Eve not so hard after all

[Zosma Procyon]

Why didn't anyone tell me how easy it was to pull off atmospheric insertion on Eve. I'm my experimenting for a series of large launches to the the second planet, I've been experimenting with heat shield configuration to survive the heat of insertion, and trying to determine the amount of delta-v required for a deorbit burn. Anyone familiar with my recent posts will see that i got the heat shields figured out: four in front and a wider arrangement of nine in aft to maintain balance. 

But it turns out that I was massively overestimating the delta-v required to deorbit my behemoth lander, by a factor of 4 or 5, maybe 10. My first successful attempts used between 1800 and 2400 m/s from initial orbits of 186 km. Worked, but the crafts experienced worryingly high G-force. Then I tried a 1000 m/s burn from 100 km. This ended in failure due to one of my cats walking on the keyboard. I'm not sure what keys her pressed, but it put the well balanced lander in a flat spin which broke it up. Given the my lander masses more than 800 tons, you can imagine these attempts required a metric f*ckton of fuel. Several Saturn Vs worth. I was racking my brain on how to get the rocket off Kerbin and to Eve.

But just now I tried a far smaller deorbit stage. Two of the largest stock tanks and seven vector thrusters. I also spammed the large panel radiators everywhere they would fit on the lander. The deorbit stage was rated at 430ish m/s, but I used less than half off that. My angle of insertion was very shallow. And the entry went flawlessly. G-force barely touched the red line, heat shields didn't go beyond yellow, it was over all a much safer operation. 

With all the talk of how hard it is to land on Eve, you'd think someone would mention how little you need to burn to get down. 

[Fearless Son]

Eve has always been pretty easy to land on.  Aerobreaking on Eve from orbital velocities (or, Kod help you, trans-orbital velocities) is what has gotten dangerous since 1.0 came out.  

[Geonovast]

Getting off of Eve is the hard part.

[Cpt Kerbalkrunch]

24 minutes ago, Zosma Procyon said:

With all the talk of how hard it is to land on Eve, you'd think someone would mention how little you need to burn to get down. 

Um, yeah. I think you got mixed up somehow. A guy in his first week in the game can land on Eve. Not really worth posting about unless it was something special. Bringing your ship back to orbit is where the difficulty lies.

[Geschosskopf]

1 hour ago, Zosma Procyon said:

With all the talk of how hard it is to land on Eve, you'd think someone would mention how little you need to burn to get down. 

Tylo is hard to land on.  Eve is hard to launch from (although not so much anymore---20-ton landers are all the rage now).

In general, though, the smaller the de-orbit burn, the shallower you come down.  This means 2 things:

• Slower deceleration so lower G loads
• Higher horizontal entry speed which is maintained longer, so you burn longer, but with a lower max temp it seems than with a steeper descent.

I find that from just above the atmosphere on any planet, a good compromise between the above is to do a de-orbit burn so that my trajectory will hit the ground about 1/4 to 1/3 of the way around the planet from where I do the burn.  This seems to be a good angle for every planet with an atmosphere.  Where you actually hit the ground doing this, of course, varies due to atmospheric densities and heights being different.  On Eve, if you aimed 1/4 of the circumference ahead of you, you'll likely hit only 1/8 of the way around due to the air being so thick.  On Kerbin and Laythe, you fall about 15% short of the mark.  On Duna, you almost make it to where you aimed.

 

[Human Person]

Everybody says how landing is easy and ascent being the hard part. I disagree. Landing a small one-way craft is easy, yes, but landing a big craft capable of returning to orbit is hard, harder than the ascent in my opinion. I measure hardness in time it takes to figure out a design that works. Throwing something together with enough Delta v and TWR is quickly done, figuring out the aerodynamicis to make it survive reentry and how many parashutes you need, that’s the hard part, not to talk about how many landing legs and with or without a small burn to ease touchdown.

Edited January 12, 2018 by Physics Student

[Cpt Kerbalkrunch]

1 hour ago, Physics Student said:

Throwing something together with enough Delta v and TWR is quickly done, 

I think this depends on how you play. I'm not sure how it is if someone uses mods or calculators of some sort, but I can tell you that (for me at least) by playing simply through guesswork and experience, it actually isn't quick or easy. Obviously, this is just a personal preference that isn't necessary, but if you play this way it takes awhile; and quite a bit of testing is necessary (again, for me at least). It's why, no matter how many times I go to Eve and back, it is always tremendously satisfying.

Also, there's quite a bit of a difference in difficulty between landing a ship, and landing a ship that is capable of getting back to orbit, as you alluded to.

Edited January 12, 2018 by Cpt Kerbalkrunch

[Geschosskopf]

2 hours ago, Physics Student said:

Everybody says how landing is easy and ascent being the hard part. I disagree. Landing a small one-way craft is easy, yes, but landing a big craft capable of returning to orbit is hard, harder than the ascent in my opinion.

Given that you can get off of Eve with a 20-ton, 2-stage lander with drop tanks these days, putting such a ship on Eve to begin with isn't hugely difficult.  And because of this, Eve has lost a lot of its challenge. 

Back before air got "de-soupified", you really did need about 15K-16K m/s to get off Eve, so the lander had to be this ridiculously massive thing with incredibly complex asparagus staging.  Landing one of those on Eve was indeed difficult (although at least you didn't have to worry about heat).  Thus, doing this was considered a big challenge and YouTube got filled up with folks showing off how they'd done it.  These videos are still there, of course, thus perpetuating the belief that Eve landers still have to be monstrosities, although this is no longer true.

[NSEP]

Yeah but everybody knows thats the easy part of Eve. So easy that nobody even bothers with it, because the other part of Eve is so damn hard.

The Hard part is getting out of there!

[ARS]

Atmospheric insertion on eve? Well just attach a bunch of parachutes and tons of heat shields. Let it go down the atmosphere by itself. It's easy, just like usual reentry. What makes eve infamous among KSP players isn't about how to land on it, but how to leave it. The drag and gravity that must be overcome is absolutely ridiculous which is why you will always seen a video about eve return and almost none about eve insertion

Though in my opinion, tylo is even harder since the lack of atmosphere and high gravity means you must slow down using rocket fuel instead parachutes

Edited January 12, 2018 by ARS

[GoSlash27]

14 minutes ago, ARS said:

The drag and gravity that must be overcome is absolutely ridiculous

And also the atmospheric density, which wrecks your engine's I_sp and thrust. Landing something on Eve is easy. Launching from Eve is hard. Landing something that is capable of launching from Eve is *very* hard.

Best,
-Slashy

Edited January 12, 2018 by GoSlash27

[Cpt Kerbalkrunch]

7 hours ago, Geschosskopf said:

Given that you can get off of Eve with a 20-ton, 2-stage lander with drop tanks these days, putting such a ship on Eve to begin with isn't hugely difficult.  And because of this, Eve has lost a lot of its challenge. 

Back before air got "de-soupified", you really did need about 15K-16K m/s to get off Eve, so the lander had to be this ridiculously massive thing with incredibly complex asparagus staging.  Landing one of those on Eve was indeed difficult (although at least you didn't have to worry about heat).  Thus, doing this was considered a big challenge and YouTube got filled up with folks showing off how they'd done it.  These videos are still there, of course, thus perpetuating the belief that Eve landers still have to be monstrosities, although this is no longer true.

I bought the 1.0 release, so I don't know much about the early game. For today's game, from pics I've seen as well as my own experience, Eve vehicles vary in size due mostly to the number of Kerbals onboard. If someone is able to make a multi-Kerbal ship (in proper command pods) that is small, easy to land, and easy to get back to orbit, their design work is extremely impressive.

Edited January 12, 2018 by Cpt Kerbalkrunch

[Geschosskopf]

3 hours ago, ARS said:

Though in my opinion, tylo is even harder since the lack of atmosphere and high gravity means you must slow down using rocket fuel instead parachutes

Tylo is the exact opposite of Eve, in that it's hard (and thus dangerous) to land on but very easy to leave.

 

1 hour ago, Cpt Kerbalkrunch said:

I bought the 1.0 release, so I don't know much about the early game. For today's game, from pics I've seen as well as my own experience, Eve vehicles vary in size due mostly to the number of Kerbals onboard. If someone is able to make a multi-Kerbal ship (in proper command pods) that is small, easy to land, and easy to get back to orbit, their design work is extremely impressive.

True, the 20-ton Eve landers are for 1 Kerbal, but at least they can get an actual Mk 1 pod back to orbit with the Kerbal still inside, without the Kerbal having to finish circularizing with his jetpack.  Multi-Kerbal pods are heavier per Kerbal than the Mk 1, so the lander is rather bigger.  Still, they're way smaller than the 1-seat behemoths of ancient days.  However, I would probably use a 1-seat lander for each Kerbal, as both easier and probably cheaper than trying to put them all in the same ship.

[ARS]

12 minutes ago, Geschosskopf said:

Tylo is the exact opposite of Eve, in that it's hard (and thus dangerous) to land on but very easy to leave.

My problem with Tylo is that, during landing, using rocket fuel is mandatory for safe touchdown. However, fire the thruster too early and it ends not having enough to leave, or fire too late and crash to the ground. So far I've been doing 5 Eve mission (3 success, 1 failure, 1 unmanned permanent probe) but only 1 Tylo mission (Fail)

[Geschosskopf]

Just now, ARS said:

My problem with Tylo is that, during landing, using rocket fuel is mandatory for safe touchdown. However, fire the thruster too early and it ends not having enough to leave, or fire too late and crash to the ground. So far I've been doing 5 Eve mission (3 success, 1 failure, 1 unmanned permanent probe) but only 1 Tylo mission (Fail)

Tylo is unique in that the descent profile is highly dependent on the design of the lander.  There are many possible ways to build a Tylo lander with enough dV and TWR for the job, but each one needs to start at a different altitude and come down at a different angle.  This is largely a function of TWR.  The lower this is, the more time the lander needs to slow down to a safe landing speed before reaching the ground, and vice versa.  This time is provided by distance, so in general, landers with lower TWRs need to start higher and/or come down at a shallower angle.  This starting altitude is often MUCH higher, like several hundred km, than folks are used to at other planets.

This is what trips up a lot of folks.  They build a lander that, on paper, has the stats to do the job.  Then they put it in the usual 50-100km orbit they use at other airless bodies, and crash because they can't slow down enough in the time provided by this low altitude.  So they think the lander's design is wrong and get frustrated rebuilding it many times without success.  But if they instead took the original design and experimented with different descent profiles, they'd probably find a way to make it work, because it does, after all, have the stats to do the job.

[Cpt Kerbalkrunch]

1 hour ago, Geschosskopf said:

Tylo is the exact opposite of Eve, in that it's hard (and thus dangerous) to land on but very easy to leave.

 

True, the 20-ton Eve landers are for 1 Kerbal, but at least they can get an actual Mk 1 pod back to orbit with the Kerbal still inside, without the Kerbal having to finish circularizing with his jetpack.  Multi-Kerbal pods are heavier per Kerbal than the Mk 1, so the lander is rather bigger.  Still, they're way smaller than the 1-seat behemoths of ancient days.  However, I would probably use a 1-seat lander for each Kerbal, as both easier and probably cheaper than trying to put them all in the same ship.

Agreed. I've seen some really impressive designs with the Mk1 that I wouldn't he thought could reach orbit. These guys seem to have made good friends with aerodynamics. My own method is usually to thumb my nose at it and just try to power through. My first 2 successes were 2-Kerbal designs with the combo of Mk1 command pod and lander can. It actually wasn't so bad. However, just jumping up to the Mk1-2 was a huge difference. The ascent vehicle was pretty hefty. Which meant the lander itself freakin' huge.

For @ARS, it's funny how some things give some people trouble, and other things give other people trouble. Your success rate on Eve is excellent. For me, if you count all the testing, I must have at least 100 failures. But on Tylo, I've been pretty successful. I think my penchant for larger, multi-Kerbal vessels actually helps me there. I usually have larger engines than a normal lander would, and am able to stop myself in time. As @Geschosskopf said, be able to land is one thing. Being able to land in time is what she's the difference on Tylo. I like to start with a nice 30 x 30 orbit before beginning my descent. And I definitely try to get just a single deceleration burn if possible. You fall so fast that, if you kill your velocity too high up, you just build it back up again.

[Freds]

Almost all my missions to Eve are unmanned and one way only - only one time i done a manned mission , and it was incredible difficult to bring the Jeb and Bob back.

I Just put everything inside a 2,5M service bay, install heatshields on both sides and its done! (It is a very simple configuration: It is just the service bay with a 2.5 Heatshield and a 10M heatshield on each side. Inside the service bay there is a probe core, Communotron 16-S, 2 fuel cell array, a ROUND-8 Toroidal, and all the science equipament i can fit in it.)  This configuration is so light and the heat shielding is powerful enough to permit direct atmospheric entry from interplanetary transfer - just need to enter the atmosphere with periapsis near 55Km - no need to orbital capture burn.

 When i want to land in a specific location, i use a Mk3 Karbonite powered aircraft, equipped with parachutes and a science rover in the cargo bay.

When it is near my landing site, i just activate the parachutes and it lands! After the landing, all i need to do is to open the mk3 ramp and decouple the (useless) rover..... 

[Geschosskopf]

18 minutes ago, Cpt Kerbalkrunch said:

Being able to land in time is what she's the difference on Tylo. I like to start with a nice 30 x 30 orbit before beginning my descent. And I definitely try to get just a single deceleration burn if possible. You fall so fast that, if you kill your velocity too high up, you just build it back up again.

Yeah, there are 2 basic approaches to landing on Tylo.  One is to start low and fast, and kill off horizontal speed while keeping vertical speed low.  The other is to start high and slow, and do a long powered descent, which has to be timed so that you run out of speed just before you run out of altitude and fuel.  The former is I think is easier to fly manually, but you have very little control over where you end up on the surface.  The latter can be quite difficult to do manually (although MJ usually does a pretty good job if you give it workable starting conditions), but allows you to land reasonably close to a chosen target.

[DAL59]

On 1/11/2018 at 6:55 PM, Zosma Procyon said:

This ended in failure due to one of my cats walking on the keyboard.

! 

On 1/11/2018 at 6:55 PM, Zosma Procyon said:

Why didn't anyone tell me how easy it was to pull off atmospheric insertion on Eve. I'm my experimenting for a series of large launches to the the second planet, I've been experimenting with heat shield configuration to survive the heat of insertion, and trying to determine the amount of delta-v required for a deorbit burn. Anyone familiar with my recent posts will see that i got the heat shields figured out: four in front and a wider arrangement of nine in aft to maintain balance. 

But it turns out that I was massively overestimating the delta-v required to deorbit my behemoth lander, by a factor of 4 or 5, maybe 10. My first successful attempts used between 1800 and 2400 m/s from initial orbits of 186 km. Worked, but the crafts experienced worryingly high G-force. Then I tried a 1000 m/s burn from 100 km. This ended in failure due to one of my cats walking on the keyboard. I'm not sure what keys her pressed, but it put the well balanced lander in a flat spin which broke it up. Given the my lander masses more than 800 tons, you can imagine these attempts required a metric f*ckton of fuel. Several Saturn Vs worth. I was racking my brain on how to get the rocket off Kerbin and to Eve.

But just now I tried a far smaller deorbit stage. Two of the largest stock tanks and seven vector thrusters. I also spammed the large panel radiators everywhere they would fit on the lander. The deorbit stage was rated at 430ish m/s, but I used less than half off that. My angle of insertion was very shallow. And the entry went flawlessly. G-force barely touched the red line, heat shields didn't go beyond yellow, it was over all a much safer operation. 

With all the talk of how hard it is to land on Eve, you'd think someone would mention how little you need to burn to get down. 

 

[Xyphos]

Getting to Eve requires the least dV for any celestial body, from Kerbin.
Inserting into Eve is easy if you know how to properly manage heat
Getting OFF of Eve is the hard part, your lander will need a minimum of 8,000 dV from sea-level, and a high enough TWR to lift off the surface.

However, if you check my signature below, you'll find Mount EveRest, the highest point on Eve at an altitude of 7540 meters above sea level, making it the best place to land, tho tricky.
What makes it the best landing site, is because it's so high up, the atmospheric pressure isn't as bad as it would be at sea level, which gives you a small boost to thrust and decreases the dV requirement to return to orbit.
Since Eve's rotational speed is about 55 m/s, you won't gain any benefit from landing near the equator.

Eve's dense atmosphere makes wings and parachutes more effective than they would be on Kerbin, and winged craft is the best mode of transportation, provided you have the means of propulsion, there's no oxygen for jet engines to work.

As for Tylo, you'l need a two or three stage lander to land and return, the high gravity and no atmosphere will require at least one jettisoned descent stage. don't overlook the oscar-b tanks, they're quite useful as you'll see in my Jool 5 video if you click the picture in my signature below.