The thread for space cadets!

[timtofly]

The jury is still out concerning things like "fighters" in space.

Atomic Rockets uses to explain why it's fallacious to think of "fighters" in space in the same terms we think about aircrafts taking off from carriers here on Earth as follows:

the main difference is, that on earth, fighter planes launched from carriers move in a different medium than the ships that launched them, i.e. air as opposed to water, respectively. This is the main source of their advantage - the air resistance is far lesser, so they can move many many times faster. They can move far above the '2D' world of the ships and again use their '3D' nature to their advantage. Ships are, compared to airplanes, stationary targets that can be repeatedly attacked after which the attacking airplane rapidly retreats to safety.

In space, there is only one medium - vacuum. Small fighter-like spaceships launched from a bigger spaceship don't have any of the advantages of an Earth-based fighter plane; the medium and the 3D nature of space is the same.

To explain how this is different one should take a look at small attack craft in Earth navies. It has been tried to deploy a swarm of smaller, faster, more manoeuvrable ships to attack larger ships. In the period before WW1, people thought that smaller boats rapidly closing on the big-bun battleships and sinking them with torpedoes might be a viable strategy. In the end, the torpedo-boat destroyer (now known just as 'destroyer' and considered a major surface ship) was developed to 'screen' the big ships from exactly these types of attack, and the strategy was found not viable.
Right now, in this day and age, the Iranians and other rogue(ish) countries are developing small, very fast missile boats, again hoping to overwhelm and cause damage to large advanced fleets of their 1st world enemies. It remains to be seen whether that can work or not - my guess is it won't, except under very specific circumstances. Furthermore, these smaller ships don't handle open seas well and their endurance is limited, so it's not practical to use them anywhere but very close to the shore.

So, here you go. In space, your fighters are not real fighters, but more like little speedboats or torpedo-boats. They are small, their armour is weak, their endurance is limited, so what is their advantage, really? You need to come up with some serious advantage that makes them worth the trouble.

The advantages I can see:
— manoeuvrability (i.e. ability to get closer to the enemy fleet and not be hit, since the chance to hit a target is a function of the speed of the projectile and the ability of the target ship to dodge the projectile.)
— multiple attack vectors (i.e. you can swarm the enemy fleet from more than one direction simultaneously. Combined with a large number of missiles and decoys to saturate the enemy point defences, this can open a crack in the fleets defence zone for a strike force to get close and score hits with 'torpedoes' - heavy, ship-killing missiles).
— precision attacks (if the fighter/bombers get close enough and use their lighter weapons to accurately attack enemy ships' guns, point defences, missile ports, engines, etc., they can soften it up for the main battle fleet.)

In any case, I wouldn't want to be a pilot in these things, because the casualties to point-defence fire would be HORRENDOUS. I think it would be common for the fighter force to lose over 50% of their strength in just one attack. I guess for this reason, most of the ships would be automated and piloted by AIs, with perhaps a few of 'squadron leader' fighters piloted by humans to direct the unmanned vehicles.

Thank you for the analysis.

 

[Winner]

Why should coherence loss be a problem? There is little coherence involved in doing damage with a laser. What is a problem is that every laser beam has a small divergence that leads to a large spot at long distance. So you have to work with large beam diameters and high intensities.

That is what I meant. Is "coherence" a wrong word?

The biggest problem is that spaceships are usually from aluminum, which has a high reflectance for light. After a bit of polishing (and any combat involving lasers will involve very shiny combatants sooner or later) most of the laser light is simply reflected without doing damage. It is also a very good heat conductor, so doing thermal damage is extra difficult.

I doubt lasers at intensities we're talking about can be safely reflected. I need to check that out. But I am for anything that makes them less useful in space combat...

And I don't think there is such a thing as a maximum range for point defense guns in space (unless you are shooting out of a gravity well and your projectiles are below escape velocity). The maximum range will be determined by how far away the other spaceship can comfortably dodge the salvo.

And that's what I meant by "range", i.e. the ability to hit the target with any reasonable accuracy.

I am wondering what kind of point defences may be used, since lasers don't strike me as weapons with a particularly big stopping power.

 

[hobbsyoyo]

I doubt lasers at intensities we're talking about can be safely reflected. I need to check that out. But I am for anything that makes them less useful in space combat...

These are my thoughts exactly. People tend to immediately go for 'reflective coatings' when lasers come up in space combat but unless a coating can be 100% reflective (probably impossible) then some will energy will be absorbed. At the intensities we assume for useful laser weapons, it won't take much to vaporize the (probably fragile) reflective coating.

The only tactic I could think of working is having an extremely reflective coating over an effective heat-sink material and then spinning your ship. The absorptive material underneath could soak up some heat and the spinning of the ship would reduce the chance that any one spot would be under a laser beam for a significant amount of time. However, if the distances are under a light second you could traverse the turret that is shooting so that the same spot on the spinning hull is continuously hit until it moved out of the line of sight.

 

[bhsup]

What about masers?

 

[hobbsyoyo]

Hmmmmmmmm.....

that would be interesting used against a metal-hulled ship. But the wavelength of a maser is going to be longer than that of an optical laser, (IIRC) so it will deliver less energy for the same amount of power. I think???

 

[bugwar]

Using NASA’s Hubble Space Telescope, two research teams have discovered thick layers of high-altitude clouds covering the atmospheres of two relatively nearby exoplanets: a super-Earth and a "warm Neptune."

http://www.latimes.com/science/scie...planet-20131231,0,7717645.story#ixzz2p6hN0PN9


I am flabergasted that this is at all possible.

 

[Cutlass]

Why should coherence loss be a problem? There is little coherence involved in doing damage with a laser. What is a problem is that every laser beam has a small divergence that leads to a large spot at long distance. So you have to work with large beam diameters and high intensities.

The biggest problem is that spaceships are usually from aluminum, which has a high reflectance for light. After a bit of polishing (and any combat involving lasers will involve very shiny combatants sooner or later) most of the laser light is simply reflected without doing damage. It is also a very good heat conductor, so doing thermal damage is extra difficult.

I don't think lasers are particularly useful for blinding sensors. The sensors are usually broadband and (cw) laser light is very narrowband light. So you just put a tunable filter in front of your sensor and you can still use it. In the visible and near infrared spectrum you could try to broaden your spectrum by using femtosecond pulses, but in the mid-infrared this is going to be difficult.

And I don't think there is such a thing as a maximum range for point defense guns in space (unless you are shooting out of a gravity well and your projectiles are below escape velocity). The maximum range will be determined by how far away the other spaceship can comfortably dodge the salvo.

Dispersion will place an effective maximum range on it, even though the projectiles travel further. It will become prohibitively difficult to actually hit the target at some range.

 

[timtofly]

Pre-cognitive firing?

 

[uppi]

That is what I meant. Is "coherence" a wrong word?

Coherence is the term for a different property of lasers that does not matter in this context. The divergence of a laser is pretty much independent of its coherence. So even a perfectly coherent beam would not help at all. You would need coherence to do interferometry to get sub-wavelength resolution on range finding for example, but that's not going to matter in space combat.

I doubt lasers at intensities we're talking about can be safely reflected. I need to check that out. But I am for anything that makes them less useful in space combat...

With the right mirrors you can reflect very high intensities, but in practice you are not going to have supermirrors all over the hull of your spaceship (and those might just protect against a particular wavelength).

However, even if there is no absolutely safe reflection, every bit of reflectivity helps. If you can get the hull to reflect 90% of the incoming light (which can be done with aluminum over a very broad spectrum), then you only have to care about the remaining 10%. So either the attacker needs a laser 10 times as powerful, or you have 10 times more time to dodge or engage with your own weapon systems until the damage becomes critical.

In addition, the maximum power that is still safe depends on how fast you can get the heat away (For high power lasers you can actually get watercooled mirrors for heat management). As the heat conductivity of aluminum is quite good, you can quickly get the heat away from critical spots. So aluminum is one of the materials that are very resistant to damage with lasers. I have a laser that starts to evaporate glass in milliseconds, but does no damage to a thin sheet of aluminum foil.

 

[PlutonianEmpire]

Being a huge weather enthusiast, I thought this bit about brown dwarfs was interesting:

http://www.jpl.nasa.gov/news/news.php?release=2014-005

Swirling, stormy clouds may be ever-present on cool celestial orbs called brown dwarfs. New observations from NASA's Spitzer Space Telescope suggest that most brown dwarfs are roiling with one or more planet-size storms akin to Jupiter's "Great Red Spot."

Scientists think that the cloudy regions on brown dwarfs take the form of torrential storms, accompanied by winds and, possibly, lightning more violent than that at Jupiter or any other planet in our solar system. However, the brown dwarfs studied so far are too hot for water rain; instead, astronomers believe the rain in these storms, like the clouds themselves, is made of hot sand, molten iron or salts.

 

[PlutonianEmpire]

I'm not gonna become the only one keeping this thread alive, aren't I?

Anyways; Kepler apparently caught a type Ia supernova:

http://www.nature.com/news/kepler-clue-to-supernova-puzzle-1.14513

They are cosmic detonations that briefly outshine the light of entire galaxies. And they were a crucial tool in the discovery of dark energy, the force that is accelerating the expansion of the Universe. Yet the process that gives rise to type Ia supernovae has remained mysterious.

Now, light from two of these stellar explosions has been captured in finer temporal detail than ever before, and the data are adding weight to an emerging view: that the explosions result from the merger of two white dwarfs, the burnt-out, Earth-sized remnants of Sun-like stars. The finding erodes a long-standing view that type Ia supernovae arise from a single white dwarf accruing material from an ordinary companion star, either a Sun-like star or an elderly, bloated red giant.

The data have come from an unlikely source: NASA’s Kepler mission, the space telescope that searched for alien planets by staring at some 150,000 stars in nearby reaches of the Milky Way. Distant galaxies also lurk in the telescope’s field of view, and its ability to collect data every 30 minutes, along with its sensitivity to tiny changes in brightness, made it ideal for recording the rise and fall of light emitted during supernovae.

Pretty cool.

 

[bugwar]

I'm not gonna become the only one keeping this thread alive, aren't I?

Sure, why not?

If I find something interesting, I will post it.
But how often does something in the heavens become newsworthy?

 

[PlutonianEmpire]

Given the state of human society, Westerners in particular, and of the media, I wouldn't be surprised if space aliens blatantly landed on the WH lawn and made first contact, and it is only a 30 second news bit on the evening news that evening.

 

[timtofly]

Given the state of human society, Westerners in particular, and of the media, I wouldn't be surprised if space aliens blatantly landed on the WH lawn and made first contact, and it is only a 30 second news bit on the evening news that evening.

It would only make the news if they shot at somebody. If they came in peace, we would hear about it 55 years later.

 

[Crezth]

Given the state of human society, Westerners in particular, and of the media, I wouldn't be surprised if space aliens blatantly landed on the WH lawn and made first contact, and it is only a 30 second news bit on the evening news that evening.

What are you basing this on, other than a misanthropic jealousy of people who socialize occasionally?

 

[PlutonianEmpire]

Nothing, I was deliberately exaggerating. (Dunno if that's the right word for it.)

 

[warpus]

Not sure if this has already been posted or not, but here's a countdown thingy for a spacecraft that is about to "wake up" and land on an asteroid or something.

 

[peter grimes]

Not sure if this has already been posted or not, but here's a countdown thingy for a spacecraft that is about to "wake up" and land on an asteroid or something.

Yes and no.. Rosetta is like Cassini, it's not going to land on a Comet. It's got a slave vehicle (akin to huygens) that will actually attempt a landing.

 

[warpus]

Well at least I got some of those words right!

 

[bhsup]

Wakey wakey, Rosetta! Rosetta probe awaking to meet comet

Rosetta, Europe's decade-long quest to put a robotic lander on a comet, has reached a key milestone.

The probe, which has spent the past two-and-half-years moving through space in a deep sleep, was expected to rouse itself at 10:00 GMT, ready to send a signal to Earth.

Receipt of this "I'm awake" message will confirm the great endeavour is still on course.

Rosetta is due to rendezvous with Comet 67P/Churyumov-Gerasimenko in August.

The despatch and landing of the small robot currently piggybacking the probe is set for November.

The reactivation of Rosetta is occurring some 800 million km from Earth, out near the orbit of the planet Jupiter.

Controllers at the European Space Agency's (Esa) operations centre here in Darmstadt, Germany, do not know precisely when Monday's all-important contact will be made, but they anticipate their consoles lighting up sometime between 17:30 and 18:30 GMT.