Assuming something like MT's thrusters are the maneuver drives in CT, would there be a contrail or some other signature audio/visual effects of a ship entering a planetry atomsphere? Something one could bring attention to and say with authority, "A star ship has just landed on this world."
Contrail, Yes or No
- Thread starter JAFARR
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http://www.amsmeteors.org/
At minimum you have the movement of a large object at high speeds through the upper atmosphere. You probably wouldn't end up with "a star ship", but you might end up with "a large object coming from space" - which could be debris, a meteorite or a star ship. All of which are worth observing.
Icosahedron
SOC-14 1K
No, NIMTU. With gravitic thrusters, there is no need to enter the atmosphere at high speed. If you have sufficient stealth/ECM to defeat ground-based sensors, you can come and go secretly.
How else do 'they' carry out abductions?
How else do 'they' carry out abductions?
far-trader
SOC-14 10K
Under cover of darkness in rural areas of course. And 'they' still get seen all the time. I mean come on, if they really wanted to be all secret and stealth, THEY GOTTA TURN OFF ALL THOSE LIGHTS ON THEIR FLYING SAUCERS!
Under cover of darkness in rural areas of course. And 'they' still get seen all the time. I mean come on, if they really wanted to be all secret and stealth, THEY GOTTA TURN OFF ALL THOSE LIGHTS ON THEIR FLYING SAUCERS!
Don't forget that trailer parks send out the abduction signals as well...
Actual contrails are caused by water in the engine's exhaust condensing (hence, "con"-trail) in the very cold air at high altitudes. It's not just jets that produce them; anything that leaves exhaust containing water vapor will leave a contrail in cold air. So, the presence or absence of actual contrails depends on what sort of exhaust you think Traveller maneuver drives produce. If the "burn" hydrogen, they definitely leave a contrail. But it's pretty well assumed that some sort of fusion is involved, rather than burning. That just leaves the question of venting waste heat. If a water-based coolant is used, you could still get vapor (think of those giant cooling towers at nuclear reactors).
In other words -- there's no clear answer. It really depends on whether you want them or not. You could even postulate that in a normal oxy-nit atmosphere, there's no contrail, but in certain exotic atmospheres, there is.
Steve
In other words -- there's no clear answer. It really depends on whether you want them or not. You could even postulate that in a normal oxy-nit atmosphere, there's no contrail, but in certain exotic atmospheres, there is.
Steve
Theophilus
SOC-13
Actaully, even at the slow speeds of propeller driven fighters during WWII wing tip trails were visible.
Don't forget that trailer parks send out the abduction signals as well...
It must piggyback on the Tornado Attraction Signal.
o:Easterner9504
SOC-13
Contrails
Bomber formations left massive contrails.
I recall in the P40 dogfight in Tora, Tora, Tora a wing contrail is visible.
Bomber formations left massive contrails.
I recall in the P40 dogfight in Tora, Tora, Tora a wing contrail is visible.
BlackBat242
SOC-14 1K
The bomber contrails were exhaust condensation... the ones in the movie are a common phenomenon at low altitudes in high-humidity conditions... the disturbed air is temporarily unable to keep the water it is carrying in vapor form, and some condenses into visible droplets.
For example: RAF Tornado F.3 in the Welsh hills July 2007:
Or this USAF F-15E in the same place on a different day:
For example: RAF Tornado F.3 in the Welsh hills July 2007:
Or this USAF F-15E in the same place on a different day:
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Icosahedron
SOC-14 1K
Fighters produce a lot of air disturbance and that type of contrail isn't going to significantly raise your visibility. How fast you come in, how aware you are of displacement contrails, etc, could be a factor of pilot skill. You want to come in stealthily - roll for it.
Looks like there is no definitive answer - you have a contrail if the Ref says you do, and science places the Ref under no constraints one way or the other.
I think the OP was talking about meteor-like fireballs lighting up the sky, though. I'd say you only get one of those if there is something VERY wrong with your landing - roll 12+ to survive...
Looks like there is no definitive answer - you have a contrail if the Ref says you do, and science places the Ref under no constraints one way or the other.
I think the OP was talking about meteor-like fireballs lighting up the sky, though. I'd say you only get one of those if there is something VERY wrong with your landing - roll 12+ to survive...
We have a winner.
Another issue is ionisation. Even without a contrail there will be an ionised path that will be detectable. These days they are used for amateur radio communication extension - you bounce the signal off the ionised path of an incoming meteor to extend range.
As for coming in slowly I remember something about orbital velocities not really allowing a slow landing at all. Grav (or other blackbox HighTech handwavium) of course can alleviate that. I am sure someone with a better grasp of the physics involved could elucidate.
Icosahedron
SOC-14 1K
Orbital speed is necessary to combat the planet's gravity in order to maintain a stable orbit.
The problem at TL7 is that there is no cost-effective way of slowing down other than the friction of atmospheric braking - otherwise you'd need as much fuel to get down as you took to get up. This means a fast and hot re-entry is the only way to do it.
If you have grav tech, however, you have other choices. You may just hang in the sky rather than attain true orbit, or you can slow down from true orbit whilst maintaining altitude, and hang in the sky before lowering yourself slowly to ground.
I suspect ionisation is a result of speed and atmospheric friction, too.
The problem at TL7 is that there is no cost-effective way of slowing down other than the friction of atmospheric braking - otherwise you'd need as much fuel to get down as you took to get up. This means a fast and hot re-entry is the only way to do it.
If you have grav tech, however, you have other choices. You may just hang in the sky rather than attain true orbit, or you can slow down from true orbit whilst maintaining altitude, and hang in the sky before lowering yourself slowly to ground.
I suspect ionisation is a result of speed and atmospheric friction, too.
Drakon
SOC-14 1K
Emphasis mine.
It would depend on how fast it is travelling. A few years ago, the shuttle re-entered over northern california, early one morning. I worked nights and things were quiet, so my boss and I stepped outside to watch it. I spotted a tiny, moving star. I thought that was the shuttle. It wasn't.
Then this red flare bright redy light came over the western hills and traced an arc across the skies. I counted about 6 minutes from horizon to horizon. Very dimly, I could see a smoke trail, against the stars. There was no noise at first, but faintly a dull roar, like a rocket engine, that sounded like it was coming a couple of degrees behind the quickly moving bright red star.
[Yes, I know that a shuttle is a dead stick landing and this was long after the re-entry burn. That the rockets were not burning, but the rumbling roar coming from it could best be described as sounding like a rocket engine.]
It was one of the most wondrous sights I have ever seen, a spaceship coming to earth.
We heard on the radio that the shuttle landed in florida about 10 minutes after we saw it on the west coast.
If you enter the atmosphere with any kind of realistic speed, you would hear sonic booms not far from the landing sight. Heck some planetary governments may demand a sort of burn in re-entry to decontaminate the outer hull. And if you burn in, then you will have sonic booms.
I have a weird idea about jump drive and contra grav, based on a number of sources. The drive is essentially a ring that warps the space/time around the ship, forming a bubble, into jump space. A bubble of normal space. With the bubble erected, you get an aurora effect as small particles and dust, even very small meteors, impact the bubble. Ships generally use the bubble as a kind of shielding and end up looking like a fiery red ball (yellow if its faster) during hot re-entry. The shielding field and field emitted by the contra grav plates give off a heat shimmer and at high speeds produce fiery downward pointing spikes.
Drakon
SOC-14 1K
Would you consider Space Ship One TL7? As far as I know, I do not believe there was the heat necessary to create ionization. The whole goal of the floppy wing design was so they would not need heat shielding.
And as I recall, it did have contrails.
I believe you are correct. You need heat to get the ionization. You need moister in the high air to get contrails. And you need speed to get either.
shadowdragon
SOC-12
Space Ship One did not reach orbital velocities- it was on a relatively slow ballistic trajectory the entire run. iirc it wasn't a fast enough "re-entry" to generate significant amounts of heat, therefore the lack of shielding. the "floppy-wing" design was for stability? i dont recall if they ever stated the reason for that particular design feature...
Ran Targas
SOC-14 1K
Contrails are really condensation trails and they come from engine exhaust, so a starship using contra-grav drives would not produce a contrail.
Vapor trails are produced by an object creating an area of low pressure behind it as it passes through an atmosphere where condensation can happen. Basically, vapor trails require:
1. Atmosphere
2. Some sort of vapor in the atmosphere at temperature and/or pressure close enough to condense if energy is applied
3. An object moving through the atmosphere with sufficient resistance to drive the condensation of the vapor by creating a pressure drop.
So, if your F-15 breaks the sound barrier in air sufficiently humid and at the right temperature, it create a pressure wake that produces a vapor trail. If your Type S is diving into a methane atmosphere, creating a low pressure area behind it, and the methane is at a relative concentration high enough and the temperature agrees, it can create a vapor trail.
The photo of the RAF fighter over Britain is a prime example of wing tip vortices where the pressure in the wake is so low that the air can not hold the water in a vaporous state and it spontaneously condenses. This normally happens at low altitudes in areas of high relative humidity; the higher you go, the less common.
Another really cool effect is when an aircraft passes through a cloud and causes it to rain; it looks like someone drilled a hole in the cloud. This effect is called a distrail or dissipation trail. This could also happen with a spacecraft.
Vapor trails are produced by an object creating an area of low pressure behind it as it passes through an atmosphere where condensation can happen. Basically, vapor trails require:
1. Atmosphere
2. Some sort of vapor in the atmosphere at temperature and/or pressure close enough to condense if energy is applied
3. An object moving through the atmosphere with sufficient resistance to drive the condensation of the vapor by creating a pressure drop.
So, if your F-15 breaks the sound barrier in air sufficiently humid and at the right temperature, it create a pressure wake that produces a vapor trail. If your Type S is diving into a methane atmosphere, creating a low pressure area behind it, and the methane is at a relative concentration high enough and the temperature agrees, it can create a vapor trail.
The photo of the RAF fighter over Britain is a prime example of wing tip vortices where the pressure in the wake is so low that the air can not hold the water in a vaporous state and it spontaneously condenses. This normally happens at low altitudes in areas of high relative humidity; the higher you go, the less common.
Another really cool effect is when an aircraft passes through a cloud and causes it to rain; it looks like someone drilled a hole in the cloud. This effect is called a distrail or dissipation trail. This could also happen with a spacecraft.
Drakon
SOC-14 1K
They did. The floppy wing design is to increase drag, to slow the ship down in higher atmosphere, so that it is not going fast enough in the lower air to burn up.
Granted Spaceship One did not hit orbit, but it was falling from over 100 klicks. gravity can get you moving pretty fast.
