floor is going to be slow and soft.

K-219 sank at a depth of 6,000 meters in the Hatteras Abyssal Plain and didn't suffer a leak in its reactor or missiles.

The USS Scorpion imploded at around 470 meters, tearing the vessel apart into multiple segments, and sank to the seabed at around 3,000 meters. Its fuel casing and nuclear tipped torpedoes showed no signs of leakage.


Sat Apr 13, 2019 3:19 pm
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Post Re: The "Real Aerospace" Thread
People seem to forget that water is the best radiation shield in terms of density and availability while water is the de facto shield of neutron radiation since stray neutrons are rendered harmless by Hydrogen (H20 and all that :P).

Better explanation than I can manage can be found here: https://www.reddit.com/r/askscience/com ... on_shield/

EDIT: In short, if you have something that leaks radiation you have no better place to dump it than the bottom of the ocean.

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Sun Apr 14, 2019 3:52 am
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Post Re: The "Real Aerospace" Thread
dragoongfa wrote:

EDIT: In short, if you have something that leaks radiation you have no better place to dump it than the bottom of the ocean.


'points towards above Europa mission' Exactly. Use the reactor to melt your way through the ice, while bathing the trailing submersible in hard gamma (it's trailing close behind so no significant water volume in front of it). Then once the reactor finishes digging, let it drop into the ocean bottom (100 km). It's a big piece of metal, so no significant stress from water pressure, and you can build it to use most of it's criticality while in the melting phase, so it can't carry on producing heat for a long time after finishing. Bonus points if it's a pebble bed reactor using passive circulation. Release the pebbles once the melting phase is over, and watch them become subcritical almost instantly due to not being in close proximity to one another.


Sun Apr 14, 2019 12:26 pm
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Post Re: The "Real Aerospace" Thread
IF here's life in Europa's oceans, we can assume it going all the way to the bottom of the ocean, as light will be no factor in the lifeforms swimming in the upper layers of the ocean...
Such a reactor willinfluence local life. Likely even positively, as a source of heat and warmth.
Just hope that the rockets launching that reactor start all right and have no failure....

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Mon Apr 15, 2019 12:49 am
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Post Re: The "Real Aerospace" Thread
Krulle wrote:
IF here's life in Europa's oceans, we can assume it going all the way to the bottom of the ocean, as light will be no factor in the lifeforms swimming in the upper layers of the ocean...
Such a reactor willinfluence local life. Likely even positively, as a source of heat and warmth.
Just hope that the rockets launching that reactor start all right and have no failure....


If there's life in Europa's ocean, its more likely to be found on the bottom. More chance for volcanic/tidal fissures there, and less chance for exposure to Jupiter's radiation belts.

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Post Re: The "Real Aerospace" Thread
GeoModder wrote:
Krulle wrote:
IF here's life in Europa's oceans, we can assume it going all the way to the bottom of the ocean, as light will be no factor in the lifeforms swimming in the upper layers of the ocean...
Such a reactor willinfluence local life. Likely even positively, as a source of heat and warmth.
Just hope that the rockets launching that reactor start all right and have no failure....


If there's life in Europa's ocean, its more likely to be found on the bottom. More chance for volcanic/tidal fissures there, and less chance for exposure to Jupiter's radiation belts.


Jupiter's radiation belts will quickly fry anything on the surface, but 100 km of ice is going to block essentially all of it. I wouldn't be surprised if ambient radiation under the surface ice is lower than on the surface of any solid body in the solar system, and mostly due to radioactive materials dissolved in the water.

But yes, the main sources for energy are likely to be volcanic activity at the ocean floor. Convection of ice that has concentrated minerals and organic materials might support some life at the top of the water column though. It may even result in subduction of significant amounts of free oxygen (split from the water by sunlight and Jupiter's radiation).


Mon Apr 15, 2019 6:00 am
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Post Re: The "Real Aerospace" Thread
Even with 0.1G, i think that pressure in this ocean will be insane.


Mon Apr 15, 2019 6:32 am
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Post Re: The "Real Aerospace" Thread
By my (rough) calculations about equivalent to 20 km on Earth, or twice the pressure found in the Challenger Deep. High as hell, but doable. Might wanna watch what instruments you put on the thing, though.


Mon Apr 15, 2019 1:38 pm
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Post Re: The "Real Aerospace" Thread
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


Thu Apr 18, 2019 6:02 pm
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Post Re: The "Real Aerospace" Thread
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.)


Thu Apr 18, 2019 9:47 pm
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Post Re: The "Real Aerospace" Thread
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.


Fri Apr 19, 2019 2:31 am
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Post Re: The "Real Aerospace" Thread
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.


Fri Apr 19, 2019 6:46 pm
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Post Re: The "Real Aerospace" Thread
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.


Sat Apr 20, 2019 4:11 am
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Post Re: The "Real Aerospace" Thread
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:
Quote:
“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.


Sat Apr 20, 2019 4:47 am
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Post Re: The "Real Aerospace" Thread
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...


Sat Apr 20, 2019 6:31 am
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Post Re: The "Real Aerospace" Thread
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!


Wed Apr 24, 2019 9:21 am
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Post Re: The "Real Aerospace" Thread
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.

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Post Re: The "Real Aerospace" Thread
I for one wouldn't like to be on line-of-sight of such a transmission! ;)

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