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Thrawn889

SSTO's and Space Planes

Question

So, I've had my career going for about a week now and i have unlocked most of the tech up to the 500 limit that a level 2 research. This has unlocked a bunch of plane parts that i have noticed on a lot of the designs people come up with, But i will be honest i suck at building planes and my rockets are all asparagus launched and the average cost to me is 130k. The module im returning with is only worth 6k, I losing alot in my launch staging. Anyone know how i can help with that will SSTO or space planes help that much with recoverable costs? 

I'm trying to save up for the Research level upgrade but its slow going when any contracts i take up i need 130k to get me in the air. 

If you have a guide on building SSTO or maybe even how to save my twin boar asparagus rockets would be good cause that where alot of my money goes. I have 4 Twin boars at 17k a unit. Then a main sail and Rockomax 64 tanks which gets me mostly circular before i have to use a Rockomax X200-16 Fuel Tank or Rockomax X200-8 Fuel Tank depending on my mission (mun or Minmus) this teams to a Skipper or poodle engine (Again whatever i think is more efficient for the mission). (i will post a pic when i get home). 

This may be overkill really but i tend to use up alot of DV especially when i go to the Mun. (its the landing stage that i struggle with. Although MechJeb has helped ( i don't crash as often). 

 

SO yeah y'all Kerbonauts, Any helpful tips or tricks?

 

 

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Thrawn889,

 Honestly... Your rockets shouldn't be costing you anywhere near that much. I recommend checking out this excellent tutorial by @Norcalplanner:

 

Building a good airplane is more difficult and demanding than building a good rocket, and even more so for a cheap SSTO space plane. Whatever overengineering you've got going on now will be much worse in a space plane.

 I recommend that you focus on how to build cheap and efficient rockets first.

Good luck,
-Slashy

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You can SSTO a rocket pretty easily in KSP, you just need to overbuild it. I would generally advise a circulisation stage though, because handling the massive TWR of late-flight SSTOs can be a bit of a pain. Plus, the costs go up because you've got other considerations like enough batteries and reaction wheels to make the thing maneuverable. And then slap on enough parachutes to land it gently. At the 550-level of science you've got a plethora of parts that can help with this, including structural parts with high impact tolerances. This sort of thing takes a lot of testing so try it out in sandbox if you have reverts disabled.

With a Twin-Boar you can put a couple of girders on the side to handle the landing gear, that'll give you clearance and widen the landing base. Remember the editing tools, that'll help you with positioning and making it look good (always a plus, in my book). Alternatively you can just shoot for a water landing. Put a probe core on it and make sure the bottom is heavier than the top, maybe add a small tank with the fuel disabled so you have de-orbit and maneuvering capability. Airbrakes would probably help too, try enabling the actuation toggles on them. Use linear RCS blocks and a reaction wheel to help steer it in the upper atmosphere.

Get creative, try things out, find something that works for you.

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43 minutes ago, Thrawn889 said:

Thanks for the advice. I was basically working a theory of Moar Power over skill as i haven't really got the skill. I watched a few YT vids by people who were talking about Asparagus launching and making it most efficient. which i suppose i took too far to heart XD.

Be sure you're watching up to date videos. KSP went through a major change in aerodynamics about 18 months ago and anything older than that is utterly wrong now and should be discarded. Ideally make sure the video is for version 1.2, although 1.1 wasn't a million miles away.

Asparagus staging is still useful, but it's a relatively small gain vs flying the correct launch profiles. While we joke about MOAR BOOSTERS, the truth is that's usually not the right answer to a problem. Spaceflight is more about subtlety, efficiency, and minimalism than brute force :) 

 

Edited by eddiew

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If you're having trouble with building normal planes, spaceplanes will be MUCH more difficult.  They're a lot of fun once you do figure them out, but you have to worry about all the normal plane stuff plus a number of additional issues like fuel balancing, making sure it can handle reentry, and still having all the components it needs to function and maneuver in space.

And at the stage of the game you're currently at, you shouldn't need anywhere CLOSE to that big of a rocket.  You could probably easily make a Mun lander for a quarter of that cost.  Maybe if you're going for a full Apollo-style mission, it'd get close to that much, but there are much more efficient ways to get there if money is that much of an issue.

Edit:  In about 5 minutes, I threw together a craft capable of landing a single Kerbal on the Mun and returning.  Even with a rather inefficient ascent profile, landing, and...well actually none of the maneuvers were particularly efficient...it still had over 1k dV left when it returned.  Total cost:  34502.  Science instruments are very expensive, so if you put all of those on as well, it might be another 20k or so, though you could probably recover at least some of them.

With a few more adjustments, I could easily cut the cost of that in half again.  Even if you object to sending a Kerbal out to the Mun by himself and want to have a crew of 3, it can be done for under 60k(even using the Mk1-2 pod). 

Edited by Hodari

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Tbh, sounds like you're launching things that are way bigger than they need to be... what you're describing sounds like it could to to Duna or Dres and back.

Pics will help, but my hunch is you're overspeccing. You can send tiny things to Minmus and still get them home :) 

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3 hours ago, Thrawn889 said:

Anyone know how i can help with that will SSTO or space planes help that much with recoverable costs? 

Spaceplanes aren't a money-saver, in general.  Moving to a spaceplane-based career won't really solve your issues.  There's nothing wrong with flying spaceplanes, and lots of KSP players have lots of fun flying them, but really, the only reason to fly spaceplanes is because you like doing it.

In general, KSP careers are very lucrative.  Launching spacecraft (any kind) is relatively cheap, and contracts pay a lot.  One contract can pay for a dozen launches.  So unless you have the career difficulty settings cranked way up, you ought to have cash coming out of your ears, i.e. easily enough to play the game however you want without worrying about exactly what kind of rocket you're launching.

If you're financially strapped for launch costs, by far the most likely reason is that you're designing your ships wrong (where by "wrong" I mean "a lot more expensive than they need to be").  Your path to solvency is more likely to be "refine your rocket-building technique" than "switch to spaceplanes".  The best way to do that is to just post some questions in the Gameplay Questions forum, like this:  "Hi, I'm trying to put <payload> into Kerbin orbit, but my rocket is super big and expensive:  <screenshot>.  Is there a cheaper, more efficient way to do this?"  I'm sure you'll get lots of helpful suggestions.  :wink:

Lots of words in spoiler section, regarding the above assertion that spaceplanes aren't particularly a money-saver (at least not to a degree that necessarily makes a big career difference), in case you're interested.

Spoiler

Regarding the above assertion that spaceplanes aren't a money saver:  More discussion here and here, but it boils down to this:

  • Avoiding disposable rockets doesn't really save you much. Multi-stage rockets are very cheap to launch... if you build them right.  If you're spending :funds:130K or more for a rocket... that's a lot.  You should be able to send a crewed Mun return mission for a small fraction of that, for example.  You didn't mention what kind of a craft you were spending that 130K on, but unless it was a crewed Moho return mission or something, you're spending way too much.
  • Recovering hardware doesn't gain you much.  KSP contracts are quite lucrative.  I can build a rocket for 20K funds that can satisfy a 200K contract.  Given that I make 180K profit even if I recover zero hardware, in financial terms it's really not worth the bother of trying to recover anything, even if I could recover 80% of the cost of the craft.  Better to save the time and run an extra contract instead.
  • Recoverable SSTOs take more of your personal time than simple non-recoverable multi-stage rockets.  The real currency in this game is your personal time.  Flying an SSTO to orbit is, in general, more time-consuming than a multi-stage vertical launch.  Recovering an SSTO-- especially if you're taking the time to recover it close to KSC to maximize recovery value-- is certainly more time consuming than just throwing the rocket away when you're done with it.  :wink:  So if you're primarily financially motivated, that's not a good use of your time.  If you can save ten minutes by launching a rocket and throwing it away... a better use of those ten minutes would be to take the time saved and do another contract, thereby earning far more money than you would have by recovering hardware.

Note that none of the above is telling you "don't fly spaceplanes".  There are plenty of reasons for flying spaceplanes-- or, indeed, any other kind of play-style choice-- that have nothing to do with raw financial payout.  Lots of good reasons:  maybe just "because they're fun".  Maybe for role-playing reasons (such as self-imposed "house rules" to make things more interesting or challenging).  And so forth.

But honestly, KSP careers are generally so cash-rich that you should have plenty of funds to play the game however you like, unless you either have the difficulty settings cranked way up, or else may be unnecessarily wasting funds with inefficient rocket design.

 

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If you want cheap rockets, use solid fuel boosters for the first stage.

I do not have great launch profiles(usually pretty much straight up until 35km), but generally anything in LKO works with a kick-back first stage and a terrier powered orbit/manuver/deorbit stage. (a long 1.25m tank with a terrier, a few instruments, and a parachute or three tends to have all the d-v I need, especially for satellites which do not need parachutes, crew cabins, or deorbit burns)

When I have a larger rocket, I will often go with 2.5 stages, Kickbacks around the sides, a LF engine in the middle that also ignites at launch(usually main-sail with any excess thrust being used for more fuel), and an upper stage that can get wherever I need to go in the Kerbin SOI(often with a push from the LF core of the launch stage).  If I am still low on d-v, I may attach tanks to the tops of the kick-backs so that my LF core is near full when they disengage after ~62 seconds.

I have used a twin boar liquid core on occasion, but not very often.  I think the last time I used twin boar boosters was when I was delivering a pre-assembled self-sufficient MKS base somewhere.

Generally my ships have ISRU and will be launched with just enough fuel to land Minmus on nuclear engines where their fuel and ore tanks will be topped off before they head to their destinations.  (My vacuum landings are also pretty inefficient: I try to come to a relative stop over my intended landing place from low orbit(< 10km) and use the KER suicide burn distance to slow down when I get close(drop speed to 20m/s at 200m remaining then <5m/s at 50m remaining and eye-ball it from there, on heavy bodies I may slow down at 1Km or 500m remaining to make sure I do not accidentally over-shoot the 200m mark))

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...Oh, and, moving this to Gameplay Questions, since it's primarily a question about how to play the game.

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a quick search at kerbalx resulted in those examples of much lighter and cheaper crafts able to do missions in kerbin SOI:

https://kerbalx.com/MadaRook/PT-Series-Munsplorer-V1

https://kerbalx.com/KSPBrasil/Emperion---Turismo-Orbital-3k

https://kerbalx.com/KSPBrasil/SSR-v11---Satellite-Signal-Relay

https://kerbalx.com/CompoundKhan/Orbiter-Mk-II

https://kerbalx.com/MRMac/MK1-Mun-Pod

https://kerbalx.com/madmerlyn/Lunar-ComSats

Try building something along that lines and tell us what difficulties you fund.

 

 

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Hey Guys, 

I got home and fell asleep last night. XD 

 

My basic builds are along the lines of 9XAeeKt.jpg

this has a basic asparagus system but if i remember right i got Jeb stuck on the mun with this design. Which was frustrating. 

I know that I can cheaply build Mk.1 pod ships cheaply i like using the mk1-2 pod cause i can have a pilot and scientist. My next level design moved to S4Ja3Vy.jpg

As you can see i used the basics with Jumbo 64 tanks and mainsails this design gets the job done. But as you can see the cost is quite high. 

I used it to launch a relay into kerbal orbit and it was overly efficient for that purpose. 

4PE7vFf.jpg4PE7vFf.jpg

My Payload laucher sub assembly then morphed into MKhGfBG.jpg

this was because i thought the Twin Boar were a better idea than the mainsail design. But once i get this up to circularised this basically drops almost100k of the value in the asparagus stages. 

SO yeah i know there are some good stock parts but i play on the basic medium game which doesn't provide those stock designs. Im thinking after doing a couple more money making schemes that i really should go to Duna for a fly by which is one of my missions my only issue is i want the 500+ science parts before i try it and im struggling to make the money cause each launch is overly expensive. 

 

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Yeah, um, you're way way way overspeccing :)  Getting to LKO needs about 3200-3400 vacuum delta-v, you're packing between 5400 and 8500 - that relay could probably go to Jool. It should be launchable with a single 1.25m stack under it, maybe give it an SRB at the bottom and a terrier at the top as @Terwin says above :) 

If you're finding that you're burning a lot of fuel on the ascent, it's likely that your launch profile is suboptimal - and I think a reason you might struggle is you have no fins. You've got nothing for aerodynamics to take hold of in order to keep your rockets on course so you're having to do everything with gimbal. Bearing in mind that darts and arrows fly relatively straight and follow their noses, you want your rockets to have a similar design. Have some fins on the very back (some with steering) and lean ~5-10 degrees over at 50-100m/s. From 150m/s you should be able to turn off SAS, or set SAS to hold prograde, and those rockets will mostly fly themselves up. Some good passing points to look out for are a 45 degree lean by 10km, and a 30 degree lean by 20km. After 50, point horizontal.

Also keep an eye on your throttle during ascent. With fins on the back and the weight at the front, throttle control becomes steering. The faster you're going, the more air bounces off your fins per second, the straighter it will try to fly - but you don't want it to fly dead straight. You want a gentle, gradual, (gravity) turn that results in being near horizontal at high altitude without you having to pull it around. Every time you're manually adjusting course, you're increasing drag and losing delta-v to the air. Keeping your TWR between 1.6 and 2.0 will help the rocket to fall over naturally and minimise this :) 

Checking the wiki's delta-v map...

KerbinDeltaVMap.png

We can add up that you'll need around 3400+860+310+580 = 5150m/s to land on Mun. Getting back you need whatever's on the surface to have 580+310 = 890m/s bare minimum. Sum total with absolutely dry tanks and flawless execution will be around 6040m/s. Personally I like to carry 7200 because I like a 20% safety margin.

With regards to your station, I recommend wrapping a fairing around it as you do the relay. It's got blunt front and a lot of sticky outy bits that will be adding a lot of drag. If you take out the twin boars, you've got around 2800m/s already. I think if you swap them for some big SRBs you'll easily find the missing 600 :) 

Edited by eddiew

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Thrawn889,

 Aside from the excessive DV for the job, I see way too much thrust, a lack of engine type optimization, and a lack of attention to streamlining. Also, asparagus staging isn't beneficial if not done correctly. A lot of what you're attempting could be done more simply and cheaply with a single stack.

 Generally speaking, you'll have better luck if your designs look more like real world ones. After all... real rockets look the way they do for a reason.

Best,
-Slashy

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@eddiew

Thanks for the advice. I was basically working a theory of Moar Power over skill as i haven't really got the skill. I watched a few YT vids by people who were talking about Asparagus launching and making it most efficient. which i suppose i took too far to heart XD.

 

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My recommendation for you is to open up the Atmo readouts for KER.  This gives you a lot of useful information about optimizing your rockets.

The most efficient rockets I have come up with are Solid Rocket stage, Atmospheric rated Liquid fuel stage, then Vacuum rated liquid fuel stage, with the SRM and 1st liquid fuel stage firing at launch.

The different stages should be sized as such.

The 1st liquid fuel stage should have enough fuel, when combined with SRM stage for about 3000 m/s delta V in vacuum, with a rocket sized to provide 1.3-1.4 TWR at 5km altitude after the SRM have burned out.  this frequently involves turning down the thrust on the rocket tweakables.

the SRM stage should be sized to get launch TWR at 1.4-1.5 at the surface.  This involves tweaking both the main liquid fuel engine and the SRM engine thrust, and where possible having the liquid fuel stage set as low as possible to get the 1.5 TWR at surface, and the 1.3 TWR at 5km once the SRM have burned out.

The final stage should be sized for an approximate 0.3-0.5 TWR, with sufficient delta-V to get to your ultimate destination plus the around 400 m/s needed to pay the 3400 m/s delta V bill needed to get to orbit.  The more of the 3400 m/s to orbit you put on the launch stage, the more towards 0.5 your vacuum TWR needs to be at stage initiation.

With this design, I can get 7 kerbals (payload around 8t with cabins and needed re-entry gear) to orbit for 30k (without recovery), using a gravity turn, and throttling my engine to keep time to apoapsis around 50 seconds until desired Ap altitude is reached.  my cargo launches are similarly efficient.   

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4 hours ago, eddiew said:

While we joke about MOAR BOOSTERS, the truth is that's usually not the right answer to a problem. Spaceflight is more about subtlety, efficiency, and minimalism than brute force

^ This, about a million times. And most of the time, flying an overpowered rocket is more difficult than one with nominal thrust, not less. You only really need 1.4 off the pad (1.2 if using SRBs), 0.7 for transstage to orbit, and 0.5 for any transfer. Landers work fine with 2g in the local reference, which is tiny compared to Kerbin.

Best,
-Slashy

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7 hours ago, eddiew said:

Also keep an eye on your throttle during ascent. With fins on the back and the weight at the front, throttle control becomes steering. The faster you're going, the more air bounces off your fins per second, the straighter it will try to fly - but you don't want it to fly dead straight. You want a gentle, gradual, (gravity) turn that results in being near horizontal at high altitude without you having to pull it around. Every time you're manually adjusting course, you're increasing drag and losing delta-v to the air. Keeping your TWR between 1.6 and 2.0 will help the rocket to fall over naturally and minimise this :) 

I tend to take a different approach - start with a TWR of 1.25 to 1.5, but leave it full throttle for the duration of the burn.  Per the thread below, it sounds like you generally save the most delta-v by going as fast as you can, so you spend less time losing speed to Kerbin's gravity.  

It's true that if you go faster, your rocket will not tend to turn as much.  I solve this by doing an earlier/steeper pitchover.  For rockets that start with a 1.5 TWR, and don't stage off thrust early in the ascent, I try to hit a 45 degree angle at about 5,000 meters (compared to more like 10,000 meters with an initial TWR around 1.25).

I would also say that most well-designed rockets can do OK without fins, especially if you're using vectored thrust to keep things tidy.  Especially with a higher starting TWR, since you want the rocket to turn a bit more easily, fins can even be counterproductive.  

 

 

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8 hours ago, eddiew said:

Yeah, um, you're way way way overspeccing :)  Getting to LKO needs about 3200-3400 vacuum delta-v, you're packing between 5400 and 8500 - that relay could probably go to Jool. It should be launchable with a single 1.25m stack under it, maybe give it an SRB at the bottom and a terrier at the top as @Terwin says above :) 

 

I was thinking those numbers were atmospheric since you are starting in the atmosphere in the first place......:confused:

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1 hour ago, Aegolius13 said:

Per the thread below, it sounds like you generally save the most delta-v by going as fast as you can, so you spend less time losing speed to Kerbin's gravity.  

Well... Yes and no. More acceleration does save DV, but those savings can be misleading. DV savings don't automatically translate to fuel, mass, or cost savings. It usually works out lighter and cheaper to go with the numbers I posted above, even though the DV budget winds up being a little more.

My first stage is always 1.2-1.4g off the pad and 1,800 m/sec DV calculated at 1/2 atmosphere. My second stage is always 0.7g initially and 1,700 m/sec DV calculated at vacuum. These numbers work out right for everything I launch with a reasonable safety margin.

Best,
-Slashy

 

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You do need to make sure you have a good ascent path - when I started in 1.0 I watched 0.90 tutorials, and I used the turn right at 10 km path, which didn't go very well for my kerbals, rockets and funds. Make sure you start your gravity turn early, and use a very shallow trajectory.

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9 hours ago, GoSlash27 said:

Well... Yes and no. More acceleration does save DV, but those savings can be misleading. DV savings don't automatically translate to fuel, mass, or cost savings. It usually works out lighter and cheaper to go with the numbers I posted above, even though the DV budget winds up being a little more.

My first stage is always 1.2-1.4g off the pad and 1,800 m/sec DV calculated at 1/2 atmosphere. My second stage is always 0.7g initially and 1,700 m/sec DV calculated at vacuum. These numbers work out right for everything I launch with a reasonable safety margin.

Best,
-Slashy

 

That's true, but I wasn't really talking about what engine to use, or other build issues.  I was just talking about not throttling down as your TWR increases over the course of a stage, to make the most out of whatever engine you decided to use.  

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38 minutes ago, Aegolius13 said:

That's true, but I wasn't really talking about what engine to use, or other build issues.  I was just talking about not throttling down as your TWR increases over the course of a stage, to make the most out of whatever engine you decided to use.  

Aegolius13,

 That is all true, and I can't really come up with any argument for not doing that. But in all honesty... I actually *do* throttle back during my ascent so that my thrust to weight is 2sin(pitch). I'm sure it's not doing me any favors in the efficiency department, but my gravity turns work out identical that way. I'm sure that running full throttle is more efficient overall, but IME throttling back tends to be easier. Laziness is the mother of invention, and I am nothing if not lazy :D

Best,
-Slashy

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In terms of operating economics,  KSP is not like real life.    IRL,  the space shuttle dumps the external fuel tank but brings home the engines.

However, in KSP, the lower tier engines are surprisingly cheap.  Oxidizer costs almost nothing,  and liquid fuel isn't that costly.   But Oxidizer tanks must be lined with platinum or something, because empty rocket fuel tanks have a surprising amount of value :

FT400 tank - 316 Funds value when empty

Mass (when empty) 0.25 ton

 

Reliant engine - 1100 Funds value

Mass - 1.25 tons

 

Full SSTO is difficult and requires a very large rocket for a very small payload.    If you're going for partial re-use,  you should dump the lower stage engine but carry its fuel tanks to orbit and back.    For the same mass penalty you'd get for retaining one reliant engine, you could recover five fuel tanks with a total value of 1580 Funds.    

I've done this before by putting my fuel tanks beneath the capsule, then a terrier engine at the bottom of the fuel tanks, then a decoupler , then the reliant (just make sure the decoupler has crossfeed enabled or the launch countdown will be disappoint).   At about 15km the Terrier ISP rating starts to exceed the Reliant's, though you might wait until your TWR is going over 3:1 to stage.

That said, a good old solid booster first stage with Terrier upper probably beats all.

 

In the world of partially re-usable spaceplanes,  i came up with a good design when attempting the shuttle challenge, though it's probably too SSTO-like to be eligible

.

Two Whiplashes, two Terriers, and two NERVs.

The Whiplashes get us to about mach 4, then i start the Terriers up.   The Whiplashes get staged away when they flame out (2250 Funds value each and 1.8 ton dry mass, my conscience has an easy time with this one). The oxidizer runs out at about mach 5.3 , so i stage to get rid of the Terriers (0.5 ton and 450 funds value). The NERVs are able to do the rest at this point, since orbital freefall effect is supporting most of our weight which lessens the amount of lift we need - which means we can be at very high altitude ,where there isn't much drag.

5400 funds to bring a shuttle lookalike with 6ton space telescope aboard to a 650km, 20 degree inclined orbit - not bad.   

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