The "Real Aerospace" Thread

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Mjolnir
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Re: The "Real Aerospace" Thread

Post by Mjolnir »

Arioch wrote:
Mjolnir wrote:SpaceX is getting a bit more aggressive with their first stage recovery maneuvers, with less waiting around in case something's gone wrong. With their latest launch, the first stage pitched back and did the boostback burn just seconds after separation, while still inside the second stage's exhaust plume. The interaction of their exhausts, two 3 km/s streams of rarefied gases colliding head on, produced this sight:
https://scontent-vie1-1.xx.fbcdn.net/t3 ... 7982_o.jpg
It also produced an interesting trail:
http://apod.nasa.gov/apod/ap160721.html

They could try this on this particular flight (I assume) because it was an ISS supply mission, which is in a very low orbit.
Yeah, ISS Dragon missions now have lots of margin. Other LEO missions also allow RTLS...their first return to land was on a launch of Orbcomm satellites (flight 20). It would have to be a very small satellite to allow it after a geosynchronous launch, so that's probably not going to happen.

Most or all Falcon Heavy flights will have the side boosters RTLS, though. That'll involve two boosters doing boostback burns while center core is doing a full 9-engine burn...that should be interesting to see. It sounds like the first flight will bring the center core back to land as well (they're building two additional landing pads for the Heavy), but I don't know how common that'll be.

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Re: The "Real Aerospace" Thread

Post by icekatze »

hi hi

So it seems like another round of bad quantum mechanics news is making headlines, and I'm struggling to make sense of what is actually going on. The only information I could find that wasn't trying to sensationalize the story was from NASAspaceflight. (edit)

Long March 2D launches world’s first quantum communications satellite

Anyone else have an idea of how this is supposed to work? Are they sending a series of random positions and using it as a one time pad, perhaps? A number of stories at other news sources were reporting that it would allow FTL communication of information, but I have trouble believing that China's quantum scientists have never heard of Bell's Inequality.
Last edited by icekatze on Tue Aug 16, 2016 6:36 pm, edited 1 time in total.

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Durabys
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Re: The "Real Aerospace" Thread

Post by Durabys »

icekatze wrote:hi hi

So it seems like another round of bad quantum mechanics news is making headlines, and I'm struggling to make sense of what is actually going on. The only information I could find that wasn't trying to sensationalize the story was from NASA.

Long March 2D launches world’s first quantum communications satellite

Anyone else have an idea of how this is supposed to work? Are they sending a series of random positions and using it as a one time pad, perhaps? A number of stories at other news sources were reporting that it would allow FTL communication of information, but I have trouble believing that China's quantum scientists have never heard of Bell's Inequality.
Your's is a stupid post. A Quantum Satellite does this:
https://www.theguardian.com/world/2016/ ... unications

China says it has launched the world’s first quantum satellite, a project Beijing hopes will enable it to build a coveted “hack-proof” communications system with potentially significant military and commercial applications.

Xinhua, Beijing’s official news service, said Micius, a 600kg satellite that is nicknamed after an ancient Chinese philosopher, “roared into the dark sky” over the Gobi desert at 1.40am local time on Tuesday, carried by a Long March-2D rocket.

“The satellite’s two-year mission will be to develop ‘hack-proof’ quantum communications, allowing users to send messages securely and at speeds faster than light,” Xinhua reported.

The Quantum Experiments at Space Scale, or Quess, satellite programme is part of an ambitious space programme that has accelerated since Xi Jinping became Communist party chief in late 2012.

“There’s been a race to produce a quantum satellite, and it is very likely that China is going to win that race,” Nicolas Gisin, a professor and quantum physicist at the University of Geneva, told the Wall Street Journal. “It shows again China’s ability to commit to large and ambitious projects and to realise them.”

The satellite will be tasked with sending secure messages between Beijing and Urumqi, the capital of Xinjiang, a sprawling region of deserts and snow-capped mountains in China’s extreme west.

Highly complex attempts to build such a “hack-proof” communications network are based on the scientific principle of entanglement.
Chinese satellite will test 'spooky' Einstein claim
Read more

According to this theory, two particles become “entangled” when they interact. However, any subsequent interaction impacts on both particles. “It is hence impossible to wiretap, intercept or crack the information transmitted through it,” Xinhua reported after Tuesday’s launch.

Speaking to Nature magazine earlier this year, the Chinese physicist in charge of the project, Pan Jianwei, said the launch would push the boundaries of scientific knowledge. “[But] if you want to explore new physics, you must push the limit.”

“I think China has an obligation not just to do something for ourselves – many other countries have been to the moon, have done manned spaceflight – but to explore something unknown,” added Pan, from the Chinese Academy of Sciences.

After Tuesday’s launch Pan told Xinhua the mission marked “a transition in China’s role ... from a follower in classic information technology (IT) development to one of the leaders guiding future IT achievements”.

Beijing’s official news agency said there were “enormous prospects” for the use of such technology in fields including defence, military and finance.
AKA: Un-Hackable Communication. Basically One-Time Pads..in other words: nothing can ever decrypt those messages. Not even Umiak/Historian/Soia Magic Hacking would work on this. You would need Loroi telepaths peeking into the brains of the reader/writer of such an encrypted message to get the info out. Or the Soai pulling out Time Travel machines and use those to create an infinite computing speed computer and use that to decrypt it. But basically ANY method of hacking or decrypting is fucked forever.
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Arioch
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Re: The "Real Aerospace" Thread

Post by Arioch »

As I understand it, they're trying to use quantum entanglement for encryption (and to detect attempts to break this encryption). Slightly better article at Popular Science:

http://www.popsci.com/chinas-quantum-sa ... hy-forever

(By the way, NASASpaceFlight.com is not affiliated with NASA.)

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Re: The "Real Aerospace" Thread

Post by icekatze »

hi hi
Durabys wrote:Your's is a stupid post.
Wow, ad hominem, classy.

And in any case, the Guardian article still doesn't explain how they are using quantum mechanics to make hack proof communications. Also, the part where they say "allowing users to send messages securely and at speeds faster than light," is false. Information sent via quantum entanglement is always, always random. (Again, see Bell's Inequality.)

(also also, corrected my mistake on NASAspaceflight. I'll try not to make the same mistake again.)

That Popular Science article was indeed pretty helpful, thanks Arioch. :)

As far as I'm able to determine, yeah, they're using quantum entanglement to deliver a random encryption key, and then using that random encryption key to send the message through more conventional means. But I'm not sure how they're going to use quantum mechanics to tell if someone is trying to eavesdrop. I would think that capability would be a liability, if someone is actively trying to jam your communications.

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Re: The "Real Aerospace" Thread

Post by Arioch »

icekatze wrote:
Durabys wrote:Your's is a stupid post.
Wow, ad hominem, classy.
I think he was referring to the NASASpaceFlight.com article rather than your post.

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Mjolnir
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Re: The "Real Aerospace" Thread

Post by Mjolnir »

icekatze wrote:hi hi
Durabys wrote:Your's is a stupid post.
Wow, ad hominem, classy.

And in any case, the Guardian article still doesn't explain how they are using quantum mechanics to make hack proof communications. Also, the part where they say "allowing users to send messages securely and at speeds faster than light," is false. Information sent via quantum entanglement is always, always random. (Again, see Bell's Inequality.)

(also also, corrected my mistake on NASAspaceflight. I'll try not to make the same mistake again.)

That Popular Science article was indeed pretty helpful, thanks Arioch. :)

As far as I'm able to determine, yeah, they're using quantum entanglement to deliver a random encryption key, and then using that random encryption key to send the message through more conventional means. But I'm not sure how they're going to use quantum mechanics to tell if someone is trying to eavesdrop. I would think that capability would be a liability, if someone is actively trying to jam your communications.
Yes, it's basically exploiting quantum behavior to securely generate a shared encryption key. And jamming is detectable, the point is to prevent a third party from snooping without detection. Some things are better off not communicated immediately if they can't be communicated securely, and the sooner you know of a snooping device, the sooner you can do something about it.

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Re: The "Real Aerospace" Thread

Post by Absalom »

Mjolnir wrote:
icekatze wrote:As far as I'm able to determine, yeah, they're using quantum entanglement to deliver a random encryption key, and then using that random encryption key to send the message through more conventional means. But I'm not sure how they're going to use quantum mechanics to tell if someone is trying to eavesdrop. I would think that capability would be a liability, if someone is actively trying to jam your communications.
Yes, it's basically exploiting quantum behavior to securely generate a shared encryption key. And jamming is detectable, the point is to prevent a third party from snooping without detection. Some things are better off not communicated immediately if they can't be communicated securely, and the sooner you know of a snooping device, the sooner you can do something about it.
Not entirely clear how one-time pads are going to enable detection of snooping. If this would help at all with that, then it means that sufficiently secure yet still deterministic encryption should be able to do the same. Detecting snooping doesn't really depend on good encryption, but instead on behavioral analysis. If they could determine that the wave-function had been forcible collapsed early, sure, or if they were using paired-particles-per-bit signalling and there was a discrepancy, sure, but the first is going to qualify as a limited form of FTL, and the later is unlikely to be realistic for satellite communications.

So, how can the snoop-detect really work? I can't think of anything that doesn't run into "and then a bird accidentally coupled with the signal enough to render the wave-fuction non-matching, forcing a launch to reset the entire system". Settling for really good distant-yet-synchronized encryption strikes me as the real net win, not snoop-detection.

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Re: The "Real Aerospace" Thread

Post by Mjolnir »

Absalom wrote:
Mjolnir wrote:
icekatze wrote:As far as I'm able to determine, yeah, they're using quantum entanglement to deliver a random encryption key, and then using that random encryption key to send the message through more conventional means. But I'm not sure how they're going to use quantum mechanics to tell if someone is trying to eavesdrop. I would think that capability would be a liability, if someone is actively trying to jam your communications.
Yes, it's basically exploiting quantum behavior to securely generate a shared encryption key. And jamming is detectable, the point is to prevent a third party from snooping without detection. Some things are better off not communicated immediately if they can't be communicated securely, and the sooner you know of a snooping device, the sooner you can do something about it.
Not entirely clear how one-time pads are going to enable detection of snooping. If this would help at all with that, then it means that sufficiently secure yet still deterministic encryption should be able to do the same. Detecting snooping doesn't really depend on good encryption, but instead on behavioral analysis. If they could determine that the wave-function had been forcible collapsed early, sure, or if they were using paired-particles-per-bit signalling and there was a discrepancy, sure, but the first is going to qualify as a limited form of FTL, and the later is unlikely to be realistic for satellite communications.

So, how can the snoop-detect really work? I can't think of anything that doesn't run into "and then a bird accidentally coupled with the signal enough to render the wave-fuction non-matching, forcing a launch to reset the entire system". Settling for really good distant-yet-synchronized encryption strikes me as the real net win, not snoop-detection.
It's not just a one-time pad, it's not FTL, it's not some pre-synchronized system, and no amount of encryption can make it possible, no matter how sufficiently advanced. The information required to decrypt the message is only made available to two parties, due to fundamental physical limits. If someone's snooping enough to read the message, the message is unreadable by the intended recipient, which can be detected immediately and dealt with without waiting for the adversary to change their behavior based on things they shouldn't know...which is rather too late.

As for "unlikely to be feasible", it certainly isn't easy, and it hasn't been proven to be robust enough to be feasible in real-world conditions. That's why they're messing with a single experimental satellite, not deploying a global secure communications network.

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Re: The "Real Aerospace" Thread

Post by Suederwind »

I just read an article about this study in German and thought it might be of interest: Link

Its about the effects of cosmic radiation on neurons, memories and the brain of mammals. A very uncomfortable read or in other words: I wouldn't book a trip to Mars just yet.
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Re: The "Real Aerospace" Thread

Post by icekatze »

hi hi

I read a little bit about that study in passing the other day. I remember also reading about how people going to the moon had to put up with cosmic rays, occasionally creating flashes in their eyes while they were trying to sleep.

And then there's cases of people like Edgar Mitchell who, while still a generally decent human being, did apparently go a little wacky while he was coming back from the moon on Apollo 14. Universal consciousness and all.

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Re: The "Real Aerospace" Thread

Post by Mr Bojangles »

Are we sure Edgar wasn't a bit wacky before cosmic rays smacked into his brain matter? I'd heard about his... transcendental(?)... experience during the Apollo 14 mission, but hadn't realized he'd also conducted a "psychic communication" experiment attempting to transmit info to people on Earth from the command module. His Wikipedia article makes for some interesting reading.

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Re: The "Real Aerospace" Thread

Post by Absalom »

And this is why we want humanoid robots+waldos, and enough radiation shielding to counter the problem while inside the vehicle. Nothing else fixes a problem like actually fixing the problem.

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Re: The "Real Aerospace" Thread

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Actually fixing the problem? That's just crazy talk!

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Re: The "Real Aerospace" Thread

Post by ShadowDragon8685 »

Speaking of radiation in space, bearing in mind I'm hugely nerding out here, I'm trying to figure out how many rads/sieverts someone fighting basically nude at the altitude of geostationary orbit would take over the course of an ~5-10 sword fight. I haven't been able to find a good answer with the aid of the Google, though I think my Google-Fu is failing me in this instance.

Anyone have any insight?

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Re: The "Real Aerospace" Thread

Post by icekatze »

hi hi

While I couldn't find results for something that was completely unshielded, I did find a study where one of the radiation sensors was covered only by 1.89mm of aluminum. The yearly average was about 4.8 rads per hour, but it varied greatly depending on solar activity. In periods of low activity, you might get 10 rads a day. In periods of high activity, you might get 12,000 rads in a day.

The extrapolated dose for a dosimeter without any shielding, however, was something crazy like 5700 rads per hour.

* 0mm of shielding was about 1.5E+7 rads per year
* 1mm of shielding was about 1.0E+6 rads per year
* 2mm of shielding was about 1.0E+5 rads per year
* 3 or 4mm of shielding was about 1.0E+4 rads per year (differing results between studies.)
* 5 or 7mm of shielding was about 1.0E+3 rads per year (differing results between studies.)

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Re: The "Real Aerospace" Thread

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ShadowDragon8685 wrote:Speaking of radiation in space, bearing in mind I'm hugely nerding out here, I'm trying to figure out how many rads/sieverts someone fighting basically nude at the altitude of geostationary orbit would take over the course of an ~5-10 sword fight. I haven't been able to find a good answer with the aid of the Google, though I think my Google-Fu is failing me in this instance.

Anyone have any insight?
I think it would be highly variable, depending primarily on whether the orbit carried the subject through the Van Allen belts, and what the solar activity was like at the time. The outer Van Allen belt extends to ~60,000 km, so a geostationary orbit at ~42,000 km could certainly pass through parts of it.

There's a page here which discusses the doses that the Apollo astronauts would have been exposed to, which skirted the edges of the Van Allen belt both to and from the Moon. The conclusion is that total exposure (ignoring shielding) from the belts for the entire mission was something like 180 rads.

Unless you were right in the heart of the radiation belt, or solar activity was very high, I don't think 10 minutes of exposure to normal interplanetary radiation levels would present an extraordinary risk.

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Re: The "Real Aerospace" Thread

Post by Mr Bojangles »

ShadowDragon8685 wrote:Speaking of radiation in space, bearing in mind I'm hugely nerding out here, I'm trying to figure out how many rads/sieverts someone fighting basically nude at the altitude of geostationary orbit would take over the course of an ~5-10 sword fight. I haven't been able to find a good answer with the aid of the Google, though I think my Google-Fu is failing me in this instance.

Anyone have any insight?
I couldn't find anything informative that wasn't behind a paywall, but the Wikipedia article about the Van Allen radiation belts had a section about the implications for space travel. But, it suggests that if you were to spend 5 to 10 minutes unshielded in the belts you wouldn't be fatally irradiated (I'm assuming you mean minutes; you didn't have any time units). If the sun is in a period of high activity and you're at the edges of the magnetosphere, you are likely to be all kinds of boned.

Icekatze's info seems to bear this out. Suffice it to say, don't find naked in a radiation zone. Even if you win, you lose.

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Re: The "Real Aerospace" Thread

Post by icekatze »

hi hi

I know people were talking about the Zumwalt at length in another thread, so I think someone around here will find this interesting. Also possibly has general aerospace implications, in terms of other mass driver ideas out there.

USS Zumwalt can't fire its guns because the ammo is too expensive.

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Re: The "Real Aerospace" Thread

Post by ShadowDragon8685 »

icekatze wrote:hi hi

I know people were talking about the Zumwalt at length in another thread, so I think someone around here will find this interesting. Also possibly has general aerospace implications, in terms of other mass driver ideas out there.

USS Zumwalt can't fire its guns because the ammo is too expensive.
Ahhhh... The classic derptard effect with military procurement.
There's a major disconnect between congress and defense contractors, which is surprising since they're in bed so often.

<X> develops <Weapon Y> and expects to sell <Z> units at price <A>/unit.
Congress thinks "That's too much money," and decides to only procure <F> units at price <A>/unit. But that is not what's going on at <X>.

<X> plans to make <Z * A> money. When Congress cuts <Z> to <F>, <X> still wants to make <Z * A> profit, so the price of <Weapon Y> goes waaaaay the fuck up to <Q>, such that <F * Q> = <Z * A>.


And then Congress shits a brick and says "WTF?! This costs way too much! We're not buying any!" leaving them without the weapons they wanted and having sunk all the costs into R&D which have already been paid. Meanwhile, <X> are fuming that they've basically spun their wheels, and jack up the R&D price on the next weapon system they develop for Congress so they can be reasonably sure they're going to make SOME money the next time this fiasco comes around.

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