Intake Differences?

[GoSlash27]

46 minutes ago, mystik said:

I am playing around with my SSTO and replaced all intakes with shock cones. Would not go past 375m/s. Replaced some with ramp intakes and now the thing maxes out at 1350m/s. Well, I stop there because the claw starts to melt, at which point I point it towards the sky and it whooshes out of the atmosphere.

 

This is weird. Seems that the shock cone does not have enough power to get the thing up to the critical speed on it's own. It's a heavy beast at 400t, but still, having half ramps seems to change the flight significantly.

 

I don't understand. If all intakes are left as ramps the engines cut off on the runway. It has 6x2 rapiers, 5 whips, struggles to reach orbit since the ship had over 18 rapiers in it's original config but had a weight of over 500t.

Yeah... I wouldn't know where to begin on that one. I've built testbeds that fed 3 whiplashes from 1 shock cone and 4 whiplashes from 1 shock cone and 1 precooler (necessary only for takeoff). OTOH, the VRI, while fine for keeping the engine lit, is extremely draggy for a front node part. If you're relying on clean aerodynamics rather than raw thrust, you really don't want to use that part.

Best,
-Slashy

 

@swjr-swis,

 Absolutely right. The longer a part is, the more susceptible it is to losing it's low Cd when not perfectly aligned. Sometimes it's worth using a physically shorter part to alleviate this tendency.

 I always preach "nose perfectly prograde at Mach1". The plane should be built with enough incidence to make this happen, else all those wonderful "high speed low drag" parts work against you.

Best,
-Slashy

Edited December 29, 2016 by GoSlash27

[GoSlash27]

Interestingly, these values can be directly added to give you an idea of how parts will behave when stacked because occlusion has already been factored in.

For example, a Mk1 cockpit+precooler would be 1.88 while a shock cone + Mk1 inline would be 2.46. Mk.1 cockpit+2 radial structurals is 3.92, and so on. You can mix and match the values to give you an idea of how clean your arrangement would be.

 

Edited December 29, 2016 by GoSlash27