Planet cracking missiles

[pinecone]

Re: Planet cracking missiles

 

Short answer: read the link

http://www.projectrho.com/rocket/rocket3w.html#nostealth

 

 

An infrared source can be hidden with a heat sink, for about five minutes. Unless your heat sink is several miles in diameter.

 

Yes, an ion drive can be detected at a range of one astronomical unit, even if the drive is facing away from you. And this is only if the drive is throttled down to less than 1/1000 of a g of acceleration. If the acceleration is higher, the detection range grows.

 

The direction of the drive makes little difference. And even if it did, what use is it to only be able to accelerate directly at you? Unless you were trying to ram?

 

And the phrase "facing away from you" contains two assumptions:

[1] the ion drive owner knows where "you" are located

[2] "you" are the only observer in the solar system. If "you" deployed a few observational space probes around a few other planets, it will be impossible for the ion drive to face away from all of them.

 

And then there is the problem that an ion drive requires lots of electrical power to operate. Which requires a power plant of some kind, or a huge solar array. All of which will generate waste heat as it converts fuel or solar energy into electricity. Which will give away the ion drive's position.

 

You don't seem to understand that the background of space is at three degrees above absolute zero, so almost anything else stands out like a spotlight.

 

 

We are not worrying that asteroids are hard to see. We are worrying that nobody is willing to fund a constant sky watch to detect dangerous asteroids.

 

 

 

[1] How can the laser user be sure they know where all the observational space probes are?

[2] A laser used as a photon drive requires about THREE HUNDRED MEGAWATTS to produce one measly Newton of thrust.

 

The three engines on the Space Shuttle produce a combined 5.37 million Newtons of thrust.

 

To produce this much thrust with a laser would require 1.6 petawatts (1,611,000,000,000,000 watts).

 

Lasers are notoriously inefficient. Most have efficiencies of about 25%. Say we have a free-electron laser which has a theoretical maximum efficiency of 65%. This means that 35% of the input energy becomes waste heat.

 

This means that if the laser energy is 1.6 petawatts, the waste heat will be 860 terawatts. This means that the laser will be creating waste heat at a power level of 300 times the yearly energy consumption of the United States each second.

 

And you are somehow going to hide all this waste heat?

 

Again, read the link. Chances are, whatever you try to come up with has been tried already.

 

Of course if in your role as a Game Master, you invent an exciting campaign for your players that depends upon magically creating stealth in space, then you can ignore scientific accuracy in the name of pleasing your players.

 

Certainly some fuel for thought...but you seem to use assumptions that counter your claims. "If they know where you are? You claim nothing can hide in space!

 

And the laser counter feels false somehow...if I have a drive so effiecient that it emits photons as it's reaction mass, finding a way to make them partially or completely coherant does not seem so hard. (in compareson, anyway)

 

How effective Is heat detection? Has someone shown that it is mathmaticly impossable to conceal heat emissions? If so why hasn't someone obtained Billions from the defence department to spot stealth aircraft? In comparison to a total skyscan in space spotting a big thermal plume in space, a smaller thermal plume in the atmospher should be childs play.

 

Why should anyone pay millions to build a asteroid watch? It seems as though it is a trivial task, using off the shelf componites.

 

 

I guess I'm saying you make a claim "You cannot hide in space" ...so where is the proof?

 

Shooting holes in proposals does Not constitute proof. Who detcted a ion drive at 1 AU? What was the methodology?

 

I'm thinking that detecting something that you know where is ...is not real hard....so was it tracked independantly? (Hard to test...only one has ever flown as far as I know...)

As I said so far I have heard claims...where is proof available? What tests have been performed?

 

And as always what is the "dogma" level? People used to claim "No aircraft could fly, undetected by Radar" ...even though they sometimes did...and then Stealth came along...

[Kristopher]

Re: Planet cracking missiles

 

{shudder}

 

Ummmmmm, I have a suggestion. Wouldn't it be easier to just ignore the heat problems, pretend they don't exist?

 

Let me explain. As it turns out, your handwaving is more or less the same as a rather stubborn popular misconception that is the topic of many emails I get.

 

So if you take the easy route and ignore the heat problems, it's better for you, it's better for me, and it's better for any of your players that might decide to email me.

 

They wouldn't, because I wouldn't cite the Peltier-Seebek effect, exactly because, as your article points out, it does not convert heat into some other form of energy.

 

That's why I mentioned handwavium -- I wouldn't try to explain how it would work. If I had a way to convert heat to electricity directly, in violation of the 2nd law, I wouldn't be using it in a game, I'd be the richest man on earth.

[Nyrath]

Re: Planet cracking missiles

 

Certainly some fuel for thought...but you seem to use assumptions that counter your claims. "If they know where you are? You claim nothing can hide in space!

It doesn't matter if the ship trying to be stealthy knows where the you and the observation platforms are. For a small investment in observation platforms, there will be no safe place to aim your heat emissions.

 

 

And the laser counter feels false somehow...if I have a drive so effiecient that it emits photons as it's reaction mass' date=' finding a way to make them partially or completely coherant does not seem so hard. (in compareson, anyway)[/quote']

Ummmm, I think you are mistaking "coherence" with "efficiency". Have you had any course in physics?

 

Most laser generators produce beams that are pretty close to 100% coherent. This means the laser light is in lockstep.

 

But the generator efficiency is a measure of how much electricity input becomes laser energy output. The difference between the two becomes waste heat. Most laser generators have a theoretical maximum of around 25%, with the exception of the free electron laser at 65%. This is the maximum efficiency, in practice it will be lots worse.

 

 

How effective Is heat detection? Has someone shown that it is mathmaticly impossable to conceal heat emissions? If so why hasn't someone obtained Billions from the defence department to spot stealth aircraft?

I keep telling you: read the link. All of this is covered there. You are not raising anything new.

 

[a] How effective is heat detection? Has someone shown that it is mathmaticly impossable to conceal heat emissions?

A full spherical sky search is 41,000 square degrees. A wide angle lens will cover about 100 square degrees (a typical SLR personal camera is about 1 square degree); you'll want overlap, so call it 480 exposures for a full sky search, with each exposure taking about 350 megapixels.

 

Estimated exposure time is about 30 seconds per 100 square degrees of sky looking for a magnitude 12 object (which is roughly what the drive I spec'd out earlier would be). So, 480 / 2 is 240 minutes, or about 4 HOURS for a complete sky survey. This will require signal processing of about 150 gigapizels per two hours, and take a terabyte of storage per sweep.

 

That sounds like a lot, but...

 

Assuming 1280x1024 resolution, playing an MMO at 60 frames per second...78,643,200 = 78 megapixels per second. Multiply by 14400 seconds for 4 hours, and you're in the realm of 1 terapixel per sky sweep Now, digital image comparison is in some ways harder, some ways easier than a 3-D gaming environment. We'll say it's about 8x as difficult - that means playing World of Warcraft on a gaming system for four hours is about comparable to 75 gigapixels of full sky search. So not quite current hardware, but probably a computer generation (2 years) away. Making it radiation hardened to work in space, and built to government procurement specs, maybe 8-10 years away.

 

I can buy terabyte hard drive arrays now.

 

I can reduce scan time by adding more sensors, but my choke point becomes data processing. On the other hand, it's not unreasonable to assume that the data processing equipment will get significantly better at about the same rate that gaming PCs get significantly better.

 

Now, this system has limits - it'll have trouble picking up a target within about 2 degrees of the sun without an occlusion filter, and even with one, it'll take extra time for those exposures.

 

It won't positively identify a target - it'll just give brightness and temperature and the fact that it's something radiating like a star that moves relative to the background.

 

On the other hand, at the thrusts given above, it'll take somewhere around 2 days of thrust to generate the delta v to move from Earth to Mars, and the ship will be in transit for about 1-4 months depending on planetary positions.

 

If so why hasn't someone obtained Billions from the defence department to spot stealth aircraft?

 

Stealth aircraft fly in the air. That's why they are called aircraft. Air is found on Earth. Earth has something called the "horizon", which severely limits the range at which an aircraft can be spotted. The Earth's air is also quite hot compared to the space environment. The waste heat from a stealth aircraft is not as obvious since it is relatively much more close to the ambient temperature. The air is also a good heat sink, quickly erasing the thermal plume. Even so, a stealth aircraft can be spotted by thermal imaging, only you have to be quite close.

 

Spacecraft fly in space, That's why they are called spacecraft. Space is found in space. Space does not have any horizon, you can see out to the distant galaxies, so there is no range limit. Space is incredibly cold (three degrees Kelvin), so the waste heat from a trying-to-be-stealthy spacecraft stands out like it was lit up with powerful spotlights. Space also does not do much to erase thermal plumes. As mentioned before, you can see the thermal plume from the Space Shuttle main engines as far out as Pluto, or more or less the radius of the entire solar system.

 

 

 

 

Why should anyone pay millions to build a asteroid watch? It seems as though it is a trivial task' date=' using off the shelf componites.[/quote']

Ask NASA.

 

from http://usgovinfo.about.com/library/weekly/aa072702a.htm

What is the Government Doing About This?

In 1993 and again in 1998, Congressional hearings were held to study the impact hazard. As a result, both NASA and the Air Force are now supporting programs to discover Earth-threatening objects. Congress currently budgets only about $3 million per year for programs like the Near Earth Object (NEO) project. While other governments have expressed concern about the impact hazard, none have yet funded any extensive surveys or related defense research.

 

 

 

I guess I'm saying you make a claim "You cannot hide in space" ...so where is the proof?

 

Shooting holes in proposals does Not constitute proof. Who detcted a ion drive at 1 AU? What was the methodology?

 

I'm thinking that detecting something that you know where is ...is not real hard....so was it tracked independantly? (Hard to test...only one has ever flown as far as I know...)

As I said so far I have heard claims...where is proof available? What tests have been performed?

Go ask an astronomer. These figures are assuming total sky scans with off the shelf technology. You don't think I made up these figures, do you? I obtained them from real experts, not me.

 

And as always what is the "dogma" level? People used to claim "No aircraft could fly' date=' undetected by Radar" ...even though they sometimes did...and then Stealth came along...[/quote']

Do you have a quote for that? I never read anybody who claimed that? If I did know any better, it sounds like you are using the tired old "they said they couldn't break the sound barrier" argument.

 

 

90% of the email I get about my atomic rocket website is on only three topic: I don't want to admit there is no stealth in space, I don't want to admit that faster-than-light travel is impossible, and I don't want to admit that space fighters make no sense scientifically, economically, or militarily. You apparently fall into the first category.

 

But don't take my word for it. Go to the experts yourself and ask them, they can be found here:

http://games.groups.yahoo.com/group/sfconsim-l/

[SSgt Baloo]

Re: Planet cracking missiles

 

I don't think undetectable means what you think it means. At the present level of technology, anything not in Earth orbit has an exceedingly good chance of remaining undetected. Space is big and unless you're looking in the right direction you won't see a thing.

[Nyrath]

Re: Planet cracking missiles

 

I don't think undetectable means what you think it means. At the present level of technology' date=' anything not in Earth orbit has an exceedingly good chance of remaining undetected. Space is big and unless you're looking in the right direction you won't see a thing.[/quote']

 

I repeat:

 

A full spherical sky search is 41,000 square degrees. A wide angle lens will cover about 100 square degrees (a typical SLR personal camera is about 1 square degree); you'll want overlap, so call it 480 exposures for a full sky search, with each exposure taking about 350 megapixels.

 

Estimated exposure time is about 30 seconds per 100 square degrees of sky looking for a magnitude 12 object (which is roughly what the drive I spec'd out earlier would be). So, 480 / 2 is 240 minutes, or about 4 HOURS for a complete sky survey. This will require signal processing of about 150 gigapizels per two hours, and take a terabyte of storage per sweep.

 

That sounds like a lot, but...

 

Assuming 1280x1024 resolution, playing an MMO at 60 frames per second...78,643,200 = 78 megapixels per second. Multiply by 14400 seconds for 4 hours, and you're in the realm of 1 terapixel per sky sweep Now, digital image comparison is in some ways harder, some ways easier than a 3-D gaming environment. We'll say it's about 8x as difficult - that means playing World of Warcraft on a gaming system for four hours is about comparable to 75 gigapixels of full sky search. So not quite current hardware, but probably a computer generation (2 years) away. Making it radiation hardened to work in space, and built to government procurement specs, maybe 8-10 years away.

 

I can buy terabyte hard drive arrays now.

 

I can reduce scan time by adding more sensors, but my choke point becomes data processing. On the other hand, it's not unreasonable to assume that the data processing equipment will get significantly better at about the same rate that gaming PCs get significantly better.

 

Now, this system has limits - it'll have trouble picking up a target within about 2 degrees of the sun without an occlusion filter, and even with one, it'll take extra time for those exposures.

 

It won't positively identify a target - it'll just give brightness and temperature and the fact that it's something radiating like a star that moves relative to the background.

 

On the other hand, at the thrusts given above, it'll take somewhere around 2 days of thrust to generate the delta v to move from Earth to Mars, and the ship will be in transit for about 1-4 months depending on planetary positions.

 

 

The space background in the infrared wavelengths is near pitch black at a black-body temperature of three degrees Kelvin. A manned spacecraft with all engines and power plants turned off and with the habitat module set to the freezing point of water in a desperate attempt to hide is still going to be radiating at 273 degrees Kelvin, and will show up like a beacon. An unmanned drone will be cooler, but still warmer than space.

 

And if the drone or spacecraft actually tries to move, thus using some sort of propulsion system, well they might as well shoot off signal flares and set up ten foot neon signs saying "WE ARE HERE!!!"

[SSgt Baloo]

Re: Planet cracking missiles

 

I repeat:

 

A full spherical sky search is 41,000 square degrees. A wide angle lens will cover about 100 square degrees (a typical SLR personal camera is about 1 square degree); you'll want overlap, so call it 480 exposures for a full sky search, with each exposure taking about 350 megapixels.

 

Estimated exposure time is about 30 seconds per 100 square degrees of sky looking for a magnitude 12 object (which is roughly what the drive I spec'd out earlier would be). So, 480 / 2 is 240 minutes, or about 4 HOURS for a complete sky survey. This will require signal processing of about 150 gigapizels per two hours, and take a terabyte of storage per sweep.

 

That sounds like a lot, but...

 

Assuming 1280x1024 resolution, playing an MMO at 60 frames per second...78,643,200 = 78 megapixels per second. Multiply by 14400 seconds for 4 hours, and you're in the realm of 1 terapixel per sky sweep Now, digital image comparison is in some ways harder, some ways easier than a 3-D gaming environment. We'll say it's about 8x as difficult - that means playing World of Warcraft on a gaming system for four hours is about comparable to 75 gigapixels of full sky search. So not quite current hardware, but probably a computer generation (2 years) away. Making it radiation hardened to work in space, and built to government procurement specs, maybe 8-10 years away.

 

I can buy terabyte hard drive arrays now.

 

I can reduce scan time by adding more sensors, but my choke point becomes data processing. On the other hand, it's not unreasonable to assume that the data processing equipment will get significantly better at about the same rate that gaming PCs get significantly better.

 

Now, this system has limits - it'll have trouble picking up a target within about 2 degrees of the sun without an occlusion filter, and even with one, it'll take extra time for those exposures.

 

It won't positively identify a target - it'll just give brightness and temperature and the fact that it's something radiating like a star that moves relative to the background.

 

On the other hand, at the thrusts given above, it'll take somewhere around 2 days of thrust to generate the delta v to move from Earth to Mars, and the ship will be in transit for about 1-4 months depending on planetary positions.

 

 

The space background in the infrared wavelengths is near pitch black at a black-body temperature of three degrees Kelvin. A manned spacecraft with all engines and power plants turned off and with the habitat module set to the freezing point of water in a desperate attempt to hide is still going to be radiating at 273 degrees Kelvin, and will show up like a beacon. An unmanned drone will be cooler, but still warmer than space.

 

And if the drone or spacecraft actually tries to move, thus using some sort of propulsion system, well they might as well shoot off signal flares and set up ten foot neon signs saying "WE ARE HERE!!!"

 

I'm not saying it's impossible, but does anybody have plans to set up a detection system like that anytime soon?

[Captain Obvious]

Re: Planet cracking missiles

 

I'm not saying it's impossible' date=' but does anybody have plans to set up a detection system like that anytime soon?[/quote']

 

Probably not soon, but when attempts to build a stealthy spacecraft become likely, it will probably be a high priority for someone.

[Nyrath]

Re: Planet cracking missiles

 

I'm not saying it's impossible' date=' but does anybody have plans to set up a detection system like that anytime soon?[/quote']

No. Seeing that is is all NASA can do to get funding for a detection system for rogue asteroids that could wipe out our civilization, there is no funding for a detection system for an alien invasion fleet.

 

However, in a universe where hostile armed spacecraft were common, such a detection system would also be common.

[Guest steamteck]

Re: Planet cracking missiles

 

Ok, Got it no stealth in space but I have two things I wonder about for my own campaign.

How far can radiated heat be detected and how fast does said heat travel.? That is how old is your observational data?

[L. Marcus]

Re: Planet cracking missiles

 

Just take the example above -- the heat is, obviously, EM radiation so it travels at the speed of light. It takes light something like 5+ hours to reach Pluto from the Sun.

[Cancer]

Re: Planet cracking missiles

 

Two separated observing stations separated by an AU or so ... this would be, for example, at the L4/L5 points of the Earth-Sun system, or one each in orbit around Earth and Mars ... would be adequate for locating something in 3 dimensions. This has actually been done for locating an X-ray source unambiguously in the sky, although serendipitously. The time lag between the stations nails down the spatial ambiguity, and for anything inside the solar system, assuming any kind of angular resolution, you'll be able to pin down the distance as well as direction by parallax.

 

Rapid-response all-sky observing networks are in place now, but not in the waveband or sensitivity required for this application. There hasn't been need for them. Most astronomical objects don't appear and disappear in a minute or less, so a more leisurely approach to looking for them is adequate.

[Nyrath]

Re: Planet cracking missiles

 

How far can radiated heat be detected

 

Of course this depends upon how hot the object is.

 

I'll give you some examples then give you the dull boring equations.

 

If you have a spacecraft the size of a Russian Oscar-II submarine (about 154 meters long) that is keeping a frigid interior temperature of 273 Kelvin (32 Fahrenheit, where water freezes into ice) in a desperate attempt to be stealthy, with all the engines and power plants turned off, and you are using current day off-the-shelf infrared detection technology, the maximum distance the spacecraft can be detected is about 38,800,000 kilometers.

 

This is about one hundred times the distance between the Earth and the Moon, or about 129 light-seconds.

 

If the spacecraft raised the thermostat to room temperature, it could be seen at a range of about 43,800,000 kilometers.

 

Now, if the spacecraft turns on its rocket engine, you can see it from several solar system away. We will show some examples of two spacecraft. One is the same mass as an Oscar submarine (13,900 metric tons), the other is only 1000 metric tons. We will use a chemical rocket, an ion drive, a VASIMR plasma drive, and a Hydrogen-Boron Fusion drive. We will use accelerations of 1 gee, one tenth gee, and one one-hundredth gee.

 

We will show the maximum range the the ship can be detected by current off-the-shelf IR detectors, in kilometers, light-seconds, and astronomical units (the distance between the Earth and the Sun). The solar system is about 80 AU in diameter.

Detection range goes down as the ship mass, specific impulse and thrust go down.

 

Chemical 13.9 kton 1.00 gee = 3,500,000,000km/12,000ls/24au

Chemical 13.9 kton 0.10 gee = 1,100,000,000km/3800ls/7.5au

Chemical 13.9 kton 0.01 gee = 360,000,000km/1200ls/2.4au

 

Chemical 1 kton 1.00 gee = 960,000,000km/3200ls/6.4au

Chemical 1 kton 0.10 gee = 300,000,000km/1000ls/2.0au

Chemical 1 kton 0.01 gee = 95,000,000km/320ls/0.6au

 

Ion 13.9 kton 1.00 gee = 76,000,000,000km/260,000ls/515au

Ion 13.9 kton 0.10 gee = 24,000,000,000km/81,000ls/163au

Ion 13.9 kton 0.01 gee = 7,700,000,000km/26,000ls/51.4au

 

Ion 1 kton 1.00 gee = 21,000,000,000km/69,000ls/138au

Ion 1 kton 0.10 gee = 6,500,000,000km/22,000ls/43.6au

Ion 1 kton 0.01 gee = 2,100,000,000km/6900ls/13.8au

 

VASIMR 13.9 kton 1.00 gee = 76,000,000,000km/250,000ls/509au

VASIMR 13.9 kton 0.10 gee = 24,000,000,000km/80,000ls/161au

VASIMR 13.9 kton 0.01 gee = 7,600,000,000km/25,000ls/50.9au

 

VASIMR 1 kton 1.00 gee = 20,000,000,000km/68,000ls/137au

VASIMR 1 kton 0.10 gee = 6,500,000,000km/22,000ls/43.2au

VASIMR 1 kton 0.01 gee = 2,000,000,000km/6800ls/13.7au

 

H-B Fusion 13.9 kton 1.00 gee = 170,000,000,000km/550,000ls/1100au

H-B Fusion 13.9 kton 0.10 gee = 53,000,000,000km/170,000ls/352au

H-B Fusion 13.9 kton 0.01 gee = 17,000,000,000km/56,000ls/110au

 

H-B Fusion 1 kton 1.00 gee = 45,000,000,000km/150,000ls/298au

H-B Fusion 1 kton 0.10 gee = 14,000,000,000km/47,000ls/94.3au

H-B Fusion 1 kton 0.01 gee = 4,500,000,000km/15,000ls/19.8au

 

The dull equations

 

Ship with engines and power plant off

Rd = 13.4 * sqrt(A) * T^2

where:

Rd = detection range (km)

A = spacecraft projected area (square meters )

T = surface temperature (Kelvin, room temperature is about 285-290 K)

x^2 = square of x

 

If the ship is a convex shape, its projected area will be roughly one quarter of its surface area.

 

Ship with engines running

Rd = ( 1,780,0000 * sqrt( Ms*As*Isp*(1-Nd) ) ) * (sqrt(0.04 * π))

where:

Rd = maximum detection range (kilometers)

Ms = bogey spacecraft mass (metric tons)

As = bogey spacecraft acceleration (G)

Isp = bogey drive specific impulse (seconds) Chemical = 458, Ion = 21,400, VASIMR = 30,000, H-B Fusion = 100,000, other

Nd = bogey drive efficiency (0.0 to 1.0) Chemical = 0.98, Ion = 0.5, VASIMR = 0.65, H-B Fusion = 0.5

π = Pi = 3.141593...

sqrt(x) = square root of x

 

and how fast does said heat travel.? That is how old is your observational data?

Infrared radiation travels at the speed of light. Divide distance in kilometers by 299792.458 to get how many seconds it takes the IR to travel the distance. Or use the figure for "light-seconds".

 

Divide time in seconds by 3600 for hours, 86400 for days, 2592000 for (30 day) months, or 31536000 for years

[Guest steamteck]

Re: Planet cracking missiles

 

Thanks. Co,plete brain glitch on IR's speed there. I knew that but didn't process. Your examples pretty much give me ehat I need for my game. Thanks again.

[Nyrath]

Re: Planet cracking missiles

 

Your examples pretty much give me ehat I need for my game. Thanks again.

Glad to help

[pinecone]

Re: Planet cracking missiles

 

Short answer: read the link

http://www.projectrho.com/rocket/rocket3w.html#nostealth

 

 

An infrared source can be hidden with a heat sink, for about five minutes. Unless your heat sink is several miles in diameter.

 

Yes, an ion drive can be detected at a range of one astronomical unit, even if the drive is facing away from you. And this is only if the drive is throttled down to less than 1/1000 of a g of acceleration. If the acceleration is higher, the detection range grows.

 

The direction of the drive makes little difference. And even if it did, what use is it to only be able to accelerate directly at you? Unless you were trying to ram?

 

And the phrase "facing away from you" contains two assumptions:

[1] the ion drive owner knows where "you" are located

[2] "you" are the only observer in the solar system. If "you" deployed a few observational space probes around a few other planets, it will be impossible for the ion drive to face away from all of them.

 

And then there is the problem that an ion drive requires lots of electrical power to operate. Which requires a power plant of some kind, or a huge solar array. All of which will generate waste heat as it converts fuel or solar energy into electricity. Which will give away the ion drive's position.

 

You don't seem to understand that the background of space is at three degrees above absolute zero, so almost anything else stands out like a spotlight.

 

 

We are not worrying that asteroids are hard to see. We are worrying that nobody is willing to fund a constant sky watch to detect dangerous asteroids.

 

 

 

[1] How can the laser user be sure they know where all the observational space probes are?

[2] A laser used as a photon drive requires about THREE HUNDRED MEGAWATTS to produce one measly Newton of thrust.

 

The three engines on the Space Shuttle produce a combined 5.37 million Newtons of thrust.

 

To produce this much thrust with a laser would require 1.6 petawatts (1,611,000,000,000,000 watts).

 

Lasers are notoriously inefficient. Most have efficiencies of about 25%. Say we have a free-electron laser which has a theoretical maximum efficiency of 65%. This means that 35% of the input energy becomes waste heat.

 

This means that if the laser energy is 1.6 petawatts, the waste heat will be 860 terawatts. This means that the laser will be creating waste heat at a power level of 300 times the yearly energy consumption of the United States each second.

 

And you are somehow going to hide all this waste heat?

 

Again, read the link. Chances are, whatever you try to come up with has been tried already.

 

Of course if in your role as a Game Master, you invent an exciting campaign for your players that depends upon magically creating stealth in space, then you can ignore scientific accuracy in the name of pleasing your players.

 

Well...I'l repeat myself, then drop it...I'm not interested in putting up ideas so they can be shot down. I'm trying to understand the basis for the claims.

 

Yes I do know that air is differant than space...but I also know that principles of physics aplly everywhere the same (as far as we know) So I wish to aply the claims to my own knowlage.

 

If the best you can do is suggest that I am too ignorant to understand that I should blindly accept your claims...well so be it.

 

I did not read the whole site because all I saw was claims, and a little math in the form of several terms that do not show how they were determined...leaving the result of little seeming proof. I remember a simular one from old sci-fi readings that "proved" that billions (or dozens...or none at all) of alien civs were out there.....it all depends on what value you assign to the variables. Leaving the equation a fancy way to convince people of a claim.

 

Best of luck to you.

[Nyrath]

Re: Planet cracking missiles

 

If the best you can do is suggest that I am too ignorant to understand that I should blindly accept your claims...well so be it.

Look, don't take my word for it. Go find a physics professor or somebody who can give you the proof you want and ask them.

 

You can find some experts to ask your questions of at the usenet newsgroup rec.arts.sf.science

http://groups.google.com/group/rec.arts.sf.science/topics?hl=en

or in the Yahoo group SFConSim-l

http://games.groups.yahoo.com/group/sfconsim-l/

 

I did not say you were ignorant, I was asking if you had taken any course in physics.

[L. Marcus]

Re: Planet cracking missiles

 

Well...I'l repeat myself, then drop it...I'm not interested in putting up ideas so they can be shot down. I'm trying to understand the basis for the claims.

 

Yes I do know that air is differant than space...but I also know that principles of physics aplly everywhere the same (as far as we know) So I wish to aply the claims to my own knowlage.

 

If the best you can do is suggest that I am too ignorant to understand that I should blindly accept your claims...well so be it.

 

I did not read the whole site because all I saw was claims, and a little math in the form of several terms that do not show how they were determined...leaving the result of little seeming proof. I remember a simular one from old sci-fi readings that "proved" that billions (or dozens...or none at all) of alien civs were out there.....it all depends on what value you assign to the variables. Leaving the equation a fancy way to convince people of a claim.

 

Best of luck to you.

. . . I must say, if you are in doubt, do the physics yourself. Or go the same experts Nyrath did.

[SSgt Baloo]

Re: Planet cracking missiles

 

Of course, considering the forum we're in, the science might be a bit more rubbery in the campaign where such is going on than in our own. In a hard science campaign, I suspect someone wishing to remain undetected by such an early warning system would have to hack the system that does the detection and make an exception for their own particular "signature".

 

"What the... what just happened?

 

"Kelso Station just evaporated!"

 

"I don't understand!?! The detection grid didn't give a peep!"

 

"Run diagnostics! We've been hacked!

[Cancer]

Re: Planet cracking missiles

 

You can estimate the infrared fluxes by yourself, though it gets tedious to convince yourself that you're doing it right. Here's a sloppy way to go about it.

 

For any kind of non-photon rocket, to figure out the amount of IR radiation generated, you need the temperature profile of the exhaust (that is, the temperature of the exhaust as a function of where you are in the rocket output) and the shape and size of the exhaust plume. I don't have an immediate suggestion for where to get such information, unfortunately.

 

Figure out how many square meters of exhaust plume are at what temperature, and what your view of those is. Any part of the plume that is blocked by the spacecraft you won't see, but in general the plume will be MUCH larger than the ship and all you'll have blocked is the very hottest core.

 

Pick the waveband your prospective lookout will be using. My suggestion is to pick three sample wavelengths, 1 micron, 10 microns, and 100 microns.

 

For each square meter of the plume, use Planck's Law and compute the total infrared emitted at each wavelength. Black-body radiation is isotropic (it goes equally in all directions). Add up all the square meters worth. You'll get a total power emitted per unit frequency (or wavelength) by the plume.

 

Next, assume that gets radiated isotropically -- spherical symmetry. Pick a number for how far away the rocket is ... say, 10 AU. Compute the area of the sphere of that size. Divide the total pwoer radiated by that area. You'll get a flux (power per unit area per unit wavelength or frequency).

 

You can compare that flux at each wavelength to the flux of a standard. Annoyingly, that turns out to be hard, because the absolute flux calibration in the far IR is arcane. (It's easy to compare your IR flux to that of Vega at 1 micron ... that calibration has long been done ... but at longer wavelengths than that, where you really expect the rocket to show up, it's much harder.)

[L. Marcus]

Re: Planet cracking missiles

 

. . . Anyhoo, regarding tracking asteroids -- here's an interesting tidbit from New Scientist: Space rock collides with Earth right on time.

[Nyrath]

Re: Planet cracking missiles

 

Yes, I wish they would go into some detail about how far the asteroid was from Earth when it was spotted.

[Cancer]

Re: Planet cracking missiles

 

Trying to track that down now. According to the Mnor Planet Center page, it was discovered at Mt. Lemmon on UT date Oct 6.28, and hit the atmosphere on UT date Oct 7.115. Haven't found the data from the observation set yet.

 

EDIT: the text of IAU Circular 8990, with a set of images spliced into a movie, is here; the main page is in Russian but the IAUC quotation is left in English. The circular doesn't mention the apparent magnitude, so I'm going to keep digging.

 

EDIT 2: I'll need to crunch numbers more carefully when I have more time, but I think it was roughly apparent magnitude 17 when discovered. The IAUC says Delta = 0.0033 AU at discovery, about 1.27 times the Earth-Moon distance.

 

EDIT 3: another pseudo-video towards the bottom of the page. You can see the streaks. The frames are taken in different colors, so the brightnesses of things aren't matched in the different frames.

[L. Marcus]

Re: Planet cracking missiles

 

. . . UT date? Is that anything like stardate?

[Cancer]

Re: Planet cracking missiles

 

It just specifies the time in fractional days (rather than hours-minutes-seconds) in Universal Time.