eve lander and return , building help

[bjerrang]

Building a 8000dV lander and return to orbit ship. (Tug will be used for rest)

Trying to slow down with heat shields , but still with rcs and wings it flips and explode. 

This is the ship that will enter eves atmosphere. 

Any tip ?

 

 https://imgur.com/a/r5FC7oR

Edited September 29, 2018 by bjerrang

[mystifeid]

Try using two inflatable heat shields - one on the top and one on the bottom. Also you could try reducing your orbit to something like 90-100km before deorbiting - ie so that your speed is down to around 3200m/s before starting your deorbit burn at the top of the atmosphere. If you have enough fuel and can decelerate to around 800m/s by the time you hit about 60km you can even ditch the heat shields altogether. But if you're going for the big aerobrake, they tend to flip and you'll probably need the two heat shields.

You can even get creative and try turning one of the heat shields upside down. Normally when you add an inflatable heat shield to a craft, it won't inflate - either in the VAB or in flight - if something is attached to the pointy end. But you can get around this by first using the rotation tool then the offset tool. (Be aware that if you then detach/reattach the heat shield it will no longer inflate and you will need to start over). You will also need to use the offset tool to attach another part to the other side of the heat shield. However, I'm not sure if this will make any difference to any propensity for flipping.

With two heat shields, possibly the thing that will have the most effect on stability is the distance between the heat shields.

Edited September 29, 2018 by mystifeid

[bjerrang]

Thats like cheating ;-)

I would like a rocket that will work and stay stabile during aerobrake. 

It does not "flip" but it angles so much that the Science Jr blows up. 

[OhioBob]

Somebody else just recently asked this same question.  Perhaps you can find some helpful suggestions in that thread.

 

[Gargamel]

11 hours ago, mystifeid said:

Try using two inflatable heat shields - one on the top and one on the bottom.

This is what I do, but make sure they aren't centered on the COM.  I had an early prototype that was very very stable, but sideways.    Make sure the trailing shield is farther from the COM than the leading one. 

[mystifeid]

17 hours ago, bjerrang said:

It does not "flip" but it angles so much that the Science Jr blows up.

You could try putting the Science Jr in a 2.5m Service Bay.

[bjerrang]

Kinda worked with the double heatshield. Looks awful , but i survive reentry.

Just gotta make the shutes work properly now.

That big service bay back to kerbin requires alot bigger ship.

[mystifeid]

1 minute ago, bjerrang said:

That big service bay back to kerbin requires alot bigger ship.

If you have a scientist along for the ride you can remove the science from the Science Jr. Maybe put the service bay at the bottom of the central stack and stage it before liftoff.

[bewing]

Or similarly with a miniScience container.

 

[Freshmeat]

My Eve descent/ascent vehicle looked like this:

Sorry for the poor lightning, but I seem to have no other images. The lower stage fires to enter the atmosphere, and then discards. The real trick is the six wings shielded with large heat shields in the top, and an inflatable one in the bottom. Still goes for a rocky ride, but all tanks are empty to maximize drag/mass. The upper stabilizers are jettisoned after the parachutes engage, so they are clear from the landing site. Additional one way landers provide base camp and ISRU for filling up the tanks for return to orbit. Designed for four kerbals with life support for five days and absolutely no room to spare; the mission parameters stipulated immediate pickup by an orbital shuttle to return to the interplanetary transport craft.

[Foxster]

A slightly less fugly alternative to the double inflatable heatshield solution is to mount a lot of airbrakes at the trailing end of the craft - just make sure they are in the heat occlusion shadow of a big heatshield on the leading edge of the craft when deployed. 

With a heavy craft you might need a lot of stacked airbrakes, maybe 20+, but they are light and you will want to discard them, along with the other landing stuff like chutes and landing gear, before taking off again. 

Whatever you go with, you will want to get the CoM as near the leading edge of the craft as possible. 

[Aeroboi]

I have a alternative solution to what Foxster has said. It may be less easy but if you understand it you should be able to emulate it.
You can use normal wing pieces instead of airbrakes at the trailing edge. I often do this because wing pieces have more lift rating so you will need less of them to create the desired balance.

Often this creates undesirable drag during launch from kerbin so what I do is put the wings in a fairing or mk 2 or mk3 cargo bay at the back. Putting them inside fairings or cargo bays will hide them from drag. Then jettison the fairing during aerobraking or open the cargo bay. Opening a cargo bay itself creates drag to begin with. As for the method of putting wings inside it.
What you do is pack as many as you can inside to the point where you find it aint clipping and use move editor tool to have them near the doors. Then set them to deploy with authority limiter to 150. Then rotate them in the editor so that they're aligned with the cargo bay doors outer mesh but while still being stowed when you close the doors.
If you deactivate deploy or change deploy direction the elevons should extend outside the doors. If they extend inside you need to rotate  them upside down.

What you do then upon Eve arrival is open the cargo bay doors, pin all the elevons context menus and then click "Deploy direction" on all the elevons.

The result is that they will stick out with a very sharp angle to create incredible drag.

The best part is that you can use the largest elevons (BIG_S Elevon-2) It has 4 times more lift rating then the A.I.R.B.R.A.K.E.S. and has a heat tolerance of 2400 degrees so doesn't do poof as quickly as the airbrakes.
 

  It's a very Kerbal solution but it helps.

Edited October 5, 2018 by Aeroboi

[bigcalm]

A brief guide to Eve Lander problems, and solutions.  I'm ignoring the most obvious in that if you craft explodes on entry and you don't have a heatshield, you should know to put a heatshield on.

My Craft flies sideways after initially ascending ok

 - Your craft is most likely not streamlined enough, or has some property that is causing the craft to fly sideways.  This is likely not fixable by adding tons of reaction wheels, but it depends on the severity of the problem.  It's also possible that once you clear the lower-atmospheric treacle it will become controllable again, so throttling down whilst ascending through the lower atmosphere can help.  Here's an example of a failed one from me -- too unaerodynamic:

 

On atmospheric entry, the craft spins around and immediately blows up due to overheating.

 - Essentially, this is because your centre of mass is a long way from the heatshield.  This is difficult to avoid because you want your craft long and nicely aerodynamic for the ascent.  There's two possible solutions - pad the bit nearest the heatshield with some (ejectable) mass, or use additional heatshields at the top which act like very very draggy fins and stop it from spinning round.  An example --

 

Despite having over 8k delta-v, I can't make orbit

  - This can be a number of things, but most likely:

    -- Your craft is not aerodynamic enough.  General hint - avoid Mk2 plane parts.  Also, if you're using the adjuster tool to make it "look" more aerodynamic, that's not how KSP calculates drag!

    -- Your craft has poor thrust to weight ratio in at least one of your stages.  If you have MechJeb installed then in the VAB, the "SLT" number is the one you want to pay attention to - this is the surface level thrust, i.e. the thrust you will achieve at sea level (set the body to Eve, though, eh?).  Kerbal Engineer Redux can also give you the same information.

  -- Aerodynamic instability in one or more stages.

 -- Ascent profile.  Very generally (and again, aerodynamics weighs heavily in this), you should ascend to roughly 25k above Eve before making your gravity turn - basically, get out of the treacle-like lower atmosphere before steering!

Though it is tempting to add fins and stuff, be careful.  This is a successful one-man ascender --

However, the addition of basic fins on the upper stage changed this from being able to make orbit from sea level with 1000ms spare, to one that could not make it to orbit from a starting altitude of 2000metres.   On Kerbin, you can generally brute-force your way through the lower atmopshere with enough engines.  On Eve, you probably can't.

Ejecting re-entry stuff causes explosions

 -- This is either when you're in the descent phase, when you've dropped below the exploding-due-to-entry-heat phase, and want to get rid of extraneous heatshields, or on the surface when you want to get rid of parachutes and landing legs.

 -- Separatrons are good (in one of the earlier versions of KSP Separatrons basically didn't work at low altitudes on Eve, but this appears to be fixed since at least 1.3.1).  Spinning whilst staging can also help.

 -- Ejecting the bottom heatshield is recommended after inflating the parachutes.  This is mainly because before this, your lovely aerodynamic rocket will move much faster than the ejected draggy heatshield, causing you to crash into it.

 -- It can be helpful to lift off and then eject any landing gear structure if that's possible, depends on your first-stage engine though - at the same time normally works.

 -- Landing legs exploding on landing is almost inevitable, even if you load up on stupid amounts of parachutes to have a softer landing.  Have lots of landing legs and some will likely survive, or a substructure that you attach your landing legs to that will take the place of the exploded landing legs.  Alternatively, if you aren't opposed to mods, there's some much tougher landing legs available in other part packs - certainly better than the Mk2 at least.  Here's an alternative that just uses a bunch of girders instead of legs --

 

Testing on Kerbin

 -- mimicking the conditions of Eve is very tricky on Kerbin, but you might want to try the following tests.

 -- With the ascent vehicle you should generally be able to take off, get to Kerbin orbit, land back on Kerbin (or at least, get a few feet from the surface as you probably won't have landing legs on that bit), and then get to orbit a second time.

 -- Are you able to fly stably at a constant low altitude whilst picking up speed?  Do you ever reach a speed where everything explodes?

 -- You can sort of mimic entry conditions by first putting it in orbit of Kerbin, accelerating to roughly 3km/s, and then doing a little burn at apoapsis to set your periapsis deep inside the atmosphere - this will give you an entry speed into the atmosphere similar to that you'll get from low Eve orbit.

 -- Depending on how you feel about it, you could Hyperedit to Eve Orbit or Eve Surface for testing.