So what does it take to get off of Eve these days?

[RocketBlam]

Delta-V wise, what do you need to get to orbit from sea level on Eve in these 1.1.x days? Anyone know? Or do I have to go experiment myself?

[monophonic]

IIRC what I have seen suggests the raw dV needed is actually noticeably less, but you need to pack it in a lot more aerodynamic shape. Haven't been there nor done that though, so it's all second/third/... hand information.

[Signo]

As far as I have seen 1.0.5 crafts still work and they are less prone to overheating while ascending.

The required d/v should be almost the same as before. (more or less 6500+, with consistent TWRs, depending on the pilot's hand and the craft streamlining)

 

EDIT - I checked my craft and it has got 7811 m/s vacuum d/v (starting from 3322 at Eve sea level). I usually manage to reach a 110x110 orbit with a few spare fuel

Edited May 4, 2016 by Signo

[Superfluous J]

Hyperedit.

I'm not as lucky as @Signo is. My Eve ship that worked perfectly well in 1.0.5 required hours of work to get through the atmosphere to a landing in 1.1.2, and after hours of work trying to get it to take back off again, I've given up. I don't know exactly what's wrong or why it worked just fine in 1.0.5 and flies like a cow with broken legs in 1.1.2, but it has driven me to the point where I don't care if I never see the surface of Eve again.

[Signo]

I am currently using this design I clearly stole from Foxster with just a few tweaks of mine. Nothing really fancy. TBH I did not try it yet in 1.1.2, my last Eve trip was in 1.1.0.something.

 

[Nich]

Have a link to the original mission that just looks like it wouldn't make it lol @Foxster, @Signo

[Signo]

Well, I can not speak for Foxster, but I still have pics from my 1.0.5 attempt.

 

 

Edited May 4, 2016 by Signo

[Kerbinchaser]

5 minutes ago, Signo said:

Well, I can not speak for Foxster, but I still have my pics from my 1.0.5 attempt.

 

 

Nice attempt. I haven't gotten around to Eve yet though. I'm slowly working my way up the Kerbol system. I've only gone to Kerbin's 2 Moons. 

Edited May 4, 2016 by Lo Var Lachland

[Foxster]

One of the nice things about 1.1+ is having the big new heat shield. Before that, if you wanted to get a lander down, you either made it skinny enough to fit behind one heatshield or bolted a few together. Now there's room to stretch out a little more. 

Exactly how much dV you need obviously depends on streamlining and the altitude you launch from. Streamlining is pretty essential, you want a few skinny stacks. Even using a less draggy mk1 capsule rather than the lighter lander can make the difference as to whether you make orbit. I'd aim for 7500-8000 dV and see how it goes. It is possible to do it with less than 6000dV though.

Then there is your flight profile. Turn too soon and you will either lose the climb to drag or you'll heatplode. Turn too late and you'll need too much dV to finish orbit. I aim for 25-30km straight up and then a steep turn of about 80°. 

Update...

For interest, here's sea-level-capable 1.1 Eve lander weighing a tad over 40t...

Craft file: https://www.dropbox.com/s/59ekurg9541uclg/Eve%20lander%20v3%204%201_1%202.craft?dl=0

If anyone fancies trying it then the flight is something like...

1. Use the engines to de-orbit

2. Then deploy the heat shield AND air brakes

3. Drift down at almost any Pe. It will be hard to overheat with the big heat shield

4. Once below 200m/s deploy the chutes

5. At 1000m the chutes will fully deploy

6. Jettison the heat shield and it should drift down away from the craft. 

7. Deploy the landing gear

8. Land

Getting back to orbit is...

1. Decouple the chutes, ladders and air brakes

2. Launch and fly to orbit. If you want to use MJ then I suggest: Orbit altitude: 105km, Turn start altitude: 26km, Turn start velocity: 100,000m/s, Turn end altitude: 80 km, Final flight path angle: 1°, Turn shape: 80%.

3. You should find you have about 500-700m/s dV left by orbit, enough for a rendezvous 

 

Edited May 4, 2016 by Foxster

[Xyphos]

Eve has always made me wonder about the possibility of a new engine type: rocket-powered turbines;
it uses LFO fuel to power a turbine and uses the Atmosphere for extra thrust at low altitudes.

Edited May 5, 2016 by Xyphos

[Renegrade]

1 hour ago, Xyphos said:

Eve has always made me wonder about the possibility of a new engine type: rocket-powered turbines;
it uses LFO fuel to power a turbine and uses the Atmosphere for extra thrust at low altitudes.

I did once read about some type of rocket engine that uses the atmosphere as additional reaction mass (not for combustion, ie not a SABRE).  Not quite the same thing but it would have a similar effect, possibly.  I can't recall if it was a workable concept or not though.

[LameLefty]

1 hour ago, Xyphos said:

Eve has always made me wonder about the possibility of a new engine type: rocket-powered turbines;
it uses LFO fuel to power a turbine and uses the Atmosphere for extra thrust at low altitudes.

Well, in RealLife™, many liquid fuel rockets (early Delta family, Saturn, Soyuz, Atlas V, Falcon family ...) use RP1, highly-refined kerosene. Similarly, most jet turbine engines are optimized for some formulation of what was historically called Jet-A, also highly-refined kerosene.

So basically, that's already how jet engines work.

[Xyphos]

10 minutes ago, LameLefty said:

Well, in RealLife™, many liquid fuel rockets (early Delta family, Saturn, Soyuz, Atlas V, Falcon family ...) use RP1, highly-refined kerosene. Similarly, most jet turbine engines are optimized for some formulation of what was historically called Jet-A, also highly-refined kerosene.

So basically, that's already how jet engines work.

I already knew that. but that's not what I meant.

I meant, LFO in a combustion chamber to power a large fan in which the atmospheric pressure can be converted into thrust.

Edited May 6, 2016 by Xyphos

[LameLefty]

Just now, Xyphos said:

I already knew that. but that's not what I meant.

If you meant a variable-cycle engine like the theoretical SABRE or something, then you know we've already got RAPIERs in the game.

Did you mean something else?

[Xyphos]

I meant, LFO in a combustion chamber to power a large fan in which the atmospheric pressure can be converted into thrust.

imagine the 2.5m jet engine, but not air-breathing; it's LFO fueled but uses the surrounding atmosphere as a primary reaction mass.
this would make for a space-plane takeoff, where the atmosphere gets thinner and you can switch to normal rockets.

Edited May 6, 2016 by Xyphos

[LameLefty]

2 minutes ago, Xyphos said:

I meant, LFO in a combustion chamber to power a large fan in which the atmospheric pressure can be converted into thrust.

imagine the 2.5m jet engine, but not air-breathing; it's LFO fueled but uses the surrounding atmosphere as a primary reaction mass.

Hmm, basically a rocket-powered turbofan? If it's able to use atmosphere as the reaction mass, it ought to be able to dispense with the "O" part of the LFO and just be a jet, unless the atmosphere has no oxygen. Maybe a rocket-powered fan engine?

Edited May 6, 2016 by LameLefty

[Xyphos]

Exactly. non-airbreathing jet engine. it uses Liquid Fuel + Oxidizer (LFO) to power a fan to compress the surrounding atmosphere into a source of thrust.

[CheckYoStaging]

How high an orbit on kerbin requires the same Dv as a low orbit on Eve?  I've been testing my ships on a 100-120km orbit.

[LameLefty]

3 minutes ago, Xyphos said:

Exactly. non-airbreathing jet engine. it uses Liquid Fuel + Oxidizer (LFO) to power a fan to compress the surrounding atmosphere into a source of thrust.

 Let's be clear on terminology - "compression" of the air per se is not required for thrust. What IS required is MOVING the air, which is basically what a propellor does in an ordinary general aviation aircraft on earth. The thrust on a Cessna, for instance, is because of the mass of hair being pushed backward by the prop. Yes, there is some localized compression of the high-pressure air behind the prop blades pushing forwards, but there is an equal rarefaction (lowering of the pressure) of the air flowing across the top of the blades; the thrust is simply F=ma.

The only time you need or even really WANT compression of your reaction mass is in the case of a combustion process, where adding compression and then injecting fuel into the compressed air for combustion causes rapid expansion (and again, MOVING the air).  But if you're not using that air for combustion, compressing it is a waste of energy. Just move the air with a fan.

(DISCLAIMER: I am an actual aerospace engineer by education and former profession; this subject is pretty basic propulsion engineering but without knowing the background of the audience, it's hard to know how much detail to go into).

[Superfluous J]

13 minutes ago, CheckYoStaging said:

How high an orbit on kerbin requires the same Dv as a low orbit on Eve?  I've been testing my ships on a 100-120km orbit.

IIRC you need to be able to launch your ship into LKO, then Hyperedit it back down to the surface, and then launch THAT back into LKO. And if you have enough left over to escape Kerbin's SOI, you might - just might - be able to scrape your way into orbit of Eve.

[Xyphos]

okay, well... rocket-powered fan it is then. whatever.

the idea is that ISP on Eve at sea-level wouldn't be as efficient as flying a fan-powered plane to a certain altitude where normal rockets could then be used.

[CheckYoStaging]

1 minute ago, 5thHorseman said:

IIRC you need to be able to launch your ship into LKO, then Hyperedit it back down to the surface, and then launch THAT back into LKO. And if you have enough left over to escape Kerbin's SOI, you might - just might - be able to scrape your way into orbit of Eve.

Woa...  I'm waiting until I land on every body and return to download mods, so I'm just gonna have to launch one and see how far I can go.

[Superfluous J]

8 minutes ago, CheckYoStaging said:

Woa...  I'm waiting until I land on every body and return to download mods, so I'm just gonna have to launch one and see how far I can go.

Another thing you can do - if you want no mods - is to launch straight up. When the engines cut out, note the time and your velocity. Then 10 seconds later note the velocity again.

Your acceleration down due to gravity at the surface is 10m/s (about). Your acceleration at the end is 1/10th the difference in your two ending velocities. The average of those two numbers times how many seconds you burned is *about* how much you lost to gravity.

That number, plus your velocity when the engines cut out, is *about* your ship's total dV. This ignores several things about atmosphere (and the fact that acceleration due to gravity doesn't fall off in a linear fashion) but it's a good approximation.

You want that number to be at least 8000m/s.

Edited May 6, 2016 by 5thHorseman

[Glaran K'erman]

Actually since I am not committing to a career at this point I might as well try to do an Eve ascent. I do wonder what the difference between landing ASL or at some elevation makes in dV though...?

[Xyphos]

4 minutes ago, Glaran K'erman said:

Actually since I am not committing to a career at this point I might as well try to do an Eve ascent. I do wonder what the difference between landing ASL or at some elevation makes in dV though...?

Eve has a very dense atmosphere, rockets tend to loose effectiveness in atmospheric conditions due to the pressure pushing back on the thrust.
this causes the rocket to loose both thrust and ISP (the efficiency measurement)
Although possible to return to Eve's orbit from sea-level using rockets, it's definitely not efficient or practical,
which is why I suggest a new engine type, rocket powered fans (or even helicopter rotors)
to bring the vessel up to an altitude where rockets would be better suited.

DISCLAIMER: I do not claim to be an aerospace engineer, I'm just a guy who likes to tinker with things, and play sandbox games.

Edited May 6, 2016 by Xyphos