Jump to content
  • 0

problem with spaceplane urgent


imcute
 Share

Question

my spaceplane is constantly going retrograde if it is above 60m/s

making it impossible to take off

the mass center is in front of the lift center

solved

the mass center should be behind the lift center

Link to comment
Share on other sites

Recommended Posts

  • 0
2 hours ago, imcute said:

phew finnally landed!!!!!!!:joy:

Congratulations! :happy:

It took me a lot of time to be able to do what you have done in the last few days so I'd say you're probably a natural spaceplane pilot and designer. Onward and upward!

1 minute ago, imcute said:

so now i have 2100dv,im stranded in duna orbit,how can i get to jool?

Using this online tool it looks like you'll need around 1350 to get to the system so you'll probably need to use some gravitational assists off the moons to get to Laythe (the only other place in the stock Kerbin system where you can use airbreathing mode) and refuel.
mBoOd9R.png

Link to comment
Share on other sites

  • 1
15 minutes ago, imcute said:

aww man fairing keep decoupled by mech jeb

https://image-gallery.imcute-aaaa.repl.co

@James Kerman

@AeroGav

That design looks fairly promising.  Is that a 2.5m fairing though,  attached to a 1.25m fuselage piece with no size adapter ?  Will make drag there.    Also , it looks like you are using two wheesley and one nerv engine ?   I would maybe use 2 rapier and 1 nerv or 2 nerv and 1 whiplash

Link to comment
Share on other sites

  • 1
1 minute ago, imcute said:

no its a 1.875 fairing shielded by 1.25 fairing so no drag i think

no its 2 wheatley and a nerv

That doesn't sound like a viable propulsion system for SSTO.

One NERV is only 60kn,  same as a Terrier.     Close cycle Rapier is 3 times as much power.

If you are not going to use oxidizer engine,  then you will need 2 nervs at least.  And lots of wing,  and low drag.

Wheesely engines have hardly any power above mach 1.  If you really want to cruise around at low altitude and low speed on LAthe without using much fuel,  use a  Panther.    Or just mount a Whiplash for SSTO and put a pair of little Junos on the wing tips for cruising around.

If you are using NERVs to get to orbit try to store as much of your LF as you can inside mk1 strakes,  rather than fuselage tanks.    They will help it fly in the upper atmosphere when the jet engines have stopped. 

Link to comment
Share on other sites

  • 1
1 hour ago, imcute said:

 

yes i used this advice

and the nervs'tail nodes are sealed by nose cones

it loses controll at 10000m and 300m/s

wing strakes?or big s ones?

This is strange.  

Stability should not change with speed or altitude - if the amount of air hitting the plane gets more (because of speed) or less (because of altitude) the strength of the aerodynamic forces will change,  but not their position on the craft.  If the center of lift is behind the center of mass,  the craft will still want to point its nose prograde.

Is it anything to do with fuel burning off ?  "RCS Build Aid" shows a red ball in SPH / VAB so you can see what happen to centre of mass when fuel is used.

Or maybe its just drag from the fairing.  It is a very big one..   like i say the converter and ore tanks don't need to be inside, only the drill.

One other thing.. it's not to do with  Angle of Attack is it ?  I would have thought if this was your problem you would notice on takeoff already.

A plane that looks stable at low angle of attack but suddenly becomes unstable at high pitch is either bending in flight from G forces,  or you've got some aero surfaces angled up a bit at the rear of the air plane.   This gives the back end more lift and makes the blue arrow look like it is in right place in hangar, but when you pitch up,  the rear end stalls first.

I am also confused by your statement "too much wing to take off".    It should be easier to take off with more wing.

Strakes - yes Big S wing strakes weigh the same as other wing parts that make the same lift,  and have the same drag.   But they also store fuel,  which makes them over powered.

 

 

 

Link to comment
Share on other sites

  • 1
7 hours ago, imcute said:

no its always 10 to 20 degrees

Just,  remember kids,    "Angle of Attack" and "Pitch" are not the same thing.

Angle of attack is the difference between where the nose is pointing, and where the plane is actually going (prograde marker in surface mode).

With a powerful engine like the Whiplash,  at times you will have a pitch of 10 - 20 degrees because of the steep climb rate.

But you never want your Angle of Attack to get much more than 5 degrees.

Above 5 degrees,  the lift to drag ratio gets worse, and you want to be trading at the best rate possible.

To fly well (not melt) in the upper atmosphere,  whilst keeping angle of attack at no more than 5 degrees, it is nice to have quite a lot of wing.

But the Whiplash engine thrust falls away very quick above 17km.     So you might be using much less than 5 degrees when flying on jet engine.   This is OK,  because the most important thing is to get as much speed out of the jet engine as possible. 

Once you are using NERVAs,   their thrust doesn't decrease with altitude,  but the ISP is much less than the jet's.   So the only thing that matters is to have the most efficient lift : drag ratio you can get. 

el2r050.jpg

Link to comment
Share on other sites

  • 1
16 hours ago, imcute said:

fixed

fixed

photo gallerry:https://image-gallery.imcute-aaaa.repl.co

okay this time the plane works more easilly and lifts off quickly

This is difficult because i think it is night time where i live when it is daytime where you live.

Now,

Major Issue

I can't believe  I didn't see this earlier.    Where are your vertical stabilizers ?   What is keeping you stable in yaw ?  When you mentioned losing control, I always assumed you mention in pitch, because that is the harder problem to solve.  I like to use big S wing strakes rotated vertical, and slide them to the back of the airplane.  maybe one on top of each outer engine pod.   But any tail fin is better than none !

Moderate Issue 

In your latest pic,  I see two extra Whiplash engines on the back of the NERVs.    I think this is a bad idea.    That is another four tons the NERVs will have to push to orbit, after the jets have stopped working.   I normally find you need twice as many nervs as jet engines.

Minor Issue.

In the last pic you added a pair of shuttle vertical stabilizers as tailplanes.   They are very large for a craft this size, but ok.   The main thing is they are not mounted as far back as they could be,  they are quite close to your centre of mass.   IF this is your only pitch control surface,  this means they have to generate a lot of downforce to get the tail down and the nose up,  and that downforce subtracts from the lift you are making.   If they are further from Centre of Mass,   they have more leverage and can get the same effect with less down force.

Minor Issue 2

The solar panels are still not in service bay.   I don't think you need such a big solar panel.   A smaller one might take longer on Laythe,  but it doesn't matter really because you will be in high time warp while making fuel.

RE:

BTW i still don't see any Big S wing parts on your plane or am i looking at an old pic ?

 

RE:  Using KAL intake exploit on NERVs  so they work better in atmosphere

I think you asked this earlier.   

I sometimes use NERVs on Kerbin above 7km to help me get through sound barrier, if levelling off from my climb is not enough.

Otherwise it's a waste of fuel ,  I don't put them on until i am at 17km, in level flight and the jet engines are not able to accelerate me any faster.  NERvs are a lot more fuel efficient than normal rockets but still terrible compared to jets.

On Laythe, same principle.

On Duna,  the atmosphere is so thin, the NERVAs work great even at surface.   Which is lucky because Jets don't work on Duna (no oxygen)

 

 

 

 

Link to comment
Share on other sites

  • 1

Is this your first SSTO?

Regardless, I think you'll have more success if you limit your scope for now. It looks to me like you're trying to make an SSTO than can refuel itself and fly anywhere, which is a pretty tall order. SSTAs, as the KSP community likes to call them, are pretty extreme designs generally. You'll need a detailed understanding of KSP's physics and aerodynamics (and especially where they deviate from real life) and a fair amount of experience to pull it off.

If you've never built an SSTO before, I'd suggest skipping the NERVs and the drills/converters and just trying to build a mk2 based plane that can fly to orbit and back with 1 or 2 rapiers and no other engines.

If you've been to orbit with an SSTO before, Try building one with a NERV on it and some extra liquid fuel, See if you can make it to Minmus.

Once you can make it that far, build an SSTO that can do it with some cargo, then maybe stick some small refueling gear in the cargo bay.

 

Edit: I had a look at your pictures. You keep attaching things to the end of your NERV engines. That will block them from producing thrust. They'll still show rocket exhaust, but all that will happen is your nosecones or whiplash engines will be heated up by them. If you want to occlude the rear attach node for better drag you have to offset whatever part you use out of the way after or decouple it before firing the engine.

Edited by Zacspace
Link to comment
Share on other sites

  • 0
Posted (edited)

so my spaceplane stopped retrograding but it started ripping off its wings on liftoff instead

autostrut on all parts already

it says node break

Edited by imcute
this thread is very noisy and chaotic due to vanamonde merges
Link to comment
Share on other sites

  • 0

so im wanting to make a non KAL spaceplane

but that means that i should not use fuel consuming "S3 Vector" engines.

and that makes the speed of the plane not enough to achieve aerodynamic stability(the combination of forces that make missiles turn prograde and reentry pods retrograde)

how can i fly without aerodynamic stability?

Link to comment
Share on other sites

  • 0

this is the wrong subsection of the forum. this is the "tutorial" subsection, where people post tutorials. you're more likely to get help if you post in questions, as this is indeed a question.

also, you have 91 posts active, by now you should be experienced enough to know that you must give more information if you want people to be able to help you. all I get is that you are trying some kind of spaceplane with vector engines and that it is somehow aerodinamically unstable. and instead of trying to make your plane stable, you are trying to fly it while unstable.

All I can tell you is that if you want to fly an unstable vehicle, you can add lots of reaction wheels to compensate for aerodinamic forces. or, you could reshape it to make it stable.

Link to comment
Share on other sites

  • 0

Give us some clues please...

Does your craft blast off vertically from the pad,  or takeoff horizontally from the runway ?  Is it rocket only or jet ?

What is KAL ?  A mod ?  The S3 Vector engine is part of the base game.

If you are not allowed to use it for whatever reason,  Vernor thrusters are much more powerful than normal RCS , and can work at Sea level unlike normal RCS systems that are designed for space.

My best guess is that you're trying to build a vertical launch space shuttle type thing.   You've probably got non-symmetrical engine placement, which is causing the thing to flip,  before it gets going fast enough for aerodynamic forces to keep it straight.

Space shuttle replicas are the hardest type of launch vehicle to make.  

Link to comment
Share on other sites

  • 0
9 hours ago, AeroGav said:

What is KAL ?  A mod ? 

kay ayy ell overclocking

9 hours ago, AeroGav said:

whatever reason

too much fuel consumption(s3 vector)

exploits(kal1000controller)

9 hours ago, AeroGav said:

You've probably got non-symmetrical engine placement, which is causing the thing to flip

nope

9 hours ago, AeroGav said:

takeoff horizontally from the runway

spaceplane

 

better question:how do i fly without making the air pushing it on its place

the air gives a lot of effects:one creates instability which is proportional to wing size and another creates stability,which is proportional to speed.

i cannot use the latter one due to not being able to acheive that much speed without fuel exploits that i do not want to use

so i need to minimize the former effect by(im asking for this)

10 hours ago, Vanamonde said:

Stability or speed or both

both,but not enough speed is also okay

10 hours ago, Vanamonde said:

Pictures might help diagnose the problem. 

all i can supply is some pics of planes crashing

Link to comment
Share on other sites

  • 0

okay i found out that the centers should be near and the col should be slightly behind the com by looking at tut

wee!it works!

next step is to fly it to orbit and make it able to go to nearest planet in case of fuel low

it says 7829 dv but thats the sum of a nerv and two rapiers in average

lemme try mechjeb autopilot

aww man mech jeb does not know how to drive my plane and steers it into the ocean

Link to comment
Share on other sites

  • 0
5 minutes ago, imcute said:

this dumb guy even tilts the wings 90 degrees

Great news on the stability issues! I'm not the best designer or pilot of spaceplanes but I have managed to get a few to orbit by holding 5 to 15 degrees above the horizon on the navball (depending on TWR), you should have plenty of propellant.

Edited by James Kerman
More info
Link to comment
Share on other sites

  • 0
Posted (edited)

okay changed rapier to jet engine(i have a nerv so omit oxidizer) and added an isru set,see if it can work

29 minutes ago, James Kerman said:

5 to 15 degrees

okay ill try it

i thought that we should do 45 degrees!me still learning

whoops

jet engine is not working due to lack of intake(why didnt the rapiers not work?idk)

Edited by imcute
im not dumb :)
Link to comment
Share on other sites

  • 0
3 minutes ago, imcute said:

i thought that we should do 45 degrees!me dumb

Please don't say that, you are just learning and spaceplanes in KSP are something of a black art.

Just now, imcute said:

okay more intake,but (my centers are still in the right place) it resumes tumbling after takeoff

A picture says a thousand words in KSP and I'm sure our spaceplane loving members can assist in design if you have further issues. The forum itself cannot host images so we take a screenshot and upload it to imgur or google drive and then link to the image here.

Link to comment
Share on other sites

  • 0
5 minutes ago, James Kerman said:

A picture says a thousand words in KSP

yes ik

 

5 minutes ago, James Kerman said:

google drive

no

5 minutes ago, James Kerman said:

imgur

ok

maybe this would work?

https://img.kaiheila.cn/assets/2022-06/OrQ8O1LNwO19g0lf.png

problem=plane okay if it could launch,but it could not and it gains wobbling energy from zero point energy evern when autostrut on

fixed,putting landing gear on fragile wings is not a good idea

Link to comment
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.

 Share

×
×
  • Create New...