• 0
Helmetman

Has anybody once build a rail gun or cannon [stock]

Question

So you may suggest mods for this. But concerning the core idea I would want it to be reviewed from a possible stock orientation.

Food for thought: 

 

So I want to build something similar on the Mun but then with rocket engines. Either using a real rail gun replica or a cannon using kinetic force of engine exhaust. It's not to be mega efficient at something persé.
It's probably not something even remotely functional for a maintained reusable method during sandbox/career gameplay, rather a test to see if it can get done.

I'm not necessarily aiming for getting a craft to suborbital or even orbital velocities using said technique. But I would want to know how far I could get.
What I want to recreate in KSP is a 1-2km long rail on a small crater slope with a drill and refinery at one end that has a default rocket propelled rail carriage (locomotive) I would want to put cargo on the rails and have it docked and be propelled by said locomotive. Then using a hotkey to release the forward cargo section and have the propelled carriage it's engines cut and put on brakes so it stops at the end of the rail. Then having your cargo shoot of at god knows how many meter per second. I could then use the carriage (locomotive) to roll back to it's starting position where it can be refueled by the ISRU since it has it's external tanks once released and put on rails.

All I hope it's possible while any game colliders do not brake apart any parts during the rail guided phase. I would probably have to fine tune a lot to get this done properly if at all possible.

The previous point is also why I made this thread. Has something been done before? Not like in the youtube videos sample but on high speed (whatever that is)
What issues could I run into? 

Another idea was to simply build a cannon. Basically a wing build tube with landing gear sticking in at the inside to funnel the parts out of the barrel. But I'm hardly sure you can get decent speed besides launching very small objects into space.

Is there a way to use as much of the kinetic energy exhaust to maximize the distance of my projectile? Will a certain stock part be more susceptible to absorbing the kinetic energy and propel further then other parts for example when placed at the bottom near the exhaust flame? Questions like these get me going. Before getting at it I was curious whether such a attempt has been done before with high projectile speeds in mind and whether I should continue or give up now. 

Stupid idea?  

Share this post


Link to post
Share on other sites

13 answers to this question

Recommended Posts

  • 0

Yeah, exactly! That is brilliant, although I rather build it myself. That one seems quite strong so I'm gonna try test to shoot sizeable cargo on the Mun with this to see what's necessary.

I'm definitely going to get work done on a rail gun aswell just to see what I can get done. If someone got some tips or warnings for a high speed rail gun then great. I've only found EC driven slow moving locomotives. That is what I've found so far...

Share this post


Link to post
Share on other sites
  • 0

@Spricigo That craft will lose all it's lending legs in the process. I didn't mention, but I would want the mechanism to be re-usable rather then expendable.

 

@bewing Looking into it. Thanks:cool:

Share this post


Link to post
Share on other sites
  • 0
18 minutes ago, Helmetman said:

Yeah, exactly! That is brilliant, although I rather build it myself.

Then you are going to have to figure out how they work. :wink: I don't know, myself.

Share this post


Link to post
Share on other sites
  • 0

The Legittilery mini, what a beast. Answers my question pretty well. 

Gonna try to be quite creative to see what can be done with sizeable cargo. have to find out what sizeable can be hehe.

Still wondering of any decent speed can be gained with railguns. Is it a dead end due to collision effects?

Just now, bewing said:

Then you are going to have to figure out how they work. :wink: I don't know, myself.

Yeah, that I'm gonna try...

Edited by Helmetman

Share this post


Link to post
Share on other sites
  • 0

Not sure if this is related, but I have a KSP design for long range gun in stock (my design fires kerbals though). The design is based from Germany city bombardment gun during WW2. Basically, my design is lining up mainsail engines like this:

\ \ \ \ \ \ \ \

Projectile >>>

/ / / / / / / /

The / and \ is mainsails, which propels the projectile sequentially, the longer the assembly, the higher the projectile speed. There's no limit to the engines that you can use (well, too many engines might cause game performance issue though)

Share this post


Link to post
Share on other sites
  • 0

Very nice ARS. I'm sold to the mechanical landing gear method. The KerbalX samples that use landing gear for propulsion will create a higher kinetic energy giving more energy then what the max exhaust velocity of rockets could give you.
Basically the speed is limited by the ISP which is even lower on ground level at Kerbin. The mechanical landing gear method can get things to over 1000 m/s. So unless I tweak the TWR of a Dawn Ion engine I will not profit from a exhaust mechanic.

This would do great on the Moon though for shooting actual cargo. However I did thought of a similar Idea you propose but I don't yet found a way to properly funnel it. Place the engines to close to each other and it damages while it leaves the barrel. To far from one another and it isn't properly guided.
It's a lot of fiddling to do this correctly. But I'll try.

                                                       

 

 

Edited by Helmetman

Share this post


Link to post
Share on other sites
  • 0
On 1-10-2017 at 5:43 PM, Helmetman said:

Very nice ARS. I'm sold to the mechanical landing gear method. The KerbalX samples that use landing gear for propulsion will create a higher kinetic energy giving more energy then what the max exhaust velocity of rockets could give you.
Basically the speed is limited by the ISP which is even lower on ground level at Kerbin. The mechanical landing gear method can get things to over 1000 m/s. So unless I tweak the TWR of a Dawn Ion engine I will not profit from a exhaust mechanic.

This would do great on the Moon though for shooting actual cargo. However I did thought of a similar Idea you propose but I don't yet found a way to properly funnel it. Place the engines to close to each other and it damages while it leaves the barrel. To far from one another and it isn't properly guided.
It's a lot of fiddling to do this correctly. But I'll try.

                                                       

 

 

Unfortunately ... that isn't correct. The exhaust vector is meant as a function of gameplay only, it's a constant force based on a simple calculation. ISP has got nothing to do with it.

The maximum speed you can reach when accelerating using a rocket engine is based on the mass of the projectile, the force from the exhaust vector and the force drop-off value with distance; and the time the projectile remains within range of the exhaust vector.

Take a look at ModuleEngines, all the entries for ExhaustDamage. I played with some of the values and made a powerful proton cannon with a 3 km range out of the ion engine.

https://kerbalspaceprogram.com/api/class_module_engines.html

Share this post


Link to post
Share on other sites
  • 0

@Azimech 

Do you mean that it's a different 'simpler' calculation for the exhaust vector in KSP or in real life also? I don't know what you mean by a simple equation in that regard.

Sorry for confusing with my mistake mentioning the relation to ISP
But my real worry is the exhaust velocity. Which has one in KSP? Or is this not part of the simpler equations?

How can your projectile travel faster then the exhaust velocities emitted by your engines? Whatever speed that is. 

Thanks for explaining the other factors I should consider.

And thanks for sharing the moduleengines entries. Not sure I wanna go there but cool to hear what you did using the exhaustdamage entries. 

 

 

 

Share this post


Link to post
Share on other sites
  • 0
6 hours ago, Helmetman said:

@Azimech 

Do you mean that it's a different 'simpler' calculation for the exhaust vector in KSP or in real life also? I don't know what you mean by a simple equation in that regard.

Sorry for confusing with my mistake mentioning the relation to ISP
But my real worry is the exhaust velocity. Which has one in KSP? Or is this not part of the simpler equations?

How can your projectile travel faster then the exhaust velocities emitted by your engines? Whatever speed that is. 

Thanks for explaining the other factors I should consider.

And thanks for sharing the moduleengines entries. Not sure I wanna go there but cool to hear what you did using the exhaustdamage entries. 

 

 

 

Really,  try to think much simpler. There are no particles being ejected and therefore the whole concept exhaust velocity does not exist. It's just a force with a point of origin and a vector. ISP is just numbers they've entered in the configuration file. 

You can do all kinds of wacky things with ModuleEngines and ModuleEnginesFX, like give them negative thrust (starts generating resources) or give them negative heat output (use rockets to kill a fire). It's all there to give the illusion of a real engine. 

If the engine were real the name of the product would've been "Rocket Engine Simulator", running slow and unable to do anything else.

Share this post


Link to post
Share on other sites
  • 0
On 03/10/2017 at 7:44 AM, Helmetman said:

@Azimech 

Do you mean that it's a different 'simpler' calculation for the exhaust vector in KSP or in real life also? I don't know what you mean by a simple equation in that regard.

Sorry for confusing with my mistake mentioning the relation to ISP
But my real worry is the exhaust velocity. Which has one in KSP? Or is this not part of the simpler equations?

How can your projectile travel faster then the exhaust velocities emitted by your engines? Whatever speed that is. 

Thanks for explaining the other factors I should consider.

And thanks for sharing the moduleengines entries. Not sure I wanna go there but cool to hear what you did using the exhaustdamage entries. 

 

 

 

The velocity of the projectile fired is not based on the engine ISP, since engines produces constant force in one direction. ISP is just engine efficiency in the config file, nothing more than that. The main factor in accelerating projectile in KSP using engine exhaust is the weight of projectile itself. Here's an example:

Drop a mk1 fuel tank on top upside down running mammoth engine (most powerful stock engine in KSP). The mk1 fuel tank would be launched upwards at high velocity (more if the tank is drained). Now drop a mk2 fuel tank on the same situation. While it does launch the mk2 fuel tank, the velocity would be lower since mk2 fuel tank is heavier

But then, every engine in KSP only provides constant thrust, so no matter how, the mk1 fuel tank won't be launched with the velocity exceeding the maximum possible velocity when using mammoth engine. That brings us to the multi engine launcher. While the engine used does have the same thrust, multiple engines provides far more power than a single engine can provide (for example of this, see @Danny2462's video about 25 thing you can do with asteroid where he uses mainsail engines as a mass relay to launch asteroid)

Using several engines clustered in one point is very inefficient, so what I did in my design is simply positioning the engine vectors along the barrel of the cannon, which means, the longer the barrel, the more engine that can be put. The engine will accelerate the projectile further as it travels inside the barrel

Edited by ARS

Share this post


Link to post
Share on other sites
  • 0

I have tried building a stock artillery gun. The hardest part in my opinion is guiding the shell/payload through the barrel, since structural tubes and 0.625m shells don't exactly fit snugly together. I tried using fairings but that was just a lag-fest. You could use I-Beams/Structural Panels/Wing Panels to build the barrel. You will need to add another engine (or engines) to act as a recoil.

 

P.S. check this out https://en.wikipedia.org/wiki/V-3_cannon

Share this post


Link to post
Share on other sites
This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Answer this question...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.