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Noclevername
2012-Oct-20, 08:20 PM
I know that a nuclear bomb requires at least some atmosphere to produce a signifigant electromagnetic pulse. I also know there are conventional-explosive EMP generators, but their range is quite limited.

Would it be possible to create a nuclear e-bomb that works in full vacuum, with long-range effects?

publiusr
2012-Oct-20, 08:38 PM
I thought AC CLark once said that a nuke shot off in space might illuminate asteroids and allow for their detection

antoniseb
2012-Oct-20, 09:06 PM
... Would it be possible to create a nuclear e-bomb that works in full vacuum, with long-range effects?
I think anyone who could answer this, even if such a device is impossible, would be violating some agreement by discussing it.
Can you say something about what you have in mind?

Noclevername
2012-Oct-20, 09:19 PM
I think anyone who could answer this, even if such a device is impossible, would be violating some agreement by discussing it.
Can you say something about what you have in mind?

I'm working on a story involving deep-space combat, see here (http://cosmoquest.org/forum/showthread.php/138448-Antigravity-FTL-and-realism) and here (http://cosmoquest.org/forum/showthread.php/138467-The-logistics-of-Space-Marines), and I wanted to know if such a weapon would be plausible or at least can be made to seem realistic using current physics.

Swift
2012-Oct-20, 09:32 PM
I thought AC CLark once said that a nuke shot off in space might illuminate asteroids and allow for their detection
Please do not post off-topic comments in Q&A

Ara Pacis
2012-Oct-20, 09:50 PM
No. The wikipedia article on EMP (http://en.wikipedia.org/wiki/Electromagnetic_pulse) explains how it works in fair detail. Not only do you need atmosphere, but I you need a magnetic field for the important effects. I think the only effects a target in space would feel would be from direct interaction with the gammas, neutrons and other particles which would spread out rapidly and would not have an atmosphere or magnetosphere to amplify their activity. If you can induce currents in the enemy ships via their hull or engine exhaust, then maybe you'll get some electrical effects. I'm not sure.

Somehow I knew this would come up in your threads when I mentioned that the only warheads you could realistically use would be fragmentation and hyperkinetic. Nuclear might be useful, but you'd still have to be fairly close, or use a warhead that can convert the gamma and neutron energy into thermal and/or kinetic energy.

Noclevername
2012-Oct-20, 11:20 PM
Somehow I knew this would come up in your threads when I mentioned that the only warheads you could realistically use would be fragmentation and hyperkinetic. Nuclear might be useful, but you'd still have to be fairly close, or use a warhead that can convert the gamma and neutron energy into thermal and/or kinetic energy.

You'd have to be close to use a nuke, but a kinetic impactor would have to be a lot closer-- touching. :)

Someting like a nuclear shaped charge would still be pretty devastating over its range. But as far as EMP is concerned, it's a bust.

Noclevername
2012-Oct-20, 11:20 PM
Somehow I knew this would come up in your threads when I mentioned that the only warheads you could realistically use would be fragmentation and hyperkinetic. Nuclear might be useful, but you'd still have to be fairly close, or use a warhead that can convert the gamma and neutron energy into thermal and/or kinetic energy.

You'd have to be close to use a nuke, but a kinetic impactor would have to be a lot closer-- touching. :)

Someting like a nuclear shaped charge would still be pretty devastating over its range. But as far as EMP is concerned, it's a bust.

Githyanki
2012-Oct-21, 01:29 AM
A nuke in space creates a lot of radiation that wipes out computer memory and kills crewmen.

Noclevername
2012-Oct-21, 01:45 AM
A nuke in space creates a lot of radiation that wipes out computer memory and kills crewmen.

Practically any manned deep-space craft will have to have signifigant radiation shielding-- the military ships in my story are specifically designed to resist radiation effects, having several layers of heavy metal, carbon and water tanks between crews and any potential radiation threat.

Githyanki
2012-Oct-21, 02:14 AM
Practically any manned deep-space craft will have to have signifigant radiation shielding-- the military ships in my story are specifically designed to resist radiation effects, having several layers of heavy metal, carbon and water tanks between crews and any potential radiation threat.

Yeah, a lot of anti-radiation shield does require a lot of energy to move it. Each deep-space craft(designed to go from planet to another) in my games has a solar-flare protection room.

Shaula
2012-Oct-21, 07:14 AM
Aren't heavy metal shields going to have appalling spallation problems?

Ara Pacis
2012-Oct-21, 09:45 AM
Aren't heavy metal shields going to have appalling spallation problems?

Do you mean from thermal expansion or Bremsstrahlung?

Shaula
2012-Oct-21, 09:50 AM
Mainly the heavy metals. I thought that for the highest energy stuff (and relativistically shifted radiation) you tended to favour lighter nuclei, because you got far less secondary nastiness.

Ara Pacis
2012-Oct-21, 09:52 AM
You'd have to be close to use a nuke, but a kinetic impactor would have to be a lot closer-- touching. :)

Someting like a nuclear shaped charge would still be pretty devastating over its range. But as far as EMP is concerned, it's a bust.

Depends on how you mean. A projectile can travel vast distances and maintain the same impact energy, but a nuke is essentially limited by the inverse square law. I don't know how well a shaped nuclear design would actually work. However, conversion of nuclear to kinetic has been proposed in SDI, IIRC (a form of Explosively Formed Penetrator), or using a "Thunderwell" design where the nuke vaporizes certain materials to create a directed blast of vapor, plasma, dust, pellets, or larger debris. A "Thunderwell" might be used as a mobile one-shot mass-driver.

Noclevername
2012-Oct-21, 12:04 PM
Aren't heavy metal shields going to have appalling spallation problems?

The thick carbon graphite layer goes on the outside, and the metal shields have PVC and kevlar-or-future-equivalent lining. I was posting tired, sorry.

cjameshuff
2012-Oct-22, 03:10 AM
You might pull it off with artificial magnetic fields, and perhaps two separate devices whose fireballs interact with each other. However, it's really rather easy to shield against EMP, and space hardware is going to be highly isolated and tolerant of electromagnetic abuse anyway due to issues like the ease of charge buildup in vacuum (think static on a dry winter day is bad?). I really don't see EMP devices being effective outside of some special circumstances (taking out large solar arrays without causing blast damage to the nearby habitat, for example).

Solfe
2012-Oct-22, 04:03 AM
What about at BLU-114/B type weapon (http://en.wikipedia.org/wiki/BLU-114/B_%22Soft-Bomb%22) (wiki link). The bomb has submunitions that release graphite fibers that short out powered devices. In the real world example, they are used on power plants. Ideally, your weapon would be a missile that first penetrates armor and then deploys the submunitions.

Shaula
2012-Oct-22, 06:28 AM
The BLU 114/b kind of requires exposed wires and high voltages, doesn't it? Dropping a graphite ribbon on insulated wires carrying a few tend of volts doesn't do a huge amount!

Noclevername
2012-Oct-22, 06:54 AM
What about at BLU-114/B type weapon (http://en.wikipedia.org/wiki/BLU-114/B_%22Soft-Bomb%22) (wiki link). The bomb has submunitions that release graphite fibers that short out powered devices. In the real world example, they are used on power plants. Ideally, your weapon would be a missile that first penetrates armor and then deploys the submunitions.

At the impact speeds typical of a space battle, I don't think such a complicated device would survive the crash intact. Anything hitting at more than 2 miles a second might as well be made of TNT.

Solfe
2012-Oct-22, 01:04 PM
At the impact speeds typical of a space battle, I don't think such a complicated device would survive the crash intact. Anything hitting at more than 2 miles a second might as well be made of TNT.

Why doesn't anyone do a stern chases in space? :)

The issue I have with 2 miles/second closure speed is - where are you fighting? In orbit - a big circle around a planet. If your weapon travels that much faster than orbital speeds, it is leaving orbit. Your weapons either needs to be so fast it can follow a straight line to the target or it needs to stay at basically orbital speeds to follow the curve of the target's orbit. If your weapon is much faster than orbital speed, it has to trace a straight line to the target. Your ranges are going to be very short which is going to subject your ship to debris that is faster than 2 miles/second which you can't dodge.

Speed is life... and death in space.

Noclevername
2012-Oct-22, 01:17 PM
Why doesn't anyone do a stern chases in space? :)

The issue I have with 2 miles/second closure speed is - where are you fighting? In orbit - a big circle around a planet. If your weapon travels that much faster than orbital speeds, it is leaving orbit. Your weapons either needs to be so fast it can follow a straight line to the target or it needs to stay at basically orbital speeds to follow the curve of the target's orbit. If your weapon is much faster than orbital speed, it has to trace a straight line to the target. Your ranges are going to be very short which is going to subject your ship to debris that is faster than 2 miles/second which you can't dodge.

Speed is life... and death in space.

Where are we fighting? All over. Planetary orbits can cover very large volumes, Earth's orbital zone for example extends out farther than the Moon, so ranges will not necessarily be very short at all, and that's not counting battles around jump points (most of which are not within planetary orbits) or if you get caught somewhere in between planets and jump points. When the fight comes to you, you fight there or die. We can't outrun the enemy ships so all we can hope for is to outgun them.

Missiles have no "range" in space; the missile might use little bits of delta-V at a time to close in and line up on a target, then use the rest all up at once to get up to strike speed. It need not fire continuously unless designed that way. And dodging debris is no harder than dodging incoming fire, and generally a fair bit easier as debris is not target-seeking.

Solfe
2012-Oct-22, 01:49 PM
Ah, I though we were in orbit.

The TV show Space Above and Beyond has a wonderful example of orbital combat. The heroes are fleeing by circumnavigating a black hole. They are told forget the event horizon, you ship can't get close enough to for it to be a problem. There is a red circle around the black hole and this circle is the minimum safe distance for the heroes ships to go. Any place inside that red circle and the ships can't escape the black hole and can't be rescued. The best part of this is, the circle is clearly stated to be a distance that has nothing to do with the black hole and every thing to do with fuel and acceleration of the ship.

The heroes are pursued by enemy fighters that are closing from behind. When the heroes accelerate to top speed, they are moving away from the red circle and opening space between the enemy. When the enemy accelerates, they dip inside the red circle. The distance between the ships is opening at first, but eventually it will close very quickly. The enemy isn't going to catch the heroes from behind, they are going to get in front of the heroes and pop up. This will prevent the heroes from maneuvering effectively. The enemy can do this because their ships have more fuel and more acceleration. One of the heroes saves the day by retro firing and diving down on the enemy. This happens to be nearly the same as the enemy's trap, they can't maneuver in any meaningful way. He succeeds in intercepting the enemy but can't escape the black hole. He doesn't bother to fire his engines until a rage laden final few moments before being ripped to pieces by tidal forces.

My general point is if you can match 2 miles/second of speed, then picking something slower should be an option. It would require slowing as you approach, but it should be possible.

Noclevername
2012-Oct-22, 02:15 PM
Ah, I though we were in orbit.

We can be, but don't confuse orbit with low orbit. As I said, the volume of space within a planet's orbit can be massive-- gazillions of cubic miles*. The Moon is in orbit and it's over a light-second away and takes a month to go around-- if we're still there in a month waiting for debris to come back around it's because we're already dead.

*As opposed to metric gazillions.


It would require slowing as you approach, but it should be possible.

Assuming the ship you approach has no point defenses and is not dodging, sure.

But the weapon is designed to minimize collateral damage. The enemy we're fighting takes collateral damage as a bonus. We may, however, have brought some along to use on the rebel colony that we were originally planning to fight, so it might see its intended use against ground targets. But in space? No. If we could land a Silly String dispenser on their hull we could far more easily send a nuke into point-blank range.

cjameshuff
2012-Oct-22, 02:28 PM
The issue I have with 2 miles/second closure speed is - where are you fighting? In orbit - a big circle around a planet. If your weapon travels that much faster than orbital speeds, it is leaving orbit. Your weapons either needs to be so fast it can follow a straight line to the target or it needs to stay at basically orbital speeds to follow the curve of the target's orbit.

Why? What's wrong with taking a trajectory that's a hyperbola or a segment of some other ellipse?



If your weapon is much faster than orbital speed, it has to trace a straight line to the target. Your ranges are going to be very short which is going to subject your ship to debris that is faster than 2 miles/second which you can't dodge.

"Very short"? The moon orbits over a light second away from Earth, and the range of possible orbits extends a good bit further than that. Geostationary orbit is about 7 Earth radii from Earth's center, making most of Earth's orbital space visible. Even objects in low Earth orbit can be in line of sight while thousands of km apart...4500 km or so for two objects both at 400 km altitude. And unless the target is subject to insane overkill, most of the debris is going to stay in a similar orbit.

Jens
2012-Oct-23, 01:11 AM
Why doesn't anyone do a stern chases in space? :)


I'm not sure, it might be a joke because of the smiley. But in space, there wouldn't be such a thing, would there? In an atmosphere you can't simply turn your airplane around, but in space you can maneuver all you want to face whichever direction you want, so would there be any meaning to "stern"?

Noclevername
2012-Oct-23, 01:13 AM
I'm not sure, it might be a joke because of the smiley. But in space, there wouldn't be such a thing, would there? In an atmosphere you can't simply turn your airplane around, but in space you can maneuver all you want to face whichever direction you want, so would there be any meaning to "stern"?

I think he was referring to the "stern chase" in The Gripping Hand, sequel to The Mote In God's Eye. It was a "stern" chase because the ships were under constant thrust, and so had to keep their tails pointed at those chasing them.

Solfe
2012-Oct-23, 04:32 AM
I think he was referring to the "stern chase" in The Gripping Hand, sequel to The Mote In God's Eye. It was a "stern" chase because the ships were under constant thrust, and so had to keep their tails pointed at those chasing them.

That at the trope that space is an ocean.

Noclevername
2012-Oct-23, 07:59 AM
Well, in my story, the U.S. Space Force draws from every service, but the Navy has greater experience with nuclear wessels vessels, so they are the de facto propulsion experts. I'm still trying to avoid SIAO tropes, though, the gunships and aerospace planes are mostly drawn from Air Force backgrounds, and the Space "Marines" in the particular task force followed in my story are a mixed force of Army Aerospace Ranger, Marine Corps Space/Ground Fast Reaction Force and a Navy SSEAL team (yes, the double S is intentional). These groups were not originally intended to fight mixed, but circumstances changed our plans radically. The current head of the Space Foce ExtraTerrestrial Planetary Surface Warfare forces is a Space Force General and overall fleet command rests with a Space Marshal, but both were based on or near Earth and our task force is out of contact, so Commodore Gregor is the acting commander of the U.S. space forces and, as the highest ranking officer left that we know of, is nominally in command of all U.N. forces in space. Getting other commanders to agree to this, especially foreign ones, is as you might expect, problematic, though the fact that most jumpships were destroyed, stranding other forces in the systems they happened to be in, gives him some leverage. However, Gregor grew up in the Space Force and has never served wet-Navy, he knows how to fight in space, and that it's not an ocean.

Ara Pacis
2012-Oct-23, 08:32 AM
That at the trope that space is an ocean.

There may be reasons for constant thrusting. You may not want the enemy to get closer where their lasers can have enough intensity per area to do damage. You may want to use your exhaust to foul their weapons and sensors. You may want to get somewhere as fast as possible. You may want to be able to "drop" something behind you like a mine to damage the ship following you or force it to expend fuel/propellant avoiding it, expend chemical laser fuel to damage it, to prevent the other vessel from coming up along side to target the broadside of a vessel if the narrow front and rear of the vessel are heavily armored, etc.