Space Shuttle (help)

[Thraeorn]

Hello,

I am looking for anything of how to get a shuttle (STS) into orbit. Just like the one that Nasa used. With the new MK3 parts, a stock part replica is possible and that is what I created.

There are many issues that I have and am looking for help to counter the problems I been having.

First is the weight issues.

Second is the Fuel Issues

Third is the Release timeing.

Forth is the orientation.

So lets talk about weight. With an MK3 nose, the large cargo bay and the shorttank mk3 to 3.75adapter.. I took 4 steel panels and used that to mount my 3 SME(shuttle main engines) to them and gimbled them out (like you should) But because of the hallow bay area and the engines in the back, this causes weight to be in the rear making it hard to control (I also have 2 small tanks and the LVT-30 engines on them as OMS) My question is how do you get more of a balance out of this thing with out compromising the aesthetics from a shuttle replica?

Second, Fuel.

As it drains it will create an imballance and shift the weight. To make the replica, with the parts listed as above the shuttle is litteraly 50% of the real one. 122ft long with a wing span of 78 feet boosters will reach 149 ft with the ET (external Tank) reaching 184ft (of course convert to meters) Anyhow this means that the SRB's that come stock are too small. So I opted for Liquid Fuel Boosters instead. The SRB acts as a single fuel tank and thus always keeps the COG center with the tank, but with the LFB's this isn't possibe due to the size. I need to couter the weight with an even fuel flow. How do I do that, other than fuel lines? And should I be trying to dump fuel from the bottom of the stack up or vice versa or try to keep it all even?

Third, Release.

How long should the SRB's burn before I release them to rely on the ET. From what I heard the ET should last all the way into orbit. What altitude should I be at and will this be before or after I begin my Gravity Turn which is at 6,900 M?

Fourth. Orientation

Im going east obviously though should i begin by pitching the nose down to be right side up or should I pitch back to be upside down ? (or does this make a difference?)

[Anquietas314]

Scott Manley did a video on shuttle building a few weeks back:

It doesn't include the Mk3 parts, but it should help

[Pecan]

...There are many issues that I have and am looking for help to counter the problems I been having...

Replicas of the American Space Shuttle are hard to build and fly in KSP.

SSTO rockets are easier, VTVL SSTO jets more efficient, spaceplanes more efficient and better looking.

Unless you're just setting yourself the challenge of this for the appearance of it there really is no point in trying. I'm assuming you're new(ish) to KSP; just save yourself the headache.

[Anquietas314]

Replicas of the American Space Shuttle are hard to build and fly in KSP.

SSTO rockets are easier, VTVL SSTO jets more efficient, spaceplanes more efficient and better looking.

Unless you're just setting yourself the challenge of this for the appearance of it there really is no point in trying. I'm assuming you're new(ish) to KSP; just save yourself the headache.

Scott actually mentions later on in the video that something like the shuttle is just a really bad idea for a spaceship anyway because of the huge amount of technical complications from the design. Also, the common term is VTOL: Vertical Take Off and Landing.

[Pecan]

...Also, the common term is VTOL: Vertical Take Off and Landing.

Unfortunately there is a profusion and confusion of terms. As I understand it "VTOL" means a plane that can take-off and land vertically - such as the Harrier Jump Jet. I'm using "VTVL" instead to mean a jet-powered ("tailsitter") first stage that does not have wings/landing-gear and launches and lands like a rocket. Opinions on how to make the distinction clear are welcome ^^.

[Anquietas314]

Unfortunately there is a profusion and confusion of terms. As I understand it "VTOL" means a plane that can take-off and land vertically - such as the Harrier Jump Jet. I'm using "VTVL" instead to mean a jet-powered ("tailsitter") first stage that does not have wings/landing-gear and launches and lands like a rocket. Opinions on how to make the distinction clear are welcome ^^.

What's wrong with "tailsitter"? It gets the meaning across perfectly, and isn't an excessively long term.

[The_Rocketeer]

Let me couch this by saying this is one of my current projects. I have a shuttle that can reach a sub-orbital trajectory, I'm still tweaking it to reach orbit, but it's close. With the old Mk3 parts I had a fully working craft using TehouTorpedo's Mk3 cargo bays.

So lets talk about weight. With an MK3 nose, the large cargo bay and the shorttank mk3 to 3.75adapter.. I took 4 steel panels and used that to mount my 3 SME(shuttle main engines) to them and gimbled them out (like you should) But because of the hallow bay area and the engines in the back, this causes weight to be in the rear making it hard to control (I also have 2 small tanks and the LVT-30 engines on them as OMS) My question is how do you get more of a balance out of this thing with out compromising the aesthetics from a shuttle replica?

The fuselage fuel tank should be empty at launch. The real shuttle carried no fuel in the orbiter except for small, high-mounted tanks for the OMS engines. Carrying fuel here complicates your design, and adds dead-weight, because you can never use it without drastically altering your CoM. I also recommend the LV-909s for OMS, they have easily enough thrust for orbital manoeuvres, weigh less and have higher Isp.

Second, Fuel.

As it drains it will create an imballance and shift the weight. To make the replica, with the parts listed as above the shuttle is litteraly 50% of the real one. 122ft long with a wing span of 78 feet boosters will reach 149 ft with the ET (external Tank) reaching 184ft (of course convert to meters) Anyhow this means that the SRB's that come stock are too small. So I opted for Liquid Fuel Boosters instead. The SRB acts as a single fuel tank and thus always keeps the COG center with the tank, but with the LFB's this isn't possibe due to the size. I need to couter the weight with an even fuel flow. How do I do that, other than fuel lines? And should I be trying to dump fuel from the bottom of the stack up or vice versa or try to keep it all even?

No parts will scale correctly with the new Mk3 parts - they're just too big (even the biggest tanks are tiny compared with a properly scaled 'real' external tank). However that's not really an issue. I stick with the SRBs, even if they look a bit small. They're lightweight, high thrust, and have a much better aesthetic, not to mention being that bit like the real thing.

The mass issue, you're forced to use a segmented tank, which means fuel management becomes an issue that it wouldn't be for a real shuttle - the CoM for the real shuttle and tank would move linearly (excluding the SRBs). For you it won't. I've found it's best to experiment. My current design drains the bottom tanks until SRB separation, then drains top down to prevent overbalancing the other way. Keep an eye on the steering needle guages in the bottom left, particularly pitch - once you understand how the SAS pitch responds to shifting fuel mass, you can start to transfer fuel to correct (again, the real shuttle wouldn't have to do this).

Third, Release.

How long should the SRB's burn before I release them to rely on the ET. From what I heard the ET should last all the way into orbit. What altitude should I be at and will this be before or after I begin my Gravity Turn which is at 6,900 M?

The SRBs basically need to stay on until your orbiter+ET have TWR higher than 1 (which they won't at launch without the SRBs). They also need to stay on until the fuel mass has shifted such that the orbiter main engines are thrusting through the CoM. I current drop them at about (from memory) around 6-7000m, and keep up a more-or-less vertical trajectory. I don't start the gravity turn until my orbital prograde marker has reached at least 45 degrees from vertical - this is usually around 13000m. The reason for this is if my vertical speed is too low when I start the gravity turn, I'll fall back to the surface before I build up enough horizontal speed to reach space.

Yes the ET stays on almost to orbit velocity. It should only take a little push from the OMS engines to make a final circularisation, so that the ET will fall back to Earth. Remember, all your fuel should come from the ET until you start the OMS engines, and they should draw from small dedicated tanks on the orbiter.

Fourth. Orientation

Im going east obviously though should i begin by pitching the nose down to be right side up or should I pitch back to be upside down ? (or does this make a difference?)

You should launch with the orbiter's dorsal side facing East, and pitch backwards to be upside down. You make a right-side roll manoeuvre at the edge of space before dropping the ET. It makes a difference because when you lose SRB thrust, you basically have to heft the tank up onto orbiter's thrust. Also, the draining fuel will tend to make the ventral side of the shuttle progressively lighter than the dorsal side over time, to the shuttle will tend to dorsal rotate anyway.

Final tips:

Engineer the shuttle with a representative payload (like a Jumbo fuel tank or something lighter, depending on your planned typical payload mass) already in the bay. Otherwise, a shuttle that you engineered to launch empty won't launch anymore once you put something in it due to different CoM.

Design the shuttle to LAND. I can't overstate this enough - if the orbiter can't glide in and land without any thrust at all (including remaining OMS), you're not doing it right.

Happy to discuss further. This is a damn hard project, but very rewarding when it works.

[Parkaboy]

Here's how I design my shuttles, in a few simple steps:

1- Build the shuttle you want with a payload already on the cargo bay. You'll need two sets of engines: orbital engines pointing to the COM of the shuttle, and ascent engines pointing a bit below. It works better if you have two "layers" of ascent engines (I use two pairs of LV-T45s for MkII and three Mainsails in a triangle for MkIII);

2- Add wings to the shuttle. Make sure the center of lift is a bit behind the COM, even with the shuttle unfueled. You'll probably want to do a test launch using infinite fuel to see if the shuttle can glide well with no fuel and no cargo;

3- Add a decoupler under the shuttle and attach fuel tanks. A fuel line should take this fuel into the shuttle. If your shuttle has strong enough engines and reaction wheels, you only need a fuel tank to be discarded. Make sure to plan the fuel flow so the fuel flows toward the center of the tank.

4- Take the fuel off the drop tank to see where the COM is. Reduce the thrust from the orbital engines and the "top layer" of ascent engines to 0. We want to rotate the "bottom layer" of ascent engines (currently the only ones active) so the center of thrust points to the current COM;

4- Now we activate the "top layer" and fill the drop tank, and rotate the "top" engines so the new COT points toward the new COM. We can then use this to our advantage: we can either set up an action group to toggle the "top" engines on and off as the COM changes mid-flight, keeping the thrust roughly balanced, or we can do it by reducing the thrust of the "top" engines mid-flight as the COM moves (though the second option is trickier and works better if you have only a single engine on top);

5- Add the pair of decouplers and SRBs to the sides of the drop tank, making sure to pay attention to the shifts on the COM and COT. We want to keep those aligned.

6- Point the whole ensemble upwards, with the top of the shuttle pointing to the direction of the orbit (usually east), and launch. A good strategy is to drop the tank just before circularizing the orbit, finishing the burn with the orbital engines. Make sure to set up action groups to switch off the ascent engines and turn on the orbital ones.

This set up works wonderfully with MkII parts. It's trickier with MkIII, because the parts are heavier and there's a greater chance of spontaneous disassembly during flight.