SSTO, Why u no fly?

[Zeenobit]

I was having similar issues to yours not long ago. You can look at this thread for the full story:

http://forum.kerbalspaceprogram.com/threads/99982-SSTO-FAR-Deadly-Reentry-Help

There is a few things I learned that might be useful to you:

1. Piloting is somewhat more important than design.

2. Have faith in your aircraft. If built correctly, it can usually take a lot more punishment that you probably think. Trust it.

3. Keeping above in mind, don't be in a rush to climb up into upper atmosphere. Turn on precision controls, adjust your trim, sit back, and just enjoy the scenery. With my aircraft in the link above, the ascent into upper atmosphere happens in a "staircase" pattern: I climb, lose speed, aircraft nose pitches down, I gain speed, lose altitude, aircraft nose pitches up, I lose speed, gain altitude, so on and so forth. Before, I used to panic every time the nose pitched down. All I had to do was let go of the controls. My point is, don't try to over-control the aircraft. Let it fly. I almost exclusively fly with trim controls now.

4. Again, don't be in a rush to climb the atmosphere. Take it slow. You want to pick up as much speed as you can with the jet engines. Remember: Getting into orbit isn't about how high you are. It's about how fast you're going.

5. If you're not using RAPIERS, make sure, and make doubly sure that your engines are lined up. What I mean by this is, in the Editor, turn on the Center of Thrust marker. Reduce the Thrust Limiter on one set of the engines to 0. The CoT should NOT move. Repeat the same with the other set. If CoT moves, you may induce unwanted torque to the aircraft when you pitch, which can be catastrophic. Adjust these until the CoT does not move.

6. In order to minimize the effects of sudden change in thrust, throttle down as much as you can (don't flame-out the jets if you have more than one. This may create a change in yaw if one flames out before the other, and you won't go to space that day). Then switch to rockets. Then slowly throttle back up.

I hope these help! I know how frustrating it can be to get that thing into orbit, but keep trying!

[capi3101]

I generally point spaceplane newbs to two places - Keptin's Basic Aircraft Design Explained - Simply with Pictures post (a great place to begin) and to DocMoriarty's KSP Space Plane Construction and Operation Guide (a great place for specifics and ideas on what exactly you can do with planes). DocMoriarty's guide focuses on use of the RAPIER engine. It's slightly out of date (by slightly I mean it was designed for 0.24.2 and he hasn't yet updated it for the changes in 0.25/0.90), but so far the only thing I've seen that's major is that the new Wing Connectors are functionally equivalent to Delta Wings. Shock Cone Intakes are equivalent to 1.2 Ram Intakes and 4 of the new Structural Intakes are roughly equivalent to a single Shock Cone Intake.

As far as specific numbers go -

- your maximum take-off weight per engine is 10 tonnes if you use Basic Jet Engines, 13 if you go with RAPIERs and 15 with Turbojets.

- your total lift rating (i.e. the sum of the lift ratings of all horizontal lift-generating parts) should be roughly equal to your mass. 1.15 tonnes:1 lift is an acceptable ratio, 1:1 is easier to remember.

- the total intake area of all intakes should be no less than .035 per engine if you want to make space. A greater amount of intake area should allow you to achieve a higher atmospheric flight ceiling.

- Total liquid fuel should be roughly 40 times the plane's mass in total fuel units, total oxidizer should be about 25 times the plane's mass in total number of units. Count any fuel to be used for interlunar/interplanetary flight among the craft's payload.

- Assume a low-end payload fraction of 25% if using the plane as a payload booster.

That should hopefully get you started. Flight profile is equally important. Folks will tell you to get to 10k as quickly as you can if you're using stock aerodynamics (like me). After you're at 10k, you can start flattening out; pitch down to about 20 degrees above the horizon and just let 'er fly. Speed benchmarks as follows - 350@11k, 450@14k, 650@16k, 850@19k, and 1300@23k. In general, you want your ascent past 10k to be no greater than 100 m/s (as per the rate of ascent indicator right besides the altimeter). Past 20k, you want that even lower - say, no more than 20 m/s or so. If you're flying a multiple-engine craft and it starts pulling to one side after 25k, throttle back a bit. You want to keep accelerating on just your jets for as long as you can (if you use RAPIERs, be sure to set an action group that will allow you to toggle them between modes, and be willing to switch back to air-breathing mode if they switch over before you've picked up enough speed). When you have to throttle back and no longer accelerate, that's the time to light your rockets. You then shut off your jets, close your intakes, pitch up to about 40-45 degrees and fly like hell until your apoapsis is where you want it. Kill the burn - at that point your plane is a rocket, and should be treated as such.

Hopefully that'll get you started. Folks have given you some good advice on this thread already; be willing to experiment a bit to see whose advice best fits your style of play.

Edited March 27, 2015 by capi3101

[GamerMitch]

thanks capi3101, That was very in depth, and the threads were helpful too. Thanks to all who have considered this and decided to help me out. I actually made it on a sub-orbital trajectory 1/4 the way around Kerbin just yesterday!

[Laie]

Step 2: Build a turbojet powered aircraft that can reach 29KM altitude and 2,000 M/sec and return safely to KSC

Slashy,

I've been able to get to step 2, It's just the gap-bridging part that kills me. I try to add rocket engines and fuel, but they add too much weight.

If you can get to 2000m/s, you no longer need very much rocket power. Almost none at all, truth be told. A tiny engine (that 30kN rockomax thingy, for example) will do, and you won't need more than 300m/s of rocket fuel. Chances are that you can make do with less than 100m/s.

Once you reach/get close to 2000m/s, just try to maintain that speed and get back to climbing. Not too fast, but definitely climbing. You'll have ever less air for your jets, but you'll also have ever less drag to fight against. So just throttle down to keep your engine from dying. As long as you can maintain a "surface speed" of about 2000m/s, all will be well -- no need to get much faster. By the time you reach 40-50km, a miniscule amount of thrust will suffice to keep you going (just look an Wanderfound's throttle in the picture above). A plane that can reach 2000m/s will also be able to take you much further.

[Wanderfound]

A demo of how little rocketry is required:

[deepspacecreeper]

Check out my thread, my first and only successful spaceplane (not rly ssto, check out to see why). 2t to Kerbin orbit or 5 passengers (not counting pilot Jebediah).

[Redshift OTF]

Show us a picture of your plane and we can see where you are going wrong. Sometimes it is just one thing that is holding you back. When you get your first SSTO into orbit all comes down to optimisation from that point on to make even better planes with better performance, distance and aesthetics.

[GamerMitch]

BREAKING NEWS

At Precisely 7:01 AM CST this morning, November 17, My SSTO made it to a 70x135 km orbit with fuel to spare. Amazing, right? Thanks to all of you who took time to offer your advice to me on this topic. I will continue to improve at SSTOs, thanks to you guys. Screenie!

[OgreMagi]

my sstos typically run between 6 to 12 tons, I use one tubo jet with 2 shock intakes and a couple rock max 48=7s ( to 30 Kn ones) I have the Kommet Nucleonics mod with the small nuke engine ( 0.5 tons and 12Kn thrust) for my interplanetary sstos

basic concept is build a jet, balance it first so it can make stable flight without SAS, not really necessary but it helps.

then build a turbo jet variant, balance it ( the lift/mass/thrust markers ) then get it up as high and fast as you can.

then add a few rockets as said previously said you don't need much rocket thrust, usually less then 500 M/s DV to make orbit and land...

one of my earlier designs using the shuttle cockpit. just under 12 tons, makes a slow climb to make orbit.

and the updated one, note I do not fill the tanks full, to keep the weight down.

Edited November 18, 2014 by OgreMagi

[GoSlash27]

BREAKING NEWS

At Precisely 7:01 AM CST this morning, November 17, My SSTO made it to a 70x135 km orbit with fuel to spare. Amazing, right? Thanks to all of you who took time to offer your advice to me on this topic. I will continue to improve at SSTOs, thanks to you guys. Screenie!

http://i.imgur.com/e22mgol.png

Congrats!

Getting it done the first time is the hard part. It should be a lot easier for you now.

Best,

-Slashy

[Vegvisir]

This, and several others, have been pretty useful threads to read through. But I'm still unable to crack it! It seems my craft doesn't get enough speed, or air, or altitude, or all of the above.

Maybe some of you spaceplane aces could offer any advice?

​

On a functional level...

It's 20.8 tonnes. 2x jet engines, and 1x Thud (tried a Terrier, thought it was not enough). 28(?) intakes, most of which are either the Structural or Radial kind. Dunno how people get more than a couple of Rams on their planes (could use the other MK2 cockpit and +1 more intake I suppose).

880 LF (in 1x MK2 and 2x nacelles). 270 LF+230 Ox (1x MK2 tank and 2x of the little T100s).

It's fair to say I haven't calculated it all out, in terms of how much fuel and everything else. I've had lots of goes and decided after some attempts if it seemed too much or not enough. Science!

I was aiming for this:

Speed benchmarks as follows - 350@11k, 450@14k, 650@16k, 850@19k, and 1300@23k

and (haha) tried lots of times, but had surface speed displayed. Everyone talks about orbit speed, right? Well. I changed display to that and it seemed a better go. However, like most other times I still get to that 20K point and 1000m/s or more is a struggle. Which is recognised as that tipping point between jets and rockets, right? Knowing when to turn on the rocket is tough to get right, though. I see jet thrust drop fairly early-ish, which is when people say to ignite rockets, but at what point...100?...50?...75? The rocket seems to do ok, speed will start to increase slowly. But only if I keep ascent at like 20deg. Then sooner or later I run out of fuel - and adding more fuel = more mass = no better off. It's frustrating, I really want to get it

[Starhawk]

@Doslidnyk

This thread contains info about the old versions.

Everything has changed since 1.0 was released. Air-hogging is a thing of the past. One shock cone intake or ram intake per engine is plenty. I don't use the structural intakes at all since they seem way too draggy - YMMV.

Those speed benchmarks are also useless in the current version of the game, as are the flight profiles in this thread. The new atmosphere in 1.0 demands a complete rework of spaceplane design and flight profile.

Please read some of the more recent threads such as the Pro SSTO Builder/Pilot thread or the newer entries in the K-Prize thread.

Those should put you on the right track.

Happy landings!

Edited August 13, 2015 by Starhawk

[selfish_meme]

Haha necroed, I was reading thinking this is the worst advice I have ever read!

[capi3101]

Yeah, forget this thread existed, unless you're being nostalgic and whipping out anything from 0.9 on back. Might recommend the admins lock the thread, purdy-please.

[Red Iron Crown]

That's not a bad idea, new players might see the thread and think it contains current information. Locked.