For Questions That Don't Merit Their Own Thread

[DDE]

5 hours ago, ARS said:

On MAZ-based transporter-erector launcher vehicles, what's the purpose of the that secondary cabin separated from the driver's cabin? Does it serve any functional purpose or just for passengers? What about it's civillian version?

Fire control, comms, engineering. Note how the Smerch has them in a central location instead because it's long enough relative to the rocket tubes. You also often see it altered quite a bit between vehicle subvariants or removed, even while the driver's cabin stays put.

Plenty of similar tasks for all the civilian versions.

[K^2]

On 3/25/2020 at 10:42 PM, HaplessBystander said:

What I'm taking away from this is I've failed to account for the relative velocities between the ship and the propulsion unit and the faster the propulsion unit is ejected the more kinetic energy it will have to impart to the ship to produce the same delta-v. Will the aforementioned additive approach still work if the equation is altered to account for this? If so, how do I alter the equation to make it work?

Same way you do in derivation of rocket formula. Instead of considering all of the energy at once, you compute delta-V for each individual detonation. You can then work in rest-frame of the ship for each detonation, since incremental delta-V changes are going to be the same. Then you add all of these together. Since early detonation work against the full mass of the ship, and later detonations push a ship that's a few nukes lighter, you will end up with something resembling a logarithm in the rocket formula.

[tater]

For those of use who enjoy espresso, lol:

https://www.sciencedirect.com/science/article/pii/S2590238519304102

 

[ARS]

Could you fly an aircraft with twin-tail twin-engine design (such as F-15 or Su-35) using only one tail (with the other one ripped off) and compensating by using rolling+pitching in place of yawing while disabling the remaining vertical stabilizer?

[magnemoe]

1 hour ago, ARS said:

Could you fly an aircraft with twin-tail twin-engine design (such as F-15 or Su-35) using only one tail (with the other one ripped off) and compensating by using rolling+pitching in place of yawing while disabling the remaining vertical stabilizer?

As I understand someone landed an F15 with just one wing so missing an tail is not an big deal. F-15 and Su-35 tend to have an twr well above 1 on light load, they have oversize control surfaces for agility in dogfights. 

[K^2]

F-15 also has a fly-by-wire system specifically designed to adaptively deal with combat damage. I would imagine so would Su-35, since both aircraft are inherently unstable and both are built to have snot beaten out of them and keep flying. This is similar to how you can usually land a conventional airplane with any one control surface stuck near neutral position by utilizing combined input from all the others. (Yes, you can roll your plane with rudder, just not very well.) The difference is that a modern(ish) fighter is built to be aerodynamically unstable for improved maneuverability and efficiency, so it has a computer keeping controls coordinated. You don't control anything with flight stick directly - just telling flight computer what you'd like the airplane to do. If you lose a control surface, flight computer usually adapts input to all others to try to give you as much of authority back as possible. According to the pilot from that F-15 incident, had he known how bad the damage was, he would have bailed. But due to the fly-by-wire simply rerouting control to all remaining control surfaces, he thought the wing is merely damaged and so went ahead with the landing.

[SuperFastJellyfish]

1 hour ago, magnemoe said:

As I understand someone landed an F15 with just one wing so missing an tail is not an big deal. F-15 and Su-35 tend to have an twr well above 1 on light load, they have oversize control surfaces for agility in dogfights. 

 

[DDE]

15 hours ago, ARS said:

Could you fly an aircraft with twin-tail twin-engine design (such as F-15 or Su-35) using only one tail (with the other one ripped off) and compensating by using rolling+pitching in place of yawing while disabling the remaining vertical stabilizer?

I remember coming across an article about a NASA F-15 with a tweaked fly-by-wire capable of seamlessly compensating a malfunction of any of the control surfaces. So it's fairly likely.

[ARS]

14 minutes ago, DDE said:

I remember coming across an article about a NASA F-15 with a tweaked fly-by-wire capable of seamlessly compensating a malfunction of any of the control surfaces. So it's fairly likely.

Probably the F-15 STOL/MTD project, which eventually produces the IFCS system

[Spacescifi]

 

How to chase and rendezvous with another spaceship in orbit?

 

The most I learned first hand was playing a clone of the original 2-D Space War.

I used the star in the middle to orbit, and I found orbiting head on toward my target was one of the fastest ways to intercept.

In real life we do not have infinite fuel, so I was thinking... how does one chase down a spaceship in orbit that does not want to be caught up with?

Provided both ship's have similar specifications?

My guess? Try to fly as close to the planet as possible and then speed up to fly over and avoid diving into atmosphere. That will at least give you a gravity assisted boost to orbit faster.

Go too deep and you eat atmosphere though, while also killing your speed.

I guess this will result in a tie if both ships have the same specs, since they can evade each other forever until they run out of fuel. 

Playing dirty is another way by littering orbit with debris, but there is a fine line between destroying and disabling a spaceship.

 

Edited March 30, 2020 by Spacescifi

[kerbiloid]

There is a special software to do this.

Spoiler

https://www.kerbalspaceprogram.com/

 

[K^2]

4 hours ago, Spacescifi said:

In real life we do not have infinite fuel, so I was thinking... how does one chase down a spaceship in orbit that does not want to be caught up with?

If one ship is strictly pursuing, the other is strictly evading, the evading ship has advantage and in general will always be able force pursuer to run out of fuel first. Suppose, pursuing ship already invested some fuel to get an intercept. Now the evading ship can perform a correction to avoid intercept. Pursuing ship has option to match or abort and go for a different intercept later. In the former case, it's the evading ship that chooses the burn and therefore, can always chose one that's going to be fuel-efficient for evading ship. If pursuer aborts, they have to get new intercept, which will require even more fuel down the line. Either way, evading ship can keep evading until pursuer runs out of fuel.

[Spacescifi]

5 hours ago, K^2 said:

If one ship is strictly pursuing, the other is strictly evading, the evading ship has advantage and in general will always be able force pursuer to run out of fuel first. Suppose, pursuing ship already invested some fuel to get an intercept. Now the evading ship can perform a correction to avoid intercept. Pursuing ship has option to match or abort and go for a different intercept later. In the former case, it's the evading ship that chooses the burn and therefore, can always chose one that's going to be fuel-efficient for evading ship. If pursuer aborts, they have to get new intercept, which will require even more fuel down the line. Either way, evading ship can keep evading until pursuer runs out of fuel.

 

I see... so again reality proves those unwanted spaceship scuffles in orbit as pure fiction.

If I don't want to be caught up with or be fighting with another spaceship in orbit and it has similar specs to mine... I won't.

It is not a forced sitiation after all.

Now launching suborbital craft or missiles to hit an orbiting craft actually could force the orbiter to run out of fuel, but that is another discussion.

Edited March 30, 2020 by Spacescifi

[DDE]

In railguns, what is the greater bottleneck in terms of rate of fire: the capacitors or the gun?

[p1t1o]

53 minutes ago, DDE said:

In railguns, what is the greater bottleneck in terms of rate of fire: the capacitors or the gun?

Erosion of the rails is a big deal I think.

https://www.researchgate.net/publication/3107709_Rail_and_insulator_erosion_in_rail_guns

https://www.sciencedirect.com/science/article/abs/pii/S0921509311006009

[DDE]

On 4/3/2020 at 1:51 PM, p1t1o said:

Erosion of the rails is a big deal I think.

https://www.researchgate.net/publication/3107709_Rail_and_insulator_erosion_in_rail_guns

https://www.sciencedirect.com/science/article/abs/pii/S0921509311006009

Disregarding erosion, what I'm actually thinking is whether, with the assumption that we have two guns...

...is it more efficient to have two capacitor banks, or have one that alternatively fires into two turrets?

[Shpaget]

That would depend on available power, maximum charge rate of capacitor bank, projectile loading rate and, of course, doctrine.

Perhaps the system can fire continuously at max rate on both guns, using only one capacitor bank, but two are installed for redundancy. Efficiency is a hazy metric when it comes to military.

[magnemoe]

2 hours ago, DDE said:

Disregarding erosion, what I'm actually thinking is whether, with the assumption that we have two guns...

...is it more efficient to have two capacitor banks, or have one that alternatively fires into two turrets?

Purpose of having two guns is that they can focus on different targets or rater be commanded independently, say you do artillery support for two units. I assume missiles would be an 3rd command. 
If it was just rate of fire having two guns in one turret would be much lighter. 
For traditional guns the main issue is heating, so you can fire bursts but rate of fire over time is limited by heat. 

[DDE]

5 minutes ago, magnemoe said:

Purpose of having two guns is that they can focus on different targets or rater be commanded independently, say you do artillery support for two units. I assume missiles would be an 3rd command. 
If it was just rate of fire having two guns in one turret would be much lighter. 

That's not usually the case. Many, many generations of ships before had multiple turrets but a single fire director, sometimes for the entire ship. The multi-gun turrets are always a compromise between saving space, and risking a larger portion of the firepower lost due to a malfunction.

 

[magnemoe]

2 minutes ago, DDE said:

That's not usually the case. Many, many generations of ships before had multiple turrets but a single fire director, sometimes for the entire ship. The multi-gun turrets are always a compromise between saving space, and risking a larger portion of the firepower lost due to a malfunction.

 

Good point, also you have to develop the multi gun turret. Thinking of US WW 2 destroyers with up to 5 single gun 5" turrets. And they had dual gun 5" turrets who was used as secondary guns on battleships, but they might not fit well on an destroyer even if you reduced armor on them. 
But on an modern ship shooting smart shells you would want to control them independently, doing artillery support you are not using the fire control system much anyway so it might be that if you fight air targets or other ships you can only engage one target. 
Some serious missiles on that ship

[Tonka Crash]

On 3/28/2020 at 9:03 PM, K^2 said:

F-15 also has a fly-by-wire system specifically designed to adaptively deal with combat damage. I would imagine so would Su-35, since both aircraft are inherently unstable and both are built to have snot beaten out of them and keep flying. This is similar to how you can usually land a conventional airplane with any one control surface stuck near neutral position by utilizing combined input from all the others. (Yes, you can roll your plane with rudder, just not very well.) The difference is that a modern(ish) fighter is built to be aerodynamically unstable for improved maneuverability and efficiency, so it has a computer keeping controls coordinated. You don't control anything with flight stick directly - just telling flight computer what you'd like the airplane to do. If you lose a control surface, flight computer usually adapts input to all others to try to give you as much of authority back as possible. According to the pilot from that F-15 incident, had he known how bad the damage was, he would have bailed. But due to the fly-by-wire simply rerouting control to all remaining control surfaces, he thought the wing is merely damaged and so went ahead with the landing.

F-15 isn't fly-by-wire. F-16, F/A-18, F-22, F-35 yes, F-15 not yet. The proposed F-15EX will be the first to ditch the conventional flight control system. One of the arguments for the change on the F-15EX is that it will be more reliable and simpler to maintain by removing the hydraulics and mechanical linkages. Even the original F/A-18s had a mechanical backup for the FBW that was deleted in the Super Hornet.

The Israeli F-15 that landed missing a wing was able to do so primarily because the flight control system had adequate control authority to maintain control in 1g flight. It was returned to service and was still flying as recently as 5 years ago.

[kerbiloid]

(about the ship multiguns)

Isn't fork the main (if not the only) purpose of  independent vertical adjusting of the barrels

Spoiler

When you have three independent barrels you can quickly throw three shells at different angles, and hope that one of them hits the target.

[DDE]

13 hours ago, magnemoe said:

Good point, also you have to develop the multi gun turret. Thinking of US WW 2 destroyers with up to 5 single gun 5" turrets. And they had dual gun 5" turrets who was used as secondary guns on battleships, but they might not fit well on an destroyer even if you reduced armor on them. 

The Fletcher-class variant Allen M. Sumner-class  did upgrade to three twin turrets, but those did seem alarmingly wide compared to the hull.

Which is probably the reason for the pairs of AK-100 turrets on the relatively narrow-hulled mid-Cold War Soviet ships - although their later users, namely the Udaloy (seen here) and the Kirov, were both upgraded with the twin 130 mm.

[wumpus]

9 hours ago, kerbiloid said:

(about the ship multiguns)

Isn't fork the main (if not the only) purpose of  independent vertical adjusting of the barrels

  Hide contents

When you have three independent barrels you can quickly throw three shells at different angles, and hope that one of them hits the target.

For the "too short", "too long", "just right method" wouldn't two barrels (to throw the "too short" and "too long" shells at once) be better?  Once they land you can calibrate your "just right" shot (or fire two more for successive approximation).  Of course this assumes that time to load >> time of shell in flight.

[kerbiloid]

44 minutes ago, wumpus said:

For the "too short", "too long", "just right method" wouldn't two barrels (to throw the "too short" and "too long" shells at once) be better?  Once they land you can calibrate your "just right" shot (or fire two more for successive approximation).  Of course this assumes that time to load >> time of shell in flight.

There were two as well.

Spoiler

But why have two when the turret is enough wide to have three.

Also you don't have to fire all three at once. Fire two, then fire the third without reloading.

Edited April 5, 2020 by kerbiloid