Ascent profile for Eve

[davidpsummers]

I've managed to land the ship pictured on the surface of Eve.  Now to see if I can take off again.  One issue, is the ascent profile.  On Kerbin, you want to pitch over 45 degree at about 10,000 - 15,000 km.  Anyone have any experience on how far up it should be on Eve?

Using KSP 1.3

 

 

 

Edited October 23, 2019 by davidpsummers
Fixed image link

[Laie]

The answer is as straightforward as it is useless: it depends.

For starters: "pitch over 45 degree at about 10,000" is old info, from before KSP v0.90. Today, you still want to be pitched over to (more-or-less) 45° by the time you reach 10km, but you start the turn sooner, just a few seconds after liftoff, and more gently.

Now about Eve: Heat is much more of a concern during Eve ascents than on Kerbin. There is a strict speed limit in the lower/middle atmosphere:  starting at about 12km, anything that is faster than ~1200m/s will explode (with a sufficiently powerful rocket you can go faster below, only to instantly die at 12km). The limit only increases slowly, to perhaps 1400m/s@45km, when all of a sudden it goes away entirely.

That is the lower boundary for an ascent you can get away with: you want your ascent to be steep enough that you are close to, and preferably above, 50km by the time you reach an airspeed of 1400m/s.  And later on, you want to be above ~70km when you reach orbital velocity -- you may go 3000m/s@60km, but only for a minute or so.

Compared to what you can do on Kerbin, this is a rather steep ascent. Depending on TWR, you may go straight up for 3, 5 or maybe even 10km before you gently start tipping over. By the time you're 10 degrees off vertical, you're pretty much locked into your ascent. Let go of the controls if the rocket is aerodynamically stable, or turn on SAS-to-prograde if it isn't. If it doesn't work out, try going steeper on the next attempt.

Now, all of that said, it all depends on your launcher and how much TWR/dV you have in each stage. Some need to make steeper ascents, others have to take a shallow route and throttle down at some point in order to not burn up. Many cannot make it at all. From the screenshot, I cannot tell how much of that rocket is supposed to be the lifter, so I cannot be any more specific.

[The Destroyer]

It also depends on aerodynamics as well as TWR -  a skinny lander can punch through the atmosphere and accelerate out quickly better than a fat rocket can. See here as well.

 

 

[Fierce Wolf]

In my experience, go straight up, limit your engines or you will burn down. From 55 km and up, start turning very gently. Eve's atmosphere is unforgiving, it's better to get out of it soon and do your bussiness later.

[ManEatingApe]

Here's an Eve gravity turn ascent video that might help (fun starts at 1:35).
It's version 1.6 but I don't believe the atmosphere has changed since 1.3

• 10° at  3,000
• 20° at  9,000
• 30° at 16,000
• 45° at 25,000
• 60° at 38,000 (throttle back at this point to prevent melting)

 

 

Edited October 23, 2019 by ManEatingApe

[Foxster]

One thing that will help you with any kind of ascent profile with your craft is to put all that extra stuff (solar panels, parachutes, radiators, etc) on decouplers and dump them before lifting off. Eve is all about drag, so you want to eliminate anything at all that adds it. 

You will then be able to have a smaller, lighter craft and your options increase. 

Another tip is to use the Gravity Turn Continued mod to automate your launch so that you can figure out in a repeatable way a profile that will get your craft to orbit. You don't have to use it for your final launch but more as an in-the-simulator thing. 

Edited October 24, 2019 by Foxster