Spaceships glow in the dark. If you want anything highpowered on them you have to shed MW of thermal energy, or fry the crew.
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Spaceships glow in the dark. If you want anything highpowered on them you have to shed MW of thermal energy, or fry the crew.
I wonder what power would be required to vaporize a tungsten rod of modern anti-tank sabot shell.
Zkribbler
Deity
No one on a trip to the moon or in the international space station has ever been fried.
NASA has never released any Earth-taken shot of a lunar orbiter circling the moon.
I don't recall ever seeing an Earth-taken shot of the international space station.
Moral of the story: Things in space are very hard to see.
Corollary: ...especially if you don't know where to look.
The ISS can be seen with the naked eye. As for a shot:
https://apod.nasa.gov/apod/ap090116.html
Spoiler :
For an interplanetary spacecraft you sort of would know where to look. Assuming that the craft is in some way constrained by fuel, there are only so many transfer orbits that are actually viable. So even if you didn't know the exact path, you just would have to check around the possible transfer routes and you would find it.
Lunar orbiters are hard to spot, because the light reflected off the moon itself drowns out any other signal. A spacecraft making an interplanetary transfer would be a bright spot against an empty background, so it would be much easier to see. To see something like the ISS at 1 AU distance, you would need something like a 3m telescope (very rough estimate). Currently, there are more than 30 of those operational on Earth. So if you suspected that something was coming and had all resources on Earth available, I don't see how you would be able to miss it. And at that distance and current spacecraft speeds, it would be still months out from arriving at Earth and there would be plenty of time to prepare. In a full-blown interplanetary war with telescopes dedicated to searching spacecrafts, there wouldn't be any element of surprise for the attacker. This would grant a massive advantage to the defender, up to the point where an interplanetary war involving spacecraft between not completely unequal sides wouldn't make sense, because you are never going to be able to mount a successful attack.
You are comparing a primitive capsule against a laserbreathing warship. Even our 1st generation war lasers are in the 10sKW output range, which means you need much more to put in and waste heat to shed. Apollo could only manage 4kW IIRC.
The only way to shed heat in space is radiation or a heat sink but heat sinks are not infinite. So you get brightly glowing radiators standing out against the CMB.
As uppi points out orbits are restricted by the specs of your spacecraft, you'll only need spotwise observations to nail down the location of a ship.
Yes you can hide in the glare of planets, but only for certain angles. And if we are assuming spacebattleships, surveillance probes giving multiple points of view pretty much a given.
Zkribbler
Deity
I didn't know that. Thank you.The ISS can be seen with the naked eye. As for a shot:
https://apod.nasa.gov/apod/ap090116.html
Spoiler :
I still maintain it would be easy for a ship to hide in the vastness of space. Say, you want to go from Planet A to Planet B. You don't go from A to B because you'd be easy to spot.
Instead, you go from A to Point C, do a mid-course correction, and proceed C to B. Point C can be anywhere, so there are an infinite number of possible trajectories. Heat radiation is no problem. The ship can vector the heat away from Planet B, using the ship itself to shield any sight of it.
hobbsyoyo
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I wonder if this was responsible for the pattern of orbits for Kuiper belt objects that people think are caused by a Planet X.
I still maintain it would be easy for a ship to hide in the vastness of space. Say, you want to go from Planet A to Planet B. You don't go from A to B because you'd be easy to spot.
But given the constraints of orbital mechanics, fuel and the orbital parameters of A and B, Point C cannot be anywhere. From the perspective of the sun, Earth moves with about 30 km/s, which is much more than a spacecraft can usually accelerate in total. This means, that any spacecraft launched from Earth will be moving into a similar direction as Earth itself. If you wanted to go, for example, into the reverse direction, you would need more fuel than any spacecraft has ever brought along. Then, Mars moves at 24 km/s, so that in addition to being at the place of Mars at the right time, you also need to match its speed. If you don't do that, you either have a very short flyby before you are flying into space with no hope of return or you have a very violent impact on Mars. This means that for any given launch date the realistic trajectories are quite limited (if there are any at all). Since space is a continuum, saying that there is an infinite number of trajectories is technically correct, but they are so close together that with a few pictures you should be able to cover almost all of the realistic ones.
That was my first thought at well. However, the very same authors published a paper on the hypothetical 9th planet last year so they must be interested in that as well -- yet they make no mention of that in the present paper.
Heat radiation is no problem. The ship can vector the heat away from Planet B, using the ship itself to shield any sight of it.
Didn't I say if you got the tech for space battleships you the capabilities for surveillance satellites spread across the solar system. You cant hide your radiation from all angles.
Thorgalaeg
Deity
You mean to sublimate.
It is very easy to calculate. You need the enthalpies of fussion and vaporization, the specific heats of solid and liquid Tungsten plus the temperatures of fussion and vaporization and finally initial temperature of the rod and total mass of the rod.
(Ah, and atomic mass of Tungsten)
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Yeah, piece of cake.
Energy losses due to radiation will be high. I don't know at what temperature tungsten evaporates in vacuum, but assuming it's around 2000K, square meter of its surface will be radiating about 1 megawatt into space
If I correctly applied Stephan-Boltzmann law.
If we use very powerful laser, may be it will make the rod glowing red before it pierces through spaceship. To make sure it doesn't stuck
Berzerker
Deity
https://phys.org/news/2018-03-earth-impact-creation-moon.html
More evidence the proto-Earth had plenty of water before the impact creating the Moon
That means water saturated the inner solar system contradicting existing theory, or this collision between the proto-Earth and the impactor to form the Moon happened further away from the Sun.
or
the proto-Earth formed here but somehow acquired more distant water before the impact
More evidence the proto-Earth had plenty of water before the impact creating the Moon
That means water saturated the inner solar system contradicting existing theory, or this collision between the proto-Earth and the impactor to form the Moon happened further away from the Sun.
or
the proto-Earth formed here but somehow acquired more distant water before the impact
hobbsyoyo
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The Chinese space station is expected to re-enter this weekend and no one can say where it will come down yet. It is large enough that some pieces will make it to the ground.
Blue Origin stated that they have changed the engine on the second stage of New Glenn. They were going to use a vacuum version of the BE-4 engine (Methane/Oxygen - used for the first stage) but have switched to using the BE-3U (a sea level version is used on New Shepard and it's on the 3rd stage of NG). This will allow them to only develop 2 engines for the rocket instead of 3. They also say that this will allow the 2-stage version to compete for all USAF contracts where previously it could only do some and they would have to develop the 3-stage for the rest. The new 2nd stage will likely be stretched to accommodate the rare* hydrogen fuel and will use two of the BE-4 engines which will produce roughly 2/5 of the thrust of the BE-4.
*rare in the sense of not dense
Blue Origin stated that they have changed the engine on the second stage of New Glenn. They were going to use a vacuum version of the BE-4 engine (Methane/Oxygen - used for the first stage) but have switched to using the BE-3U (a sea level version is used on New Shepard and it's on the 3rd stage of NG). This will allow them to only develop 2 engines for the rocket instead of 3. They also say that this will allow the 2-stage version to compete for all USAF contracts where previously it could only do some and they would have to develop the 3-stage for the rest. The new 2nd stage will likely be stretched to accommodate the rare* hydrogen fuel and will use two of the BE-4 engines which will produce roughly 2/5 of the thrust of the BE-4.
*rare in the sense of not dense
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Berzerker
Deity
I live near or in the belt of likely descent... I'll have to keep updated on that, they say we might be able to see it burn up
Wouldn't it be absolutely creepy if Ben Bova turned out to be right? His Venus novel is the stuff of nightmares.
But the Russian Venera missions found no life when they landed. Or were they looking?
Thorgalaeg
Deity
I think Veneras didnt carry the needed instruments to detect life as mass spectrometers and such, and even if so they didnt last that much once on the surface. Venus is not a very nice place. Anyway there are apparently evidence of life everywhere but they never find anything. Till i have an alien pet playing with my socks i will not believe a word.
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Berzerker
Deity
The Chinese space thingie is supposed to burn up on re-entry tomorrow. It's gonna hit the atmosphere at ~26km/h. Okay, why does stuff hit the atmosphere and burn up? I can understand a meteor doing that but this craft isn't really behaving like a meteor. Cant a ship enter the atmosphere 'gently' by matching the speed of the upper atmosphere?
