Economical Space Delivery System

[skrpt kddz]

Hello, I'd like to share with you all my proposal for a highly economical system to deliver crews and payloads to multiple destinations around the kerbol system. The system will comprise of several orbital tugs in space, modified second stages of my Raptor Heavy launch vehicle, which can deliver a second stage into space with just a first stage and a booster. These several different tugs are launched into space with docking ports, a mixture of solar panels and rtgs, and more monoprop tanks. Then, several Raptor Heavy launch vehicles are launched into different orbital inclinations around kerbin. Then, a Raptor 1 launch vehicle, a Raptor Heavy without four small liquid fuel boosters and a smaller fairing, could launch up payloads with a modified reusable second stage, which would deliver a payload or crew to the orbital tug via docking ports, then, it would re-enter the atmosphere, parachute down to the surface, and be recovered. To expand the effective range of said orbital tugs, more refuel depots could be delivered to the orbits of different planets and moons, to serve as stops to refuel for stages departing from kerbin. To keep prices down, this system would need to be sustained by several IRSU sites spread around the kerbol system would need to be operated, periodically replenishing their supply depots. The orbital tugs themselves have 5.1k deltav, which would allow them to deliver a payload to just about anywhere, refuel along the way if needed, refuel for a return trip, and return back to kerbin. Additionally, tugs could be kept on standby outside of kerbin around other celestial bodies, allowing economical crew and payload transport to and from any destination around the kerbol system. For instance, a mission profile could follow a tug refueling in orbit, a delivery stage delivering a payload to a tug, the delivery stage being recovered on kerbin, the tug going to, for instance, duna, delivering the payload, refueling, returning back, topping off its fuel, and repeating the cycle.
I'm going to be attempting to refine and replicate this system over time on my savegame, and trying to figure out exactly how much it could save. Thanks for reading over this, please comment with your feedback.

[Rocket Witch]

Sounds good, but regarding those tugs, make sure that 5.1 km/s is your laden capability for the payload capacity you're designing for. Something with 5.1 km/s on its own might have less than 2 km/s left over when docked to another craft of similar mass to its own, and your description of them having monopropellant engines implies you've made them quite small. For comparison, my own 'tug' designs are large 80+ tonne (wet mass) craft inspired by the NSFD Shuttle and have over 12 km/s unladen.

Given that these tugs are reusable and just trundle back and forth between celestial bodies and stations, nuclear engines are ideal for them. Once you've footed the bill to buy and launch them, you've got the best possible combination of efficiency and thrust to make efficient tranfers with heavy payloads.

[James M]

Question here!

Could you lay out some idea of your infrastructure for your mining systems? 

I tried setting one up with a mining platform on Minmus, a refinery in orbit, and a ore transport piloted by a kerbal engineer, but failed because I couldn't stick the landings. (may have to learn kOS 0.o ) I'd be interested to learn what I could have done better.

[skrpt kddz]

Well, when it comes to landings, I'd highly suggest packing lots of extra fuel into your landers. I'd highly suggest a few degrees before going over your target on the surface, slowly zeroing your velocity, descending down with zero lateral velocity, turning as needed to steer your lander closer to your surface base, then, you should be able to figure out out from then and just land normally. If your a bit off, I'd suggest small suborbital hopps.

As for the ground mining operation, you should probably have unmanned mining landers which will dig up resources and refine them into fuel, then transport the fuel with rovers with docking ports on them over to ascent landers. At that point, you would want to top off your ascent landers fuel, haul up all the fuel to an orbital depot, which then you could use for refueling spacecraft departing from the kerbin system, exporting fuel via tanks with a heat shield and parachute back to kerbin, and distributing fuel around your tug network. 

As for Rocket Witches post. I was kind of inspired by old Space Transportation System concepts, where something that is reusable goes up and delivers a payload to a tug, lands back on kerbin, and the tug delivers payloads, comes home, refuels, then repeats the process. https://en.wikipedia.org/wiki/File:Cargo_transport_from_Space_Shuttle_with_the_space_tug_to_Nuclear_shuttle.jpg

[Hotel26]

On 1/21/2021 at 3:10 PM, James M said:

I tried setting one up with a mining platform on Minmus, a refinery in orbit, and a ore transport piloted by a kerbal engineer

Take a look at e.g. TANTOR-K15 for a well-engineered example that takes the single mining drill back to orbit with it where its radiators etc can be used during the refining operation in orbit.

Or my Outland which carries the refinery component with it into orbit, to be deposited upon your space station and then makes trips to the surface alone simply to mine ore.

                                                                           

Depending upon what you mean by "sticking the landings", I'd recommend Better Burn Time for guiding your descent speed to the surface.  And for pin-point landings, I perform a prepatory inclination change to align with the target; followed by using this equation, s = v^2 / 2 / a,where s is distance before the target at which to begin a Sfc Retrograde decel burn, v is your orbital speed and a is your max decel as shown by e.g. KER.  This will get you stopped (horizontally) over the target, or very close to it.

Edited January 24, 2021 by Hotel26

[James M]

On 1/23/2021 at 11:55 PM, Hotel26 said:

Depending upon what you mean by "sticking the landings", I'd recommend Better Burn Time for guiding your descent speed to the surface.  And for pin-point landings, I perform a prepatory inclination change to align with the target; followed by using this equation, s = v^2 / 2 / a,where s is distance before the target at which to begin a Sfc Retrograde decel burn, v is your orbital speed and a is your max decel as shown by e.g. KER.  This will get you stopped (horizontally) over the target, or very close to it.

I guess I should specify, I was landing on the target yes. Just not so perfectly that I could get the ports to align. I was always just a meter or two away from a perfect landing and any adjustments I tried to make just ended up confusing me on the navball.  xD

I could of just used trajectories mod or whatever but I wanted to do it legit stock.. I did however end up getting it to work later though. I made an entirely new hauler with the control point at the center of mass and used pulling engines rather than pushing. 

[Misguided Kerbal]

I actually have a very similar system in place, except not as complicated as yours. I have these things called ANTS (Advanced Nuclear Tug/Transfer Stage). Basically, these tugs dock with a Depot in LKO (which is resupplied by tankers often) and have about 6000 dv unladen, giving them enough to ferry stuff around Kerbin's SOI and back. 

 

Seen Here: Payload rendezvousing with ANTS at KOFD (Kerbin Orbital Fuel Depot)

 

Seen Here: KOFD with 2 ANTS docked to it

 

Seen Here: ANTS delivering payload to Mun

 

Seen Here: Reusable Tanker Pod

The Tanker pod has a 10m inflatable heat shield on the bottom for reentry, and it's jettisoned after chute deployment.

 

 

 

The ANTS can also be useful for other things, such as acting as an engine block for interplanetary trips, like my recent trip to Duna:

 

For a viable and easy to refuel system, I suggest you use NERVS as Rocket Witch has suggested. However, you might want to consider adding some sort of auxiliary engine or about ~4 NERVS, or else your TWR will be too low for any reasonable burn time. Currently my system is only about Half-finished, I plan on supplementing the fuel deliveries from Kerbin with fuel from Minmus and possibly using an Asteroid to get fuel.

[skrpt kddz]

Alright, seems pretty cool I'll try it out, really cool system.

[Misguided Kerbal]

3 hours ago, skrpt kddz said:

Alright, seems pretty cool I'll try it out, really cool system.

Thanks a lot!

[SpaceFace545]

I did the same thing, I used a rocket with recoverable engines only which could put heavy payloads into LKO and then another rocket would take up a reusable second stage with about 5000m/s of deltav that could take the payloads anywhere and could be reused if they were kept within the kerbin sphere of influence.