Whay would real-life war spacecraft look like?

[razark]

On 6/4/2017 at 9:23 AM, wumpus said:

There were also thousands of ICBMs deployed, but none so far has been launched armed (and presumably never tested with actual warheads).

I am unaware of any ICBMs, but Operation Dominic - Frigate Bird tested an SLBM.

[Joseph Kerman]

What I think the first space fighters will be like?

 

Scramjets: They will be large blended wing or lifting body fighters with an inline turboscramjet and final insertion thrusters for orbital insertion. They will have to carry some batteries as well, for life support and the weaponry. We would most probably be using a laser, at least 30 kW. Re-entry will involve using retro-thrusters to push perigee below 70,000 m for aerobraking.

Ion-propulsion: They cannot be used for quick acceleration, but for orbital control. It is because the force is equivalent of a piece of paper. However, if technology improves, it's specific impulse will soon be astronomically huge; high thrust for very minimal fuel usage

[ARS]

What I think about real-life space combat, I personally doubt the combat will take place in interplanetary space, since air combat tactic on earth does not apply in space. I'm personally think that, if somehow 2 colonies on different planets start to wage war against each other, the combat would take place on the orbit of one of the planet, using tactic like these:

-fleet A is heading on a planetary orbit of target planet from the trajectory where the target planet's launch site (or fleet) is still behind the planet

-the target planet reposition the fleet B to intercept fleet A, while fleet A finished establishing orbit

-both fleet now on a stable orbit (ex: equatorial orbit), but each of them heading on different direction (ex: fleet A heading clockwise, fleet B heading counterclockwise)

- eventually, both fleets will get a closest approach between each other where they will unleash everything they had at each other

- if both of the fleet still survives, then the next closest approach will be the next combat engagement. However, a cunning fleet commander may consider to change orbital inclination to attack from unexpected direction, increase their prograde to get range advantage, or perform any orbital maneuver to gain advantage against other fleet. The planet may send a fleet to attack other planet with the crew in cryosleep (dunno if it's viable for long range travel) that will be awakened before the encounter with target planet

That's what I think

[Joseph Kerman]

On 6/11/2017 at 7:38 PM, ARS said:

What I think about real-life space combat, I personally doubt the combat will take place in interplanetary space, since air combat tactic on earth does not apply in space. I'm personally think that, if somehow 2 colonies on different planets start to wage war against each other, the combat would take place on the orbit of one of the planet, using tactic like these:

-fleet A is heading on a planetary orbit of target planet from the trajectory where the target planet's launch site (or fleet) is still behind the planet

-the target planet reposition the fleet B to intercept fleet A, while fleet A finished establishing orbit

-both fleet now on a stable orbit (ex: equatorial orbit), but each of them heading on different direction (ex: fleet A heading clockwise, fleet B heading counterclockwise)

- eventually, both fleets will get a closest approach between each other where they will unleash everything they had at each other

- if both of the fleet still survives, then the next closest approach will be the next combat engagement. However, a cunning fleet commander may consider to change orbital inclination to attack from unexpected direction, increase their prograde to get range advantage, or perform any orbital maneuver to gain advantage against other fleet. The planet may send a fleet to attack other planet with the crew in cryosleep (dunno if it's viable for long range travel) that will be awakened before the encounter with target planet

That's what I think

No one will try that. The relative speed of the craft will be Ov squared.

Edited June 12, 2017 by Joseph Kerman

[kerbiloid]

On 04.06.2017 at 5:23 PM, wumpus said:

There were also thousands of ICBMs deployed, but none so far has been launched armed (and presumably never tested with actual warheads).

Cruise ones were tested with nukes. R-12 (SS-4) and R-14 (SS-5).

[captain meh]

What advantages does a craft (drone or manned) which fires or releases weaponry have over just a bunch of missiles? I think missiles would be launched from planets or from space stations rather than being launched from a space fighter or warship.

[kerbiloid]

Instead of missiles it has an advantage that a SILO can be shot in several minutes, while an orbital platform needs up to an hour to be hit and can evade a little.
So, it can survive enough long to launch missiles when SILOs are already gone.
 

Instead of unmanned platform:

It can operate without lightspeed delay and even without communication.
Captain can receive an order like "Take the package #4 from the safe, unpack and follow instructions. Secret key — 12345."
(You can watch this in "Dr. Strangelove" movie).
Then the crewed ship operates on its own, in real time.
While a droneship needs either a super-AI or communication to receive commands with seconds-up-to-minutes delay. Unless it's just a launcher.

Any nuke has a warranty period, and this period is significantly shorter than Mir or ISS lifespan.
So, you have to utilize the orbital nukes and to deliver them back to the Earth.
Somebody must do this. Either the battleship crew, or a utility ship crew.

If you want to have many orbital nukes, you have to launch tens or hundreds of rockets with them.
Several of them surely will crash, spreading fission materials along the launch path.
So, if you don't want to watch blue sunsets, you have to deliver unarmed charges separatedly, in safe way, as alive persons, in protected capsules with LES or so, and then mount them aboard or kind of.

Missiles and nuke need maintenance or at least watching. 
So, if you don't want to send a shuttle to every uncrewed satellite with ten warheads aboard and try to repair it in spacesuits, it's easier to keep them docked to a crewed station. 
Even if you undock them for battle.

Somebody can try to steal or disable an uncrewed nukesat.
You can easily burst a spysat together with the intruder, but will you burst or spread along the orbit 20 nukes when there can be no intruder, just a false positive?
So, one feels better if somebody guards his barn with nukes _{with dogs and shotgun}.

This makes a crewed orbital battleship not so silly thing. 
It's a combo of:
- autonomous command center able to target and launch missiles without communication with HQ, just on its own.
- orbital workshop for maintenance of nuke charges.
- guarded trailer park for the docked nukesats

So, I'm sure that unless we speak about far future, real-life orbital battleships can be of two kinds:
1. Light orbital spotter like MOL/Almaz, without its own weapons, just spotting targets for ICBM, aviation, orbital rocket battleships.
(Though, as both MOL/Almaz had mini-capsules to deliver films, they probably could hit, say an unprotected terrorist camp in desert or jungles with a solitary 100kt inaccurate strike.
But of course such strike has no purpose for a real warfare between nuclear states, it would just cause a massive counter-strike).

2. Mir-style drone carrier like on pictures here

Spoiler

Maybe with a Skylab-sized body instead of several modules.

Edited July 4, 2017 by kerbiloid

[DDE]

2 hours ago, captain meh said:

What advantages does a craft (drone or manned) which fires or releases weaponry have over just a bunch of missiles? I think missiles would be launched from planets or from space stations rather than being launched from a space fighter or warship.

Immediately? None. It only has an advantage if its propulsive system has a noticeably higher Isp than the expendable payload. Think a NERVA warship carrying hypergolic missiles.

On ‎11‎.‎06‎.‎2017 at 5:48 AM, Joseph Kerman said:

What I think the first space fighters will be like?

Scramjets: They will be large blended wing or lifting body fighters with an inline turboscramjet and final insertion thrusters for orbital insertion. They will have to carry some batteries as well, for life support and the weaponry. We would most probably be using a laser, at least 30 kW. Re-entry will involve using retro-thrusters to push perigee below 70,000 m for aerobraking.

Ion-propulsion: They cannot be used for quick acceleration, but for orbital control. It is because the force is equivalent of a piece of paper. However, if technology improves, it's specific impulse will soon be astronomically huge; high thrust for very minimal fuel usage

Not sure you can power a military useful laser with chemical batteries. Might as well work with a nuclear turbojet/scramjet/thermal rocket/powerplant.

Ion propulsion basically results in something that is static in a tactical timeframe; electric thrusters in general can't achieve thrust useful in combat.

[kerbiloid]

Not sure if he can place enough big mirror on a fighter, even with batteries.

[Joseph Kerman]

42 minutes ago, DDE said:

Not sure you can power a military useful laser with chemical batteries. Might as well work with a nuclear turbojet/scramjet/thermal rocket/powerplant.

The powerplant is not a chemical battery, but a fission battery. The latter has the advantage of lasting longer and producing energy near-indefinitely.

44 minutes ago, DDE said:

Ion propulsion basically results in something that is static in a tactical timeframe; electric thrusters in general can't achieve thrust useful in combat.

Actually, that is partially false. Ion propulsion can be used on very-light fighters that carry a few HVAR's at a target; the said platform is not static.

[tater]

There are no "fighters," that's not a thing in space. Not ever. Nothing goes fast enough to travel far in short time periods, so all craft need long duration life support, making them bigger. Thanks to the rocket equation, they all carry large amounts of propellants. Robotic "fighters" have another name---missiles.

 

[tater]

It's important to remember that the concept of a fighter bomber terrestrially is that it:

1. Is a very small target.

2. Travels vastly in excess of ground target speeds, including shipping.

3. is highly maneuverable compared to ground targets and shipping.

4. Carries weaponry capable of taking out much larger targets than itself.

 

In space warfare 1 and 2 are mutually exclusive. In addition, 2 is simply not true in space, more propellant means higher velocity, so bigger craft are faster. 2 and 3 are mutually exclusive as well, the faster you are going, the more predictable your future position is.

4? This tends to imply a missile/warhead (both for real fighters, and fantasy space fighters). The trouble with missiles is that the defensive fire control solution is trivial, since the missile needs to intercept the target, and hence ends up on a nearly constant bearing. Any directed energy weapon can easily kill the sensors necessarily pointed at the target. Larger craft can carry better DE weapons, because physics.

[YNM]

As apparently I haven't posted my opinion here previously :

 

 

 

Space Warfare ?

[DDE]

7 hours ago, Joseph Kerman said:

The powerplant is not a chemical battery, but a fission battery. The latter has the advantage of lasting longer and producing energy near-indefinitely.

Those are rubbish in terms of specific power, and are basically useless when you merely need brief bursts of power - which is the case with laser pumping energy sources.

Quote

Actually, that is partially false. Ion propulsion can be used on very-light fighters that carry a few HVAR's at a target; the said platform is not static.

No, they can't. Due to the massive power needs, ease of detection and inherent limitations to thrust power, they'll never move from the category of "sitting duck".

[DDE]

7 hours ago, tater said:

It's important to remember that the concept of a fighter bomber terrestrially is that it:

1. Is a very small target.

2. Travels vastly in excess of ground target speeds, including shipping.

3. is highly maneuverable compared to ground targets and shipping.

4. Carries weaponry capable of taking out much larger targets than itself.

 

In space warfare 1 and 2 are mutually exclusive. In addition, 2 is simply not true in space, more propellant means higher velocity, so bigger craft are faster. 2 and 3 are mutually exclusive as well, the faster you are going, the more predictable your future position is.

4? This tends to imply a missile/warhead (both for real fighters, and fantasy space fighters). The trouble with missiles is that the defensive fire control solution is trivial, since the missile needs to intercept the target, and hence ends up on a nearly constant bearing. Any directed energy weapon can easily kill the sensors necessarily pointed at the target. Larger craft can carry better DE weapons, because physics.

There have been efforts towards coming up with justifications for them... but they're usually pretty damned contrived. Usually magic ECM, energy shields, nerfage of lasers... and "cultural reasons".

[tater]

Given that this thread is in the science section and not the Lounge, we should eliminate fantasy  

[Joseph Kerman]

11 hours ago, DDE said:

Those are rubbish in terms of specific power, and are basically useless when you merely need brief bursts of power - which is the case with laser pumping energy sources.

Unless you are talking about RTG's, no, they are not rubbish.

11 hours ago, DDE said:

No, they can't. Due to the massive power needs, ease of detection and inherent limitations to thrust power, they'll never move from the category of "sitting duck".

Talk to the hand: https://en.wikipedia.org/wiki/Dawn_(spacecraft)

[tater]

25 minutes ago, Joseph Kerman said:

Unless you are talking about RTG's, no, they are not rubbish.

Talk to the hand: https://en.wikipedia.org/wiki/Dawn_(spacecraft)

Dawn produces ~10 kW at 1AU. Meaninglessly small for anything like directed energy weapons when you need to deliver megaJoules to the target. 

Maneuver over years? Not important for a weapon system. It needs to be able to move at least a spacecraft diameter in a random direction during the time of flight of a weapon aimed at it (say a laser).

[Bill Phil]

11 hours ago, DDE said:

No, they can't. Due to the massive power needs, ease of detection and inherent limitations to thrust power, they'll never move from the category of "sitting duck".

This explains my thoughts on space combat in general. Everything is a sitting duck, and its location and velocity, orbit and such are all known values.

14 hours ago, tater said:

There are no "fighters," that's not a thing in space. Not ever. Nothing goes fast enough to travel far in short time periods, so all craft need long duration life support, making them bigger. Thanks to the rocket equation, they all carry large amounts of propellants. Robotic "fighters" have another name---missiles.

 

I think it'd be more accurate to say there are no craft which have a different travel medium, save rovers and spaceplanes. 

But when it comes to fighters, they won't be a thing. But torpedo boats? Maybe. Operating out of a space station armed with a small number of warhead pumped weaponry, Casaba howitzers or Excalibur warheads. They can be small cheap space craft, and would likely be unmanned unless some sci fi Minovsky particles somehow come into play. Probably less expensive than their warheads...

[kerbiloid]

2 hours ago, Bill Phil said:

Everything is a sitting duck, and its location and velocity, orbit and such are all known values.

AGM-135.

Speed 24000 km/h = 6.7 km/s, target altitude = 555 km, i.e. flight time ~90 s. Kills the satellite with direct collision.

Orbital object size ~10 m.

Acceleration to evade in random direction =2*L/t² = 2 * 10 / 90² = 0.002 m/s².

Mass, say, ~1000 t. 

Required thrust ~ 0.002 * 1000 000 = 2 kN.

Every self-propelled module of Mir/ISS has two-four main engines of 4 kN thrust.

ISS mass = 500 t.

Acceleration = 2 * 4000 / 500000 = 0.016 m/s².

Time to evade = (2 * 10 / 0.016)^1/2 = 36 s.

Check. L = wt²/2 = (2*4000/500000) * 36² / 2 = 10.4 m.

So, if ISS gets warned about incoming AGM-135 in less a minute after its launch, it has enough thrust to move in random direction to evade.
That's if they target at a specific module.

If they target at ISS in whole, the rocket would just pierce a solar panel or radiator. Pure probability.

A sat can have solid a booster.

And you have to have fighters with ASATs along the whole orbit, while ISS can launch something at any point.

So, technically orbital weapons are possible. Economically - "ok, but not right now".

2 hours ago, Bill Phil said:

torpedo boats

Have no benefits above torpedoes launched right from Huge Battle Station.
Only if they are unmanned self-propelled modules like on this Mir picture. Just to move away from the station getting killed and launch torpedoes.

 

[Bill Phil]

2 minutes ago, kerbiloid said:

AGM-135.

Speed 24000 km/h = 6.7 km/s, target altitude = 555 km, i.e. flight time ~90 s. Kills the satellite with direct collision.

Orbital object size ~10 m.

Acceleration to evade in random direction =2*L/t² = 2 * 10 / 90² = 0.002 m/s².

Mass, say, ~1000 t. 

Required thrust ~ 0.002 * 1000 000 = 2 kN.

Every self-propelled module of Mir/ISS has two-four main engines of 4 kN thrust.

ISS mass = 500 t.

Acceleration = 2 * 4000 / 500000 = 0.016 m/s².

Time to evade = (2 * 10 / 0.016)^1/2 = 36 s.

Check. L = wt²/2 = (2*4000/500000) * 36² / 2 = 10.4 m.

So, if ISS gets warned about incoming AGM-135 in less a minute after its launch, it has enough thrust to move in random direction to evade.
That's if they target at a specific module.

If they target at ISS in whole, the rocket would just pierce a solar panel or radiator. Pure probability.

A sat can have solid a booster.

And you have to have fighters with ASATs along the whole orbit, while ISS can launch something at any point.

So, technically orbital weapons are possible. Economically - "ok, but not right now".

Have no benefits above torpedoes launched right from Huge Battle Station.
Only if they are unmanned self-propelled modules like on this Mir picture. Just to move away from the station getting killed and launch torpedoes.

 

Yeah, sure.

Simple solution. Laser. Excalibur warhead. No more space station.

Yes, I thought of that. Why not just launch torpedoes from the station itself? Well, having other vectors and positions to deploy weapons would be valuable. More threats = more things to shoot at. Of course, you could have dummy torpedo boats, too.

And of course, the torpedo boats could deploy in a sort of spherical defense pattern. If anything gets too close, it shoots off a warhead. If too many things get too close, a bunch of them shoot warheads. The main advantage over a station here is that the warheads would arrive faster and would increase the defense range.

Of course, we could just deliver huge slugs to the station from afar....

The torpedo boats could potentially deploy to any location in the Earth-Moon system, and potentially provide a screen that would prevent ships from entering. Then it'd be more like mines, but they'd carry multiple warheads...

In any case, torpedo boats are more justifiable than fighters.

[kerbiloid]

20 minutes ago, Bill Phil said:

Simple

Since 1950s.
But the only implemented orbital one weighted about 100 t and required an Energy to launch.

Another, much smaller, airplane-based thing has unknown range, requires a cargo plane and, afaik, gets decommissioned right after the tests.

Also: 
- you need many lasers, as the orbit is long.
- laser (that one, from airplane) needs several seconds to heat the target, which also can evade or throw clouds of smoke.
- against every laser your opponent can have anti-laser, chances get 50:50
- you can't shoot first (this will just cause a mass counter-attack), while when the station had launched her rockets, you no more need to hit the empty station. First step is hers.

20 minutes ago, Bill Phil said:

The torpedo boats could potentially deploy to any location in the Earth-Moon system, and potentially provide a screen that would prevent ships from entering. Then it'd be more like mines, but they'd carry multiple warheads...

And now you have to launch all these torpedo boats to the orbit, maintain them, utilize outdated nukes.
And from time to time catch several warheads lost in space before they fall and spread Pu in air or fall into evil hands.
Then you realize that all boats will stay docked to stations until apocalypse, and when apocalypse goes, you still must return the boat crews to home.
So, 99.999% of time the crews will eat, breathe and morally decay to work several minutes instead of a simple robot.

Fighter, though, yes, are pure fiction.

Edited July 5, 2017 by kerbiloid

[DDE]

4 hours ago, kerbiloid said:

AGM-135.

Speed 24000 km/h = 6.7 km/s, target altitude = 555 km, i.e. flight time ~90 s. Kills the satellite with direct collision.

Orbital object size ~10 m

That's only a minor problem caused by departure from liquid-fuelled missiles to solid-fuel ones. Any dodge can be countered, you just need to learn to handle acid and hydrazine. And then you have SDI-era USAF Project TIMBERWIND with pebble-bed nuclear motors.

7 hours ago, Joseph Kerman said:

Unless you are talking about RTG's, no, they are not rubbish.

Nuclear batteries are glorified RTGs with a different power conversion method. They have a stable, but fairly low power output. They are not "batteries", and the x-ray stimulated isomer decay thing seems to be a hoax.

[kerbiloid]

I just mentioned a practical test where a sat was intercepted irl, and without nuclear propulsion which makes the thing more fantastic than realistic.
For example, how many nuclear timberwind would be crashed while debugging?

Edited July 5, 2017 by kerbiloid

[magnemoe]

7 hours ago, Bill Phil said:

This explains my thoughts on space combat in general. Everything is a sitting duck, and its location and velocity, orbit and such are all known values.

I think it'd be more accurate to say there are no craft which have a different travel medium, save rovers and spaceplanes. 

But when it comes to fighters, they won't be a thing. But torpedo boats? Maybe. Operating out of a space station armed with a small number of warhead pumped weaponry, Casaba howitzers or Excalibur warheads. They can be small cheap space craft, and would likely be unmanned unless some sci fi Minovsky particles somehow come into play. Probably less expensive than their warheads...

An torpedo boat would make sense, an fighter is designed for an short duration mission 6 hour or shorter, life support and crew facilities as in an seat is designed for this. 
In space you would have longer duration missions but you would not want to stay an month in an Gemini capsule 

An torpedo boat would have far longer endurance, it would have crew quarters and facilities, think a space shuttle.  
it would have an more efficient drive than an missile, another use is fire control closer to target, this would be an practical minimum size for manned warships.