Mother of Mothership

[Suiram1649]

Anyone ever tried to build a craft that would be able to do everything you would as it? Like for example launch from Kerbin, land on Eve, refuel, then relaunch from Eve, go on Laythe, refuel, then go on [...]? Is it possible? I thought something that would have around 20k dV, 1.5 TWR & 1.00 SLT when simulated from Eve (since it would be the hardest land/relaunch right?), but it seems like it's harder than harder said than done. I have been struggling for a couple of hours now trying to figure out how I could get the most dV out of this beauty but you know.

Here's my work yet, any ideas for increasing the efficiency? And yes this can all hold up together, all it needs are some struts that I will add at the end : 

 

 

I'd really like to keep the ring theme, and add docking ports on the side with comm modules on top. Also there are missing Science items but that can added after making everything launchable.

[Snark]

Well, if you could build a thing that can get off the surface of Eve and into orbit, then it can basically go anywhere and do anything, as long as it can refuel in between major missions.

The problem is that the way you've described your ship pretty much requires that your ship has to be SSTO.  And it's basically impossible to build a craft that can SSTO from Eve, without using modded parts; it pretty much forces you to use a multi-stage design.

So, that's the major stumbling block that I see.

One way around that, if you're willing to use mods, is Extraplanetary Launchpads.  That's a mod that allows you to mine metal, then use it to build craft on your ship, rather than having to launch everything from KSC.  So, with that setup, it's certainly possible to do a single "grand tour" mission.  As it visits the various planets, it mines metal and constructs specialized craft.  So, for example, the mission to Eve would look something like this:  arrive at Eve, go to Gilly first, mine metal to make a multi-stage Eve lander; send that down, it comes back up, recover the crew & the science, then move on to the next place.

[Cpt Kerbalkrunch]

Welcome to the forums!

Mr @Snark failed to extend this courtesy, so he too shall receive a stern talking-to.

For your ship, does it really need to land in one piece? If you made it a true "mother" ship, it could certainly have detachable landers. It looks large enough that you could have several. A low g lander for places like Pol, Bop, Gilly, and Minmus, and a high G for Tylo. Maybe a medium for Ike, Mun, and Vall. Then an atmospheric for Duna and Laythe. Designing each one and putting all together in a way that still functions as a whole would be a lot of fun.

Eve is it's own animal, though. Enter at your own risk.

 

Did I leave out Moho, Dres, and Eeloo? Shame on me.

Edited May 2, 2017 by Cpt Kerbalkrunch

[juanml82]

That ring will not take off from Eve, even in a multistage design: is too heavy and antiaerodinamic.

 

You can't do an Eve SSTO. But even in a multistage ship, you'll need to reduce The ship's drag to a minimum and lift as little payload as possible

[Suiram1649]

2 minutes ago, juanml82 said:

That ring will not take off from Eve, even in a multistage design: is too heavy and antiaerodinamic.

What if I use a smaller ring? The idea for rings is to have the docking ports on the side for multiple landers or extra vacuum fuel, also for aesthetic purposes! But otherwise how would you build a ship with that objective in mind? Big ship with landers, as said above?

[Ithirahad]

You just... don't try, from Eve. Everything else, sure...

[eddiew]

2 hours ago, Suiram1649 said:

What if I use a smaller ring? The idea for rings is to have the docking ports on the side for multiple landers or extra vacuum fuel, also for aesthetic purposes! But otherwise how would you build a ship with that objective in mind? Big ship with landers, as said above?

You have to remember aerodynamics and atmospheric drag is a thing in KSP. If it's blunt at the front, it's going to be hard as hell to get to orbit. You need a pointy front and a smooth body if you want it to SSTO on an atmospheric world.

You've also got a ton of un-used attachment nodes on those 6-way connectors. KSP adds an artificial drag penalty to these, so I'll honestly be amazed if you can even break atmosphere on Eve. 

Which is fine, KSP is very much a learning curve   You're never wrong to try things out, but this is the reason that this ship won't work (or at least, will be very cumbersome and hard to fly).

Bear in mind that most of us do SSTO's as spaceplanes. Sleek, pointy, and making use of wings to help avoid gravity losses during ascent. VTOL rocket SSTOs are another class entirely, and VTOL rocket Eve SSTOs are... not unheard of, but certainly not achievable with the excess baggage this one is carrying. You have 4 heavy jet engines that you can't use on Eve, and far too much weight of passenger cabins. Take it down to 1 crew pod and those tanks and engines might just get 1-3 kerbals off the surface   I highly recommend a browse of these forums to previous solutions to Eve ascent, it will save you a lot of time and pain!

The jets, btw, are why you're reading such a high delta-v. Take them away, and I suspect you'll have more like 2km/s.

For reference, here's an example of an Eve SSTO. Check how much fuel and engine mass there is vs crew pods!  

(Sorry, I'm not looking to be overly critical or unkind. It's just that you're wasting your time on this one and you can spare yourself a lot of pain by knowing about it!)

Edited May 4, 2017 by eddiew

[kraden]

If you really want the ring design, you could do like @eddiew has in the past and have an SSTO spaceplane that docks worth a ring shaped interplanetary transfer bit. That saves you weight on both descent and ascent. If you're set on having a single piece ship that can both land and take off from any body, good luck and I want to see it if/when you pull it off. Either way, you'll need to have a minimalistic design approach. All those crew cabins are eating up your dv and as others have said, they are not very aerodynamic.

[Frozen_Heart]

You can make something that will do everything but eve, but SSTO from there is close to impossible.

 

I'd suggest leaving that one out.

[Freshmeat]

I have found it very hard to get more than ~9000 m/s from my interplanetary ships if they where to have a reasonable payload (30-60 t). These have acceleration of around 2 m/s^2 (TWR = 0.2) and no provision for landing themselves, but carry landers, bases and personel throughout the Kerbol system.

[Vanamonde]

This sharing of a craft has been moved to the craft sharing subforum. 

[sdj64]

Welcome to the Forums!

I think you are becoming confused because your ship includes jet engines, so its atmospheric delta-V is high.  However, jet engines only work on Kerbin and Laythe, so they would be no help on Eve.  Look at your vacuum delta-V, it is only 1593.  Even on Kerbin I suspect your ship will have trouble because the jets you used only work at low altitude and it may not have enough to get through the upper atmosphere and into orbit.

Doing this on Eve is impossible with any craft, even though stock Eve SSTOs have been done, stock Eve SSTOs that can make it to Gilly to refuel have never been done and it's beyond the laws of physics for stock parts.

 

Most of these "all-in-one" crafts are spaceplanes that use rapiers on Kerbin then go to Minmus to refuel.  A few rocket designs have been done but it is much harder to do.  You need about 4800 vacuum m/s to get to Minmus on all rockets, or about 1500 left in orbit after you reach it with jets.  Most rapier-using spaceplanes can't do Tylo either, but rocket ones can.

 

I have, in fact, tried to do exactly what you want to do (except Eve).  My ship was a rocket-only winged design that carried some 40 Kerbals, a lander, a small plane, a rover, and a scanning satellite.  It had some major issues though which made it terrible to fly and had way too many parts.  Never got farther than this picture.

[juanml82]

Also regarding the engines, you're using the 2.5m jets, which are only for subsonic jets in Kerbin and the 3.75m first stage engine, which is terrible for vaccum. The 2.5m jets are just dead weight above 10,000 meters in Kerbin.

As recommended engines, although this is much more complex, I'd say you have two groups (not exactly, but to get an idea): engines that take off from Kerbin's surface (or any other gravity well) and engines that excel at vaccum.

For a mothership, you want engines from the second group - the catch is that most of those engines suck as lifter engines and not all of them work well for lander engines. I'll list them:

Nerv: excelent isp when paired with liquid fuel only tanks. Heavy, low thrust so it can't take off Kerbin (let alone Eve) and it's long shape requires creativity to place it in a lander. Also, since it's heavy, it makes your lander heavy.

Terrier  and Dart: the best isp for 1.25 engines. The Terrier sucks in an atmosphere, the Dart doesn't and is one of the few engines to work in Eve's surface. The Terrier is lighter, has gimbal and low thrust. The Dart is a bit heavier, lacks gimbal and has decent thrust (for a 1.25m engine). I'm not sure if you can make a pure stock SSTO with darts for Kerbin (I've tried without success).

Poodle: pretty much an oversized Terrier, so same recommendations. The best isp of chemical engines

Rhino: the best isp of 3.75m engines. Heavy. Powerful thrust. Can be used as a lifter engine in an atmosphere, although it doesn't excel at that. Its tall profile and heavy weight means it takes a lot of creativity to use it as a lander engine using stock parts (you need landing legs somewhere!). Can't take off from sea level at Eve.

 

Also, a good navigational practice for interplanetary ships with low TWR (as in, relative low engine power compared to their mass) is to split the nodes. So, instead of a long 2,000 dV burn, you start with a 800 dV burn at the place where you need to burn to go interplanetary. That will put your Ap by the Mun's orbit and it will take about a day to complete the orbit (so you don't risk missing a transfer window by pushing the Ap to Minmus orbit).Then you schedule the actual interplanetary burn at (or near) your Pe. You save some fuel due the Oberth effect and you gain in accuracy.

Edited May 5, 2017 by juanml82