Kerbal Space Shuttle and rocket Economics

[KerikBalm]

Let me start by saying I've been using SSTOs way too much lately, and I don't actually have a good idea what the cost per ton is for normal rockets.

The main thing that killed the space shuttle economics was the cost of refurbishing the space shuttle, and maintaining the facilities to store them, etc.

In KSP, we don't have those costs. 100% recovery, no costs at all to use something again if it lands back on the runway. So... could a space shuttle make economic sense in KSP, given the perfect reusability savings?

Last night I had a crack at making a shuttle style launcher, using mk3 parts.

Despite the videos I saw on youtube, it wasn't so hard, and my first attempt got to space, although I didn't try to see if I could get to orbit, as I already noticed some flaws to correct.

Design 2 got to orbit.

Tweaked it a bit more, and for attempt 3 I got it to space carrying a payload (~18 tons)

*Note, I didn't actually put much development into the orbiter. It has no landing gear, and I haven't checked if the wings are positioned in a way that will actually make it stable in horizontal gliding flight). This was just a test of the asymetric launch system.

However, when I calculated the cost of getting this payload to orbit... It came out to 26,898 funds (plus whatever the onboard fuel in the orbiter cost)

That is about 1,500 funds per ton to orbit... and I still have to deorbit and land the orbiter like a SSTO spaceplane.

In comparison, my SSTO that carries cargo in a mk3 bay costs ~100 funds per ton to orbit

My SSTO that carries cargo way too big to fit in a mk3 bay costs between 175 - 250 funds per ton to orbit.

This semi-reusable non-airbreathing shuttle is roughly 6 to 15 times more expensive than my airbreathing SSTO spaceplanes.

I was wondering if my costs per ton for this shuttle are typical for shuttle designs?

I never did look into non-airbreathing SSTOs, what do they typically cost per ton?

I haven't designed staging pure rocket lifters with cost in mind for a while now (I'll throw one together in sandbox, but ignoring cost)

I will admit... it does look cool in orbit though... it looks much more elecant than my mk3 spaceplanes with engine nacelles, intakes, added length due to carrying much more onboard fuel, more control surfaces because it needs to be able to fly horizontally full and empty... etc.

For reference, my shuttle's main tank was 2x orange tanks capped at both ends with nosecones, and then two pairs of the kickback SRBs (4 total, not 2, we need more powerful SRBs). It has 4x monoprop engines, and a 2.5 monoprop tank inside the main bay. I'd be better off using LFO tanks and the main engine at low thrust... but the monoprop as an OMS supply seems cooler. Even if the real SS OMS was hypergolic bipropellent.

I doubt SRB recovery would improve the economics of it much.

I'm tempted to use this design in my career save for fun, but the economics of it seem so poor.

The ascent is faster than with a SSTO (somewhat due in to a better framerate but its not fair to compare a launcher for 20 tons vs a launcher for >120 ton payloads), so maybe a working shuttle would be a good compromise between time and economics.

However, I doubt it will actually end up being any cheaper.

Edited September 14, 2015 by KerikBalm
spelling, sentence fragments

[The_Rocketeer]

It almost certainly won't. I've learned since playing KSP what an economic white elephant the real STS was.

If anything I would guess that your shuttle is considerably MORE economical than RL, since it seems to me that you must have used a Buran-style under-tank rocket which the NASA shuttles didn't (if not then I'm slightly awed by your success - I've spent many hours refining my designs to get them into orbit). The issues of CoM shift were resolved with highly gimballed engines that splayed out in different directions, such that the assembly rose on a multi-legged 'stool' of thrust, rather than a single pedestal (as rockets normally do). This results in huge fuel wastage just for extra stability.

[Nansuchao]

In stock KSP a Shuttle vehicle is interesting as a challenge, not good for much more. If you try in RSS, you'll find that the only safe way to reach orbit with a plane is the shuttle way.

[More Boosters]

Let me start by saying I've been using SSTOs way too much lately, and I don't actually have a good idea what the cost per ton is for normal rockets.

The main thing that killed the space shuttle economics was the cost of refurbishing the space shuttle, and maintaining the facilities to store them, etc.

In KSP, we don't have those costs. 100% recovery, no costs at all to use something again if it lands back on the runway. So... could a space shuttle make economic sense in KSP, given the perfect reusability savings?

Last night I had a crack at making a shuttle style launcher, using mk3 parts.

Despite the videos I saw on youtube, it wasn't so hard, and my first attempt got to space, although I didn't try to see if I could get to orbit, as I already noticed some flaws to correct.

Design 2 got to orbit.

Tweaked it a bit more, and for attempt 3 I got it to space carrying a payload (~18 tons)

http://i.imgur.com/m9kOsCx.png?1

*Note, I didn't actually put much development into the orbiter. It has no landing gear, and I haven't checked if the wings are positioned in a way that will actually make it stable in horizontal gliding flight). This was just a test of the asymetric launch system.

However, when I calculated the cost of getting this payload to orbit... It came out to 26,898 funds (plus whatever the onpoard fuel in the orbiter cost)

That is about 1,500 funds per ton to orbit... and I still have to deorbit and land the orbiter like a SSTO spaceplane.

In comparison, my SSTO that carries cargo in a mk3 bay costs ~100 funds per ton to orbit

My SSTO that carries cargo way too big to fit in a mk3 bay costs between 175 - 250 funds per ton to orbit.

This semi-reusable non-airbreathing shuttle is roughly 6 to 15 times more expensive than my airbreathing SSTO spaceplanes.

I was wondering if my costs per ton for this shuttle are typical for shuttle designs?

I never did look into non-airbreathing SSTOs, what do they typically cost per ton?

I haven't designed staging pure rocket lifters with cost in mind for a while now (I'll throw one together in sandbox, but I haven't tried to build a vertical launc

I will admit... it does look cool in orbit though... it looks much more elecant than my mk3 spaceplanes with engine nacelles, intakes, added length due to carrying much more onboard fuel, more control surfaces because it needs to be able to fly horizontally full and empty... etc.

For reference, my shuttle's main tank was 2x orange tanks capped at both ends with nosecones, and then two pairs of the kickback SRBs (4 total, not 2, we need more powerful SRBs). It has 4x monoprop engines, and a 2.5 monoprop tank inside the main bay. I'd be better off using LFO tanks and the main engine at low thrust... but the monoprop as an OMS supply seems cooler. Even if the real SS OMS was hypergolic bipropellent.

I doubt SRB recovery would improve the economics of it much.

I'm tempted to use this design in my career save for fun, but the economics of it seem so poor.

The ascent is faster than with a SSTO (somewhat due in to a better framerate but its not fair to compare a launcher for 20 tons vs a launcher for >120 ton payloads), so maybe a working shuttle would be a good compromise between time and economics.

However, I doubt it will actually end up being any cheaper.

Hey, I've been thinking about the exact same thing but I haven't been able to test anything since I currently don't have my computer with me. I think the main problem here is the underpowered SRBs; I believe you can improve the situation by using the SRBs from the SpaceY parts pack.

A few notes:

- Rhino seems a bit overpowered for this case, it may have good ISP but it also has huge weight at 9 tonnes so you may want to try weaker, lighter LFO engines with stronger SRBs (you'll have to consult a mod or rightfully buff the Kickbacks for this)

- You should try to recover the SRBs.

- 3.75m tanks may be more sensible as two oranges have more drag, at least they look like they do.

- You don't have to adhere strictly to the real life design, it wasn't very practical after all. You could for example try R.A.P.I.E.Rs (like 3-4 of them) at the orbiter's main body to make landing easier, or use a mod 3.75m version of it.

But of course I never got the chance to try any of this and I am hardly an SSTO expert so take these for what they are worth.

It almost certainly won't. I've learned since playing KSP what an economic white elephant the real STS was.

If anything I would guess that your shuttle is considerably MORE economical than RL, since it seems to me that you must have used a Buran-style under-tank rocket which the NASA shuttles didn't (if not then I'm slightly awed by your success - I've spent many hours refining my designs to get them into orbit). The issues of CoM shift were resolved with highly gimballed engines that splayed out in different directions, such that the assembly rose on a multi-legged 'stool' of thrust, rather than a single pedestal (as rockets normally do). This results in huge fuel wastage just for extra stability.

Well he is using a Rhino and he clearly kept the engine on the orbiter, so I'd say the ridiculous thrust that engine has for space standards (and this payload really, you're lifting how many tons to orbit now?) reduces your losses to stability allowing you to fix the center of thrust with a far smaller engine inclination.

Edited September 14, 2015 by More Boosters

[Johnny Wishbone]

The space shuttle was sold to Congress and the American taxpayers as a "low cost, reusable" vehicle to space. However, it was designed to be a money pit (even before the Air Force got their dirty fingers into it and messed up the design even more). NASA administrators saw what happened to funding for Apollo once its goals were achieved and knew if they wanted continuous funding for manned space programs, they would need a vehicle that would require continuous funding while appearing to be keeping costs down because so much of it was "reusable". You just had to ignore the fact that pretty much every part of the orbiter other than the crew cabins and cockpit needed to be ripped apart and rebuilt after every mission.

I've never understood the love for the space shuttle, in real life, or by people playing this game. (I'm not judging you, if you are someone that loves it; I just don't get it.) Statistically, it was the most dangerous vehicle ever flown into space, it was the most expensive ever flown into space, and it was an overall piece of junk that could barely meet its most basic mission requirements (and had far less capability than the Saturn V rocket it replaced). Personally, I believe the space shuttle set the American space program back by at least 10 years, as that is how long its going to take for us to re-design the rockets we already mastered (and lost) and get us back into manned spaceflight.

Edited September 14, 2015 by Red Iron Crown
Easy with the language.

[GoSlash27]

KerikBalm,

Heck, my shuttle only lifts about 7 tonnes. I'm curious to see what your launch stack looks like.

Here's mine:

Yeah, the economics are just about as ugly as you can get.

Best,

-Slashy

[More Boosters]

KerikBalm,

Heck, my shuttle only lifts about 7 tonnes. I'm curious to see what your launch stack looks like.

Here's mine:

http://i52.photobucket.com/albums/g13/GoSlash27/KSP/Shuttle%20Kourageous/Kourageous3_zps2y0ogul9.jpg

http://i52.photobucket.com/albums/g13/GoSlash27/KSP/Shuttle%20Kourageous/Kourageous1_zpsiovlv8m6.jpg

Yeah, the economics are just about as ugly as you can get.

Best,

-Slashy

Technically you don't even need to incline your engines if you balance the center of thrust by adding liquid fuel boosters connected under the external tank. Once the external tank dries up, dump it and the balancing LFBs. Maybe that would work? Anyway I've seen some shuttles that lift oranges and more to orbit on Youtube. Once again I haven't had the chance to try this so take this for what its worth, but maybe your shuttle building isn't as refined as your SSTO building?

[KerikBalm]

" Rhino seems a bit overpowered for this case, it may have good ISP but it also has huge weight at 9 tonnes so you may want to try weaker, lighter LFO engines"

Well, its Isp at launch is pretty bad, not as terrible as it used to be. Anyway, When I launched the orbited without a payload, I throttled it to 50%, otherwise it produced too much thrust.

With a payload, I could throttle it to 100% and with maximum pitch without resorting to the vernors, it was working and allowing me to pitch over into a gravity turn.

Part of it is that I just didn't want to bother with a engine cluster, and part of it was looks.

I could also try using a mk3 to 2.5m adapter and putting a mainsail on there (I a skipper would not be sufficient) I don't know if saving 3 tons and some better atmospheric Isp is worth the loss of ~30 vacuum Isp.

The other thing is that the Rhino has one of the largest gimbal ranges in the game -> 4 degrees.

Radial engines get 8.0 degrees of gimbal.

The mainsail, skipper, and mammoth get 2.0

The Rapier, LV-T45, and 48-7s get 3.0

The LFB gets 1.5

The KR-2L gets 4.0 degrees of gimbal. A high gimbal is what you want for a design like this.

I supposed I could use a pair of Thuds..

A Poodle gets 4.5 degrees of gimbal, but is totally unsuited for the main engine.

LV-909s get 4 degrees of gimbal as well but are just as bad as the poodle for this use.

I'm going to stick with the KR-2L for now due to high gimbal and vacuum Isp.

"with stronger SRBs (you'll have to consult a mod or rightfully buff the Kickbacks for this)"

Well, I could switch from pairs of SRBs to trios of SRBs... but that will then neccesitate a stronger main engine to balance the added thrust on that sie of the CoM (with a KR-2L, I could just go from 50% thrust ot 75% thrust). This will be even worse if I have a heavier payload strapped to the side of the tank+SRB combo.

20 tons is already quite bad. I don't want to have to restrict payload mass even more to maintain balance.

The LFB is what gives me control because I can throttle that one, so I'd like to have excess thrust so I can have it at lower throttle on launch, and throttle it up as the SRB fuel is consumed and the main tank empties (which will shift the CoM, and make it want to pitch over)

"3.75m tanks may be more sensible as two oranges have more drag, at least they look like they do."

Its inline oranges, not side by side. I'm pretty sure they are lower drag. a 2.5m diameter cross section rather than 3.75m.

Plus I'd then need to add the 3.75-> 2.5m adapter before sticing nose cones on.

"You should try to recover the SRBs."

I'm trying to make it all stock, that would work with someone else with an all stock install. I've made recoverable SRBs before, they consist of fleas paired with LES's, and have extremely short burn times so that they land before leaving physics range.

This is absolutely not an option with fully fueled kickbacks due to the game engine (although you could stock-ish do text file editing and save file duplication to allow you to recover the SRBs, by pasting the SRB part data back into the game after you recover your orbiter/get it to orbit, and then followingthe SRBs down).

As such, I don't plan on attaching chutes, and designing the decoupling system to stop them from being destroyed during the decouple (its happened every time so far, but its never hit my orbiter+ main tank, so I don't care for now)

"You don't have to adhere strictly to the real life design, it wasn't very practical after all. You could for example try R.A.P.I.E.Rs (like 3-4 of them) at the orbiter's main body to make landing easier,"

Landing is not the problem. I often land my SSTOs without any use of engines after the deorbit burn.

The RL design was not practical because of the refurbishment costs.. which aren't there in KSP.

I've already made Vertical Launch airbreathing spaceplanes... granted they mostly fly like a horizontal launch space plane, and just have a very short burn of SRBs to launch them vertically, pitch over, and enter horizontal flight by the end of the runway (in which case the SRBs are recovered for 100%).

It is tempting to put a pair of rapiers or turboramjets on this to improve payload fraction though.

Airbreathing engines in KSP are so OPd, that one might as well just make SSTOs if you use them.

I've already taken vertical launch SSTO rockets, and stuck on some turboramjets to improve their payload capacity and enable softer parachute landings.

I am trying to adhere to:

- No airbreathing engines (at least not used to get to orbit)

- Not single stage, but most of the expensive parts are recoverable

- Does make precision landings back at KSC (ie, has significant aerodynamic surfaces... I don't want to have to quickload a dozen times to get my de-orbit burn just right)

- Asymetry for the fun - In KSP we could just make a design where the external tank is directly above/below the orbiter, and the SRBs strap on to the sides of the orbiter... no need to worry about a thrust imbalance

Edited September 14, 2015 by KerikBalm

[Red Iron Crown]

The fuel use gets a bit better if you rearrange things to avoid the thrust offset issues:

Recovers the pricey rocket engine, all it discards are the SRBs and fuel tanks. Still, it is not the most economically viable, for that I would order them so:

1. Airbreathing recoverable SSTO (fuel cost only)

2. Pure rocket SSTO (fuel cost only, but higher than airbreathing)

3. Shuttle style (fuel cost + tanks and SRBs)

4. Rocket with disposable stages (fuel cost + tanks + engines, etc)

[Warzouz]

The fuel use gets a bit better if you rearrange things to avoid the thrust offset issues:

https://dl.dropboxusercontent.com/u/61004449/KSP/1.0.4/screenshot838.png

Recovers the pricey rocket engine, all it discards are the SRBs and fuel tanks. Still, it is not the most economically viable, for that I would order them so:

1. Airbreathing recoverable SSTO (fuel cost only)

2. Pure rocket SSTO (fuel cost only, but higher than airbreathing)

3. Shuttle style (fuel cost + tanks and SRBs)

4. Rocket with disposable stages (fuel cost + tanks + engines, etc)

For "Pure rocket SSTO", you also have the recovery price which is usually 2 to 5% because you mostly never land on the runway. But true, most of the cost comes from the fuel.

Edited September 14, 2015 by Warzouz

[Red Iron Crown]

A pure rocket plane-style SSTO is just as easy to land on the runway as an airbreathing one, and an airbreathing VTOL SSTO is just as difficult to land precisely as a pure rocket one. It's not the propulsion that makes the difference for recovery, but the landing method.

[More Boosters]

I think it's worth considering that the real life space shuttle used cryogenic engines with greater efficiency so it may also be the engines in KSP not doing it justice.

That, or STS-inspired designs need further work to be adapted properly to KSP.

As soon as I get to play KSP I have a few ideas from mods like the cryogenic engines from the similarly named mod and a cluster of LANTERNs from Atomic Age. Maybe others would like to try in my place?

[KerikBalm]

Technically you don't even need to incline your engines if you balance the center of thrust by adding liquid fuel boosters connected under the external tank. Once the external tank dries up, dump it and the balancing LFBs. Maybe that would work? Anyway I've seen some shuttles that lift oranges and more to orbit on Youtube. Once again I haven't had the chance to try this so take this for what its worth, but maybe your shuttle building isn't as refined as your SSTO building?

Slash-I can't take pictures right now (not home yet, wouldn't be appropriate to start up KSP) - but I could upload the craft file:

https://www.dropbox.com/s/8pznz6wu0jxm6g6/Space%20Shuttle.craft?dl=0

More Boosters-> That is sort of "cheating". The challenge is to have all liquid fuel engines carried on the orbiter and recovered. You are proposing more of a Buran style launch, which is easier and less recoverable (it may be better IRL, but this is KSP)

Johnny Wishbone-> I think you are a bit too cynical. I doubt it was designed to be a money pit, at least not a money pit per launch.

Sure, the aerospace contracters would like regular business - but they'd get that if there were low refurbishment costs and 50 launches per year, or high refurbishment costs and 2 launches per year.

In the end, yes, it turned out terrible. Too many compromises. The original proposals before the airforce got involved (which was neccessary to obtain funding, but in the end killed it) with small wings, a smaller payload bay, and much less cross range capability look much more appealing.

NASA was dreaming up a huge moneypit for aerospace contractors with an entire STS, not just the shuttle. I highly doubt the engineers working on the project intentionally made bad proposals, or that NASA picked the one that would prevent the rest of the STS from becoming a reality.

Hindsight is 20/20...

https://en.wikipedia.org/wiki/Hanlon's_razor

"Never attribute to malice that which is adequately explained by stupidity."

- - - Updated - - -

Red- Hehe, I see you posted a picture of exactly what I was describing as I was editing my post.

A pure rocket plane-style SSTO is just as easy to land on the runway as an airbreathing one, and an airbreathing VTOL SSTO is just as difficult to land precisely as a pure rocket one. It's not the propulsion that makes the difference for recovery, but the landing method.

I think we have another case of people thinking that airbreathing implies spaceplane, and pure rocket implies not a space plane.

But don't make a mistake of your own... althought you don't explictely say it, it almost seems implied...

VTOLs can be quite easy to land precisely.

If it is a tail sitter that lands under parachutes, and launches vertically like a rocket, and has no wings, it can be quite hard to land precisely.

Or it could be something with vertical lift jets, that otherwise flies horizontaly.

Or it could be like what I use on bodies that aren't kerbin and lack a runway+its associated extremely flat grassy surrounding:

Capable of stable horizontal aerodynamic flight -> fly right over the target areaat low altitude, extend landing legs and pitch full up, pop chutes and apply a puff of thrust if needed to soften the landing.

To me, its not the landing method, its the "flight method"

Does it proceed along a ballistic arc, or do you have aerodynamic surfaces to allow you to alter your trajectory, to refine it... to make "mid course corrections".

The more you can alter your trajectory, the easier it is to land where you want.

[More Boosters]

More Boosters-> That is sort of "cheating". The challenge is to have all liquid fuel engines carried on the orbiter and recovered

In that case, perhaps you could have high efficiency but still small engines mounted horizontally? Maybe you'll be allowed to keep your main engine without inclination then?

Some sparks, perhaps?

[Warzouz]

... If it is a tail sitter that lands under parachutes, and launches vertically like a rocket, and has no wings, it can be quite hard to land precisely.

...

But even though, the recovery cost variation is very slim.

- Land on runway or launchpad = 100%

- Land anywhere on KSC ground = 98%

- Land at 50km from KSC = 97%

- Land at 100km from KSC = 95%

- Land on the other half of Kerbin = 20%

It's very easy to land at less than 50km from KSC with a non directive object using only airbrakes. There is not much difference with perfect runway landing. The only thing you want to know is where to deorbit and burn dV.

If the recovery costs where much higher, SSTO rocket might not be as interesting.

[KerikBalm]

If my craft costs 100,000 funds, and the fuel cost is 5,000 -> then a 95% recovery results in it costing twice as much to launch a payload.

Even a 98% recovery would represent a 40% increase in costs.

[Frozen_Heart]

With my shuttle I found that it cost a lot more to launch than conventional rockets, but is a tiny bit cheaper if you manage to land the orbiter again.

SSTOs blow everything else out of the water costwise though. You only have to pay for the payload and fuel. I'm awful at making those though. :/

[Warzouz]

If my craft costs 100,000 funds, and the fuel cost is 5,000 -> then a 95% recovery results in it costing twice as much to launch a payload.

Even a 98% recovery would represent a 40% increase in costs.

Let's take some more real data : 15% to 20% fuel cost is more realistic for a rocket SSTO (space plane don't miss the runway).

For example the 150T launcher

- Wet cost = 260k

- Dry cost = 210k

- 100% recover = 50k (cost, not recovered fund)

- 98% = 55k

- 97% = 58k

-> 15% variation (as of 97% easy average / full recovery)

If you use SSTO spaceplane, sure you want to land on the strip. That is quite easy with little practice

[tseitsei]

Spaceplanes are most cost efficient since it only costs the price of fuel used to send something to orbit and payload fractions can also be very good in proper designs (30% is quite easy to achieve on smaller scale planes and >20%-30% is quite simple with bigger designs as well)

On rockets you lose some money even if you use parachutes to recover early stages because you can't land them neatly on the runway...

[More Boosters]

Just saw this comment on youtube:

Why dont you just stick 2 shuttles on the fuel tank: problem solved

How would this work out? Can you even put two vehicles into orbit at once? I mean the human factor would prevent it, no?

Edit:

Also found this:

Sure it uses LFBs and not SRBs but it does the job.

Edited September 14, 2015 by More Boosters

[KerikBalm]

Let's take some more real data : 15% to 20% fuel cost is more realistic for a rocket SSTO (space plane don't miss the runway).

For example the 150T launcher

- Wet cost = 260k

- Dry cost = 210k

- 100% recover = 50k (cost, not recovered fund)

- 98% = 55k

- 97% = 58k

-> 15% variation (as of 97% easy average / full recovery)

If you use SSTO spaceplane, sure you want to land on the strip. That is quite easy with little practice

http://n.lejeune.free.fr/ksp/cygnus_g.png

Lets look at that first rocket.

A 100% recover would be 414 funds per ton.

A 95% recover would be 539 fund per ton ->30% more per ton.

Look at the last rocket.

A 100% recover would be 329 funds per ton.

A 95% recover would be 449 funds per ton.

A 36.5% increase in cost per ton.

Getting a 100% recovery does significantly effect the cost per ton, even for non-airbreathers which have higher fuel costs.

Edited September 14, 2015 by KerikBalm

[More Boosters]

Lets look at that first rocket.

A 100% recover would be 414 funds per ton.

A 95% recover would be 539 fund per ton ->30% more per ton.

Look at the last rocket.

A 100% recover would be 329 funds per ton.

A 95% recover would be 449 funds per ton.

A 36.5% increase in cost per ton.

Getting a 100% recovery does significantly effect the cost per ton, even for non-airbreathers which have higher fuel costs.

I'd like your comment on the shuttle I posted as it seems to deliver 42t to a 200 x 200 orbit just fine, recovering all but the ET. Though I'm not sure that SSME stand in is a stock engine.

[viktor19]

When you compare big dumb boosters with reusable systems it ironically boils down to what happens when they are not flying. At first it seems like: "Shuttle can carry less payload than other rockets, but it's reusable - you can use it over and over." That's true, but what about the boats NASA made specifically for fishing boosters in the Atlantic? The story doesn't stop there, boosters are checked and new fuel has to be loaded. What about the SSMEs that have to be removed from the Shuttle? What about those 30,000 tiles?

Personally, I think that Elon Musk's middle way is just what humanity needs...

Now back to KSP. We don't have NASA's problems like someone already mentioned. Still, Shuttle replica is a nice challenge for KSP, period. You have to balance thrust, mass...for peanuts in savings. Go small, make a spaceplane! Go big, make a first stage, add a probe core, some batteries, airbrakes (and optionally, parachutes). Land where you want, when you want.

The fuel use gets a bit better if you rearrange things to avoid the thrust offset issues:

https://dl.dropboxusercontent.com/u/61004449/KSP/1.0.4/screenshot838.png

Recovers the pricey rocket engine, all it discards are the SRBs and fuel tanks. Still, it is not the most economically viable, for that I would order them so:

1. Airbreathing recoverable SSTO (fuel cost only)

2. Pure rocket SSTO (fuel cost only, but higher than airbreathing)

3. Shuttle style (fuel cost + tanks and SRBs)

4. Rocket with disposable stages (fuel cost + tanks + engines, etc)

This is literally the thing I was waiting my whole KSP life!

[GoSlash27]

The fuel use gets a bit better if you rearrange things to avoid the thrust offset issues:

https://dl.dropboxusercontent.com/u/61004449/KSP/1.0.4/screenshot838.png

Recovers the pricey rocket engine, all it discards are the SRBs and fuel tanks. Still, it is not the most economically viable, for that I would order them so:

1. Airbreathing recoverable SSTO (fuel cost only)

2. Pure rocket SSTO (fuel cost only, but higher than airbreathing)

3. Shuttle style (fuel cost + tanks and SRBs)

4. Rocket with disposable stages (fuel cost + tanks + engines, etc)

RIC,

The reason shuttles can't keep up with disposables is the tyranny of the rocket equation. Most of what's placed in orbit is not payload, so the stack is huge in comparison. All the extra fuel and oxidizer erases any savings you get from returning the engines.

Best,

-Slashy

[Skorpychan]

RIC,

The reason shuttles can't keep up with disposables is the tyranny of the rocket equation. Most of what's placed in orbit is not payload, so the stack is huge in comparison. All the extra fuel and oxidizer erases any savings you get from returning the engines.

Best,

-Slashy

That's because the shuttle's big wings and control surfaces, big main engines with heavy complex gimbal systems, and empty fuel tanks are all dry mass. The most efficient space shuttle design would have been Buran-style, with the engines under the main fuel tank, and dedicated on-orbit engines making good use of onboard fuel. And also a lifting body rather than big delta wings.

On top of that, using a rocket to launch something with wings on seems a little wasteful. I'd rather have seen it air-launched from under a bomber, or maybe this: https://en.wikipedia.org/wiki/Conroy_Virtus - I found it browsing wikipedia over the weekend, and it seems like a great idea. Get up high and up to a good velocity before releasing the shuttle and igniting the engines.