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Jim Starluck
2009-Dec-14, 09:47 AM
The latest post (http://blogs.discovermagazine.com/badastronomy/2009/12/13/wise-to-launch-monday-morning/) on Phil's blog, about the Wide-Field Infrared Survey Explorer about to launch, reminded me of something. Specifically, a question I've been meaning to ask here: how much infra-red astronomy has been done on the asteroids within our solar system? How detailed of an understanding do we have of their temperatures and whatnot?

The reason I ask... In my spare time I've been tinkering away with a sci-fi story. Now while there are parts of it that are going to do unspeakable things to physics, I'm otherwise trying to keep things somewhat realistic. For example, There Is No Stealth In Space. (http://tvtropes.org/pmwiki/pmwiki.php/Main/StealthInSpace) It is not a matter of "if" a spaceship will be detected, it is a matter of "when". Even shut down in entirely passive mode, a thorough enough survey will see it shining like an infra-red beacon against the blackness sooner or later, and the sensor systems aboard other spaceships have more in common with current-day astronomical instruments than anything else.

One countermeasure I've been considering a viable option to defeat this is for a ship to use an asteroid as a heat sink. You park your ship next to one, bore a hole deep inside of it and instead of radiating all your waste heat out into space, you pump it deep into the asteroid. Of couse, eventually it will get hot enough that you'll have to pick up and move to a new one, because now the asteroid itself is radiating enough heat to be noticeable.

This is why I ask the question. A plot point for aforementioned story is an alien spacecraft(s) employing this method of concealment within our own solar system, thus remaining undetected.* But this would obviously not work if we've taken some very close looks at asteroids and would be able to tell if a number of them were hotter than the rest. WISE seems intended to do exactly this, and it got me wondering what kind of studies have been done in this field before.

So how closely have we looked at all those rocks tumbling around out there? Do we know how hot they are, and if so, to within what degree of accuracy? How hot could an asteroid get before it would stand out significantly, and what quantity of heat energy would that entail being dumped into it?






* - No, they have not been abducting people. Don't be silly.

Hungry4info
2009-Dec-14, 09:50 AM
Spitzer has been aimed at a few asteroids to gather spectra and what-not. Aiming Spitzer at, say, any random KBO, it's heavily unlikely that a spacecraft could be distinguished from the asteroid's own infrared radiation.

If the asteroid appears brighter in infrared because of the spacecraft's heat, then, because the spacecraft's existence is unknown, it will be assumed that the asteroid is just larger than it actually is (or having a lower albedo than most asteroids, if it appears visibly darker than expected for its IR output).

So, assuming that the IR output of the spacecraft made a difference, anyone using a telescope would go with the "larger, dark asteroid" hypothesis over a "normal asteroid with a spacecraft" one. So your spacecraft should be safe.

IsaacKuo
2009-Dec-14, 03:22 PM
The basic idea that "there is no stealth in space" is really just a rule of thumb for the uninitiated. In fact, there are a lot of ways to deceive enemy sensors in space, it's just that there isn't a way to do what "stealth" does. That is, "stealth" is like a cloaking device that lets you sneak around in space with relative impunity, like a modern day stealth bomber or nuclear submarine.

In fact, you could pretty easily launch small passive sensor drones far away from the enemy which for all practical purposes will never be detected by the enemy--so long as the enemy doesn't get too close.

It gets difficult to be "stealthy" when you want to do one or more of the following:

1) Be "big"

2) Move somewhere

3) Shoot a weapon

Your idea of hiding on an asteroid will work, but there are some limitations.

First, you have to get to the asteroid in the first place. You have to not only launch yourself toward the asteroid unnoticed, but you also have to LAND on the asteroid unnoticed. This is HARD to do unless you started off pretty close to the asteroid's position and velocity to begin with.

Second, you're now tied to the asteroid. You can operate some high power hardware, using the asteroid as a heat sink...but so what? You'd still have to leave in order to perform some sort of military mission. This may not be an issue for your aliens, of course, depending on what they want to do. Or it may be an issue. Anyway, it's part of what's meant by "there's no stealth in space" because the saying is related to military "stealth" technology for military purposes.

Anyway, there's no inherent reason why a spacecraft sitting on top of an asteroid would ever be detected by increased heat radiation. One of the most practical power sources for spacecraft is solar power. As long as the spacecraft uses solar power, the amount of waste heat "generated" by the spacecraft will be equal to the amount of solar radiation "stolen" from the asteroid by the shadow of the spacecraft. In other words, the total amount of radiation from the asteroid is more or less unchanged.

Jim Starluck
2009-Dec-14, 06:14 PM
Spitzer has been aimed at a few asteroids to gather spectra and what-not. Aiming Spitzer at, say, any random KBO, it's heavily unlikely that a spacecraft could be distinguished from the asteroid's own infrared radiation.

If the asteroid appears brighter in infrared because of the spacecraft's heat, then, because the spacecraft's existence is unknown, it will be assumed that the asteroid is just larger than it actually is (or having a lower albedo than most asteroids, if it appears visibly darker than expected for its IR output).

So, assuming that the IR output of the spacecraft made a difference, anyone using a telescope would go with the "larger, dark asteroid" hypothesis over a "normal asteroid with a spacecraft" one. So your spacecraft should be safe.

This is mostly what I figured; that if we noticed an asteroid or group of asteroids being hotter than the rest, "alien spacecraft" would not be high on the list of probable explanations.





First, you have to get to the asteroid in the first place. You have to not only launch yourself toward the asteroid unnoticed, but you also have to LAND on the asteroid unnoticed. This is HARD to do unless you started off pretty close to the asteroid's position and velocity to begin with.

Fortunately, I already have a convenient explanation for this. To reach the asteroids, they employed an Alcubierre-like FTL drive (one of aforementioned unspeakable violations of physics). Since it involves the warping of spacetime and not the ejection of hot, high-velocity exhaust, it is much, much less detectable to Earth's observations. A telescope would have to be pointed directly along its path of travel and observe the light from distant stars being occluded and distorted by the intense gravity fields.

It also allowed them to arrive at rest relative to the asteroid, which made landing pretty easy.


Second, you're now tied to the asteroid. You can operate some high power hardware, using the asteroid as a heat sink...but so what? You'd still have to leave in order to perform some sort of military mission. This may not be an issue for your aliens, of course, depending on what they want to do. Or it may be an issue. Anyway, it's part of what's meant by "there's no stealth in space" because the saying is related to military "stealth" technology for military purposes.

Their mission in our solar system is twofold. First and foremost, it is essentially a giant anthropological experiment. They know how their own civilization(s) developed and evolved, and are curious to see how an alien life form's civilization(s) does the same. When they first found Earth back in the late 14th century they determined that we were, in the relatively near future, going to move through one of the most dynamic phases of growth--the rise of science, industry and technology--and they were keen to see how our species handled that, compared to their own. They especially wanted to see how we handled nuclear weapons, because their own ancestors nearly wiped themselves out in a WWIII-style ICBM exchange and they're still suffering something like racial guilt over that.

Second, they wanted to station a number of spacecraft within our solar system for our own protection. They know of another nearby alien species who would not be nearly so benign if they found Earth, so they've been intentionally interdicting our star system for centuries. It also handily deals with the Fermi Paradox.


Anyway, there's no inherent reason why a spacecraft sitting on top of an asteroid would ever be detected by increased heat radiation. One of the most practical power sources for spacecraft is solar power. As long as the spacecraft uses solar power, the amount of waste heat "generated" by the spacecraft will be equal to the amount of solar radiation "stolen" from the asteroid by the shadow of the spacecraft. In other words, the total amount of radiation from the asteroid is more or less unchanged.

Ahhh. This had not occured to me... though it might be difficult to put into use, given the asteroid would most likely be rotating and they would be moving in and out of its shadow. Still, definitely something to consider.

IsaacKuo
2009-Dec-14, 07:48 PM
Ahhh. This had not occured to me... though it might be difficult to put into use, given the asteroid would most likely be rotating and they would be moving in and out of its shadow. Still, definitely something to consider.
The solar panels could keep batteries topped up; the batteries are used during the "night".

But anyway, if they really want to avoid detection from us Earthlings, then I suggest they avoid the main solar system altogether. It would be about as easy to keep an eye on us using large telescopes in the Oort cloud, and the chances of detection would be practically zero.

The problem with hanging out among main belt asteroids is that it's "just barely" outside our range of detection. We've started sending missions to asteroids, and we've started getting a good close look at some of them. Why would aliens bent on avoiding detection risk it? They might be detected just by being unlucky, or they might be detected in a few decades or a few centuries after we've sent mining missions to the asteroids.

If they hang out in the Oort cloud, then chances are good that they'll avoid detection even after we've developed interstellar colonization capability. They could stick around for billions of years and avoid detection, unless we specifically search for them.

Messier Tidy Upper
2009-Dec-14, 10:17 PM
The latest post (http://blogs.discovermagazine.com/badastronomy/2009/12/13/wise-to-launch-monday-morning/) on Phil's blog, about the Wide-Field Infrared Survey Explorer about to launch, reminded me of something. Specifically, a question I've been meaning to ask here: how much infra-red astronomy has been done on the asteroids within our solar system? How detailed of an understanding do we have of their temperatures and whatnot?

The reason I ask... In my spare time I've been tinkering away with a sci-fi story. Now while there are parts of it that are going to do unspeakable things to physics, I'm otherwise trying to keep things somewhat realistic. For example, There Is No Stealth In Space. (http://tvtropes.org/pmwiki/pmwiki.php/Main/StealthInSpace) It is not a matter of "if" a spaceship will be detected, it is a matter of "when". Even shut down in entirely passive mode, a thorough enough survey will see it shining like an infra-red beacon against the blackness sooner or later, and the sensor systems aboard other spaceships have more in common with current-day astronomical instruments than anything else.

One countermeasure I've been considering a viable option to defeat this is for a ship to use an asteroid as a heat sink. You park your ship next to one, bore a hole deep inside of it and instead of radiating all your waste heat out into space, you pump it deep into the asteroid. Of couse, eventually it will get hot enough that you'll have to pick up and move to a new one, because now the asteroid itself is radiating enough heat to be noticeable.

This is why I ask the question. A plot point for aforementioned story is an alien spacecraft(s) employing this method of concealment within our own solar system, thus remaining undetected.* But this would obviously not work if we've taken some very close looks at asteroids and would be able to tell if a number of them were hotter than the rest. WISE seems intended to do exactly this, and it got me wondering what kind of studies have been done in this field before.

So how closely have we looked at all those rocks tumbling around out there? Do we know how hot they are, and if so, to within what degree of accuracy? How hot could an asteroid get before it would stand out significantly, and what quantity of heat energy would that entail being dumped into it?

* - No, they have not been abducting people. Don't be silly.

Nice idea.

Space is big and asteriods are common &, yes, I can see this working well as long as they don't draw attention to themslves.

As far back as the IRAS (InfraRed Astronomical Satellite) mission in 1983 (http://en.wikipedia.org/wiki/IRAS ) IR has been used to study asteroids - example, IRAS discovered Phaeton the source of the Geminid meteor shower (http://en.wikipedia.org/wiki/3200_Phaethon ) and two other asteroids 3728 IRAS and 1983 QG. It could be ironic if one of those was your aliens cover! :lol:

I would probably rule out as hiding places the asteroids we've already checked up close - definitely Eros and probably also Gaspra, Ida, Mathilde, Itokawa, etc .. But one cool dilemmna could be if the chosen asteroid is by incredibly improbable chance the target of an upcoming human spaceprobe visit. :lol:

I agree with Isaac Kuo that the Oort cloud or maybe the closer Edgweworth-Kuiper belt may be even better although, of course, more distant.

Another possibility is that the alien ship could, from the outside, just appear to be an asteroid a la many "generation ship" ideas.

There's also the fact that the largest asteroids eg. Ceres, Vesta, Pallas, Hygeia are almost dwarf planets (well Ceres is one!) so they'd have some gravity and a larger shielding area. On the downside, they'd be a bit more conspicuous and are more likely to draw human attention eg. the Dawn mission currently en route to Ceres and Vesta. However, you could (& durnnit I'm working on a story with this idea myself) burrow *into* the putative ocean on Ceres as that's meant to be mostly ice with an iron core and a dusty crust.

Anyhow, great idea & I'd love to read the book when its done. :)

Jim Starluck
2009-Dec-14, 10:26 PM
The problem with more distant hiding-spots is with the FTL drive. The only way to detect one is to pick up the gravity waves it throws off, and they propogate at lightspeed while the FTL spacecraft is moving, well, FTL. It'd be like trying to track a supersonic aircraft with sonar--you'll only ever detect it after it's passed you by. They need to be within a few light-minutes of Earth if they want to have any chance of intercepting an intruding ship before it does something highly unpleasant for humanity. If they're hanging out in the Kuiper Belt or Oort Cloud, it would be at least hours, and possibly days, before they would detect any kind of intruder--way too late.

Also, since they've been monitoring us for so long, they'd have had plenty of time to translate our languages and listen in on communications. If NASA or some other space agency planned a mission to an asteroid they were hiding on, they'd hear about it through our own news networks or whatnot and just move before it got there, since such missions would take years of preparation.

They're also interested in eventually making contact with us, so by the time we've got interstellar capability of our own they wouldn't be hiding anyway.

Messier Tidy Upper
2009-Dec-14, 10:39 PM
You may also want to check this article - 'In Search of Dark Asteroids and Other Sneaky Things' found via the Wide Field Survey Explorer Wiki-page :

http://science.nasa.gov/headlines/y2009/15sep_ninjaastronomy.htm

BTW. Elapsed mission time for WISE is now 8 hours -its first working day completed and no rest or play for our tireless robot observatory! :lol:

IsaacKuo
2009-Dec-14, 10:55 PM
The problem with more distant hiding-spots is with the FTL drive. The only way to detect one is to pick up the gravity waves it throws off, and they propogate at lightspeed while the FTL spacecraft is moving, well, FTL. It'd be like trying to track a supersonic aircraft with sonar--you'll only ever detect it after it's passed you by. They need to be within a few light-minutes of Earth if they want to have any chance of intercepting an intruding ship before it does something highly unpleasant for humanity. If they're hanging out in the Kuiper Belt or Oort Cloud, it would be at least hours, and possibly days, before they would detect any kind of intruder--way too late.
If this is a concern, then it's impossible to protect Earth from just one point.

You'd need to have a number of fast patrol ships stationed in all directions--probably in the Oort cloud but perhaps even further out.

Even if you're very close to Earth, then a single patrol ship won't do at all. If the intruder comes in from any direction except almost directly past the patrol ship, it will arrive at Earth before the patrol ship even sees the intruder. For example, if the intruder FTL drive is capable of 10x lightspeed, then the patrol ship would only see the intruder before it arrives at Earth if it came within 6 degrees of the patrol ship. Assuming the intruder is unaware of the existence or location of the patrol ship, the patrol ship has only a 0.25% chance of even seeing the intruder before it arrives at Earth.

And here's the kicker--because it's so close to Earth, it has almost no time to react to the intruder! If the patrol ship were further out, then it would have more time to rev up its drive and catch up with the intruder. The further out, the better.

So, if the intruder FTL drive's are capable of 10x lightspeed, you'd need a patrol force of at least four hundred fast ships stationed out in the Oort cloud or beyond.

publiusr
2009-Dec-15, 12:39 AM
400 ships isn't unreasonable.

Jim Starluck
2009-Dec-15, 06:42 AM
If this is a concern, then it's impossible to protect Earth from just one point.

You'd need to have a number of fast patrol ships stationed in all directions--probably in the Oort cloud but perhaps even further out.

Even if you're very close to Earth, then a single patrol ship won't do at all. If the intruder comes in from any direction except almost directly past the patrol ship, it will arrive at Earth before the patrol ship even sees the intruder. For example, if the intruder FTL drive is capable of 10x lightspeed, then the patrol ship would only see the intruder before it arrives at Earth if it came within 6 degrees of the patrol ship. Assuming the intruder is unaware of the existence or location of the patrol ship, the patrol ship has only a 0.25% chance of even seeing the intruder before it arrives at Earth.

And here's the kicker--because it's so close to Earth, it has almost no time to react to the intruder! If the patrol ship were further out, then it would have more time to rev up its drive and catch up with the intruder. The further out, the better.

So, if the intruder FTL drive's are capable of 10x lightspeed, you'd need a patrol force of at least four hundred fast ships stationed out in the Oort cloud or beyond.

Yes, it's impossible to protect Earth entirely. As in, if an enemy ship wants to get near it they can't prevent it from doing so. Both sides' FTL drives are of comparable speeds--around 300 c for intra-system travel--so even if they do detect an intruder before he's already arrived, they won't be able to catch up with him.

What they can do, however, is ensure that such an intruder won't have much time to do anything after he arrives at Earth. They have roughly 8-12 dedicated sentry ships in the solar system and keep at least one ship stationed on an asteroid within a couple light-minutes of Earth at all times. Each ship is equipped with tiny, one-use FTL message pods that are pre-programmed to jump to the location of all the other ships and sound the alarm. If anything ever jumps directly to Earth, all sentries scramble and converge on it.

Incidentally, the combination of the FTL drive and SOL sensors means that any ship can come under attack with little to no warning, so their crews are trained and ships are built to go from idle to combat-ready in seconds.





You may also want to check this article - 'In Search of Dark Asteroids and Other Sneaky Things' found via the Wide Field Survey Explorer Wiki-page :

http://science.nasa.gov/headlines/y2009/15sep_ninjaastronomy.htm



Yes, quite handy. This is why the mission caught my interest: because it could fit into the plot as the first hint humans would've gotten that there's something funny going on with the local space-rocks. Sure, they probably won't figure it out, but when contact is finally established all the astronomers can go "Ah-HA! That's what it was!" with great satisfaction. :p

IsaacKuo
2009-Dec-15, 03:44 PM
Both sides' FTL drives are of comparable speeds--around 300 c for intra-system travel--so even if they do detect an intruder before he's already arrived, they won't be able to catch up with him.

What they can do, however, is ensure that such an intruder won't have much time to do anything after he arrives at Earth.
Eh...good luck with that. With 300c capability and so few sentry ships, it's extremely unlikely the intruder would be detected until well after they had already destroyed Earth. Or landed on it, or whatever.

If the intruder landed on Earth, then you could see the reentry fireball (as well as people on Earth), but once they land they'd be hard to find/track. This depends on the terrain, of course. But if they land somewhere like New York City or a redwood forest, there's just too much tall cover.

Incidentally, the combination of the FTL drive and SOL sensors means that any ship can come under attack with little to no warning, so their crews are trained and ships are built to go from idle to combat-ready in seconds.
It's hard to imagine a scenario where a ship would have any warning at all.

There are two basic possibilities--either the ship is attacked while sitting around sublight, or it is attacked while in motion.

If the ship is sitting around at sublight, then the enemy sees the ship and simply launches an FTL missile at it. Your ship never sees it coming. Boom.

If the ship is moving, then the enemy can only see you if he happens to run into your light wake. If so, then the enemy can try to catch up with you and/or launch a fast FTL missile at you. Either way, you never see it coming. Boom.

chornedsnorkack
2009-Dec-15, 07:14 PM
That depends on whether there are such things as FTL missiles. Or how practical and affordable FTL drives are.

IsaacKuo
2009-Dec-15, 07:21 PM
An FTL missile is just an unmanned FTL vehicle designed to home in on a target and destroy it (along with itself).

If an FTL "ship" is possible, then so is an FTL "missile".

chornedsnorkack
2009-Dec-15, 09:11 PM
How much information does a FTL moving ship (aliened or unaliened) get about its surroundings?

Jim Starluck
2009-Dec-16, 01:03 AM
How much information does a FTL moving ship (aliened or unaliened) get about its surroundings?

Zero. They are totally blind while using the FTL drive; they also can't be detected by any way other than picking up the gravity of the drive field itself. Furthermore, they can't change vector while the drive is active, as the gravitational shear would rip the ship apart. The only maneuver they can make at all would be to shut down the drive earlier than intended.

FTL missiles are certainly possible... but not practical. For one thing, the FTL drive can't go from a standstill to 300c instantaneously, or vice-versa. It has to ramp its strength up and down at both ends of the trip, or the drive can fail catastrophically (such failures can often be rather vigorous, i.e. "kaboom"). The acceleration isn't linear; a ship spends a lot more time going from lightspeed to stop than it does going from 1c to 300c. As the ship or missile or whatever is slowing to a stop, there's a short span of time during which it is traveling slower than the gravity waves the drive field gives off. This time is consistent regardless of the size of the ship or missile. If you're heading directly towards another ship, it will have roughly seven-and-a-half seconds within which it can see you before you arrive. That's how much time any ship has to react.

Also, the drive field is not entirely stable. It requires energy to maintain, proportional to how much mass is inside it. If you add a whole lot of mass real quick--like, say, your FTL ship/missile runs into another ship or a large enough chunk of space debris or something--the drive will overload and burn itself out (see aforementioned "vigorous" failure). So if you try to hit a target with a missile moving FTL, as soon as the drive field encounters the mass of the target it will overload the FTL drive, vaporizing the missile in the process. The drive field vanishes at the same and the "target" is pretty much unharmed; maybe a bit of structural distortion where the drive field came into contact with it.

For an FTL missile to work, it would have to drop out of FTL first and THEN attack the target, and since the target has 7.5 seconds to track the incoming missile, it will have plenty of time to aim its array of point-defense lasers at the predicted point of arrival. Hence, not very practical.



And I thought this thread was about asteroids and not fictional FTL drives? :p

IsaacKuo
2009-Dec-16, 01:48 AM
Zero. They are totally blind while using the FTL drive; they also can't be detected by any way other than picking up the gravity of the drive field itself. Furthermore, they can't change vector while the drive is active, as the gravitational shear would rip the ship apart. The only maneuver they can make at all would be to shut down the drive earlier than intended.
You don't specify exactly how easy or impossible it is to detect the starship. Since your patrol vessels are several AU from Earth, that implies that it's relatively easy to detect them.

As such, an FTL missile is practical. It just drops out of FTL once in a while to take a reading on where the target is and which direction it's moving in. This is actually pretty common in the animal world, where some predators are essentially blind while running.

Also, the drive field is not entirely stable. It requires energy to maintain, proportional to how much mass is inside it. If you add a whole lot of mass real quick--like, say, your FTL ship/missile runs into another ship or a large enough chunk of space debris or something--the drive will overload and burn itself out (see aforementioned "vigorous" failure). So if you try to hit a target with a missile moving FTL, as soon as the drive field encounters the mass of the target it will overload the FTL drive, vaporizing the missile in the process. The drive field vanishes at the same and the "target" is pretty much unharmed; maybe a bit of structural distortion where the drive field came into contact with it.
Where does the energy of the explosion go? Into magical ether or something?

It seems to me that you're introducing enough magic that you can decide whatever you want for everything else.

Anyway, since a missile can carry nothing but armament, it can outgun a general purpose warship whenever it gets within "engagement range". So the "boom" might actually be a salvo of those magical point defense lasers. The missile carries nothing but the drive system and laser weapons, while the target warship has to carry life support systems, supplies, fuel for long journeys, and so on. Even if the warship is so heavily armed that it's a roughly even match, that's okay. The missile has done its job if it gets destroyed in the process.

For an FTL missile to work, it would have to drop out of FTL first and THEN attack the target, and since the target has 7.5 seconds to track the incoming missile, it will have plenty of time to aim its array of point-defense lasers at the predicted point of arrival. Hence, not very practical.
It takes 7.5 seconds to drop out of FTL and destroy Earth, or land on Earth, or whatever...and you think a patrol ship twenty light minutes away is going to do something about that?

You really need to have your patrol ships detect and intercept the intruders further out for them to be able to do anything at all.

And I thought this thread was about asteroids and not fictional FTL drives? :p
Welcome to the world of FTL in scifi. The rule of thumb is simple. If your scifi universe has FTL drive systems, then the specific properties of the FTL drive systems utterly dominate.

Jim Starluck
2009-Dec-16, 02:58 AM
You don't specify exactly how easy or impossible it is to detect the starship. Since your patrol vessels are several AU from Earth, that implies that it's relatively easy to detect them.

Which is why they're hiding on asteroids in the first place.


Where does the energy of the explosion go? Into magical ether or something?

Into the missile, and once that's vaporized it radiates outward in every direction.

You'd think it would make the missile itself an effective warhead, but the missile's drive field will be large enough that when the leading edge of it hits the target ship, the missile itself will wind up a km or two away, so most of the energy of the explosion is wasted.


Anyway, since a missile can carry nothing but armament, it can outgun a general purpose warship whenever it gets within "engagement range". So the "boom" might actually be a salvo of those magical point defense lasers. The missile carries nothing but the drive system and laser weapons, while the target warship has to carry life support systems, supplies, fuel for long journeys, and so on. Even if the warship is so heavily armed that it's a roughly even match, that's okay. The missile has done its job if it gets destroyed in the process.

Remember what I said about warships being able to react quickly? The 7.5 seconds of warning is long enough that if they think they won't be able to win the fight (and they can get an estimate of the incoming object's mass from the strength of its drive field), they can fire up their own FTL drive and make a short hop away from the incoming ship/missile's point of emergence, and then engage at their discretion.

And considering how sophisticated you're making this missile, it's going to be a small starship in its own right.


It takes 7.5 seconds to drop out of FTL and destroy Earth, or land on Earth, or whatever...and you think a patrol ship twenty light minutes away is going to do something about that?

Neither of the alien civilzations in this scenario has anything even remotely near planet-busting firepower; their anti-ship missile warheads are roughly comparable to current-day ICBM warheads in yield.


Welcome to the world of FTL in scifi. The rule of thumb is simple. If your scifi universe has FTL drive systems, then the specific properties of the FTL drive systems utterly dominate.

Hence why I've been plotting out the specifics of this one for quite some time.

antoniseb
2009-Dec-16, 05:30 AM
Ummm, can you remind me what the OP was about?

Jim Starluck
2009-Dec-16, 05:39 AM
I did say just two posts ago that it was supposed to be about asteroids, but we've gotten quite a bit sidetracked, haven't we?

At any rate, the original question has been answered to my satisfaction. IsaacKuo, if you want to continue the discussion about FTL, let's do so via Private Message.

antoniseb
2009-Dec-16, 01:04 PM
... IsaacKuo, if you want to continue the discussion about FTL, let's do so via Private Message.

I'm not forcing the FTL discussion off the board, but OTB might be a better place for it.

Jim Starluck
2009-Dec-21, 07:40 AM
Thread's up (http://www.bautforum.com/off-topic-babbling/98433-fictional-ftl-drive.html#post1647300), if anyone's still interested.

neilzero
2009-Dec-21, 01:44 PM
Quote from original post. "How detailed an under standing do we have of their temperature and whatnot?" To me that means will liquid nitrogen boil on the surface just before sunrise on some, most, or nearly all main belt asteroids? I think I'm asking if some of them produce significant internal heat?
My guess is nearly all of them tumble or rotate with a period of 1 hour to 100 hours. I heard most about an 8 hour period, but I would think faster is typical for pea size and smaller asteroids. Some more whatnot would also be interesting, but with numbers instead of generalities. I suggested the boiling point of nitrogen in a vacuum, as I suspect the infrared temperature is quite different than other means of determining temperature. Neil

JohnD
2009-Dec-21, 01:54 PM
Jim,
Detection systems work on the principle, does something look different, from before, or different, from normal. I fear your stealth starship idea fails on the first. Boring a hole to hide in the asteroid will release a great deal of heat, whatever technology you use. So a large asteroid would suddenly flare with heat, in all directions. Bit like turning a lighthouse on.
Of course you could shunt the heat down a wormhole to another dimension, but god-like powers are rather boring.

And, anit-IR trechnology is already pretty good. See this IR pic of three models in normal clothing, and Anti-IR suit and a ghillie suit. http://www.army-technology.com/contractors/camouflage/intermat/intermat5.html Pretty good, eh? Several other examples on the same website

Ghillie suits have been around for yonks. They work in IR by scattering the radiation and distributing it over a larger area. Here's some German technology that looks pretty good too: http://www.youtube.com/watch?v=nx0ggSL8CkU&feature=PlayList&p=487FBE9C9D5442B3&index=1

So, if we can do that now, I'm sure your aliens can improve on the same principles.

John

IsaacKuo
2009-Dec-21, 03:03 PM
As I noted before, if they use solar power then the amount of heat generated remains the same. Also, it's not necessary to dig into the asteroid. Simply landing on the asteroid is good enough. A sheet painted to roughly match the characteristics of the surrounding rock can serve the same basic purpose as a ghillie suit.

neilzero
2009-Dec-21, 07:35 PM
Hi Isaac: Same long term average power level, perhaps, but in different frequency/wavelength bands. Also the rises and falls of luminosity will be dfferent (as the asteroid rotates) with PhotoVoltaic and/or heliostats covering/shading part of the surface. The dark side of the asteroid will sometimes have a hot spot = more near infrared at the drill site and spacecraft . For asteroids less than one kilometer, previous data is likely sparse, so these are safer hiding places. Neil