Eve Return Mission with FAR and DRE

[Bekiekutmoar]

Hi all,

I'm about to eat my keyboard and need a little bit of advice regarding a return-trip to Eve with FAR and DRE installed; the last couple of weeks I've been trying to perform a succesful journey to Eve. However, I haven't even managed to reach the surface of Eve as my landers burn up in the atmosphere during entry. At least I now know how to make a lander aerodynamically stable during descent, but a lot of problems remain. I've searched the forums and Google for answers, but found not much. All I know an ascent from the Evian surface to low orbit 'costs' 5 to 7,5 km/s Delta-V, TWR should be at least 1.7, and an ascent vehicle should be as long and thin as possible.

Now, how big should I make an ascent vehicle if my goal is to bring a capsule with a mass of 0.8t to Evian orbit? This question is quite prominent as it has great influence on how to design the lander and the transfer stage. The lander shown here has a mass of 90t. Thought I nailed it with that thing, but the heat shield (in this case a thrust multiplate adapter) simply can't withstand the dense Evian atmosphere.

Edited October 29, 2014 by Bekiekutmoar

[Taki117]

You could probably work the dV equation backwards. You know the "Empty" mass of your rocket (Your payload) and you know how much dV you need to get to orbit. (About 8km/s) so using that you can solve for Full Mass of your rocket to get how much fuel mass you need. HOWEVER! you need to keep in mind that engines will change your empty mass. IF you have a mod like Kerbal Engineer or Mechjeb it can tell you the dV of your rocket in the VAB without having to calculate it by hand.

[Jovus]

Let me second the suggestion of KER (Kerbal Engineer Redux). Make your lander in the VAB with that mod installed and the KER part slapped on. Set the mod to show atmospheric stats, and include enough dV to get to orbit. (There are dV maps on the wiki; if you need to you can probably skimp about 1000m/s because they are made for a stock air model.)

Then build something to get it there, of course, whether that be all one giant craft or something you dock to it in orbit.

As to actually flying the thing? I don't know. I've never done an Eve descent or ascent. I should think you need pretty beefy heatshields, and to do your gravity turn a wee bit later in order to get out of the atmo better (because I think the atmo curve at low altitudes overpowers the gravity curve, though I'm not sure).

Good luck making something tall and skinny landable, though. You might want to just suck it up and power through the atmo with brute force, at least at first.

[merendel]

Er, you mentioned the multiadaptor being your heatshield and burning up. Are you going into the atmosphere with the engiens pointed at your prograde vector? Or in other words is that ring on the top side if your picture whats takeing the heat or is the inflateable heatshield on the botom end of the picture takeing the heat?

Engiens themselves tend to make rather good low stress heatshields for situations like comeing down from LKO. Their heat tolerance is enough that you'll slow down before they reach critical overheating unless you come down very steap. However they are not actual heat shields and honestly I've never tried deorbiting on a thrustplate arangement with DRE. Its quite possible that the engiens are fine but the thrustplate is takeing enough heat from between the engiens to fail if your coming in butt first.

What you may need to do is put one or more of the inflateable heatshields on decouplers behind those engiens. Have whatever transfer stage you send that to eve on do the deorbit burn and disconect and return to orbit befor you hit atmo. Once your through the reentry phase you can decouple the heatshields to prepare the engiens for landing and return to space.

The other issue I see is the pictured craft is going to be really hard to land safely. Unless you get really lucky and hit a flat area thats going to tip over and your not going back to space today. In far you can build sideways to a limited degree. Just ensure each radialy mounted stage is itself as aerodynamic as possible. Long and thin will save you on the dV budget over somewhat squat but you have to balance that with being able to land the sucker.

[Stratzenblitz75]

For the heat shield, I highly recommend you use ProdecuralParts' heat-shields. They are designed to work with DRE and you can make them as large as you want.

For the rocket, yeah, 5 - 7.5 Km/s of Vacuum Delta V should be enough. As others have suggested, use KER to figure out how much Delta V your rocket has.

The other issue I see is the pictured craft is going to be really hard to land safely. Unless you get really lucky and hit a flat area thats going to tip over and your not going back to space today. In far you can build sideways to a limited degree. Just ensure each radialy mounted stage is itself as aerodynamic as possible. Long and thin will save you on the dV budget over somewhat squat but you have to balance that with being able to land the sucker.

Yep, long and thin landers are the way to go if you feel like torturing yourself.

(Notice how the terrain is flat, yet I still managed to crash it)

Successful landings: 2

Failed landings: 2 many

Just make a wider landing base, you'll thank me later.

[Laie]

Yep, long and thin landers are the way to go if you feel like torturing yourself.

http://i.imgur.com/0Ltx4AK.png

Yep. That picture shows what goes for flat terrain on Eve. There's the occasional level spot between all those gentle slopes, but we're really talking about "spots" no wider than the lauchpad. If you want to get along without excessive saveloading, your lander must be able to keep standing when you plop it down on a 5-10 degree slope.

[Jovus]

One thing you could do to give yourself a wide landing base and yet have a tall thin launcher is to build such a base attached to the butt of an aerodynamic rocket by decouplers.

It'll still be difficult to land properly, but easier than without.

[Yakky]

However, I haven't even managed to reach the surface of Eve as my landers burn up in the atmosphere during entry. At least I now know how to make a lander aerodynamically stable during descent, but a lot of problems remain.

The lander shown here has a mass of 90t. Thought I nailed it with that thing, but the heat shield (in this case a thrust multiplate adapter) simply can't withstand the dense Evian atmosphere.

http://i57.tinypic.com/30a3u9s.png

I've lately been trying to do an Eve land-and-return mission with FAR (but not DRE). Simply put, you need a huge lander, but slowing down a huge lander in the atmosphere without rapid disassembly is a huge challenge. I still have not succeeded in the round trip BTW, but I have finally stuck a landing... except I broke several of my liftoff engines on touchdown, which stranded Bill Kerman down there.

My successful landing ended up using all of the following strategies together:

1. Don't do a direct interplanetary approach straight into the atmosphere. The speeds are simply too high. Instead, you need to do several gentle aerobraking passes to get down to a very low orbit in order to bleed off as much energy as possible before your final re-entry.

2. The final re-entry has to be as gradual as possible. At the end it will still inevitably get steep and abrupt, but don't make things worse than they have to be.

3. Consider adding a large retro-rocket burn to assist during the peak heating phase. When the FAR dynamic stress level (Q) gets above 40,000, you run an elevated risk of things going boom (especially if you get even the tiniest bit off-axis), so I keep my eye on the Q-meter and fire up a huge retro-rocket to help slow things down once the Q forces get into the upper 30 thousands. The retro rocket combined with the atmospheric drag slows you down very quickly. This takes more fuel and mass than a purely passive re-entry, but for a really large lander I've found it helpful.

Edited October 27, 2014 by Yakky

[technion]

I completed exactly this mission. There's a guide below.

http://forum.kerbalspaceprogram.com/threads/82321-Eve-in-a-single-mission

No matter how much you stack your rocket with heat shields, you'll need to bleed off some of it. From a 100x100 orbit, I was able to burn about 900dv off before dropping the transfer rocket, and things were still quite dicey.

[Bekiekutmoar]

Thanks for all the replies ... ! Gonna see how to improve my lander, although I'll download Kerbal Engineer for sure. Right now I haven't a clue about the Delta-V of a ship in construction, and this mod might help a lot. Things to do in a nutshell:

-Build landing base as wide as possible

-Retroburn hard when approaching the thicker atmosphere of Eve

-Payload as light as possible (well, I prefer the 'aerodynamically' shaped 1-man capsule, then remove built-in ablative shield and monoprop)

[Bekiekutmoar]

Er, you mentioned the multiadaptor being your heatshield and burning up. Are you going into the atmosphere with the engiens pointed at your prograde vector? Or in other words is that ring on the top side if your picture whats takeing the heat or is the inflateable heatshield on the botom end of the picture takeing the heat?

Engiens themselves tend to make rather good low stress heatshields for situations like comeing down from LKO. Their heat tolerance is enough that you'll slow down before they reach critical overheating unless you come down very steap. However they are not actual heat shields and honestly I've never tried deorbiting on a thrustplate arangement with DRE. Its quite possible that the engiens are fine but the thrustplate is takeing enough heat from between the engiens to fail if your coming in butt first.

What you may need to do is put one or more of the inflateable heatshields on decouplers behind those engiens. Have whatever transfer stage you send that to eve on do the deorbit burn and disconect and return to orbit befor you hit atmo. Once your through the reentry phase you can decouple the heatshields to prepare the engiens for landing and return to space.

The other issue I see is the pictured craft is going to be really hard to land safely. Unless you get really lucky and hit a flat area thats going to tip over and your not going back to space today. In far you can build sideways to a limited degree. Just ensure each radialy mounted stage is itself as aerodynamic as possible. Long and thin will save you on the dV budget over somewhat squat but you have to balance that with being able to land the sucker.

I'm using the thrust plate as heat shield. The actual inflatable heatshield is used to keep the ship upright and it works remarkebly well. When the plate hits 1500 degrees, things start to burn and eventually the ship desintegrates. Perhaps the next redesigned lander could reach the surface with the tips given here. Gonna keep y'all posted.

[Bekiekutmoar]

Well, I've downloaded KER and managed to fabricate a 'small' (50t) lander with -according to KER- almost 8 km/s of atmospheric Delta-V. Also now actually using an inflatable heat-shield as protection against atmospheric heat and I've widened the landing base. I have good hope this design works and like to thank y'all for your advise ... !

[Bekiekutmoar]

Update: I've managed to perform a return-mission to the Evian surface with the lander in question ... ! This lander wasn't without flaws however; landing base was too small and even a tiny hill was enough to tip the thing over during landing and crashing in flames on the surface. During ascent, it turned out the vehicle was uncontrollable with the three lateral aerospikes burning, so I had to ditch the still almost full lateral tanks immediately after launch. But even then, there was still plenty of Delta-V to reach orbit around Eve. The next lander will be even smaller and with wider landing base.