Transporting an Eve lander

[Guest]

I have built two rockets capable on carrying an Eve lander and orbiter to Eve and back BAUT COM has some disagreements. If you have any tips that would be nice as I want to finish this mission by saturday! 

Here is the lander

[Aegolius13]

4 hours ago, The Doodling Astronaut said:

BAUT COM has some disagreements.

Huh?  Are you looking for ideas on how to get these things into Kerbin orbit?  Or how to get from there to Eve orbit, or both?  

[Guest]

20 hours ago, Aegolius13 said:

Huh?  Are you looking for ideas on how to get these things into Kerbin orbit?  Or how to get from there to Eve orbit, or both?  

How to transport it into orbit the best way how to build it

[Aegolius13]

Getting to the Eve system is quite easy, with only about 1,000 m/s burn required.  Once you get there, though, you have to either aerobrake (which gets very hot) or put up with a fairly hefty burn to get into low orbit (the map says 1,300 m/s).  I usually just go for the latter, since it takes a bit of complexity over what is already a complicated mission.  

The orbiter shouldn't take anything special, particularly if you elect not to aerobrake. 

The lander, however, has a number of challenges just getting to the surface:

The first is the massive reentry heat.  Anything not protected by a heat shield is as good as dead.  

The second issue is aerodynamic stability once you hit the thicker atmosphere.  Since heat shields tend to be very draggy, flipping is very common, and normal countermeasures like RCS can easily be overwhelmed.  Many people solve this by putting some inflatable heat shields at the back of the craft, just to add drag.  The new robotics parts may have opened some options for homemade airbrakes here. It also helps to transfer any available fuel to the forward-facing end of the ship.

The third issue is getting your ship ready to land, which means getting oriented right, ditching the heat shield, and getting chutes to deploy.  You may find that when you detach a heat shield, it flies up an into your ship (since the shield is much lighter/draggier than the rest of the ship).  There are various ways of dealing with this, like using separatrons or similar to dislodge it, or dropping the heat shield while it's facing sideways or up.  Oh, and chutes tend to get glitchy on Eve.  In particular I'd be leery of saving while your chutes are out.  Trying to load that save may cause... problems.

The fourth issue is landing your ship in one piece.  You pretty much have to hope for a landing site that's flat-ish, though the more stable your lander is built, the less of a big deal this is.  The high gravity and heavy masses involved have a habit of breaking landing legs.  Options here are to include extra legs in case some break, design very sturdy legs (looks like you're on this), and/or use engines to soften the landing as much as possible.  

And then once you're landed, if you want to plant a flag and all that, you'll need a way to get your Kerbal to ground and back.  Many people like to put a small crew module at the bottom of the lander so the kerbal can be transferred close to ground.  .  It's common to put everything not needed for the ascent (chutes, landing legs, Kerbal egress, etc) on decouplers and drop it before taking off.  Ladders are not recommended unless you ditch them before takeoff, since they're very draggy

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With all that, you'll likely be starting out with a large, convoluted package on the launchpad, but it's still essentially a regular launch.  Strategic use of fairings may help with aerodynamic and heat issues. 

One thing I like to do -- a typical Eve lander (including yours) tends to have some very powerful, efficient engines packed on it.  I like to put those engines to work on the Kerbin launch and/or transfer to Eve, with detachable fuel tanks, instead of separate engines from those stages.  This can avoid even more size and complexity, but it can require some unusual designs.

[Zhetaan]

On 8/12/2019 at 7:31 PM, The Doodling Astronaut said:

If you have any tips that would be nice as I want to finish this mission by saturday!

Here's one:

On 8/12/2019 at 7:31 PM, The Doodling Astronaut said:

Don't narrow your fairing in the middle as you have in the photo.  It's better to have a smoothly tapered fairing from the widest point to the tip than for it to have a wasp-waist constriction as yours does.

[Guest]

50 minutes ago, Zhetaan said:

Here's one:

Don't narrow your fairing in the middle as you have in the photo.  It's better to have a smoothly tapered fairing from the widest point to the tip than for it to have a wasp-waist constriction as yours does.

So one fairing... okay!

[sturmhauke]

16 hours ago, Aegolius13 said:

The second issue is aerodynamic stability once you hit the thicker atmosphere.  Since heat shields tend to be very draggy, flipping is very common, and normal countermeasures like RCS can easily be overwhelmed.  Many people solve this by putting some inflatable heat shields at the back of the craft, just to add drag.  The new robotics parts may have opened some options for homemade airbrakes here. It also helps to transfer any available fuel to the forward-facing end of the ship.

I have yet to attempt an Eve landing, but I have experimented with folding wings and such in Kerbin's atmosphere, which is of course thinner. Aero forces can easily overwhelm servos and prevent them from moving, or even break parts off. What you want to do is design your servos in such a way that they are minimizing induced drag. Don't try to push a wide surface face-first directly into the airstream. For an Eve airbrake, perhaps you can have pistons that extend backwards with fins attached, to move the center of pressure further aft. Then another set of pistons attached to the first perpendicularly, to push them horizontally outwards like an umbrella. If you try to use a powered hinge it's unlikely to work. 

[Claw]

Not necessarily "one fairing" but definitely want to avoid the wide, then narrow middle, back to wide setup. It would be better to either have one fairing, or replace that middle small fairing base with a larger one.

 

Also, Aegolius13 also pointed out something that often catches people. The atmosphere is thicker and tends to cause difficulty during entry. Things burn up more, flip over easier, and such (as Aegolius13 pointed out). So once you get there, you may need to try different speeds and angles for entering the atmosphere.