Eve science plane math check

[Nich]

I am planning on sending down a science plane to get Science and explore Eve.  I want to make it as efficient as possible so I am doing some math.  If you could check it over and give comments suggestions it would be much appreciated.  Here is my starting point.  The craft will have a mass of around 11t when I get done adding wing area.  

So on Eve it will weigh 11,000 kg*9.81m/s^2*1.7 = 183.447kN

From 

We know that 2 degree AOI will give optimal wing L/D.  At 2 degrees AOA the wings will produce 80kN of lift per 10 wing area on kerbin.  To adjust this we need to multiply by 5 for Eves denser atmosphere. Thus 400kN per 10 wing area.  This means we would need 4.59 wing area.  I already have a little over 8 wing area SO I could probably cruze a little slower then 100m/s on Eve and be at L/D max.

What is the math to adjust? L = 1/2 * CL * density * V^2

Edited March 6, 2016 by Nich

[Snark]

11 tons is your empty weight, yes?  Because just the fuel tanks and engines alone are going to be over 11 tons.

Also, not sure whether you may have structural-strength issues with those long, narrow-aspect wings sticking out, since they're four sections end-to-end.  They may be too floppy.  If it turns out to be a problem, one option would be to make it a biplane, i.e. have the same wing area, but two stacked wings that are 2 sections each, rather than a single wing of 4 sections.

Eve reentry heat can be brutal, and this is a design that's pretty much impossible to heat-shield, so my initial reaction was "how is that going to get down to the surface?"  But I suppose that since it carries ISRU, you don't have to land it full, and you can use the rockets to slow it down a lot before you hit atmosphere.  If 11 tons is your empty weight and I'm correctly reading your fuel capacity as 8 tons, that would give you a dV of around 1800 m/s, which I suppose is enough to significantly cushion the experience (as long as your initial landing is in a place that has mineable ore... the small-size drills only work at concentrations over 2.5%).

Edited March 6, 2016 by Snark

[Nich]

Yes I expect I will get the most distance doing a full burn as high as possible and gliding to my next landing.  If I am flying around with fuel I am fine going with a suboptimal aoa 

[fourfa]

I had the same reaction as Snark - getting something to the surface successfully will probably end up driving the design.  For instance, a delta-shaped plane could be stuffed inside a conical fairing mounted to its nose, with the wide end enclosing the tail.  Add a disposable retro engine and heatshield, blow them off in the lower atmosphere, and glide to a landing.

Might want to find space for a narrow-band scanner, and learn to use it in flight.  Otherwise the 2.5% requirement of the small drills may well prove deadly.

I've taken a couple passes at Eve-ISRU rocket planes and it ain't easy!

[Nich]

Just wanted to thank everyone for the help My eve mission is underway