Post by Machina Haruspex on Dec 17, 2007 17:07:51 GMT -5
Active sensor emitters can be the target of EMP or other beam weapons; it is much more difficult to locate and destroy a widely spread cloud of passive sensors. In a civilised system, the chances are you won't be all that far away from enemy sensors; anything that has even the slightest interest in defence and the resources of a solar system will have the outer system seeded with millions (or billions or trillions) of passive sensor platforms which are very cheap, very stealthy and very good at spotting a ship that is radiating at all in any frequency.
Functional Characteristics:
* � Resolution
* � Sensitivity
* � Wavelength
Optical Telescopes Aperture Diameter /m Volume /m3
0.25 1.8
0.50 14
1.00 110
1.50 380
2.00 900
2.50 1800
The resolution of a sensor is given by �xr = R �s / ds where
* � R=Range
* � �s=Sensor wavelength
* � ds=Effective aperture
Passive sensor clouds for use in defended systems effectively rule out the use of active detection systems by exploring or hostile spacecraft. A spacecraft's passive sensor array often consists of a set of Telescopes or focal field arrays operating in the infrared to visible range.
A global set of low-resolution, low-sensitivity scopes is used to track all possible targets (typically such an array can detect the waste heat of a fusion reactor several AUs distant). Target tracking and identification is carried out by a smaller number of larger telescopes (usually in the 50cm size range, but as large as 2m for major vessels; even larger for habitat cylinders).
An OASIS (Optical Aperture Synthesis Imaging System) arrangement may be the range at which detailed target identification and imaging may be carried out. Vibrations caused by operating drive systems limits the use of OASIS to ships that are not accelerating. Spacecraft may deploy passive sensor clouds but they are liable to be detected by accidental radiation from their data communications or any attitude adjustments they might make.
On warships, there is a second type of important sensor: the X-ray Telescope. Operating fusion drives discharge plasma at a temperature of around a hundred million kelvin. The initial cooling of this drive plume is by x-ray emission, and x-rays are also emitted from the fusing regions.
A pulsed or continuous fusion drive produces terawatts of power, and an amat or GUT-drive can produce several orders of magnitude more, much of which ends up as x-rays, or extreme ultraviolet. As well as detecting the high-temperature drive plume, x-ray calorimetry can give information on the drive geometry and reaction conditions.
Such data can help to identify the class of ship (or design of drive). The cylindrical mirrors used on x-ray telescopes are of much poorer quality than the mirrors used in near-optical telescopes, so the x-ray detectors are of only limited use for attaining firing solutions.
Neutrino Detectors
Can detect emissions from fusion, Amat, GUT and most kinds of reactionless drive, but are usually massive structures, often hidden in asteroids or planets. Small shipborne versions are generally of poor resolution and may be confused by decoy neutrino emitter, as at the battle of Pehhpepep.
Forward mass detectors
Are so called because they were developed by information age guru Dr. Robert Forward, not because they can't look backwards. These detectors are capable of detecting and determining the mass of objects remotely, and are particularly useful for detecting neutronium or certain kinds of reactionless drive craft.
Superconducting Quantum Interference Devices
(Squids) can detect many kinds of magnetic and gravitic anomalies, and are particularly useful for planetary scanning. Hostile spacecraft may hide in planetary atmospheres, oceans, ring systems and even inside the photospheres of suns; mass detection and squid technology can often find them.
Gravitational Wave detectors
Are sensors capable of detecting many kinds of acceleration at long distances, and can detect the peculiar signature of most reactionless drives, although a finely tuned Bias drive craft may escape detection.
Biosensors and Chemosensors
Can be deployed throughout a system, to detect biological and nanotech activity, which may otherwise go undetected; these small weapons are often deployed against sensor arrays, causing systemic breakdown as a preliminary to attack.
Passive sensors can track targets at a much greater range than the range at which identification becomes possible. The plume from a fusion rocket is so clearly visible that warships spend most of the time on unpowered orbits, or accelerating using a secondary drive at much lower power, or accelerating in short bursts. The fusion/Amat/GUT drive is only used when stealth has ceased to be a significant factor (i.e. when actively engaging enemy vessels).
To make detection more difficult attacking craft can cover their hulls in active stealth materials; all warships will have some sort of mimetic / chameleon hull, but simple black coating is all that is needed, at that distance (the ship being so far away and tiny) they are not likely to occlude any stars in the defender's visual field. Assuming of course that the enemy aren't using passive sensors to look for the thermal signature of your ship, in which case a black coating will make it stand out because it will make it radiate more.
Ships by their very nature are hard to keep cool, their reactors need to have a high output and so will output a lot of heat which you have to radiate or the ship will suffer problems (ranging from systems over heating to the ship actually melting) very quickly, and even with the reactor and all other heat sources shut down you still have the problem of cooling your ship down to the temperature of the cosmic microwave background radiation (CMBR), because even even if your opponents tech is only equivalent to information age tech they will be able to spot even very tiny temperature variations.
Advanced energy management can allow waste heat to be radiated as a single beam away from the defending positions, in interstellar space the beam will not be obvious, but in the dust cloud of a solar system it might be more obvious.
Functional Characteristics:
* � Resolution
* � Sensitivity
* � Wavelength
Optical Telescopes Aperture Diameter /m Volume /m3
0.25 1.8
0.50 14
1.00 110
1.50 380
2.00 900
2.50 1800
The resolution of a sensor is given by �xr = R �s / ds where
* � R=Range
* � �s=Sensor wavelength
* � ds=Effective aperture
Passive sensor clouds for use in defended systems effectively rule out the use of active detection systems by exploring or hostile spacecraft. A spacecraft's passive sensor array often consists of a set of Telescopes or focal field arrays operating in the infrared to visible range.
A global set of low-resolution, low-sensitivity scopes is used to track all possible targets (typically such an array can detect the waste heat of a fusion reactor several AUs distant). Target tracking and identification is carried out by a smaller number of larger telescopes (usually in the 50cm size range, but as large as 2m for major vessels; even larger for habitat cylinders).
An OASIS (Optical Aperture Synthesis Imaging System) arrangement may be the range at which detailed target identification and imaging may be carried out. Vibrations caused by operating drive systems limits the use of OASIS to ships that are not accelerating. Spacecraft may deploy passive sensor clouds but they are liable to be detected by accidental radiation from their data communications or any attitude adjustments they might make.
On warships, there is a second type of important sensor: the X-ray Telescope. Operating fusion drives discharge plasma at a temperature of around a hundred million kelvin. The initial cooling of this drive plume is by x-ray emission, and x-rays are also emitted from the fusing regions.
A pulsed or continuous fusion drive produces terawatts of power, and an amat or GUT-drive can produce several orders of magnitude more, much of which ends up as x-rays, or extreme ultraviolet. As well as detecting the high-temperature drive plume, x-ray calorimetry can give information on the drive geometry and reaction conditions.
Such data can help to identify the class of ship (or design of drive). The cylindrical mirrors used on x-ray telescopes are of much poorer quality than the mirrors used in near-optical telescopes, so the x-ray detectors are of only limited use for attaining firing solutions.
Neutrino Detectors
Can detect emissions from fusion, Amat, GUT and most kinds of reactionless drive, but are usually massive structures, often hidden in asteroids or planets. Small shipborne versions are generally of poor resolution and may be confused by decoy neutrino emitter, as at the battle of Pehhpepep.
Forward mass detectors
Are so called because they were developed by information age guru Dr. Robert Forward, not because they can't look backwards. These detectors are capable of detecting and determining the mass of objects remotely, and are particularly useful for detecting neutronium or certain kinds of reactionless drive craft.
Superconducting Quantum Interference Devices
(Squids) can detect many kinds of magnetic and gravitic anomalies, and are particularly useful for planetary scanning. Hostile spacecraft may hide in planetary atmospheres, oceans, ring systems and even inside the photospheres of suns; mass detection and squid technology can often find them.
Gravitational Wave detectors
Are sensors capable of detecting many kinds of acceleration at long distances, and can detect the peculiar signature of most reactionless drives, although a finely tuned Bias drive craft may escape detection.
Biosensors and Chemosensors
Can be deployed throughout a system, to detect biological and nanotech activity, which may otherwise go undetected; these small weapons are often deployed against sensor arrays, causing systemic breakdown as a preliminary to attack.
Passive sensors can track targets at a much greater range than the range at which identification becomes possible. The plume from a fusion rocket is so clearly visible that warships spend most of the time on unpowered orbits, or accelerating using a secondary drive at much lower power, or accelerating in short bursts. The fusion/Amat/GUT drive is only used when stealth has ceased to be a significant factor (i.e. when actively engaging enemy vessels).
To make detection more difficult attacking craft can cover their hulls in active stealth materials; all warships will have some sort of mimetic / chameleon hull, but simple black coating is all that is needed, at that distance (the ship being so far away and tiny) they are not likely to occlude any stars in the defender's visual field. Assuming of course that the enemy aren't using passive sensors to look for the thermal signature of your ship, in which case a black coating will make it stand out because it will make it radiate more.
Ships by their very nature are hard to keep cool, their reactors need to have a high output and so will output a lot of heat which you have to radiate or the ship will suffer problems (ranging from systems over heating to the ship actually melting) very quickly, and even with the reactor and all other heat sources shut down you still have the problem of cooling your ship down to the temperature of the cosmic microwave background radiation (CMBR), because even even if your opponents tech is only equivalent to information age tech they will be able to spot even very tiny temperature variations.
Advanced energy management can allow waste heat to be radiated as a single beam away from the defending positions, in interstellar space the beam will not be obvious, but in the dust cloud of a solar system it might be more obvious.