Looking for a guide/tips to cheap lifters

[Jarin]

Hey, I've been looking about, but haven't been able to find much (this is really it, so far). Pre-career, I used to massively overengineer everything, because why not? But now that I'm trying to be frugal about things, I've become paranoid about just about anything being un-recoverable. Every dropped Skipper is lost funds, y'know?

Assume the lower-half of the tech tree, with what you can get with LKO access and halfway-decent aircraft. Around Mainsail-tech across the board (the 160-300~ish point tech levels)? That's easy enough to get to, I think. Any pointers for building cheap and/or recoverable lifters? I mean, a link to a comprehensive guide covering tips for various payloads and tech levels would be awesome, but I'm keeping my hopes realistic here

Edit: Should probably have put "looking for a" in front of that thread title, so it doesn't look like I'm posting a guide. Can't figure out how to edit the title now though...

Edit2: Thank you capi

Edited October 11, 2014 by Jarin

[Taki117]

If you want recoverable lifters I suggest getting something like Stage Recovery which allows you to put parachutes on your stages and recover them when they despawn for funds. This will help negate the cost of the parts. Another option, if you want to use spaceplanes, is to build in orbit. If you build a spaceplane that can carry X-tons of stuff, and you need an interplanetary ship, just make it out of sections. Another option to consider, is if you already have an interplanetary ship with X-m/s of dV, instead of discarding it either into deep space or the surface of Kerbin, reuse as much of it as you can.

A cost effective space program requires lots of planning to execute because you don't want to use dV unneccessarily. This means waiting for launch windows (Often times to and from) as well as making the most use of things like the Oberth Effect (nor more burning to interplanetary and then trying to intercept your target) Even your ascent profile might need some fine tuning.

[Alshain]

A Taki117 said Stage Recovery or DebRefund for recovering stages.

SSTO's for reusability (this can be a spaceplane OR a rocket, you can single stage a rocket too!)

If you want more reasonable lifters that mirror the real world, use NEAR or FAR and Procedural Fairings. With real aerodynamics you will find yourself rarely using things like asparagus staging.

The Oberth Effect and aerobraking can help reduce fuel requirements.

However the simplest and best thing you can do is use Kerbal Engineer and plan your delta V. Learn how much delta V you need to do what you want to do and add just a little for your piloting skills. Using that image, add all the numbers between your starting position and your goal and that will be the approximate dV you need in your craft for a one way trip (add them backward to get back) and that will also help you plan your stages properly too!

Note: If you do use far, that will reduce atmospheric dV required. Kerbin ascent is around 3600dV, I don't know about the others (Laythe, Duna, and Eve). It won't change Atomsphere-less planets.

One of the big things to be aware of is that it's not just about throwing as much fuel on there as possible, with each bit of fuel you add, your TWR goes down and then you have to add engines too. The idea is to use a single efficient engine, see if you can get as much fuel in it to get the delta V you want, with a TWR of about 1.25 or higher on the launchpad, however you can add boosters to augment it if it's just a little low. If you just can't get the delta V while maintaining a good thrust to weight ratio, that's when you have to add more engines and fuel, but add slowly, don't just pile 10 engines on it.

Edited October 9, 2014 by Alshain

[LethalDose]

I think the first and most important thing to remember is that efficient lifting starts with efficient payloads. Describe the mission profile, and then engineer the smallest payload you can to fit the mission profile. It's been my experience that many players that just over-engineer everything feel like they need to launch MASSIVE payloads, when the mission could be accomplished with a third the mass.

Get a info plugin (MJ, KER, VOID) and learn how much dV it takes to escape the atmosphere (Changes between stock and NEAR/FAR). Use that info to design your lifters.

Keep your TWR low on the pad (values depend on aero model and personal preference).

Until you get more comfortable lifting payloads efficiently, allow yourself to revert and start toying with how little you can use to get a payload to orbit. Also play with your ascent profile.

In my experience, I've had the best luck with LFO cores with strap-on SRBs for cheap lifters. The SRBs are cheap and get the lifter up to speed off the pad while the LFO core sustains the launch, picking up speed slowly as it climbs. I usually get the lifter to around a 75 km Pe and stage at ~ 2 km/s velocity so the lifter re-enters. I use the upper stage engine to complete the orbital insertion (I consider "Upper stages" to be part of the payload). With a single LFO stack and strap-on SRBs at Mainsail tech levels, I can very easily get ~ 40 tonnes to LKO, which is typically all I need for my missions.

You may be able to save more funds if you use a kicker stage to get to orbit, but I don't find them particularly useful.

Asparagus increases your payload fraction, but all the LFO tanks and engines tend to make it very expensive. I haven't done a cost/ton comparison of what I've described above vs asparagus, though.

DasValdez streamed a lifter design lesson recently. Oh here it is.

Hope that helps.

Edited October 9, 2014 by LethalDose

[capi3101]

Edit: Should probably have put "looking for a" in front of that thread title, so it doesn't look like I'm posting a guide. Can't figure out how to edit the title now though...

Just go edit your post, go into advanced mode and you should be able to fix it there. Now I'll see if I can give you some advice on your question, as soon as I read through what everybody else has said...

[capi3101]

Well...okay. Tier 5 tech (at least Tier 5 in 0.24.2; the wiki hasn't been updated yet for new stuff in 0.25). Big chutes, big lander legs, Mainsails, Mk1 Lander Cans...

Hmm. A Mk-1 lander can with sixteen radial chutes, 4 Z-100 batts, 4 big lander legs, a Jumbo-64, an X200-32 and a Mainsail could make Kerbin orbit (4622 m/s delta-V assuming constant seal level Isp with a launch TWR of 2.45), deorbit and land safely at elevations below 5000 meters. Any of the lighter sci instruments attached wouldn't affect the delta-V all that much and the lifter has more than sufficient thrust for the job. You could easily launch an assembly like that, make LKO and return to Kerbin with the whole thing intact. Set your periapsis to 44-45k meters above KSC prior to re-entry, and you can even do a complete return to sender. Whole thing costs a little over 30,000 funds. The trick is flying it - from the get-go the Mainsail provides you waaaay more thrust than you need and it'll only get worse as the ascent progresses. Start by following the terminal velocity curve to 10,000 meters (benchmarks are 100 m/s at 1000 meters, 130 at 3000, 160 at 5000, 210 and 8000 and 260 and 10,000). Make your gravity turn and throttle back as you ascend to keep the craft at the top of the green band of the gee meter. You'll lose too much delta-V to drag if you keep the throttle to the stops the whole way up.

Really, it is a matter of figuring out what you want to do and then how to do it most efficiently. Pretty much what everybody else has said. Alshain's given you good advice; I'd go with it.

[colonel0sanders]

SRBs are cheap. One thing to remember, too, is you can adjust thrust limiter on them as well. If you're launching a smaller ship, you may want to tone down the thrust on the SRBs to get more burn time out of them and to keep you below terminal velocity.

Also, like folks have said, build with your mission in mind. I've got a ship just for rescues that cost less than 10k after recovery (about 11k at launch), and I bet you could do it even cheaper, as my last rescue landed with nearly 800 extra dv.

[Red Iron Crown]

Small payloads and SRBs for as much of the lifting as possible are the keys to an affordable space program. Reusability is good too but usually isn't as feasible for most players until much of the tech tree is unlocked.

[problemecium]

My only advice here (that hasn't already been covered at least) is that the LV-T30 and T45 engines are each able to carry a small payload (e.g. a probe core + sensors) to orbit in a single stage, having maximum dV with about 14 of the starter fuel tank (admittedly this is prone to getting wobbly. Also I recommend turning off the top three or four tanks until the bottom ones run out in order to keep aerodynamic stability).

[Jarin]

Also I recommend turning off the top three or four tanks until the bottom ones run out in order to keep aerodynamic stability).

Random side-note... is it just me, or is making the front tanks drain first in vanilla a kind-of jerk move? <.<

Thanks for the advice, everyone. I'll probably have some follow-up questions when I get home and toy around a bit.

[LethalDose]

Random side-note... is it just me, or is making the front tanks drain first in vanilla a kind-of jerk move? <.<

No, it's not a "jerk move" because it doesn't matter at all in most cases. Most rockets with more than one stage or any kind of a payload remain stable because as the fuel burns out from the bottom of the rocket, the mass at front stays the same and the CoM shifts forward. Most space planes have most of the fuel at or behind the CoM, so the same thing happens: Fuel burns behind the CoM, CoM moves forward.

What ParameciumKid noted above is just an incredibly bizarre case, involving more than a dozen serially stacked tanks... You don't do that normally.

[Jarin]

Most space planes have most of the fuel at or behind the CoM, so the same thing happens: Fuel burns behind the CoM, CoM moves forward.

Because that is a perfectly intelligent and logical way to build aircraft and of course I always do exactly that. I certainly never put my cargo-bay in the middle with fuel tanks in front and back and then constantly madly shuffle to push fuel back into my forward tanks. <.<

...

I'm just gonna go hide somewhere now.

[SRV Ron]

Current hard mode Career cheap contract rocket.

Contract orbiter;

Contract to Mun or Minmus

On its way;

Unlocked tech for the ideal lander;

Just an addition of two more SRBs and a larger third stage tank, parachutes, and this will do the Duna, Ike, and Eve contract. Take advantage of direct intercept and aerobraking to have plenty of fuel left for orbital insertion.

[Friend Bear]

Really short answer but I want to give a tip versus a guide...Makes discovering the possibilities more fun.

...Solid Fuel...

it's the bee's knees.

Most stuff you are doing in career mode is low orbit. If you make up for all costs there, you can spend wildly exploring other planets.

Think shuttle with recoverable gas tank and solids. Do multiple tests in one flight. WaBAM!

[mhoram]

You can also find some inspiration in the Cost-Effective Lifters Challenge.

[Jarin]

Really short answer but I want to give a tip versus a guide...Makes discovering the possibilities more fun.

Just discovered the amazing fun of the new* uber-size SRBs. My god, those are nice. Strap on 2-4 of those and never have to worry about low-altitude "soup" again.

Currently trying to set up a communication network for RT2. So far.... 1 comsat geostationary over KSC. So far so good. Hope I strapped enough antennas to it, though...

*hey, I haven't really played since .23

[-Velocity-]

I created a vertical lift-off SSTO fuel tanker that I launch from the VAB and lands vertically again on Kerbin. It uses RAPIER engines and can take about 30 tons of fuel to orbit. You recover every part of it so you only pay for the cost of the fuel. I did it from the VAB because I just got better fuel efficiency than with any spaceplane design I made through the SPH. The design is halfway between a rocket and a space plane.

So basically, the idea is that you launch only a couple of reusable spacecraft into orbit. A nuclear powered interplanetary transfer craft with multiple docking ports, some kind of generic lander that can land on low gravity bodies up to and including Duna and Moho, perhaps a lander that can land on Tylo, and you have a space plane for Laythe and for transporting your crews and science between Kerbin and orbit.

Anyway, with this approach you end up just paying for the gas to explore the surface of any planet (except Eve, as there is no way to make a stock reusable spacecraft for it), since once you have the hardware in orbit, you are 100% reusable.

[Jarin]

I created a vertical lift-off SSTO fuel tanker that I launch from the VAB and lands vertically again on Kerbin. It uses RAPIER engines and can take about 30 tons of fuel to orbit. You recover every part of it so you only pay for the cost of the fuel. I did it from the VAB because I just got better fuel efficiency than with any spaceplane design I made through the SPH. The design is halfway between a rocket and a space plane.

So basically, the idea is that you launch only a couple of reusable spacecraft into orbit. A nuclear powered interplanetary transfer craft with multiple docking ports, some kind of generic lander that can land on low gravity bodies up to and including Duna and Moho, perhaps a lander that can land on Tylo, and you have a space plane for Laythe and for transporting your crews and science between Kerbin and orbit.

Anyway, with this approach you end up just paying for the gas to explore the surface of any planet (except Eve, as there is no way to make a stock reusable spacecraft for it), since once you have the hardware in orbit, you are 100% reusable.

This would be my ultimate goal. Well, this, with some combination of "refueling at Minmus" via Karbonite or Kethane (still waffling on that one). SSTO is still my bane; maybe I'll have better luck once I get the RAPIER unlocked. What's your ascent profile like?

[-Velocity-]

This would be my ultimate goal. Well, this, with some combination of "refueling at Minmus" via Karbonite or Kethane (still waffling on that one). SSTO is still my bane; maybe I'll have better luck once I get the RAPIER unlocked. What's your ascent profile like?

It's a rocket with wings essentially, so I do get a decent amount of lift. It takes off and lands on landing legs. It has multiple canards on the front and eight delta wings on the back (six of them parallel to provide the primary lifting surfaces). It is powered by 24 RAPIER engines.

Ascent profile: Straight up to about 11000 meters, then pitch down so that a slight climb is maintained. Pitch down will be completed at like 16000 meters. Slowly climb and accelerate, with the goal of hitting about 1400 m/s at like 23000 or 24000 meters. Peak TWR is over 2.5. Eventually, the rocket will autoswitch to closed cycle, but that usually happens due to a thrust asymmetry developing due to the thin air (causing the craft to yaw, further reducing engine air supply and triggering the autoswitch), so you should have an action group to switch to closed cycle when either you're ready, or the moment a thrust asymmetry begins to develop (you'll save a bit on efficiency). Now, you pitch up at like 45 degrees, maybe 50 degrees and burn closed cycle until the apoapsis is above the atmosphere. Once that is done, you just cut off the engines and wait for the circularization burn, which should only be 400 m/s or 500 m/s.

Fuel payload fraction (mass of fuel delivered to orbit/mass of fuel on pad) is around 60%, I believe. I never added it up and checked though. It's a remarkably high number, FAR better than I EVER got from a traditional space plane. The spacecraft can deliver a full Jumbo64 tank to a waiting spacecraft or orbital fuel depot in LKO, while requiring slightly less than that (I think) to put it up there!

The reason I don't know exactly how much it takes is because the RAPIER engines are located on "nacelles" that are fuel tanks themselves. I don't remember how much fuel those nacelle tanks contain total. I suppose the fuel payload fraction may be only 40%.

Edited October 10, 2014 by |Velocity|

[nine_iron]

Ive been doing my test contracts from a plane/spaceplane which I land back at the KSC, very cheap and easy recovery but does take a little more time.

Practically raking in science and also some funds (converting 15% to Sci too).

[Jarin]

It's a rocket with wings essentially, so I do get a decent amount of lift. It takes off and lands on landing legs. It has multiple canards on the front and eight delta wings on the back (six of them parallel to provide the primary lifting surfaces). It is powered by 24 RAPIER engines.

Ascent profile: Straight up to about 11000 meters, then pitch down so that a slight climb is maintained. Pitch down will be completed at like 16000 meters. Slowly climb and accelerate, with the goal of hitting about 1400 m/s at like 23000 or 24000 meters. Peak TWR is over 2.5.

24 rapiers... o.o; what's your engine/intake ratio?

Ive been doing my test contracts from a plane/spaceplane which I land back at the KSC, very cheap and easy recovery but does take a little more time.

Practically raking in science and also some funds (converting 15% to Sci too).

Yeah, I've been running aerial surveys from the extended contracts mod for much of my science. Got myself a nice "sprinter" style aircraft that can cruise 1500m/s at 22km or so which does the job nicely. Still working on getting performance out of one that has a decent cargo bay, though.

I tried sticking wing-mounted SRBs on it to punch it into LKO. This... did not go well.

[-Velocity-]

24 rapiers... o.o; what's your engine/intake ratio?

I think it was like 1.3 or 1.5 intakes per engine, don't remember. Not all intakes are the same, either.