Acestin

Are SSTO's worth it?

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I think, In ksp, pure rocket (reusable) sstos are much useful than spaceplanes. Most of my career launches are done via 1 over massive bfr/ish ssto stage.

Rocket sstos are most often way larger, but are way simpler to design.

In my opinion, spaceplanes are most useful for shuttling large numbers of kerbals between ksc and stations. 

Spaceplanes are mostly a mark for your skill, rather than being actually practical.

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Once upon a time in one of my many career saves I needed to deliver repeated payloads weighing up to 70 tons to LKO, and so I designed a fully stock reusable booster and go full spaceX. The single core could lift 30 tons, but to lift the 70 required I needed to go falcon heavy style. I could actually recover all three boosters using SMRS (I think that’s what it’s called? It’s the mod that lets you go back to stage separation to land boosters and benefit) 2 landed back at KSC, one landed one a drone ship using some assistance from a kOS script. The second stage could *kinda* be recovered. It worked!

But the whole thing about *repeated* launches got kind of tedious. Well, really tedious. One launch took 20 min just to get to LKO in order to properly land each of the boosters. 

Then I devised a SSTO to do the job. I gave it huge wings and plenty of rapiers located near the COM so it was actually really well balanced. It could lift 75 tons to orbit EASY! And the whole mission only took about 6 minutes. The only downside was space. I really had to cram some stuff in the MK3 cargo bay in order to get to orbit whereas with the heavy rocket everything was enclosed in a fairing. 

Oh, and the SSTO had much better returns too, less fuel was burned and the recovered rate was 100% if I landed it on the runway whereas the rocket would have 2 land on the grass and one on a ship very far out. 

(I’ll try to remember to add pics to this post when I get to my pc so you guys see my designs.)

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I have designed a few SSTOs, mostly just for the fun of it.  Probably the only use I've personally found for them is for putting small satellites in to LKO (before the satellite puts itself in to a higher orbit) or for transferring crew to and from space stations.

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SSTOs come in two flavors...  

Single Stage to Orbit space planes and Single Stage to Orbit rockets.   

I used to only build planes.. but now that I have discovered the speed and new challenges of launching SSTO rockets it has become a new game for me.

Where as before it could take upwards of 10-15min to get a plane into orbit and deploy the cargo... now I can do it half the time, and have a fairly easy to fly craft.  With many more landing options.   I am sure I can even modify the base design and use it as a lander on Duna or most other planets except Eve.    

I love the SSTO designs they often are far easier to use.  

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On 11/8/2018 at 2:56 PM, 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)?

Pretty much that yeah. 

I think it's fairly uncontroversial to state that SSTO aircraft rule for 

- exploring Laythe

- lofting modestly-sized, compact cargoes (or Kerbals) off Kerbin

Anything more ambitious than that is squarely in the "because you want to" category. Which isn't to say that they can't be good -- again, I have made high-mass, high-volume SSTO lifters and they work great -- but they are a lot of work, and require a lot of fine-tuning to get right. Rockets are unquestionably easier, even recoverable SSTO rockets.

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Lots of content has been removed from this thread.

Somebody (who's been around long enough to know better) objected to people giving helpful, detailed answers to the OP's question, which of course people objected to, and then the thread got massively derailed by people who were,

  1. bickering, and
  2. bickering about bickering

C'mon, folks.  I know you know better than this.  We're all pals here, and when somebody asks a question, people are going to answer it.  It's what the forum is for.  I can't believe I actually have to explain all this, but apparently a refresher is in order:

  • If someone asks a question?  Feel free to answer it!  :)
  • If you're not interested in someone else's response?  Feel free not to read it.
  • It's not your place to tell anyone else how to post or how not to post.  You're not a moderator, so please don't try to act like one.  Trying to boss people around like this is called "backseat moderating", and is against the forum rules (specifically, 3.2).
  • If you see someone posting something that you believe is so egregious that it violates forum rules, please just report the post so the moderator team can have a look.  Do not attempt to enforce it yourself.
  • On-topic posts (e.g. for this thread:  discussing the merits of spaceplanes and/or SSTOs) are fine.
  • Off-topic arguing (including arguing about arguing) is not.
  • If you see a flame war, report it-- or, at least, just walk away.  Don't stand around pouring more gasoline on the fire.

I'm going to give you all the benefit of the doubt and assume that you're just having a bad morning or haven't had your coffee yet, or something.  So nobody's getting dinged... yet.

But please, I trust we can play nice, now?  Thanks.

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Whether a spaceplane is "worth it" or not depends on what "it" is, on what you want to do.

One example of a thing spaceplanes are good at (to add to the examples already mentioned) is doing around-Kerbin contracts (again, if those are something you want to do.)  Things like "Take X reading at Y altitude over position Z on Kerbin" can be more or less difficult to do depending on distance from KSC and altitude.  For example, something above 20 KM on the far side of Kerbin would be difficult to do with low-thrust, low-altitude engines, and flying all the way around Kerbin in a plane can be a bit of a chore since you have to shepherd the plane the whole time; trying to send a rocket through there can be imprecise and might expend more funds than you are comfortable with for that contract.  But a spaceplane can do a big trans-atmospheric ballistic flight that will save you time and give you the opportunity to correct and loiter long enough to take your readings before coming in to a soft landing and a strong fund recovery.

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11 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...

There is a current thread on exactly that in the gameplay questions area:

Although I've used it I prefer the 'Kerbin Spacestation' approach - where a station acts as hub and interchange so everything in or out goes via there.  The station's invariably above Kerbin itself because taking craft and crews from Kerbin to Minmus is far more effort/time/dV than fuel to Kerbin.  Then again, I'm pretty sure it's been shown that stations aren't "worth it" - I just like to RP that way.

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4 hours ago, Hodo said:

I used to only build planes...

Hodo is being almost criminally modest here!  It would almost be fraudulent not to say that Hodo was (if not still is, we'll have to tempt him out of his shyness) one of the best advocates of the 'art' of spaceplanes, in every sense.  *Tips hat*

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On 11/6/2018 at 10:53 PM, overkill13 said:

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.

This is why I've grown to love SSTO tailsitters. You keep your launch costs down (Im down to around 650f/t) without spending crazy amounts of time trying to stick runway landings. The lifter below is good for 50t to a LKO rendezvous, then with a well timed retro burn lands close to KSC. No need to spend hours landing, I just get close and pop the chutes. Heres some pwetty pics:


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2 hours ago, Pecan said:

Hodo is being almost criminally modest here!  It would almost be fraudulent not to say that Hodo was (if not still is, we'll have to tempt him out of his shyness) one of the best advocates of the 'art' of spaceplanes, in every sense.  *Tips hat*

Thank you for the kind words.  

It is true, I am a bit SSTO plane crazy.  I managed to build, test, and use one of the biggest FAR+DRE SSTO space planes ever used.  And it was actually easy to fly.      I have yet to try and build anything like that again... now I am going a bit smaller.   

 

Next goal is to get my tail landing rocket designs working and see if I can do a completely recoverable SSTO tail landing rocket without the assist of parachutes.   Planes are easy... to me.

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On 11/10/2018 at 7:04 AM, Pthigrivi said:

The lifter below is good for 50t to a LKO rendezvous

This one is very appealing.  (By the way, how much fuel do you have onboard at lift-off?)

Edited by Hotel26
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Thanks, @Hotel26! It's been my workhorse for ages in this save. It starts full at around 18400/22500 LF/O. Helps to have access to 5m tanks to keep it squat, especially if you overshoot and have to ditch into the ocean. Glides nicely though if you pin the fore and aft tanks and move the landing fuel back and forth to control the pitch. 

Edited by Pthigrivi
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I like the idea of SSTO spaceplanes, but I rarely use them because I'm frequently playing in 2.5x scale.  It's a bit harder to cram in the extra delta V and still have a useful payload.

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On 11/12/2018 at 11:22 PM, Norcalplanner said:

I like the idea of SSTO spaceplanes, but I rarely use them because I'm frequently playing in 2.5x scale.  It's a bit harder to cram in the extra delta V and still have a useful payload.

I invited you to try a modlet of mine (SABR3 Sterling) which happens to address this exact problem. It's in limbo now since it's not a mod I'd use for myself much (I largely made it for someone else to enjoy, and I have OPT) but I've managed SSTOs that could take 30, maybe 45 tons to LKO in 2.5x.

Staying on topic, I personally love SSTO planes (not all SSTO are planes) whether or not they're worth it because I love the idea of using the atmosphere to help/feed the engines, and getting into speed ranges that can't be done with stock parts and/or at stock scale, and being able to control and use lift to aid and control the ascent and descent.

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9 hours ago, JadeOfMaar said:

Staying on topic, I personally love SSTO planes (not all SSTO are planes) whether or not they're worth it because I love the idea of using the atmosphere to help/feed the engines, and getting into speed ranges that can't be done with stock parts and/or at stock scale, and being able to control and use lift to aid and control the ascent and descent.

This is a little tangential to that, and it's been a while since I tried it so things might be different now, but I have found that a cluster of Whiplash engines surrounding a rocket engine actually makes for a decent launch booster.  The Whiplashes alone won't lift a heavy payload to exo-atmospheric velocities, but they add thrust to the existing rocket engine, and as the rocket continues to accelerate more air gets forced into the Whiplashes' intakes, allowing them to keep adding thrust as long as they are still in-atmo.  

That is probably too expensive for a discarding launch vehicle, but can be useful for a reusable lifter, especially since the Whiplashes give the thing some atmospheric cruising range on return from orbit, making it easier to get back to KSC (or wherever you are recovering from.)

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SSTO spaceplanes are not money-savers.

They are money-savers per Kerbin hour, but with the time compression at hand's reach that means very little. They are definitely not money-savers per player's hour.

Say, your average contract done the 'disposable' way will take, say, an hour to complete, and yield 70% of the offered profit. It will also take about 5 Kerbin hours.

The same contract done SSTO way will yield 98% profit (providing you don't crash), take maybe 6 Kerbin hours (return flight home!), but in real time it will take 2-4 hours of your attention. You could do 2-4 contracts "the disposable way" in that time.

That being said, SSTO launchers - rockets - are a money-saver. Launch goes the same, landing them takes maybe 5 minutes, and you get ~90% ROI (you won't land them at KSC, but you'll get >70% recovery value).

Make no mistake, FMRS and similar stage-recovery techniques are not money savers for the same reason SSTO spaceplanes aren't. In the time it takes you to safely land and recover all the boosters you could've flown half of another contract.

 

BUT SSTO spaceplanes are fun and challenging! Do you need more reason than that to build them?

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1 hour ago, Sharpy said:

They are money-savers per Kerbin hour, but with the time compression at hand's reach that means very little. They are definitely not money-savers per player's hour.

This argument never made a lick of sense to me. Isn't the whole point of playing KSP to spend time in an enjoyable, creative, and occasionally educational manner?

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2 hours ago, Brikoleur said:

This argument never made a lick of sense to me. Isn't the whole point of playing KSP to spend time in an enjoyable, creative, and occasionally educational manner?

Yes. See my last paragraph.

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18 hours ago, JadeOfMaar said:

Staying on topic, I personally love SSTO planes (not all SSTO are planes) whether or not they're worth it because I love the idea of using the atmosphere to help/feed the engines, and getting into speed ranges that can't be done with stock parts and/or at stock scale, and being able to control and use lift to aid and control the ascent and descent.

This is to me one of the better 'mini-games' (if you could call it that) in KSP and I wish there were more like it - fine tuned, physics-based challenges based on the real world but abstracted down to something players can engage with intuitively in real-time.
 

9 hours ago, Fearless Son said:

That is probably too expensive for a discarding launch vehicle, but can be useful for a reusable lifter, especially since the Whiplashes give the thing some atmospheric cruising range on return from orbit, making it easier to get back to KSC (or wherever you are recovering from.)

*Runs off to the VAB

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12 hours ago, Sharpy said:

SSTO spaceplanes are not money-savers.

They are money-savers per Kerbin hour, but with the time compression at hand's reach that means very little. They are definitely not money-savers per player's hour.

Say, your average contract done the 'disposable' way will take, say, an hour to complete, and yield 70% of the offered profit. It will also take about 5 Kerbin hours.

The same contract done SSTO way will yield 98% profit (providing you don't crash), take maybe 6 Kerbin hours (return flight home!), but in real time it will take 2-4 hours of your attention. You could do 2-4 contracts "the disposable way" in that time.

That being said, SSTO launchers - rockets - are a money-saver. Launch goes the same, landing them takes maybe 5 minutes, and you get ~90% ROI (you won't land them at KSC, but you'll get >70% recovery value).

Make no mistake, FMRS and similar stage-recovery techniques are not money savers for the same reason SSTO spaceplanes aren't. In the time it takes you to safely land and recover all the boosters you could've flown half of another contract.

 

BUT SSTO spaceplanes are fun and challenging! Do you need more reason than that to build them?

11 hours ago, Brikoleur said:

This argument never made a lick of sense to me. Isn't the whole point of playing KSP to spend time in an enjoyable, creative, and occasionally educational manner?

Well, he is being educational. He broke down SSTO rockets vs. spaceplanes. I was never asking for a cut an dry answer. More like trying to look for all the sides to them. What I feel personally is that I most likely won't use them in career mode because they don't seem to fit, to be honest, but in science mode and/or sandbox I will use them because the objectives are different.

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My first career game sent everything from launch->destination so when I actually got to the point where I could build a functional Plane to Orbit (I still drop fuel tanks, because they're cheap, so technically not SSTO) there was nothing there for them to do. So I started a hard career game that has a large transfer station in Equatorial orbit so that there is a reason to send a plane to space. Planes turn out to be the safest way to land Kerbals back on Kerbin anyways, (parachuting out of drop pods causes some folks to blink out of existence or tumble down mountains).

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On 11/16/2018 at 3:03 PM, Sharpy said:

SSTO spaceplanes are not money-savers.

They are money-savers per Kerbin hour, but with the time compression at hand's reach that means very little. They are definitely not money-savers per player's hour.

Say, your average contract done the 'disposable' way will take, say, an hour to complete, and yield 70% of the offered profit. It will also take about 5 Kerbin hours.

The same contract done SSTO way will yield 98% profit (providing you don't crash), take maybe 6 Kerbin hours (return flight home!), but in real time it will take 2-4 hours of your attention. You could do 2-4 contracts "the disposable way" in that time.

That being said, SSTO launchers - rockets - are a money-saver. Launch goes the same, landing them takes maybe 5 minutes, and you get ~90% ROI (you won't land them at KSC, but you'll get >70% recovery value).

Make no mistake, FMRS and similar stage-recovery techniques are not money savers for the same reason SSTO spaceplanes aren't. In the time it takes you to safely land and recover all the boosters you could've flown half of another contract.

 

BUT SSTO spaceplanes are fun and challenging! Do you need more reason than that to build them?

That depends on how your career game is set up. If you set monetary reward to 20%, then the cost saving of a spaceplane is significant, and IME the time to return an SSTO rocket is similar to a spaceplane (both are slow to decelerate in the upper atmosphere).

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On 11/16/2018 at 8:03 AM, Sharpy said:

Say, your average contract done the 'disposable' way will take, say, an hour to complete, and yield 70% of the offered profit. It will also take about 5 Kerbin hours.

The same contract done SSTO way will yield 98% profit (providing you don't crash), take maybe 6 Kerbin hours (return flight home!), but in real time it will take 2-4 hours of your attention. You could do 2-4 contracts "the disposable way" in that time.

I agree with your main point, but these time estimates seem way off in my experience.

How does it take a whole hour RT to complete an average rocket contract, or 2-4 hours RT for a spaceplane? I finish designing and building a rocket/spaceplane in those times, and that includes multiple trials to test flight stability and establish optimal ascent and descent profiles. If every trial run took that long, I'd never get to finish my builds, let alone play the actual career.

If you're taking more than 10 mins RT to get your average rocket payload to circularized orbit with a run of the mill gravity turn, something's wrong. That's even considering untypically shallow ascents (30 degrees above horizon at 10km); if you always go the more typical 45@10km, 5-6 mins tops.

Spaceplane ascents are generally (but not necessarily!) shallower and so typically take longer, but even with those I never take more than about 30 mins RT at most for the entire mission, including payload deployment and runway landing.

 

On 11/10/2018 at 12:04 AM, Pthigrivi said:

No need to spend hours landing, I just get close and pop the chutes.

This comparison seems a bit off. The atmospheric trajectory and time spent before you pop the chutes is not going to be any different than for a typical spaceplane - so that can't be causing 'hours' of difference. And I can't imagine any reasonable landing approach taking much longer than what it takes to float down on chutes. If you remove the restriction of landing at the runway, I think landing the plane in the flat KSC vicinity could even be faster.

I concede that landing the 'plane way' requires one to actually pilot the craft down, where chutes make it care-free and practically automated... but I can't see it making any significant difference in time.

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23 minutes ago, swjr-swis said:

This comparison seems a bit off. The atmospheric trajectory and time spent before you pop the chutes is not going to be any different than for a typical spaceplane - so that can't be causing 'hours' of difference. And I can't imagine any reasonable landing approach taking much longer than what it takes to float down on chutes. If you remove the restriction of landing at the runway, I think landing the plane in the flat KSC vicinity could even be faster.

I concede that landing the 'plane way' requires one to actually pilot the craft down, where chutes make it care-free and practically automated... but I can't see it making any significant difference in time.

True, the only real advantage is because Im not trying to precisely land on the runway most of the journey down can be done on physics warp, aside from a dicey stretch around max-q. Probably a well-designed spaceplane could time-warp close enough to only pilot the final approach too though? The other half is just how much faster it is to launch an SSTO rocket over an airbreather. 

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