SSTO Design efficency (FAR)

[Rakaydos]

My SSTO isnt as efficnt as I would like. My jets will only take me to about 1600m/s before thrust=drag, and while I can make it to orbit on Rapiers and RCS from there, I'm wasting a lot of fuel doing so.

Figurin out how to add more thrust without increasing drag or messing with the CoM too much is my issue, as my design has the CoM lined up with both a docking port and the cargo bay, and my fuel is balanced that my CoM goes up and down, not foreward and back.

Edited November 6, 2014 by Rakaydos

[Alshain]

Why is 1600 m/s bad? They won't go much faster than that, it's the height of their velocity curve in FAR.

[How2FoldSoup]

That's because of FAR. FAR, if i remember correctly, nerfs the stock turbojets to have slightly more realistic top speed numbers. 1600-1700m/s sounds about right for the top speed I usually have with my SSTO's before switching to rockets. If you want more dV in space, pack more fuel or use nukes(or both).

[Rakaydos]

Eh, it's really more like 1550 m/s, but if mach 5+ really is an unreasonable target, I suppose I'll just not be that good of a refueler. Oh well.

[Alshain]

Eh, it's really more like 1550 m/s, but if mach 5+ really is an unreasonable target, I suppose I'll just not be that good of a refueler. Oh well.

FAR is a realism mod. Mach 5 is about the limit of a realistic air breathing engine. It really is that simple, so ferram4 fixed it.

(Actually Mach 5 assumes some degree of future tech, the fastest manned airbreather was the SR-71, topped out at 3.3)

Edited November 6, 2014 by Alshain

[Motokid600]

Its the nerfed jet engines. It got me too. I updated FAR at some point, next thing I knew my plane had lost almost a third of its power. Where I used to to be able to go sub orbit in a heart beat, but now not so much..

[Wanderfound]

1,500m/s is plenty fast enough to hit orbit with tanks 2/3rds full. See post #3 in the Kerbodyne thread linked below for some tips.

[Hodo]

1,500m/s is plenty fast enough to hit orbit with tanks 2/3rds full. See post #3 in the Kerbodyne thread linked below for some tips.

Exactly. The trick is now you can't just jet power your way into orbit. 1500m/s is FAST! I usually shoot for this speed around 20-25km then once I hit mach 5 I switch over to rockets and shutdown the jets and increase my climb rate from 10deg AoA to 20-25deg AoA. I can usually get most of my SSTOs into orbit with over 1200m/s DeltaV remaining.

The other thing is, the REAL life Skylon project shoots for mach 5 before it does its SABRE engine switch to closed cycle for the ascent into space.