Overview
This guide will, well, “guide” you on the steps or tricks that are used to make a SSTO (Single Stage To Orbit). The creator (i.e. me) of this guide recommends that you download and utilize the “Kerbal Engineer Redux” mod. I do not recommend you read this until you understand the basic concepts of “Thrust to weight ratio” “DeltaV” “Lift” “Fuel efficiency” and “how to make a plane”. If you DO know all of these, please continue.
Introduction
Hello whoever is reading this. This section is basically just gonna underline a few things concerning what you’re deciding to read. The whole point of the Single Stage To Orbit (SSTO) is that you need to make it so that your plane that you designed, can take only one stage and get into orbit of whatever height you can get (and maybe do some other things while up there). The most tempting reason for using an SSTO is to reduce the cost of launching something into orbit repeatedly (as well as bragging rights). Discarding stages is almost always destroying them, and parts cost funds. I will cover returning back to Kerbin from orbit in an SSTO. I will also cover how to slim down your plane (which will usually make it more aerodynamic) and how to use the right engine. Another thing I will cover, is the proper (well, mostly proper) way of getting into a orbit. This proper way can be generalized, If you have a lower Thrust to Weight Ratio (TWR), it’s better to pack some extra fuel to get up there, or find ways to lighten it. You can always have a lower rate of climb as well, if it turns out the plane is incapable of doing a high angle climb, just note that you also need more fuel as a result. Also of note: HEAVIER PLANES NEED BIGGER AND/OR MORE WHEELS, AND THIS WILL SLIGHTLY AFFECT TWR
Making your plane work better at high altitudes
This section is going to cover how to make your plane more aerodynamic and stable, and how much DeltaV and thrust to weight you really should have.
So, the IDEA of making a plane aerodynamic is to reduce any drag you have. The ideas are mostly as follows. (Note that some of these apply more for Ferram Aerospace Research [FAR] more than stock KSP.)
- Make anything external that DOESN’T affect flight/lift but does affect drag fit inside a cargo bay if possible. Unless it’s your airbrakes or radiation panels. (Note that radiation panels are pretty much useless unless you plan on going closer to the sun.)
- Don’t make your wings straight perpendicular to forward velocity, angle them back. Use swept wings, delta wings, or the structural triangular wings (preferably the ones that attach by the long side). Note that doing so may cause you to lose a bit of lift relative to if the wings were perpendicular, but that’s a sacrifice you have to make for speed.
- Try to make the plane as stable as possible by putting the center of lift a little bit behind the center of mass. If you are still unstable, angle or raise one of the pairs of wings a little and make it so that your lift is higher than the center of mass. By angling the wings you will also induce a roll stability affect where the wing will have a slight tendency to level out. Probably.
- Make anything poking out (that isn’t the wings) line up with the rest of the plane as much as possible, or put it in the aforementioned cargo bay.
- When you get into space, don’t worry about electricity if you have RCS, you should be fine. Unless you’re using a life support mod. This also brings up a good point about atmospheric flight, when you are returning, do not worry if you run out of power, as your control surfaces still work.
- One last thing to note that you can potentially skip is that part clipping can be justified, but it only makes it harder for you to select said part mid-flight. And it’ll probably still be something that causes drag regardless of how you clip it unless it’s either in a cargo bay or you’re using FAR.
Making use of what you have
I will be covering what engines you should use or -at the least- how you should utilize them to your maximum potential.
If you haven’t caught on by now, a SSTO is a balancing act between how the fuel gets used all throughout the aircraft, the stability of flight, TWR, and the DeltaV. A trick to get this stability is to design the body around the engines and fuel, with the wings coming last, as they don’t affect the weight too badly, unless you are doing a larger SSTO. And you’ll probably be moving the wings around anyways trying to find a balance for the CoM and CoL.
As for engine choice, I recommend you use the Toroidal/Whiplash, or Rapier/Nerv or the Whiplash/Nerv. but if you’re trying to go Mk3 fuselage big, you’re free to experiment. Note that these combinations will result in vastly different TWR capabilities. I’m unsure how I feel about the Panther but it seems more like it’s meant for repeatedly breaking mach, rather than a one-off like this.
On that note I do recommend that you use a Mk2 fuselage if you are doing a cargo and passenger runs, but if you are just in it for the science, feel free to use a Mk1 fuselage, as the Mk2 really only provides body lift. If you need more power out of the engines at high altitude, feel free to put in some air intakes, and if that isn’t enough, try messing with how much liquid fuel you take up. A reliable way for the last bit is to take the full fuel up that you will use, and when in orbit, see how much fuel you didn’t use and subtract that from the fuel in the SPH.
In general, pack plenty of fuel for your needs, make it so that it is as light as you can get it, and keep it as aerodynamic as possible.
The proper way to climb into space
If you are successful with aerodynamics and lift, this is the proper way to climb into space.
You should begin, if possible, at a 45-50 degree climb from the runway. It is also possible -should your TWR be lower- to climb at a shallower angle. Just remember to pack more fuel and watch your speed. Drag and fuel use increase exponentially the faster you go up until a certain point. That point usually being when you have passed mach 1.4, and are at higher altitudes respectively. When you reach 10km up, level out to 5-10 degrees and speed up as fast as possible. when you have reached your maximum speed, slowly pull up to 45 degrees, and when you’re about to lose your air-breathing engines, cut them off and use the rockets. if you have made it to 70+ km up in apoapsis, try not to use any more fuel than needed to keep that altitude. The air may still be around to drag you a little, and that will take down your apoapsis more the higher you project your flight. This is a waste of resources. If possible, circularize in a 20 second window -10 seconds before and after- reaching the apoapsis.
If you have done everything correctly, you SHOULD be in orbit with some fuel to spare. Do what you want (dock to something, float around, or just cheer that you made it into orbit) for your time, and then burn retrograde. If you want to make it back to KSC, make it so that your flight path looks like it is going to fly over KSC, and get to the thicker parts of the atmosphere above KSC. I would recommend aiming for a certain part of the ocean relative to the islands but it’s dependent on angle of entry. During reentry, you must attempt to shuffle your aircraft around as much as possible and cut any throttle to stop your speed. If you have airbrakes, attempt to use them but try not to burn them off. Land and then cheer that your flight was a success. If you have done this correctly, you should have made it back to KSC in one piece.
Thank you for reading this and I hope that you are successful in your endeavors!