How to break mach with spaceplanes

[quasarrgames]

I'm having some troubles with sstos.

I built a small spaceplane, 1 panther and 2 terriers, weighing less than 18 tons, as skinny as possible to reduce drag.

Problem is, it just can't break mach 1. I tried my usual 15-20 degree ascent, couldn't get past 3000m. Then tried the 5 degree ascent everybody else uses, still had a max speed of about 250m/s. Even when i dived to gain speed, the max i got was maybe 300m/s.

And yes, i know i'm using a panther, but i did the math and it should have a thrust to weight ratio of about 0.7. Considering that people have made functioning sstos in the past with less than 0.4 twr, i find this especially strange.

I was eventually able to break the sound barrier, but it took a stupidly large twr (over 2). But that added so much more engine weight that i couldn't get to orbit.

So, what gives?

[Gaarst]

Are you using the afterburner ?
Subsonic jet engines (Juno, Wheelsey, Goliath, and Panther w/o afterburner) will lose all their thrust when approaching transsonic speeds.

Even if you use engines designed for supersonic speeds (Rapier, Panther w/ afterburner and Whiplash), there is a very strong augmentation of drag when approaching the speed of sound (see [URL="https://en.wikipedia.org/wiki/Wave_drag"]wave drag[/URL], I think this is the actual phenomenon). So, even with those enginesyou'll need a lot of thrust to pass Mach 1. Edited November 17, 2015 by Gaarst
Added things

[GoSlash27]

^ This. It will also help if we can see a pic of your spaceplane. Perhaps there's something going on that's making it draggier than it should be.

Best,
-Slashy

[quasarrgames]

You bet your bottom dollar i was using the afterburner! Still, i've made stubbier ships with less thrust-to-weight that cleaved through the sound barrier like butter, in a fifteen degree climb, so something's going on here.

Edit: and here's a picture
[img]http://i.imgur.com/6KokI6M.png[/img]
What's the problem, doc? Is it bad? Edited November 17, 2015 by quasarrgames

[GoSlash27]

Quasarrgames,
2 things jump out at me off the bat:
1) That's way too much intake area and those intakes aren't clean ones. That's a boatload of drag you don't need.
2) You don't appear to be using wing incidence to generate lift, but rather angle of attack.

For problem #1, what other intakes do you have available to play with?
For problem #2, using body lift is super- bad for drag. You want the nose pointed exactly prograde around Mach 1, not above it. This gives you the smallest, cleanest profile and allows you to cut through the sound barrier. Once you clear about 360 m/sec, your drag falls off and your thrust picks up.

Best,
-Slashy