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Building an SSTO with low-tier tech?


pondweed
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Hi all

I'm very interested in SSTO's. something to rescue kerbals with. and general-purpose shuttle to orbit.

I have looked up some videos/posts about building SSTO's, but most seem to be from before Aerodynamics changes patch, or they done in sandbox mode with a load of Rapier engines.

In career mode i'm on quite low end tech, researched tier 3 and parts of tier 4. you recon an SSTO can be built with that sort of tech?

I made a few attempts so far. thefirst issues was the LY-01 (matchstick) landing gears buckling under weight. got me them LY-10's.

current issue now is with jet propulsion: i got the J-33 "wheesley". it doesnt seem to do well up high. will i need the J-404 "panther" ?

 

The payload just needs to be an Mk1-cockpit + remote-control-thingy.

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it sounds like SSTO's in general are barely worth it.

Low tech pre-whiplash/rapier SSTO spaceplanes probably aren't worth it...

But high end SSTO spaceplanes are definitely economical for funds... maybe not player time. Their 4000/3200 Isp offsets the mass penalties easily.

SSTO rockets on the other hand do consume more fuel than a conventional staged rocket, but they still come out ahead in terms of funds.

SSTOs are very practical once you have a working design.

You can put together pretty much any mission you want using only spaceplanes to get payloads to kerbin orbit

 

Just 2 launches ot get this payload into orbit with a spaceplane (a moho mission, where everything can be reused or recovered):

rq1irRl.png

http://i.imgur.com/EZ6XwJt.png

http://i.imgur.com/JiHWstz.png

http://i.imgur.com/FOfPjuO.png

3 launches for this:

Z0fimh5.png

(not including the SSTO laythe lander docked to it)... well.. really only 2, as the lower KR-2L stage is just for ejecting the craft, and it gets refeuled from ISRU at mun (after a retroburn to keep it in kerbin's SOI and aerobraking to lower Ap to Mun orbit)... so its the same launch as the KR-2L part of the first payload.

You can even launch laythe landers for less than 180 funds/ton

http://i.imgur.com/h5QS5sP.png

My version as of 1.1.3 (sans payload)  http://i.imgur.com/BJLhFLs.png

Also note that you can do vertical launch rockets that land like spaceplanes... and you can even stage them using a flyback booster... although the fuel required for the booster retroburn is so great (because the booster needs to get an apoapsis over 70km to enable you to switch back and forth between it and the orbiter as you need to recover both), that its payload fraction is about the same as if it doesnt stage and just SSTOs... still, its cool.

This can SSTO without staging, and thus would count as a panther SSTO, even though the panthers have only a small contribution towards making back ot orbit and are mainly for the booster recovery.

oVu7wmp.png

Booster retroburn after separation: http://i.imgur.com/utRkpeF.png

Orbiter insertion burn + orbiting with payload: http://i.imgur.com/Hfx71vf.png

http://i.imgur.com/e1JK9ul.png

Booster approach and landing: http://i.imgur.com/vaDw4vc.png

http://i.imgur.com/bpWg19y.png

 

I will also note that this surface base was entirely SSTO'd... not just single stage to orbit, but single stage to Mun orbit:

CpZQ8JO.png

The Mun dropship at right was single staged to orbit of kerbin without any airbreathing engines, and without any spaceplane stuff:

1aPSPuF.png

Just mammoths and LFO, and then an infaltable heatshield as an airbrake + chutes for landing... I manages >97% recovery from landing the boosters close enough to KSC. The other modules were brought in a spaceplane... I could have brought them one at a time with a craft like this:

http://i.imgur.com/Fvfy9vY.png   (with a slightly extended cargobay) or this: http://i.imgur.com/akhX6tm.png ,   but I made a spaceplane to take all three modules at once (even though I then ferried them down 1 at a time with the mun dropship and an orbital tug (loading it in orbit was a pain though)

S5fExhB.png

 

Edited by KerikBalm
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The Wheesley can get a very small, light jet to 560 m/s at 10km altitude. But that is really not enough to make a nice SSTO spaceplane. It is definitely possible to make one with a panther and a couple terriers -- I've done it. But it just barely gets you to space, and you have to be very good about keeping your weight and drag down to the bare minimum. Which means they don't fly very nicely on reentry. So while it's doable -- especially as a learning experiment -- I don't think it's nice enough to be practical. So I tend to think that the whiplash engine is the first one that really makes for a fun spaceplane. A whiplash and a couple nuke engines can be the basis of an extremely capable (optimized) spaceplane, or a really pretty and easy-to-fly spaceplane.

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The simplest actually useful SSTO you can build is probably this:

Parachute
Mk1 Pod (monoprop removed)
Decoupler
FL-T800 (or equivalent smaller tanks)
FL-T800 (or equivalent smaller tanks)
Swivel Engine

Needs like... 10 science, I believe, to unlock the minimum required parts. Rolls out of a base level VAB, launches from a base level launchpad, and takes a Kerbal to LKO and back home. Now, if you want to use this to rescue Kerbals for contracts, you'll want some extra parts: an Octo probe core between the parachue and the pod, and some solution to it needing power (either solar panels, or one or more Z-100 batteries - you can attach them to the fuel tanks on the inside of the decoupler). Also, you probably want a bit healthier fuel margins to make the rendezvous, so another FL-T100 or -T200 is in order. Basically whatever you feel is necessary and can be added without dropping the sea level TWR of the Swivel below ca. 1.25.

Now, if you want to build a spaceplane - well basically, you can't. While it may potentially be possible to build something Wheesley- or Juno-powered that barely makes it to orbit, the subsonic airbreathing engines contribute so little speed and altitude that you essentially have not a plane, but an air-launched rocket that needs to haul along a lot of unecessary dry mass. It's going to cost a lot of patience, parts and/or mass (and thus building upgrades) and funds to pull off... and then you're in orbit, and faced with the reality of needing to perform reentry with a craft made out of parts that are not rated for reentry. What are you gonna do, decouple the pod? Then you might as well have sent a much cheaper rocket! :P

No, spaceplanes really start with mk2 fuselage series parts and the Panther engine. Before that, don't bother.

Edited by Streetwind
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So, I've been considering it, and 2 wheesleys plus a reliant may actually be doable -- I'll try it soon and post a note.

 

Edit: Nope, I didn't come particularly close to making orbit. Of course, the LY10 wheels are absolutely necessary. The limited number of MK0 to MK1 adapters, the inability to transfer fuel, and the pathetic heat tolerance of the small circular intake make it unreasonably hard, I think. Plus the 18/30 limits and the width limit create some small difficulty, too.

Edited by bewing
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It's feasable to take a reliant or swivel, stack fuel tanks until you have a TWR of about 0.5, knock it over, prop it up with some wheels, add enough wing to make it flyable and then just abuse your excess of delta V to reach orbit without staging.

I've done something similar with a skipper when testing how much of a craft to give over to air breathing engines. With the tiny Juno, on such a large craft, it's probably not worth adding any air breathers as you'd need so many. With the wheesley you'd have to test to see whether it was worth it.

However you achieve it, without the Panther or better, these are going to be primarily rocket biased craft, using wings to permit excessively low TWR, and for re-entry control.

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Experimenting with making low tier SSTOs is a very good learning method for SSTOs in general. I found this out a while back. Ever since I tried making them my higher tier SSTOs became also a whole lot better, because making low tier SSTOs is basically a hardcore learning lesson that makes you super efficient on the aerodynamics, weight/thrust ratios, and overall building complexity.

So I would advice you to go there since it is possible, and as a result you will be able to build much better higher tier SSTOs.

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jet engines below the panther are basically useless for SSTO planes. you can make a "micro SSTO" with a juno jet engine & spark rocket engine using the 0.625m tanks (or similar) but that thing won't have any payload, so it's just a "toy" for messign around, really. 

I've had some success with rocket planes using the skipper rocket engine. a skipper rocket can get a few tons of payload to LKO in SSTO style, and you can also turn such a rocket into a rocketplane. the main difference is that the rocketplane will use wings for takeoff and landing, so you can stack some more payload onto it (doesn't need a TWR of >1 to take off as a plane) and you don't have that messy "rocket dangling on parachutes" reentry/landing of SSTO rockets.

i suppose you could do similar with swivel engines and 1.25m tanks, but the payload fraction of pure rocket planes is quite low, so you'll probably have to build a bigger plane to get a reasonable load to orbit with a bit of fuel for at least a rendezvous or something.

i think that's the most reasonable route for really low tech SSTO planes. you will definitely have to unlock bigger landing gear and at least the first upgrade of the landing strip (and probably also first upgrade of the hangar).

 

overall, it's not worth it in my experience. even a proper jet/rocket hybrid SSTO is barely worth the extra effort you put it for something as trivial as getting a bunch of kerbals from/to LKO. a simple disposable rocket is only marginally more expensive and it gets to orbit quicker, has more deltaV left for maneuvers and you don't have to worry about a pinpoint landing at KSC when all you bring back is a cheap capsule & some crew cabins - doesn't matter if you recover their full value or only half of it when landin on the opposite side of kerbin.

SSTO's are mostly a roleplay/vanity thing, tbh. don't use them for efficiency. they aren't efficient when you factor in the extra playtime you invest.

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As you increase the difficulty setting on the game, funds get more scarce. At 50% funds, I would definitely like to recover as much as possible of my launch costs. And there are players who set their funds slider to 20% ....

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oh sure, if you set the funds down to 20%, the situation changes. but i don't think 20% is even officially supported. IIRC 60% is the lowest setting, everything beyond that would require editing the save file or something (?). i've played my last career on hard (60% funds) and SSTOs were definitely not worth using.

my rule of thumb was to not spend more than the advance payment of the contract on the rocket. if my design costs more then the advance payment, i know i'm doing something wrong and using an overengineered design. if you follow such a simple rule, the actual completion reward (and usually a part of the advance payment) is your profit. the compeltion reward is usually something like 2-3 times the money you got in advance, so all an SSTO does is increase the margin of profit from 200% to 250% or something, but the additional time you put into the design means the mission takes a lot longer.

for simple missions like "put satellite into orbit", a disposable rocket gets the job done in half the time. doesn't matter that an SSTO would save you 5,000 funds or something, that less than 10% of the money you actually make, so you're better off doing 2 satellite missions with rockets rather than 1 mission with an SSTO.

i actually wanted to make SSTOs useful in that career. i setup a space station to serve as a refuelling spot and hub for toursit missions, with reusable nuclear spaceships and SSTO planes to get people and fuel up to the hub station. it worked, but it was really just a roleplay thing. later i basically abandoned the station and just shot my tourists to the mun or whatever in simple vertical launching rocket powered shuttles.

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Juno & LV-T spaceplanes do work (junos cap a little higher than the turbofans ) but you save little if anything over a atraight rocket. SSTO VTVL rockets are worth investigating if all you're after is recovery percentage. This game I used VTHL spaceplanes early on, but I use the Stagerecovery mod so multistage doesn't really hurt - I just like spaceplanes & recovery to the runway or I'd have left the wings off.

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Panthers work fine, and my panther ssto was the work horse for lko rescues and crew transfers.  Flight characteristics are based on how you design not what tech you have.  Mine was very finicky on re entry until slower speeds.  So I just stay off the stick until moving slower.  Drag is paramount, so I avoid any struts our fuel ducts, and keep wing and stabilizers to a minimum.

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https://kerbalx.com/AeroGav/Icarus

I can do a Tier 4 Spaceplane,  but not an SSTO.

Somewhat fun to fly but a rocket can actually be cheaper.    At this point, I set off to create a highly reusable Tier 4 rocket.   Basically it was configured as capsule, fuel tanks, terrier, decoupler (crossfeed on) , reliant.     Dump the Reliant once you feel you've got enough of a heave on and use the Terrier the rest of the way.  Everything except the Reliant and it's decoupler come back from orbit.

How did it fly?  Let's just say Jeb begged to be transferred back to the Icarus program ASAP.

 

Panther can actually be profitable for tourists that want an orbit, even though this design decouples the panther which is mounted behind the Terrier.

https://kerbalx.com/AeroGav/Hermes-1c

20160520191009_1_zpse8gkjsls.jpg

For nervous passengers,  a complimentary dose of Prozac is stored under each seat.   As you can see, this was a non-revenue flight,  so Tedlorf ended up with all 3 doses.

I kinda like flying this ship, it's fun but safe and makes orbit with a generous delta v margin.   Who cares if its not 100% reusable. 

 

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great stuff chaps, thanks for info.

so it sounds like SSTO's in general are barely worth it. but it still seems fun to try for the novelty factor :)

interesting about the difficulty factors. changing the funds income by 20% seems like a welcome challenge. im sure it will push me to learn more effecient designs and experiement with new ones. 

I don't use auto save/load.  makes for quite the adrenaline rush :o 

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I use SSTO spaceplanes almost exclusively once I have the engines; I use almost-SSTO craft until then, usually just use droppable boost stages fired at edge-of-jet altitude to give a kick to near orbit. Something like this:

27596377425_e955858f2b_b.jpg

Could equally use LV-Ts instead of LV-N and have liquid droptanks.

Recovering everything bar fuel is not to be sneezed at, you just have to have the technology to do it sanely. I don't use really heavy lift ones currently so things like stations go up on rockets, but I try and recover all the rocket boost parts too, even the orbital stage.

Edited by Van Disaster
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Just so long as gametime is not a precious commodity, spaceplanes are a lot of fun and are very economical. It's almost the only thing about the stock game that is near future tech, rather than pathetic 1960's tech.

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3 hours ago, pondweed said:

great stuff chaps, thanks for info.

so it sounds like SSTO's in general are barely worth it. but it still seems fun to try for the novelty factor :)

 

Kinda depends what you mean by an SSTO

If you mean a single stage spaceplane that you fly back to a landing then I'd agree. 

If, though, we include a wingless single stage rocket that you land with some chutes then they can be very useful early in the game.   

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10 hours ago, pondweed said:

so it sounds like SSTO's in general are barely worth it. but it still seems fun to try for the novelty factor :)

Basically, yeah.  You probably save a lot of funds since you can recover the entire craft(assuming you can land it safely on the runway to get the full 100%value back), but even that savings is probably at least somewhat offset by the fact that you'll be using a lot more fuel to put a payload into orbit that way instead of using a conventional rocket.  And by the time you have the tech to build a spaceplane, funds probably aren't much of an issue anyway.  They also take a lot more gameplay time for a particular mission, mostly on launch and deorbiting/landing it which may not be especially fun after the first few times.

So yeah, they're probably mostly good for novelty or if you're trying to roleplay a somewhat more realistic space program where you don't have virtually unlimited funds and you actually want to be efficient about costs.

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Er, if you're using more fuel in a spaceplane than a rocket then something is amiss... but thy definitely take considerably more gametime to recover. Slightly mitigated by most of the recovery being mostly hands-off, but still a fairly long process. I like doing it though or I'd not have been building the things so long that I can't build a decent rocket, but I can build to let the craft re-enter mostly unatended by now.

Also, if you don't feel up to runway landings ( especially more rough versions ) just land on the grass or even in the sea & taxi the last bit.

Edited by Van Disaster
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27321416482_a59c98ff2e_b.jpg
27385783446_ff3d08088c_b.jpg

That was my early tier solution - I could have actually flown the boosters back myself if FMRS worked, but I didn't fancy that every launch so I just let StageRecovery grab them. Note tiny Juno pods, plenty for recovering the spaceplane. Why the spaceplane? well I didn't have much luck recovering passenger cabins vertically & I knew for sure I could build a spaceplane, so why not.

26809165363_0dc426604b_b.jpg
26761687483_d864414668_b.jpg

That sort of thing was fun, worked, but rather impractical :P none of these things are SSTO, but all parts are eminently recoverable somehow ( well the boost stage on the carrier launched part is only really parachute recoverable, but that bit wasn't costly ).

Edited by Van Disaster
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