[Answered] Payload LKO delivery SSTO spaceplane with B9 under FAR, engine/altitude/thrust issue

[fatcargo]

I have designed a SSTO as LKO lifter with B9 and stock parts that uses Sabre M engines in air-breathing mode to maximize fuel usage.

After several modifications i realized that when craft reaches 25-31 km altitude and about 1700 m/s, engines loose thrust and craft can no longer climb.

When i switch to rocket mode, craft starts to climb and all fuel and oxidizer are consumed without visible change in climb rate and speed.

Adding more LF/OX does not help as it turns solving into classic rocket problem which i wanted to avoid.

So, i'm asking are there any part packs that have air-breathing engines with usable thrust in 25-40km altitude and speeds over 2000 m/s ?

Simply, i'm looking for air-breathing engines that work as stock turbojets did before FAR.

PS :

I've looked for various engines and i'm interested in using "thermal turbojets" inside KSP Interstellar but it's development has stopped.

There are few unofficial branches to make it compatible for KSP 0.90 but they too use resource frameworks that are abandoned.

Are there any similar "thermal turbojet" parts packs that are actively developed ?

Edited January 8, 2015 by fatcargo

[steve_v]

A jet producing any thrust over 2000m/s is pretty unrealistic, if you really want turbojets to work like they do without FAR, just comment out (or tweak) the nerfs starting at line 694 in FerramAerospaceResearch.cfg. It'll be pretty OP though.

Also, check your drag. - turn on "show aero forces" in the FAR setup menu and look at various parts in flight. As jet thrust falls off drag becomes your biggest enemy, especially with the new skin friction model.

[hab136]

Yeah, the jet engines in stock KSP are completely overpowered. Even with FAR, they're still ridiculously overpowered; you need AJE to make them realistic.

There's a maintenance release of Interstellar for 0.90

Karbonite has overpowered "jet" engines that are really thermal engines, which even work on Eve/Jool/Duna.

[fatcargo]

@ steve_v : I thought of it too, but i want to make my craft shareable without forcing potential users to add/edit configs or parts beyond what is already available. As for drag, i thought of it too as i checked FAR's flight data and saw severe L/D drop. I can't reduce it anymore beyond sweeping the wings even more (which is now possible with B9 thanks to bac9's new proc wings). I even attached proc fairings to shroud front section and reduce frontal drag. Also, i should reduce intakes (count and size) to required minimum for operating in upper atmo.

@ hab136 : Last time i could make a large weight/size payload SSTO was before using FAR. It killed jet/rapier performance to near unusable. To install AJE would make it impossible.

Anyway, thanks for responding. I assume this discussion is concluded.