"Best" KSPI SSTO?

[nuclearping]

Hello

Has probably been asked alot. But can't find any related / up to date threads. So I appologize in advance if this is yet another thread ...

I'm playing with KSPI (KSP Interstellar) since quite a while, but haven't really figured out how to use the Fusion Reactors and Generators properly. I know how to get a Nuclear Reactor working and how to build a Thermal Turbojet which uses Atmosphere and then Liquid Fuel.

However, I'm still getting pretty low on fuel once I reached Kerbin orbit. So to venture further I need to refuel in orbit first. Also my previous craft wasn't really cappable of visiting Eve (I get in, but can't get out ... :D) or Moho due to too little dV in the end for the return.

I know the "Interstellar Quest" videos from Scott Manley. I saw how he was using Microwave Transmitters. But I'm not a fan of them, due to their dependency on a proper relay network. Too much fiddle ...

I saw an old video from 2014 some days ago of a guy building a Fusion Jet SSTO:

Spoiler

 

But this isn't working anymore. The engine isn't available and using the normal "Plasma Thruster" instead doesn't produce any thrust on the runway at all.

So long story short: Whats the relatively "best" way to build a powerful SSTO using KSPI, without relying on MWT or refuelling in orbit?

[wumpus]

Judging by how Scott Manley's playlists are sorted I'd expect that his "interstellar quest" series is from KSP 0.18 or 0.19.  I wouldn't use it to figure out how the interstellar quest mods work now at all.

[AeroGav]

Back in December,   I installed Interstellar in order to continue a career game.   Had a few issues getting the mod to work properly.   Built this with a few techs low on the interstellar tech tree

 

The reactor is the bottom tier Molten Salt reactor, producing Thermal Power.   I unlocked the Hybrid Thermal rocket tech,  which enables the basic Thermal Turbojet to have a closed cycle mode, like a RAPIER.    So basically, your reactor produces thermal power,  and your Thermal Turbojet consumes Thermal Power to make thrust , either using intake air, or a liquid propellant >30km (functioning like a NERV).  

I used Modular fuel tanks to swap the contents of everything from Liquid Fuel to hydrazine.

Hydrazine is a standout fuel.  Most of the time when you put stuff in a nuclear thermal rocket, the higher your ISP , the worse your fuel density and the worse your thrust will be.  Hydrazine gets far more thrust and isp than similar density fuels however, i think because it undergoes the same chemical reaction inside the nozzle as it does when used as a monoprop, adding to the performance.   Unlike hydrogen it does not boil off, and unlike kerosense/liquid methane it does not soot up the engine's insides.

I built a mk1 spaceplane with a 1.25m molten salt reactor, could only get a 5-10 degree climb rate and couldn't go supersonic.

Then i used tweakscale to make it 2.5m, power increased disproportionately and i was now climbing at 30 degrees, delivering  a 7 ton payload to mid orbit and still having >2k delta V left !

I quit at this point as i felt this was unrealistic, but on the forum they reckon that larger reactors are more efficient, this is working as intended etc. etc.  Don't know if still the case .  No doubt the mod has been through many more updates since.

 

[nuclearping]

Interessting. Thanks for the info. Never used Hydrazine in my whole gametime with KSPI though. Will give it a shot.

Can you make Hydrazine with ISRU? If yes, from what resources? Ore? Or do you need to scoop?

Edit: I noticed that if you apply TweakScale to reactors, generators and engines, they seem to not scale properly in terms of power. I built a Mk3 SSTO with 1 large Mk3 LQ fuel tank, Pebble Bed Reactor, Thermal Electric Generator and a Thermal Turbo Jet. After getting to Orbit, I still had plenty dV left. In comparison, an equivalent Mk2 SSTO with 1 large Mk2 LQ fuel tank, scaled PBR, TEG and TTJ I always end up in Orbit with much lower fuel then its Mk3 counterpart, even though it is smaller and lighter ... Don't know if this is true or I'm just imagining things ...

Edited May 20, 2016 by nuclearping

[AeroGav]

The drawback of hydrazine is that there didn't seem to be a way to IRSU it.

Use hydrazine to launch, but have some other tanks on the vessel that launch empty but are filled via IRSU once you land offworld, and use this fuel for travel from that point onward?

 

[nuclearping]

Well yea, I could. But thats also unnecessary payload. So you could stick to Air / LQ fuel or LqHydrogen. But however you turn it, you still end up needing a refuel after getting into Orbit.

Isn't it possible to build a SSTO with a Fusion reactor and Plasma thruster or something (anymore?), like the guy did in the video?

[AeroGav]

Hopefully someone more knowledgeable about endgame KSPI techs can answer this, if you want an extreme ISP propulsion system.

However, the ship i pictured above would be able to grand tour , pretty much (maybe not land on tylo, due to lack of atmosphere and high gravity).

Use some of cargo bay for ISRU and some for a tank containing the mined fuel.   Remember, the Kerbin to Minmus leg is the hardest of any grand tour.   Minmus to Ike (refuel again on the side permanently facing the sun) is little more than 1k delta V,  Ike to Jool is 2-3k,  Jool to Eeloo is about 1k.    

I have actually done this tour on a stock mk2 ship, though it wasn't quite SSTO (has a couple of panther boosters that were dropped on the way up).

ISRU is quite painless once you've got a setup capable of it.   You can accelerate time to x 1 million while the vessel sits on the ground and get full tanks in one or two game minutes.  It continues to mine at a lower rate if you switch away to control a lower ship.  It only becomes a drag if you've not got enough power storage to mine overnight, that means you have to turn the drill on again every morning.

What I usually do in my career games is separate the ISRU and exploration vessels however, since it's tough to make something with enough payload capacity for both roles.  I use Kerbal Attachment system to link the two vessels on the ground - just park up within 30m of each other and send  a Kerbal out on EVA to run a fuel pipe.      This is a lot less work and time consuming than orbital rendez vous and docking. 

[FreeThinker]

On 20-5-2016 at 2:29 PM, AeroGav said:

The drawback of hydrazine is that there didn't seem to be a way to IRSU it.

No there is a way to create hydrazine with KSPI ISRU, it requires Ammonia and HydrogenPeride, which can be made with IRSU as well.

[Palaceviking]

On 20/05/2016 at 1:29 PM, AeroGav said:

The drawback of hydrazine is that there didn't seem to be a way to IRSU it.

Use hydrazine to launch, but have some other tanks on the vessel that launch empty but are filled via IRSU once you land offworld, and use this fuel for travel from that point onward?

 

You CAN isru hydrazine.

It's just complicated cos you need nitrogen and water