High speed flight

[tomf]

I am trying to build by first 1.0 spaceplane but at the moment I am struggling to even break the sound barrier.

At about 12,000m and 300m/s the thrust on my “whiplash†turbojet is starting to decrease rapidly. I have plenty of intake air available.

I don’t have any pictures available

The craft is pointy with small rear mounted delta wings

It has 1 turbojet for a peak TWR of ~1

And 2 “sparkâ€Âs for circularization

The total weight on the runway is ~20 tonnes

I was expecting the turbojet’s thrust to peak at around 1000m/s and at much higher altitude. What am I doing wrong?

[Deutherius]

Well, your problem is twofold:

1) That plane is pretty damn heavy. Probably not impossible to put a 20t craft into orbit on a single Turboramjet, but you are making it too hard on yourself.

2) The thrust of the turboramjet increases a lot after mach 1. After reaching 12 km, pitch down to pick up speed. After you bust through mach 1, your engine will start producing way more thrust. If you cannot break ~350 m/s even in descent, then you have too much drag.

Other than that, you mention that you have plenty of intake air. Careful there, too many intakes will add a lot of drag, making it a lot harder to break mach 1. So will radially attached parts and excessive use of wings.

[tomf]

I guess I was building a 0.90 design and I need to adapt more.

Are there guildelines for building an SSTO along the lines of the ones the GoSlash produced for old aero?

e.g. 1 turbojet for every n tones of plane

x lift for every tonne

etc.

[n0xiety]

1 ram intake is actually enough for a turbojet engine. 2 would make it go up to maybe 24k without flaming out if you have the speed at that point. More than that will add alot of unnecessary drag. Seems like the old intake abusing days are over like we did in that soup atmosphere.

Edited May 19, 2015 by n0xiety