Reusable space programme - refuelling and crew return?

[NSEP]

Im currently working on a Vertical takeoff and Horizontal landing booster in Realism Overhaul, along with a reusable Transfer vehicle. I will post updates

[Raptor9]

I've given considerable thought how to set up a propellant generation network in the Kerbin SOI that is both efficient and practical, but I've never taken it down to hard numbers or mathematical equations on total energy in vs total energy out.  It's probably not the best, but in my mind it has the least amount of overhead effort to maintain.

1) Location of assembling and launching interplanetary missions: low Munar orbit.  It takes less delta-V to achieve Kerbin ejection velocity here than it does from Minmus orbit, even if you don't use a Kerbin slingshot; which is of course an option to reduce delta-V expended, but it requires more complex trajectories.  The zero-inclination orbit provides an easier access route to/from Kerbin, and the shorter orbital duration allows for more frequent departure opportunities than Minmus.  Plus it's close to the propellant generation location: the Mun.
2) Location of mining propellants: Munar surface.  I refine all the propellants as necessary on the surface, and lift the fuel to munar orbit.  The orbital fuel depot/shipping hubs are at low altitude (15km equatorial orbit) to provide a close orbit to equator ISRU sites so the fuel transports expend the least amount of fuel hopping up to the depots.  You could reduce the fuel expended lifting to orbit by mining on Minmus and shipping it to the Mun, but you would lose a lot more fuel during the transit, and it adds a lot more tedious "economy management" gameplay, taking away from the actual exploring.
3) Fuel transport: large propellant fractions/efficient propulsion.  The uncrewed fuel transports are essentially large fuel tanks with landing gear, engines, and attitude control.  They have a high propellant fraction to reduce the amount of hardware weighing them down, and utilize Poodle engines that have decent thrust and the highest ISP, again to prevent fuel losses during shipment.  All of the ISRU equipment remains on the surface in place since the hardware is heavy.  You really penalize yourself by having a lot of unnecessary equipment repeatedly moving between the surface and orbit, like large crewed sections, or carrying drills, converters, large solar arrays/radiators.
4) Reusability: once it's in orbit, it stays in orbit.  Pretty much the only launches from the Kerbin surface is new hardware, so the rockets need to be as cheap as possible, and the lifters only need to make it to low Kerbin orbit.  Once in orbit, refuelable cargo transports or reusable upper stages dock to the payload to transport them elsewhere.  For Kerbals, I send them up on SSTO spaceplanes to waiting crew transports in orbit to take them elsewhere, or vice versa to return them to the KSC.
5) Interplanetary versatility.  To reduce the amount of hardware you purchase before you launch it from the KSC, try to make the craft as versatile as possible.  It's a lot cheaper to buy spacecraft that can perform multiple functions, or be reconfigured to perform different missions, instead of purchasing two entire spacecraft for the two functions.  This also means you expend less fuel and delta-V sending one craft versus two on interplanetary missions.  And it also builds redundancy.  (ie: Wrecked my reusable Ike lander?  I'll use my reusable Duna lander to perform additional sorties to the Ike surface -since I ensured it has that tested capability- because the next transfer window to send a replacement lander is in 6 months, with a 8 month travel time, etc.).  Of course you need to keep it within reason; adding too much additional equipment to a spacecraft to perform a bunch of different functions and you'll start impacting its performance.

Regarding aerobraking and gravity assists, these are skills I haven't gotten proficient in, so I tend to focus on propulsive captures and simple departure burns.  But again, I'm very selective on where I'm departing from to save on dV.

Edited January 19, 2018 by Raptor9

[RizzoTheRat]

18 minutes ago, Raptor9 said:

1) Location of assembling and launching interplanetary missions: low Munar orbit.  It takes less delta-V to achieve Kerbin ejection velocity here than it does from Minmus orbit,

Do you know roughly how much the difference is?  Given earlier comments about Oberth presumably this is due the Mun having higher gravity than Minmus so higher orbital speeds?  If so would it be more efficient for the departing craft (but not the refuellers) to be in a high orbit, and brake to an elliptic orbit so the ejection burn at periapsis starts at a higher speed?

Clearly I need to do some experiments.

Edited January 19, 2018 by RizzoTheRat

[Raptor9]

@RizzoTheRat, I apologize, I should have been more explicit. I meant that it was less delta-V to depart directly interplanetary from a low Mun orbit compared to a low Minmus orbit. As for what combination of gravity slingshots you use (Minmus to slingshot around Kerbin, or Mun to slingshot around Kerbin), that's something I haven't gotten hard numbers on.

I will say though that if you can setup a propellant generation system on the Mun, you can use the same equipment in other places like Ike or Dres since they have similar gravity (just slightly less). The only thing you may have to change is your power generation capabilities due to less solar energy the further out you go.

[KerikBalm]

22 hours ago, RizzoTheRat said:

is it worth it for the extra hassle of being on a inclined orbit compared to the rest of the solar system? Plus it's 6 day orbit presumably makes hitting transfer windows easier than Minmus's 49 day orbit?

IMO, yea, go with the moon for the shorter orbit/transfer time/no inclination.

I play a modded system, and I swap the orbits of Mun and Minmus (along with a 3x rescale), if you're ok with that, then it makes the choice real easy

Proportionately, its a better place for Mun anyway (as an analogue of Earth's moon, Minmus has no analogue, so whatever)

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What I'd like to do is have a reusable vehicle that transfers them to somewhere relatively close to Kerbin, and then a separate reusable lander to get them down.

Ummm, then just send up an SSTO from kerbin to rendezvous with the transfer vehicle?

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 Not tried it yet but I'm assuming the Mun's inclination makes it a lot easier to aerobrake around Kerbin and get in to a Mun orbit than it would to get to a Minmus orbit, or is it generally going to easier to just carry enough to fuel to get in a Kerbin orbit with limited aerobraking? 

IMO in stock size, its easy to carry fuel, but yes its much easier to aerobrake to a Mun intercept than to aerobrake to a Minmus intercept.

[RizzoTheRat]

28 minutes ago, KerikBalm said:

Ummm, then just send up an SSTO from kerbin to rendezvous with the transfer vehicle?

Yeah, that was the plan, but I just haven't worked out where yet, I'm veering back to the original idea of a refuelling station in Mun orbit, but not sure if returns need to go via the Mun or in to Kerbin orbit yet.  

However other comments earlier on this thread have given me a slightly different idea instead of having an SSTO crew lifter.  I already have SSTO boosters I use to launch stuff and then de-orbit them empty to land as near to the KSC as possible.  (I got a bit lucky landing this one, which can launch 45 tonnes to 80km)

With a bit of forethought I should be able to come up with an interplanetary crew transfer vehicle that can dock with a spent booster and use it to get back down to Kerbin.  This might have to involve having some extra fins on the transfer vehicle as it's going to be a lot of weight on the top on the booster that might then struggle to keep pointing retrograde.  Alternatively I build a Mk2 lander can in to my boosters so each one can lift or return a couple of crew members, and I leave the boosters in orbit until required.  This wastes some weight on every launch but means I'm reusing my interplanetary vehicle rather than keep recovering and launching new ones.  Or I have an interplanetary transfer vehicle with a modular payload so I leave the tug in orbit but land the crew module...

Probably just as well that my wife's away until Saturday evening as I'm not sure she'd be seeing much of me tis weekend...

[magnemoe]

15 hours ago, RizzoTheRat said:

A lot of people don't like asymmetric designs either, the full size ISRU plus a medium Thermal Control System weighs 4.5 tonnes, the same as an empty Ore tank and a Hitchiker.  This was my now aborted design for a self landing Mun mining base, obviously it's not perfectly balanced but its close enough that the torque can handle it, it also wouldn't work if you were planning on taking off again with a load of ore, but it was only intended to land with the bottom tanks in use.

One extra ore tank would balance it if you put something to counter the dry mass of tank, 
Reminds me of my typical mobile Mun base but its designed to take of with full ore load, found the base very useful in that it can land everywhere on Mun, refuel ships in orbit on on Mun using Kas. 
Tourist landing on Mun tend the get lander refueled by base. 

Minmus is the real refueling facility. 


This is the tanker. Only need one

[ShadowZone]

In general I like to put everything I need for a mission into orbit in one launch. I am also not a huge fan of SSTO spaceplanes. Probably because of the lack of cargo capacity. That's why I designed a massive 2 stage fully reusable launcher system, the "Kerbon Heavy", that can put more than 1000 tons into orbit and return safely to Kerbin.

It's a beast and expensive (about 4,000,000 Kredits) and you need access to good tech, but it's very satisfying being able to launch that much into orbit and recover everything besides the fuel:

 

I also like to keep stuff in space that can be used for multiple purposes. Multi-role spaceships are sort of my thing
If you add docking ports in strategic places of your vehicle, you can expand it later on when it's already in orbit and you need something a bit different.

 

Regarding refueling... so far I have built three "space refineries":

1) My Minmus refueling operation ("Munsucker"). It was designed way too complex, with a dedicated mobile ore drilling platform and a separate refinery and fuel storage.

2) For my Mun refueling operation ("Munsucker 2") I put drills and refinery in one single package. Fuel storage was modular, designed to be lifted into an orbital storage facility. A transfer vehicle transports everything to LKO if needed.

3) I designed a self sufficient Jool colonization mission and included a mobile refinery for Pol. Due to its miniscule gravity, the entire refinery is lifted into orbit. There's a depot there with two shuttles designed to ferry the fuel to Laythe where my main space habitat and other craft reside.

 

In general, I like to stay reusable more in a sense of what is already in space compared to launcher vehicles

 

[Corona688]

22 hours ago, XLjedi said:

I seem to be spamming craft pics today... 

@Corona688 "People will go to heroic lengths to avoid landing the full-sized ISRU, just because it's so obnoxious to design with.  You can't attach radial parts to it, so any traditional design becomes a top-heavy needle or skycrane of trusses. "

Mobile planet-side ISRU, bit of a monstrosity, but it's not too bad!

https://kerbalx.com/XLjedi/RLV-21-Magic-Hat

I call shenanigans, I see tons of parts radial-attached to your ISRU, you can't do that in stock.  Either that or you've clipped them all the way off their source part.

[XLjedi]

50 minutes ago, Corona688 said:

I call shenanigans, I see tons of parts radial-attached to your ISRU, you can't do that in stock.  Either that or you've clipped them all the way off their source part.

 Ha!  yeah... you caught me there... trying to pull a fast one. 

LOL, as if the idea of attaching to the part right next to it is some sort of design revelation I've solely managed to stumble upon.    ...and "clipping way off" is what?  nudging it to the left or right a meter or two from the next closest part?  In this case, you should also be warned that I regularly attach landing gear to different parts of the fuselage and slide em out to what must be blasphemous distances on the wings to help them track straight on the runway.

The intent was just a counter to your idea that this ISRU part is somehow "heroically" avoided because it's nearly impossible to work with under some sort of "traditional design" constraint that results in unwieldy contraptions.  It's no worse than any other part I have to deal with that won't allow radial attachment.

The craft is actually a very handy and usable rover design that I like to dropoff and retrieve at will.   But you don't need to take my word for it; you could follow the download link I provided for the stock craft file, examine it in your stock installation SPH, drive it around... dock it with some of the other transport craft that I also posted and it's compatible with, and drop it off at the Mun or Minmus.  It's a good design I think, and I have a lot of fun with it on missions.

Edited January 19, 2018 by XLjedi

[Corona688]

1 hour ago, XLjedi said:

LOL, as if the idea of attaching to the part right next to it is some sort of design revelation I've solely managed to stumble upon.

Don't worry, I don't give you that much credit.

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The intent was just a counter to your idea that this ISRU part is somehow "heroically" avoided because it's nearly impossible to work with under some sort of "traditional design" constraint that results in unwieldy contraptions.

And proved my point instead by showcasing everything the ISRU doesn't let you do.

I guess it comes down to your personal building rules. We all could just clip it, but many would think twice.  Clip a battery onto a structural part?  Who cares.  Clip a battery onto an engine?  The hot part?  That's crazy talk.

Edited January 19, 2018 by Corona688

[XLjedi]

36 minutes ago, Corona688 said:

Don't worry, I don't give you that much credit.

And proved my point instead by showcasing everything the ISRU doesn't let you do.

I guess it comes down to your personal building rules. We all could just clip it, but many would think twice.  Clip a battery onto a structural part?  Who cares.  Clip a battery onto an engine?  The hot part?  That's crazy talk.

Well, OK then... 

Guess I'll have to scrap my other idea of attaching wings to the ISRU and flying it around...  

Ah well, back to the drawing board.

Edited January 19, 2018 by XLjedi

[RizzoTheRat]

Not sorted out a refuelling station yet, but I've decided to go modular, with a simple tug design that will dock to other modules as required.  The main body's a tweakscaled liquid fuel tank, and the service bay has a KR-14 dish to  talk to Kerbin (I'm using RemoteTech some coms are important).  4 Gigantors should give me plenty of power at Duna but beyond there I can easily add a fuel cell generator module

So for a couple of contracts to test some parts above Ike and land a base on Ike, I've just launched this

It'll leave the reusable booster in Kerbin orbit and head to Ike.  Landing gear and pylon can be tested in Ike orbit and then top section disconnected and dumped.  It's got plenty of power to land on Ike, a 4 man crew that can hop out and plant some flags for the experience, and then disconnect the lab section, leaving that on the ground.  Rendezvous with the fuel dump and lander in Duna orbit for some more flag planting, and then return to Kerbin where it will attach the Hitchiker module to the booster to deorbit the crew, and the tug can then wait in Kerbin orbit for it's next mission.

3 contracts, big experience boost for 4 crew, and the only parts that will be discarded are the fuselage section with the test parts.

 

Only slight problem is I forgot to put the crew in before I launched it...

[OHara]

On 1/18/2018 at 10:27 AM, Corona688 said:

People will go to heroic lengths to avoid landing the full-sized ISRU, just because it's so obnoxious to design with.  You can't attach radial parts to it, so ...

That is a strange feature of its configuration, and was reported as a bug (link) that got the response 'by design'.   I'll argue there that that detail of the design-spec looks very much like a typo.  For myself, I change that rule with module-manager.

Spoiler

@PART[ISRU] {
// let things attach to the ISRU surface (not let ISRU attach to other parts' surfaces, as stock does)
// flags: stack, srfAttach, allowStack, allowSrfAttach, allowCollision
@attachRules = 1,0,1,1,0
// was 1,1,1,0,0
}

 

[Corona688]

22 hours ago, OHara said:

That is a strange feature of its configuration, and was reported as a bug (link) that got the response 'by design'

It's a rock crusher and chemical reaction vessel full of moving parts which gets really, really hot in operation.  Radially attaching to it makes no more sense than radially attaching to the hot parts of an engine.

[XLjedi]

2 minutes ago, Corona688 said:

It's a rock crusher and chemical reaction vessel full of moving parts which gets really, really hot in operation.  Radially attaching to it makes no more sense than radially attaching to the hot parts of an engine.

How bout wings?  ...do you think it might melt em or somefin?

I was contemplating something like this maybe?  ...but in a Mk3 size?

 

[Corona688]

3 hours ago, XLjedi said:

How bout wings?  ...do you think it might melt em or somefin?

I was contemplating something like this maybe?  ...but in a Mk3 size?

No clipping was required to get it there, because the small ISRU has hardpoints.

It also operates in very derated fashion for this convenience.  Apparently wrapping an insulating attachment casing around something which demands cooling causes it to run hot, who would have thought.  It's a game mechanic called a "trade-off".

Edited January 21, 2018 by Corona688

[XLjedi]

1 minute ago, Corona688 said:

The small-size ISRU operates in very badly derated fashion because of its size and extra hardpoints.  It's a game mechanic called a "trade-off".

I agree, you should adapt your design to the more efficient one.

[Corona688]

Just now, XLjedi said:

I agree, you should adapt your design to the more efficient one.

It weighs four tons and lacks the necessary hardpoints.  it's a game mechanic called a "trade-off".

[XLjedi]

15 minutes ago, Corona688 said:

It weighs four tons and lacks the necessary hardpoints.  it's a game mechanic called a "trade-off".

C'mon, you can do it!!  ...typical payload for one of your heavy SSTOs (or rocket?) is easily 10x that.

Interesting edit though, I didn't actually notice the little one had radial attachment.  Kinda puts me in the mindset where I think that might be a bug then?  Or maybe the big one should've had radial mounting as I saw someone else suggest in the thread?  I can see where folks might draw that conclusion now.  Although, I don't really see an absolute need for it on either.

How did you get your big ISRU landed on Minmus?  Big rocket?

 

[Corona688]

2 minutes ago, XLjedi said:

Interesting edit though, I didn't actually notice the little one had radial attachment.  Kinda puts me in the mindset where I think that might be a bug then?

The small one is in an insulated case, I  think.  That stops it from frying things, but makes it prone to overheating.  The big one is caseless.

2 minutes ago, XLjedi said:

How did you get your big ISRU landed on Minmus?  Big rocket?

Hard to see, but it's got a pair of LV-909's attached to the underside with BZ-52 radial attachment points.

[XLjedi]

4 minutes ago, Corona688 said:

The small one is in an insulated case, I  think.  That stops it from frying things, but makes it prone to overheating.  The big one is caseless.

Hard to see, but it's got a pair of LV-909's attached to the underside with BZ-52 radial attachment points.

Interesting theory on the insulated case...  Thankfully the big one doesn't fry things on mine cuz I put a huge radiator on it, and it doesn't have to do too much rock crushin' thanks to the drills that bring up the ore thru a tube in small-ish pellet size.

You should post your reusable (or not reusable) lander design that got your ISRU from Kerbin to Minmus.  I would give it a try!

[Ultimate Steve]

I'm transitioning from early to mid career right now and I'm starting to design things to either stay in one spot indefinitely or be reused. However, I'm actually reusing spaceplanes, at least. I don't hit recover, I bring out a separate refueling rover.

[XLjedi]

27 minutes ago, Ultimate Steve said:

I'm transitioning from early to mid career right now and I'm starting to design things to either stay in one spot indefinitely or be reused. However, I'm actually reusing spaceplanes, at least. I don't hit recover, I bring out a separate refueling rover.

My biggest issue lately has been the 1.3.1 update and its very damaging effect on spaceplanes and equipment/bases left planet side.  Hoping they fix that bug quickly as it's kinda forcing me to keep everything mobile and off the surface as much as possible.  If the Ker-bounce doesn't destroy the base or the spaceplane, it might smash the nose gear up into the spaceplane for permanent displacement/damage that would also compound with time.

Just be careful leaving those planes on the ground!

Edited January 22, 2018 by XLjedi

[Corona688]

2 hours ago, XLjedi said:

Thankfully the big one doesn't fry things on mine cuz I put a huge radiator on it

1. You didn't attach anything to your ISRU's exposed, spinning, red-hot guts, just glitched them there.  Blowing up the ISRU will expose them hovering on elfin magic.
2. The big ISRU's guts are supposed to be hot.  Attaching cold things to it will stop it from working.
3. Squad didn't implement this restriction in subatomic detail, just barred you from building there at all.

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You should post your reusable (or not reusable) lander design that got your ISRU from Kerbin to Minmus.  I would give it a try!

https://kerbalx.com/Corona688/8LMH-Ergrates

It's got lots of room for improvement.  You can get away without RCS or improved reaction wheel, surprisingly, but it's not exactly comfortable to fly.  I'm just afraid to touch it lest I mess up its balance again.

 

Edited January 22, 2018 by Corona688