[1.1.x] Space Shuttle Engines (2016-07-03)

[Synthesis]

I am pretty sure that you have way too much thrust on your tank side. In addition the shuttle is too high on the tank. The shuttles engines must be able to turn the shuttle as the CoM shifts. Your CoM is almost at the same height as the shuttle engines. The best thing the engines can do here is pushing the shuttle sideways but they can hardly turn it.

Try reducing the thrust on your tank side or increase the thrust on the shuttle side. In addition try to have the CoM higher.

I hope this helps.

Okay, I can definitely reduce the height of the shuttle on the tank, but I should have been more specific: I was hoping to have the shuttle ride up on its launch vehicle, Buran-style, rather than burning its own fuel immediately. Is that totally impossible? If so, I'll need to set up a line to transfer whatever fuel is left in the lift vehicle back into the shuttle, I guess.

Otherwise, though, I can mount weaker engines on the lift vehicle. I don't expect that will be tough. And thank you for your help so far.

[Malsheck]

For those folks who are having issues making your shuttles flyable, here's a suggestion. Take the boosters off and then look at your Center of Mass and your line of thrust. You want to have the line of thrust practically pointing at your CoM. Now, here's where it gets interesting. Boosters... If they are too weak, you dont get off the pad or your shuttle's thrust will be pulling back against the stops trying to prevent your shuttle from nosing over. Too strong, and you'll notice that your shuttle engines are pointing nearly strait down with the control maxed out pushing forward.... but instead it fall over backwards.... This usually happens at higher altitudes when the CoM is shifting towards your shuttle and away from the tank.. But the booster is still going just as strong as it was on the ground... just lighter. So the trick is to find a booster that will last til roughly 18km-20km giving you as close to pegged vertical speed as possible... but will burn out prior to your tank becoming too light. I actually compensated by bringing too much fuel. This also allows me to do a solid burn all the way til Pe while pitching down to limit Ap from climbing. I'll see if my internet behaves long enough to upload a demo video. If I can I'll post it on this thread.

Edit: Looks like the video will have to wait. However, I did find a good picture demonstrating what I was saying above:

Edited November 18, 2013 by Malsheck

[The Destroyer]

I got a problem with the Big bang engine- when I try to place it in the VAB, the game starts to melt. Aka lag.

EDIT: Same problem as thing guy

Ok, i have an performance issue.

When the Rotating Big Bang Engine 1 is in it's -15 degree mode, it lags like crazy, like 20 fps.

But if i change it to straight, the lag disappear.

Edited November 18, 2013 by The Destroyer

[DomDiaemus]

It sounds as if your TWR is bad. You also might want to add some more boosters because the stock boosters are just not good enough. For my KM Atlantis I used four boosters instead of two. It looks nice, too.

A stronger version of the X2. I has the same efficiency and TRW as the mainsail. It packs 500kN. So three of these will be exactly the same as the mainsail or the large BB1. Using four or five will give you quite some more thrust.

If the shuttle engine FSX2 is to mimic the real shuttle then the Isp SL+Vacuum seem a bit water down (unless are based in some formula and not guess work... btw know nothing about this but just got interested looking at shuttle info)

Current values: for Isp sea level and Isp Vacuum:

atmosphereCurve

{

key = 0 330

key = 1 380

}

Values based on "wiki" shuttle engine (http://en.wikipedia.org/wiki/Space_Shuttle_Main_Engine)

atmosphereCurve

{

key = 0 453

key = 1 366

}

With that yeah, it that makes the fuel to last till orbit to release the tank once reached apoapsis and not on its ascend... well thats me thinking

Edited November 18, 2013 by DomDiaemus

[Netris]

If the shuttle engine FSX2 is to mimic the real shuttle then the Isp SL+Vacuum seem a bit water down (unless are based in some formula and not guess work... btw know nothing about this but just got interested looking at shuttle info)

Current values: for Isp sea level and Isp Vacuum:

atmosphereCurve

{

key = 0 330

key = 1 380

}

Values based on "wiki" shuttle engine (http://en.wikipedia.org/wiki/Space_Shuttle_Main_Engine)

atmosphereCurve

{

key = 0 453

key = 1 366

}

With that yeah, it that makes the fuel to last till orbit to release the tank once reached apoapsis and not on its ascend... well thats me thinking

Remember that Kerbin and the kerbals are scaled down compared to Earth and humans.

[wasmic]

Remember that Kerbin and the kerbals are scaled down compared to Earth and humans.

Aye, it's not exactly like we need the higher I_sp. I can already get to orbit with a tank that is smaller - relative to the shuttle - than the real thing.

[dtobi]

The new update is out.

[dtobi]

There is a new engine now (x3) and a new large example craft. Look at the album in the first post. I hope you like it. TWR and efficiency are the same as the mainsail.

[wasmic]

Hey dtobi, do you have any tips on placing SRB's? I can't get them to act balanced.

[dtobi]

Hey dtobi, do you have any tips on placing SRB's? I can't get them to act balanced.

What exactly is the issue? You can look at the example craft in the download file, too.

[wasmic]

I just can't seem to place them, and still get my shuttle to fly straight. I have already made a shuttle, which is capable of flying just fine when the SRB's are not attached. Maybe I just need to poke around a bit more tomorrow, there was some trouble with launch clamps.

[dtobi]

I just can't seem to place them, and still get my shuttle to fly straight. I have already made a shuttle, which is capable of flying just fine when the SRB's are not attached. Maybe I just need to poke around a bit more tomorrow, there was some trouble with launch clamps.

Is your shuttle flipping forward or back?

[The Destroyer]

I still must ask about m y previous problem of the big bang engine. Is this fixed?

[SFJackBauer]

For those folks who are having issues making your shuttles flyable, here's a suggestion. Take the boosters off and then look at your Center of Mass and your line of thrust. You want to have the line of thrust practically pointing at your CoM. Now, here's where it gets interesting. Boosters... If they are too weak, you dont get off the pad or your shuttle's thrust will be pulling back against the stops trying to prevent your shuttle from nosing over. Too strong, and you'll notice that your shuttle engines are pointing nearly strait down with the control maxed out pushing forward.... but instead it fall over backwards.... This usually happens at higher altitudes when the CoM is shifting towards your shuttle and away from the tank.. But the booster is still going just as strong as it was on the ground... just lighter. So the trick is to find a booster that will last til roughly 18km-20km giving you as close to pegged vertical speed as possible... but will burn out prior to your tank becoming too light. I actually compensated by bringing too much fuel. This also allows me to do a solid burn all the way til Pe while pitching down to limit Ap from climbing. I'll see if my internet behaves long enough to upload a demo video. If I can I'll post it on this thread.

Edit: Looks like the video will have to wait. However, I did find a good picture demonstrating what I was saying above:

Keep in mind that the center of mass of the external tank was off the center. The upper 35% of the ET houses the liquid oxigen tank, which comprises 82% of the total mass (620 tons). The remaining 65% of the tank is liquid hydrogen which comprises the remaining 18% of the mass (106 tons). Therefore to get a closer approximation of the shuttle center of mass during ascent, the center of mass of the external tank should be about a third down from the top.

Also, may I ask you from where is that picture? I don't remember seeing it from my researches of the STS program.

[wasmic]

Is your shuttle flipping forward or back?

Well, I got it to fly straight when the boosters are on, but now it starts tumbling when I jettison the SRB's. Maybe I should try with some gimballing srb's, like the ones from KW and NovaPunch.

EDIT: My problem right now is that my Shuttle tends to spin (i.e. rotate around its centerline). Would it be possible to get a MKIII to 3*1.25m converter?

The reason that I use MKIII is, that I have installed TouhouTorpedo's MKIII expansion and Crew Tank.

Edited November 19, 2013 by wasmic

[dtobi]

I still must ask about m y previous problem of the big bang engine. Is this fixed?

Unfortunately not. I can't reproduce the error. Can you send me your craft file?

[dtobi]

I still must ask about m y previous problem of the big bang engine. Is this fixed?

I made a new release with a non-rotating BB2 engine. Can you try if this engine also creates lag? BTW: the heat animation works on the BB2 (it doesn't for the rotating BB1).

[ddenis]

Why do the top part of tanks have 0.2 drag? Shouldn't it be lower?

Edited November 20, 2013 by ddenis

[dtobi]

Why do the top part of tanks have 0.2 drag? Shouldn't it be lower?

I need to fix that in the next release. Are you using FAR?

[The Destroyer]

I used the LLL pack with it, maybe that's it?

Will try the new one.

I deleted the craft long ago, but on all 5 shuttles they all had lag

Here was one

Another thing: Tiberdynes shuttles uses a plugin to always put the engine through the CoM. You could use it this and make shuttles MUCH easier.

[Tiberion]

No it doesn't, not since 0.19. It was extremely limited anyway - only one active engine at a time could be compensating, which is why my shuttle engines were always single parts instead of 3 separate.

The 0.22 SAS is sufficient to keep the engines pointed in the right direction, as long as you have enough gimbal range.

[bs1110101]

I have an idea for the the big bang engine, make it work like the firespiter vtol engine, and if that does work, i vote for making all the engines have it so that buran style shuttles are easier to make.

[Synthesis]

Well, dtobi, thank you for your advice: I was able to get my shuttle in orbit finally, after a lot of adjustment. It might not carry much cargo, but it's a start!

[dtobi]

Well, dtobi, thank you for your advice: I was able to get my shuttle in orbit finally, after a lot of adjustment. It might not carry much cargo, but it's a start!

Great to see you mastered it. Have you already tried the new and stronger x3 engine?

[FellipeC]

Love this pack. But for some reason the tank separators are very hard to fit in place. It's just me?