Really struggling with an Eve lifter

[Foxster]

I just can't get a craft off Eve!

I've tried lots of designs. Some stacks for streamlining, some fat asparagus with nose cones, 4 stages, 8 stages, lots of fins, lots of SAS, various to-orbit profile from turning at 1km to 30km...

None get to orbit. I could do this fairly easily with just trial and error under 0.9.

The problems are:

A lot of the engines have little or no thrust at lower altitude. Makes it hard to find a good set of engines for the lift.

Even with streamlining the things shake themselves apart without lots of strutting and even then they wobble something fierce.

It flips out at various altitudes. Fins and SAS help some but I can't seem to find the balance.

Here's the latest disaster that doesn't have the dV for orbit, I was just hoping to get it fly to high altitude but it flips out at stage 3.

Anyone got a working Eve lifter that will get a Kerbal to orbit?

[maccollo]

Ok, so the problem is god awful ISP and thrust close to sea level. The solution?

You really cannot afford to linger at the bottom with barely enough thrust to take off. You must get out of there fast, drag be dammed!

Here's a design just over 110 tonnes that can launch from the very bottom.

Generally the design principle here is MAAAAAXIMUM POOOOWER for about 10 seconds, then stage and sustain the acquired velocity with less thrust. Once you are up to speed you don't need nearly as much thrust to sustain that speed, and you can quite easily climb out of the ISP black hole.

Obviously, you don't have to take off from sea level. I believe the highest point is at about 5 km, which goes a really long way to mitigate the problem.

Hitting it from orbit is very hard, but you can put wheels on your EAV and drive there. The old pancake EAVs obviously wont cut it anymore, but way back I built this rickety contraption which might actually be pretty useful now.

Edited May 3, 2015 by maccollo

[Foxster]

Thanks, that's really helpful.

You have flown that in 1.0.2, right? I only ask because without fins it looks like it might flip.

I'm guessing its an LV-909 in the final stage. What's the engine in the middle?

[GoSlash27]

Here's a design just over 110 tonnes that can launch from the very bottom.

https://dl.dropboxusercontent.com/u/22015656/EAV.png

maccollo,

Have you actually confirmed that on Eve? I wouldn't expect it to work based on the engine specs.

The only 2 engines I would expect to be viable would be the Mammoth and the Aerospike.

curious,

-Slashy

[maccollo]

It is actually over engineered, and gets to orbit with lots of delta V to spare. Total vacuum delta deltaV to orbit is about 7.5 km/s.

Also while the design isn't aerodynamically stable it is very controllable. This is a good thing actually, because it means you come down engines first during EDL.

Craft file: https://dl.dropboxusercontent.com/u/22015656/eve%20lander.craft

Edited May 3, 2015 by maccollo

[Foxster]

Confirmed. I made it to orbit with it. Needed a couple of tweaks for me to get there but that's probably my piloting skills.

What kind of profile for the lift did you use? I was going straight up to 40km and then banking fairly quickly.

- - - Updated - - -

My cunning plan is to land this on chutes and with some fuel in just the 1st stage, using those engines for final braking.

I'm going to take along the gear for makings fuel and top it off before lifting. Leaving behind all the landing and refueling stuff.

[maccollo]

I started the gravity turn pretty early, around 5 km. Ended up a bit to high, so 45 degrees at 35-40 km seems like a good mark for this particular ascent vehicle.

Protip:

It seems like struts add a significant amount of mass now, but only to the part where you first attach them. So whenever you add struts start from the bottom stage so you can ditch the strut mass when you stage.