As was foretold, we've added advertisements to the forums! If you have questions, or if you encounter any bugs, please visit this thread: https://forums.penny-arcade.com/discussion/240191/forum-advertisement-faq-and-reports-thread/

Planetary Resources, Inc. Asteroid Mining: First telescope launch within 24 months

1567810

Posts

  • electricitylikesmeelectricitylikesme Registered User regular
    It really depends on what you're trying to do. If you just want to move the asteroid around then UV-band lasers would probably be fine. You'd actually want a wide dispersion angle to spread the momentum transfer across the occlusive cross-section of the object and ensure the maximum radiated-to-kinetic energy transfer. Having a tight focus on the target would increase the likelihood of ionization/excitation in the material and you'd lose a lot of energy to phonon generation. If you wanted to actually chop up the rock into bits, x-ray laser might be a good way to do it. Or something like an industrial-scale version of the gamma knife they use for cancer treatment (those things are fucking awesome, by the way, if you've never been in the room with one... you go in through this 3 foot thick metal door like something out of a sci-fi movie and there's this giant rotating machine that projects a green laser grid across the room for targeting). But I bet you could build a robot that would spin up a laser-sail out of pure gold mined straight from the asteroid. Gold's a pretty good reflector and is fairly strong even when made as an extremely thin film. Strong enough to handle a few MW of momentum transfer from a laser and not just go to shit if it gets a few micropunctures by floating space dust creating during mining operations, anyway.

    Well my thinking was you'd trigger evaporation of the surface, which would then give you a much better specific impulse from the laser.

  • Mr_RoseMr_Rose 83 Blue Ridge Protects the Holy Registered User regular
    edited April 2012
    Talking of gamma knives, the picture of the "early model" on Wikipedia is amazing. No wonder people in the sixties thought we'd all be wearing tinfoil suits by now…

    Mr_Rose on
    ...because dragons are AWESOME! That's why.
    Nintendo Network ID: AzraelRose
    DropBox invite link - get 500MB extra free.
  • Salvation122Salvation122 Registered User regular
    This is pretty much completely off-topic to asteroid mining, but totally on-topic to space lasers:

    In grad school my nuclear physics professor was explaining...something or other about phase space transformations, and encouraged us to consider how what we were learning could be applied to constructing a material that would be reflective in the x-ray part of the EMR spectrum. Apparently the technology exists and is well-classified by the US DoD to build space-based x-ray lasers (which, thanks to the high energy allows for extremely tight confinement...a properly tuned orbital x-ray laser could hit a target on the ground about the size of a dime), so I am forced to assume that we do, in fact, have orbital x-ray space lasers up there somewhere. The whole process is totally out in the open, but anyone who actually knows how to build an x-ray lasing cavity is bound by the government not to tell anyone. It's not terribly theoretically difficult to figure out, but I have no idea how you'd go about actually making the material from an engineering standpoint.

    Are we sure he wasn't crazy? I mean, you can just buy lab coats, and I have to presume if we had the Hammer of Dawn, we'd be rolling that bad boy out,

    Well, space-based weapons are outlawed by the Outer Space Treaty, which has over a hundred signatories.

    Knowing how to build something doesn't mean that you actually built it.

  • Mr_RoseMr_Rose 83 Blue Ridge Protects the Holy Registered User regular
    Isn't that just space-based nuclear weapons?
    I remember that a more general weapons ban never got ratified because of the practicalities of deciding whether your multi-terawatt x-ray laser with 0.0001 arc second accuracy is a propulsion system or an interplanetary terror weapon.

    Truly, any propulsion system powerful enough to be interesting is powerful enough to be a weapon.

    ...because dragons are AWESOME! That's why.
    Nintendo Network ID: AzraelRose
    DropBox invite link - get 500MB extra free.
  • [Tycho?][Tycho?] As elusive as doubt Registered User regular
    edited April 2012
    Mr_Rose wrote: »
    Isn't that just space-based nuclear weapons?
    I remember that a more general weapons ban never got ratified because of the practicalities of deciding whether your multi-terawatt x-ray laser with 0.0001 arc second accuracy is a propulsion system or an interplanetary terror weapon.

    Truly, any propulsion system powerful enough to be interesting is powerful enough to be a weapon.

    Conventional weapons are allowed, which I did not know.

    http://en.wikipedia.org/wiki/Outer_Space_Treaty

    I knew there would be weapons of some sort up there, but them being expressly allowed makes me wonder just how many are in orbit as we speak.

    Speaking of which, the X-37B, the robotic space plane is perfect for both delivering weapons to orbit, or messing with other countries satellites. The craft is under the control of the Pentagon rather than NASA, and its missions are kept secret. Of course, its still claimed the missions are purely for scientific research.

    [Tycho?] on
    mvaYcgc.jpg
  • CycloneRangerCycloneRanger Registered User regular
    It really depends on what you're trying to do. If you just want to move the asteroid around then UV-band lasers would probably be fine. You'd actually want a wide dispersion angle to spread the momentum transfer across the occlusive cross-section of the object and ensure the maximum radiated-to-kinetic energy transfer. Having a tight focus on the target would increase the likelihood of ionization/excitation in the material and you'd lose a lot of energy to phonon generation. If you wanted to actually chop up the rock into bits, x-ray laser might be a good way to do it. Or something like an industrial-scale version of the gamma knife they use for cancer treatment (those things are fucking awesome, by the way, if you've never been in the room with one... you go in through this 3 foot thick metal door like something out of a sci-fi movie and there's this giant rotating machine that projects a green laser grid across the room for targeting). But I bet you could build a robot that would spin up a laser-sail out of pure gold mined straight from the asteroid. Gold's a pretty good reflector and is fairly strong even when made as an extremely thin film. Strong enough to handle a few MW of momentum transfer from a laser and not just go to shit if it gets a few micropunctures by floating space dust creating during mining operations, anyway.

    Well my thinking was you'd trigger evaporation of the surface, which would then give you a much better specific impulse from the laser.
    Yeah, the goal would be to make the surface ablate or at least discharge any frozen volatiles on the side you're illuminating--not to push the asteroid around with photon momentum.

  • Mr_RoseMr_Rose 83 Blue Ridge Protects the Holy Registered User regular
    Reminds me of a way someone figured out to make laser weapons practical against armour; fire two pulses, nanoseconds apart, the first to initiate surface vaporisation and the second to excite the newly expanding cloud of debris into plasma, causing an explosion that triggers spalling on the other side. Never saw a follow up though.

    ...because dragons are AWESOME! That's why.
    Nintendo Network ID: AzraelRose
    DropBox invite link - get 500MB extra free.
  • KageraKagera Imitating the worst people. Since 2004Registered User regular
    Mr_Rose wrote: »
    Reminds me of a way someone figured out to make laser weapons practical against armour; fire two pulses, nanoseconds apart, the first to initiate surface vaporisation and the second to excite the newly expanding cloud of debris into plasma, causing an explosion that triggers spalling on the other side. Never saw a follow up though.

    Well of course you didn't you don't have the clearance.

    My neck, my back, my FUPA and my crack.
  • CptHamiltonCptHamilton Registered User regular
    It really depends on what you're trying to do. If you just want to move the asteroid around then UV-band lasers would probably be fine. You'd actually want a wide dispersion angle to spread the momentum transfer across the occlusive cross-section of the object and ensure the maximum radiated-to-kinetic energy transfer. Having a tight focus on the target would increase the likelihood of ionization/excitation in the material and you'd lose a lot of energy to phonon generation. If you wanted to actually chop up the rock into bits, x-ray laser might be a good way to do it. Or something like an industrial-scale version of the gamma knife they use for cancer treatment (those things are fucking awesome, by the way, if you've never been in the room with one... you go in through this 3 foot thick metal door like something out of a sci-fi movie and there's this giant rotating machine that projects a green laser grid across the room for targeting). But I bet you could build a robot that would spin up a laser-sail out of pure gold mined straight from the asteroid. Gold's a pretty good reflector and is fairly strong even when made as an extremely thin film. Strong enough to handle a few MW of momentum transfer from a laser and not just go to shit if it gets a few micropunctures by floating space dust creating during mining operations, anyway.

    Well my thinking was you'd trigger evaporation of the surface, which would then give you a much better specific impulse from the laser.
    Yeah, the goal would be to make the surface ablate or at least discharge any frozen volatiles on the side you're illuminating--not to push the asteroid around with photon momentum.

    You could get better specific impulse for fine steering with surface vaporization, but you wouldn't get any more oomph out of it than just pushing it with photons. But if we're going to go whole-hog on the imaginative ways to move asteroids around...

    Instead of pushing the rock with a laser, you could set up a mass driver system on the asteroid that takes chunks of conductive material out of the bulk and accelerates them using power provided via narrow-beam laser to a photoreceptor on the mass driver. Though then you'd need to worry about having very high velocity hunks of metal careering around the solar system.

    PSN,Steam,Live | CptHamiltonian
  • Mr_RoseMr_Rose 83 Blue Ridge Protects the Holy Registered User regular
    Not if the chunks of metal are being delivered to your destination; if they are on a ciprocal orbit, they can be used to decelerate the asteroid on arrival at the target. Maybe?

    ...because dragons are AWESOME! That's why.
    Nintendo Network ID: AzraelRose
    DropBox invite link - get 500MB extra free.
  • Mild ConfusionMild Confusion Smash All Things Registered User regular
    edited April 2012
    Aim them at Jupiter. If on the other side of Earth, aim at the sun.

    Mild Confusion on
    steam_sig.png

    Battlenet ID: MildC#11186 - If I'm in the game, send me an invite at anytime and I'll play.
  • ButtcleftButtcleft Registered User regular
    [Tycho?] wrote: »
    Mr_Rose wrote: »
    Isn't that just space-based nuclear weapons?
    I remember that a more general weapons ban never got ratified because of the practicalities of deciding whether your multi-terawatt x-ray laser with 0.0001 arc second accuracy is a propulsion system or an interplanetary terror weapon.

    Truly, any propulsion system powerful enough to be interesting is powerful enough to be a weapon.

    Conventional weapons are allowed, which I did not know.

    http://en.wikipedia.org/wiki/Outer_Space_Treaty

    I knew there would be weapons of some sort up there, but them being expressly allowed makes me wonder just how many are in orbit as we speak.

    Some Soviet stations had conventional cannons built into them.

  • Salvation122Salvation122 Registered User regular
    Buttcleft wrote: »
    [Tycho?] wrote: »
    Mr_Rose wrote: »
    Isn't that just space-based nuclear weapons?
    I remember that a more general weapons ban never got ratified because of the practicalities of deciding whether your multi-terawatt x-ray laser with 0.0001 arc second accuracy is a propulsion system or an interplanetary terror weapon.

    Truly, any propulsion system powerful enough to be interesting is powerful enough to be a weapon.

    Conventional weapons are allowed, which I did not know.

    http://en.wikipedia.org/wiki/Outer_Space_Treaty

    I knew there would be weapons of some sort up there, but them being expressly allowed makes me wonder just how many are in orbit as we speak.

    Some Soviet stations had conventional cannons built into them.

    What? Cite.

  • [Tycho?][Tycho?] As elusive as doubt Registered User regular
    Buttcleft wrote: »
    [Tycho?] wrote: »
    Mr_Rose wrote: »
    Isn't that just space-based nuclear weapons?
    I remember that a more general weapons ban never got ratified because of the practicalities of deciding whether your multi-terawatt x-ray laser with 0.0001 arc second accuracy is a propulsion system or an interplanetary terror weapon.

    Truly, any propulsion system powerful enough to be interesting is powerful enough to be a weapon.

    Conventional weapons are allowed, which I did not know.

    http://en.wikipedia.org/wiki/Outer_Space_Treaty

    I knew there would be weapons of some sort up there, but them being expressly allowed makes me wonder just how many are in orbit as we speak.

    Some Soviet stations had conventional cannons built into them.

    I don't understand what this means, given the context. A "conventional cannon" in my mind is like an artillery piece. Which, for one thing, requires oxygen to fire. More details are needed!

    mvaYcgc.jpg
  • KageraKagera Imitating the worst people. Since 2004Registered User regular
    [Tycho?] wrote: »
    Buttcleft wrote: »
    [Tycho?] wrote: »
    Mr_Rose wrote: »
    Isn't that just space-based nuclear weapons?
    I remember that a more general weapons ban never got ratified because of the practicalities of deciding whether your multi-terawatt x-ray laser with 0.0001 arc second accuracy is a propulsion system or an interplanetary terror weapon.

    Truly, any propulsion system powerful enough to be interesting is powerful enough to be a weapon.

    Conventional weapons are allowed, which I did not know.

    http://en.wikipedia.org/wiki/Outer_Space_Treaty

    I knew there would be weapons of some sort up there, but them being expressly allowed makes me wonder just how many are in orbit as we speak.

    Some Soviet stations had conventional cannons built into them.

    I don't understand what this means, given the context. A "conventional cannon" in my mind is like an artillery piece. Which, for one thing, requires oxygen to fire. More details are needed!

    Mass drivers obviously.

    My neck, my back, my FUPA and my crack.
  • Mild ConfusionMild Confusion Smash All Things Registered User regular
    [Tycho?] wrote: »
    Buttcleft wrote: »
    [Tycho?] wrote: »
    Mr_Rose wrote: »
    Isn't that just space-based nuclear weapons?
    I remember that a more general weapons ban never got ratified because of the practicalities of deciding whether your multi-terawatt x-ray laser with 0.0001 arc second accuracy is a propulsion system or an interplanetary terror weapon.

    Truly, any propulsion system powerful enough to be interesting is powerful enough to be a weapon.

    Conventional weapons are allowed, which I did not know.

    http://en.wikipedia.org/wiki/Outer_Space_Treaty

    I knew there would be weapons of some sort up there, but them being expressly allowed makes me wonder just how many are in orbit as we speak.

    Some Soviet stations had conventional cannons built into them.

    I don't understand what this means, given the context. A "conventional cannon" in my mind is like an artillery piece. Which, for one thing, requires oxygen to fire. More details are needed!

    Hypothetically: Wouldn't you be able to seal enough oxygen inside of the round itself? Especially if you compress the air?

    steam_sig.png

    Battlenet ID: MildC#11186 - If I'm in the game, send me an invite at anytime and I'll play.
  • Pi-r8Pi-r8 Registered User regular
    [Tycho?] wrote: »
    Buttcleft wrote: »
    [Tycho?] wrote: »
    Mr_Rose wrote: »
    Isn't that just space-based nuclear weapons?
    I remember that a more general weapons ban never got ratified because of the practicalities of deciding whether your multi-terawatt x-ray laser with 0.0001 arc second accuracy is a propulsion system or an interplanetary terror weapon.

    Truly, any propulsion system powerful enough to be interesting is powerful enough to be a weapon.

    Conventional weapons are allowed, which I did not know.

    http://en.wikipedia.org/wiki/Outer_Space_Treaty

    I knew there would be weapons of some sort up there, but them being expressly allowed makes me wonder just how many are in orbit as we speak.

    Some Soviet stations had conventional cannons built into them.

    I don't understand what this means, given the context. A "conventional cannon" in my mind is like an artillery piece. Which, for one thing, requires oxygen to fire. More details are needed!
    If you're in orbit, you don't need to fire it. You can just drop the cannonball on the target :P

  • DiannaoChongDiannaoChong Registered User regular
    edited April 2012
    Coca Cola figured out that it was technically possible to use lasers to beam their logo onto the moon — not to physically etch the logo onto the surface, but to continuously illuminate it like in a laser show. They were stopped from doing so over concerns that the lasers would interfere with passing aircraft.

    :shock:

    I'd like to see the hard science behind this. That jackass nobody heard of wanted everyone to go out and shine laser pointers at the moon all at the same time to try and make a visible dot on it a few years ago, and it caught on as a viral thing. tv news showed how it wasn't possible because the pointers weren't strong enough and would dilute by the time they got to their target. and this was even if everyone pointed at the exact same point. I'd like to know what was going to be used to project the image. If airplanes were really an issue, they can get clearance to stop planes from flying over specific areas, or find a place and buy the property where this is already the case....

    DiannaoChong on
    steam_sig.png
  • Salvation122Salvation122 Registered User regular
    [Tycho?] wrote: »
    Buttcleft wrote: »
    [Tycho?] wrote: »
    Mr_Rose wrote: »
    Isn't that just space-based nuclear weapons?
    I remember that a more general weapons ban never got ratified because of the practicalities of deciding whether your multi-terawatt x-ray laser with 0.0001 arc second accuracy is a propulsion system or an interplanetary terror weapon.

    Truly, any propulsion system powerful enough to be interesting is powerful enough to be a weapon.

    Conventional weapons are allowed, which I did not know.

    http://en.wikipedia.org/wiki/Outer_Space_Treaty

    I knew there would be weapons of some sort up there, but them being expressly allowed makes me wonder just how many are in orbit as we speak.

    Some Soviet stations had conventional cannons built into them.

    I don't understand what this means, given the context. A "conventional cannon" in my mind is like an artillery piece. Which, for one thing, requires oxygen to fire. More details are needed!

    There are conventional explosives with their own oxidation agents already, I'm pretty sure.

  • PhyphorPhyphor Building Planet Busters Tasting FruitRegistered User regular
    edited April 2012
    Buttcleft wrote: »
    [Tycho?] wrote: »
    Mr_Rose wrote: »
    Isn't that just space-based nuclear weapons?
    I remember that a more general weapons ban never got ratified because of the practicalities of deciding whether your multi-terawatt x-ray laser with 0.0001 arc second accuracy is a propulsion system or an interplanetary terror weapon.

    Truly, any propulsion system powerful enough to be interesting is powerful enough to be a weapon.

    Conventional weapons are allowed, which I did not know.

    http://en.wikipedia.org/wiki/Outer_Space_Treaty

    I knew there would be weapons of some sort up there, but them being expressly allowed makes me wonder just how many are in orbit as we speak.

    Some Soviet stations had conventional cannons built into them.

    What? Cite.

    Apparently there was, at least on one station

    Phyphor on
  • CycloneRangerCycloneRanger Registered User regular
    edited April 2012
    It really depends on what you're trying to do. If you just want to move the asteroid around then UV-band lasers would probably be fine. You'd actually want a wide dispersion angle to spread the momentum transfer across the occlusive cross-section of the object and ensure the maximum radiated-to-kinetic energy transfer. Having a tight focus on the target would increase the likelihood of ionization/excitation in the material and you'd lose a lot of energy to phonon generation. If you wanted to actually chop up the rock into bits, x-ray laser might be a good way to do it. Or something like an industrial-scale version of the gamma knife they use for cancer treatment (those things are fucking awesome, by the way, if you've never been in the room with one... you go in through this 3 foot thick metal door like something out of a sci-fi movie and there's this giant rotating machine that projects a green laser grid across the room for targeting). But I bet you could build a robot that would spin up a laser-sail out of pure gold mined straight from the asteroid. Gold's a pretty good reflector and is fairly strong even when made as an extremely thin film. Strong enough to handle a few MW of momentum transfer from a laser and not just go to shit if it gets a few micropunctures by floating space dust creating during mining operations, anyway.

    Well my thinking was you'd trigger evaporation of the surface, which would then give you a much better specific impulse from the laser.
    Yeah, the goal would be to make the surface ablate or at least discharge any frozen volatiles on the side you're illuminating--not to push the asteroid around with photon momentum.

    You could get better specific impulse for fine steering with surface vaporization, but you wouldn't get any more oomph out of it than just pushing it with photons.
    Yes, you absolutely would--thrust is a function of momentum change. By vaporising bits of asteroid and propelling them (as vapor or plasma) into space you will dramatically increase the total force applied. Effectively you're increasing your reaction mass, which (for a fixed energy input) will significantly increase thrust.
    But if we're going to go whole-hog on the imaginative ways to move asteroids around...

    Instead of pushing the rock with a laser, you could set up a mass driver system on the asteroid that takes chunks of conductive material out of the bulk and accelerates them using power provided via narrow-beam laser to a photoreceptor on the mass driver. Though then you'd need to worry about having very high velocity hunks of metal careering around the solar system.
    A mass driver or nuclear rocket on the surface of an asteroid would work, but is likely inferior in terms of gross adjustments to a nuclear explosive placed a few meters beneath the surface (ejecting thousands of tons of material into space). You'd basically be attempting a version of what Project Orion thought to do. Obviously not all asteroids are really candidates for any given method, which is part of why the first step PRI is taking is to study near-Earth asteroids.

    CycloneRanger on
  • CycloneRangerCycloneRanger Registered User regular
    edited April 2012
    Also, I don't know where the idea that guns require oxygen to fire came from--that doesn't even really make sense. Do you think the tiny amount of atmospheric oxygen that the gunpowder is in contact with when packed into the breech is reacting to produce the necessary energy to propel a bullet?

    Gunpowder includes its own oxidizer. There are mechanical problems that might interrupt a gun or cannon's functioning in space (cold welding, changes in pressure, etc.), but they certainly don't need ambient O2 to fire.

    CycloneRanger on
  • electricitylikesmeelectricitylikesme Registered User regular
    Also, I don't know where the idea that guns require oxygen to fire came from--that doesn't even really make sense. Do you think the tiny amount of atmospheric oxygen that the gunpowder is in contact with when packed into the breech is reacting to produce the necessary energy to propel a bullet?

    Gunpowder includes its own oxidizer. There are mechanical problems that might interrupt a gun or cannon's functioning in space (cold welding, changes in pressure, etc.), but they certainly don't need ambient O2 to fire.

    Also worth noting: Guns can be fired underwater - where there definitely isn't enough oxygen to support a flame, already.

    The "needs oxygen to fire" was Joss Whedon fucking up in writing Firefly.

  • KageraKagera Imitating the worst people. Since 2004Registered User regular
    Also, I don't know where the idea that guns require oxygen to fire came from--that doesn't even really make sense. Do you think the tiny amount of atmospheric oxygen that the gunpowder is in contact with when packed into the breech is reacting to produce the necessary energy to propel a bullet?

    Gunpowder includes its own oxidizer. There are mechanical problems that might interrupt a gun or cannon's functioning in space (cold welding, changes in pressure, etc.), but they certainly don't need ambient O2 to fire.

    Also worth noting: Guns can be fired underwater - where there definitely isn't enough oxygen to support a flame, already.

    The "needs oxygen to fire" was Joss Whedon fucking up in writing Firefly.

    Pretty sure it's a mistake that predates Firefly

    My neck, my back, my FUPA and my crack.
  • electricitylikesmeelectricitylikesme Registered User regular
    Kagera wrote: »
    Also, I don't know where the idea that guns require oxygen to fire came from--that doesn't even really make sense. Do you think the tiny amount of atmospheric oxygen that the gunpowder is in contact with when packed into the breech is reacting to produce the necessary energy to propel a bullet?

    Gunpowder includes its own oxidizer. There are mechanical problems that might interrupt a gun or cannon's functioning in space (cold welding, changes in pressure, etc.), but they certainly don't need ambient O2 to fire.

    Also worth noting: Guns can be fired underwater - where there definitely isn't enough oxygen to support a flame, already.

    The "needs oxygen to fire" was Joss Whedon fucking up in writing Firefly.

    Pretty sure it's a mistake that predates Firefly

    It's true that Firefly is only safe when moving as a series.

  • KageraKagera Imitating the worst people. Since 2004Registered User regular
    No really I remember seeing Wing Commander the movie and a lot of people bitched about how their life got flipped turned upside down...

    wait...no. I mean they bitched about how bullets wouldn't work in space and that was before Firefly so the myth was out there.

    My neck, my back, my FUPA and my crack.
  • V1mV1m Registered User regular
    Kagera wrote: »
    Also, I don't know where the idea that guns require oxygen to fire came from--that doesn't even really make sense. Do you think the tiny amount of atmospheric oxygen that the gunpowder is in contact with when packed into the breech is reacting to produce the necessary energy to propel a bullet?

    Gunpowder includes its own oxidizer. There are mechanical problems that might interrupt a gun or cannon's functioning in space (cold welding, changes in pressure, etc.), but they certainly don't need ambient O2 to fire.

    Also worth noting: Guns can be fired underwater - where there definitely isn't enough oxygen to support a flame, already.

    The "needs oxygen to fire" was Joss Whedon fucking up in writing Firefly.

    Pretty sure it's a mistake that predates Firefly

    Let me tell you about how rockets won't work in space because there's nothing for them to push against.

  • Mr_RoseMr_Rose 83 Blue Ridge Protects the Holy Registered User regular
    Kagera wrote: »
    Also, I don't know where the idea that guns require oxygen to fire came from--that doesn't even really make sense. Do you think the tiny amount of atmospheric oxygen that the gunpowder is in contact with when packed into the breech is reacting to produce the necessary energy to propel a bullet?

    Gunpowder includes its own oxidizer. There are mechanical problems that might interrupt a gun or cannon's functioning in space (cold welding, changes in pressure, etc.), but they certainly don't need ambient O2 to fire.

    Also worth noting: Guns can be fired underwater - where there definitely isn't enough oxygen to support a flame, already.

    The "needs oxygen to fire" was Joss Whedon fucking up in writing Firefly.

    Pretty sure it's a mistake that predates Firefly

    Was he not talking about the gun as a whole and not necessarily the round itself? Vacuum does a lot of weird things to metals and lubricants not designed for it after all…

    As for what V1m brought up; yeah that one always freaks me out when I encounter it… it still amazes me that people can hold that view for long enough that correction never takes. I'm pretty sure the explanation was pretty much the second thing I was told about rockets after, y'know, that rockets exist.

    ...because dragons are AWESOME! That's why.
    Nintendo Network ID: AzraelRose
    DropBox invite link - get 500MB extra free.
  • electricitylikesmeelectricitylikesme Registered User regular
    The main thing about explosives is that there's no possible way for them to get enough oxygen to detonate from the environment. Every explosive is based on putting the oxygen needed for the reaction in the molecule itself - which is about as close as you get it.

    i.e. check out nitroglycerin:
    250px-Nitroglycerin.svg.png

    The reason that works as an explosive is because the molecule is going to self-combust with all those oxygens hanging around there. The detonation happens because the shockwave from the first combustion triggers the other molecules to degrade before the flame-front actually gets there, so on a macroscopic scale it explodes rather then burns.

  • [Tycho?][Tycho?] As elusive as doubt Registered User regular
    Well, good to know that guns don't actually require oxygen to fire. Makes sense; I picked up that misconception from old video games, far before Firefly.

    But I still don't know what a "conventional cannon" in space is. I can imagine all kinds of ways to have a cannon in space, but that doesn't explain was was actually -supposedly- put up there by the Soviets.

    mvaYcgc.jpg
  • electricitylikesmeelectricitylikesme Registered User regular
    [Tycho?] wrote: »
    Well, good to know that guns don't actually require oxygen to fire. Makes sense; I picked up that misconception from old video games, far before Firefly.

    But I still don't know what a "conventional cannon" in space is. I can imagine all kinds of ways to have a cannon in space, but that doesn't explain was was actually -supposedly- put up there by the Soviets.

    As I understand it at least one satellite was launched which had a normal .50 cal machine gun on their. They fired a few dozen rounds under remote control.

  • evilbobevilbob RADELAIDERegistered User regular
    [Tycho?] wrote: »
    Well, good to know that guns don't actually require oxygen to fire. Makes sense; I picked up that misconception from old video games, far before Firefly.

    But I still don't know what a "conventional cannon" in space is. I can imagine all kinds of ways to have a cannon in space, but that doesn't explain was was actually -supposedly- put up there by the Soviets.

    As I understand it at least one satellite was launched which had a normal .50 cal machine gun on their. They fired a few dozen rounds under remote control.

    It was a space station with a 23mm cannon. It was aimed by rotating the whole station.

    l5sruu1fyatf.jpg

  • electricitylikesmeelectricitylikesme Registered User regular
    evilbob wrote: »
    [Tycho?] wrote: »
    Well, good to know that guns don't actually require oxygen to fire. Makes sense; I picked up that misconception from old video games, far before Firefly.

    But I still don't know what a "conventional cannon" in space is. I can imagine all kinds of ways to have a cannon in space, but that doesn't explain was was actually -supposedly- put up there by the Soviets.

    As I understand it at least one satellite was launched which had a normal .50 cal machine gun on their. They fired a few dozen rounds under remote control.

    It was a space station with a 23mm cannon. It was aimed by rotating the whole station.

    There was definitely a machine gun as well. It's Russia - they launched quite a number of things.

  • CycloneRangerCycloneRanger Registered User regular
    The whole things just makes me smile--I can totally imagine some engineer being told by a Soviet politician to put a gun on his space station. That conversation must have been funny.

  • evilbobevilbob RADELAIDERegistered User regular
    Well it was a military space station.

    l5sruu1fyatf.jpg

  • autono-wally, erotibot300autono-wally, erotibot300 love machine Registered User regular
    Is there anyone who didn't arm their stations?
    Finland? Well thanks for nothing!

    kFJhXwE.jpgkFJhXwE.jpg
  • BurtletoyBurtletoy Registered User regular
    Every explosive is based on putting the oxygen needed for the reaction in the molecule itself - which is about as close as you get it.

    Disagree!

    http://en.wikipedia.org/wiki/Thermobaric_weapon

  • CptHamiltonCptHamilton Registered User regular
    It really depends on what you're trying to do. If you just want to move the asteroid around then UV-band lasers would probably be fine. You'd actually want a wide dispersion angle to spread the momentum transfer across the occlusive cross-section of the object and ensure the maximum radiated-to-kinetic energy transfer. Having a tight focus on the target would increase the likelihood of ionization/excitation in the material and you'd lose a lot of energy to phonon generation. If you wanted to actually chop up the rock into bits, x-ray laser might be a good way to do it. Or something like an industrial-scale version of the gamma knife they use for cancer treatment (those things are fucking awesome, by the way, if you've never been in the room with one... you go in through this 3 foot thick metal door like something out of a sci-fi movie and there's this giant rotating machine that projects a green laser grid across the room for targeting). But I bet you could build a robot that would spin up a laser-sail out of pure gold mined straight from the asteroid. Gold's a pretty good reflector and is fairly strong even when made as an extremely thin film. Strong enough to handle a few MW of momentum transfer from a laser and not just go to shit if it gets a few micropunctures by floating space dust creating during mining operations, anyway.

    Well my thinking was you'd trigger evaporation of the surface, which would then give you a much better specific impulse from the laser.
    Yeah, the goal would be to make the surface ablate or at least discharge any frozen volatiles on the side you're illuminating--not to push the asteroid around with photon momentum.

    You could get better specific impulse for fine steering with surface vaporization, but you wouldn't get any more oomph out of it than just pushing it with photons.
    Yes, you absolutely would--thrust is a function of momentum change. By vaporising bits of asteroid and propelling them (as vapor or plasma) into space you will dramatically increase the total force applied. Effectively you're increasing your reaction mass, which (for a fixed energy input) will significantly increase thrust.

    Hmm. I guess it depends on how fast you wanted to move the asteroid. The thrust gain from mass ejection is due to the fact that the mass you're ejecting is no longer part of the body being accelerated, meanwhile you're storing up a lot of energy that would either be gained as momentum in a full-reflection scenario in heat stored by the metals not actually vaporized. I can think of scenarios where either could be considered more energy efficient, and I feel like the general category of scenarios that favor mass ejection are going to be economically unfavorable. Unless the asteroid has a lot of material that you just don't economically care about, it seems like you'd be better off pushing it more slowly in one piece than ejecting parts of it to get it to the mining orbit.
    But if we're going to go whole-hog on the imaginative ways to move asteroids around...

    Instead of pushing the rock with a laser, you could set up a mass driver system on the asteroid that takes chunks of conductive material out of the bulk and accelerates them using power provided via narrow-beam laser to a photoreceptor on the mass driver. Though then you'd need to worry about having very high velocity hunks of metal careering around the solar system.
    A mass driver or nuclear rocket on the surface of an asteroid would work, but is likely inferior in terms of gross adjustments to a nuclear explosive placed a few meters beneath the surface (ejecting thousands of tons of material into space). You'd basically be attempting a version of what Project Orion thought to do. Obviously not all asteroids are really candidates for any given method, which is part of why the first step PRI is taking is to study near-Earth asteroids.

    All the parts of a mass driver besides the capacitors used to hold charge prior to driver initiation could be manufactured fairly easy in-situ out of available metals by a mining robot and requires no fuel. A nuclear rocket is going to need fuel, which may not be available on a rocky asteroid. Building a nuclear explosive in-situ on an asteroid is pretty much a non-starter. I was thinking about asteroid maneuvering devices that require hauling as little as is physically possible from Earth orbit to the asteroid. Hitting it with a laser based in cislunar space or at a lagrange point or something wouldn't require that you move the laser ever again after getting it up there in the first place, and if you're okay with waiting a little while for the thing to get where it's going, sending a robot capable of building a mass driver or sail out to the rock would cost a lot less (energetically) up-front than any kind of consumable-fuel drive.

    PSN,Steam,Live | CptHamiltonian
  • CycloneRangerCycloneRanger Registered User regular
    edited April 2012
    It really depends on what you're trying to do. If you just want to move the asteroid around then UV-band lasers would probably be fine. You'd actually want a wide dispersion angle to spread the momentum transfer across the occlusive cross-section of the object and ensure the maximum radiated-to-kinetic energy transfer. Having a tight focus on the target would increase the likelihood of ionization/excitation in the material and you'd lose a lot of energy to phonon generation. If you wanted to actually chop up the rock into bits, x-ray laser might be a good way to do it. Or something like an industrial-scale version of the gamma knife they use for cancer treatment (those things are fucking awesome, by the way, if you've never been in the room with one... you go in through this 3 foot thick metal door like something out of a sci-fi movie and there's this giant rotating machine that projects a green laser grid across the room for targeting). But I bet you could build a robot that would spin up a laser-sail out of pure gold mined straight from the asteroid. Gold's a pretty good reflector and is fairly strong even when made as an extremely thin film. Strong enough to handle a few MW of momentum transfer from a laser and not just go to shit if it gets a few micropunctures by floating space dust creating during mining operations, anyway.

    Well my thinking was you'd trigger evaporation of the surface, which would then give you a much better specific impulse from the laser.
    Yeah, the goal would be to make the surface ablate or at least discharge any frozen volatiles on the side you're illuminating--not to push the asteroid around with photon momentum.

    You could get better specific impulse for fine steering with surface vaporization, but you wouldn't get any more oomph out of it than just pushing it with photons.
    Yes, you absolutely would--thrust is a function of momentum change. By vaporising bits of asteroid and propelling them (as vapor or plasma) into space you will dramatically increase the total force applied. Effectively you're increasing your reaction mass, which (for a fixed energy input) will significantly increase thrust.

    Hmm. I guess it depends on how fast you wanted to move the asteroid. The thrust gain from mass ejection is due to the fact that the mass you're ejecting is no longer part of the body being accelerated, meanwhile you're storing up a lot of energy that would either be gained as momentum in a full-reflection scenario in heat stored by the metals not actually vaporized. I can think of scenarios where either could be considered more energy efficient, and I feel like the general category of scenarios that favor mass ejection are going to be economically unfavorable. Unless the asteroid has a lot of material that you just don't economically care about, it seems like you'd be better off pushing it more slowly in one piece than ejecting parts of it to get it to the mining orbit.
    No, you've still got it wrong--I think you have a fundamental misunderstanding of the physics involved. In fact, I'm certain you do--you mentioned better specific impulse, but less "oomph" (which I take as meaning "thrust"). That's not correct (assuming you're measuring fuel consumption in terms of whatever is powering the laser--which is the only way SI is a meaningful metric here in the first place). You seem to be under the impression that, because energy is conserved, the total thrust imparted to the asteroid is going to be constant in some way. This isn't correct, and you can see this by examining any number of more familiar propulsion systems. Take a jet engine vs. a rocket engine--a jet engine is fantastically more efficient, and it becomes still more efficient as more bypass flow is added (this is one of the main reasons we use high-bypass turbofans on anything that doesn't need to go very, very fast). For a finite power supplied, the total thrust scales with reaction mass. You can see this in the equations for kinetic energy and momentum--momentum scales linearly with velocity and mass, while kinetic energy scales linearly with mass and quadratically with velocity. Thrust is a change in momentum, so for a given quantity of energy you will get the best thrust by using the largest possible reaction mass. "Slowly" ejecting some plasma from the surface produces a lot more thrust than does very quickly ejecting a photon, and the effect is not dependent on the decrease in mass in the asteroid that you're trying to move--that is, we're not "shaving it down" and thereby moving it faster over time. (The acceleration of the asteroid will of course depend on its mass--but the thrust is independent of that, and we can consider only a setup that uses a negligible portion of the asteroid, or an arbitrarily large asteroid, if that will help make things clear).

    Another way to think of it is in terms of kinetic energy--discarding for the moment losses to heat, etc. you want the exhaust (be it photons or heated volatiles on the surface) to carry off as little kinetic energy as possible, because you want the asteroid itself to carry off as much as possible. This requires the lowest possible exhaust velocity, and since energy is conserved we therefore want the highest possible exhaust mass. In the example of a photon sail, the photons carry off almost all the energy they started with.

    So, what you'd really want is to use some of the asteroid as reaction mass, with energy provided to accelerate it either via ambient solar, a nuclear reactor, or a laser, if you were going to use one of those approaches to start with.

    CycloneRanger on
  • SynthesisSynthesis Honda Today! Registered User regular
    edited April 2012
    evilbob wrote: »
    Well it was a military space station.

    De facto, they were all military space stations. I'm not sure what wouldn't qualify as a military space station since you couldn't exactly cram them full of guys with rifles that easily, and military forces throughout the world are interested in scientific experimentation. NASA wasn't filled with Air Force personnel because I Dream of Genie was such a great show.

    If I had to guess, I'd say "Because everyone came from the Air Force when NASA was founded."

    Synthesis on
Sign In or Register to comment.