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My Tweakscale Starship


eberkain
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I have been working on making a starship type vessel that I can use to do all different kinds of missions.  My goals are to keep the part count as low as possible and only use stock parts if at all possible. 

The core stack is 9 parts.  Nosecone, cockpit, cargo, fuel tank adapter, battery, reaction wheel, fuel tank, engine plate, structural tube. all the mk3 parts are scaled up to 5m.   

Then we have 2 solar panels for symmetry. 6 landing legs, 4 wasn't really strong enough. 4 airbrakes for reentry drag. 1 antenna, 1 extending docking port,2 drain valves for offset forces

 

XPRD2Irm.jpg Then we have the business end. 3 Vector engines for landing on Kerbin, 3 Wolfhounds for vac thrust. 1 extending docking port for orbital fuel transfer and 1 tri adapter. 

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And I haven't counted RCS. The monoprop blocks have a lower skin temp and tend to explode on me during reentry and its a massive vessel, so upscaled Vernor engines are really the only choice.  To cover all the directions in a reasonably decent way takes 12 of them. 

With the docking adapter inside the cargo bay we are up to 46 parts. 

t8T8X8Il.png I have also made a robot arm for the cargo bay that can be used to deploy modules.  I did manage to use it to build a space station.  Going slow and locking joints/only using one joint at a time does ok.  But it is still too wobbly to try and make manuvres, so I ended up having to autostrut the cargo to the ship to make it work, which tended to cause the robotics to wig the f out. 

The booster is just expendable with 4 parts and 19 vector engines scaled to 1m and gives the full stack about 5200 Dv off the launch pad.  

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Starship Dry Mass 62.7 tons / Wet Mass 226 tons

With 20 tons of cargo I get 3700 vac Delta V and a starting TWR of .42, which should take me pretty much anywhere on a 1 way trip, and i should even be able to do a mun landing and return after refueling in orbit. 

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During reentry I generally purge all fuel but about 1k Dv worth and go nose first with the airbrakes out, at about 10km we slow to under mach 1 and then I close the airbrakes and use the thrusters to flip over to tail first and have a powered landing.  This works for a LKO return, but returning from the mun melts the nosecone and airbrakes, so i got to figure out something different. 

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So now we have a new problem, lets say we find a place to land on the mun and we carry a cargo module.  How the hell do we get it unloaded?  

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Do you have any suggestions for how to reduce the part count?  

What could I do to survive a high velocity reentry since there are no belly heat shields in stock... or any mod that im aware of. 

 

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The current revision uses these mods, the starship is now 42 total parts.  

Kerbal Attachment System

Kerbal Reusability Expansion

Missing Robotics 

Tweakscale

Mk1 is 3.5m

Mk2 is 5m

Edited by eberkain
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I love the craft! Wonderful stock design ánd functionality!  As for re-entry heating, the only way I know is to put some really heat-resistant parts on the forward facing side during re-entry. I went with a full body fairing on my Starships, but you lose the very cool capability of loading and unloading cargo.

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15 hours ago, eberkain said:

What could I do to survive a high velocity reentry

I put an empty precooler behind the nosecone, and slide it back into the cockpit. Alternately, use a fairing or a shielded docking port.

For airbrakes, I'd replace them with control surfaces and set them to deploy on brake.

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6 hours ago, FleshJeb said:

I put an empty precooler behind the nosecone, and slide it back into the cockpit. Alternately, use a fairing or a shielded docking port.

For airbrakes, I'd replace them with control surfaces and set them to deploy on brake.

Still tweaking and playing around.  New nosecone from fairing which has a higher heat tolerance. 

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I added two radiators behind the cab and ran them during reentry which was just enough to keep things from overheating. I think its just going to be safer to plan on doing a small reentry burn to get down to under 3km/s before hitting the atmosphere.  Airbrakes seem not necessary.  but it would be nice to have something, i have 1 more idea. 

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Also tried several options for unloading cargo and finally decided on the gantry parts from the missing robotics mod and a winch from KAS, so 4 parts and I can unload cargo safely.  I also scaled the legs a little bigger and went down to 4.

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EDIT: The 5m cargo bay can actually hold the largest tundra modules from MKS if I add another extension.  Which also takes a 3rd gantry to extend far enough.  Tested that on uneven ground on the mun and it is functional. 

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Now I need some kind of truck that I can offload the modules onto which can them deliver them to the base site.... 

EDIT2: 

I tried out my alternate airbrake idea. 

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Between those and the radiators I was able to do a direct return from Mun nose first, but had stability problems below 1500 m/s.  The interesting thing tho was leaving the brakes on after the flip dropped the terminal velocity to about 120 m/s, so it takes much less fuel to land now. 

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Edited by eberkain
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7 hours ago, FleshJeb said:

Glad it's working better.

Your fins are deploying the wrong way.

right you are.  

I rebuilt the ship with the standard mk3 parts and added the KRE mod for better legs and thrusters.  I figure this way I can still carry 2.5m parts and it takes less fuel overall.  Basically everything the same just scaled down some.  Took the smaller version to visit my space station.  

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Deploying the other direction does make the craft super stable at high speeds.  

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I could not however get flipped over with them deployed.  So I need to be able to toggle the deploy direction as an action group to flip them when we are ready to flip the ship over for landing.  

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12 hours ago, redivh said:

It looks pretty cool, is there a link to download it?

I will update the OP

Sent my first real mission to the Mun using the ship. 

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Orbital refueling. 

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Successfully deployed an expedition rover to investigate some anomalies detected on the surface. 

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Burning for home after breaking the fuel tank on the rover and cutting the mission short. 

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I'm actually thinking about an elevator for crew, been playing around with different ideas so the don't have to jump out the door to get down and I don't have to jetpack everyone back up to the cab anymore.  

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I think I will just let it clip in/out, there are limits to what you can do with the pieces available. 

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Also, physics struggles

Starships in action

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Edited by eberkain
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So I've did a bunch of missions with my 5m starship and I had a list of things that I did and didn't like about it. The great things was that with as much as 20 tons of cargo I could launch, land on the mun, drop cargo and return without bothering to do an on orbit refuel.  And with an orbital refuel I could take as much as 50 tons of cargo. 

  I was thinking, why not go bigger?  Bigger ship, more cargo, less trips.  I'm having a lot of fun figuring out base building with a crane and unloading the starship on site.  What is the practical limit?  Landing gear can only scale to 400%, so that kind of puts a maximum size.  I starting working on a 7.5m version, but ditched that and went to 10m.  One of the things I didn't like about the last version was the upscaled mk3 cockpit, it kinda works for 5m, but it really doens't look right at 10m, so one of the things I wanted this time was for the crew parts to not be scaled.  I also wanted a crew exit inside the cargo bay.  I also wanted to not have any mods, but I don't see any way to do unloading without KAS winches, so that remains a requirement.  

I tried every combination of parts that I could come up with to do a cockpit nosecone and it just can't be done and look decent with stock parts IMO.  I was also having real trouble figuring out what to put above the cargo bay without using a scaled up mk3 command pod. there are only a couple choices and just the dry mass of one of the empty tank adapters at 10m is over 40t. I was about to give up and I discovered that the MK2 crew cabin can be surface attached.  I played around with a few ideas and ultimately decided on a crew section as a kind of spine in the back of the cargo bay.  This meant I could just make the nose cone a nose cone, so using a fuel tank with fuel in it on both ends of the cargo bay makes sense.  

Still trying my best to keep the part count at a minimum so its playable, this is how it stands.  

The main stack comes out to 14 parts: 1 fairing as nosecone,  2x tank adapter, 1x cargo bay, 1x fuel tank, 1x engine plate, 1x tube, 1x tri coupler, 6x engines

in the nosecone we have 4 parts, 1 probe core, 1 radiator, 1 battery, 1 reaction wheel. 

The crew spine is only 5 parts, 2 crew compartments, 1 cockpit, and 2 decorative parts.  The crew compartments are arranged so that the door for one opens into the cargo bay, the other one would not be needed, but the crew access elevator has to have a place to get stored, and I didn't want it to take up a chunk of the cargo bay, so the second one is needed  so we can have a crew egress to the side of a fuel tank. I could do an inline cockpit there instead, but then would need 2 decorative parts to accomplish the same thing that the regular cockpit does aesthetically.   In reality the crew elevator mechanics could be hidden inside the dead space along the corner of the fuel tank curve, since these tanks are so massive there would probably be significant space there to work with , so I'm good with the crew elevator system being clipped into the tanks when stored. 

The crew elevator is 14 parts, 1 hinge, 1 piston, 1 winch, 1 winch connector, 1 beam, 1 plate, 4 wings, 4 ladders  I really can't figure out a more part efficient way to do it and it be functional. True you could not have one on planets like the mun or minmus and just rely on jetpacks, but that isn't going to be an option everywhere. 

The rest of the system is 24 parts, 2 solar panels, 4 landing gear, 4 aero surfaces, 12 thrusters, 1 antenna, 1 docking port.

 After a lot of experimenting I have figured out that all I need for unloading is a piston and a winch, since the bay is so massive I opted for two sets, which is 4 more parts.  

We also have the space for 2.5m Kontainers inside the engine skirt. We connect those with docking port jrs.  So that adds 6 more parts. 

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rpqUypQ.jpgI have a booster built, and I need to do some math to really see what the Dv looks like, but I think I can take a couple hundred tons to the mun and return without refueling. It has a stupid low terminal velocity with those aero surfaces working to brake, like 60m/s , so it doesn't take much to land. The booster is beyond the pale tho, will detail it later. Gotta get my son to bed. 

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  • 2 weeks later...
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ok, so here we have one more revision to the design.  

Tweakscale had a bugfix update which changed the lowered the drag on the scaled up parts and made the ship burn up in the atmosphere. 

I tried a bunch of different solutions, but the real problem was that the aero fins at the bottom were too large and had too much control vs the body size. 

Smaller fins worked, but they could not provide enough drag during reentry. 

Finally I decided to just move the fins to the center of the craft which allowed the aero surfaces to do their jobs closer to the center of mass, and that works great. 

I also took the opportunity to extend the cargo bay, as large as it was, I found it limiting on some of the Tundra parts from MKS and could not do the things I wanted to try. 

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The other problem I had was that the crew elevator relied on too many moving parts and could end up flopping around in the atmo, even through it was clipped inside the vessel.  

I tried a dozen different designs on the elevator, there are several problems to work around.  Kerbals on EVA have no friction so they can't stand on a moving platform.  You can get around this by making a 'cup' like structure.  Kerbals on ladders can still create physics interactions and can have weird things going on.  

So here we have the final design. no more clipping into the ship. we take advantage of the taller cargo bay and instead of having a cup we just have a platform, and instead of ladders or standing we have seats for each of the crew.  We also resolve the issue of the elevator getting turned at an odd angle when it gets retracted back up.  With this system the crew should be able to get around the seats no problem.  At the end of the day the previous crew elevator was 14 parts and carried 4, this is 10 parts of the elevator, and 8 for the walkway, the struts are not technically needed, but look nice. 

This "final" version is 75 parts, with the booster increasing it to 94. I also have a MKS life support module that I can stuck under the fairing to give it a few months of supplies and habitat.  

The craft file should only require Stock + Tweakscale + KAS

KShip10E.craft

The Life Support module needs MKS suite. 

KShip Life Support.subassembly

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