What kind of military spacecraft can we create with current technology?

[RainDreamer]

57 minutes ago, DDE said:

OP, have you ever considered Children of a Dead Earth? It fits your mandate for "proven technology only".

Yeah, this thread was made waay before I heard of it though, like a year ago. Someone just brought it back up today and I thought I should fix the scenario a bit.

Honestly though, I can't imagine a scenario where the military space race don't end up in trashing LEO and no one get to space anymore, even if it is between moon colonists and earth. So likely no one is planning to go do it, realistically. Doesn't mean we can't speculate though!

[DDE]

8 minutes ago, RainDreamer said:

Honestly though, I can't imagine a scenario where the military space race don't end up in trashing LEO and no one get to space anymore, even if it is between moon colonists and earth.

Asset denial via scorched earth (har-har) is the smart response to a superior enemy. I have it in my fictional WWIV scenario.

[Kryten]

17 minutes ago, RainDreamer said:

Honestly though, I can't imagine a scenario where the military space race don't end up in trashing LEO and no one get to space anymore, even if it is between moon colonists and earth. So likely no one is planning to go do it, realistically. Doesn't mean we can't speculate though!

 Not much military infrastructure is in LEO right now, so this isn't necessarily true in a near-term scenario. It's limited to maybe a dozen his-res recon sats in the worst case (the US) and the Iridium constellation, and Iridium is low-throughput enough that it's probably not worth targeting.

[Core]

My idea for a modern attack space craft would involve a high efficiency propellant (probably xenon ion thrusters), with .50 cal machine guns that utilize a secondary cancellation shell to prevent the guns from being thrusters too. If the fighter is built strictly for space, then a pressurized cockpit could be skipped by using a space suit instead, with auxillary oxygen tanks.

[DDE]

4 minutes ago, Core said:

a high efficiency propellant (probably xenon ion thrusters)

They cannot be used to get anywhere in a tactically useful amount of time, and can't be used to dodge at all.

I'd suggest hydrazine with ClF₅ oxidizer.

[Core]

25 minutes ago, DDE said:

They cannot be used to get anywhere in a tactically useful amount of time

I figured as much. The only time I managed to get something to go fast on KSP with those thrusters was when the craft weighed less than 2 tons.

But I would expect early space combot to be drastically different from air combat and future space combat. Maybe dodging will not be something easily and efficiently possible.

[DDE]

26 minutes ago, Core said:

I figured as much. The only time I managed to get something to go fast on KSP with those thrusters was when the craft weighed less than 2 tons.

But I would expect early space combot to be drastically different from air combat and future space combat. Maybe dodging will not be something easily and efficiently possible.

The guy behind Children of a Dead Earth has concluded that just sitting in one place (or firing an electric rocket - same thing) leaves you exposed even to conventional cannons, let alone railguns, dozens of them. Technicolor traces mandatory, of course.

 

Edited September 16, 2016 by DDE

[Emperor of the Titan Squid]

On June 4, 2015 at 3:22 PM, KSK said:

This sounds very Footfall to me.

To answer OP's question, probably an Orion powered ship loaded up with all manner of nuclear nasties. Whether we'd ever get a chance to deploy it before it gets clobbered with a rods-from-god kinetic weapon, is another question.

We would probably put it underground. But that might take just as much energy as building the ship. I suggest that we place it  in Area 51, to keep it inconspicuous and for awesomeness factors.

I would suggest that we build a Michael style battleship, but with casaba howitzers and nuclear misses like the Orion battleship.  Plus some railguns, and maybe gauss cannons, equipped with shells, penetrator shells, nuclear shells, and metal rods. Also, I would suggest laser cannons, and phalanx systems for anti missle combat.  With burn space shuttles, fully equipped with fighters and nukes. Although, America couldn't get its hands on those.

[DDE]

4 minutes ago, Emperor of the Titan Squid said:

With burn space shuttles, fully equipped with fighters and nukes. Although, America couldn't get its hands on those.

You're free to try scratching off the bird crap.

There is, however, this American Buran:

 

[YNM]

Probably some large ICBM or intercept rockets launch source all over the Earth. Being in orbit is halfway to anywhere, so stopping the first half (ground to orbit) is always enough.

[DDE]

16 hours ago, YNM said:

Probably some large ICBM or intercept rockets launch source all over the Earth. Being in orbit is halfway to anywhere, so stopping the first half (ground to orbit) is always enough.

Yes, and it takes much less dV to kill something in orbit than to put something in orbit.

[Frozen_Heart]

On ‎16‎/‎09‎/‎2016 at 8:38 PM, Core said:

My idea for a modern attack space craft would involve a high efficiency propellant (probably xenon ion thrusters), with .50 cal machine guns that utilize a secondary cancellation shell to prevent the guns from being thrusters too. If the fighter is built strictly for space, then a pressurized cockpit could be skipped by using a space suit instead, with auxillary oxygen tanks.

A modern prototype laser weapon on a simple satellite or spacecraft could swat something like that several light seconds away most likely. No dodging or avoiding possible, just instant rupturing of the fuel tanks. Some hydrazine thrusters for propellant and cold gas and reaction wheels for turning. Also why bother with a cockpit? Just make it a drone so it is cheaper, expendable, and smaller.

Guns are pointless in space, with even high velocity railguns being too slow moving, let alone 50 cals.

[Jmm85]

I saw a couple of posts about evasive maneuvers almost dogfighting in space.   I just want to ask if anyone had read up on real air to air combat as exsists today?   Most endangerment are from across horizon, well beyond visual range wroth long range missiles.   Space ranges would increase drastically making combat less about pilot skill and more a senor arms race.  If talking lasers dogding impossible, flat out no way to detect before hit. Rail guns near impossible,  to point decaying is almost silly.   Rockets at long range can be dodged if detected early though if have that detection capability would be easier to destroy and not waste fuel. 

Eratic hetic dogfights are nonsense at ranges likely if combat moved up, its almost extinct now.

[DDE]

48 minutes ago, Frozen_Heart said:

A modern prototype laser weapon on a simple satellite or spacecraft could swat something like that several light seconds away most likely. No dodging or avoiding possible, just instant rupturing of the fuel tanks. Some hydrazine thrusters for propellant and cold gas and reaction wheels for turning. Also why bother with a cockpit? Just make it a drone so it is cheaper, expendable, and smaller.

Lasers aren't exactly that good. It takes the currently available ones a while to burn through anything; it's far from being able to instantly rupture anything, let alone something that has a lot of cool liquid in it.

And most definitely not a light-second away. Ever heard of beam waist and diffraction?

48 minutes ago, Frozen_Heart said:

Guns are pointless in space, with even high velocity railguns being too slow moving, let alone 50 cals.

13 minutes ago, Jmm85 said:

Rail guns near impossible,  to point decaying is almost silly.   Rockets at long range can be dodged if detected early though if have that detection capability would be easier to destroy and not waste fuel. 

Disagreement!

It would take even railguns several seconds to reach a target at a realistic range. That gves enough time to dodge.

If you haven't noticed, fighter jets do that to missiles, too.

Edited September 17, 2016 by DDE

[Jmm85]

Missiles are slow in comparison to rail guns, hence small non explosive payload vs high explosive, with guidence.  To dodge something means seeing it,  calculating trajectory,  and using that information.  We don't have the tech at reasonable distance to do that with something hyper sonic workout a lot of distance. The realitive small size of the projectile from a rail gun complicates this.  Also dodging missiles rare outside movies, that's why fighters use radar jamming, stealth, flares, chaff to confuse their guidence.

[Core]

Imagine orbital sniping from space station to space station. One bullet flying through space to hit a target on the other side of the planet. That would be neat. I would think surgical shots such as that to be more likely in space combat, but rendevous between target and bullet would depend largely on:

1: Target not changing course

2: Target being unaware

3: Very precise shots

[DDE]

11 hours ago, Jmm85 said:

Missiles are slow in comparison to rail guns, hence small non explosive payload vs high explosive, with guidence.  To dodge something means seeing it,  calculating trajectory,  and using that information.  We don't have the tech at reasonable distance to do that with something hyper sonic workout a lot of distance. The realitive small size of the projectile from a rail gun complicates this.  Also dodging missiles rare outside movies, that's why fighters use radar jamming, stealth, flares, chaff to confuse their guidence.

Yes, but once you detect the railgun firing - easily, the muzzle flash is going to be quite vivid - you can start dodging randomly, "drunkwalking"; almost any change in trajectory will be enough to foul up their firing solution.

10 hours ago, Core said:

Imagine orbital sniping from space station to space station. One bullet flying through space to hit a target on the other side of the planet. That would be neat. I would think surgical shots such as that to be more likely in space combat, but rendevous between target and bullet would depend largely on:

1: Target not changing course

2: Target being unaware

3: Very precise shots

Any spacecraft easily detectable by infrared. Muzzle flash easily detectable on IR. Whoops.

[pyrosheep]

13 hours ago, Jmm85 said:

Also dodging missiles rare outside movies, that's why fighters use radar jamming, stealth, flares, chaff to confuse their guidence.

It depends what you mean by dodging.

If you mean movie style dodging where the missile rocket motor is burning, the fighter does a sharp jink and the missile flies right by (and sometimes turns back to attack the fighter again -Shudders-), then you are right, that doesn't happen these days, a missile with energy is way more manoeuvrable than a fighter Aircraft (generally 4 times more manoeuvrable) and against missiles 00s onward countermeasures like chaff and flares generally do squat.

However missiles are still limited by drag and deltaV (and gravity to a lesser extent).

A missile's maximum range is generally given for a specific specific situation where the attacking and defending aircraft are flying head on at each other at high speed and high altitude. In this scenario the missile and the defending fighter are going towards each other so the distance the defending fighter travels in the time it takes for the missile to get there adds to the missiles range; if that fighter simply turns sideways or around, after the missile is fired, it will remove that added range and the missile will fall short.

This is why missiles have NEZ (no escape zones), a range where even if the fighter turns around completely, going 'cold', the missile will still reach it.

There are other ways to reduce the effectiveness of missiles as well: while they can turn hard when they have energy, they use up energy very fast when turning. Because of their limited deltaV a missile can only do so much turning before it runs out of energy completely and essentially becomes a lawn dart; fighters can use this by forcing the missile to make many maneuvers on it's way to the target and use up it's energy, so that if it gets there, the missile has low energy and the fighter can dodge it with an appropriate maneuver. Missiles have lead guidance, so if the fighter turns one way and then the other (called cranking), soon after the missile is launched, it forces the missile to predicatively aim ahead of the fighter back and forth causing it to lose allot of energy, as well as reducing the closure rate of the defending fighter to the missile.

Missiles also have more drag at lower altitudes so it can sometimes be a good idea for the fighter pilot to dive to reduce the missile's range (at high mach drag matters more than gravity for the missile's energy), this also works well with Notching, a technique for confusing radars that rely on Doppler shift to disern targets from ground clutter (basically, when a something is moving towards or away from you relative to the ground, the radar return is doppler shifted relative to the ground, however, if that thing moves at the same speed relative to the ground the doppler shift becomes the same as the ground and it can disappear into the ground clutter - so if pilots fly with the enemy radar direction normal to their velocity vector with the ground behind them, they can break a lock-), i'm not sure how well this works with modern AESA radars though. 

Jamming and stealth generally don't do much for losing missiles, the whole point of them is to prevent getting detected/prevent a launch solution in the first place.     

Edited September 18, 2016 by pyrosheep

[kerbiloid]

The first Interstellar Battleship really engineered (just still not built) by humanity.

Project Daedalus.
Two-stage anti-planetary homing missile with 450 t kinetic warhead.
A world killer, A hammer of faith.

A two-staged thermonuclear booster accelerates a 450 t kinetic warhead up to 0.1 c speed, aiming to a potentially habitable planet system, as close to the target planet as it's possible.

After the booster has burnt out and decoupled, the warhead floats through the space with no option to stop or to avoid a collision. (Again: targeted as close as possible to a potentially habitable planet).

Also, it hasn't self-destruction option. Even if it misses the primary target, it stays running with 0.1 c speed. Sooner or later it will crash into at least something. Even if its electronics has gone billions years ago.
It's effective: who said that a civilization in a galaxy far far away, which will be hit by this warhead 100 million years later, would never be a danger for us.

Once it meets a target planet, it crashes into the planet with
(let's calculate: 450*10³ * (0.1 * 3*10⁸) / 2 / 4.2*10¹⁵ ~= 48 000)
50 000 megatons of kinetic energy, love and adoration.

Any potentially hazardous civilization will be eliminated by one relativistic kinetic warhead scientific probe in one flash and several hours of destruction.

P.S.
And probably this is the most possible explanation of Fermi paradox.
Once a sentient race achieves this technical level, it starts sending kinetic warheads peaceful scientific probes to any potentially habitated planet in 100 l.y. around. With a lethal accuracy.

Edited September 18, 2016 by kerbiloid

[Diche Bach]

"Hammer of Faith" that has a real ring to it . . .

On 9/16/2016 at 3:44 PM, DDE said:

They cannot be used to get anywhere in a tactically useful amount of time, and can't be used to dodge at all.

I'd suggest hydrazine with ClF₅ oxidizer.

Given that degree of maneuverability, why bother with ballistic weapons? Just send them up with grappling hooks, a "can opener" and some machetes = far less likely to blow a hole in your own fuel tank.

I cannot even comprehend how hard it would be to hit a target moving at 8km/s with a machine gun . . .

Edited September 18, 2016 by Diche Bach

[DDE]

1 hour ago, kerbiloid said:

The first Interstellar Battleship really engineered (just still not built) by humanity.

Project Daedalus.
Two-stage anti-planetary homing missile with 450 t kinetic warhead.
A world killer, A hammer of faith.

A two-staged thermonuclear booster accelerates a 450 t kinetic warhead up to 0.1 c speed, aiming to a potentially habitable planet system, as close to the target planet as it's possible.

After the booster has burnt out and decoupled, the warhead floats through the space with no option to stop or to avoid a collision. (Again: targeted as close as possible to a potentially habitable planet).

Also, it hasn't self-destruction option. Even if it misses the primary target, it stays running with 0.1 c speed. Sooner or later it will crash into at least something. Even if its electronics has gone billions years ago.
It's effective: who said that a civilization in a galaxy far far away, which will be hit by this warhead 100 million years later, would never be a danger for us.

Once it meets a target planet, it crashes into the planet with
(let's calculate: 450*10³ * (0.1 * 3*10⁸) / 2 / 4.2*10¹⁵ ~= 48 000)
50 000 megatons of kinetic energy, love and adoration.

Any potentially hazardous civilization will be eliminated by one relativistic kinetic warhead scientific probe in one flash and several hours of destruction.

P.S.
And probably this is the most possible explanation of Fermi paradox.
Once a sentient race achieves this technical level, it starts sending kinetic warheads peaceful scientific probes to any potentially habitated planet in 100 l.y. around. With a lethal accuracy.

50 gigs? After several decades of collecting He₃ for a single launch?

Get real and have 10 gigs right away.

[kerbiloid]

2 minutes ago, DDE said:

50 gigs? After several decades of collecting He₃ for a single launch?

We can't wait for decades just to annihilate a planet of puny ET...

4 minutes ago, DDE said:

Get real and have 10 gigs right away.

So, in general we have reached a consensus. Just need to elaborate details.

[Diche Bach]

3 hours ago, kerbiloid said:

We can't wait for decades just to annihilate a planet of puny ET...

So, in general we have reached a consensus. Just need to elaborate details.

You can count me out on that consensus. I'm still going for my "grappling hooks, can opener and machetes" boarding parties approach.

Too easy to miss with a 50 Gigs, multi-billion funds  relativistic kinetic warhead scientific probe.

NOT so easy to miss with a small, highly maneuverable, capsule with a couple of grappling hook/can opener/machete wielding roughnecks inside.

 

Edited September 18, 2016 by Diche Bach

[kerbiloid]

1 minute ago, Diche Bach said:

You can count me out on that consensus. I'm still going for my "grappling hooks, can opener and machetes" boarding parties approach.

Too easy to miss with a 50 Gigs, multi-billion funds  relativistic kinetic warhead scientific probe.

NOT so easy to miss with a small capsule with a couple of grappling hook/can opener/machete wielding roughnecks inside a highly maneuverable capsule.

 

Yes, a space myoparo definitely has its own advantages, this is undoubted.

 

But in fact I haven't tried to invent a battleship. I'm just currently reading a sci-fi book (Robert Ibatullin, "Rose and worm"), where an alien civilization killed the Earth with 0.5 c relativistic 100 kg carbon arrows.

And just thought:: when Daedalus authors had invented a 450 t boilerplate rushing on 0.1 c through a potentially habitable planetary system
(by default habitable, otherwise why to send a over-expensive  probe to that system),
wasn't it rather horrific for them, that this thing has no brakes or evasive possibilities and is aimed as close to the planet of interest as they even can.

And that in the infinite space it will fly maybe for billions years and absolutely sure will crash into something, releasing 50 000 Mt of energy.

Would they like if such thing were flying through LEO?

[Core]

If you can do it KSP (w/o unreasonable mods), you can do it in real life. Which proves all of my KSP craft to be examples for what the military should do (or not do).