SSTO Orange Tank Orbital Refuel-er?

[m4rt14n]

Hi,

I'm building a massive mothership in orbit with 4 Orange Tanks with spaceplanes, rovers, landers, satelites docked. My question is after I used up the fuel to go to Jool or something like that and back, is it possible to Refuel the tanks with SSTO spaceplanes?

My guess that the plane would need to go to LKO 100km with a full/half orange tank and dock to transfer fuel; then return to KSC with the now empty tank safely. If anyone has ever done it, can you post me links/pics? I need tips for the SSTO constructions. Also no mods beside Mechjeb...

Thanks a bunch

Edited January 31, 2014 by m4rt14n

[Keymaster89]

I think it's possible, but u have consume a good amount of fuel in the process that was meant to go in the mothership because u'll need for sure a good number of jets and engines to make that mass able fly.

SSTO IMO aren't good for resupply, but as orbital bus for Kerbals and little payload lifter are perfect.

U should consider, instead of doing 8 or more SSTO flys, to build a single 4 orange tank refueler module... launch it, refuel and then destroy it or recycle it as a new tanker station...

[Claw]

Hmm, I have not tried to deliver such a large payload with a space plane yet. It is completely possible. I have been delivering tanks via rocket because a space plane of this kind would be quite large. So the main problem will be maneuvering and docking in orbit. But again, completely possible. I think there are several youtube videos of people delivering orange tanks, but they are quite large.

But maybe I'll take up this new challenge.

EDIT: By the way, if you're just looking for SSTO, you can do that with a rocket instead of a space plane and it will be a bit simpler. It won't necessarily be fully recoverable like a space plane, but you can make SSTO rockets with TurboJet boosters.

Edited January 30, 2014 by Claw

[m4rt14n]

But maybe I'll take up this new challenge.

I'll race you to it

[Claw]

I'll race you to it

Maybe tonight, haha!

[capi3101]

Okay...so you're wanting to build a spaceplane that can deliver the equivalent of an X200-32 (largest grey tank) and RCS, and possibly extra Liquid Fuel cannisters, right?

That's eighteen tonnes for the tank, 1.1 tonnes for each extra Mk1 Fuselage (I've had problems attaching Mk2 Fuselages radially, otherwise I'd be recommending thems) - say four for 4.4 tonnes, the large RCS tank weighs 3.4 tonnes, eight RCS blocks weigh 0.4 tonnes aggregate, the RCL-01 probe core weighs 0.5 tonnes, a pair of small battery packs will weigh 0.01 tonnes, and a pair of unshielded solar panels weigh .035 tonnes. Total mass of all this crap is 26.745 tonnes. I'ma gonna say you need three Turbojets for that, three Mk2 Fuselages in the core, two pairs of wing connectors, five pairs of swept wings, two pairs of small control surfaces for elevons, a pair of AV-R8 Winglets for canards, another pair of AV-R8s for rudders, landing gear and a total of 34 ram air intakes. Total mass should be 34.625 tonnes. I'd recommend breaking the single largest grey tank into four FL-T800 (long skinny tanks) and putting them away from the centerline.

I dunno - that sounds like it'd work to me, though for rendezvous and docking you might consider adding a low thrust engine to the end of the FL-T800s, say a pair of 48-7S. Unless you want to do all your rendezvous and docking maneuvers on RCS only (which, trust me, you probably don't have time for). Downside to that - you'd be taking the fuel for docking out of what you meant to send up as payload. I have no qualms suggesting you do that with the big RCS tank, since that almost always has waaaaaaay much more than you need for docking purposes. Might suggest an extra pair of FL-T100s though specifically for rendezvous maneuvers. Shouldn't screw up anything.

Now, 26.745 tonnes in a rocket is easy. Slap on a big stack decoupler, another probe core, an X200-8 and a 48-7S; you don't need much more since all you're doing is a rendezvous and docking - that adds another 5.5 tonnes of equipment, for 32.245 tonnes total payload. An SSTO booster for that would mass about 830 tonnes and consist of seven stacks of three orange tanks equivalent of fuel and a Mainsail each. Make sure they're well strutted. Throttle back as necessary after the gravity turn to keep it around the top of the green zone of the gee meter and you should be golden.

The spaceplane option sounds easier to me - at least, it sounds like it'd take fewer overall parts; then again, I'm only partially confident about the "design" I outlined above. Both are valid solutions, though.

[Captain Sierra]

m4rt1n, the ammount of fuel you want to lift is a challenge for SSTOs. Record weight I've seen an SSTO lift was 40 tons, but it was using some totally unrealistic techniques (it had the wings copied so it was really two wings for the size of 1 and had an over 8-1 intake engine ratio, using B9). Sans rediculous techniques, best payload I've ever seen was 15 tons.

Now, I've tried without air hogging and wing clipping to deliver one of my standard fuel cans (standard docking port and 1.25-2.5m adapter OR Sr. docking port, large RCS tank, orange tank, same docking port setup on other end). I can put that in orbit without asparagus, as the whole thing, including rednezvous/docking upper stage, weighs less than 50 tons, which is starting to push my limits of single layer parallel staging.

[m4rt14n]

Can you half a tank refuel, use the rest for fuel maybe? Is it easier to launch vertical then coast down to land?

[dualmaster]

This is actually something I've been working on for a little while - I want an SSTO that can put an orange tank and one of the large RCS fuel tanks into orbit. Thus far I've come pretty close - I've managed to rendezvous without ~80% of an orange tank remaining. Unfortunately, it requires some excessive air hogging which I find kinda lame. Without air hogging it will be pretty tough.

I don't have any pics at the moment, but I'll see if I can get some later.

[SuperBigD60]

You know, if you'd allow FAR and B9, this challenge becomes trivial

[capi3101]

Can you half a tank refuel, use the rest for fuel maybe? Is it easier to launch vertical then coast down to land?

You might be able to - I suppose I did forget the bit where you have to switch over to rockets for the final ascent and all that. The big difference there is one of your own personal gratification: the spaceplane is "reusable", the rocket I suggested is most certainly not, but on the other hand it'd be almost 100% guaranteed to reach your mothership still fully loaded.

[1greywind]

With stock parts ~36 ton payload to LKO SSTO lifter will be somethat 200 ton on runway and 300-350 parts (~150 parts for wings, 100 for engines, intakes, fuel lines, rest for fuelage and auxilary).

[arq]

I have done this. The Procedural Wings mod works miracles with making large spaceplanes. And a SSTO can get payload fractions over 30%, so on the runway I would expect it to be in the 120-150t range. Don't be afraid to use large engines like the Mainsail or T30 clusters for the rocket stage.

[dualmaster]

Here is my Hogger Refueler at 100 km orbit with almost a full orange tank and a large RCS tank.

Javascript is disabled. View full album

Can't seem to figure out the right tags to get it to show up here.

Anyways, it obviously abuses air hogging and also has some clipping via cubic octagonal struts (mostly for the sake of appearance rather than necessity). Still, it flies pretty well and was fun to make!

Edited February 28, 2014 by dualmaster

[Claw]

Well, I already have SSTO rockets that carry an 80t payload with about 30% payload ratio (260ish tons).

I've already started work on a space plane capable of lifting a full orange tank (36t). My goal is better than 40% payload ratio or it won't be worth it with a space plane. I've seen larger payloads, but this is my start. So ultimately I'm aiming for around 70-80 tons on the runway. All stock.

Edited January 30, 2014 by Claw

[capi3101]

Good luck - 70t is about the mass I had on the Auk III and I never could get that one off the ground for all the structural problems it had.

[Claw]

My initial prototype currently weighs a bit over 72 tons. It's flown above 25km and needs more work, but so far it's on track.

[Pecan]

Well, I already have SSTO rockets that carry an 80t payload with about 30% payload ratio (260ish tons).

Craft file? I'm still playing-around optimising pure-rocket launch vehicles but 30% with jet assist has to be worth it. I want to complete my 'set' first because over about 10t my VAB jet designs have become 'moar' spam :-( Love to see how you're doing it. In the meantime, as you know, I've been playing with spaceplanes when rocket-launch after rocket-launch has got boring. The hope is that this'll better inform my rocket designs though - while they're fun spaceplanes are too much of a pain to get into orbit for me to use regularly. ... At least while resuability isn't really an issue.

[1greywind]

Check this - http://forum.kerbalspaceprogram.com/threads/67870-Heavy-SSTO-lifter-(-40-ton-payload-to-LKO)-prototype

I have not yet finished work on it, but it is already able to deliver 1 orange tank to LKO.

[Alistone]

I've beel playing around with this idea for the past few days.

As a spaceplane my large orange tanks are difficult to control; difficult to land; a bit unstable as wing wiggle can ripple them apart.

The wheels are a real pain too; since it is soo heavy it is very difficult to land without destroying the wheels (and most everything else).

I was transitioning to trying to make a "shuttlecraft" that could take of vertically to avoid the wheel problem, but that brings it's own set of challenges (flipping over).

It's going to take a lot of work, but I think it can be done stock. Just before coming to work today I had a "umbrella" design that was relatively stable 10 TJE on "T"s symetrically (VAB) above the orage tank (low CoG relative to thrust to keep it upright) and pulled an orange tank easily to over 20,000 before returning to KSP to land.

Future improvements incoming to push it further into space; but I assume you'd be satisfied if it was a VTOL craft instead of a traditional spaceplane.

I don't do "clipping" and I don't use mods, so it is particularly challenging and figuring out the transition to rocket propulsion will likely involve some explosions during testing.

I am coming to the conslusion fast that if I want to build a usable and decent looking SSTO space plane, I am going to have to do away with my aversion to enabling clipping.

Edited January 30, 2014 by Alistone

[Claw]

Craft file? I'm still playing-around optimising pure-rocket launch vehicles but 30% with jet assist has to be worth it. I want to complete my 'set' first because over about 10t my VAB jet designs have become 'moar' spam :-( Love to see how you're doing it. In the meantime, as you know, I've been playing with spaceplanes when rocket-launch after rocket-launch has got boring. The hope is that this'll better inform my rocket designs though - while they're fun spaceplanes are too much of a pain to get into orbit for me to use regularly. ... At least while resuability isn't really an issue.

I'm sorry. I must retract my statement slightly. My 80t lifter isn't an SSTO yet, but it does have a 30% payload ratio. I've been iterating designs of a family of 20t, 40t, 60t, 80t lifters and the 60/80t aren't SSTO. They are currently two stage as I ditch the jets during ascent (with parachutes to recover). The rocket portion finishes orbital ascent/insertion, then acts as a tug for docking/deorbit. So my 80t design is not an SSTO.

I don't have a file hoster at the moment, but here's a picture of my 20t lifter (also about 30% payload). It's probably a better picture to show anyway as it's a little cleaner and you can see what's going on better. It's designed to ditch the TurboJets, but you can also hold onto them if you desire. It wasn't meant to be reusable, so no guarantees on landing.

So I've just kept scaling this up. Turns out whatever rocket fuel you have up top, you'll need on the bottom (plus a little as the payload gets bigger). Also, if I wanted to use this as an SSTO it needs adjustment to the RCS system.

EDIT: I added an orbital shot too. Not the best ascent, but here it is in 80x80 orbit with about 150ish dV left. It was designed to have 500 dV left after ditching the TurboJets.

Edited January 30, 2014 by Claw

[Claw]

I want to complete my 'set' first because over about 10t my VAB jet designs have become 'moar' spam :-(

Depends on what you mean by moar spam. On my rockets I have been using only 1 intake per engine, but it takes a lot of engines to lift 240+ tons (which is what my 80t lifter weighs right now). I haven't spent a lot of time on the 80t because my goal has been to make a 100t lifter with TurboJet boosters. Past 40t the rocket actually becomes the weak link and tears itself apart. The TurboJets start producing too much thrust at high altitude and you have to pay attention to acceleration and payload mass or it crushes itself.

[Rhomphaia]

That's eighteen tonnes for the tank, 1.1 tonnes for each extra Mk1 Fuselage (I've had problems attaching Mk2 Fuselages radially, otherwise I'd be recommending thems) - say four for 4.4 tonnes,

If you aren't going to use Mk2 or Mk3 fuselages then you are better off removing the oxidizer from rocket fuel tanks, other than round-8s and oscar-Bs they have a better ratio than the MK1 fuselage.

[Claw]

If you aren't going to use Mk2 or Mk3 fuselages then you are better off removing the oxidizer from rocket fuel tanks, other than round-8s and oscar-Bs they have a better ratio than the MK1 fuselage.

That's true, but you also sacrafice some structural integrity using rocket tanks. So care needs to be taken when placing.

[Captain Sierra]

That's true, but you also sacrafice some structural integrity using rocket tanks. So care needs to be taken when placing.

Three words: Kerbal Joint Reinforcement.

Never have I had a problem with a serially staged rocket since installing that.