Discussion: what are the best ways to reduce launch cost?

[322997am]

So I was kinda wondering if VTVL is the best method, or there are better ways to recover rockets/reduce prices

[KerikBalm]

Airbreathing HTOL SSTOs work really well and can get ~50% payload fractions in stock.

They do take more player time. For stock, I find VTVL SSTO rockets (with parachutes to assist the vertical landing) to be good enough in career for most purposes.

[blakemw]

First helpful thing is to use the cheapest launchers. Generally this is the Twin-Boar - it has both a "thrust cost ratio" and "thrust weight ratio" significantly superior than other liquid fuel engines, other than Reliant which closely matches it (but the Reliant is very limited). Using low-cost thrust like from Twin-Boar rather than high-cost like from Vector doesn't matter that much if you're recovering, but it does mean that any losses from distance etc aren't as significant and RUD isn't such a blow.

Other than being cheap the Twin-Boar has a host of other recovery benefits. First one is it produces a ludicrous amount of drag in reverse due to the flared base, this means it slows down really well and you never have to worry about overheating during reentry and it'll also typically get down to safe drogue chute speeds without additional drag enhancers, also its fatness acts as a heat shield for the rest of the rocket further reducing heat load on the rocket. Secondly it has a 20m/s impact tolerance so you only need 2 or 3 chutes to safely land it on chutes alone. Thirdly you can drop it in the ocean and its long length and high buoyancy will protect everything higher up the stack (just quickly ninja recover before it tips over). Basically the Twin-Boar comes pretty close to being idiot-proof for recovery and barely any bells and whistles are required for recovery. Again if you're planning on quickloading until you nail the KSC having extra bells and whistles isn't such a big deal because you'll recover the cost, but if you don't want to spend your play time quickloading and just go for a 80%+ recovery for somewhere vaugely near the KSC then it doesn't hurt to keep the rocket on the cheap side.

Next: Fuel. As a general rule a RAPIER spaceplane can put a payload into orbit at about 1/3rd the fuel cost of a SSTO Rocket bcause it uses jet engines to build up most of the orbital velocity - the cost of using a spaceplane is greatly increased mission times. With rockets you can use a lot more prograde hold and 4x physics warp, with a Spaceplane you definitely want to aim for a high recovery %age. Also spaceplanes scale extremely poorly for hauling bulky payloads, payloads almost have to be designed for the spaceplane, whereas with rockets you just size the rocket and fairing to the payload.

SSTOs (whether rocket or plane) tend to use less fuel if they have a higher TWR because they spend less fuel fighting gravity. There are limits to this, but I'd probably go with a TWR of 1.6 for a Rocket SSTO which is going to be recovered, whereas for non-recovery I'd normally use a TWR of 1.2,

It should be noted if you're an incorrigible cheapskate ALL fuel costs can be eliminated by building an ISRU crawler and launching planes and rockets empty and fueling them up using mined ore (assuming you have ore at shores biome). Also if you're not into cheese but still want to slash launch costs, instead of recovering your launch stage, you can instead reuse it by refueling it in space using ore mined from Minmus. Even better, a Mammoth rocket can quite easily make it to Minmus if you empty out the upper stage tanks or enable crossfeed so it can consume all the fuel, by refueling a Mammoth rocket on the flats of Minmus using a ISRU crawler you save the bother of hauling fuel/ore from Minmus to LKO (also non-Mammoth rockets can make it to Minmus with a little help from SRBs). I tend to believe that this is the optimal way of launching large payloads cheaply to distant destinations (like Moho or Jool), instead of like a 5x Mammoth you just use a single Mammoth and refuel it, because of the greatly reduced fuel costs this probably will be cheaper than recovery on the ground.

Edited February 5, 2018 by blakemw

[Brainlord Mesomorph]

my 0.02 :

If you're honest about how you play the game, and own you occasional crashes, then reusable launch systems aren't really worth the effort.

Let's start with SSTO rockets:

To make an SSTO rocket it has to have enough fuel to take itself all the way to orbit, it'll need a probe core, parachutes, batteries, landing gear etc. all that adds about 20,000 to the cost of the rocket and significantly reduces it's payload capacity. You never get 100% return b/c you'll never land on the runway, so let's assume a 75% recovery rate. Now, if you crash one 1 out of 5 of these rockets (comes down in the mountains, probe core overheats on reentry, renetry is too steep and the chutes rip off, or reentry isn't steep enough and its stuck in orbit.) losing 1 rocket will cost you all the profits you made from recovering the other 4. (and you've screwed up your budget)

OTOH, if you strip that same rocket down to just engine, fuel and fins, and throw it away 20 m/s short of orbit, its way cheaper and it'll carry 30% more payload. You can lift  that 5 SSTO rockets worth of payload on 4 disposables  and it costs basically the same, and you know what your budget is going to be. (and you've saved yourself the game-play boredom of recovering 5 rockets.)

Spaceplanes are both better and worse:

With an SSTO spaceplane you can get to orbit for the cost of fuel (reliable 100% recovery on the runway) using a Spaceplane Sandwich, you can lift truely large payloads to orbit on planes.

But as a launch system, a spaceplane is a much more complex and expensive machine than a rocket. My "C1000  ExoLifter" costs nearly a quarter million. With a sandwich I'm putting a half million spacebucks worth of planes on the runway. If I crash one of those on the way back...

So just trying to build the cheapest disposable rockets is where my research is going. ( the twinboar you say... hmmm)

Edited February 5, 2018 by Brainlord Mesomorph

[Tex_NL]

59 minutes ago, Brainlord Mesomorph said:

You never get 100% return b/c you'll never land on the runway, so let's assume a 75% recovery rate.

Agreed, landing back on the runway/launchpad can be difficult. But stating it will never happen is complete and utter BS ! With a bit of practice and proper design you can land back on the runway/launchpad each and every time.

[Brainlord Mesomorph]

8 minutes ago, Tex_NL said:

Agreed, landing back on the runway/launchpad can be difficult. But stating it will never happen is complete and utter BS ! With a bit of practice and proper design you can land back on the runway/launchpad each and every time.

1.  I was talking about parachuting rockets in from orbit. (and I stand by my statement)

2. bit of an overreaction

 

[Nich]

I have found rather then saving Kredits you are better off making more.  Combining 5 missions into 1 will make way more then the best SSTO space planes could ever save.  Unless you are playing with 10% funds or something crazy.

[magnemoe]

9 minutes ago, Nich said:

I have found rather then saving Kredits you are better off making more.  Combining 5 missions into 1 will make way more then the best SSTO space planes could ever save.  Unless you are playing with 10% funds or something crazy.

This, player time is more important than saving credit outside of rolle playing obviously. 
For common missions especially kerbal transport SSTO makes plenty of sense. 
For large one off missions it would eat lots of time. 
 

[Brainlord Mesomorph]

5 hours ago, blakemw said:

if you're an incorrigible cheapskate ALL fuel costs can be eliminated by building an ISRU crawler and launching planes and rockets empty and fueling them up using mined ore

I suggested that a couple of years ago and someone told me that ore is actually more expensive than refined fuel. So if you want to go that route, just mine huge quantities of ore and then recover it for cash, then buy fuel.

[Alpha 360]

The way I do it is to divide up the rocket with a fully-reusable first stage and a non-reusable 2nd stage. The way I play, I pile on a lot of the delta-v on the first stage, carrying it to about 1,200 m/s and above the atmosphere. Usually if you can do that, then you can detach the first stage, fire up the second stage and reach orbit. Then switch over to the first stage and land and recover that for about 40,000 out of 50,000. So with that I save 40,000 out of a 125,000 credit rocket which can get a lander to Minmus, or in more standard terms, probably about 70 to 80 tons to LKO. So I pay 80,000 credits for 80 tons to LKO or 10,000 credits per ton to LKO. That is barely efficient, but manageable if you run a strict space program. This is of course the first step. 

The next step, for me, probably would be a kerbal transport system which could transport kerbals in large quantities. I would imagine sticking a space-plane onto a reusable rocket stage. Then both the space-plane and first stage would be recoverable, costs ranging from 10,000 to 20,000 from inefficiency of the first stage recovery. I find that this type of set up is a good step up from partially reusable rockets. 

Next would probably be the generic vector and 3.75 meter SSTO. You know, when there is a ring of boosters, ranging from 3 or 4 to 8. Each one being propelled by 9 vectors. This is a very expensive rocket, costing to a quarter of a million or more. But if you have successfully landed the space-plane, then you should be able to land the rocket SSTO with relative ease near to KSC. An SSTO like this could potentially lift up to a couple hundred tons to LKO. This is the ultimate rocket which most players gravitate towards, if they aren't very good with large space plane SSTOs like myself. 

This is mainly my progression of the tech tree. Reusable 1st stages, then reusable rocket space-planes, and finally the vector powered rocket SSTO. 

Happy Explosions!

[Laie]

The best way to reduce launch cost is to reduce payload mass.

19 hours ago, 322997am said:

So I was kinda wondering if VTVL is the best method, or there are better ways to recover rockets/reduce prices

Oh, that's what you're going after... on that premise, winged jets it is. Rockets just cannot compete, period. Of course, actual launch cost is pretty high -- you're rolling out a lot of expensive hardware and any failure is really gonna hurt. It's the recovery that makes it work in the end.

3 hours ago, Brainlord Mesomorph said:

If you're honest about how you play the game, and own you occasional crashes, then reusable launch systems aren't really worth the effort.

Exactly.

3 hours ago, Brainlord Mesomorph said:

You never get 100% return b/c you'll never land on the runway [...] I was talking about parachuting rockets in from orbit. (and I stand by my statement)

Nah, if you have any control at all (a few airbrakes will do), landing on the runway isn't all that difficult.

What poisons recoverable rockets is that they effectively have to be SSTO (because recovering earlier stages is difficult at best, and comes at a steep discount even if you can make it work).

However, one thing to keep in mind... With stock settings, one can totally afford throw-away rockets. Not accounting for recovery in any way is a great way to reduce (actual) launch cost and also takes care of several failure modes. Recovery takes as much time as a launch if not more, and compared to the cash flow the actual mission generates, the payoff for recovering the LV tends to be meager.

[HalcyonSon]

3 hours ago, Tex_NL said:

Agreed, landing back on the runway/launchpad can be difficult. But stating it will never happen is complete and utter BS ! With a bit of practice and proper design you can land back on the runway/launchpad each and every time.

Agreed.  I land 90% of my vertical launch single-stage-to-orbit rockets within 90 km of KSC for a 90% return.  That makes it well worth burning slightly more fuel to carry the probe core and parachutes.  The reentry procedure is identical to any manned pod - place the end of the projected orbit (blue line) in the water east of KSC and reenter engine-first.  

[suicidejunkie]

2 hours ago, Brainlord Mesomorph said:

I suggested that a couple of years ago and someone told me that ore is actually more expensive than refined fuel. So if you want to go that route, just mine huge quantities of ore and then recover it for cash, then buy fuel.

I'm sorry, but that's just flat out nuts.  Did you never do a sanity check on selling dirt vs rocket fuel?

Ore costs 2 spesos per ton.  One ton of monoprop costs 300 spesos.

Launching a convertotron to the runway (it can be powered by the launch clamps!) and then recovering it will earn you over a speso per second, and operates in the background while you're doing other missions.

 

 

I think my spaceplanes average 90-95% recovery or so, with no quicksaves.  In theory it costs 2000 for 5 passengers and a KIS box to Minmus surface or mun orbit, but 10k is Mortimer's minimum bid.

Most common is the minor fees for missing control surfaces and upholstery cleaning after a flat spin recovery, but even in the worst cases of wing-eating disease, the plane can be put down safely on the Minmus or KSC flats using chutes in the cargo bay, so I haven't had any complete mission losses.

 

[Fearless Son]

10 hours ago, blakemw said:

Other than being cheap the Twin-Boar has a host of other recovery benefits. First one is it produces a ludicrous amount of drag in reverse due to the flared base, this means it slows down really well and you never have to worry about overheating during reentry and it'll also typically get down to safe drogue chute speeds without additional drag enhancers, also its fatness acts as a heat shield for the rest of the rocket further reducing heat load on the rocket. Secondly it has a 20m/s impact tolerance so you only need 2 or 3 chutes to safely land it on chutes alone. Thirdly you can drop it in the ocean and its long length and high buoyancy will protect everything higher up the stack (just quickly ninja recover before it tips over). Basically the Twin-Boar comes pretty close to being idiot-proof for recovery and barely any bells and whistles are required for recovery. Again if you're planning on quickloading until you nail the KSC having extra bells and whistles isn't such a big deal because you'll recover the cost, but if you don't want to spend your play time quickloading and just go for a 80%+ recovery for somewhere vaugely near the KSC then it doesn't hurt to keep the rocket on the cheap side.

This combination also makes them ideal first-stage boosters.  You can drop them as soon as they run out, and if you have parachutes on them in the same stage, you can expect them to reliably fall into the ocean on an unpowered descent.  They will be regarded as "debris" by the engine, but you can still recover them for a partial refund of their initial cost.  If one happens to fall apart for whatever reason, no biggy, it was not that pricey anyway.  

[RizzoTheRat]

7 hours ago, Brainlord Mesomorph said:

You never get 100% return b/c you'll never land on the runway, so let's assume a 75% recovery rate. Now, if you crash one 1 out of 5 of these rockets (comes down in the mountains, probe core overheats on reentry, renetry is too steep and the chutes rip off, or reentry isn't steep enough and its stuck in orbit.) losing 1 rocket will cost you all the profits you made from recovering the other 4. (and you've screwed up your budget)

I usually get about 97% recovery, very rare it's below 95%, and that's using chutes and airbrakes with only a short burst of throttle for a soft landing, couild probably do better if I had a bit more fuel (and therefore less payload) to play with on the way down.  I lost a few in development but I class that as simulation and reload.  Now I've got the hang of the entry profile I never lose one of my 45 tonne payload launchers, and as I also use them to recover Hitchiker cans full of crew I don't waste money on re-rentry capsules either.

Never landed on on the runway but I've got close.  I usually intend to land a bit short of the KSC though as that's a lot safer, they won't survive landing in the sea. 

Think it works out at about 550 kredits per tonne which isn't the cheapest, but way less than I can do it with disposables.  Not managed to get a heavier system to work though, everything I've tried so far has too much momentum for the drag and burns it's engines on the way down.

 

 

Edited February 5, 2018 by RizzoTheRat

[Brainlord Mesomorph]

9 minutes ago, RizzoTheRat said:

Never landed on on the runway but I've got close.  I usually intend to land a bit short of the KSC though as that's a lot safer, they won't survive landing in the sea. 

Way back when (in the old aero model) I was fully committed to SSTO rockets, and I got very good at "throwing rocks at the KSC"  - I never tried to control them after the deorbit burn,  just left Isaac Newton in the drivers seat and I could get very close, once almost this close - on the other side of the runway.  

With new areo I can't land in the same place twice - With planes of course, but with ballistic payloads, I'm landing in the mountains, or out at sea, depending on weight drag and how much it tumbles on the way down. But then again I'm not really trying that anymore.

[Brainlord Mesomorph]

39 minutes ago, RizzoTheRat said:

Think it works out at about 550 kredits per tonne

When I did the math I was down to about $600 a ton.

But I was fooling myself about the savings b/c I was comparing recovering SSTO rockets to throwing away SSTO rockets. But when you compare it to stripped down multistage disposables you get like $800 a ton. 

Advice to the OP,  if you want money grind contracts.

[Nich]

There was a disposable cost/ton challenge years ago and the competition started in the 800-1000 range but in the end people managed to get it down to the 450ish range.  One thing I took from the competition was decouplers, nose cones, and control surfaces are really expensive.  SRBs are ok but they are not as cheap as you think.  Twin boars and poodles were high value engines.

[invision]

9 hours ago, Brainlord Mesomorph said:

my 0.02 :

If you're honest about how you play the game, and own you occasional crashes, then reusable launch systems aren't really worth the effort.

Let's start with SSTO rockets:

 You never get 100% return b/c you'll never land on the runway, so let's assume a 75% recovery rate. 

 

 

[RizzoTheRat]

8 hours ago, Brainlord Mesomorph said:

When I did the math I was down to about $600 a ton.

But I was fooling myself about the savings b/c I was comparing recovering SSTO rockets to throwing away SSTO rockets. But when you compare it to stripped down multistage disposables you get like $800 a ton. 

Advice to the OP,  if you want money grind contracts.

Yeah, it's still a reasonable saving over multistage disposables, assuming your 800 kredit figure I'm saving about 12 grand per launch, but it's also giving me a re-rentry vehicle in orbit so I'm not losing capsules/engines/tanks on re-entry vehicles, so my 45 tonne payload is the equivalent of probably 48-50 tonnes of a payload that could re-renter a crew.  However spaceplanes would be cheaper for crew transfers to and from LKO.

One disadvantage of the fixed family of launchers approach that it forces you in to, compared to new build disposables every time, is they're optimised for a particular weight.  I currently have a 16 tonne and a 45 tonne launcher.  If I want to launch a 30 tonne payload I either accept a higher launch cost, or carry 15 tonnes of something else.  I was carrying extra fuel up but now I'm bringing that in from Minmus, essentially for free.

At the end of the day though it's down to how you want to play.  I'm trying to make my space program as reusable as possible, the only parts I've wasted on my last 3 missions (refuelling base and tug on Minmus, 7xSCANSAT launch, and a mission to Ike and Duna for multiple base/flag/science/parts test contracts) have been nosecones, some separators and 4 disposable stabiliser wings.  This has undoubtedly worked out cheaper than disposable launches, but the cost isn't the main driver for doing it.

[Guest]

About spaceplanes and what's being said about them ITT.

I'm currently on a "planes only [almost]" career. Some observations.

1. Developing spaceplanes is a lot of work and I couldn't imagine doing that without quickload/revert to hangar. Until you get them tuned they do tend to crash in all kinds of exciting ways.
2. Once you have one, it's reliable and IMO easier to deal with than rockets. For one thing, getting a good plane into orbit efficiently is -- for me at least -- much easier to do consistently than acing a gravity turn with a rocket.
3. I wouldn't want to do this without Atmosphere Autopilot and its standard fly-by-wire mode. On a keyboard in full stock, planes need continuous control input to fly.
4. Saying that they scale poorly just isn't true. My workhorse early-career rocket spaceplane (based on two or three Skippers) lifted 40-ton payloads with a 4 metre diameter routinely and with no problems. My RAPIER-based late-game heavy lifters can lift 300 ton payloads consisting of three side-by-side 4-metre modules. I haven't needed to lift anything heavier than that; perhaps one of these days I'll see just how high I can go. Saying that they don't scale as much as rockets is true of course; I think a 1000+ ton payload plane would be ... very difficult at least.
5. One thing that planes do uniquely well is recovering modules from orbit. If your objective is to save costs, that helps a lot.

Now I can't compare HTOL spaceplanes to VTOL rockets -- "which is better and why" -- not having ever developed a fully recoverable VTOL rocket lifter. Simple arithmetic would suggest that the VTOL rocket would still be at a cost disadvantage: because of the steeper ascent profile it won't be able to make effective use of jet engines, which means the payload fraction will be much smaller, which means it'll burn much more fuel per launch. Moreover, I am assuming that it's going to be harder to reliably land a VTOL rocket on the runway or launchpad than a plane.

But yeah: Atmosphere Autopilot is crucial to the exercise; before I started using it I was flying them with a joystick and it did work but it's just extremely fiddly and not all that much fun. So if you're talking 100% stock, no mods at all, then sure, avoid planes -- but not because they're inherently more expensive, less efficient, or don't scale, but because the stock controls don't let you fly them as they ought to.

Edited February 6, 2018 by Guest

[blakemw]

22 minutes ago, Brikoleur said:

Saying that they scale poorly just isn't true. My workhorse early-career rocket spaceplane (based on two or three Skippers) lifted 40-ton payloads with a 4 metre diameter routinely and with no problems. My RAPIER-based late-game heavy lifters can lift 300 ton payloads consisting of three side-by-side 4-metre modules. I haven't needed to lift anything heavier than that; perhaps one of these days I'll see just how high I can go. Saying that they don't scale as much as rockets is true of course; I think a 1000+ ton payload plane would be ... very difficult at least.

Spaceplanes scale reasonably well with mass such as carrying more fuel, but they scale terribly with volume (bulky payloads). Basically if the payload doesn't fit within the diameter of a Mk3 cargo hold you're going to have to do extremely awkward things (or use mods, of course, if you use the proper mods there is nothing wrong with spaceplane scaling as it's it not intrinsic it's just the stock game lacks certain parts in larger sizes).

Edited February 6, 2018 by blakemw

[Guest]

9 minutes ago, blakemw said:

Spaceplanes scale reasonably well with mass, but they scale terribly with volume (bulky payloads). Basically if it doesn't fit within the diameter of a Mk3 cargo hold you're going to have to do extremely awkward things (or use mods, of course).

Not true at all. Just use an external payload inside the standard fairings. As I said, I'm routinely lifting 4 m wide modules (2.5 m core with bits poking out), and was long before I even had access to Mk3 parts. All those fuel tanks on the payload are full BTW.

Edited February 6, 2018 by Guest

[blakemw]

I'd probably classify that as awkward: I mean compared with a Triple-Twin-Boar with a 3.75m fairing.

Designing payloads that can be launched by spaceplanes is an interesting challenge but it comes back to what I said in my first post: With spaceplanes you have to design the payload to be launched by the spaceplane, with rockets the payload just has to be able to fit in a 3.75m fairing - or even not. While not usually ideal a rocket is effective at lifting a bulky and draggy payload up and out of the lower-middle atmosphere, simply disregarding all streamlining concerns. This is normally stupid stuff like launching castles, but in any case rockets can do it easily whereas with spaceplanes it would be somewhere between awkward and nearly impossible.

[Guest]

8 minutes ago, blakemw said:

I'd probably classify that as awkward: I mean compared with a Triple-Twin-Boar with a 3.75m fairing.

Suit yourself. I classify it as an elegant solution to a hard problem rather than brute-forcing it with a really big rocket. (You're shifting the goalposts by the way. You claimed that spaceplanes scale terribly to volume. I just demonstrated the contrary, and now you're going "but it's awkward.")

Also, fitting it in a 3.75 m fairing isn't trivial either -- for one thing, you'd end up with a tremendously tall rocket. That poses its own challenges. Making that rocket reusable would be even harder. Making it reusable and so that you can reliably land it at the KSC would be even harder. And even so, it would burn much, much more fuel, and would be harder to get to orbit efficiently and reliably because the gravity turn is trickier than than a plane's ascent profile.

Edited February 6, 2018 by Guest