Coming back to KSP after while- Ship Design

[Stewcumber]

I used to play KSP a lot, around Christmas 2015 (before "the wheels" update anyway) and I had a good thing going with getting rovers up to the Mun and Minmus (and back) on this thing...

(Also this version with the rover attached underneath the lander although the docking port is easily added back onto the above design)

This was probably the final evolutions of sixth or seventh refinements of this ship, and was pretty reliable at the time, and easy to fly believe it or not (or maybe I had just had lots of practice). I'm getting back into KSP now and I have a few questions!

1) Would it still work well in this version of KSP (have the aerodynamics changed...)

3) Is it generally a flawed design and worth starting from scratch? E.g. It is fine for the Mun and Minmus (it was only designed for that purpose), so I can't refuel with it.

 

Thanks!

Edited November 2, 2016 by Stewcumber

[Dafni]

I believe your craft should work just fine. Aero has had some changes, but I dont see many crucial parts on your ship. Maybe just cover all the open nodes on your radially attached boosters and tanks.

Tanks with open nodes in the airstream generate a lot of drag. Just add nosecones.

Another thing to keep an eye on would be fuel flow. There were some changes there.

In the end, there is only one way to find out. Load the craft and try it. You might want to adjust your ascent profile a bit, but the chances are pretty good you could still make it.

Unless of course I am missing something. Sometimes a screenshot is not enough, one really needs to fly a craft to find all flaws.

[Plusck]

1 hour ago, Stewcumber said:

3) Is it generally a flawed design and worth starting from scratch? E.g. It is fine for the Mun and Minmus (it was only designed for that purpose), so I can't refuel with it.

I don't see why it wouldn't work in 1.2.

As for the "design flaws"... well it works, so it isn't flawed.

• SRBs are cheap and have decent thrust. However they are heavy for what they do, and their vacuum I_sp isn't great. Carrying them up to orbit is therefore a bad idea generally, and is certainly making you use a lot more fuel than you need just to get to space.
• as @Dafni has pointed out - lots of flat bits facing ahead and behind, all of which will be adding a lot of drag. This ties into the next point:
• you're carrying a lot of engines that are doing nothing for most of the flight. This adds dead weight (and drag, since many of them have open nodes). Ideally engines should be firing all the time at full thrust, or ditched because they're surplus to requirements. Specifically:
  • The lander's engines being off to start with is understandable, but with some fuel routing from the lower stages, they could be contributing from the upper atmosphere and onwards (negating the need for the Hammers, for example). Their I_sp is better than any of the other engines you have there, so you'll end up using less fuel if you use them more.
  • That looks like three Swivels on the upper transit stage, plus four (and a Mainsail or Skipper) on the stage before that, all doing nothing and being effectively dead weight on liftoff. Total fuel for all of the pre-lander stages looks to be about 5 or 6 orange tanks. All of those engines could be merged into the very bottom stage, using just a central Skipper + 1 orange tank, two Mainsails on the sides with decouplers carrying two orange tanks, and a couple of Swivels (also on decouplers) with a couple of FL-T800s each. By feeding the Mainsails' tanks to the Swivels' stacks, and from them to the core, you should end up with much the same TWR at all stages, much less engine weight and much more dv for the same amount of fuel. You certainly wouldn't need the Hammers at all, and probably not the Thumpers (though there's no reason not to include a couple).

 

[Sharpy]

It will work, but it will work poorly. You should be able to achieve the same result in half the parts, or twice the result in this number of parts.

- learn to love Autostrut. Almost all of your struts could be replaced by autostrut.

- About the whole third stage seems completely unnecessary. Unless you're carryingt a single solid block of steel under that fairing, that bottom stage would bring you to an altitude, where second stage running off a Poodle (even without these side boosters) would bring you to LKO and all the way to Minmus suborbital trajectory and a nice part of braking above the surface.

- The lander seems like built to withstand Tylo landing, not Minmus. Landing legs, steel beams, the sheer number of struts on that Mk1 pod... You don't need half of that stuff.

- Get rid of the fairing as soon as you're out of the atmosphere. Observe the text that appears as you build a fairing, in particular the weight. That thing is HEAVY. You really don't need to haul it all the way to Minmus, and once in orbit you use much weaker engines so all these struts are unnecessary.

- Why are you landing with that one last tank? See that roundish bottom of Mk1 pod? It's made to withstand violent reentry and airbrake very efficiently if not obstructed by some tank.

[bewing]

7 hours ago, Sharpy said:

- Why are you landing with that one last tank?

Because the more stuff you land with, the more money you make. Throwing parts away is financially inefficient.

[Sharpy]

3 hours ago, bewing said:

Because the more stuff you land with, the more money you make. Throwing parts away is financially inefficient.

Are you seriously going to argue this in this case? Empty FL-T800 is 433 funds. Even the four decouplers used to discard the engines are 600 each, and with landing legs you could instead land the whole landing stage, recovering four Terriers instead of discarding the engines and recovering a single cheap empty tank! You could save up more on removing redundant struts and not carrying SRBs with third stage than on recovery of that tank!

 

[WanderingKid]

Should it work?  Yes.  However, like the others, I'm curious as heck.  4 Orange Tanks?  Last time I built something with that much power to it I went to Duna with a massive kerbal compliment, a science station, two (badly built) landers, a third emergency lander.  You've gotten into a Moar Powah scenario, where you're using fuel to lift fuel.

As long as you're reasonably aerodynamic, it should take you 3,500 - 3,800 d/v to get circularized.  Those nose cones do a lot now if you're not # of parts starved in career.  It's around 900 to get to Mun and 950 to get to Minmus (I'm hedging a bit here, for last minute maneuvers and piloting errors).  Pulling into Mun orbit costs ~300 d/v, and another 600-700 to land depending on how good you are of a pilot.  Minmus is ~200 d/v to pull into orbit and around 200 more d/v to land.

So all told, you need from the Launchpad 6,500 d/v to land on Mun and return, 5,500 d/v for Minmus (roughly, depends on your exit vectors and launch profiles).  Call it 6,000 for Minmus for safety.

I'm putting science bombs on the Mun for about 16,000 funds (Hard Mode cost), with a returning container for the experiments.  So, Mat Bay, Therm, Goo, etc.  Just how big is that rover?