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Mammoth

Is there a way to change initial altitude in which I launch my rocket?

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So normally we launch from the launchpad at the base which is at sea level, is there anyway I could launch from different heights, eg. 10km above sea level, 20km above sea level, or 30km above sea level?

I'm thinking of using one of those planes with rockets attached and fly the plane up, but it would be more ideal if there's some setting in the game or mod I can use to change the initial altitude I launch my ship because preferably I want zero net force during the launch. 

I'm doing this to investigate the effect of launch height and delta-v.

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Do you have the Making History DLC? There is an option there to enable additional launch sites, rockets can be launched from “Woomerang” or from the “Dessert Airfield”. Planes can be launched from the Dessert Airfield. According to the wiki, Woomerang is 739 m above sea level, and Dessert Airfield is 824 m above sea level. So while they are higher, it’s not a huge difference.

1 hour ago, Mammoth said:

preferably I want zero net force during the launch

Not going to be much of a launch then ;)

Confused as to what you mean here sorry

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You could use the HyperEdit mod and the ship lander feature setting a height that you like. 

Or if the rocket you want to launch isn't too big then you could just have a big first stage that you launch vertically. When it reaches the height/Ap you want then seperate, wait until you stop rising and then launch your test craft.   

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29 minutes ago, Goody1981 said:

Do you have the Making History DLC? There is an option there to enable additional launch sites, rockets can be launched from “Woomerang” or from the “Dessert Airfield”. Planes can be launched from the Dessert Airfield. According to the wiki, Woomerang is 739 m above sea level, and Dessert Airfield is 824 m above sea level. So while they are higher, it’s not a huge difference.

your could also make a very simple "mission", in which case you can place your launch pad anywhere you want on Kerbin, such as the peak of the mountains west of KSC, which should be around 5km

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I don't know if it still works but you used to be able to edit launch clamps in .craft files to any height you wanted. And I mean any height. 100km? No problem!

I don't know the details but I'm sure a few minutes on Google would bring up the important parts.

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You could use the mod *KSCSwitcher*, which allows you to configure alternative launch sites to have KSC at. It's used by RSS; I don't know any ready-made configs for stock Kerbin so you'll probably have to work out your own.

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This question about how to play the game has been moved to Gameplay Questions. 

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20 hours ago, Goody1981 said:

Not going to be much of a launch then ;)

Confused as to what you mean here sorry

I meant no external forces aside from the thrust from the rocket, so if I were to fly an acceerating plane then launch the rocket from it then it wouldn't be same as launching it from a stationary point right?

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28 minutes ago, Mammoth said:

I meant no external forces aside from the thrust from the rocket, so if I were to fly an acceerating plane then launch the rocket from it then it wouldn't be same as launching it from a stationary point right?

Um.... right.   

So to do that, you need a launch site on a mountaintop.  OR  you could use one of the balloon mods to float your rocket way up before releasing it with no horizontal velocity to start with.

But if you're doing all this, why not just use either HyperEdit or the stock cheat menu feature that does the same thing?

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4 hours ago, Mammoth said:

I meant no external forces aside from the thrust from the rocket, so if I were to fly an acceerating plane then launch the rocket from it then it wouldn't be same as launching it from a stationary point right?

Ah ok, gotcha (sort of) ... 

Another way would be launch your rocket using infinite fuel, wait til just before you reach your desired altitude, cut engine, turn off infinite fuel, coast to a stop hopefully around your desired altitude, then throttle up as you hit max height

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5 hours ago, Geschosskopf said:

Um.... right.   

So to do that, you need a launch site on a mountaintop.  OR  you could use one of the balloon mods to float your rocket way up before releasing it with no horizontal velocity to start with.

But if you're doing all this, why not just use either HyperEdit or the stock cheat menu feature that does the same thing?

Balloon mod seems interesting. As I'm quite new to the game, can you elaborate on the cheat menu or Hyperedit you mentioned?

1 hour ago, Goody1981 said:

Ah ok, gotcha (sort of) ... 

Another way would be launch your rocket using infinite fuel, wait til just before you reach your desired altitude, cut engine, turn off infinite fuel, coast to a stop hopefully around your desired altitude, then throttle up as you hit max height

Thanks for the suggestion but infinite fuel wouldn't work for my case since for the experiment I'm doing I have to control the final and initial mass of the rocket and I'm thinking of doing that through carrying different fuel loads.

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18 minutes ago, Mammoth said:

Balloon mod seems interesting. As I'm quite new to the game, can you elaborate on the cheat menu or Hyperedit you mentioned?

Thanks for the suggestion but infinite fuel wouldn't work for my case since for the experiment I'm doing I have to control the final and initial mass of the rocket and I'm thinking of doing that through carrying different fuel loads.

Infinite fuel is a misnomer. It just means your rocket doesn't burn the fuel in it. When you turn it off you'll still have what you started with.

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4 hours ago, Mammoth said:

Balloon mod seems interesting. As I'm quite new to the game, can you elaborate on the cheat menu or Hyperedit you mentioned?

Forgive my poor manners.  I should have noticed you were new.  Welcome!

I know of 2 balloon mods:  Heisenberg Airships and Hooligan Labs.  The former I'm pretty sure is up to date, the latter I don't know.

The cheat menu is accessed with CTRL-ALT-F12 (or just ALT-F12 for some folks).  It has a section for orbits.  There, you can instantly teleport a ship to any orbit off any planet you want.  I suggest this because your whole situation here suggests you just want to get something into orbit without burning fuel or time, which is what this tool does.  Same as HyperEdit.

4 hours ago, Mammoth said:

Thanks for the suggestion but infinite fuel wouldn't work for my case since for the experiment I'm doing I have to control the final and initial mass of the rocket and I'm thinking of doing that through carrying different fuel loads.

As @5thHorseman says, "Infinite Fuel" actually allows the engines to run without using fuel.  So engines will run with empty tanks, and if you had fuel to start with, that amount doesn't change as long as infinite fuel is turned on.

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Posted (edited)

Perhaps I'm not understanding the question, but if you want to launch your rocket from altitude x, then why not use a first stage to lift it to altitude x and launch from there?

Edited by Zhetaan

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5 hours ago, Zhetaan said:

Perhaps I'm not understanding the question, but if you want to launch your rocket from altitude x, then why not use a first stage to lift it to altitude x and launch from there?

That gets really tedious when you're testing a design.

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Posted (edited)
3 hours ago, Geonovast said:

That gets really tedious when you're testing a design.

Certainly, but I would counter that tedium is a necessary part of the design process.  KSP spares the player from the worst of it (mostly with revert-to-launch and the cool explosion sound effects), but I think that it's inescapable that if you want to play with experimental rockets, then you must expect to do experiments.  Perhaps I am making too many assumptions, but since @Mammoth already indicated a desire to test the effect of launch altitude on delta-V, I am under the impression that @Mammoth is a more nuts-and-bolts type of player who wants to actually see the effect rather than let the calculator provide the answer.

If I am wrong, then that's easy enough to do with Kerbal Engineer:  switch to the atmospheric delta-V readout and there are two sliders, one for altitude and one for speed.

Besides, I don't think it's that onerous.  The problem is to test launches at various altitudes with minimal net forces:  that implies as close to a zero-velocity launch as one can get.  That's easy enough:  launch straight up, kill the engines a few thousand metres short of the intended launch altitude, coast to that altitude, stage and burn when the velocity is zero, and there's the answer.  It's essentially the same as the part test contracts that require one to test a part at high altitude but low velocity.  It's even made repeatable by tweaking the fuel load so that the lifter burns out at the same altitude, and pilot error is at a minimum because straight up is the starting attitude of the rocket in the first place.

Edited by Zhetaan

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You could also get a plane to the peak. If you can build a stratolauncher but bigger for your rocket you could get it to the peak with a use to make it stand upright. It's not for everyone as it may prove difficult but it could be your option. Just make sure you Hyperedit test from that altitude to see what works.

There is also something called a space elevator mod using a 100m elevator you could use. I believe you can make it larger using tweakscale also. This way you can lift the rocket up the top and launch it from there.

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