Questions About Eve

[The Flying Kerbal]

Hey Guys...

I'm having some difficulty planning my mission to Eve and Gilly, maybe you could throw me a bone of advice?

First question is, it it possible to use a NERV engine as a heat shield while aerobraking in Eve's atmosphere?  I have a tendency to use engines like this, but I just can't find any altitude that doesn't see me seeing my vessel explode.  I'm hitting the atmosphere at 5000m/s; I could fire up the engine I suppose, but the whole idea was to get captured without wasting any Delta V... I'm a cheapskate that way.  I've tried this so many times now I'm beginning to think it's only a proper, dedicated heat shield which can take the heat of slamming into that reinforced concrete wall Eve pretends is an atmosphere?

Having been looking at other options, I set up an Orbit around Eve at it's maximum possible diameter, at the very edge of its SOI using the Set Orbit cheat under Alt F12.  I thought I would forget about aerobraking and just use the engine to enter a lower orbit, and since I was going to be using fuel anyway, I thought I would align this orbit with Gilly rather than an Eve equatorial orbit.  This worked exceedingly well, and when the time came to head out to Gilly, having the orbits inclinations the same, made this wee buns.  But this was done while still playing after using the cheat menu, I don't claim any credit for any achievements accomplished without doing the mission right, from launch to completion.  So my second question is, is there anything about not being in an equatorial orbit with Eve which increases the chances of the mission going sour?  What I intend to do is basically the same as what I did at Duna, a small lander parachutes down to the surface of the planet, while an RCS powered lander lands on its moon?

All advice will be very much appreciated... thanks all!

[Draalo]

If you want to aerobrake use a 10m inflatable heatshield and 2 radial attached engines. So your engines are functional till inflate and after ditching the shield.

Note that Eve has a thick atmosphere, a small probe only needs a droguechute for landing. Heavier stuff need no droguechutes and -rule of thumb- only half the chutes for a Kerbin landing.

Gilly has such a low gravity, consider using ion engines. Yes, even if you land a MK2 Lander Can. Sunlight is brighter there, only 3/4 of solarpaneels are nes. in comparision to Kerbin(orbit). But RCS is fine too.

Good luck and have fun

[bewing]

Please understand that heating goes as density * velocity cubed. Yes, you can get away with coming back to Kerbin from Minmus at 3100 m/s.

But entering Eve's atmosphere at 5km/s produces more than 20 times as much heating as that, just because of the excess speed. Then yes, you can throw in the extra density too, if you like. Aerobraking at Eve requires very creative engineering (or using exploits, such as the AIRBRAKES trick). I personally think it's better just to burn the extra fuel -- especially if you are willing to refuel at Gilly.

Edited October 30, 2017 by bewing

[Cpt Kerbalkrunch]

Are these unmanned missions you're talking about? If so, and you don't plan on leaving, it's actually pretty easy to land on Eve; as @Draalo said. A probe core with a shield and a parachute will land easily. I sent the ship below for a contract at one time or another. Don't really remember.

 

 

If you want to send some Kerbals (and bring them home), you're talking about a much more difficult (and expensive) proposition. These are pics of my last 2 Eve missions.

 

 

The inflatable heatshields are pretty much indispensable. The shields at the top are to keep the whole thing from flipping over and being obliterated. It's a 2-Kerbal ship, so it's a lot bigger than necessary, but it worked really well. You'll notice coming down (especially in a larger ship), that all the action occurs from 50-40km. If you reach 40km without being blown up, you should be fine.

 

 

This one is a 3-Kerbal design with the Mk1-2 command module. Pretty much the same concept. I recommend dropping your Pe to about 60km or so and just let Eve bring you in easy. It has large land masses, so you should be able to hit dry land with just a couple tries; if not on the first.

 

 

And if you are going to use a large ship, bring drogue chutes as well if you want to land without using up your fuel (you'll be going too fast for your regular chutes to open without slowing down somehow). And plenty of landing legs or trusses of some kind. The heavier you are the more you need.

 

 

For Gilly, what can I say? You can land anything on Gilly. The hardest part is having the patience to make the landing. It takes a looong time. Hope all goes well. Eve is a blast, but it ain't easy. They don't call her the Purple Widow Maker for nothin'. Or maybe I'm the only one who calls her that. 

[Cpt Kerbalkrunch]

3 hours ago, The Flying Kerbal said:

I just can't find any altitude that doesn't see me seeing my vessel explode.  I'm hitting the atmosphere at 5000m/s; I could fire up the engine I suppose, but the whole idea was to get captured without wasting any Delta V... I'm a cheapskate that way.  I've tried this so many times now I'm beginning to think it's only a proper, dedicated heat shield which can take the heat of slamming into that reinforced concrete wall Eve pretends is an atmosphere?

Having been looking at other options, I set up an Orbit around Eve at it's maximum possible diameter, at the very edge of its SOI using the Set Orbit cheat under Alt F12.  I thought I would forget about aerobraking and just use the engine to enter a lower orbit, and since I was going to be using fuel anyway, I thought I would align this orbit with Gilly rather than an Eve equatorial orbit.  This worked exceedingly well, and when the time came to head out to Gilly, having the orbits inclinations the same, made this wee buns. So my second question is, is there anything about not being in an equatorial orbit with Eve which increases the chances of the mission going sour?

When reading back over your question again, this point stuck out. It wasn't your inclination that made the difference, but your trajectory. At Kerbin, I've survived reentry at just over 8km/s; and been instantly turned into a puff of smoke at less than 4km/s. The difference is in how steeply you hit the atmosphere. Sort of the difference between wading out into a pool and just doing a belly flop from 30 feet up. If Eve were a normal planet, you could aerocapture from Kerbin easily. You've seen how easy it is at Duna. You don't even need a heatshield to free-capture from Kerbin. Eve, however, is unforgiving. I tried to aerocapture there in my earliest tries to conquer the planet. They were spectacular failures. Whether manned or not, I would establish an orbit before making the dive.

[The Flying Kerbal]

Yes this is an unmanned one way trip to Eve and Gilly.

The above shows what will (more or less, still some work to be done) arrive in the Eve system if everything goes according to plan.  The original idea was to simply point retrograde and let the nuclear engine act like a heat shield while I was captured for free into an Eve orbit.  Unfortunately experiments and what you guys have said would suggest that isn't so straightforward as I had originally thought.  The equation bewing typed up certainly was enough to make me rethink the whole idea of aerobraking without a heat shield!

I never realised an inflatable heat shield didn't block an engine, that's definitely good to know for future missions.  Unfortunately I haven't got the big inflatable yet, and I used up all my science picked up on and around Duna, to get nuclear propulsion, so I can't use it this time.

Nope, I do think the best solution is to forget about using Eve's atmosphere and just fire up the nuke to establish a nice stable orbit inclined to match Gilly's, drop the Pe. into the atmosphere, separate the Eve lander, and then pull the Pe. back up again.  I know the little lander's heat shield will protect it, the Gilly lander will remain in orbit to play the role of relay until all science from Eve's surface has been transmitted back to Kerbin, then push out to meet up with Eve's moon.

Thanks guys for the really fantastic advice, I'd be stuck without it.

[Laie]

2 hours ago, The Flying Kerbal said:

Yes this is an unmanned one way trip to Eve and Gilly.

Then by all means, just put on a heatshield and be done with it. This may go against your cheapskate grain, but certainly won't ruin you.

You probably want a 2.5m shield for all the parts sticking out. The good news is that you can shave off at least half of the ablator already in the VAB.

[Draalo]

5 hours ago, Laie said:

Then by all means, just put on a heatshield and be done with it. This may go against your cheapskate grain, but certainly won't ruin you.

You probably want a 2.5m shield for all the parts sticking out. The good news is that you can shave off at least half of the ablator already in the VAB.

Cant see something sticking out. Note: only the top is the eve lander, bottom is Gilly lander + propulsion for the trip.

Edit: Are you german too? If so, feel free to join my discord https://discord.gg/M8x7DZ7 (there is also a subchannel "english only" so everybody may join)

 

@The Flying Kerbal: 

Your vessel will do the job, here some tweaks:

 

- Eve landerprobe:

Too much chutes on the eve probe. A single Mk16 chute will do the job, no drogue needed, the heatshields drag will easily slow you down to comfortable <200m/s at 10km altitude.

Swapping the Communotron 16 against a 16-S allows you to controll the probe while descending. An extended c16 will probably brake during descent if extended. If its retracted you ll probably not be able to do measurements in the high and low atmosphere.

Add a science container. You can do temp. etc. measure in high atmo, store it in the container, measure again in low atmo... transmit after landing. Consider increasing the EC with some more batteries.

 

- Gilly landerprobe:

Landing on Gilly is more like docking when 2km away from a target

Reduce the amount of monoprop, a FL-R10 tank is enough. The reaction wheel of the HECS is strong, remove the 4-way thrusters and put 2 or 3 monothrusters beneath the lander. (They wont get ripped off when you decouple)

Bet you are still able to lift off from Gilly after landing again, having still a comsat for free.

(Maybe its just the view angle - are a thermometer etc. on the Gilly lander too?)

Edit: are there batteries on the lander?

 

- Propulsion:

add 2 Goo and 2 Science Jr. to it. You want the science from high over and near Eve too

 

If you have done all suggested changes the mass of the vessel should still be equal or less than your design. 

Maybe a bit expensivier - but you ll get MOAR SCIENCE!

Edited October 30, 2017 by Draalo
Infos added

[Cpt Kerbalkrunch]

All good advice above. I thought the same thing about the chutes. The 2 radial chutes are fine (I'm assuming you have them for symmetry because you couldn't attach the Mk16 to the top). The drogues aren't really hurting much, mass-wise, but you can dump them to save space for more equipment. I think I'd go with an extra battery, as @Draalo said (Eve is a large planet; the data you send back will be lengthy, especially if you had the atmosphere gadget: though I think now you can send info in pieces, so it might not matter).

And as @Laie said, you might consider a larger shield or there's a good chance you'll lose some equipment on the way down. As an alternative (possibly for another time; I'm not suggesting you redesign your entire mission), you can fit everything you need for this mission inside a 2.5m service module. It'll hold a probe core, battery, extendable solar panels, and all the science equipment inside. With a heatshield on the bottom and a parachute on the top, you'd have a fully operational probe-in-a-can.

Anyway, I think you'll be successful. The cheapskate approach is lookin' pretty good. 

 

I wanted add (and you may have already done this so, if you have, just disregard), that if it's possible, you might think about bringing the orbital survey scanner as well. I imagine this mission is a prelude to your manned mission, so it might be helpful to at least have the ability to mine ore. You can set up refueling operations on Gilly, as @bewing said earlier, or, as I did on my first (successful) manned Eve mission, land your ship empty. Drill, refuel, dump the equipment, and take off. Even if you don't plan to do any of these things, it might help to at least have the ability. You never know how things might get Kerbaled up later. 

 

Edited October 30, 2017 by Cpt Kerbalkrunch

[Gilph]

Also, if this is not a one way and you wish to lift off again, consider this great mod.

 

[Geschosskopf]

13 hours ago, The Flying Kerbal said:

I've tried this so many times now I'm beginning to think it's only a proper, dedicated heat shield which can take the heat of slamming into that reinforced concrete wall Eve pretends is an atmosphere?

Yeah, pretty much.  You need a proper heatshield at Eve.  And it helps if it's wider than whatever's landing.  IOW, use a 2.5m shield on a 1.25m stack, etc.  However, you can skimp on the ablator.  Most heatshields have enough for 2 or 3 Eve re-entries (for the unlikely event the same ship will do that many).  So if you're worried about weight, reduce the ablator by 1/2 and see if you still survive.  You probably will.

Capturing into a low Eve orbit by thrust alone typically costs about 1200-1500m/s IIRC.  Not really a big deal if you've already got an LV-N transfer stage.

 

13 hours ago, The Flying Kerbal said:

So my second question is, is there anything about not being in an equatorial orbit with Eve which increases the chances of the mission going sour?  What I intend to do is basically the same as what I did at Duna, a small lander parachutes down to the surface of the planet, while an RCS powered lander lands on its moon?

This is the sort of thing I frequently do myself.  I typically send the Gilly lander and the Eve lander as separate ships, however.  This greatly simplifies everything:   mission planning, ship design, and ship size/cost.  If you send them both out on the same ship, you not only need a bigger lifter but you need a bigger transfer/OMS stage because either the Eve lander has to be dragged around to line up with Gilly, so you're maneuvering more mass.  Plus the ship design is all complicated with various separate modules that have to separate.  So I find it better to make each a specialized ship and have them go their own ways.

Not being in an equatorial orbit at Eve has no real effect on anything, UNLESS you're trying to hit a specific point when you land there.  Then you have to wait until that point passes under your inclined orbit.  Also, if the ship in Eve orbit is coming home, it'll likely need a small amount more dV for the Kerbin transfer if it's in an inclined orbit, but not enough to worry about.

The Eve lander doesn't need engines.  It just needs its science instruments, a radio, and batteries/solar panels.  Plus its heat shield and chute.  If you keep it as light as possible, it will slow down quickly without getting very hot or using much ablator.  You can deorbit it with the transfer stage, then drop the transfer stage and watch it explode on the way down    

If you make the lander small enough, you can probably de-orbit it with a few Sepratrons.  This would allow you to stack 2 or 3 such micro-landers on the same transfer stage.   Then being in an inclined Eve orbit would be beneficial as you'd be able to drop these landers on different biomes.

 

[The Flying Kerbal]

More brilliant answers!  In no particular order, I never thought of taking two Science Juniors to Gilly and think it's definitely worth looking at very seriously.

I did try landing on Eve using just the two radial Mk16's, but the thing landed in highlands at 11.2m/s, smashing the heat shield and taking out the solar panels.  I was surprised it hit so hard having read many different posts on this forum about how efficient parachutes are in Eve's atmosphere.  So I replaced the two drogue 'chutes and decided to it play safe.  I also moved the panels slightly higher so they were no longer resting on the top of the heat shield.

A larger heat shield would be the answer for sure, but unfortunately I haven't unlocked anything bigger than the 1.25.  Maybe I could shoot a mission or two to the Mun or Minmus and trawl some more science.  I've already got two vessels in LKO, one for each of the two moons, which I refuel and send repeatedly to do just that.  And the lander sitting on Ike has a ton of RCS propellant still on board, I could move it to another biome or two and harvest more science in that way.

No orbital survey scanner this trip, it too has still to be unlocked, indeed all the science you see is what's available at the moment.

I looked at using the S-16 antenna, but I couldn't find anywhere to squeeze it in unfortunately.  If I thought I could get away without the drogue 'chutes it would make life a bit easier, I still think there was something freaky about that 11.2m/s I mentioned a moment ago..?

Yes, my Gilly lander does have a battery but I've got one awful bad habit - well one of many actually (you would take a heart attack if you saw me launching into an LKO) - I tend to hide things like batteries, small mono propellant tanks, etc. inside the bodies of my spacecraft by offsetting them out of sight.  There's no real advantage to this except it makes the vessel look a bit sleeker.  I suppose that's a bit of a faux pas on my part... 

Two rockets sounds like a good idea and I'd definitely consider it, but my Duna mission was such a total success (I mean guys... I'm seriously proud and chuffed to bits with that one!), that I don't want to make such a radical change for Eve.  That's a brilliant idea about stacking two or three small Eve landers on the rocket, that one will DEFINITELY need further looking into!

Anyway guys, it's time I was getting some shut eye.  I apologise for not addressing every point made and please don't think my lack to do so is in any way a snub; every suggestion and piece of advice is greatly appreciated and I thank all of you for responding.

[Cpt Kerbalkrunch]

I thought 2 chutes would work for such a tiny probe (you got batteries offset in there or bricks? ), but Eve does have crazy-high gravity, so I guess I'm not too surprised. Now that I think about it, I twice accepted "mine ore from Gilly and deliver it to Eve" contracts. The money was good, and I have a mining operation on Gilly, so I couldn't resist. It was about 3,000 ore for each (which is extremely heavy), but I used the inflatable heatshield (which is extremely draggy), so getting it to the surface was a bit easier than I thought it would be. I'd have to check when I get home tonight to see how many chutes I used for that one. Probably a lot. I've learned hard lessons on Eve.

Anyway, it sounds like your mission's ready to rock. For what you have available, it looks like a pretty solid design and overall plan. This should also give you some idea of what you're going to need for your manned forays in the future. The science you gain will keep your space program moving forward, so hopefully all goes well. Drop us a postcard from Eve.