SSTO's no matter what I do I always fail.

[genericeventhandler]

I've downloaded and tried to design a number of SSTO's, I've managed to get one of my own into a 71-75 orbit with zero fuel remaining.

All the ones I've downloaded and tried and the others I've made all fail to reach orbit.

I'm using stock aero, and normal re-entry.

Most of the ones I have seen say fly to 18 alt, pick up speed and then pitch up.

When I do this it either fails by.

1. Can't reach 18 alt, air intake is not sufficient to get much above 15km, or lift won't take me that far.

2. Getting up to speed burns through all the liquid fuel and into the rocket stages supply.

3. With rapiers I can get up to 1,500 ish speed at 18 alt, but the moment I pitch up it drops to 500, and I'm basically an underpowered rocket.

I downloaded an SSTO Training plane, the notes said pitch up to 25 degrees, when the speed starts to drop switch to rockets. That one barely got to 50 km in altitude.

What am I doing wrong?

Thanks

Edited September 11, 2015 by genericeventhandler

[capi3101]

Hazarding a guess, you may be downloading craft from the pre-1.0 era, when the aero model was vastly different. Look at post date of the craft you're downloading - if the date is prior to April 27, 2015, the craft is probably no good. Unless you're using an older version of KSP, of course.

And if the plane is newer, then you need to look at your ascent profile. These days, the standard flight profile is to get to 10,000 meters as fast as possible, level out in the 10-15k regime and pick up as much speed as you can without 'sploding, then pitch up once you're going no slower than 1000 m/s, lighting the rockets somewhere in the 15-25k regime (with speed the primary consideration). Typically a plane needs 1,800 m/s during the rocket phase to reach orbit, fart around a bit up there, and return safely with stock air.

[Val]

...

With rapiers I can get up to 1,500 ish speed at 18 alt, but the moment I pitch up it drops to 500, and I'm basically an underpowered rocket.

I downloaded an SSTO Training plane, the notes said pitch up to 25 degrees, when the speed starts to drop switch to rockets. That one barely got to 50 km in altitude.

What am I doing wrong?

Thanks

That's a lot of pitching up. I don't pitch up more than 10-15 degrees. And I do it at lower altitude and speed. And very slowly so I don't lose speed.

If you're up for another try, I posted a SSTO with instructions here.

[Scarecrow88]

Try this one, it has enough fuel to get to a 350km orbit, so a 75km orbit shouldn't be too difficult. I usually fly it initially at about 30 degrees, lowering it slightly to stay on the prograde vector as it climbs. Once I get to 10,000 drop to 10 degrees nose up, and stay there. Speed should reach 1300 - 1400 m/s by the time you get to 21,000m or so. You will hear the engines start to tail off, and the acceleration start to slow at this point, so use action group key 1 to change to closed cycle mode and just ride the acceleration until your apo hits 85 - 90k. No need to pitch up. The apo will drop slightly while you are coasting due to losses whilst still being in the atmosphere, but once you near apo, just make sure you are pointing prograde and burn to circularise. Job done.

For coming back down, just make sure the airbrakes are deployed before you hit atmo, action group key 2, and just stay close to prograde. Remember to switch back to air breathing mode, action group key 1 again, in case you need to fly any distance to your intended landing point.

Craft download file

Kiter SSTO

Docked to station orbiting at 350km

Back on Kerbin

[Val]

Hazarding a guess, you may be downloading craft from the pre-1.0 era, when the aero model was vastly different. Look at post date of the craft you're downloading - if the date is prior to April 27, 2015, the craft is probably no good. Unless you're using an older version of KSP, of course.

...

Good point. I didn't think of that.

[crestofawave]

i use 2 rapiers and 2 whiplashes, it auto takes off because of the angle of my undercarriage, fly a steady 20deg angle all the way up, auto switchover on the rapiers, i find using canards at the front will help you a lot if your unsure with lift/control

[Kosmo-not]

Try this SSTO

[Warzouz]

No : this is a SSTO ! (600T payload and it's recoverable)

More seriously, designing SSTO space plane is not that easy. As they aren't very scalable you find yourself in need of changing the whole design just because you can't add a few tons.

It took me quite a long time to get my first one right. I'm working on a small one for now.

- Add a inligne cockpit

- Add a shock cone in front

- Add a big and medium 1.25 rocket fuel tank,

- Add BigS wing and fuel them.

- Add elevons on the wings

- Add a tail fin.

- Add one rapier.

- Add 3 wheels

- Add front canard if you need more control

You should get a very stable plane that goes to space (wings are too big though). You must tweak wings positions and elevons to get proper control and balance.

- Takeoff

- Climb 10° until speed is 250m/s

- Climb steeper, keeping your speed constant up to 10km

- Follow prograde and wait to cross 10°, swap to SAS

- Let your speed increases frmo 300 to 1200/1400 (the faster the better)

- You should try to climb slowly by locking SAS. Ideally, you should get to 20km at 1400m/s

- Swap Rapier to close cycle mode when you speed starts to stall. The higer the better but don't let go your speed down.

- Then continue up to 35km, then follow prograde (your AP should at 75km very soon)

- You should circularize with fuel left.

When your plane goes to space, you can start adding stuff (energy production, airbrakes, docking...) to manage other operations. Again adjust other parts and test again.

[genericeventhandler]

Thanks all, it seams that I was following the flight profile for pre 1.0, with post 1.0 craft. I'll definitely give it a go tonight, and I'll try all your wonderful craft files

[Nothalogh]

My ascent profile goes as follows:

1 Go supersonic shortly after takeoff

2 Pitch up into a 25° to 30° climb and maintain about Mach 1.1 to 1.5

3 At about 7 to 10km, pitch down until your prograde marker is at 15°

4 Set throttle to full, and hang on to your buttcheeks

5 You will breach 19km at well over 1200m/s

5 Engage rockets or switch mode on your rapiers

6 Pitch up to 20° and burn until AP reaches target

[genericeventhandler]

Thanks all,

over the weekend I built my first successful SSTO plane.

2x Ram intakes, 2x rapiers and 2x Whiplash on a MK2 plane with 1.25 rockets strapped to the sides, Big Plane wings filled with fuel and Cannards to help with lift balancing.

My ascent profile,

1. Pitch up to 5 degrees and lip off the end of the runway,

2. When the gear is up, pitch up to 25 degrees.

3. At 10km pitch down slowly to 15 degrees.

4. When the speed gets to mach 2.7, or you start burning. Pitch back up to 25 degrees (slowly)

5. At the first flame out, change the rapiers over to closed loop. This should give you air up to 20km for the other two engines.

6. Close down the air breathers when they flame out and close the intakes.

7. 25 degrees all the way to orbit.

Things I did wrong.

• Too many intakes, the drag was keeping my velocity down.
  
• Not enough power on the climb from the runway, if it can't do 25 degrees sustainable, you need more air-breathers and less drag.
  
• Pitching up/down too soon and too fast.
  
• Too many things attached to the hull, was causing too much drag. Use spot placement RCS.
  
• Hide solar panels inside the cargo hold.
  
• 10km is where you pick up speed, not 18km (pre patch 1 I presume)
  
• Mach 4 at 10km makes things more streamlined, air brakes explode at that speed.
  
• Too much roll / pitch control is a bad thing. Deactivate flaps after takeoff and only use one set to pitch.