1.0.3 SSTO tips for the returning player

[Bishop149]

As the title basically

Had my first serious attempt at an SSTO in 1.0.x yesterday.

My basic strategy was unchanged from when I did it in older versions of KSP high and fast as possible on Turbojets, before pitching up and firing the rockets.

This turned out to be about 1,100 m/s [surface] at around 20-23km up and I initially woefully under estimated the quite substantial rocket power that was then required for the last step on the 1st few attempts. Eventually however got one to orbit on two turbojets and two aerospikes

Back when I last did an SSTO (probably 0.24.2) I could do substantially better than that. . . turbojets used to top out at about 30-35km at ~1,600 m/s [surface].

Now obviously I realize the aerodynamic model has changed substantially but just wanted to get a feeling for if its only down to that or if I'm doing something wrong now. Also had a quick look around at recent SSTO pics posted here and almost without exception they all use the rapier engines . . . . which I've not unlocked yet. Is a nice efficient SSTO lifter now basically impossible without this fancy tech?

Best I managed after some brief playing about with turbojets and aerospikes was a nearly 60 ton craft (4xTurboJets and 4xAerospikes) to lift a 10 ton payload to orbit . . . . just barely!

Any tips appreciated.

Edit: Oops meant 1.0.4! Ignore mistake in title!

Edited August 11, 2015 by Bishop149

[Red Iron Crown]

Turbojets for SSTOs are perfectly viable, you just need more fuel for the rocket portion of the ascent since they can't go as fast as Rapiers.

The new aero model makes it critical to minimize the frontal area of your craft, have no more than one stack per engine and leave none of the nodes open. Use as few radially attached parts as possible, including struts and fuel lines, they are draggy.

Don't bother with pre-1.0 style airhogging, it no longer works and adds unneeded mass and drag. One ram intake or shock cone per air-breathing engine is plenty.

Also, you should upgrade to 1.0.4.

[Pecan]

The latest version of KSP is 1.0.4

The simplest manned SSTO I have is - Mk1 pod and parachute, 2 x FL-T800 tanks, T-45 engine.

If you want information about spaceplanes ...

http://forum.kerbalspaceprogram.com/threads/131122-Spaceplane-Woes-in-the-new-version

http://forum.kerbalspaceprogram.com/threads/131171-Minimize-drag-for-SSTOs

http://forum.kerbalspaceprogram.com/threads/129955-Spaceplane-issues-in-the-transsonic-region

http://forum.kerbalspaceprogram.com/threads/131050-Regarding-Intakes

http://forum.kerbalspaceprogram.com/threads/131184-The-Art-of-landing

http://forum.kerbalspaceprogram.com/threads/129374-Pro-SSTO-builder-pilot-Challenge

http://forum.kerbalspaceprogram.com/threads/116729-Stock-Payload-Fraction-Challenge-1-0-4-Edition (maybe)

http://forum.kerbalspaceprogram.com/threads/95562-fastest-jet-in-ksp-%2AUPDATED%2A-8-8-2015

... are just some of the current threads.

[Sharpy]

My basic strategy was unchanged from when I did it in older versions of KSP high and fast as possible on Turbojets, before pitching up and firing the rockets.

This turned out to be about 1,100 m/s [surface] at around 20-23km up and I initially woefully under estimated the quite substantial rocket power that was then required for the last step on the 1st few attempts. Eventually however got one to orbit on two turbojets and two aerospikes

That's a reasonable strategy, although add nukes (and corresponding Liquid Fuel tanks). What you did is the "Fish Jump" approach: gain 1000-1100m/s on turbojets, then use a strong engine (something of moderately good thrust) to get closer to orbital speeds and altitudes, then switch to nukes to circularize and go elsewhere. It gives you a decent time to orbit and is the general strategy to use with any heavier SSTO that would be too draggy to climb on nuke power alone. The disadvantage is a worse payload fraction (even if the payload total will be better!) and lower delta-V once in orbit. The extra advantage is that you have some high-thrust engines for maneuvers you want to execute fast.

The other approach ("arduous climb") forgoes the intermediate engines, depending only on nukes and turbojets. Once nukes stop giving you acceleration you pitch only a tiny bit up, and fire the nukes. Fifteen minutes in constant flames is quite standard as you sloooowly gain the second 1100m/s and climb just enough so that earned speed lets lift catch up with reduced atmospheric density, and lowered gravity drag. The airplane can be significantly smaller, and arrive to the orbit with enough fuel for some quite distant travel (less fuel total, but much better TWR due to low mass). It's good for passenger flights and small payloads.

The slow climb planes are a challenge to balance drag and thrust, as the nukes are so weak the air at lower altitudes can utterly thwart your attempts if you don't have enough power or too much drag. The "fish jump" ones are a challenge of choosing the right intermediate engine - anything of reasonable ISp and thrust, from Reliant to Rhino, is a fair game depending on the plane size, desired thrust and flight profile. As ridiculous as it sounds, Poodle is a decent choice. Recently I tried an SSTO with BACC SRB for the main hull, and it performed very nicely too. Of course Aerospikes are the "classic" choice.

Rapiers are good in that they can serve both as turbojets and intermediate engines - you save up the mass of two separate engines. Also, they can buy you a little more speed and thrust in air-breathing mode, but are harder to push through transsonic barrier (lower thrust that Whiplashes at transsonic speeds). They have a rather poor ISp though, for their thrust, and so they aren't very good intermediate engines, especially for larger crafts.