Eve Tips?

[StrandedonEarth]

I really have to get around to doing an Eve ascent mission, as I haven't done that since 0.24 or so. Some good reminders and tips in this thread. But if you really want to do it with a spaceplane...

Spoiler

 

Edited April 3, 2018 by StrandedonEarth

[GoSlash27]

1 hour ago, StrandedonEarth said:

^ Truth. Getting to Eve is one of the easiest things to do in KSP. Getting *back*, OTOH....

[Lego_Prodigy]

If you can tell me how to post images, i will show you guys what I used to get to eve, a spaceplane that was exceedingly simple for what I did. Unfortunately, I didnt have enough fuel to power an injection maneuver, and I had to use cheats to actually explore eve.

[-Velocity-]

6 hours ago, Foxster said:

That craft is rather over-engineered.

The biggest battle on Eve is with drag. You will lose loads of dV for every bump, over-sized tank, stack, sepratron, fin, engine, strut and whatever else you bolt on in effort to get the dV numbers up. That leads to the craft ballooning. Whereas the way to go is take stuff away. 

This 25t stock craft can lift 4 Kerbals in chairs inside the fairing to Eve orbit from sea level...

 

I admit it's possible that the rules have changed significantly since I last played, but if they changed this much, I am extremely surprised.  The rule I always heard- and that I experimentally found to be roughly true- was you need 12000 ms dV to get to orbit from sea level (with some safety margin).  This craft only has a delta-V of 6000 m/s!!!   You mean to say that they changed the game's aero model so much that you can almost entirely negate drag?!

What is at the end of the side tanks? 

How does one fly this thing?  At maximum thrust?  You go from sea level to orbit in less than TWO MINUTES?!  Because you certainly don't have enough delta-V to make it to orbit at TWR = 2.  If you have essentially zero drag, though, it should work.

Oh, I finally figured it out.  That's a small circular intake.  Shouldn't that be draggier?

Edited April 4, 2018 by -Velocity-

[StrandedonEarth]

33 minutes ago, -Velocity- said:

The rule I always heard- and that I experimentally found to be roughly true- was you need 12000 ms dV to get to orbit from sea level

As I said earlier, I haven't done Eve lately, but IIRC after the 1.0 aero-and-heat revamp, I heard that the dV required dropped to around 8-9 km/s. I'm not sure where you got 6km/s from, if you were building your own copy, did you set up the asparagus and staging properly? And the intakes are supposedly one of the lower-drag parts out there, or so I've heard (again, I haven't played with them).

[-Velocity-]

Just now, StrandedonEarth said:

As I said earlier, I haven't done Eve lately, but IIRC after the 1.0 aero-and-heat revamp, I heard that the dV required dropped to around 8-9 km/s. I'm not sure where you got 6km/s from, if you were building your own copy, did you set up the asparagus and staging properly? And the intakes are supposedly one of the lower-drag parts out there, or so I've heard (again, I haven't played with them).

Well, I hope so.  The aspargus staging is strange, the smaller tanks go first according to the arrows on the fuel lines, but yea, 6 km/s.  But wow, only 8-9 km/s?!?!

[GoSlash27]

2 hours ago, Lego_Prodigy said:

Unfortunately, I didnt have enough fuel to power an injection maneuver, and I had to use cheats to actually explore eve.

Ah, but if you're using cheats to get there, then the design of the vehicle itself doesn't matter. You can "cheat" a capsule to Eve with no engines or fuel whatsoever. And as I said earlier, getting there is the easy part. Eve is the easiest planet in the system to get to. Unfortunately, it's also the most difficult planet to get home from.

If you're cheating, then use whatever vehicle you like, 'cuz it doesn't matter. But if you're trying to design a vehicle that will actually do the job, then a spaceplane is the worst possible vehicle you could use.

Best,
-Slashy

 

[-Velocity-]

7 hours ago, Foxster said:

That craft is rather over-engineered.

The biggest battle on Eve is with drag. You will lose loads of dV for every bump, over-sized tank, stack, sepratron, fin, engine, strut and whatever else you bolt on in effort to get the dV numbers up. That leads to the craft ballooning. Whereas the way to go is take stuff away. 

This 25t stock craft can lift 4 Kerbals in chairs inside the fairing to Eve orbit from sea level...

 

 

I just tried your design.  I cheated it with infinite fuel to Eve and landed it real quick.  It doesn't get close to making orbit from 1.6 km ASL, either with the throttle firewalled or by carefully controlling the throttle to TWR = 2.  Are you sure you didn't mean it could make it to orbit from 5 km altitude, not sea level?  

Is it right to have the smaller side tanks stage first?!  Please upload a craft file.  Also, the small circular intakes ARE there, they are buried under the ground for some reason.

By the way, this is with 4X xenon tanks under the fairing.  4 xenon tanks weigh as much as 4 kerbals.

I can't see how I could be flying it wrong, I don't see how there could be a happy middle ground between firewalling the throttle and controlling it to TWR = 2 where this thing makes it to orbit.  Your picture does clearly show the fuel going from the small tanks to the larger side ones...  There are 20 oscar-b fuel tanks in my copy's long side tanks and 10 in the short side tanks.  I assume the upper stage engine is an LV909 or whatever that thing is called (1.25m short, high vacuum ISP engine with 50 kN max thrust).

 

Edited April 4, 2018 by -Velocity-

[Cpt Kerbalkrunch]

This one works from sea level, as well. Single Kerbal, direct ascent return to Kerbin. Not sure if these newer designs really count as "stock" anymore. I made use of MH parts. Most notably, the engine plate. It really is a fantastic add on to the game; allowing for engine clustering. 

 

 

Still heavy at about 150 tons, but that's pretty light for me. And as I said, it will take you from Eve sea level back home to Kerbin without refueling. And this doesn't matter at all, but I'll mention it anyway cuz it made me kinda proud. For a guy who uses the trial and error method, I actually nailed this in one shot. Second launch, though. First time I forgot to add the Delta Deluxe Winglets on the 2nd stage. As you can imagine, it flipped immediately when I staged it. The tougher part with tall, single-fuselage ships is often the landing. Chutes, drogue chutes, landing engines, and tons of shielding are necessary. Always an adventure. 

 

And looking at @velocity's screenshot above me, I am once again overcome with greed and desire upon seeing the KER screen open. I would just about kill to have all that info available. One day, I'm finally going to give in and join the modern world. 

[Foxster]

With some precise flying and a very low drag craft it is quite possible to make Eve orbit with <6000 dV from sea level. It can't be done though with most people's craft and with MJ or best-guess flight profiles. It can be done manually with care and I have also managed to automate it using the GravityTurn mod. 

The "secrets" are:

Reduce drag losses to the absolute minimum through the use of a small number of thin stacks, eliminating everything possible. 

Control the throttle very carefully to limit Q to no more than about 220,000pa. My craft above uses full throttle for only the first few km and then is throttled back to 1/4-1/3 throttle until Q drops. 

AoA needs to be tightly controlled. You need it zero all the time except whilst making the initial gravity turn.

The altitude you start your gravity turn is critical, typically around 4km from a sea level launch. 

No two craft (or variants of the same craft) will have the same flight profile to orbit. You will need to be prepared to experiment with the Q limit, gravity turn start altitude, and the pitch of your initial turn. Getting this right makes the difference between getting to orbit or coming up 1000dv short. 

My craft above is at the bleeding edge of what is possible, it was built and flown for a challenge. It shows what can be done if you are prepared to spend hours tweaking the design and then the matching flight profile. It is not for everyone, with most preferring to build something that is a lot easier to fly. However, it does demonstrate the principles of low weight and low dV craft on Eve. Using similar principles you can make a craft weighing ~50-60t that is relatively easy to get to orbit.  

Edited April 4, 2018 by Foxster

[Foxster]

Just found that there is a fairing bug in 1.4.2 that won't be helping Eve craft. 

The part mounted immediately below the fairing will have enormous drag. 

|n my craft above that worked fine in 1.3, the drag of the tank just below the fairing gets into the 100s. This means the craft won't make orbit. 

I'm playing with parts to see if there's an alternative but it might be a matter of waiting for a bug fix. 

[Dafni]

5 minutes ago, Foxster said:

Just found that there is a fairing bug in 1.4.2 that won't be helping Eve craft. 

The part mounted immediately below the fairing will have enormous drag. 

|n my craft above that worked fine in 1.3, the drag of the tank just below the fairing gets into the 100s. This means the craft won't make orbit. 

I'm playing with parts to see if there's an alternative but it might be a matter of waiting for a bug fix. 

So this fairing drag in 1.4.2 is recognized as a bug and will be fixed? That would of course be appreciated. I was a bit baffled by the huge drag induced by fairings lately.

[Foxster]

13 minutes ago, Dafni said:

So this fairing drag in 1.4.2 is recognized as a bug and will be fixed? That would of course be appreciated. I was a bit baffled by the huge drag induced by fairings lately.

Dunno. I'll look for it in the bug tracker and add it if its not there. 

Oddly the fairing itself has zero drag but the part below it has enormous drag as though the drag of all the shielded parts was added to it. 

Update: Its already in the bug tracker with a status of "Being worked on". 

Edited April 4, 2018 by Foxster

[fourfa]

7 hours ago, Foxster said:

Dunno. I'll look for it in the bug tracker and add it if its not there. 

Oddly the fairing itself has zero drag but the part below it has enormous drag as though the drag of all the shielded parts was added to it. 

Update: Its already in the bug tracker with a status of "Being worked on". 

There's an exploit available right now until it's patched: Use both upward- and downward-pointing fairings, attached to each other, enclosing all parts of your craft.  Close the lower fairing on the engine bell.  Presto, you should experience zero aerodynamic drag.