Any Eve Lander/Ascent designs?

[Der Anfang]

I'd like to see some 3 kerbal (or less, but not unmanned) landers. I want to see something that can both land and take off. Preferably, anything that is 100t or less. I'd also like to know if there are any design tips for a lander that might take of from at or near sea level on Eve. Command seats are allowed, as well. I built a successful Eve lander in .90, but after the update with the thrust/isp and new atmospheric models, it became well obsolete and unable to take off from Eve, particularly at sea level.

What kinds of design perks are necessary for something that takes off at or near sea level?

[Scarecrow]

I'm in a similar situation.  My Eve lander was built in 1.0.4 but I haven't tried it in 1.0.5 so I have no idea if it is still capable of completing the task.

[ManEatingApe]

By a happy co-incidence, I just rescued Zelbe Kerman from Eve's surface after 159 years!

Some tips from the experience:

• Asparagus staging is your friend
• Drag is your enemy, keep your design clean, pare away as many ladders, struts and landing gear as possible
• Vector and Aerospike are the best engine choices for initial stages, as they are the least affected by atmospheric pressure.
• Terrier is a good choice for final stage, 2nd highest ISP of any liquid fuel engine and light weight. However if your final stage is a very light command chair design, then the "Twitch" engine could be better.
• Be prepared to leap for it! You may run out of fuel before circularising - if it's close then try completing orbit on EVA (with the Navball in EVA mode this is easier now)

My design also included a science rover and came in at just under 40 tons (ascent vehicle only) for 1 Kerbal. It can make orbit from about 600m above sea level.

Full disclosure: Eve ascent is possibly the hardest thing in the game. After 2 failed attempts I gave in and used HyperEdit to test and refine my design for the 3rd attempt (but not for the actual mission itself). 

Screenshots behind spoiler tag here:

Spoiler

Ascent Vehicle Only. Each pair of tanks is a stage for 4 stages total. A terrier is stacked over the central Vector.

Ascent Vehicle, Rover and heat shield

Mission album here:

Craft file here

 

Edited December 22, 2015 by ManEatingApe
+ Craft file

[Der Anfang]

3 hours ago, ManEatingApe said:

By a happy co-incidence, I just rescued Zelbe Kerman from Eve's surface after 159 years!

Some tips from the experience:

• Asparagus staging is your friend
• Drag is your enemy, keep your design clean, pare away as many ladders, struts and landing gear as possible
• Vector and Aerospike are the best engine choices for initial stages, as they are the least affected by atmospheric pressure.
• Terrier is a good choice for final stage, 2nd highest ISP of any liquid fuel engine and light weight. However if your final stage is a very light command chair design, then the "Twitch" engine could be better.
• Be prepared to leap for it! You may run out of fuel before circularising - if it's close then try completing orbit on EVA (with the Navball in EVA mode this is easier now)

My design also included a science rover and came in at just under 40 tons (ascent vehicle only) for 1 Kerbal. It can make orbit from about 600m above sea level.

Full disclosure: Eve ascent is possibly the hardest thing in the game. After 2 failed attempts I gave in and used HyperEdit to test and refine my design for the 3rd attempt (but not for the actual mission itself). 

Screenshots behind spoiler tag here:

  Hide contents

Ascent Vehicle Only. Each pair of tanks is a stage for 4 stages total. A terrier is stacked over the central Vector.

Ascent Vehicle, Rover and heat shield

Mission album here:

Craft file here

 

WOW! That thing is small! O-o I was actually considering using a vector engine for a size-1 design, but I didn't know how to implement it because everyone knows that Vector is a fuel hog. Really impressive considering that it doesn't have to be a hulking behemoth to launch from near sea level. For ladders, isn't it easier to just design in the ladders for descent stage, and then pop them off with seperators for the ascent stage? Reduces drag and weight at the same time, but you're kerbal can enter and exit the vehicle any number of time after the descent and before the ascent.

 

Also, 159 years, lol. That poor guy! How much Delta-V did your design have? o.o

Edited December 22, 2015 by Der Anfang

[ManEatingApe]

On 12/22/2015 at 4:21 AM, Der Anfang said:

For ladders, isn't it easier to just design in the ladders for descent stage, and then pop them off with seperators for the ascent stage? Reduces drag and weight at the same time, but you're kerbal can enter and exit the vehicle any number of time after the descent and before the ascent.

You're spot on, there's considerable room for improvement there. Placing the ladders on the 1st stage was a timesaving compromise on my part - I couldn't work out a neat way to create a ladder structure in the shadow of the heat shield.

Another area for improvement is the nose cones. There's a thread somewhere that compares the drag of various nosecones in 1.0.5. I think the upshot was that practically anything is a better nosecone than the actual nosecones parts. The ramp intake for example is the same weight and has lower drag.

EDIT: This is incorrect, see post below comparing various nosecones

On 12/22/2015 at 4:21 AM, Der Anfang said:

because everyone knows that Vector is a fuel hog.

I wonder if the Vector got this undeserved reputation by being placed under Mk 1 stacks that it will drain terrifyingly quickly. 

It has a perfectly respectable Vacuum ISP of 315 and the joint highest ASL ISP of 295, so when used as designed for a lifting stage it's fine.

On 12/22/2015 at 4:21 AM, Der Anfang said:

How much Delta-V did your design have?

Delta-V calculations are little tricky as the ISP varies with height. I don't use any mods, but here's the figures from my trusty Google doc spreadsheet. The ISP figures are bit of a SWAG. The first (250) is a rough guess from what I remember, the 2nd (295) the Kerbin ASL ISP of the Vector, the 3rd (315) is the vacuum ISP of the Vector and the 4th (345) the vacuum ISP of the Terrier.

 

Lifting 3 Kerbals from the surface of Eve is bravely ambitious, I look forward to seeing your attempt!

Edited December 24, 2015 by ManEatingApe
Fact checking

[OhioBob]

8 hours ago, ManEatingApe said:

Delta-V calculations are little tricky as the ISP varies with height. I don't use any mods, but here's the figures from my trusty Google doc spreadsheet. The ISP figures are bit of a SWAG. The first (250) is a rough guess from what I remember, the 2nd (295) the Kerbin ASL ISP of the Vector, the 3rd (315) is the vacuum ISP of the Vector and the 4th (345) the vacuum ISP of the Terrier.

FYI, the ISP of the Vector is...

Pressure (atm.)	Specific impulse (s)
5	193
4	220
3	246
2	271
1	295
0	315

 

[ManEatingApe]

Thanks @OhioBob, those figures are lower than I remember, Eve's atmosphere is so brutal!

The Eve wiki page is still listing dV needed to reach orbit from sea level as 11kM/s, though with 1.0.5 aero changes that should be lower now.

If you would like any further inspiration @Der Anfang, check out this thread here: http://forum.kerbalspaceprogram.com/index.php?/topic/118750-post-10-lightest-sea-level-eve-ascent-challenge/ 

[OhioBob]

5 hours ago, ManEatingApe said:

Thanks @OhioBob, those figures are lower than I remember, Eve's atmosphere is so brutal!

KSP doesn't figure ISP correctly.  In the game, ISP follows a curve that is defined in engine configuration files.  In real life it is a simple straight line function.  If the ISP drops 20s from vacuum to 1atm, it should drop another 20s for each additional 1atm pressure.  This is one of the few places where real life is easier than the game.

[Der Anfang]

9 hours ago, ManEatingApe said:

Thanks @OhioBob, those figures are lower than I remember, Eve's atmosphere is so brutal!

The Eve wiki page is still listing dV needed to reach orbit from sea level as 11kM/s, though with 1.0.5 aero changes that should be lower now.

If you would like any further inspiration @Der Anfang, check out this thread here: http://forum.kerbalspaceprogram.com/index.php?/topic/118750-post-10-lightest-sea-level-eve-ascent-challenge/ 

Do you still need 11k dv or no? What do  we need now? I remember for Kerbin we needed about 4.2k, now I can get by with roughly 3.5k.

[OhioBob]

24 minutes ago, Der Anfang said:

Do you still need 11k dv or no? What do  we need now? I remember for Kerbin we needed about 4.2k, now I can get by with roughly 3.5k.

I haven't launched from Eve since version 0.90, but, from what I've heard, I believe the new number is somewhere around 7000-8000 m/s.  Engine selection is very important now because ISP drops significantly at atmospheric pressures above 1 atm (pre-1.0, ISP never dropped below its sea level value).  The best engines for use at low altitudes on Eve are the Aerospike and the Vector.

[ManEatingApe]

1 hour ago, OhioBob said:

from what I've heard, I believe the new number is somewhere around 7000-8000 m/s.

That feels about right. Adding up my lander stages (for simplicity using the Vacuum ISP numbers) and adding in 300 m/s from 1/2 an EVA jetpack (my unofficial final stage!) gives 7,637 m/s to reach orbit from 200m above Eve sea level.

So if you budget at least this, and are careful with minimising drag and with engine choice (Aerospike or Vector) as OhioBob mentions, then you should be fine.

Edited December 23, 2015 by ManEatingApe

[Der Anfang]

7 hours ago, OhioBob said:

I haven't launched from Eve since version 0.90, but, from what I've heard, I believe the new number is somewhere around 7000-8000 m/s.  Engine selection is very important now because ISP drops significantly at atmospheric pressures above 1 atm (pre-1.0, ISP never dropped below its sea level value).  The best engines for use at low altitudes on Eve are the Aerospike and the Vector.

That's a big number, but that's actually not too bad considering that you'd be using aerospikes, mostly. 7, 8k dv allows lot more freedom for lighter landers, even at sea level. It's mainly the Vectors that would be the problem, but you'd only need their thrust to take you up to about 10-15 km before you need to discard them, and even on Eve their thrust is OP for a smallish lander. I too have only ever launchd a successful lander once... I think it was in .24 or .90. It's interesting how the new aero models allow us less dv for this. Even then, Eve is really Brutal; You can't really rely on the old size 1 engines anymore, except for the terrier at higher altitudes. What would you say is a recommended altitude is before you should rely on using a terrier?

Edited December 24, 2015 by Der Anfang

[fourfa]

30 kilometers

[OhioBob]

2 hours ago, Der Anfang said:

What would you say is a recommended altitude is before you should rely on using a terrier?

I suppose the ideal time to switch to the Terrier is when it's ISP exceeds the ISP of the engines on your earlier stages.  The altitude on Eve at which the Terrier and Vector have the same ISP is about 27.4 km.  And the altitude at which the Terrier and Aerospike have the same ISP is about 36.8 km.  Below is a graph that compares the performances.

Edited December 24, 2015 by OhioBob

[Teilnehmer]

On 22.12.2015 at 6:07 PM, ManEatingApe said:

I think the upshot was that practically anything is a better nosecone than the actual nosecones parts. The ramp intake for example is the same weight and has lower drag.

My own test showed the opposite for some reason.

The Advanced nosecones type A performed a bit better in my Eve rocket than the Ramp intakes did.

The tail connectors type A performed even better a bit on top of the boosters, but were too heavy for the main stage.

Edited December 24, 2015 by Teilnehmer

[ManEatingApe]

8 hours ago, Teilnehmer said:

My own test showed the opposite for some reason.

The Advanced nosecones type A performed a bit better in my Eve rocket than the Ramp intakes did.

The tail connectors type A performed even better a bit on top of the boosters, but were too heavy for the main stage.

Yup on reflection, I was talking a load of cobblers.

Here's @Yakuzi's excellent original thread that compares nosecones in 1.0.4.

Powered by eggnog and the spirit of scientific inquiry, I was curious to see how much (if any) things had changed in 1.0.5, so I created this baseline craft (craft file)

then using HyperEdit, placed it on Eve, at latitude 8.53065679509284, longitude 296.669318564622, elevation 544m

with a variety of nosecones on top the boosters e.g

For each nosecone type I set SAS to Stability Assist, opened the throttle to full and recorded the maximum height using the F3 menu. Taking the average of 5 runs for each type gave this graph:

The intake were open (closing them had no effect) and the NCS adapter was empty of fuel

To help make an informed decision here's the mass of each of the permutations:

Edited December 24, 2015 by ManEatingApe