Help with SSTO transport.

[Gamer217]

Help with SSTO transport.

I need help building a SSTO shuttle for colony missions that can take off like a plane, carry 3 passengers (a hitchhiker pod would be nice but I don't now how feasible it is) and it I would like to put it in my carrier (if it has to dock outside on the bottom so be it but inside would be great). The carrier (modular construction of course) is in the design phase and here are some screen shots to give an idea of how much space there will be in terms of width and height (modules will allow me to make it as long as I like):

Can anyone help me with this design.

EDIT: So far I'm staying away from jets as I'd like this to be able to take off in any planet (well maybe not Eve), even if it doesn't have an atmosphere in which case unusable jet engines seems like dead weight and it needs to be all stock parts because I'm seeing what I can do with that instead of using mods.

[Killenger]

I'm using 12 turbofan engines and 12 nuclear engines for my newest build to bring a 20 ton payload into space.

Use mechjeb, make your basic craft, balance the thrust to wieght ratio of the nuclear engines to be between .5 and .6 when your craft is complete, I usually start at 1 to give me plenty of room for adding fuel to the final design.

In order to get into orbit with a thrust to weight ratio that low your going to have to burn almost strait upwards as soon as you kill your atmospheric engines - but your going to orbit at an isp of no less than 750 when you do it this way, you'll actually have extra fuel.

Your going to need a ton of lift at the back of your craft and you are gunna have to use atmospheric engines.

So in short start with this

1. 2 jet fuselages like dual mk2 tanks

2. 12 tons worth of rocket fuel (liquid and oxidizer)

3. Roughly 10 intakes

4. 4 nuclear engines

5. 4 turbofan engines

6. Add wings so your center of lift is behind and stays behind your center of mass, if it doesnt take off and you already have huge wings in the back try adding control surfaces to the front.

7. Add vertical control surfaces for stability (tail-fins)

8. Add landing gear (pay attention to how level your aircraft is and how that affects its takeoff)

9. And your hitchhiker container of course

Hope it makes sense and helps, good luck

Edited June 14, 2013 by Killenger

[Gamer217]

Ok but what if I'm on a larger planet like Duna and there is no Oxygen, would that still be enough to get into orbit?

[Killenger]

Test it for me haha,

Duna has less gravity than Kerbin so I think so.

I just know how to get em off the ground

If you feel the need for more thrust add some of those tiny red engines or put a single aerospike on it with your nuclears

I'm all about efficiency now to spare me refueling

PS.

Basically what I'm trying to say is the most efficient number of atomic engines for an SSTO is a thrust to weight ratio between ~.5-.6 (very approximate, its not easy to test these things since there is so many variables such as when you kill your atmospheric engines) But to get into orbit like this you have to have a balanced air intake to drag ratio with balanced lift that has the proper amount of control surfaces. You also need a long near vertical nuclear burn after you kill your air intakes and air-fed engines (it may seam like your going to loose your apariapsis but at the last minute you'll start gaining again, usually around 40km).

BTW most of my craft are kinda unflyable without the use of mechjeb as the ASAS sometimes does not provide enough torque alone - so when your climbing you will want to set mechjeb (I highly recommend it). I have played with using multiple avoinics packages/sas modules to help my ASAS maintain control, it seams to help a bit adding extras when you can't seam to get a larger craft under control.

I always start by building a nice diamond shape of wings around my aircraft, add wings until the thing starts to seam somewhat neutrally buoyant by the end of the runway, then add a small amount of "bite" to your wings by tweaking their attitude a bit (to slightly curve your wings use shift key + W, A, S, or D key) if the thing flys down the runway like a floppy fish and spirals out of control, try adding some down force to the front of it by curving your frontmost wings/control surfaces down. Also how level your craft is when sitting on its landing gear effects this alot, if the nose points up on its landing gear then the thing will have more of a tendency to lift early which can be good or can spin you out of control on the runway.

Try to make your craft look like this as much as possible (include your wings into this shape)

<---X-O----------\

Front of your aircraft = <

Center of mass = X

Center of lift = O

Edge of aircraft's rear most wing = \

If you find going full nuclear beyond the scope of what your trying to accomplish here, I still recommend going at-least half nuclear and using something like aerospikes. Use the aerospikes only in pulses when you need the thrust, the rest of the time burn the nuclear engines for longer efficient burns.

Nuclear engines will make the difference between a half tank of fuel left in orbit, and almost no fuel left in orbit.

I just checked the gravity of Duna, I think you would be able to take off from there as your TWR is going to be atleast .5 and Duna has less than half Kerbins gravity. (Not to mention your TWR will be alot higher because you just used enough fuel to get to Duna)

One more thing - the larger your craft is, the harder it will be to land it. Landing is really not my thing and its not something I make plans on doing, I'd perfer to send an SSTO with a lander module as payload into orbit around my target planet, drop the lander payload, visit the planet, return the SSTO, fly back and stay in orbit docked in a station somewhere.

I'll land my smaller SSTO's that weigh like 10-30 tons but anything bigger than that has been tricky for me.

-Another note, I've been working with my new SSTO all night and I discovered that a TWR of .5 is where your nuclear engines will come close to overheating, my SSTO is at .54 TWR and it comes to about 85% overheat, just some good FYI

Edited June 15, 2013 by Killenger

[Gamer217]

Ok so I have tried building it to little success. It spin out of control the moment I full back for take off. Here is the craft so far:

Also how do I get Mechjeb to fly the spaceplane, I installed a unit on board but it's covered by the Hitchhiker's hatch in the screenshot.

[Killenger]

Your center of mass is too far above your center of lift.

I hope you have nuclear engines on the bottom as well, otherwise that thing will never fly. You gota be as symmetrical as possible. Your center of thrust has to be inline with your center of mass.

Use mechjeb surf feature, before take off set it to 30 degrees and wait till your in the air to hit execute, if your plane is stable enough mechjeb will take over no problem.

[Gamer217]

Thanks I'll try it out.

[Killenger]

One more thing - A large cockpit is unneeded extra weight, use the lightest possible till you get the hang of it or just have it unmanned with a hitchhiker can attached.

I hope this is not to large for you starting out, think simple. It's easy to get carried away and over complicate the design.

Scratch having the wings at angles, for now stick to strait wings and rely on your control surfaces to get you off the runway. Having your wings curve down or up slightly is only beneficial in certain circumstances. I feel that throwing that in there on your first try could cause the thing to get so complex that it will never work.

This is an older SSTO of mine, but it is a good example of how the back of your aircraft should look, don't use aerospikes though.

noticed the image was not working, try this instead - http://postimg.org/image/mig1mot1d/full/

See how the center of thrust is inline with the center of mass?

If you try all this and the thing still spirals out of control off the runway provide me with these pictures: top view, bottom view, and rear view. Also a picture of the instant you start spinning out may help me tell you whats wrong.

Edited June 27, 2013 by Killenger

[Gamer217]

Thanks I'll start playing around and looking at some other SSTO's

[Killenger]

http://forum.kerbalspaceprogram.com/showthread.php/33312-Showcase-SSTO-s%21-Post-your-pictures-here

This will give you a broad view of what works.

[Tex_NL]

On most atmospheric worlds jets are your friends. On Duna you won't really need them as it has low gravity and thin atmosphere. Eve is hard anyway you put it.

The plane on the left is my most successful (and easiest) SSTO spaceplane thus far. It's capable to getting a pilot and 6 passengers to orbit and back with fuel to spare.

The one on the bottom right is my SSTO cargo plane. Guaranteed to get a 20 ton payload into LKO.

[Killenger]

Did you use robotics? What mod and what version you running?

I've been wanting to make a robot armed station that unloads cargo. But I have been running the newest version of KSP.

[Tex_NL]

Did you use robotics? What mod and what version you running?

I've been wanting to make a robot armed station that unloads cargo. But I have been running the newest version of KSP.

The planes are mostly B9, the wings are pWing. Most of the station is Large Structural/Station Components, the arm you see (and those still in the big cargo plane) come from Romfarer's Robotic Arms Pack

[KerbMav]

If I only could fly these things - tried the smallest stock plane yesterday - was the first Kerbal I ever really lost (not counting reloads or end flight-repeats during launch) ...