SSTO video tutorial?

[GrihanOs]

Hi,

Can you point me to a good SSTO/Space plane video tutorial?

Thanks.

[bewing]

For how to build one? How to get one into orbit? Or how to deorbit one?

[GrihanOs]

Mainly for orbiting and deorbiting.

[OrbitalBuzzsaw]

@Matt Lowne's youtube channel has a Minmus SSTO tutorial that's pretty good

[AeroGav]

Can cover the re-entry part 

 

The basics - in a capsule return, you stay on prograde (or retrograde) so your heatshield points directly into the oncoming blowtorch and keeps your pod out of the line of fire.   Spaceplane is the opposite, you pitch up a bit so make a bit of lift or drag.  Lift keeps you out of the thickest atmosphere till you've really slowed down, drag, well, slows you down so there is less heat.   There's a lot of argument about the finer points of technique, some people say pitch up as much as possible for maximum drag, i say go for a moderate high lift position.   In this video, shot in 1.0.5,  i open the cargo bay and lower landing gear for more drag.   Not sure if that makes sense in 1.1.12 but we'll see.     It might be a good idea to use inline cockpits so the bit with the crew isn't the hottest part of the ship.   Consider putting a heat shield between the nose cone and the cockpit - it won't get ablated or create any drag in normal use,  but if you do come in too hot and burn off the nose cone, the heat shield starts to do its thing and save the ship.   Finally if you really want to go health and safety on us you could put a chute in the cargo bay, in case the wings melt.   Can be quite a small one,  since especially with gear down etc. the cockpit of a spaceplane will survive quite high ground impacts.

Also,  i'd generally use a higher periapsis for re-entry of an SSTO, since they are more fragile.   The drawback is, less accurate landing point, however that's not such a problem in a spaceplane as they have greater ability to glide/fly back to the space centre than something coming down on a parachute.

 

I'll stop being such a lazy ####  and upload an ascent video i shot of a recent design that i put on KerbalX.

[AeroGav]

Basic rules 

1.  Fuselage size - small diameter is best.

Stick with mark 1 fuselages if at all possible, they have so much less drag and weight.   If the ship becomes too long and bendy with mk1, and a shorter, fatter type 2 fuselage will fit the same number of kerbals, or if you absolutely need a mark 2 cargo bay, only then consider type 2+.

2.  Parallel fuselages - minimise frontal area

This is closely tied in to the number of engines you are going to support.   If you are building under 25 tons and are planning to use fuel and oxidizer, then you need only one engine (a RAPIER)  and it can be at the tail end of your only fuselage section.  No need for sponsons, engine pods, parallel fuselages or whatever to add frontal area.   

If, like me, you are building an oxidizer-free long range spaceplane that flies to orbit on a combination of air breathing engine and nuclear rocket,  you're basically forced to have at least 3 parallel fuselages - two for the LV-N strapped to the sides, one for the airbreather.

3.  Minimise radially attached  rubbish

Weight is easier to tolerate than drag.   Use reaction wheels insdead of thruster blocks, put stuff (solar panels)  in service bays if you can.  In line clamp o trons only.   Don't add more air intakes than you need. Avoid fuel ducts and struts, they are bugged and add horrific amounts of drag.

4.   Don't mount too many engines

One air breather per 30 tons is fine.    60KN of closed cycle thrust (one LV-N or one Terrier) is enough to put 15 tons in orbit.  Engines are very heavy and add substantially to your empty weight, they can quickly cut down your delta V.

5.  Don't be too stingy with wings

Look out for the ones that can double up as fuel tanks (big s strakes, big s shuttle delta wings, fat 455 airplane wing).   These are especially handy if you're making an oxidizer-free nuke/jet engine ship like mine since you need all the liquid fuel capacity you can get.

Above 20KM, air is very thin and if your wings are under sized you may need to use Angle of Attack > 10 degrees to get enough lift.  Over 10 degrees angle of attack drag goes up very quickly.  Matters less i guess if you have a very powerful oxidizer using rocket engine to get you past that awkward moment when you're no longer  a very good airplane but not yet a space ship.   On a nuke powered spaceplane however, it is important to keep drag down here so you can still accelerate with these weak engines, you also need to gain height at sufficient rate as you accelerate, to not overheat.  This all means plenty of wing.

-------------------------------------------------------------

https://kerbalx.com/AeroGav/Astrojet-Citation

This is a 30 ton, one whiplash two NERV SSTO with the ability to take 5 kerbals and a docking port to Minmus.  Can also fly to Duna, land safely and go back to orbit again , but doesn't quite have enough for the transfer burn back to Kerbin unless refuelled.

Part one of my launch video.

 

The craft flies without any mods but Mechjeb makes it possible to fly climb angles accurate to within 1 degree , which saves a lot of effort and allows you to experiment with different profiles in a repeatable way.

Note how i've got mechjeb configured on the left.   Whatever i input in the "pitch" box is the AoA the autopilot will hold.   On the right aero data window, at the top of the third section,  see how closely AoA matches the "PIT" setting on Mechjeb . 

Six lines down you have "Total Drag" and "Lift Drag Ratio".  Throughout the flight i'm adjusting these to try keep Lift Drag Ratio as favourable as possible.    Four lines up from bottom, is "Thrust".  Notice how this compares with "Total Drag" as engines come on and offline, and move in and out of their sweet spots !

Edit - part two here, where we finally max out the little old airbreathing jet and light up the nukes.

 

Edited May 14, 2016 by AeroGav

[GrihanOs]

Thank you all for your answers. They were  very useful.  

[AeroGav]

1 hour ago, GrihanOs said:

Thank you all for your answers. They were  very useful.  

At this point I'll also shout out to my favourite mods for space plane building -

Almost Indispensible  (really not cheating)

GPOSpeedFuelPump  - if only using RAPIER, you won't need this.  Otherwise however it solves the problem of rocket engines not seeing wing tanks, and draining fuel unevenly from the front first, destabilizing your ship

Mechjeb - see the video for details.  Makes life easier.

Very Useful (not really cheating)

ModularFuelTanks -  allows you to alter the ratio of liquid fuel and oxidizer, or even change to LF only.  Want to keep Monoprop  in your Big S spaceplane wings? You can !  Want to change a large 2.5m rocket fuel tank to hold only liquid fuel or xenon - done ! Same with the mark 2 to 1 and 3 adapters and bicouplers that are only available in rocket fuel format - swap these over to LF only and not waste any tank space.

Useful (a little more dubious)

The after fuel, the next problem you have is one of not having parts the right size for what you need to build - planes are finicky about this. Wings and control surfaces are often too small for our needs, while engines are often too big and heavy for smaller craft.

You've basically got 3 choices -

KerbalJointReinforcement - allows you to put together lots of smaller wing segments to make your own custom wings, without stuff getting too floppy. You could argue this is an unfair advantage, in some situations though.

B9 Aerospace Procedural Parts Fork - Has procedural wings and control surfaces.  Choose the exact span, width and sweep angle you want !  Can look good if you take a lot of care, keeps part count and number of floppy joints to a minimum.  Can look a bit non-stock and "low polygon" if you're not careful. I'd say this is a pretty fair mod, you're not using anything OP,  just something that's the right size for what you're making.

Tweakscale  - upscale or downscale stock parts.  Want a pair of jettisonable Whiplashes in underwing pods for your little mark 1, but the stock ones are too big and heavy? shrink them to Juno size !  Should be ok, but the results sometimes look wierd.  Shrinking engines, wings or fuel tanks is ok, their stats scale with size.  Shrinking crew pods, science labs, etc. while still having them function the same is a cheat however !

Edited May 15, 2016 by AeroGav