How to build an ssto?

[Prat4545]

I'm seeing some videos about sstos but how do u build sstos that can go into space? any tips and tricks thankfull!

I'm playing science mode right now on a high tier level (i hope its my first playthrough)

sincerly Prat!

 

[Vanamonde]

Your thread has been moved to the Gameplay Questions subforum, since you're seeking help rather than offering it. 

Now that we're here, making an SSTO is one of the two or three hardest things to do in this game. There's no simple formula for getting it right. You will have to make the craft balance properly as an aircraft full of fuel on the way up and still balance properly as an aircraft on the way back empty of fuel, and function as a rocket in between. I played the game for a couple of years before I was finally able to make my first one that worked and I'm still not very good at it. Maybe get a feel for the game with some simpler accomplishments before returning to this challenge? Just a suggestion. 

[Spricigo]

 "SSTO" is supposed to be Single Stage To Orbit. Got into orbit without dropping pieces? Than is an SSTO. (Most of my SSTOs were a bunch of fuel tanks attached to an engine. But I guess that is not what you are interested in.) 

 

So... You need to decide what kind of craft you want and design it to not drop parts. It will need more fuel and slither stronger engines but also be careful to not put too much of everything or it'll be to heavy to work properly. 

 

 

 

 

 

[katateochi]

Assuming we're talking about an SSTO spaceplane, then here's a few things I've picked up.
- DRAG!! drag is extremely important, design your craft to have as little drag as possible. That means having no or very few attachment nodes left without an aerodynamic part to end it. As important on the back of the craft as the front.
- Angle of attack. angle the wings on the craft up very slightly, how much depends on the craft, but the aim is that when flying level the lift from the wings should be keeping the prograde marker on the navball crosshair. 
- The magic number of the Rapier Engine. 450. When you take off, don't try to climb too fast, fly at a slight upward pitch (5-10), the aim is to gain speed. Once you reach 450m/s the Rapiers will be performing optimally, then start to climb. (How you fly your SSTO makes a big difference to it's efficiency, they're much less tolerant of bad piloting than rockets!)
 

Don't be too ambitious at first, just try a single pilot craft to low orbit to start with.  You can build a really small LKO capable SSTO and gain a lot of understanding from it before trying something bigger.  Grab some craft made by others and pull them apart.
Here's a couple of mine: This one is very small and simple, but doesn't have angled wings. This one is also quite simple in design but has a good range, it's a good example of the slightly angled wings (also is a mostly liquid fuelled design). And this one is on the larger side with a 67ton cargo capacity. (my craft are a bit out of date, but should load in the current KSP) Or search for SSTO on KerbalX.com and there are loads of great designs which you can pull apart and see how they're made.

 

[Fraktal]

3 hours ago, Vanamonde said:

I played the game for a couple of years before I was finally able to make my first one that worked and I'm still not very good at it.

Sloooowpooooke~.  Started the game in January 27, 2018, got my first SSTO to orbit on February 16, first SSTO Mun flyby on February 26 after a one-week hiatus, first SSTO Mun landing on February 28.

Anyway. First SSTO design of mine that reached orbit, using a Mk2 fuselage:

Second design, built entirely out of Mk1 parts and with much higher wing surface:

Third design with ventral monoprop thrusters to VTOL on the Mun:

@Prat4545, feel free to take notes. I used 3-4 Whiplashes and 4 NERVs (two on top, two on bottom) for propulsion instead of Rapiers, so it was running entirely without oxidizer. For the second design, I apparently used a 15° ascent angle while on Whiplashes, then pulled up to 45° upon flameout.

Edited June 12, 2020 by Fraktal

[Prat4545]

hm thanks for the tips! i'll try it but do you guys have any more tips for a space plane?

[AHHans]

14 minutes ago, Prat4545 said:

but do you guys have any more tips for a space plane?

Well, a general suggestion from me would be to first build regular planes that fly well. So that you learn where you need to put the CoM and CoL for a plane to fly well. Once you have a feel for that, then keep in mind that the CoL that is displayed in the SPH doesn't represent all aerodynamic forces. In particular when planes fly high (where the air is so thin that it doesn't generate much lift) and fast (at close to orbital speeds) then the drag becomes much more important in comparison to the lift, so then the center of the aerodynamic forces on your plane can shift.

[Linkageless]

Where your drag is, compared to C/o Mass, is definitely the first and foremost consideration.
Something possibly not mentioned is that the shock cone intake is lowest drag for its performance and only one is normally needed per four rapiers.

Also, stick standard intakes on the Nodes at the back of all your engines, then offset them so they don't block the thrust.  This removes the trailing drag from the engine and may be that little extra that enables you to go supersonic for the rapier and later hypersonic as you're leaving the thicker parts of atmosphere.

 

[Fraktal]

1 hour ago, Prat4545 said:

hm thanks for the tips! i'll try it but do you guys have any more tips for a space plane?

Big wings. You're going to be flying high where the air is very thin, so you need a lot of wing surface area if you don't want to stall out. If you don't have enough, you'll start losing altitude due to insufficient lift, forcing you to nose up in order to point your engines downwards to compensate against gravity, which in turn causes you to lose forward airspeed due to the extra drag of flying belly-first, which in turn forces you to expend more fuel to reach orbit, in a vicious cycle.

Also, when you're designing the spaceplane, make sure that the plane is not too stable (ie. center of lift should be very close to the center of mass). When you enter the atmosphere, you ideally want to do it belly-first to aerobrake as hard as you can (set SAS to radial-out and use roll controls to keep the wings perpendicular to your trajectory); the plane will instead want to nose down, which carries a real risk of you not decelerating enough during the descent to pull up and thus avoid plowing into the ground at terminal velocity. The more stable the plane is, the harder it will be for you to keep it pointed in any direction other than nose-first unless you pack it with an excessive number of reaction wheels.

[Prat4545]

okay i'm trying it now!

[FleshJeb]

 

[RoninFrog]

2 hours ago, FleshJeb said:

 

Ouch!  That "what not to do" example looked an awful lot like my first SSTO spaceplane...

Edit:  Ouch again!  The Mk3 engine mount is both in his "what not to do" and on my second SSTO spaceplane...

Maybe I should read up on this stuff.

Edited June 14, 2020 by RoninFrog