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How to make a working Space Shuttle or spaceplane


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Hello everyone, It's Trekkie148 here, I'm just wondering on how to make my space shuttle stable, get to orbit, rendezvous, docking with an object, maybe mun orbit, and mostly mk2 and mainly mk3. I am using the mod Kerbal Engineer Redux  and for visual Planet Shine to see the ship from the dark side of a celestial body. When ever I make a orbiter that looks like and supposed to act like the NASA space shuttle and I also empty out the tanks of the orbiter and put on the CoM and CoL indicators and sometimes CoT all standing for Center of Mass, Center of Lift, Center of Thrust, and I try to make the CoL closer to the CoM, I seriously do not know about what is happening what is happening with my design because it keeps on flipping my spacecraft either while landing or Reentry. This thread will be updated tomorrow on Thursday November 22 2018. Stay tuned, But do tend to give me help and reply. This helps out a lot. Thank you everyone.

Also Happy Thanks Giving! :cool:

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13 minutes ago, Trekkie148 said:

I try to make the CoL closer to the CoM

We could use some screenshots, but this is likely your issue.

It can be too close.  You also definitely do not want it in front of the CoM.  If it's flipping, you want to move the CoL back a little at a time until it's stable.

My 1st Gen Shuttle:

aeascreenshot618.png

2nd Gen Shuttle:

screenshot619.png

3rd Gen Shuttle:

2c0screenshot64.png

 

 

These are all in flight condition with empty tanks.

BTW, you may want to check out SmartParts for the fuel dump valve - really handy for re-entry.

 

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19 minutes ago, MR L A said:

@Trekkie148 was that screenshot (the one in the sph with CoM and CoL) fuelled or unfuelled? If it was fuelled then that's probably your issue... when the tank empties that CoM is going to shoot backwards...
 

@SiriusRocketry sounds like you need to realign your CoT and CoM

The one in the sph was unfuelled 

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8 hours ago, SiriusRocketry said:

I have this problem too- my shuttle flips when the OMS turns on. It's your basic 3 Vector and two Thud deal, but when the Vectors go off and the top mounted Thuds ignite, the craft pitches down like crazy.

In the VAB, turn your CoT on.  Turn the thrust limited on the vectors down to zero.  The CoT indicator doesn't care about what's in what stage.  Then you can try to line it up with the CoM.

First pic is with Vectors at 100, second is with them at 0.  Obviously, in flight, you'll simply have them turned off, but for the VAB, they need to be set at zero thrust.

44escreenshot16.png

caascreenshot17.png

It's not perfect, but it's better.

You won't get it perfect, it never can be.  Your CoM will move around with the payload and fuel consumption, so it'll take some practice to find a balance.  It's especially tricky since the gimble overreacts.

 

You'll also want an alternative control point in that line, otherwise you'll still have issues with the manuever node / prograde / whatever indicators not lining up with the CoT.

I stick a jr docking port between the CoT and CoM indicators. 

a36screenshot18.png

 

With the offset tool in local mode, you can see where "forward" (green arrow) will be when using the docking port as your control point.  You want that lined up best you can with your CoT.

4e5screenshot20.png

If "forward", CoT and CoM are lined up, you won't be flipping.  It's not important which way the cockpit is facing when you're in space.  Even if your CoT and CoM are lined up, if they're not lined up with your control point, it will try to gimble to get your CoT lined up with your control point, pointing it away from the CoM, causing flipping.

 

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I think the problem is more likely to be that the pitch control surfaces are pretty much inline with the CoM, so the plane has no pitch control authority. So it's going to be unstable in pitch no matter what you do.

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3 hours ago, bewing said:

I think the problem is more likely to be that the pitch control surfaces are pretty much inline with the CoM, so the plane has no pitch control authority. So it's going to be unstable in pitch no matter what you do.

So I would need a separate canard not at the Center of Mass that has pitch. maybe something like this? 

013.jpg

 

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Well, in order to make a succesfull space shuttle, you indeed need to build the shuttle in  your expected "Re-entry" state => the state in which the space shuttle will get back into the atmosphere. this is the start for balancing your shuttle out for descend and final flight to KSC. Next is adding the OMS engines. To balance these properly out you need to put all your tanks at half weight and see where the Center of Mass ends up to. once you have its location its just a matter of placing engines symmetric with their CoT aiming through the CoM. (!!!! Make sure that if you have attached the main engines for ascend, to turn the thrust limiter to "0". Otherwise your indicated CoT line will include the projected thrust from those engines, whilest in reality when in orbit, those engines are dead. This will throw your entire balancing off, causing instabilty. once that is done. you need to continue to build the shuttle up to its final shape, with all weight included ( engines, boosters everything), again turn the thrust limiter of the OMS engines to 0 for the same reason as earlier. Then detach the Boosters to exclude their weight from the CoM, put the weight of the main tank in half again, line the CoT of the main engines up and then put the booster back on their place. this might seem to set the CoT line under the CoM, but the tiny gimbal range will counteract it on the launch. and while the weight lowers, the CoM will drop too, stabilizing it even more.

I've managed to build a stable stock space shuttle like this. but i went on to mods for aesthethics and functionality like robo arms etc.

It all a matter of simulating all states of your shuttle and checking the balance out for each state.

A few pics of my old stock shuttle and the newer ones:

C774C3A8742A4610E1DE55E92A03ACCD9902D05320043FC7D9B767A548FD25064903735C679D1DF8631E3B0823E43C1F3426158FD7EE14DC83038C3F50072E51E01802A2E375A8F70D3C7196699751D2

DD3C4B2A0FB97C7B1C3CD014C8890F6A4CEB8B2D

And With my current Mods: 7D002F20B9217F6DD683D476AB5B06E1F48736CF

Edited by GRYPHUS-01
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Also, if you want some inspiration, there happen to be plenty of awesome shuttle designs in "my" STS challenge.

(A bit of a shameless plug, I admit :D )

But feel free to browse the entries a bit, and maybe even fly a mission or two, we have a small but passionate shuttle community over there :) 

Michal.don

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1 hour ago, michal.don said:

Also, if you want some inspiration, there happen to be plenty of awesome shuttle designs in "my" STS challenge.

(A bit of a shameless plug, I admit :D )

But feel free to browse the entries a bit, and maybe even fly a mission or two, we have a small but passionate shuttle community over there :) 

Michal.don

Aw thanks man!

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