Destructive power of starships

[Lazar]

Here's a thing that dawned on me about interstellar or relativistic vessels as commonly depicted in sci-fi: couldn't just one of these, traveling at speed, devastate or destroy a planet? If you look at something like Star Trek or Star Wars, you have great numbers of these ships milling about near inhabited planets, some of them in private hands. How would you prevent some lone nut from crashing his ship into the Earth at 1/4 lightspeed (i.e. 'full impulse'), or even at warp speed? Why did the Galactic Empire pour so much money into the Death Star and its superlaser, when they could liquefy any planet's surface merely by tossing a few mothballed Star Destroyers at it?

[Aliquantic]

Isn't it the same problem as relativistic weapons (Wikipedia)? Anything travelling at a substantial portion of the speed of light is very, very deadly, and you don't even need to sacrifice a starship, but it's even less "cool" in story terms!

[Soralin]

Indeed, I suggest looking through the Atomic Rockets site: http://www.projectrho.com/rocket/ (topic list in the upper right) It has a lot of interesting information on the physics of this sort of thing, and how it relates to science fiction. For example:

http://www.projectrho.com/rocket/prelimnotes.php

Another annoying fact is that realistic spacecraft propulsion systems are incredibly weak. They will take forever to push the ship to anywhere farther than, say, Luna. So SF authors try to jazz things up by postulating more powerful propulsion systems. Alas, they then run full tilt into Jon's Law for SF authors.

Jon's Law for SF authors is closely related to Niven's Kzinti Lesson. It states: "Any interesting space drive is a weapon of mass destruction. It only matters how long you want to wait for maximum damage." It goes on to say: "Interesting is equal to 'whatever keeps the readers from getting bored'".

As an example, a spacecraft with an ion drive capable of doing a meager 0.0001g of acceleration may be scientifically realistic and the exhaust is relatively harmless. However, to most of the audience it will not be interesting. "Nine months just to travel to Mars? How boring!"

The author, not wanting his book sales to go flat, hastily re-fits the hero's spacecraft with a fusion drive. The good news is that the ship can make it to Mars in twelve days flat. The bad news is that the ship's exhaust is putting out enough terawatts of energy to cut another ship in two, or make the spaceport look like it was hit by a tactical nuclear weapon.

The author can still use the drive, but must consider the logical ramifications of the wide-spread civilian availability of the equivalent of thermonuclear weapons. Consider: the more energy the drive contains , the worse the damage if an accident occurs. How would you like to have the captain of the Exxon Valdez skippering a tramp freighter with an antimatter drive? That brilliant mushroom cloud you see marks the former location of Clinton-Sherman spaceport. The more devastation a propulsion system can wreck, the shorter the leash the captains will be on.

So one of the logical ramification is that if drives are too powerful, there won't be any colorful tramp freighters or similar vessels. As a matter of fact, civilian spacecraft will probably by law be required to have a remote control self-destruct device that the orbital patrol can use to eliminate any ship that looks like it is behaving erratically or suspiciously.

Most of the nasty effects of Jon's Law are due to the propulsion system's exhaust. The presence of an exhaust is because rockets use Newton's Third Law (the one about action with equal and opposite reaction). Canny SF authors postulate some kind of hand-waving reactionless drive in an attempt to avoid Jon's Law. Reactionless means no exhaust is required. You feed electricity in, and the ship is magically accelerated. The "gravitic impellers" from David Weber's HONOR HARRINGTON series is an example of a reactionless drive.

Unfortunately such canny SF authors then run smack dab into Burnside's Advice. Burnside's Advice is that Friends Don't Let Friends Use Reactionless Drives In Their Universes. The trick is making a reactionless drive that doesn't give you the ability to shatter planets with the Naval equivalent of a rowboat (which would throw a big monkey wrench into the author's carefully crafted arrangement of combat spacecraft). Reactionless drives, with no fuel/propellant constraints, will give you Dirt Cheap Planet Crackers. If you have a reactionless drive, and stellar economics where most of the common tropes exist (privately owned tramp freighters), you also have gravitic drive missiles. And avoiding Planet Crackers Done Real Cheap is almost impossible to justify on logical grounds, the SF author is faced with quite a daunting task.

[bigglesworth]

And since an Imperial I class Star Destroyer puts out 2,300g of acceleration, that puts it firmly in the camp of the planet destroying.

On the other hand, I suppose that the hypermatter used to power the Death Star might have been cheaper than even a mothballed Star Destroyer which could be dismantled and recycled.

[Kang]

Funny thing is that when Han Solo goes on about the precision necessary for a hyperspace jump he says something along the lines of: «You do it wrong, you could end up crashing into a planet!», obviously referring to how that would be bad for them, but I never quite questioned how that might be bad for the planet as well.

[brume]

And then there's Dune where the ships don't move at all as space is somehow warped around them. A similar idea in the movie Event Horizon, but with less woo and spice. Maybe Deepak Chopra can invent us a quantum vibration motor?

[ikrase]

Possibly in hyperspace, interactions are less, or KE is actually low, or the ship is insubstantial, or something. I seem to remember that you need to worry about gravity, not solid objects, in SW.

[Xanthir]

I wonder if you could still get reactionless drives to work if you included a velocity-limiting effect of some kind. That is, a drive with power consumption X can't push you faster than velocity V.

Hmm. Seems like that breaks relativity, though. Damn.

[nitePhyyre]

The ships use a momentumless drive that warps space around the ship, rather than having the ship move through space. Then all you have to say is that when you get too close to some gravity well, the drive can no longer fold space properly.

[Lazar]

The ships use a momentumless drive that warps space around the ship, rather than having the ship move through space. Then all you have to say is that when you get too close to some gravity well, the drive can no longer fold space properly.

I suppose that's a decent way to prevent Star Trek ships from warping into planets, but they still use fusion rockets to travel at relativistic sublight velocities. In any case, Star Trek has a pretty terrible track record of understanding movement in space. They've depicted ships stopping, ships reversing, and ships using constant thrust to maintain a consant speed - and opponents always meet each other on a horizontal plane.

[gmalivuk]

You could handwave some kind of "suppressor" of nuclear reactions near spaceports, and have ruthlessly enforced no-fly zones for everywhere else that's near a planet but outside the dampening field. And then, if you want FTL, base it on wormholes or a gate network instead of controlled travel through hyperspace, or use the typical "can't warp in a gravity well" excuse to prevent mass destruction near massive objects.

[nitePhyyre]

Actually, when you think about it, the gravity well defense doesn't make much sense. If you wanted your warp ship to not be able to crash into Mars, that would preclude warp throughout the solar system. You could have the warp field break down if there are too many particle collisions instead.

[yurell]

It'd be an interesting setting for a story if people don't live on planets any more precisely because of this issue — a five-minute long war would be pretty convincing for everyone involved the danger of dumping all your eggs in one basket like that.

[gmalivuk]

If you wanted your warp ship to not be able to crash into Mars, that would preclude warp throughout the solar system.

Yep. Which is why the standard trope is to have to come out of warp well outside the system, and then use fusion rockets from there.

[nehpest]

In any case, Star Trek has a pretty terrible track record of understanding movement in space. They've depicted ships stopping, ships reversing, and ships using constant thrust to maintain a consant speed - and opponents always meet each other on a horizontal plane.

Star Trek gets it right and wrong at the same time - in one TNG episode, Picard orders the tractor beam disengaged as a power saving measure, since the ship they were towing is already moving in the right direction at a satisfactory speed. Amusingly, the rest of the onscreen crew is amazed by this insight. Clearly, they don't teach Newtonian mechanics anymore in the 24th century.

[BlackHatSupport]

The ships use a momentumless drive that warps space around the ship, rather than having the ship move through space. Then all you have to say is that when you get too close to some gravity well, the drive can no longer fold space properly.

I suppose that's a decent way to prevent Star Trek ships from warping into planets, but they still use fusion rockets to travel at relativistic sublight velocities. In any case, Star Trek has a pretty terrible track record of understanding movement in space. They've depicted ships stopping, ships reversing, and ships using constant thrust to maintain a consant speed - and opponents always meet each other on a horizontal plane.

You noticed that, too?

And notice how phasers, (supposedly "pure energy") take forever to knock down enemy shields?

Why not set up a shield that absorbs the energy of a weapons blast and use it to strenghten itself?

[Tomlidich]

all this makes me wonder why captain kirk was not court marshalled.

because theoretically he endangered many planets over the course of the show by losing direct control of his ship or allowing it to fall into the hands of unqualified or malicous persons.

[nehpest]

all this makes me wonder why captain kirk was not court marshalled.

because theoretically he endangered many planets over the course of the show by losing direct control of his ship or allowing it to fall into the hands of unqualified or malicous persons.

He stood a court martial. They busted him down to Captain (from Admiral). Watch the fourth movie, and try not to cringe at the tacky 80s-ness being rained down upon you.

[Tomlidich]

all this makes me wonder why captain kirk was not court marshalled.

because theoretically he endangered many planets over the course of the show by losing direct control of his ship or allowing it to fall into the hands of unqualified or malicous persons.

He stood a court martial. They busted him down to Captain (from Admiral). Watch the fourth movie, and try not to cringe at the tacky 80s-ness being rained down upon you.

well ok, i mean court marshalled AGAIN

[Lazar]

You noticed that, too?

I maintain that no one can bash Star Trek as well as a disenchanted ex-Trekkie (i.e. me). I seriously lived and breathed Trek as a child - and I still enjoy watching it -, but nowadays I could write an entire book on its flaws and inconsistencies.

[Tomlidich]

You noticed that, too?

I maintain that no one can bash Star Trek as well as a disenchanted ex-Trekkie (i.e. me). I seriously lived and breathed Trek as a child - and I still enjoy watching it -, but nowadays I could write an entire book on its flaws and inconsistencies.

you mean like how the captain always reverses the polarity on things?
being an electrical engineer, that part always bugs me *twitch* *shudder* *spasm*

[Macbi]

I was reading the Feynman Lectures on Physics the other day, and he actually uses the phrase "reverse the polarity". It was great.

[Tomlidich]

I was reading the Feynman Lectures on Physics the other day, and he actually uses the phrase "reverse the polarity". It was great.

*TWITCH*

edit: .....you made me drop my traffic cone. you bastard.

[BlackHatSupport]

I maintain that no one can bash Star Trek as well as a disenchanted ex-Trekkie (i.e. me). I seriously lived and breathed Trek as a child - and I still enjoy watching it -, but nowadays I could write an entire book on its flaws and inconsistencies.

If you write that book I will buy it.


Show a ex-Trekkie a piece of spectacular machinery, they spend all day tyring to make it fail. Believe me.


Usually with phasers.

[nehpest]

BHS: The Physics of Star Trek may prove to be of interest to you. Also, Krauss wrote Beyond Star Trek, which develops the same topic with examples from other sci-fi scenarios.

[Turtlewing]

you mean like how the captain always reverses the polarity on things?
being an electrical engineer, that part always bugs me *twitch* *shudder* *spasm*

To be fair they spend a lot of time standing on the wrong side of consoles looking at thing upside down. I'd imagine it's pretty easy to plug things in backwards in an environment like that.

[Tomlidich]

you mean like how the captain always reverses the polarity on things?
being an electrical engineer, that part always bugs me *twitch* *shudder* *spasm*

To be fair they spend a lot of time standing on the wrong side of consoles looking at thing upside down. I'd imagine it's pretty easy to plug things in backwards in an environment like that.

still, no excuses. when it is digital control, there should probably be some failsafe in there like the windows "are you sure" popup.

especially when it just breaks things half the time.

[Soralin]

still, no excuses. when it is digital control, there should probably be some failsafe in there like the windows "are you sure" popup.

especially when it just breaks things half the time.

[TheShadowFog1]

still, no excuses. when it is digital control, there should probably be some failsafe in there like the windows "are you sure" popup.

especially when it just breaks things half the time.

Exactly.

[Technical Ben]

You could handwave some kind of "suppressor" of nuclear reactions near spaceports, and have ruthlessly enforced no-fly zones for everywhere else that's near a planet but outside the dampening field. And then, if you want FTL, base it on wormholes or a gate network instead of controlled travel through hyperspace, or use the typical "can't warp in a gravity well" excuse to prevent mass destruction near massive objects.

I like the last one. Perhaps mixing in the neutrino effect of not being able to interact with matter. I'd think making it too power intensive near large planets and unable to effect matter while in "hyperspace" or "warp speed". It would still allow you to drop out of warp right on someone's noes though.

[Tomlidich]

You could handwave some kind of "suppressor" of nuclear reactions near spaceports, and have ruthlessly enforced no-fly zones for everywhere else that's near a planet but outside the dampening field. And then, if you want FTL, base it on wormholes or a gate network instead of controlled travel through hyperspace, or use the typical "can't warp in a gravity well" excuse to prevent mass destruction near massive objects.

I like the last one. Perhaps mixing in the neutrino effect of not being able to interact with matter. I'd think making it too power intensive near large planets and unable to effect matter while in "hyperspace" or "warp speed". It would still allow you to drop out of warp right on someone's noes though.

of course this makes me wonder what happens when you hit one of the few particles of matter distributed out through space? would you drop out of warp? also, would you not be able to start warp as these particles are pretty much everywhere?

[nehpest]

You could handwave some kind of "suppressor" of nuclear reactions near spaceports, and have ruthlessly enforced no-fly zones for everywhere else that's near a planet but outside the dampening field. And then, if you want FTL, base it on wormholes or a gate network instead of controlled travel through hyperspace, or use the typical "can't warp in a gravity well" excuse to prevent mass destruction near massive objects.

I like the last one. Perhaps mixing in the neutrino effect of not being able to interact with matter. I'd think making it too power intensive near large planets and unable to effect matter while in "hyperspace" or "warp speed". It would still allow you to drop out of warp right on someone's noes though.

of course this makes me wonder what happens when you hit one of the few particles of matter distributed out through space? would you drop out of warp? also, would you not be able to start warp as these particles are pretty much everywhere?

Clearly, the warp field evacuates the surrounding space of matter, providing a gravity-well-free environment for transit. /handwave

[Technical Ben]

Tomlidich neutrinos barely interact with the earth. So if your fictional warp drive effectively turns the craft into a neutrino cloud, it's not going to hit anything.
When you drop out of warp, your acceleration and speed is "normal" and back below c. So no danger from relativistic collisions.

[Lazar]

Clearly, the warp field evacuates the surrounding space of matter, providing a gravity-well-free environment for transit. /handwave

Trek ships are equipped with deflector shields that deflect particles and debris during warp and impulse flight (with the implication that the warp field does not clear matter out of the way). So our "why can't ships warp into planets" handwave should be that only things with significant gravity can obstruct a warp field. (If we think about the mechanics of bending space, this may legitimately make sense.)

Really, given that warp travel is non-Newtonian, it's much easier to explain away the possible dangers. The real problem is impulse propulsion, which we know can move ships at relativistic velocities. I mean, one runaway freighter could wipe out the Earth with just a moment's warning. As best I can guess, they would either have to have fast ships ready to tractor-beam it away, or the ability to shoot enough photon torpedoes at it that it's not merely broken up but vaporized.

[nehpest]

True, Lazar. My point was only the ease of creating the handwave, rather than the details of one. As for for the runaway freighter scenario, I seem to remember Star Trek IV mentioning planet-wide shields - I'll have to watch it again later to confirm

[BlackHatSupport]

Put it this way.

1) Fusion drives aren't actually too dangerous in space

2) FTL drives can be dangerous to planets (i.e. warp droves or stellar folding)

3) Every time Kirk poarized the hull, a little bit of me died.

[Meteorswarm]

3) Every time Kirk poarized the hull, a little bit of me died.

What? Why? There's lots of ways to interpret that that make sense.

Moving charge to an internal capacitor, sending off a charged particle beam, just redistributing charge along the hull to give it poles, etc.

[BlackHatSupport]

What? Why? There's lots of ways to interpret that that make sense.

Moving charge to an internal capacitor, sending off a charged particle beam, just redistributing charge along the hull to give it poles, etc.

It's less that and more the "our hull is polarized! They cannot detect us!" *shudder*

[MHD]

OTTO: FTL drives then...

Did you read up on why they case TIME PARADOXES?

I'd say that is a bit more dangerous...

[Gagundathar The Inexplicable]

Let me expand the venue a bit, if y'all will allow.

The starship in Independence Day would have completely disrupted the entire planet's ecosystem.
Why, you may ask? Well, given how immense it was, and how close to the planet (after all you could see the dang thing hanging there in orbit), its very gravity would have been a destructive tidal force. Just being there would have caused immense damage.

It is similar to why the Death Star didn't just orbit Alderaan and screw with their ecosystem.
Or why ... heck, a bunch of other scenarios come to mind.
But, I think I have made my point.