How to build a successful SSTO?

[Zeratul]

I have been playing KSP for about 6 months now and I love the game very much. I play for weeks, stop for awhile, and then jump right back into it full throttle. I have been building a large space station that sits at an alt. of 100k above Kerbin. I am pretty good at building rockets, but I have not tried building a single spaceplane or SSTO.

Im not sure I even know how to fly one correctly. Any ideas?

[allmhuran]

Turbojets and plenty of ram air intakes. Get up as high as possible and level out on the jets, picking up speed and reducing throttle as you go so your engine(s) don't flame out. You should be able to get to 30000m+ @ 2000m/s or more. From there, it's just a little rocket-assisted squirt into orbit.

Also, have some rep for the username.

Edited October 14, 2013 by allmhuran

[Sirine]

It depends on your definition of "successful". The basic stock craft Aeries 4A could classify as SSTO too.

To fly one SSTO, for the basic (NOT ALL), you just fly it HIGH, and FAST, before you switch on the rocket engines to push you to Kerbin Orbit.

Normally a standard SSTO get to 1600m/s in speed, and 20~30km before switching to rocket engines.

Some SSTO gets to 2350m/s (Orbit speed), for few seconds and just a little push of small rockets get its to orbit.

Example the "Frak-I" <---search for it.

[AnalogAddict]

Hey, take a look at this post and video. The video goes to orbit 3 times so you should be able to work up a valid flight path.

There is some valuable information on flying SSTOs, tips, tricks, plus a couple DLs for working planes.

http://forum.kerbalspaceprogram.com/threads/44759-Nobunaga-Interceptor-quick-agile-spaceplane

[lammatt]

a quick tip is:

2 turbojets + 1rocket engine (the one with 215kN thrust)

on 1 long 1.25m fuel+oxidizer tank+ the mk1fuselage with fuel at the middle and 2x 1.25 fuel+oxidizer on the side with fuel duct to the middle stack;

with ~2ram intake +4 radial intakes, you will be able to fly up to ~mach4 to5 at~20km altitude and the jets can live till ~25km

----

otherwise, you want to squeeze as much jet thrust as you can in a reasonably weight, if you manage to get to mach 5 @25km before the jet dies and you have >1.5km/s of vacuum rocket dv to spend, you are very likely getting to space unless something goes wrong.

[arq]

With enough wing area and the right fuel load, 1-2 turbojets with 3-4 intakes per jet, plus a LV-T30 should get you to orbit if you want a basic SSTO. Most of my larger SSTOs use these same ratios of jets/rockets. But smaller ones can be made with a single jet, 3-4 intakes, and 2 LV-909s or even two rockomax 48-7S's.

As you may have found with staged rockets, less is sometimes more. This is even more true for SSTOs. A staged rocket can always get further by simply putting the whole rocket on top of a bigger rocket. An SSTO carries all of its mass forever (unless you strictly mean 'to orbit' and then drop stuff), so without refueling their range is hard-limited by the performance of the parts available. So bigger is nearly identical in performance, at best, but often is actually worse due to other inefficiencies, especially with new players.

SSTOs can be made arbitrarily simple by adding intakes, so if you really just want to get one up use 6+ intakes per engine and it should be (comparatively) easy. I usually find 3 to be plenty, but I have a bit of experience. Unless you are airhogging you will not reach 30km on jets alone. With 3ish I usually top out around 24-27km, going between 1300 and 1500m/s.

[Kosmo-not]

It takes a rocket ~4500 m/s to get to orbit. For a SSTO, you just need to have that much dV in the first stage. Below is an example of a simple SSTO.

[Hodo]

Arq, is dead right.

You can build a space plane type SSTO with 3:1 intake to jet ratio. The turbo jets are the best for this role and do quite well in atmosphere and handle mach 3.5 and better the best. I use FAR so I can't tell you much about the stock drag model or how it works because I have never dealt with it for any length of time. But you will want your wings to be pretty simple in construction or at least strutted so they don't flex to much. And you don't want to try go and fly it like a rocket, SSTOs take a bit longer to get to space than a rocket. But they can get to space generally with more fuel if done right.

[Starglider]

Tip #1: Weight is not your friend. A heavier plane flies lower, encounters more drag, and has a lower top speed. My first SSTO actually decoupled the landing gear and parachuted back to Kerbin because the landing gear was so heavy.

Tip #2: Start small: one turbojet to get your initial speed up and shoot your plane into space, and a pair of Rockomax Radial Rockets to finish up your orbit. One radial would work fine, but then you have unbalanced thrust.

Tip #3: Bring only the fuel you need: one mk1 fuselage for jet fuel, and a FLT100 for rocket fuel (that's right, the small one - you don't need much). You'll probably have enough fuel left over to make a powered landing at KSC.

Tip #4: Drag is not your friend either. While weight causes drag, so do wings. Yet you need wings for lift. You will need to find a balance, but for a really small plane, a pair of delta wings, a pair of small control surfaces on the delta wings, and a pair of forward canards should be sufficient.

Tip #5: Rudders work best in pairs. I've seen some strange yawing action when using one, that seems to be canceled out when using two.

Tip #6: For your first SSTO, airhog to the max. Many find it objectionable, but your first attempt needs a large margin for error, and having a couple dozen ram air intakes for that one turbojet gives you that that margin for error. Once you're used to how things work, feel free to tone it down.

Tip #7: Start with getting a stable airframe that you can easily fly. Part of this is in design (CoM should always be in front of CoL; be aware CoM shifts around during flight so compensate for the shifting), but part of it is in flight testing before you send it into space.

Tip #8: Practice your landings. Nothing hurts quite so much as to have a completely successful mission, before your plane crashes on landing.

[capi3101]

Kosmo-not makes a good point: "SSTO" is not synonymous with "spaceplane", and you can build an SSTO rocket easily. To design one, assume your payload fraction is about 4% of your rocket's total mass and plan your engines accordingly (a launch TWR of 1.2 is good for an SSTO rocket). You then take the mass of the engines and add it to that of your payload; you get the constant "deadweight" of your rocket, leaving just the fuel tank mass as the only bit you need to determine in Tsiolkovsky. Most fuel tanks in KSP weigh nine times as much full as they do when they're empty. You work Tsiolkovsky backwards and with that information figure out how much fuel you need for the 4550, and then put everything together in the VAB. Simple stuff, really.

The flight profile is just like any other launch: straight up to 10k, 45 degrees at 090 to 25k, then follow the prograde marker on the navball. Keep your gee meter in the green; that means throttling down as you go - expect to make your orbital insertion burn at one-third throttle. When you're up, cut it loose.

Practical payload limit for an SSTO rocket is 45 tonnes - by practical, I mean "as much as you can expect to lift with nine Mainsails". You can try to lift more, but construction is going to be much trickier.

Spaceplanes, I can't help you with the design; trying to figure those out myself and not diligently. From what I understand, though, you want to head up to about 25,000 and go horizontal (may be higher; a high as you can go without flaming out the engines). Say on your jets and pick up speed (though watch your throttle so you don't flame out). When you've got orbital velocity, kick in your rocket and give yourself a push upwards.

[SRV Ron]

Small SSTO, 1.2 ton launch weight, 0.3 tons in orbit. (Novapunch Mods.)

[capi3101]

Big SSTO - 24 tonnes payload, about 600 give or take total. Stock. Designed for a three Kerbal flyby of Moho.

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(Learned later I could've assigned a three Kerbal crew from the VAB; only problem with this album. I should fix it).