Are SSTO's worth it?

[Acestin]

Hello. I am not new to the game at all (800+ hours), but I have never ever tried my hand at SSTO's (that's kind of a lie, I made a super simple one before the 1.0 update). I was just curious if SSTO's are even worth trying to make in KSP. If they are useful but only in certain situations, what are those situations?

 

Edit: I'm using a stage recovery mod, as well as a off-world construction mod, so this will/may dictate my reasons for or against SSTO planes. Also, by worth I mean their cost effectiveness and overall performance.

Edited November 7, 2018 by Acestin
To clear up confusion.

[ZL647]

They can be quite fun and challenging to design. Then you get to have that good feeling when you succeed. Beyond that, their main use is career mode to save yourself some $$ since you'll get quite a bit back for recovering them, so they make good contract farmers. Or if you just happen to like them.

Beyond that, they don't serve any purpose that a conventional rocket can't also serve, and they require some design choices that definitely place restrictions on their capability.

However, being as this is a game, and I enjoy them, I still find myself making lots of SSTO space planes XD

Edited November 7, 2018 by ZL647

[Chel]

SSTOs are great for Career mode as the more parts you recover the more you save. Why send a 3 stage rocket to deploy a satellite around Kerbin if you are only going to lose money and not recover the parts? With an SSTO you can deploy the satellite and come back down, recovering all parts and making a tidy profit out of it. Not to mention SSTOs look very cool and hi-tech

[overkill13]

I built a couple lower tech SSTO's with Panther engines and had some fun for a bit.  They definitely save some money, but frankly not enough to be worth while.  I've recently subscribed to Snark's opinion that in the time it takes me to launch and recover an SSTO space plane I could have already launched another mission and made more than enough money to cover the loss of some boosters for both rockets. SSTOs require flight all the way up and down, careful reentry planning and time warp often isn't an option without attracting the kraken.  I had issues with some MkII bodies and the trajectories mod.

Definitely a nice accomplishment, but my play time is better used launching rockets.

[Geonovast]

Before going any further... SSTO does not explicitely mean reusable space place.  It's simply Single Stage To Orbit.  I build expendable rockets all the time that are SSTOs, because they don't stage anything off before achieving orbit.  What happens after orbit is irrelevant as far as SSTO status is concerned.

SSTO returnable space planes however, are their own thing.  They may not be practical in most places, but they sure are a challenge to learn to build and really fun to use.  The bulk of my KSP time nowadays is spent flying reusable shuttles, like the real one.  Practical for the game?  Not at all.  But a blast to launch, dock, and fly back to the KSC.  Plus they look cool.

SSTO planes are the same.  I'm terrible at them, I can't get squat as far as cargo up with one, but I did manage to build one that's a good small crew ferry for a space station.  Were I in career, I could run kerbals or small supply payloads up to my space station for the cost of fuel.

[I_Killed_Jeb]

I think most of the min/max math has shown that SSTO's, esp. spaceplanes, aren't fund-efficient because in the time it takes for you to carefully land back at or near KSC, you can easily perform another contract or two.

 

That being said, they're certainly very fun! The first plane is a challenge, but subsequent designs can be based off the first one (just multiply payload, fuel, intakes and wing surface by the same factor) before tweaking.

[Chel]

1 minute ago, I_Killed_Jeb said:

I think most of the min/max math has shown that SSTO's, esp. spaceplanes, aren't fund-efficient because in the time it takes for you to carefully land back at or near KSC, you can easily perform another contract or two.

 

That being said, they're certainly very fun! The first plane is a challenge, but subsequent designs can be based off the first one (just multiply payload, fuel, intakes and wing surface by the same factor) before tweaking.

If you practice using SSTOs then you should have little issue getting back to the KSC, and as you've said they are fun to build and fly

[I_Killed_Jeb]

4 minutes ago, The_Cat_In_Space said:

If you practice using SSTOs then you should have little issue getting back to the KSC, and as you've said they are fun to build and fly 

I agree it's not so much a giant challenge, but unless you're a superpro flying through physics warp, it's still going to take a number of minutes even under the best of circumstances

[Hydrothermalventclam]

I am not great at SSTOs, though I have built a few SSTO spaceplanes.  I find that they can make very routine missions, like a crew transfer to a LKO space station, much more interesting and fun.  I have never had much difficulty returning them to the KSC, you just need to figure out the decent trajectory that works and stick to it.  I always plan my missions such that there is a little fuel left in the tanks to fly the plane back to the runway if I overshoot or undershoot a bit.

As to your question, it totally depends what you mean by "worth it".  I would recommend designing one, flying a mission with it, and seeing if you like it, because that's all that matters in the end.

[KerikBalm]

What is it?

Funds? you can definitely save funds with them.

Your time? If you have fun and enjoy it, then yes. If you'd rather launch disintegrating totem-poles, then they're not worth it.

IMO, just about anything you can launch with a rocket, you can launch with a spaceplane, however, spaceplane part count may be higher.... and for obscenely large payloads (greater than 10 meter diameter/greater than what a 3.75meter fairing can expand to enclose), it gets quite difficult to get a working design off the runway.

[Guest]

I love them.

"Worth it" is entirely subjective however. 

From a sheer efficiency point of view, they rule. Once you have access to RAPIERs, there's simply no more efficient way to loft a cargo to orbit than a spaceplane, in terms of consumables used per ton lofted: airbreathers are just that efficient, and because you can return spaceplanes precisely to the runway, they're 100% recoverable.

Earlier in your career, you can make 100% recoverable rocket-powered ballistically launched, horizontally landed craft: you fly them up like a rocket, then glide down and recover them like a plane. I have found this to be the best way to create fully recoverable rocket lifters: you could leave out the wings and land with parachutes and/or retro rockets instead, but that's harder to do precisely enough for a 100% recovery. These are also easier to design than HTOL spaceplanes, because the payload goes on the nose like on a rocket and it's perfectly fine -- desirable even -- to have the centre of mass far forward on the way up. And /very/ early in your career, you can get to near 100% recoverability even without landing gear, because you can ditch them in the sea in front of KSC. 

Later in your career, you can use them to explore Laythe and Duna. (For Duna though you'll probably want something even more complicated -- a VTOL or STOL SSTO. Although it only has to be SSTO for Duna, which is easier than SSTO for Kerbin.)

On the other hand, SSTO spaceplanes are much harder to design than ballistically launched rockets or conventional landers, and it's even harder to design spaceplanes that can loft bulky payloads; it's often easier to design your payload to fit the plane rather than the other way around. It can be done -- I have made spaceplanes lofting 10-metre wide, 100-ton plus payloads -- but it requires a lot of work, troubleshooting, and fine-tuning to get them working reliably. However for me at least that's the entire point of playing KSP -- finding hard design challenges and then overcoming them.

[Atkara]

I use SSTO spaceplanes in LKO mostly, for a variety of tasks:

• Carry crews and passengers to/from stations and vessels.
• Carry equipment to and from LKO, including recovered parts from rescue missions.
• Carry fuel/ore to LKO to be picked up and distributed by drones.

Given the extent of the career they operate in, I fly them frequently and thus, I know my planes. Landing is always something to be careful at, but a less than 5 m/s descent rate on touchdown ensures you won't break the craft -make it less than 3 m/s to ensure you won't bounce off the tarmac.

Is it worth it? Well, it's harder than launching rockets, I can tell you that. But once you get right and as you accumulate flight hours, you become better (like all things we practice on) and in the end, yeah, it becomes more than worth it.

Should you get into that kind of action? I suppose it depends on what do you want to accomplish in the game, but in the end, only you can answer that.

[Kroslev Kerman]

it depends if your playing for fun i think its no if your playing career just make SSTO rockets(so much easyier to build and fly)

[Acestin]

3 hours ago, Hydrothermalventclam said:

I am not great at SSTOs, though I have built a few SSTO spaceplanes.  I find that they can make very routine missions, like a crew transfer to a LKO space station, much more interesting and fun.  I have never had much difficulty returning them to the KSC, you just need to figure out the decent trajectory that works and stick to it.  I always plan my missions such that there is a little fuel left in the tanks to fly the plane back to the runway if I overshoot or undershoot a bit.

As to your question, it totally depends what you mean by "worth it".  I would recommend designing one, flying a mission with it, and seeing if you like it, because that's all that matters in the end.

Yeah, I should have better defined "worth". By worth I mean cost effectiveness and time. I have built a SSTO plane in sandbox and I really did like it. However, I feel like instead of a SSTO plane, I should design a SSTO rocket (I have a stage recovery mod) that has some sort of plane on top, like the dynasoar.

[Pecan]

SSTO: Single Stage To Orbit (as has been said) but I'm willing to add 'reusable' as the only potential benefit.
Cost Effective:  At any planet/moon you intend to revisit it's a good idea to have one or more dedicated landers that simple shuttle between the ground and local orbit.  It is absolutely worth it to make them reusable.
Spaceflight: No, SSTOs are terrible at that.  Landers are best dedicated to the task of launch and landing, especially if through an atmosphere.  Quite simply, atmospheric flight needs too many massy aerodynamic considerations that you don't need in space.  In addition to dedicated landers have dedicated space tugs/stations without so much as a landing leg.  (Whether stations are 'worth it' is an entirely different thread ^^)
Fuel-to-space: Cheaper to mine it on Minmus, costs almost nothing to launch and transfer using dedicated, reusable, landers and tugs.
Construction-to-space: Your ships all have to start on Kerbin.  It is worth it to launch them using reusable SSTOs, especially if you build your largest vehicles in space, by docking easily-launched modules together.  Modularity is good and this helps keep your cargo SSTOs smaller and easier.
Crew-to-space: Your ONLY source of Kerbals is Kerbin.  No. 1 reason for a Kerbin SSTO is to give them a ride to the nearest spacestation.  And tourists, of course.

Edited November 7, 2018 by Pecan

[Cavscout74]

The primary places I use SSTO spaceplanes are for Laythe interface & for LKO crew transfers.

For Laythe, it just made sense - either use built-in ISRU or refuel from a ground base, and so long as I don't botch a take-off or landing, I just have a single vessel permanently based around Laythe for interface duty.   In fact, I've never used a vertical crew lander on Laythe.  I started off with a few downloaded designs, then reverse engineered & modified designs I liked, and most recently made an original design that works well.

For a while, that was just about all I used them for.  One factor that I've added to my careers that encourages spaceplanes is time limits between rocket launches based on launch mass (<18t requires 1 day, 18-140t requires 10 days & >140t requires 20 days between launches), but spaceplanes are exempt from that restriction.  So now most of my larger stuff gets launched on expendable rockets, then the crews go up & down on spaceplanes.  Late career, it's pretty common now to find half a dozen spaceplanes in parking orbits waiting for my various interplanetary crew cyclers to return home, plus one or two more on various missions in LKO or between Mun or Minmus.

For a while, I was also using a recoverable rocket, but it started getting tedious manually landing a fleet of rockets back at KSC after every interplanetary launch window.  I still use that design occasionally, but it just wasn't worth the time to me.  If I was using a stage recovery mod, it probably would've been worth the effort.

[Tyko]

My least favorite time sink in the game is getting into orbit around Kerbin and returning from orbit to Kerbin's surface. I love flying in space - maneuvers, rendezvous and docking, building on orbit stations, etc. For me the initial launch and return is just something to be accomplished as quickly as possible to give me more time doing what I enjoy. Because of this I stick to launching rockets and recovering pods because it's quick. 

Everywhere else I aim for re-usability. I build SSTO landers, I use space tugs and ISRU whenever possible - partially because this means I have to launch less from Kerbin   

That said, I love the amazing space planes others build. I really admire the work that goes into them and how cool they look. If I was just building them to look at them I'd probably spend more time on them.

[Acestin]

3 hours ago, Pecan said:

SSTO: Single Stage To Orbit (as has been said) but I'm willing to add 'reusable' as the only potential benefit.
Cost Effective:  At any planet/moon you intend to revisit it's a good idea to have one or more dedicated landers that simple shuttle between the ground and local orbit.  It is absolutely worth it to make them reusable.
Spaceflight: No, SSTOs are terrible at that.  Landers are best dedicated to the task of launch and landing, especially if through an atmosphere.  Quite simply, atmospheric flight needs too many massy aerodynamic considerations that you don't need in space.  In addition to dedicated landers have dedicated space tugs/stations without so much as a landing leg.  (Whether stations are 'worth it' is an entirely different thread ^^)
Fuel-to-space: Cheaper to mine it on Minmus, costs almost nothing to launch and transfer using dedicated, reusable, landers and tugs.
Construction-to-space: Your ships all have to start on Kerbin.  It is worth it to launch them using reusable SSTOs, especially if you build your largest vehicles in space, by docking easily-launched modules together.  Modularity is good and this helps keep your cargo SSTOs smaller and easier.
Crew-to-space: Your ONLY source of Kerbals is Kerbin.  No. 1 reason for a Kerbin SSTO is to give them a ride to the nearest spacestation.  And tourists, of course.

So what I'm gathering is that SSTO airplanes have a special niche that even then can still be done with a rocket?

 

3 hours ago, Cavscout74 said:

The primary places I use SSTO spaceplanes are for Laythe interface & for LKO crew transfers.

For Laythe, it just made sense - either use built-in ISRU or refuel from a ground base, and so long as I don't botch a take-off or landing, I just have a single vessel permanently based around Laythe for interface duty.   In fact, I've never used a vertical crew lander on Laythe.  I started off with a few downloaded designs, then reverse engineered & modified designs I liked, and most recently made an original design that works well.

For a while, that was just about all I used them for.  One factor that I've added to my careers that encourages spaceplanes is time limits between rocket launches based on launch mass (<18t requires 1 day, 18-140t requires 10 days & >140t requires 20 days between launches), but spaceplanes are exempt from that restriction.  So now most of my larger stuff gets launched on expendable rockets, then the crews go up & down on spaceplanes.  Late career, it's pretty common now to find half a dozen spaceplanes in parking orbits waiting for my various interplanetary crew cyclers to return home, plus one or two more on various missions in LKO or between Mun or Minmus.

For a while, I was also using a recoverable rocket, but it started getting tedious manually landing a fleet of rockets back at KSC after every interplanetary launch window.  I still use that design occasionally, but it just wasn't worth the time to me.  If I was using a stage recovery mod, it probably would've been worth the effort.

StageRecovery is a good mod I use. It's not like cheaty either. Once a dropped stage (even just a single part) is below like a certain altitude, the mod calculates where it would land on Kerbin and then, if you have enough parachutes or enough Delta-V to slow the craft down to landing speed, it will recover it and refund. I made an SSTO rocket that could deorbit itself and I just have to project its trajectory to about around where the KSC will be once the mod takes over. Not a great system but I get anywhere 85%-95% refund. The powered landings are also only possible if you have a Kerbin somehow piloting the craft or a probe core, and the parachute method still has a chance of failing. 

[Pecan]

1 hour ago, Acestin said:

So what I'm gathering is that SSTO airplanes have a special niche that even then can still be done with a rocket?

Sort of.  What I meant was that a reusable launch/lander is always a good idea whichever planet/moon you're talking about.  (Space)plane really just means it's intended for atmospheric flight.  As such, you shouldn't design it for lunar/interplanetary flight as well - unless that's what you wanted in the first place, in which case it isn't a SSTO anymore, in any meaningful sense.  Note that the efficiency of jets is only relevant to Kerbin and Laythe, where they totally make sense.

Everything can be done with a disposable rocket.  Much better can be done by launching indefinitely-reusable transfer (space) vehicles that shuttle between the planets/moons carrying <whatever>.  At each end you have similar, infinitely-reusable, "landers" that just do the ascent/descent bit.  Any trip from anywhere to anywhere 'should', in this scheme, be - launch vehicle => transfer vehicle => lander.  Since "launch vehicle" and "lander" are meant to be the same, infinitely re-usable, thing (dedicated to locality - no point in an Eve ascent vehicle at Gilly!) that becomes SSTO => Infinite-Spacecraft => SSTO, although apart from Kerbin and Laythe the SSTOs would almost certainly not be spaceplanes (where their great benefit is jets).  For a planet/moon that has an atmosphere but does not provide the oxygen for jets a 'straight' SSTO-rocket-with-parachutes is likely to be more efficient (*depends on a where/mass/design/flight*) and is almost always a lot quicker and easier.

That's may be alright for the vehicles themselves but what about the fuel and crews they need?  Well, as I said before, the fuel can come from Minmus or elsewhere at no cost at all, once you've sent a mining unit there.  You use free electricity to mine it, so it's free apart fom time.  Launch from Minmus back to Kerbin (if that's where you want your 'fuel dump') requires 1,430m/s dV, or less.  That's almost 2km/s less than launching from Kerbin itself, where you would have to pay for that fuel plus the (admittedly inconsequential) launch-fuel.

Crew are different and, for me, a source of fun.  Yeahh!  Instead of those mining drones and hibernating-transfer-vehicles it's a chance to spend a little effort transporting your most valuable resource in style and comfort.  Orient Express to everywhere ^^.

Edited November 8, 2018 by Pecan

[Atkara]

I could've easily derailed the thread, when Pecan's mention of Minmus picked my curiosity. Choosing to wait for once, it turns out that he was talking about the simple case of bringing fuel back to LKO, instead of what I had in mind.

Anyway, I don't think you can talk about SSTO planes without having their uses in mind (unless you make them just to look at them, like Tyko said earlier) and their quirks. And while it can be argued that further details maybe better to be left for later (or another thread entirely) I believe certain things have to be said, so that you won't break your plane on the way out and/or back.

[Acestin]

From what I gather, is that SSTO aircraft are good for specific jobs that a rocket would not be too good in, such as atmospheric flights off Kerbin or crew transfer between low-orbit and a planet with atmosphere.

Other than those reasons, building SSTOs is more or less a pass time (which is fine)?

[Geonovast]

29 minutes ago, Acestin said:

(which is fine)?

Well, literally everything you do in this game is fine.  If you want to spend your entire day walking a kerbal around the KSC pretending to tend gardens, then go nuts!  It's your game.

I really think SSTO spaceplaces are popular for the cool factor.  Which they are.  SSTO reusable rockets are pretty cool too, especially when you manage to land them back on the launchpad.

As for the Laythe example, they definitely do have an advantage over a rocket a reusable SSTO rocket.  Laythe is almost all water, and bringing a rocket down precisely to get on land all the time on Laythe would be incredibly tedious.

[Pecan]

13 hours ago, Acestin said:

From what I gather, is that SSTO aircraft are good for specific jobs that a rocket would not be too good in, such as atmospheric flights off Kerbin or crew transfer between low-orbit and a planet with atmosphere.

Other than those reasons, building SSTOs is more or less a pass time (which is fine)?

Yep, pretty accurate summary, I'd say - including the "just because you want to" reason being fine :-)

18 hours ago, Atkara said:

I could've easily derailed the thread, when Pecan's mention of Minmus picked my curiosity. Choosing to wait for once, it turns out that he was talking about the simple case of bringing fuel back to LKO, instead of what I had in mind.

 

What. what?  Now you've got me curious  (Fuel to LKO was only an example that got an "if that's ...")

[Atkara]

8 hours ago, Pecan said:

What. what?  Now you've got me curious  (Fuel to LKO was only an example that got an "if that's ...")

Yeah. At some point I thought of using Minmus itself as a 'fuel dump' of sorts -basically fueling up interplanetary vessels in orbit around Minmus before sending them out. Problem is that ejecting so far out of Kerbin, means you're doing it without all the energy you'd otherwise have from it's gravity well.

But what if you came back down for a close "fly-by" (technically, you haven't left the system yet) got back all that energy (plus the amount you converted to potential energy by going to Minmus in the first place) and performed the ejection burn down there? In theory, you'd have exchanged 150-170 dV for the comfort of performing fueling operations in Minmus' low gravity conditions, while saving ~800 of your vessel's total dV budget (since you're coming down from Minmus fully fueled).

Haven't tried it myself yet, but I understand it makes calculating transfer windows more complicated than usual and frankly, I don't know if it really works as well as I think it does. So, seeing you mentioning Minmus, my mind went straight there and I was one step from asking how well it works for you. Then I said to myself "he propably doesn't mean anything of the sort" so, I waited

Edited November 9, 2018 by Atkara

[magnemoe]

3 hours ago, Atkara said:

Yeah. At some point I thought of using Minmus itself as a 'fuel dump' of sorts -basically fueling up interplanetary vessels in orbit around Minmus before sending them out. Problem is that ejecting so far out of Kerbin, means you're doing it without all the energy you'd otherwise have from it's gravity well.

But what if you came back down for a close "fly-by" (technically, you haven't left the system yet) got back all that energy (plus the amount you converted to potential energy by going to Minmus in the first place) and performed the ejection burn down there? In theory, you'd have exchanged 150-170 dV for the comfort of performing fueling operations in Minmus' low gravity conditions, while saving ~800 of your vessel's total dV budget (since you're coming down from Minmus fully fueled).

Haven't tried it myself yet, but I understand it makes calculating transfer windows more complicated than usual and frankly, I don't know if it really works as well as I think it does. So, seeing you mentioning Minmus, my mind went straight there and I was one step from asking how well it works for you. Then I said to myself "he propably doesn't mean anything of the sort" so, I waited

Duna speed run after drop from minus orbit. 

You can aslo do an return burn directly from Minmus orbit like an standard return from moon burn.
Put an probe in low kerbin orbit and plot trajectory on it, you ship need to copy this burn but with 900 m/s less dv required, very nice then you are throwing huge bases outward. 

For an energy efficient run to Duna you don't need an booster as the dV requirements for landing on Ike is higher than the transfer